96 past paper MCQs on Neurons, from the Coordination and Control unit of MDCAT Biology. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.
1.The neurotransmitter active outside the central nervous system is: (MDCAT 2022)
Correct answer: (a) acetylcholine
Acetylcholine works at the neuromuscular junction and in the autonomic nervous system.
2.The chemical messengers that transmit an action potential across a synapse are: (MDCAT 2023)
Correct answer: (c) neurotransmitters
The vesicles of the synaptic knob release a neurotransmitter across the cleft.
3.During the resting membrane potential of a neuron: (MDCAT 2023)
Correct answer: (a) the outer surface is positive and the inner surface negative
The sodium-potassium pump and the potassium leak leave the inside about $-70$ mV with respect to the outside.
4.In a typical nerve, the action potential duration is: (MDCAT 2023)
Correct answer: (a) 1 millisecond
Depolarization and repolarization together take about a millisecond.
5.In human myelinated fibres a nerve impulse travels at how many metres per second? (MDCAT 2024)
Correct answer: (a) 100-120
Saltatory conduction along a myelinated fibre reaches about $100$-$120\ \mathrm{m\,s^{-1}}$.
6.Nissl's granules are groups of: (MDCAT 2024)
Correct answer: (c) ribosomes
They are stacks of rough endoplasmic reticulum with their ribosomes in the cell body of a neuron.
7.During the non-conducting state, the neuron membrane is permeable to the efflux of: (MDCAT 2024)
Correct answer: (a) $\mathrm{K^+}$
At rest the membrane leaks potassium outwards, which is what leaves the inside negative.
8.Which of the following neurotransmitters lies outside the central nervous system? (MDCAT 2024)
Correct answer: (a) acetylcholine
Acetylcholine is the transmitter at the neuromuscular junction and in the autonomic ganglia.
9.Depolarization during the conduction of a nerve impulse is due to: (MDCAT 2024)
Correct answer: (a) inward movement of $\mathrm{Na^+}$
The sodium gates open and sodium floods in, reversing the sign of the membrane potential.
10.Which component of a reflex arc connects the sensory neuron to the motor neuron within the spinal cord? (UHS MDCAT 2025)
Correct answer: (d) Associative neuron
The associative (inter) neuron of the spinal cord is the link between the sensory and the motor neuron.
11.Nissls granule is a specialized structure in neuron formed by modification of : (UHS MDCAT 2025)
Correct answer: (d) Ribosome & Rough ER
Nissl granules are stacks of rough endoplasmic reticulum studded with ribosomes.
12.Which of the following is the correct pathway of nerve Impulse? (UHS MDCAT 2025)
Correct answer: (a) Receptors--> CNS--> Effectors
A receptor picks up the stimulus, the central nervous system decides, and the effector acts.
13.The neurotransmitters are secreted by the neuron from: (UHS MDCAT 2025)
Correct answer: (a) Axon ends
The vesicles of neurotransmitter lie in the synaptic knobs at the axon endings.
14.Which part of the neuron typically receives incoming signals from other neurons? (UHS MDCAT 2025)
Correct answer: (b) Dendrites
Dendrites are the branched processes that carry impulses towards the cell body.
15.Which of the following cells possess Nissl's granules? (UHS MDCAT 2025)
Correct answer: (a) Nerve cells
Nissl granules are found only in neurons, where they mark the rough endoplasmic reticulum.
16.Which type of neurons stimulate muscles to contract In a reflex arc? (UHS MDCAT 2025)
Correct answer: (a) Motor neurons
The motor neuron is the one that carries the impulse out to the effector muscle.
17.The junction between two consecutive neurons where information is transmitted from one neuron to the next is called: (KMU MDCAT 2025)
Correct answer: (b) Synapse
The gap between two neurons, crossed by a neurotransmitter, is the synapse.
18.Which ion is tenfold higher in concentration outside the membrane of neuron during resting potential? (KMU MDCAT 2025)
Correct answer: (b) Sodium
The pump keeps sodium about ten times more concentrated outside the resting neuron.
19.Touching a sharp object stimulates pain receptors. This information is carried to the central nervous system by the: (KMU MDCAT 2025)
Correct answer: (b) Sensory neuron
A sensory neuron carries the impulse from the receptor in to the central nervous system.
