39 Year 2: Physiology exam questions on Medical Physiology IV (CNS) for medical students. Includes MCQs, answers, explanations and written questions. Sample: Th
This MCQ set contains 39 questions on Medical Physiology IV (CNS) in the Year 2: Physiology unit. Each question includes the correct answer and a detailed explanation for active recall and exam preparation.
Correct answer: B – Dopamine
The substantia nigra contains dopaminergic neurons that project to the caudate nucleus and putamen (collectively called the striatum) via the nigrostriatal pathway. This dopaminergic pathway is crucial for motor control and is affected in Parkinson's disease. The other neurotransmitters listed are not the primary neurotransmitters used by substantia nigra neurons in this pathway. ---
Correct answer: A – A few millimeters higher
CSF pressure is normally maintained at a few millimeters of mercury higher than venous pressure in the superior sagittal sinus. This pressure gradient is essential for CSF drainage through the arachnoid granulations into the venous system. If CSF pressure were lower or equal to venous pressure, proper drainage would not occur. ---
Correct answer: A – The output signals of a Golgi tendon organ lead to inactivation of the muscle associated with the active tendon organ
Golgi tendon organs detect muscle tension and when activated, they cause inhibition of the muscle they monitor (autogenic inhibition). This is opposite to muscle spindles, which detect muscle stretch and cause activation of the same muscle. The other options are incorrect as Golgi tendon organs do function during voluntary movements, do contribute to proprioception, are not directly linked to alph
Correct answer: C – Cerebellum
Golgi tendon organs send proprioceptive information about muscle tension to the cerebellum via spinocerebellar tracts. The cerebellum uses this information for motor coordination and balance. The other structures listed are not primary targets for Golgi tendon organ afferents. ---
Correct answer: B – Nicotinic
All autonomic ganglia (both sympathetic and parasympathetic) use nicotinic cholinergic receptors at the synapse between preganglionic and postganglionic neurons. Muscarinic receptors are found at parasympathetic postganglionic terminals, while alpha and beta receptors are adrenergic receptors found at sympathetic postganglionic terminals. ---
Correct answer: D – Parahippocampal gyrus
The limbic cortex includes the parahippocampal gyrus along with the orbitofrontal cortex, subcallosal gyrus, and cingulate gyrus. These areas are involved in emotion, memory, and behavior. The other options are not considered part of the limbic cortex. ---
Correct answer: E – Arachnoid villi
Communicating hydrocephalus occurs when CSF can flow through the ventricular system but cannot be absorbed properly. Obstruction of arachnoid villi (granulations) prevents CSF absorption into the venous system, leading to communicating hydrocephalus. Obstruction of the other structures would cause non-communicating (obstructive) hydrocephalus. ---
Correct answer: C – Cutaneous free nerve ending
The withdrawal reflex is a protective reflex triggered by noxious stimuli detected by cutaneous free nerve endings (nociceptors). These receptors detect potentially harmful stimuli and initiate rapid withdrawal from the stimulus. The other receptors listed detect different types of stimuli but are not primarily involved in withdrawal reflexes. ---
Correct answer: C – Epinephrine
Epinephrine (adrenaline) has equal affinity for both alpha and beta adrenergic receptors. Norepinephrine has higher affinity for alpha receptors than beta receptors. Acetylcholine, serotonin, and dopamine are not adrenergic receptor agonists. ---
Correct answer: B – Regulation of thirst and water intake
The posterior and lateral hypothalamus, along with the preoptic area, are key regions involved in osmoregulation and thirst control. These areas contain osmoreceptors that detect changes in blood osmolality and initiate appropriate responses including thirst and ADH release. The other functions are controlled by different hypothalamic regions. ---
Correct answer: E – Pontine reticulospinal fibers excite spinal cord motor neurons that activate limb extensor muscles
Pontine reticulospinal fibers facilitate extensor muscle tone and activity, while medullary reticulospinal fibers generally inhibit extensor muscles and facilitate flexor muscles. The other statements are incorrect: reticulospinal neurons do receive cortical input, medullary fibers inhibit rather than excite extensors, and pontine fibers course in the ventral funiculus, not posterior funiculus. --
Correct answer: A – Norepinephrine
The locus ceruleus is the major noradrenergic nucleus in the brain, containing norepinephrine-producing neurons that project widely throughout the CNS. These neurons are involved in arousal, attention, and stress responses. The other neurotransmitters are produced by different neural populations. ---
Correct answer: C – Tight junctions between adjacent choroid plexus cells
