Weekly Year 2: Physiology Exam - May 15, 2026 (Section A: MC

Question 1

The following neurotransmitter is used by the substantia nigra neurons that project to the caudate and putamen:

Accepted Answer

Dopamine — The nigrostriatal pathway, originating in the substantia nigra pars compacta and projecting to the caudate and putamen, primarily uses dopamine as its neurotransmitter. This pathway is crucial for motor control.

Question 2

Which of the following items correctly describes the relationship of cerebrospinal fluid pressure to the venous pressure in the superior sagittal sinus?

Accepted Answer

CSF pressure is normally lower than venous pressure in the superior sagittal sinus. — Cerebrospinal fluid (CSF) pressure is normally maintained below the venous pressure in the superior sagittal sinus. This pressure gradient facilitates the outflow of CSF into the venous system via the arachnoid villi.

Question 3

Output signals from Golgi tendon organs are transmitted to which of the following higher centers?

Accepted Answer

Brainstem and spinal cord — Golgi tendon organs provide proprioceptive information about muscle tension. Their afferent signals project to the spinal cord (inhibiting motor neurons) and to the brainstem (e.g., vestibular nuclei, reticular formation), which then influence posture and movement. Some projections also reach the cerebellum.

Question 4

Which type of cholinergic receptor is found at synapses between preganglionic and postganglionic neurons of the sympathetic system?

Accepted Answer

Nicotinic receptors — The synapse between preganglionic and postganglionic neurons in the autonomic nervous system (both sympathetic and parasympathetic) is cholinergic and utilizes nicotinic acetylcholine receptors.

Question 5

The term limbic cortex includes the orbitofrontal cortex, subcallosal gyrus, cingulate gyrus, and which one of the following areas?

Accepted Answer

Hippocampal formation — The limbic cortex is a collection of cortical areas involved in emotion, memory, and motivation. In addition to the orbitofrontal cortex, subcallosal gyrus, and cingulate gyrus, it includes the parahippocampal gyrus and the hippocampal formation.

Question 6

Occlusion of which of the following structures would lead to communicating hydrocephalus?

Accepted Answer

Arachnoid villi — Communicating hydrocephalus occurs when there is an obstruction to CSF flow after it leaves the ventricles, or impaired absorption. Occlusion or dysfunction of the arachnoid villi, the primary site of CSF absorption into the venous system, leads to this condition.

Question 7

The withdrawal reflex is initiated by stimulation delivered to which of the following receptors?

Accepted Answer

Nociceptors — The withdrawal reflex is a protective reflex that withdraws a limb from a painful stimulus. This reflex is initiated by the activation of nociceptors, which detect pain.

Question 8

Which substance activates adrenergic alpha and beta receptors equally well?

Accepted Answer

Epinephrine — Epinephrine has roughly equal affinity for alpha and beta adrenergic receptors. Norepinephrine has a higher affinity for alpha receptors, while isoproterenol is a potent beta-adrenergic agonist with little alpha activity. Dopamine has distinct receptor effects.

Question 9

The posterior and lateral hypothalamus, in combination with the preoptic area, are involved in the control of which of the following functions?

Accepted Answer

Thermoregulation and feeding behavior — The hypothalamus, including the posterior, lateral, and preoptic areas, plays a central role in regulating fundamental homeostatic functions such as body temperature (thermoregulation) and appetite/satiety (feeding behavior).

Question 10

Which statement concerning the reticulospinal system is correct?

Accepted Answer

It plays a major role in maintaining posture and balance. — The reticulospinal tracts, originating from the reticular formation in the brainstem, are crucial for modulating muscle tone, maintaining posture, and influencing the excitability of motor neurons, thereby playing a significant role in balance.

Question 11

The neurons located in the locus ceruleus release which of the following neurotransmitters at their synaptic terminals?

Accepted Answer

Norepinephrine — The locus ceruleus, a nucleus in the pons, is the principal site for brain synthesis of norepinephrine. Its neurons project widely throughout the CNS and are involved in arousal, attention, and mood.

Question 12

Which of the following items represents the structural basis of the blood-cerebrospinal fluid barrier?

Accepted Answer

Tight junctions between epithelial cells of the choroid plexus — The blood-cerebrospinal fluid (CSF) barrier is formed by the specialized epithelial cells of the choroid plexus. These cells have tight junctions that restrict the passage of substances from the blood into the CSF, ensuring a highly regulated environment for the brain.

Question 13

Which of the following is a component of the renal response to metabolic acidosis?

