Assistant Professor of Medicine and Epidemiology &Population Health, Department of Medicine,
Epidemiology & Population Health, Albert Einstein
College of Medicine
Attending Physician, Department
of Medicine, Montefiore Medical Center, Bronx, NY
The Pathophysiology of Uremia
Short courses of aminoglycoside-containing drops can be used safely in such patients erectile dysfunction doctors staten island generic viagra super active 50mg otc. The decision as to whether to operate to close the perforation in the long term will depend on the severity of symptoms impotence solutions generic 25 mg viagra super active visa. If allowed to continue top erectile dysfunction doctor 50 mg viagra super active, the disease will increase in size and may damage the ossicles erectile dysfunction treatment vitamins discount viagra super active 100 mg online, the cochlea and the vestibule and can lead to intracranial sepsis impotence doctor generic viagra super active 100 mg amex. These include meningitis erectile dysfunction after age 50 100mg viagra super active free shipping, subdural abscess erectile dysfunction effects on relationship buy viagra super active 25 mg without a prescription, extradural abscess erectile dysfunction vasectomy buy viagra super active 25mg with amex, intracerebral abscess and venous sinus thrombosis. During its course within the temporal bone, it can be divided into labyrinthine, tympanic and mastoid parts. The site most commonly affected is the footplate of the stapes, where it articulates with the oval window. The excess bone interferes with the rocking movement of the stapes, resulting in a conductive hearing loss. The infection also affects fibres from the facial nerve which supply the ear canal. When vesicles form and break down, a painful otitis externa develops which often requires topical treatment and aural toilet. In laryngeal cancer, involvement of the vagus nerve (cranial nerve X) may lead to otalgia. Applied anatomy of the ear 45 Pharynx, larynx and neck Multiple choice questions In the following, choose the single best answer. B A system for describing lymph nodes of the neck Clinical anatomy and physiology 1. A Fourth cervical vertebra B Fifth cervical vertebra C Sixth cervical vertebra D Seventh cervical vertebra E First thoracic vertebra. Infection of the parapharyngeal space places the patient at risk of: A Otitis media B Acute tonsillitis C Dental infection D Mediastinitis E Epiglottitis. A Eighth cranial nerve B Ninth cranial nerve C Tenth cranial nerve D Eleventh cranial nerve E Twelfth cranial nerve. A Preparation of fold bolus for swallowing B Protection of the lower respiratory tract C Phonation D Control of pressure during respiration E Fixation of the chest. A A system for describing skin lesions involving the neck C A system for describing the salivary glands D A system for describing movement of the larynx during swallowing E A system for describing venous drainage of the neck. A Hyponasal speech B Velopharyngeal insufficiency C Recurrent epistaxis D Cleft palate E Obstructive sleep apnoea. In which patients presenting with unilateral nasal obstruction and recurrent epistaxis should angiofibroma be suspected A Elderly male smokers B Adolescent patients of Chinese origin C Middle-aged patients with atopy and asthma D Adolescent males E Immunocompromised patients. Treatment of a peritonsillar abscess requires: A Tonsillectomy B Transoral incision and drainage 330 10. A Under local anaesthetic in the sitting position B Under local anaesthetic with the patient supine C Under general anaesthetic with the patient head down D With antibiotics alone E As an outpatient. A At the point the superior laryngeal nerve penetrates the thyrohyoid membrane B At the potential space between the superior constrictor and skull base C At the weakness where the pharyngeal constrictors meet the midline raphe D Created following tonsillectomy E Between the lower border of the inferior constrictor and cricopharyngeus muscles. In paediatric suspected acute epiglottitis, which of the following is contraindicated A Antibiotics B Examination of the mouth with headlight and spatula C Examination under general anaesthetic D Emergency intubation E Tracheostomy. A Acute upper airway obstruction B Potential upper airway obstruction C Tension pneumothorax D Protection of the lower airway E Prolonged artificial ventilation. A A decrease in alveolar ventilation B An increase in the work of breathing C Increased rate of moisture exchange from the upper airway D Reduced mucus production E Reduction of anatomical dead space. A A low-pressure cuff B An inner tube C An outer flange D A port for nasogastric feeding E A speaking valve attachment. C It is a long-term solution to airway obstruction D It involves excision of the anterior cricoid cartilage E It should routinely be converted to a tracheostomy. A Speech therapy B Surgical excision C Radiotherapy D Steroid injection E Inhaled corticosteroid. Early laryngeal cancer presents with: A Otalgia B Lymph node metastasis C Hoarseness D Dysphagia E Weight loss. A the thyrocervical trunk B the cervical sinus C the track of the thymus through the neck in to the mediastinum D the fourth branchial pouch E the track of the thyroid from the tongue base to the neck. A the anatomy of the larynx allows for significant swelling prior to loss of function. B Endotracheal intubation should be performed prior to the formation of oedema and maintained until swelling subsides. A Submandibular swelling with inflammatory oedema of the floor of mouth B Spreading cellulitis of the lower neck with dark discoloration in patches related to necrosis C Gingivostomatitis D Retrosternal chest pain related to swallowing E Cellulitis secondary to zoster lesions in the cervical dermatomes. C Infection of the cyst leads to an increase in size, facilitating surgical excision. D They are found at the junction of the upper and middle third of the sternomastoid muscle. A