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NEET Zoology
Human Physiology

Zoology questions for NEET UG — Animal Kingdom, Human Physiology, Genetics, Evolution.

25 Q 6 Topics Take Mock Test
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Topics in NEET Zoology
A marathon runner experiences muscle cramps after 2 hours of intense exercise despite adequate hydration. Analysis shows normal blood glucose and electrolyte levels. Which physiological mechanism most likely explains this condition?
A Accumulation of lactate and hydrogen ions beyond the muscle's buffering capacity
B Depletion of muscle glycogen stores triggering involuntary contractions
C Excessive calcium influx into the sarcoplasm causing sustained contraction
D Reduced oxygen availability preventing ATP resynthesis in mitochondria
Correct Answer:  A. Accumulation of lactate and hydrogen ions beyond the muscle's buffering capacity
EXPLANATION

Despite normal glucose and electrolytes, prolonged high-intensity exercise causes lactate accumulation and acidosis beyond the muscle buffer system's capacity, leading to involuntary muscle cramps through disrupted calcium regulation in muscle fibers.

Test
Which neural pathway transmits pain and temperature sensation from the body to the brain?
A Dorsal column-medial lemniscus pathway
B Spinothalamic tract
C Corticospinal tract
D Rubrospinal tract
Correct Answer:  B. Spinothalamic tract
EXPLANATION

The spinothalamic tract carries pain and temperature information from the spinal cord to the thalamus and sensory cortex via crossed fibers.

Test
In a diabetic patient with hyperglycemia, which of the following best explains why glucose appears in urine?
A Glucose is actively secreted by collecting ducts
B Blood glucose exceeds the renal threshold for reabsorption
C The glomerular filtration barrier is damaged
D Insulin prevents glucose reabsorption
Correct Answer:  B. Blood glucose exceeds the renal threshold for reabsorption
EXPLANATION

Glucose is normally filtered and reabsorbed via active transport. When blood glucose exceeds ~180 mg/dL, the reabsorptive capacity is saturated, causing glycosuria.

Test
A researcher observes that blocking acetylcholinesterase leads to prolonged muscle contraction. This demonstrates that acetylcholinesterase's role is to:
A Synthesize acetylcholine
B Transport acetylcholine across the synapse
C Degrade acetylcholine after synaptic transmission
D Activate acetylcholine receptors
Correct Answer:  C. Degrade acetylcholine after synaptic transmission
EXPLANATION

Acetylcholinesterase breaks down acetylcholine in the synaptic cleft, terminating signal transmission; its inhibition causes acetylcholine accumulation and sustained contraction.

Test
A person injures their spinal cord at the cervical level. Which of the following would NOT be affected?
A Control of arm movement
B Control of leg movement
C Breathing
D Taste sensation
Correct Answer:  D. Taste sensation
EXPLANATION

Taste is mediated by cranial nerves (VII, IX, X) which are not affected by cervical spinal cord injury. Cervical injury affects arms, legs, and potentially breathing.

Test
Which of the following best explains oxygen-hemoglobin dissociation curve shift to the RIGHT?
A Increased pH and decreased temperature
B Decreased pH, increased temperature, and increased 2,3-DPG
C Increased pH and increased oxygen pressure
D Decreased carbon dioxide levels
Correct Answer:  B. Decreased pH, increased temperature, and increased 2,3-DPG
EXPLANATION

Right shift (Bohr effect) occurs with decreased pH, increased CO2, increased temperature, and elevated 2,3-DPG, facilitating oxygen release to tissues.

Test
A patient develops Cushing's syndrome due to excessive cortisol. Which feedback mechanism is disrupted?
A Positive feedback on CRH
B Negative feedback inhibition of CRH and ACTH
C Feedforward mechanism only
D No feedback regulation occurs
Correct Answer:  B. Negative feedback inhibition of CRH and ACTH
EXPLANATION

In Cushing's syndrome, elevated cortisol fails to inhibit CRH and ACTH secretion, disrupting the normal negative feedback loop of the HPA axis.

Test
Which mechanism explains how the kidney maintains blood pH around 7.35-7.45?
A Reabsorption of all filtered bicarbonate and secretion of H+ ions
B Production of ammonia buffer system only
C Excretion of all excess acid
D Secretion of bicarbonate ions
Correct Answer:  A. Reabsorption of all filtered bicarbonate and secretion of H+ ions
EXPLANATION

Kidneys reabsorb filtered HCO3- and secrete H+ ions, regulate ammonia production, and adjust acid-base balance through selective reabsorption and secretion.

Test
A patient with spinal cord injury at T5 level loses pain sensation below the waist. Which spinal tract is likely damaged?
A Dorsal column
B Spinothalamic tract
C Corticospinal tract
D Propriospinal fibers
Correct Answer:  B. Spinothalamic tract
EXPLANATION

The spinothalamic tract carries pain and temperature sensation, crossing at the spinal cord level. Damage results in contralateral loss of pain sensation below the injury.

Test
During maximal exercise, how do skeletal muscles maintain ATP availability despite increased consumption?
A Through anaerobic glycolysis and phosphocreatine breakdown
B Solely through aerobic oxidation of glucose
C By inhibiting ATP consumption in other tissues
D Through hepatic gluconeogenesis alone
Correct Answer:  A. Through anaerobic glycolysis and phosphocreatine breakdown
EXPLANATION

During intense exercise, muscles use phosphocreatine to rapidly regenerate ATP and switch to anaerobic glycolysis, producing lactate. Aerobic metabolism is insufficient initially.

Test
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