The blood-CSF barrier is formed by tight junctions between choroid plexus epithelial cells. This barrier controls the movement of substances from blood into CSF. Option E describes the blood-brain barrier, while the other options are not correct structural bases for the blood-CSF barrier. ---
Correct answer: C – Junction of the parietal, temporal, and occipital lobes
Wernicke's area, located at the junction of the parietal, temporal, and occipital lobes in the dominant hemisphere, is responsible for language comprehension. Damage to this area results in Wernicke's aphasia, characterized by inability to comprehend written or spoken language. The other areas are not primarily involved in language comprehension. ---
Correct answer: B – Amygdala
The amygdala is crucial for processing emotions and social behavior, including the ability to recognize social cues and respond appropriately to social situations. Dysfunction of the amygdala can lead to inappropriate social behavior and difficulty reading social situations. The other structures, while important for various functions, are not primarily responsible for social appropriateness. ---
Correct answer: A – Crossed extensor reflex
The crossed extensor reflex occurs when a painful stimulus causes withdrawal of the affected limb (flexion) while simultaneously causing extension of the opposite limb to maintain balance and support. This involves antagonistic muscle groups on both sides of the body. The withdrawal reflex only involves the affected side, while reciprocal and autogenic inhibition are different mechanisms. ---
Correct answer: C – An imbalance in the activity of medullary and pontine reticulospinal systems such that excitation of extensor motor neurons is the end result
Decerebrate rigidity results from damage above the level of the vestibular nuclei, leading to an imbalance where pontine reticulospinal activity (which facilitates extensors) predominates over medullary reticulospinal activity (which inhibits extensors). This results in excessive extensor muscle tone and rigidity. ---
Correct answer: D – Cerebrocerebellum and dentate nucleus
The cerebrocerebellum (lateral hemispheres) and dentate nucleus are involved in motor planning and coordination of complex, sequential movements. They receive input from cerebral cortex and are important for cognitive aspects of motor control. The other cerebellar regions have different functions related to balance, posture, and limb coordination. ---
Correct answer: C – Excessive eating, rage and aggression, hyperactivity
The ventromedial hypothalamus contains the satiety center. Bilateral lesions of this area result in hyperphagia (excessive eating), leading to obesity, along with increased aggression and hyperactivity. This is opposite to what would occur with lateral hypothalamic lesions, which would cause decreased eating. ---
Correct answer: E – Medial forebrain bundle
The medial forebrain bundle is a major pathway connecting limbic structures to the brainstem, particularly the hypothalamus. It carries both ascending and descending fibers and is important for emotional and motivational behaviors. The other structures have different functions and connections within the limbic system. ---
Correct answer: A – Systemic blood vessels
Systemic blood vessels receive predominantly sympathetic innervation and have minimal parasympathetic innervation. Sympathetic stimulation causes vasoconstriction of most systemic vessels. The other organs listed receive dual innervation from both sympathetic and parasympathetic systems, with varying degrees of dominance. ---
Correct answer: C – Semicircular canals
The semicircular canals detect angular acceleration (rotational head movements). They contain the ampullae with hair cells that respond to endolymph movement during rotation. The macula, saccule, and statoconia are involved in detecting linear acceleration and gravity, not angular acceleration. ---
Correct answer: B – Broca's area
Broca's area is responsible for speech production and motor aspects of language. Damage to this area results in Broca's aphasia, where comprehension is intact but speech production is severely impaired. Wernicke's area damage would affect comprehension, while the other areas are not primarily involved in speech production. ---
Correct answer: E – Dopamine
The dopamine hypothesis of schizophrenia suggests that excessive dopaminergic activity, particularly in the mesolimbic pathway, contributes to the positive symptoms of schizophrenia. Antipsychotic medications work by blocking dopamine receptors. The other neurotransmitters are not primarily implicated in schizophrenia pathophysiology. ---
Correct answer: B – Dentate nucleus
The dentate nucleus is part of the cerebellum, not the basal ganglia. The basal ganglia includes the caudate nucleus, putamen, globus pallidus, substantia nigra, and subthalamic nucleus. The dentate nucleus is the largest of the deep cerebellar nuclei and is involved in motor planning and coordination. ---