procedure which removes all lymph nodes on one side of the neck but preserves the accessory nerve, jugular vein and sternomastoid muscle is called: A A radical neck dissection B A classical neck dissection C A selective neck dissection D A subtotal neck dissection E A modified radical neck dissection. A Bacterial cervical lymphadenitis B Infection of a necrotic malignant cervical lymph node C Tuberculous cervical lymphadenitis D Tracking of a peritonsillar abscess into the parapharyngeal space E A postoperative wound infection which drains through the collar incision of thyroidectomy. Investigation and management of the acute airway case A Ultrasound-guided aspiration B Per-oral incision and drainage C Early tracheostomy D Intubation until swelling subsides E Cricothyroidotomy F Insertion of an oral airway G Transfer to theatre with experienced anaesthetist and surgeon H Endoscopic excision of lesions I A short course of steroids J Soft tissue neck X-ray Choose the most appropriate management for each of the scenarios listed below: 1 A stertorous 16-year-old with tonsillitis and a positive test for glandular fever fails to improve with antibiotics, fluids and analgesia. C the pharynx is a muscular tube which extends from skull base to the level of the sixth cervical vertebra, which corresponds to the lower level of the cricoids cartilage. D the deep spaces of the neck lie between fascial planes which allow for the spread of infection in predictable patterns. Pus can track through these potential spaces to the para-oesophageal region and the superior mediastinum. The most common sources of suppuration in the parapharyngeal lymph nodes are dental and tonsil infections. C the sensory and motor innervation of the larynx is derived from branches of the vagus nerve. The superior laryngeal nerve supplies sensation to the larynx above the true vocal folds, and motor supply to the cricothyroid muscle. The recurrent laryngeal nerve supplies sensation to the larynx below the vocal folds and all other intrinsic laryngeal muscles. Damage to the recurrent laryngeal nerve during thyroidectomy will produce a cord paralysis and resulting hoarseness. It acts as a sphincter which closes during swallowing at the laryngeal inlet, the false cords and the glottis. It also helps in the cessation of respiration during the swallow and is involved in the cough reflex. The human larynx is well developed for phonation, but also helps control pressure during the respiratory cycle, with vocal cord abduction during inspiration. Closure against raised subglottic pressure splints the chest and aids in lifting, climbing and defaecation. Squamous cell carcinoma of the upper aerodigestive tract metastasises to predictable areas of the neck. As our understanding of patterns of metastasis have evolved, procedures have been developed which spare these structures, particularly the accessory nerve. E Adenoidectomy for obstructive sleep apnoea in children with postnasal obstruction is often combined with tonsillectomy. The risks of adenoidectomy include velopharyngeal insufficiency, which results in reflux of liquids into the nose whilst swallowing. Patients with cleft palate, either clinically obvious or a submucous cleft, are at higher risk. The tumour often involves the nasopharynx, and, as it enlarges, causes local damage, including to the optic nerve, which can result in blindness. IgA to antiviral capsid antigen has found use as a screening tool in southern China when applied to high-risk groups. B Peritonsillar abscess or quinsy describes an infective process which results in a collection of pus in the peritonsillar space. The tonsil and uvula are pushed medially and there is often significant trismus due to inflammation around the pterygoid muscles. Supportive treatment with fluids, analgesia and antibiotics are often required, but definitive treatment is with transoral incision and drainage under local anaesthetic. In children, a general anaesthetic is required and tonsillectomy is often performed at the same time. Discussion with a senior anaesthetist is advised and orotracheal intubation should be performed in the head-down position so that accidental perforation of the abscess during intubation does not result in aspiration of pus. The abscess cavity can usually be accessed through the oral cavity, although transcervical approaches can be used. The cause of this condition is not clear but may relate to incoordination of relaxation of the upper oesophageal sphincter or abnormalities of the pharyngeal contraction wave. Alcohol consumption is a less significant risk factor, although in combination with cigarette smoke, the effects have been shown to be synergistic. Lesions can spread submucosally, which makes determining surgical margins challenging. The hypopharynx receives a rich, bilateral lymphatic supply, making cervical metastasis common, although not always palpable. B Children with epiglottitis will be febrile and often drooling due to the pain related to swallowing. They should be nursed in a quiet environment and with a parent present to encourage them to remain calm. Intubation should be attempted, but if unsuccessful, a tracheostomy may be required. C Tracheostomy involves producing an entrance to the trachea through the skin of the neck. It can be done in cases of airway obstruction above the level of the tracheostomy in cases of epiglottitis. Following head injury or coma, patients are at risk of aspiration and a tracheostomy can be used to place a cuffed tube and protect the lower airway. Patients who are intubated and ventilated for a prolonged period may be suitable for tracheostomy, which allows a reduction in sedative medications and is more comfortable for the patient. E the anatomical dead space is reduced by around 50 per cent following tracheostomy. Drying of the tracheal epithelium occurs due to loss of the heat and moisture exchange functions of the upper airway, and there is an increase