Biology

Nervous System and Neurons

1,224 Questions

The nervous system and neurons section covers the structural and functional aspects of the human nervous system. Topics include nerve fibers, the myelin sheath, and sympathetic nervous system functions. This material is crucial for general science preparation in various competitive exams.

Neuron structureMyelin sheath productionSympathetic nervous systemCranial and spinal nervesParasympathetic functions

Nervous System and Neurons Questions

Multiple choice biology control and co-ordination in plants and animals voluntary and involuntary movements impulse and its transmission coordination in human beings- nervous control

The rate at which a nerve impulse travels along a nerve fiber is dependent up on 

  1. Length of the nerve fibre

  2. Diameter of the nerve fibre

  3. Presence of connective tissue sheath

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Increased axon diameter in axons leads to increase action potential velocity. As there is an increase in diameter of a fibre, its internal resistance decreases. The internal resistance decreases faster relative to the membrane resistance - therefore the distance the membrane potential can travel is increased by an increased diameter. So, the correct answer is option B.

Multiple choice biology control and co-ordination in plants and animals voluntary and involuntary movements impulse and its transmission coordination in human beings- nervous control

If myelin sheath is continued in myelinated nerve fibre then what will happen in a neuronal conduction?

  1. Velocity will be increased.

  2. Conduction will be slow.

  3. Conduction will be stopped.

  4. No effect is seen.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Myelin is an insulating layer or sheath, that forms around nerves, including those in the brain and spinal cord. It is made up of protein and fatty substances. The purpose of the myelin sheath is to allow electrical impulses to transmit quickly and efficiently along the nerve cells. Nerve impulses cannot pass through the myelination, so they jump from one node of Ranvier to the next. If the whole nerve becomes myelinated then the conduction will be stopped.

Multiple choice biology control and co-ordination in plants and animals voluntary and involuntary movements impulse and its transmission coordination in human beings- nervous control
The speed of nerve impulse depends on the diameter of the axon.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The speed with which the nerve impulse is conducted by axon is known as nerve conduction velocity. The speed of nerve conduction does not depend on the diameter of axon only rather it depends on the diameter of the nerve fibre. The diameter of nerve fibre is axon, neurilemma, and myelin sheath in myelinated axons while axon and neurilemma in unmyelinated fibre. Conduction velocity is high in myelinated nerve fibre with the greater diameter. So, the given statement is false.

Multiple choice biology control and co-ordination in plants and animals voluntary and involuntary movements impulse and its transmission coordination in human beings- nervous control

The propagation of a nerve impulse is due to changes in the permeability of the nerve cell membrane that allow for a voltage difference across the membrane.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Neurons send messages through electrical impulses called as nerve impulses. The nerve impulse is due to the changes occurring across the cell membrane. Cell membranes contain a sodium-potassium pump. The concentration of sodium and potassium ions is different across the membrane. This difference causes a voltage difference between the inside of the neuron and its surroundings. This is called as the resting membrane potential. The membrane potential is always negative inside the cell. The sodium and potassium channels in the cells are voltage-gated, meaning they can open and close depending on the voltage across the membrane. During action potential, permeability of the nerve cell membrane changes for both sodium and potassium ions. During depolarization, there is influx of sodium ions which makes inside of the cell positive. Depolarization is followed by repolarization during which the outflux of potassium ions takes place which makes inside of the cell negative. The whole process results in the propagation of a nerve impulse.

Thus, the correct answer is option A.

Multiple choice biology structural organization of animals structural organization of rabbit structural organization of leech phylum annelida

Two extra cranial nerves found in rabbit/human are

  1. Hypoglossal and spinalaccessory

  2. Hypoglossal and pneumogastric

  3. Spinal accessory and glossopharyngeal

  4. Hypoglossal and glossopharyngeal
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

While many vertebrates have 10 pairs of cranial nerves, mammals (including rabbits and humans) possess 12 pairs. The two additional pairs are the hypoglossal (XII) and the spinal accessory (XI).

Multiple choice zoology neural control and coordination parts of the brain brain and its parts brain

Anaesthetics reduce pain by blocking nerve conduction due to

  1. Blocking neurotransmitter receptors
  2. Blocking N$a^+$ channels
  3. Blocking $K^+$ channels

  4. All the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Local anaesthetics work primarily by binding to and blocking voltage-gated sodium channels in nerve cell membranes, which prevents the depolarization required for nerve impulse conduction.

Multiple choice how humans hear sound human ear study of sound sound physics

What stimulates the auditory nerve?

  1. the movement of the three ear ossicles

  2. the movement of stirrup

  3. the movement of fluid in the cochlea

  4. all
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cochlea is a coiled and fluid filled tube having sense of hearing. The movement of the fluid in the cochlea due to the vibrations stimulates the auditory nerve .

Multiple choice how humans hear sound human ear study of sound sound physics

What stimulates the auditory nerve?

  1. The movement of the three ear ossicles

  2. The movement of stirrup

  3. The movement of fluid in the cochlea

  4. All of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cochlea is a coiled and fluid filled tube having sense of hearing.the movement of the fluid in the cochlea due to the vibrations stimulates the auditory nerve.

Multiple choice biology biodiversity and its classifications life introduction to plant kingdom classification of organisms

Nerve cord is in ............ position in invertebrates.

