All Free Biology MCQs with Answers

• A. Nociceptors respond to pressure
• B. Meissner's corpuscles are thermoreceptors
• C. Photoreceptors are depolarized in darkness and hyperpolarized in light
• D. Receptors do not produce graded potentials

Explanation: In the dark, photoreceptors remain depolarized; light causes hyperpolarization, reducing neurotransmitter release.

• A. Adrenaline
• B. Thyroid stimulating hormone (TSH)
• C. FSH (Follicle-stimulating hormone)
• D. Antidiuretic hormone (ADH)

Explanation: The posterior lobe of the pituitary gland produces two hormones, vasopressin (Antidiuretic hormone) and oxytocin.

• A. Digestion of food
• B. Heart beat
• C. Contraction of pupil of eye
• D. Thought
• E. Breathing rate

Explanation: The autonomic nervous system does not directly control thought processes.

• A. Brain
• B. Central nervous system
• C. Peripheral nervous system
• D. Somatic nervous system

Explanation: The explanation for this question is as follows: The CNS consists of the brain and the spinal cord, which are both protected in three…

• A. Syphilis is caused by a virus
• B. Syphilis affects the eyes, bones, joints, and CNS
• C. Genital herpes produces genital sores and ulcers
• D. Gonorrhea is caused by a gram-negative bacterium

Explanation: The correct answer is that 'Syphilis is caused by a virus,' which is incorrect because syphilis is actually caused by a bacterium…

• A. Spinal cord, axon, vertebra
• B. Cerebrum, cerebellum, pons
• C. Medula, pons, midbrain
• D. Thalamus, midbrain, pons

Explanation: This is the correct option. The correct composition of the brain stem is "Medulla, Pons, Midbrain."

• A. Hair end organs
• B. Pacinian corpuscles
• C. Meissner's Corpuscles
• D. All of these options are correct

Explanation: Meissner's corpuscles respond to touch and low-frequency vibration. Ruffini endings detect stretch, deformation within joints, and warmth.

• A. Monosynaptic reflex
• B. Blood and water
• C. Hemi Synaptic Reflex
• D. Blood and fluid

Explanation: The patellar reflex (also known as the knee-jerk reflex) and the Achilles reflex (also called the ankle reflex) are examples of "a)…

• A. It is voluntary
• B. It is involuntary
• C. It is found in higher animals
• D. It helps in protection from hot objects

Explanation: The statement "It is voluntary" is not true for reflex action. All the other options are true.

• A. Glucagon
• B. Epinephrine
• C. Thyroxin
• D. Estrogen

Explanation: Estrogen is a steroid hormone that plays a crucial role in the development and regulation of the female reproductive system.

• A. Carbohydrates
• B. Proteins
• C. Steroids
• D. Both B and C

Explanation: Option D is correct. Chemically, hormones are classified into two main types: Protein hormones.

• A. Class Fish
• B. Class Amphibian
• C. Class Reptilia
• D. Class Mammalia

Explanation: Negative feedback mechanisms are a characteristic of Class Mammalia. A negative feedback mechanism is a regulatory process where the…

• A. Gamma-aminobutyric acid (GABA)
• B. Glutamate
• C. Acetylcholine
• D. Dopamine

Explanation: GABA, or gamma-aminobutyric acid, is the primary inhibitory neurotransmitter in the central nervous system, responsible for reducing…

• A. Pituitary
• B. Adrenal
• C. Thyroid
• D. Parathyroid
• E. Pancreas

Explanation: The adrenal gland located at the top of the kidneys is involved in the release of adrenaline which is an emergency in flight-or-fight…

• A. Option A
• B. Option B
• C. Option C
• D. Option D
• E. Option E

Explanation: The figure is not given in the question. The first label part is the thalamus, the second part is the cerebellum, and the third part is…

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Explanation: Sensory neuron function to carry the sensory information to the CNS. Interneurons transfer impulses from sensory to motor neuron remaining…

• A. Transmission by the nervous system is short-lived, whereas transmission by the hormonal system is long-lasting.
• B. The nervous system uses electrical impulses to send signals through neurons, whereas the hormonal coordination uses chemical messengers transported in the blood.
• C. Responses are often permanent in the hormonal system but temporary and reversible in the nervous system.
• D. In the nervous system secretory chemicals are released in blood while in the hormonal system; secretory chemicals are released in extracellular fluids.

Explanation: D statement is wrong because in the nervous system the secretory chemicals are not released in the blood they are released on another…

• A. Exchanged with sodium ions through co-transport channels at axon surfaces during the reestablishment of a resting potential after an action potential.
• B. Moved in by diffusion through gated ion channels in pre-synaptic membranes of excitatory neurones causing vesicles to move to pre-synaptic membrane as an impulse arrives.
• C. Exchanged with chloride ions at the post-synaptic membrane, in changing membrane potential in inhibitory neurones.
• D. Actively pumped out of axons at nodes of Ranvier of myelinated neurones, being the main cause of the potential difference that is maintained during the resting potential.

Explanation: The arrival of an impulse at the synaptic knob causes gated Ca2+ channels in the presynaptic membrane to open.

• A. Repolarization
• B. Sodium ions forming an ionic bonding
• C. The opening of sodium channels/gates
• D. The action of the acetylcholinesterase enzyme

Explanation: Option A mentions repolarization, which is the stage where there is a large influx of potassium ions out from the cell, during which…

• A. Syphilis is caused by virus
• B. Syphilis affects eyes, bones, joints, CNS
• C. Genital herpes produces genital soreness and ulcers
• D. Gonorrhea is caused by gram positive bacterium

Explanation: The statement Syphilis is caused by a virus is incorrect. Syphilis is caused by a spirochete bacterium called Treponema pallidum.