in mucus production which can lead to obstruction of the tube. B Cricothyroidotomy is performed through a vertical skin incision and involves division of the cricothyroid membrane for 1 cm immediately above the cricoid cartilage. Its use is controversial and it may be associated with long-term voice change and subglottic stenosis. The point of entry to the trachea lies immediately below the glottis, and scarring at this point is likely to result in pathological changes to the delicate vocal fold. They are fibrous thickenings of the vocal fold at the junction of the anterior and middle thirds. Speech therapy is the preferred treatment, as surgical excision, injection or radiotherapy would result in further scarring of the vocal fold. The underlying lamina propria of the vocal fold is critical to its function, and treatments aim to leave this untouched. If nodules do not settle with speech therapy, microsurgical techniques can be used to remove them, but patients must be aware that their voice may not return to its original state. Although a unilateral palsy will lead to initial voice change, symptoms may resolve as the contralateral cord compensates. For this reason, post-thyroidectomy follow-up should include visualisation of the larynx to document cord function. Although a unilateral cord palsy will not require a tracheostomy, bilateral palsies, which can follow thyroidectomy, are more likely to require intervention. The cords tend to lie in a paramedian position and compromise the airway in the immediate postoperative period. C Cancer of the larynx most commonly affects the vocal cord and presents with hoarseness. The glottis itself has no lymphatic supply, so until the disease enlarges to involve the subglottis or supraglottis, lymph node metastasis is rare. Early laryngeal cancer does not impair swallowing, but as the disease progresses it can lead to significant changes in pharyngeal function. The vocal folds are removed which clearly changes the voice, although there are multiple strategies which allow patients to speak following surgery. They are available in a range of inner and outer diameters, and with a single tube, or with an inner tube and outer tube. The advantage of a removable inner tube is that removing it to clean the tube does not leave the tracheostomy empty. Speaking valves prevent exhaled air from leaving the tube, diverting it up through the larynx thus allowing phonation. Tracheostomy tubes can interfere with feeding, however feeding tubes must not be placed in the trachea. D Branchial cysts are thought to represent a remnant of the second branchial cleft, although opinions vary. They present in young adults, with a neck mass at the junction of the upper and middle thirds of the sternomastoid muscle. If they become infected, surgical excision is made more challenging and the procedure should be postponed until the infection resolves. The neck is a common site and these soft compressible masses are brilliantly translucent. Cystic hygromas of the neck behave unpredictably and can interfere with the airway, which is an indication for treatment. Definitive treatment involves excision or sclerotherapy; however, extensive, multicystic disease presents a challenge irrespective of the treatment modality. E the thyroid descends from the foramen caecum at the junction of the posterior and middle thirds of the tongue to its position in front of the trachea. If a remnant of this thyroglossal tract fails to involute, a thyroglossal duct cyst is formed. The path of the thyroid hooks around the hyoid bone, so surgical treatment requires excision of the middle of the body of the hyoid to prevent recurrence. Excision of these cysts involves a midline neck dissection to include all branches of the cyst, removal of the hyoid, as described, and excision of a cuff of tongue base tissue. D Following blunt trauma to the larynx, haematoma and swelling can lead to a rapid loss of the airway. Long-term intubation following such an injury will result in a foreign body reaction to the tube which can cause massive permanent fibrosis. Low tracheostomy should be considered with open repair of significant mucosal lacerations and suture repair of displaced cartilage fractures. Laryngeal stents may be left in place for around 5 days and removed endoscopically. Oedema of the floor of the mouth elevates the tongue, which compromises the airway. If swelling continues despite treatment, surgical decompression of the submandibular triangles may be required with division of the mylohyoid to decompress the floor of mouth. A collection can develop in these nodes and, without treatment, pus can erode the deep fascial planes to penetrate up towards the superficial fascia. Here it spreads out within this space and is referred to as a collar-stud abscess. Patients will not show the classic signs of a bacterial abscess (hence the term cold abscess) and ideally incision and drainage should be avoided, as it will also result in a discharging sinus. Appropriate antibiotics and management of renal or pulmonary disease, if coexistent, should be commenced. Occasionally abscesses will fail to resolve, at which point complete surgical excision is the treatment of choice. B Carotid body tumours or chemodectomas are more common at altitude as the chronic hypoxia leads to carotid body hyperplasia. Only 10 per cent have a family history, and although these tumours are associated with phaeochromocytomas, they are not hormonally active themselves. The classic pulsatile mass at the level of the carotid bifurcation can be moved side to side but not up and down. If the mass presents in the parapharyngeal space, intraoral biopsy is also contraindicated as a haematoma can lead to fatal airway compromise. These tumours are slow-growing and benign so the need for surgical removal should be carefully considered. E the classical, radical neck dissection involved removal of all nodes, the sternomastoid, jugular and accessory.