20.The state, when a neuron is NOT conducting an impulse during resting membrane potential is called; (KMU MDCAT 2025)
Correct answer: (a) Polarized
A resting neuron is polarized, negative inside and positive outside.
21.Which of the following waves travel along a neuron during nerve impulse conduction? (KMU MDCAT 2025)
Correct answer: (d) Electrochemical waves
The impulse is a wave of depolarization carried by ion movement, so it is electrochemical.
22.The CORRECT sequence of events in a reflex arc is: (KMU MDCAT 2025)
Correct answer: (c) Receptor, sensory neuron, associative neuron, motor neuron, effector
A reflex runs receptor, sensory neuron, associative neuron, motor neuron, effector.
23.Which one is the correct direction of action potential along the neuron? (NUMS MDCAT 2025)
Correct answer: (a) Axon → post synaptic terminal
The impulse runs down the axon to the synaptic terminal at its end.
24.Concentration of Na+ and K+ ions during resting membrane potential is: (Inside Neuron / Outside Neuron) (NUMS MDCAT 2025)
Correct answer: (b) K+ 10 times / Na+ 30 times
The pump keeps potassium about ten times higher inside and sodium about thirty times higher outside.
25.A brief phase in which neuron regains its original ionic distribution and polarity is called: (NUMS MDCAT 2025)
Correct answer: (d) Refractory period
During the refractory period the fibre restores its ionic gradient and will not carry another impulse.
26.Ions involved in synaptic transmission of nerve impulse: (NUMS MDCAT 2025)
Correct answer: (c) Na+, Ca2+
Calcium entering the terminal releases the transmitter, and sodium carries the impulse in the next fibre.
27.Correct sequence of the four elements of a neural pathway in simple-reflex circuit: (NUMS MDCAT 2025)
Correct answer: (a) Sensory neuron → associative neuron → motor neuron → muscles
A reflex runs sensory neuron, associative neuron, motor neuron, muscle.
28.Automatic and rapid actions that do not involve the conscious part of brain is: (SIBA MDCAT 2025)
Correct answer: (a) Reflex actions
A reflex is completed through the spinal cord, without waiting on the conscious brain.
29.Which of the following neurons conduct impulses from sensory receptors to CNS: (SIBA MDCAT 2025)
Correct answer: (a) Sensory neurons
Sensory, or afferent, neurons carry the impulse in from the receptor.
30.A doctor taps below the knee and the leg kicks forward. What does this show? (SIBA MDCAT 2025)
Correct answer: (c) An involuntary reflex to external stimuli
The knee jerk is a spinal reflex, involuntary and needing no decision from the brain.
31.Which type of change is a nerve impulse? (SIBA MDCAT 2025)
Correct answer: (c) Electrical and chemical change
The impulse is electrical along the fibre and chemical across the synapse.
32.The outer surface of the axon membrane in a resting neuron is: (SIBA MDCAT 2025)
Correct answer: (b) Positive due to sodium ions
The pump drives sodium out, so the outside of the resting membrane is positive.
33.Which of the following best describes the direction of impulse traveling in a typical neuron? (SIBA MDCAT 2025)
Correct answer: (b) Dendrite ..... cell body ..... axon
The impulse comes in over the dendrites, passes the cell body and leaves along the axon.
34.Myelin sheath acts as; (SZABMU MDCAT 2025)
Correct answer: (b) Insulator
The myelin sheath insulates the fibre, so the impulse jumps from node to node.
35.Nodes of Ranvier along the length of axons fibers allow: (SZABMU MDCAT 2025)
Correct answer: (b) Saltatory conduction of nerve impulse
The impulse leaps from node to node, which is saltatory conduction.
36.In human myelinated fibers nerve impulse travels at _____ meters per second. (UHS MDCAT 2024)
Correct answer: (a) 100-120
Saltatory conduction along a myelinated fibre reaches about $100$ to $120\,\mathrm{m\,s^{-1}}$.
37.During non-conducting state, the neuron membrane is permeable to efflux of (UHS MDCAT 2024)
Correct answer: (a) K+
The resting membrane leaks potassium outwards far more readily than it leaks sodium in.
