Medical Physiology Paper I — Exam III, Q1–50 OmpathStudy

Continued from $1. PROGRAMME: Bachelor of Medicine and Bachelor of Surgery (MBChB II) UNIT CODE: BMP 2115 UNIT TITLE: Medical Physiology II EXAMINATION: Main Examination DATE: July 2016 DURATION: 3 Hours --- INSTRUCTIONS: SECTION A is COMPULSORY. Select the single best response for each multiple-choice question. Attempt all questions . --- Medical Physiology II MCQs - Answer Key --- SECTION A: COMPULSORY - SELECT THE SINGLE BEST RESPONSE Question 1 The ability to detect two points simultaneously applied to the skin is based on the following physiologic mechanisms: A) Presynaptic inhibition B) Lateral inhibition C) Medial inhibition D) Feed-forward inhibition Answer: B) Lateral inhibition Explanation: Two-point discrimination depends on lateral inhibition, which enhances contrast between adjacent sensory inputs. This mechanism allows the nervous system to distinguish between two closely applied stimuli by inhibiting surrounding neurons, thereby sharpening the sensory signal and improving spatial resolution. --- Question 2 For a sensory nerve fiber that is connected to a Pacinian corpuscle located on palmar surface of the left hand, the synaptic connection with the subsequent neuron in the corresponding sensory pathway is located in: A) The right dorsal column nucleus B) The left dorsal column nucleus C) The dorsal horn of the right side of the spinal cord D) The dorsal horn of the left side of the spinal cord Answer: B) The left dorsal column nucleus Explanation: Pacinian corpuscles are mechanoreceptors that use the dorsal column-medial lemniscal pathway. The first synapse occurs in the dorsal column nuclei (gracilis or cuneatus) on the same side as the stimulus. Since the corpuscle is on the left hand, the synapse occurs in the left dorsal column nucleus. --- Question 3 The following statement concerning synaptic transmission is correct: A) When a specific population of synaptic terminals is spread over the considerable surface of a neuron, their collective effects cannot spatially summate and lead to initiation of an action potential B) Even if the successive discharges of an excitatory synapse occur sufficiently close in time, they cannot temporally summate and initiate an action potential C) A neuron is "facilitated" when its membrane potential is moved in the less negative or depolarizing direction D) Even when rapidly stimulated by excitatory synaptic input for a prolonged period of time, neurons typically do not exhibit synaptic fatigue Answer: C) A neuron is "facilitated" when its membrane potential is moved in the less negative or depolarizing direction Explanation: Facilitation occurs when the membrane potential becomes less negative (depolarized), bringing it closer to threshold. Options A and B are incorrect because both spatial and temporal summation do occur. Option D is incorrect because synaptic fatigue does occur with prolonged stimulation. --- Question 4 Which of the following substances will elicit the sensation of sour taste? A) Aldehydes B) Alkaloids C) Amino acids D) Hydrogen ions E) Ketones Answer: D) Hydrogen ions Explanation: Sour taste is specifically triggered by hydrogen ions (H+) or acids. The other substances trigger different taste sensations: alkaloids typically taste bitter, while amino acids can taste sweet or umami. --- Question 5 When comparing the fovea with the periphery of the retina, which of the following statements is correct? A) The fovea contains an increased proportion of cones B) The fovea contains an increased proportion of ganglion cells C) The fovea contains an increased proportion of horizontal cells D) The fovea contains an increased proportion of rods E) The fovea contains an increased proportion of vasculature Answer: A) The fovea contains an increased proportion of cones Explanation: The fovea is specialized for high-acuity color vision and contains almost exclusively cones. The periphery contains mostly rods for low-light vision. The fovea actually has fewer blood vessels to avoid interfering with light transmission. --- Question 6 Which of the following is the middle ear ossicle that is attached to the tympanic membrane? A) Columella B) Incus C) Malleus D) Modiolus E) Stapes Answer: C) Malleus Explanation: The malleus (hammer) is directly attached to the tympanic membrane and is the first ossicle in the chain. The incus (anvil) is in the middle, and the stapes (stirrup) connects to the oval window. --- Question 7 Light entering the eye passes through which retinal layer first? A) Inner nuclear layer B) Outer nuclear layer C) Outer plexiform layer D) Photoreceptor layer E) Retinal ganglion layer Answer: E) Retinal ganglion layer Explanation: The retina is "inverted," meaning light must pass through all the neural layers before reaching the photoreceptors. The ganglion cell layer is the innermost layer and is encountered first by incoming light. --- Question 8 Which of the following best describes the "blind spot" of the eye? A) Located 5 degrees lateral