Accepted Answer

Increased generation of new bicarbonate — In metabolic acidosis, the kidneys respond by increasing the reabsorption of filtered bicarbonate and increasing the generation of new bicarbonate to buffer the excess acid. Ammonium excretion also increases to help excrete acid.

Question 14

Which of the following will not lead to a diuresis?

Accepted Answer

Increased secretion of antidiuretic hormone (ADH) — Increased secretion of ADH promotes water reabsorption in the kidneys, leading to decreased urine output and a more concentrated urine, thus preventing diuresis.

Question 15

Which of the following contributes directly to the generation of a hypertonic medullary interstitium in the kidney?

Accepted Answer

Countercurrent multiplication in the loop of Henle — The countercurrent multiplication mechanism, driven by active transport of NaCl out of the thick ascending limb of the loop of Henle, creates and maintains the high solute concentration in the renal medullary interstitium, which is essential for concentrating urine.

Question 16

An increase in renin is caused by

Accepted Answer

Decreased sodium delivery to the macula densa — Renin release is stimulated by decreased renal perfusion pressure, decreased sympathetic tone, and decreased sodium chloride delivery to the macula densa. Increased angiotensin II levels inhibit renin release via a negative feedback mechanism.

Question 17

What happens at plasma concentrations of glucose higher than transport maximum (TM)?

Accepted Answer

Glucose appears in the urine (glucosuria). — The transport maximum (TM) for glucose reabsorption in the renal tubules represents the maximum rate at which glucose can be reabsorbed. When the filtered load of glucose exceeds this TM, the excess glucose is not reabsorbed and appears in the urine, causing glucosuria.

Question 18

Which of the following would produce an increase in the reabsorption of isosmotic fluid in the proximal tubule?

Accepted Answer

Increased peritubular capillary oncotic pressure — The reabsorption of isosmotic fluid in the proximal tubule is driven by Starling forces in the peritubular capillaries. An increase in peritubular capillary oncotic pressure favors reabsorption, while increased hydrostatic pressure opposes it.

Question 19

Which of the following would cause an increase in both glomerular filtration rate (GFR) and renal plasma flow (RPF)?

Accepted Answer

Constriction of the afferent arteriole — Dilation of the afferent arteriole increases blood flow into the glomerulus, which increases both GFR and RPF, assuming other factors remain constant. Constriction of the efferent arteriole would increase GFR but decrease RPF.

Question 20

Which of the following is true about reabsorption of filtered HCO3-?

Accepted Answer

It requires secretion of H+ into the tubular lumen. — Reabsorption of filtered bicarbonate in the proximal tubule involves the secretion of H+ into the tubular lumen, where it combines with filtered HCO3- to form H2CO3. This H2CO3 then dissociates, and the resulting CO2 diffuses into the tubular cells to be re-formed into HCO3- which is then reabsorbed.

Question 21

Kipchoge runs a marathon in 90°F weather and replaces all volume lost in sweat by drinking distilled water. After the marathon, she will have

Accepted Answer

Hyponatremia and decreased plasma osmolality — Sweat is hypotonic to plasma, meaning it contains less sodium than plasma. Drinking large amounts of distilled water (which is essentially pure water) without electrolyte replacement will lead to a dilution of plasma sodium, causing hyponatremia. This dilution also decreases plasma osmolality.

Question 22

Which of the following is a cause of metabolic alkalosis?

Accepted Answer

Vomiting — Vomiting leads to a loss of gastric acid (HCl), which can cause metabolic alkalosis. Severe diarrhea typically causes metabolic acidosis due to loss of bicarbonate-rich intestinal fluid. Lactic acidosis and diabetic ketoacidosis are also causes of metabolic acidosis.

Question 23

The decision to delay extraction of the oocyte until 7 hours after a rise in LH levels is because the midcycle LH surge causes

Accepted Answer

Completion of meiosis I and progression to metaphase II — The LH surge triggers the resumption of meiosis in the oocyte, which has been arrested in prophase I since fetal development. This resumption leads to the completion of meiosis I and the formation of a secondary oocyte arrested in metaphase II, which is the stage at which ovulation occurs.

Question 24

Loss-of-function mutations of which enzyme would be responsible for the presence of labia in an XY subject at birth?

Accepted Answer

Aromatase — Aromatase converts androgens (like testosterone) to estrogens. In XY individuals, androgens are responsible for masculinization of external genitalia. If aromatase is deficient, the conversion of androgens to estrogens is impaired, leading to incomplete masculinization and potentially feminized external genitalia (e.g., presence of labia).

Question 25