38.Which of the following neurotransmitters is lying outside the central nervous system? (UHS MDCAT 2024)
Correct answer: (a) Acetylcholine
Acetylcholine is the transmitter of the neuromuscular junction and of the autonomic ganglia.
39.Depolarization during conduction of nerve impulse is due to (UHS MDCAT 2024)
Correct answer: (a) Inward movement of Na+
Sodium rushing in reverses the charge across the membrane.
40.Which of the following is NOT a feature of Autonomic Nervous System? (UHS MDCAT 2024)
Correct answer: (b) Regulate response of skeletal muscles
The autonomic system serves smooth muscle, cardiac muscle and glands; skeletal muscle is voluntary.
41.The following function/activity is NOT controlled by the autonomic nervous system. (KMU MDCAT 2024)
Correct answer: (d) Thoughts and emotions
The autonomic system serves the viscera; thought and emotion belong to the cerebrum.
42.A motor neuron: (KMU MDCAT 2024)
Correct answer: (c) Carries impulse from CNS to muscles
A motor neuron carries the impulse out from the central nervous system to the effector.
43.Diffusion _______ across the post synaptic membrane causes it to depolarise: (KMU MDCAT 2024)
Correct answer: (d) Sodium ions
The transmitter opens sodium channels, and the inrush of sodium depolarizes the membrane.
44.A reflex action, does not involve the: (KMU MDCAT 2024)
Correct answer: (a) Brain
A spinal reflex is completed in the cord; the brain learns of it only afterwards.
45.The neurotransmitter________ is hydrolysed by monoamine oxidase (KMU MDCAT 2024)
Correct answer: (b) Adrenaline
Monoamine oxidase breaks down the catecholamines, of which adrenaline is one.
46.Most of the neurons in the CNS are? (KMU MDCAT 2024)
Correct answer: (b) Multipolar
Most neurons of the central nervous system have many dendrites and one axon, so they are multipolar.
47.What is the fate of a neurotransmitter after the transmission of nerve impulse across synapse? (NUMS MDCAT 2024)
Correct answer: (d) Broken down by enzymes
An enzyme in the cleft breaks the transmitter down at once, so the signal does not linger.
48.Which immediate change is brought about in the post synaptic membrane on binding with excitatory neurotransmitter? (NUMS MDCAT 2024)
Correct answer: (b) Sodium gates open
The transmitter opens sodium gates, and the inrush begins to depolarize the membrane.
49.During the conduction of nerve impulse, hyperpolarization would not occur if: (NUMS MDCAT 2024)
Correct answer: (b) Potassium gates were not so lousy
The potassium gates are slow to shut, so too much potassium leaves and the inside goes past its resting value.
50.Which of the following is a characteristic of electrical synapse? (NUMS MDCAT 2024)
Correct answer: (d) Absence of neurotransmitter
An electrical synapse passes the current directly through gap junctions, with no transmitter at all.
51.Which option given below characterizes refractory period? (NUMS MDCAT 2024)
Correct answer: (a) Reversal of charges across neural membrane
During the refractory period the membrane is restoring its charges and cannot carry another impulse.
52.There is no clear difference between dendrites and axons in sensory neurons, except: (UHS MDCAT 2023)
Correct answer: (b) Length
In a sensory neuron both processes look alike, and only their length tells them apart.
53.The neurotransmitter active outside the CNS (Central Nervous System) is: (UHS MDCAT 2023)
Correct answer: (a) Acetylcholine
Acetylcholine works at the neuromuscular junction and in the autonomic ganglia, outside the brain and cord.
54.Which axon would transmit an action potential most rapidly? (SZABMU MDCAT 2023)
Correct answer: (d) 2mm diameter neuron with myelin
Speed rises with the diameter of the fibre and again with myelination, so the thick myelinated axon is fastest.
55.In neurons, the message istransmitted across synapse in the form of chemical messenger called: (SZABMU MDCAT 2023)
Correct answer: (b) Neurotransmitter
The chemical released into the synaptic cleft is the neurotransmitter.