Craniostenosis with congenital heart disease mental retardation
Teebi syndrome
Wandering spleen
Na+ is actively transported (against the concentration gradient) out of cell and K+ is actively transported (against the concentration gradient) into the cell erectile dysfunction medication shots purchase viagra super active 100mg line. However impotence grounds for divorce in tn generic viagra super active 50mg overnight delivery, because of concentration gradient erectile dysfunction fix discount 100 mg viagra super active amex, Na+ diffuses back into the cell through Na+ leak channels and K+ diffuses out of the cell through K+ leak channels erectile dysfunction is caused by buy viagra super active 25mg on-line. In resting conditions erectile dysfunction drugs names buy 100mg viagra super active with amex, almost all the K+ leak channels are opened but most of the Na+ leak channels are closed erectile dysfunction drugs class discount 50 mg viagra super active with visa. Because of this strongest erectile dysfunction pills buy viagra super active 100mg on line, K+ erectile dysfunction from anxiety order 25mg viagra super active with visa, which are transported actively into the cell, can diffuse back out of the cell in an attempt to maintain the concentration equilibrium. But among the Na+, which are transported actively out of the cell, only a small amount can diffuse back into the cell. That means, in resting conditions, the passive K+ efflux is much greater than the passive Na+ influx. Positivity outside the cell repels positive K+ and prevents further efflux of these ions ii. Negativity inside the cell attracts positive K+ and prevents further leakage of these ions outside. Importance of intracellular potassium ions Concentration of K+ inside the cell is about 140 mEq/L. The high concen tration of K+ inside the cell is essential to check the negativity. It is because of the presence of negatively charged proteins, organic phosphates and sulfates, which cannot move out normally. However, the diffusion of K+ out of the cell is many times greater than the diffusion of Na+ inside the cell because many of the K+ leak channels are opened and many of the Na+ leak channels are closed. At this stage, the development of action potential is either delayed or does not occur. Depolarization Depolarization is the initial phase of action potential in which inside of the muscle becomes positive and outside becomes negative. That is, the polarized state (resting membrane potential) is abolished resulting in depolarization. Repolarization Repolarization is the phase of action potential in which the muscle reverses back to the resting membrane potential. That is, within a short time after depolarization the inside of muscle becomes negative and outside becomes positive. Properties of Action Potential Properties of action potential are listed in Table 31. Latent Period Latent period is the period when no change occurs in the electrical potential immediately after applying the stimulus. Stimulus artifact When a stimulus is applied, there is a slight irregular deflection of baseline for a very short period. The artifact occurs because of the disturbance in the muscle due to leakage of current from stimulating electrode to the recording electrode. Overshoot From firing level, the curve reaches isoelectric potential (zero potential) rapidly and then shoots up (overshoots) beyond the zero potential (isoelectric base) up to +55 mV. Repolarization When depolarization is completed (+55 mV), the repolarization starts. Spike potential Rapid rise in depolarization and the rapid fall in repolarization are together called spike potential. After depolarization or negative after potential Rapid fall in repolarization is followed by a slow re polarization. Ionic Basis of Action Potential Voltage gated Na+ channels and the voltage gated K+ channels play important role in the development of action potential. During the onset of depolarization, voltage gated sodium channels open and there is slow influx of Na+. When depolarization reaches 7 to 10 mV, the voltage gated Na+ channels start opening at a faster rate. When the firing level is reached, the influx of Na+ is very great and it leads to overshoot. These channels remain opened for few more milliseconds after completion of repolarization. Biphasic Action Potential Biphasic or diphasic action potential is the series of electrical changes in a stimulated muscle or nerve fiber, which is recorded by placing both the recording electrodes on the surface of the muscle or nerve fiber. It is characterized by a positive deflection followed by an isoelectric pause and a negative deflection. Recording of biphasic action potential Biphasic action potential is recorded by extracellular electrodes, i. In resting state before stimulation, the potential difference between the two electrodes is zero. When the axon is stimulated at one end, the action potential (impulse) is generated and it travels towards the other end of an axon by passing through the recording electrodes. When the impulse reaches first electrode, the membrane under this electrode becomes depolarized (outside negative) but the membrane under second electrode is still in polarized state (outside positive). When the impulse crosses and travels away from the first electrode, the membrane under this electrode is repolarized. Later when the impulse just travels in between the two electrodes (before reaching the second electrode) the potential difference between both the electrode falls to zero and the baseline is recorded. When the impulse reaches the second electrode, the membrane under this electrode is depolarized (outside negative) and a negative deflection is recorded. When the impulse travels away from second electrode, the membrane under this gets repolarized. Once again the potential difference between the two electrodes becomes zero and the graph shows the baseline. Since this recording shows both positive and negative components it is called biphasic action potential. Effect of crushing or local anesthetics When a small portion of axon between the two electrodes is affected by crushing or local anesthetics, the action potential cannot travel through this part of the axon. So, while recording the potential only a single deflection (monophasic) action potential is