Medical Physiology Year Two Paper Two — Past OmpathStudy

--- UNIT CODE : MBMP 2300 UNIT TITLE : Medical Physiology DATE : Thursday, 13th July 2023 TIME : 8:00 AM – 10:00 AM DURATION : 2 Hours --- INSTRUCTIONS This paper consists of two sections: A and B . Attempt all questions in Section A and any two (2) questions from Section B. The use of mobile phones or any form of exam irregularity is strictly prohibited . --- SECTION A – SHORT ANSWER QUESTIONS (60 Marks) PHYSIOLOGY EXAM ANSWERS - SECTION A Short Answer Questions (60 Marks) 1. Three types of nerve fibers with examples (5 marks) A Fibers (Myelinated, Large Diameter) Aα fibers : Motor neurons to skeletal muscle, proprioceptive fibers from muscle spindles (12-20 μm diameter, 70-120 m/s conduction velocity) Aβ fibers : Touch, pressure, vibration sensory fibers (5-12 μm diameter, 30-70 m/s conduction velocity) Aγ fibers : Motor neurons to muscle spindle intrafusal fibers (3-6 μm diameter, 15-30 m/s conduction velocity) Aδ fibers : Sharp pain, cold temperature, some touch sensory fibers (2-5 μm diameter, 12-30 m/s conduction velocity) B Fibers (Lightly Myelinated, Medium Diameter) Preganglionic autonomic fibers (both sympathetic and parasympathetic) 1-3 μm diameter, 3-15 m/s conduction velocity C Fibers (Unmyelinated, Small Diameter) Postganglionic sympathetic fibers Dull, aching pain sensory fibers Warm temperature sensory fibers Some visceral sensory fibers 0.4-1.2 μm diameter, 0.5-2 m/s conduction velocity --- 2. Emmetropia and four types of refractive errors (5 marks) Emmetropia is the normal refractive state of the eye where parallel light rays from distant objects ( 6 meters) focus exactly on the retina without accommodation. The eye has perfect optical power matching its axial length. Four Types of Refractive Errors: A. Myopia (Nearsightedness) Light rays focus in front of the retina Caused by: Excessive axial length of eyeball or excessive refractive power Symptoms: Distant objects appear blurred, near objects clear Correction: Concave (diverging) lenses B. Hyperopia (Farsightedness) Light rays focus behind the retina Caused by: Insufficient axial length of eyeball or insufficient refractive power Symptoms: Near objects appear blurred (accommodation strain), distant objects may be clear Correction: Convex (converging) lenses C. Astigmatism Irregular curvature of cornea or lens causing different refractive powers in different meridians Light rays do not focus at a single point Symptoms: Blurred vision at all distances, eye strain, headaches Correction: Cylindrical lenses to correct the meridian with abnormal curvature D. Presbyopia Age-related loss of lens elasticity and accommodation ability Begins around age 40-45 years Symptoms: Difficulty focusing on near objects, need to hold reading material farther away Correction: Convex lenses for near vision, bifocals, or progressive lenses --- 3. Physiological events during REM sleep (5 marks) Neurological Events: Rapid eye movements (horizontal, vertical, and oblique) Vivid, complex dreaming with emotional content Increased brain activity similar to waking state Activation of visual, motor, and limbic areas Suppression of norepinephrine, serotonin, and histamine release Motor System Changes: Muscle atonia (paralysis of voluntary muscles except diaphragm and extraocular muscles) Inhibition of spinal motor neurons via glycine and GABA Occasional muscle twitches despite atonia Preserved respiratory muscle function Autonomic Changes: Fluctuations in heart rate and blood pressure Irregular breathing patterns Loss of thermoregulation (poikilothermic state) Increased oxygen consumption and metabolic rate Penile erections in males/clitoral engorgement in females Hormonal Changes: Decreased growth hormone release Reduced cortisol secretion Suppressed antidiuretic hormone (ADH) release --- 4. Decussation and its significance in the pyramidal motor system (5 marks) Definition of Decussation: Decussation refers to the crossing over of nerve fibers from one side of the nervous system to the other, forming an X-shaped intersection. Pyramidal System Decussation: Occurs at the pyramidal decussation (decussation of pyramids) in the medulla oblongata 85-90% of pyramidal tract fibers cross to the opposite side Forms the lateral corticospinal tract 10-15% remain uncrossed, forming the anterior corticospinal tract Significance: A. Contralateral Motor Control Left cerebral hemisphere controls right side of body and vice versa Explains why unilateral brain lesions cause motor deficits on the opposite side B. Clinical Implications Stroke in left motor cortex causes right-sided hemiplegia Upper motor neuron lesions above decussation cause contralateral symptoms Lower motor neuron lesions below decussation cause ipsilateral symptoms C. Evolutionary Advantage Allows for better integration of sensory input and motor output Facilitates coordinated bilateral movements Enables specialization of cerebral hemispheres --- 5. Functions of Cholecystokinin (CCK) (5 marks) Digestive Functions: Gall