56.Microscopic gap between the two neurons is called: (SZABMU MDCAT 2023)
Correct answer: (b) Synapse
The gap between two neurons is the synapse.
57.In a reflex arc, the cell body of sensory neuron is located in: (SZABMU MDCAT 2023)
Correct answer: (d) Dorsal root ganglion
The cell body of a sensory neuron sits in the dorsal root ganglion, outside the cord.
58.Na+ (sodium ions) are nearly ________ times greater in fluid outside the cell than inside: (NUMS MDCAT 2023)
Correct answer: (a) 10
The sodium pump keeps sodium about ten times more concentrated outside the resting cell.
59.The site of production of neurotransmitters is: (NUMS MDCAT 2023)
Correct answer: (b) Presynaptic neuron
The transmitter is made in the presynaptic neuron and stored in the vesicles of its knobs.
60.Endorphins are produced in: (NUMS MDCAT 2023)
Correct answer: (a) Brain
Endorphins are made in the brain and act as its own painkillers.
61.The junction between two neurons is: (NUMS MDCAT 2023)
Correct answer: (b) Synapse
The junction between two neurons is the synapse.
62.During testing membrane potential condition: (UHS MDCAT 2023)
Correct answer: (a) Outer suite of neuron is more positive
The pump drives sodium out, so the outside of the resting membrane is positive.
63.The chemical Messengers that transmit action potential across the synapse in the form of chemicals are? (UHS MDCAT 2023)
Correct answer: (c) Neurotransmitters
Those chemicals are the neurotransmitters.
64.In which part of the nervous system will you find Schwann cells? (PMC MDCAT 2022)
Correct answer: (b) Peripheral nervous system
Schwann cells make the myelin of the peripheral nerves.
65.Neurilemma cells are also known as? (PMC MDCAT 2022)
Correct answer: (d) Schwann cells
The neurilemma is the sheath of Schwann cells round a peripheral fibre.
66.Which of these compounds generates a feeling of well-being and inhibits the sensation of pain? (PMC MDCAT 2022)
Correct answer: (c) Endorphin
Endorphins are the brain’s own opiates.
67.Which of the following types of neurons has a single long dendron? (PMC MDCAT 2022)
Correct answer: (a) Sensory neuron
A sensory neuron has one long dendron running in from the receptor.
68.The components of coordinated action (PMC MDCAT 2022)
Correct answer: (d) Receptors, neurons & effectors
A coordinated action needs a receptor to sense, neurons to carry and an effector to act.
69.What is the change in the resting potential when a neuron fires a nerve impulse? (PMC MDCAT 2022)
Correct answer: (b) It becomes more positive moving from the cell body to the axon
Sodium rushing in reverses the charge, so the inside becomes positive as the impulse passes.
70.When a neuron’s membrane potentials is between – 70 mV and – 90 mV, it is said to be In a state of: (PMC MDCAT 2022)
Correct answer: (b) hyperpolarization
A membrane more negative than its resting value is hyperpolarized.
71.An automatic, involuntary response to any change, external or internal is called: (NUMS MDCAT 2022)
Correct answer: (a) Reflex
An automatic involuntary response to a stimulus is a reflex.
72.Resting membrane potential measures: (NUMS MDCAT 2022)
Correct answer: (a) -70 mv
The resting potential of a neuron is about $-70\,\mathrm{mV}$.
73.The gap between neurons at a synapse is: (NUMS MDCAT 2022)
Correct answer: (b) Synaptic cleft
The gap between the two membranes at a synapse is the synaptic cleft.
74.A long extension of a nerve cell is called: (NUMS MDCAT 2022)
Correct answer: (a) Axon
The axon is the long process that carries the impulse away.
75.The molecules responsible for conveying messages from one neuron to the next are called: (NUMS MDCAT 2022)
Correct answer: (c) Neurotransmitters
Those molecules are the neurotransmitters.
76.A single motor neuron may innervate as few as 3-5 fibers in muscles of: (PMC Practice 2021)
Correct answer: (c) Eyes
The finer the control needed, the fewer fibres in a motor unit, and the eye muscles are the finest of all.