recorded. While stimulating the whole nerve, all the nerve fibers are activated and produce action potential. The compound action potential is obtained by recording all the action potentials simultaneously. It is also called graded membrane potential, graded depolarization or local potential. It is nonpropagative and characterized by mild depolarization or hyperpolarization. Graded poten tial is distinct from the action potential and the properties of these two potentials are given in table 31. In most of the cases, the graded potential is responsible for the generation of action potential. How ever, in some cases the graded potential hyperpolarizes the membrane potential (more negativity than resting membrane potential) and inhibits the generation of action potential (as in inhibitory synapses: Chapter 140). This advanced technique in modern electrophysiology was established by Erwin Neher in 1992. Patch clamp is modified as voltage clamp to study the ion currents across the membrane of neuron (Chapter 136). The cells isolated from the body are placed in dishes containing culture media and kept in an incubator. Probing a single cell the dish with tissue culture cells is mounted on a microscope. An electrode is fitted to the pipette and connected to a recording device called patch-clamp amplifier. A gentle suction applied to the inside of the pipette forms a tight seal of giga ohms (G) resistance between the membrane and the pipette. This patch (minute part) of the cell membrane under the pipette is studied by means of various approaches called patch-clamp configurations. This allows measurement of current flow through ion channel or channels under the micropipette. Inside-out patch From the cell-attached configuration, the pipette is gently pulled away from the cell. But internal surface of the membrane patch is exposed out hence the name insideout patch. Concentration of ions can 194 Section 3 t Muscle Physiology also helps to study the effects of neurotransmitters and compounds like ozone, Gprotein regulators, etc. Depending upon this, the muscular contraction is classified into two types namely isotonic contraction and isometric contraction (refer previous chapter). During contraction of the muscle, actin (thin) filaments glide over myosin (thick) filaments and form actomyosin complex. Excitation-contraction Coupling Excitation-contraction coupling is the process that occurs in between the excitation and contraction of the muscle. This process involves series of activities, which are responsible for the contraction of excited muscle. Stages of excitation-contraction coupling When a muscle is excited (stimulated) by the impulses passing through motor nerve and neuromuscular junc tion, action potential is generated in the muscle fiber. Now, the calcium ions stored in the cisternae are released into the sarcoplasm. The calcium ions from the sarcoplasm move towards the actin filaments to produce the contraction. It is used to study the effect of alterations in the ion concentrations on the ion channels. Whole-cell patch From the cell-attached configuration, further suction is applied to the inside of the pipette. It causes rupture of the membrane and the pipette solution starts mixing with intracellular fluid. When the mixing is complete, the equilibrium is obtained between the pipette solution and the intracellular fluid. Whole-cell patch is used to record the current flow through all the ion channels in the cell. Outside-out patch From the whole-cell configuration the pipette is gently pulled away from the cell. Immediately, the free ends of the torn membrane fuse and reseal forming a membrane vesicle at tip of the pipette. The pipette solution enters the membrane vesicle and forms the intracellular fluid. The vesicle is placed inside a bath solution, which forms the extracellular environment. This patch is used to study the effect of changes in the extracellular environment on the ion channels. Role of Troponin and Tropomyosin Normally, the head of myosin molecules has a strong tendency to get attached with active site of F actin. However, in relaxed condition, the active site of F actin is covered by the tropomyosin. The loading of troponin C with calcium ions produces some change in the position of troponin molecule. Due to the movement of tropomyosin, the active site of F actin is uncovered and exposed. Each cross bridge from the myosin filaments has got three components namely, a hinge, an arm and a head. After binding with active site of F actin, the myosin head is tilted towards the arm so that the actin filament is dragged along with it. After tilting, the head immediately breaks away from the active site and returns to the original position. Thus, the head of cross bridge bends back and forth and pulls the actin filament towards the center of sarcomere. Hence, the calcium ions are said to form the basis of excitation-contraction coupling. Stage 1: Myosin head binds with actin; Stage 2: Tilting of myosin head (power stroke) drags the actin filament. When the muscle shortens further, the actin filaments from opposite ends of the sarcomere approach each other. Changes in sarcomere during muscular contraction Thus, changes that take place in sarcomere during muscular contraction are: 1. When tropomyosin moves to expose the active sites, the head is attached to the active site. Relaxation of the Muscle Relaxation of the muscle occurs when the calcium ions are pumped back into the L tubules. When calcium ions enter the L tubules, calcium content in sarcoplasm decreases leading to the release of calcium ions from the troponin. It causes detachment of myosin from actin followed by relaxation of the muscle. There are two sources from which the highenergy phosphate is obtained namely, creatine phosphate and carbohydrate metabolism. In the presence of the enzyme creatine phosphotransferase, highenergy phosphate is released from creatine phosphate. Creatine should be resynthesized into creatine phos phate and this requires the presence of highenergy phosphate. So, the required amount of highenergy phosphate radicals is provided by the carbohydrate metabolism in the muscle. The energy liberated during the catabolism of glycogen can cause muscular contraction for a longer period. Molecular Motors Along with other proteins and some