Physiology Master’s Degree Review – Knowledge Compilation

Physiology Master’s Degree Review – Knowledge Compilation

I. Reflexes

• Flexor reflex:

• Characteristics:

• Summation: Reflex intensity increases with repeated stimulation.

• Habituation: With continuous stimulation, the reflex gradually decreases and may disappear.

• Dependent on stimulation frequency: Higher stimulation frequency leads to stronger reflexes.

• Dependent on the stimulated skin area and the initial position of the limb: Different stimulation locations and initial limb positions result in different reflexes.

• Spinal reflexes:

• Related to the autonomic nervous system, non-segmental: Sweating, goose bumps, vasomotor.

• Related to the autonomic nervous system, segmental, anal reflex: Lumbar 5 sacral 5.

• Related to the autonomic nervous system, segmental, bladder reflex: Sacral 3-5.

• Related to the autonomic nervous system, segmental, blinking reflex: Cervical 4 thoracic 2.

• Related to the autonomic nervous system, segmental, erection reflex: Lumbar sacral.

II. Receptors and Neurotransmitters

• Alpha receptors:

• Location: Smooth muscle cell membranes of peripheral blood vessels and internal organs.

• Action: Vasoconstriction.

• Beta receptors:

• Location: Heart muscle, smooth muscle cell membranes of coronary arteries, skeletal muscle blood vessels, intestinal smooth muscle, uterus, bladder wall, bronchial smooth muscle, liver cells, and adipose tissue cells.

• Beta 1:

• Location: Heart muscle, sinoatrial node, atrioventricular node.

• Action: Increased heart contraction, increased conduction velocity, increased heart rate, increased myocardial contractility.

• Beta 2:

• Location: Smooth muscle of coronary and skeletal muscle vessels, Reissessens muscle of bronchioles, smooth muscle of the gastrointestinal tract, uterus, bladder wall.

• Action: Vasodilation, bronchodilation, uterine relaxation.

• Neurotransmitters:

• Alpha receptors:

• Molecular weight: 55 kDa.

• Ability to bind with the NH2 group in the side chain of the alkyl chain.

• Beta receptors:

• Molecular weight: 100 kDa.

• CH3 group in the side chain.

III. Pathway of Nerve Bundles

• Pyramidal tract:

• Neuro 1: Primary and premotor areas (motor cortex) in the precentral gyrus.

• Direct pyramidal tract (corticospinal tract): Anterior column –> crosses to the contralateral anterior horn (synapses with lower motor neurons in the contralateral anterior horn).

• Crossed pyramidal tract (lateral corticospinal tract): Crosses to the contralateral side at the medulla oblongata –> descends to the spinal cord and synapses with the second neuron in the contralateral anterior horn.

• Rubrospinal tract: Originates from the red nucleus in the midbrain.

• Tectospinal tract: Originates from the superior colliculus of the midbrain.

• Rubrospinal and tectospinal tracts: Immediately after their origin, they cross to the contralateral side –> descend through the lateral column of the spinal cord –> synapse with neurons in the contralateral anterior horn.

• Reticulospinal tract: Originates from the reticular formation of the brainstem –> descends directly to the anterior horn of the spinal cord.

• Vestibulospinal tract: Originates from the vestibular nuclei in the medulla oblongata.

• Fasciculus longitudinalis medialis (MLF): Originates from the MLF nuclei in the medulla oblongata.

IV. Autonomic Nervous System

• Stellate ganglion:

• Composition: Pre-ganglionic fibers from thoracic spinal segments II-IX, post-ganglionic fibers in the Vieussens plexus.

• Distribution: To organs in the neck and upper limb.

• Travels within the inferior cardiac nerve –> innervates muscles in the chest.

• Celiac ganglion:

• Receives pre-ganglionic fibers from thoracic spinal segments V-X (within the greater and lesser splanchnic nerves).

• Pre-vertebral ganglion.

• Also known as the visceral and superior mesenteric ganglion.

• Post-ganglionic fibers travel to the stomach, liver, spleen, and small intestine.

• Post-ganglionic fibers travel along the celiac artery and superior mesenteric artery.

• Meissner and Auerbach plexuses:

• Parasympathetic ganglia.

• Located in the wall of the stomach and intestines.

• Receive pre-ganglionic fibers located in the vagus nerve, originating from the medulla oblongata.

• Sympathetic stimulation:

• Eye: Contraction of the radial muscle of the iris causing dilation of the pupil.

• Parasympathetic stimulation:

• Eye: Contraction of the circular muscle of the iris causing constriction of the pupil, contraction of the ciliary muscle, increased tension of the suspensory ligament, lens becomes more convex, focusing on nearby objects.

V. Hormones

• Epinephrine:

• Stronger effect on heart activity.