77.Most reflex arcsare: (PMC Practice 2021)
Correct answer: (b) Polysynaptic reflex
Most reflexes have an associative neuron between the sensory and the motor one, so they are polysynaptic.
78.The spinal cord is part of: (PMC Practice 2021)
Correct answer: (b) Central nervous system
The brain and the spinal cord together are the central nervous system.
79.A neural pathway that controls an action reflex is called: (PMC Practice 2021)
Correct answer: (b) Reflex arc
The path from receptor through the cord to the effector is the reflex arc.
80.What is a typical value for the resting membrane potential of a neuron? (PMC Practice 2021)
Correct answer: (a) -70 mV
The resting potential is about $-70\,\mathrm{mV}$.
81.Which of the following is an example of superficial reflexes? (PMC Practice 2021)
Correct answer: (c) Abdominal reflex
Stroking the abdominal skin brings a superficial reflex; the knee and ankle jerks are deep tendon reflexes.
82.Which of the following neurotransmitters function, both as neurotransmitter and hormones, decreasing our perception of pain? (PMC MDCAT 2020)
Correct answer: (d) Endorphins
Endorphins are the brain’s own opiates and damp down the sense of pain.
83.Which one of the following is common to all neurons? (PMC MDCAT 2020)
Correct answer: (a) A cell body which contains a nucleus
Every neuron has a cell body with a nucleus; myelin, nodes and Schwann cells belong only to some.
84.Neurons are cells adapted for the rapid transmission of electrical impulses. To do this, they have long thin processes called: (PMC MDCAT 2020)
Correct answer: (a) Axons
The long process that carries the impulse away is the axon.
85.A _____ is a junction between two neurons or between a motor neuron and a muscle cell: (PMC MDCAT 2020)
Correct answer: (b) Synapse
That junction is the synapse.
86.If stimulation is above ______, impulses travel to the brain along the sensory neuron. (UHS MDCAT 2019)
Correct answer: (d) Threshold potential
A stimulus below the threshold sets off nothing; above it the impulse is full sized.
87.In an action potential, the permeability of sodium ions in the neurons increases due to; (UHS MDCAT 2019)
Correct answer: (c) The opening of sodium channels/gates
The sodium gates open and sodium rushes in down its gradient.
88.The reflex action is the phenomena which only involves: (UHS MDCAT 2019)
Correct answer: (b) receptors, effectors, and spinal cord
A spinal reflex needs only the receptor, the cord and the effector; the brain learns of it afterwards.
89.Acetylcholine and Noradrenaline are two types of ______ used in our nervous system: (UHS MDCAT 2019)
Correct answer: (c) Neurotransmitters
Both are neurotransmitters, acetylcholine in the parasympathetic and noradrenaline in the sympathetic system.
90.The main neurotransmitter for synapses is ______, which lie outside the central nervous system. (UHS MDCAT 2019)
Correct answer: (a) Acetylcholine
Acetylcholine is the transmitter of the neuromuscular junction and the autonomic ganglia.
91.How many sodium ions are pumped out in response to two potassium ions transported into the membrane? (UHS MDCAT 2018)
Correct answer: (b) 3
The pump drives three sodium ions out for every two potassium ions in.
92.When a nerve impulse jumps from one node of Ranvier to the next in a myelinated neuron, it’s called __________. (UHS MDCAT 2018)
Correct answer: (b) Saltatory conduction
The impulse jumps from node to node, which is saltatory conduction.
93.In the nervous system chemical messengers are called ______. (UHS MDCAT 2018)
Correct answer: (a) Neurotransmitters
The chemicals that cross a synapse are the neurotransmitters.
94.Name the structures which produce response: (UHS MDCAT 2017)
Correct answer: (d) Effectors
The muscle or gland that carries out the response is the effector.
95.Neurotransmitter secreted at synapse outside the central nervous system is: (UHS MDCAT 2015)
Correct answer: (d) Acetylcholine
Acetylcholine is the transmitter of the neuromuscular junction and the autonomic ganglia.
96.Conduction of action potentials from one mode of Ranvier to another in myelinated neurons is through: (UHS MDCAT 2015)
Correct answer: (d) Saltatory Conduction
The impulse leaps from node to node, which is saltatory conduction.