enzymes, actin and myosin form the molecular motors, which are involved in movements. Cori cycle Lactic acid is transported to liver where it is converted into glycogen and stored there. Here, the glucose is converted into glycogen, which enters the EmbdenMeyerhof pathway (Figs 31. The pyruvic acid derived from glycolysis is taken into mitochondria where it is converted into acetyl coenzyme A with release of 4 hydrogen atoms. Significance of Hydrogen Atoms Released during Carbohydrate Metabolism Altogether 24 hydrogen atoms are released during glycolysis and Krebs cycle: 4H: During breakdown of glycogen into pyruvic acid 4H: During formation of acetyl coenzyme A from pyruvic acid 16H: During degradation of acetyl coenzyme A in Krebs cycle. In Resting Condition During resting condition, the reaction of muscle is alkaline with a pH of 7. During Onset of Contraction At the beginning of the muscular contraction, the reaction becomes acidic. During Later Part of Contraction During the later part of contraction, the muscle becomes alkaline. At the End of Contraction At the end of contraction, the muscle becomes once again acidic. Heat of Activation Heat of activation is the heat produced before the actual shortening of the muscle fibers. Heat of Shortening Heat of shortening is the heat produced during contraction of muscle. The heat is produced due to various structural changes in the muscle fiber like movements of cross bridges and myosin heads and breakdown of glycogen. Heat of Relaxation Heat released during relaxation of the muscle is known as the heat of relaxation. After the end of muscular activities, some amount of heat is produced due to the chemical processes involved in resynthesis of chemical substances broken down during contraction. Each terminal branch innervates one muscle fiber through the neuromuscular junction. Axon Terminal and Motor Endplate Terminal branch of nerve fiber is called axon terminal. This portion of the axis cylinder is expanded like a bulb, which is called motor endplate. The Ach is synthesized by mitochondria present in the axon terminal and stored in the vesicles. Synaptic Trough or Gutter Motor endplate invaginates inside the muscle fiber and forms a depression, which is known as synaptic trough or synaptic gutter. It is a thin layer of spongy reticular matrix through which, the extracellular fluid diffuses. An enzyme called acetylcholinesterase (AchE) is attached to the matrix of basal lamina, in large quantities. Postsynaptic membrane contains the receptors called nicotinic acetylcholine receptors. Events of Neuromuscular Transmission A series of events take place in the neuromuscular junction during this process. These cause bursting of the vesicles by forcing the synaptic vesicles move and fuse with presynaptic membrane. By exocytosis, acetylcholine diffuses through the presynaptic membrane and enters the synaptic cleft. It increases the permeability of postsynaptic membrane for sodium by opening the ligand-gated sodium channels.
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Secondary memory Secondary memory is the storage of information in brain for a longer period erectile dysfunction after radiation treatment for prostate cancer purchase viagra super active 100mg without prescription. Common stimulants are caffeine impotence caused by medications generic viagra super active 25mg line, physostigmine, amphetamine, nicotine, strychnine and metrazol. Dementia Dementia is the progressive deterioration of intellect, emotional control, social behavior and motivation associated with loss of memory. Clinical features Common features are loss of recent memory, lack of thinking and judgment and personality changes. It is due to degeneration, loss of function and death of neurons in many parts of brain, particularly cerebral hemispheres, hippocampus and pons. There is reduction in the synthesis of most of the neurotransmitters, especially acetylcholine. Synthesis of acetylcholine decreases due to lack of enzyme choline acetyltransferase. Unconditioned reflex is the inborn reflex, which does not need previous experience. In dogs, the duct of parotid gland or submandibular gland was taken outside through cheek or chin respectively and the saliva was collected by some special apparatus. PrimaryConditionedReflex Primary conditioned reflex is the reflex developed with one unconditioned stimulus and one conditioned stimulus. After the development of reflex, the flash of light (conditioned stimulus) alone causes salivary secretion without food (unconditioned stimulus). SecondaryConditionedReflex Secondary conditioned reflex is the reflex developed with one unconditioned stimulus and two conditioned stimuli. After establishment of a conditioned reflex with one conditioned stimulus, another conditioned stimulus is applied along with the first one. For example, the animal is fed with food (unconditioned reflex) and simultaneously a flash of light (first conditioned stimulus) and a bell sound (second conditioned stimulus) are applied. After development of the reflex, bell sound (second conditioned stimulus) alone can cause salivary secretion. TertiaryConditionedReflex In this reflex, a third conditioned stimulus is added and the reflex is established. Many types of conditioned stimuli associated with sight and hearing were employed by Pavlov. External or Indirect Inhibition Established conditioned reflex is inhibited by some form of stimulus, which is quite different from the conditioned stimulus. For example, some disturbing factors like sudden entrance of a stranger, sudden noise or a strong smell can abolish the conditioned reflex and inhibit salivary secretion. If the extra (inhibitory) stimulus is repeated for some time, its inhibitory effect gets weakened or abolished. Internal or Direct Inhibition There are four ways in which the established conditioned reflex is abolished by direct or internal factors, which are related to the conditioned stimulus. It occurs if an established conditioned reflex is not reinforced by unconditioned stimulus. After establishing a conditioned reflex, the conditioned stimulus must be coupled with unconditioned stimulus now and then, i. If a conditioned stimulus is given repeatedly several times, without reinforcing it by unconditioned stimulus, there is failure of conditioned