• Dilates blood vessels in skeletal muscle and heart muscle.

• Less increase in blood pressure.

• Significantly increases cardiac output.

• Increases basal metabolic rate several times.

• Norepinephrine:

• Significantly increases peripheral resistance.

• Greatly increases blood pressure.

• GH (Growth hormone):

• Stimulates the growth of long bones in the body, especially during the pre-pubertal period.

• Works through stimulating the liver to secrete the growth factor IGF-1.

• Prolactin: Stimulates the mammary glands to secrete milk.

VI. Cardiovascular Regulation

• Reflex due to receptors in the ventricles: Decreases heart rate, decreases peripheral resistance similar to pressure receptors in arteries.

• Peripheral chemoreceptors: Located in the carotid sinus and aortic arch (similar to pressure receptors).

• Stimulation of chemoreceptors: Due to a decrease in pO2, increase in PaCO2, and decrease in H+ (weaker).

• Components of the cardiovascular autonomic reflex arc regulating blood pressure: Pressoreceptors, vagus nerve, brainstem, sympathetic nerve, sinoatrial node.

VII. Hypothalamic Regulation of Autonomic Nervous System Activity: Regulates circulation, temperature, appetite, thirst.

VIII. Tendon Reflexes

• Biceps reflex: Cervical 5,6.

• Triceps reflex: Cervical 7,8.

• Patellar reflex: Lumbar 3,4.

• Achilles reflex: Sacral 1,2.

IX. Digestion

• Sympathetic stimulation:

• Inhibits intestinal motility.

• Increases the tonicity of sphincters.

• Decreases food transport.

• Inhibits mucus secretion by the Brunner glands in the duodenum.

• Parasympathetic stimulation:

• Increases motility, increases the movement of substances.

• Increases secretion of digestive glands.

• Gastrointestinal reflex: Occurs when the duodenum is distended, when chyme is hypertonic/acidic due to the digestion of protein. Through 3 pathways: direct, sympathetic, parasympathetic.

• Gastrin:

• G cells in the pylorus.

• Stimulates HCl secretion, promotes food emptying, increases pyloric motility, inhibits pyloric sphincter, promotes pancreatic exocrine secretion of digestive enzymes.

• Histamine:

• ECL cells under the stimulation of gastrin/acetylcholine.

• Stimulates HCl secretion.

• Acetylcholine:

• Intermediate chemical of the vagus nerve and enteric nervous system.

• Stimulates HCl secretion.

• Cholecystokinin:

• I cells in the small intestine.

• Due to fat (free fatty acids) and amino acids entering the duodenum.

• Increases intestinal motility, inhibits food emptying from the stomach, secretes more pancreatic exocrine enzymes, contracts the gallbladder, relaxes the sphincter of Oddi.

• Secretin:

• S cells in the duodenal and upper jejunal mucosa.

• Due to gastric acid entering the duodenum: S cells are sensitive to pH.

• Secretes more pancreatic juice, reduces intestinal motility, inhibits food emptying from the stomach, stimulates pepsinogen secretion, promotes duct cells to secrete water and ions of bile.

• Increased intestinal motility: Gastrointestinal reflex, gastrin, cholecystokinin, motikin, insulin.

• Decreased intestinal motility: Secretin, glucagon.

X. Calcium

• Primarily absorbed in the duodenum and jejunum.

XI. Aldosterone

• Factors stimulating increased aldosterone secretion: Increased K+ concentration in the extracellular fluid, increased angiotensin II secretion in the blood, decreased circulatory volume.

XII. Pituitary Gland

• Anterior pituitary gland: Secretes STH, TSH, ACTH, GH (FSH, LH, LTH).

• Posterior pituitary gland: Nervous part, only stores hormones secreted by the hypothalamus: vasopressin, oxytocin.

XIII. Cardiac Activity

• HSL enzyme: Stimulates adipose tissue cells to release free fatty acids into the blood.

• Stimulation of HSL enzyme: Glucagon, cortisol, progesterone.

• Conduction velocity of fast response cardiomyocytes: 0.3-1 m/s.

• Conduction velocity of fast response specialized fibers in the atria and ventricles: 1-4 m/s.

• Conduction velocity of slow response cardiomyocytes: 0.02-0.1 m/s.

• L-type calcium channel in the cardiomyocyte membrane opens during the phase: Phase 2 – plateau phase.

XIV. Clearance

• Parameters measured by clearance: Renal plasma flow, renal blood flow, glomerular filtration rate, effective renal plasma flow.

XV. Water Reabsorption

• Distal convoluted tubule: 18 L/24h (10%).

• Collecting duct: 16.74 L/24h (9.3%).

XVI. Afferent Arteriole of the Glomerulus: Straight and short branch of the interlobular arteriole.

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