  1. Dorsal

  2. Lateral

  3. Ventral

  4. Absent
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The ventral nerve cord is a bundle of nerve fibers, typically a solid double strand (pair) of nerve cords, that runs along the longitudinal axis of some phyla of elongate invertebrates, and forms part of the invertebrate central nervous system. In most cases, this nerve cords runs ventrally, below the gut, and connects to the cerebral ganglia. Among the phyla exhibiting ventral nerve cords are nematodes (roundworms), annelids (such as earthworms, and arthropods (such as insects and crayfish).
The ventral nerve cord usually consists of a pair of partially fused nerve trunks running longitudinally along the ventral plane of the animals, from the anterior to posterior (the thoracic and abdominal tagma in the arthropods).

So, the correct answer is option A.

Multiple choice biology the age of adolescence changes in body during adolescence hormone during puberty role of hormones in reproduction

The homeostatic regulation of an animal requires three basic components, ________ to detect changes, ________ to evaluate the changes and _______ to adjust the changes respectively.

  1. Receptors, control center, effectors

  2. Brain, spinal cord, effectors

  3. Receptors, integrators, effectors

  4. Receptors, effectors, integrators
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Homeostatic regulation involves receptors (detecting stimuli), a control center (evaluating information), and effectors (executing the response to restore balance).

Multiple choice zoology the endocrine system adrenal gland thymus and adrenal gland adrenal glands

The sympathetic nervous system is responsible for the fight-or-flight response in humans. One neurotransmitter involved in this response is epinephrine. This excitatory molecule increases blood glucose by signaling the conversion of pyruvate into glucose.
Identify a potential target receptor cell of epinephrine in the fight-or-flight response.

  1. Liver cells.

  2. Cells in the pancreas that produce insulin.

  3. There is a specific target cell since epinephrine will work on all cells in the body and only cause a response in cells with intracellular receptors.

  4. Lung cells.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Liver cells contain glucose stored in the form of glycogen (glucagon enzyme), which is converted to glucose and released in the blood stream to provide muscle cells and brain with the required energy to respond to the stimulus instantaneously during a fight-or -flight response.

So, epinephrine should have receptors sites on liver cells or adipose cells which store energy molecules
So, the correct answer is 'Liver cells'

Multiple choice biology nervous system the reflex action reflex action and reflex arc basic reflex action and reflex arc

Reflex arc is formed by 

  1. Receptor - brain - muscles

  2. Muscles - spinal cord - receptor

  3. Receptor - spinal cord - muscles

  4. Muscle - brain - receptor
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The reflex arc is a simple nervous pathway and consists of the sensory receptor, afferent neuron, centre, efferent neuron and effector organ. The afferent/sensory neurons transmit the sensory information from sensory receptors to the spinal cord (sensory pathway). Reflex arc starts with sensory receptors, not with muscles. The interneurons of spinal cord integrate the incoming information and signal is relayed to motor/efferent neurons.  The motor pathway transmits the signal from motor neurons to the effector organs (muscles and glands etc). Thus, reflex arc transmits the information from receptor to effector via the spinal cord which. The brain is not the part of reflex arc. Thus, the correct answer is option C.

Multiple choice biology nervous system the reflex action reflex action and reflex arc basic reflex action and reflex arc

The sequence of a reflex arc is

  1. Receptor $\rightarrow$ Sensory neuron $\rightarrow$ Motor neuron $\rightarrow$ Effector $\rightarrow$ Response
  2. Effector $\rightarrow$ Sensory neuron $\rightarrow$ Motor neuron $\rightarrow$ Receptor $\rightarrow$ Response
  3. Effector $\rightarrow$ Motor Neuron $\rightarrow$ Interneuron $\rightarrow$ Receptor $\rightarrow$ Response
  4. Receptor $\rightarrow$ Motor neuron $\rightarrow$ Sensory neuron $\rightarrow$ Effector $\rightarrow$ Response
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Reflex arc transmits the sensory information from receptor to effector via spinal cord. It consists of sensory receptor, afferent (sensory) neuron, centre, efferent (motor) neuron and effector organ. The afferent/sensory neurons transmit the sensory information from sensory receptors to spinal cord (sensory pathway). Detection of environmental stimulus by receptors forms the first step of reflex arc. 

Sensory neurons receive the information from receptors while motor neurons transmit the nerve impulses from CNS to effectors (muscles and glands). 
The interneurons of spinal cord integrate the incoming information and signal is relayed to motor/efferent neurons.  The motor pathway transmits the signal from motor neurons to the effector organs (muscles and glands etc). The effector organs respond according to the information carried by motor pathway.
Therefore, the correct answer is option A.

Multiple choice biology nervous system the reflex action reflex action and reflex arc basic reflex action and reflex arc

The reflex arcs in which one or more interneurons connect the afferent and efferent signals are

  1. Autonomic reflex

  2. Somatic reflex

  3. Monosynaptic reflex

  4. Polysynaptic reflex
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

  • Monosynaptic reflex is a type of reflex in which the reflex arc consists of only two neurons, one sensory neuron, and one motor neuron. Monosynaptic refers to the presence of a single chemical synapse. 
  • By contrast, in polysynaptic reflex arcs, more than one relay neurons connect the sensory and motor neuron. 
  • Polysynaptic reflex or spinal reflex or withdrawal reflex protects the body from the damaging stimulus. It is located in the spinal cord. 

Therefore, the correct answer is option D.