reflex. However, the reflex is not abolished if the unconditioned reflex is also used in between. Conditioned inhibition Conditioned inhibition is the failure of conditioned reflex due to introduction of an unknown (new) conditioned stimulus. When a conditioned stimulus like flash of light is effective, if another conditioned stimulus like a bell sound is applied along with this stimulus suddenly, the response does not occur. Of course, if these two conditioned stimuli are given with unconditioned stimulus (food) repeatedly, the secondary conditioned reflex is developed. Inhibition by delay or delayed conditioned reflex Inhibition by delay is the absence of response or delayed response that occurs while eliciting a conditioned reflex by delaying the unconditioned stimulus. While establishing a conditioned reflex, the conditioned stimulus (light or sound) must be followed by unconditioned stimulus (food) immediately. If the unconditioned stimulus is applied after a long period, response may be absent or delayed. Differential inhibition Differential inhibition is the failure of conditioned reflex that occurs when the conditioned stimulus is altered. When an animal is trained or conditioned for a particular type of conditioned stimulus and if this stimulus is altered even slightly, the response does not occur. For example, the alteration in frequency of sound or intensity of light abolishes the conditioned reflex (Table 162. This type of reflexes is developed by the conditioned stimulus, followed by a reward or a punishment. The instrumental conditioned reflexes are also called operant conditioned reflexes or Skinner conditioning. During the development of this type of reflexes, the animal is taught to perform some task, in order to obtain a reward or to avoid a punishment. Accordingly, the instrumental conditioned reflexes are of several types, such as: 1. ConditionedAvoidanceReflex Conditioned avoidance reflex is the reflex by which the animal is trained to avoid an electric shock, by pressing a bar. Second Stage New neuronal circuits are established during the development of speech. When a definite meaning has been attached to certain words, pathway between the auditory area (Heschl area; area 41) and motor area for the muscles of articulation, which helps in speech (Broca area 44) is established. Role of Cortical Areas in the Development of Speech Development of speech involves integration of three important areas of cerebral cortex: 1. Wernicke area is responsible for understanding the visual and auditory information required for the production of words. It is situated adjacent to the motor area, responsible for the movements of tongue, lips and larynx, which are necessary ConditionedRewardReflex If the animal is rewarded by a banana by pressing a bar, the animal repeatedly presses the bar. Instrumental conditioned reflexes play an important role during the learning processes of a child. These conditioned reflexes are also responsible for the behavior pattern of an individual. Peripheral speech apparatus includes larynx or sound box, pharynx, mouth, nasal cavities, tongue and lips. All the structures of peripheral speech apparatus function in coordination with respiratory system, with the Chapter 162 t Higher Intellectual Functions 945 for speech. By receiving information required for production of words from Wernicke area, the Broca area develops the pattern of motor activities required to verbalize the words. It results in initiation of movements of tongue, lips and larynx required for speech. Later, when the child is taught to read, auditory speech is associated with visual symbols (area 18). Then, there is an association of the auditory and visual areas with the motor area for the muscles of hand. Now, the child is able to express auditory and visual impressions in the form of written words. So, many parts of cortical and subcortical areas are involved in the mechanism of speech. Subcortical areas concerned with speech are controlled by cortical areas of dominant hemisphere. In about 95% of human beings, the left cerebral hemisphere is functionally dominant and those persons are right handed. Broca area Broca area is also called speech center, motor speech area or lower frontal area. Broca area controls the movements of structures (tongue, lips and larynx) involved in vocalization. Upper frontal motor area Upper frontal motor area is situated in paracentral gyrus over the medial surface of cerebral hemisphere. Secondary auditory area Secondary auditory area or auditopsychic area includes area 22. It is concerned with the interpretation of auditory sensation and storage of memories of spoken words. Secondary visual area Secondary visual area or visuopsychic area includes area 18. This area is concerned with the interpretation of visual sensation and storage of memories of the visual symbols. It is responsible for understanding the auditory information about any word and sending the information to Broca area (Table 162. It is an acquired disorder and it is distinct from developmental disorders of speech or other speech disorders like dysarthria. Damage of speech centers impairs the expression and understanding of spoken words. Aphasia may be associated with other speech disorders, which also occur due to brain damage. Causes for Aphasia Usually aphasia occurs due to damage of one or more speech centers, which are situated in cerebral cortex (Table 162. In children, traumatic aphasia can develop by exposure to a horrifying event, without any brain damage. The simple and convenient clinical classification divides aphasia into five types: 1. The affected persons do not complete the sentences because of their inability to construct the sentences. It is due to damage of frontal lobe, which is also responsible for motor activities. Because of this weakness, they are unaware Chapter 162 t Higher Intellectual Functions 947 of their own mistakes while speaking. Wernicke aphasia is not associated with paralysis or weakness of muscles because, the injury does not involve the centers concerned with movements. Global aphasia Global aphasia is the type of aphasia characterized by combined features of Broca aphasia and Wernicke aphasia. It is due to widespread lesion in speech areas caused by infarction of left cerebral hemisphere. Nominal aphasia Nominal aphasia is the speech disorder characterized by inability in naming the familiar objects. Motor aphasia: It is the speech disorder caused by the defect in the pathway between left speech areas and excitomotor or precentral cortex (Chapter 152). It is characterized by difficulty in uttering individual words due to lack of coordination between central speech apparatus (higher cortical centers) and peripheral speech apparatus. It is also called word blindness or dyslexia and it occurs due to the lesion in secondary visual area. Agraphia is due to the defect in the connection between the cortical areas concerned with writing. Agraphia differs from dysgraphia, which is characterized by distorted writing or writing incorrect letters. Dysarthria or anarthria is defined as the difficulty or inability to speak because of paralysis or ataxia of muscles involved in articulation. Causes of Dysarthria Dysarthria is caused by damage of brain or the nerves that control the muscles involved in speech. It occurs in conditions like stroke, brain injury, degenerative disease like Parkinson disease and Huntington disease. Hoarseness means the difficulty in producing sound while trying to speak or a change in the pitch or loudness of voice. Trauma of vocal cords Paralysis of vocal cords Lumps (nodules) on vocal cords Inflammation of larynx Hypothyroidism Stress (psychological dysphonia). It is also described as a speech disorder in which normal flow of speech is disturbed by repetitions, prolongations or abnormal block or stoppage of sound and syllables. It is due to the neurological incoordination of speech and it is common in children. It is thought that stammering may be due to genetic factors, brain damage, neurological disorders or anxiety. Choroid plexuses are tuft of capillary projections present inside the ventricles and are covered by pia mater and ependymal covering. Small amount is absorbed along the perineural spaces into cervical lymphatics and into the perivascular spaces. The mechanism of absorption is by filtration due to pressure gradient between hydrostatic pressure in the subarachnoid space fluid and the pressure that exists in the dural sinus blood. The increased intracranial pressure is reduced by injection of 30% to 35% of sodium chloride or 50% sucrose. Lateral recumbent position: 10 to 18 cm of H2O Lying position: 13 cm of H2O Sitting position: 30 cm of H2O Certain events like coughing and crying increase the pressure by decreasing absorption. However, if the head receives a severe blow, the brain moves forcefully and hits against the skull bone, leading to the damage of brain tissues. Brain strikes against the skull bone at a point opposite to the point where the blow was applied. Regulation of Cranial Content Volume Regulation of cranial content volume is essential because, brain may be affected if the volume of cranial content increases. In lumbar puncture, the lumbar puncture needle is introduced into subarachnoid space in lumbar region, between the third and fourth lumbar spines. After determining the area of fourth lumbar spine, third lumbar spine is palpated. The needle is introduced into subarachnoid space by passing through soft tissue space between the two spines. Spinal cord will not be injured, because, it terminates below the lower border of the first lumbar vertebra. Opposite to midplane, this back of the subject by joining the highest points of Posture of Body for Lumbar Puncture the reclining body is bent forward, so as to flex the vertebral column as far as possible. Injecting drugs (intrathecal injection) for spinal anesthesia, analgesia and chemotherapy 3. However, in capillaries of brain, fenestra are absent because, the endothelial cells fuse with each other by tight junctions. Tight junctions are formed between endothelial cells of the capillaries at childhood. At the same time, cytoplasmic foot processes of astrocytes (neuroglial cells) develop around capillaries and reinforce the barrier. These cells play an important role in formation and maintenance of tight junction and structural stability of the barrier. In brain, pericytes function as macrophages and play an important role in the defense. It prevents potentially harmful chemical substances and permits metabolic and essential materials into the brain tissues. It was observed more than 50 years ago, that when trypan blue, the acidic dye was injected into living animals, all the tissues of body were stained by it, except the brain and spinal cord. This observation suggested that there was a hypothetical barrier, which prevented the diffusion of trypan blue into the brain tissues from the capillaries. It exists in the capillary membrane of all parts of the brain, except in some areas of hypothalamus. Oxygen Carbon dioxide Water Glucose Amino acids Electrolytes Drugs such as L-dopa, 5-hydroxytryptamine sulfonamides, tetracycline and many lipid-soluble drugs 8. Bile pigments: However, since the barrier is not well developed in infants, the bile pigments enter the brain tissues. During jaundice in infants, the bile pigments enter brain and causes damage of basal ganglia, leading to kernicterus (refer Chapter 21 for details). On the other hand, if the arachnoid villi are blocked, external or communicating hydrocephalus occurs. Hydrocephalus along with increased intracranial pressure causes headache and vomiting. In severe conditions, it leads to atrophy of brain, mental weakness and convulsions. It does not allow the movement of many substances from blood to cerebrospinal fluid. Sympathetic division supplies smooth muscle fibers of all the visceral organs such as blood vessels, heart, lungs, glands, gastrointestinal organs, etc. Paravertebral or Sympathetic Chain Ganglia Paravertebral or sympathetic chain ganglia are arranged in a segmental fashion along the anterolateral surface of vertebral column. Ganglia on either side of the spinal cord are connected with each other by longitudinal fibers, to form the sympathetic chains. Ganglia of the sympathetic chain (trunk) on each side are divided into four groups: 1. Preganglionic fibers leave the spinal cord through anterior nerve root and white rami communicantes and terminate in the postganglionic neurons, which are situated in the sympathetic ganglia.
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