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

Simple two neuron reflex arc involves

  1. Sensory neuron

  2. Spinal cord

  3. Effector neuron

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

Reflex arc transmits the sensory information from receptor to effector via the spinal cord. It 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). 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). 

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

Route of reflex arc is

  1. Effectors, grey matter, motor fibres, sensory fibres and receptors

  2. Receptors, sensory fibres, grey matter and motor fibres

  3. Receptors, sensory fibres, grey matter, motor fibres and effectors

  4. Sensory fibres, grey matter, motor fibres, receptors and effectors
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A reflex arc follows a specific pathway: a receptor detects a stimulus, sensory neurons transmit the signal to the central nervous system (grey matter), motor neurons carry the response, and effectors perform the action. Option C correctly lists this sequence.

Multiple choice biology nervous system the reflex action reflex action and reflex arc basic reflex action and reflex arc
During reflex the sensory neurons do not pass directly to the brain.

  1. True

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

The path taken by the nerve impulses in a reflex is called as a reflex arc. In higher animals, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This characteristic allows reflex actions to occur relatively quickly by activating spinal motor neurons without the delay of routing signals through the brain, although the brain will receive sensory input while the reflex action occurs. 

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

Put the following parts of a reflex arc in the correct order beginning with the sensory receptor.
A. Motor neuron    B. Interneuron    C. Effector    D. Sensory neuron     E. Sensory receptor

  1. E, D, B, A, C

  2. E, D, A, B, C

  3. A, B, C, D, E

  4. A, E, D, B, C
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Most reflex arcs have five main components:  receptors, sensory neurons,interneurons, motor neurone and muscles.
Neurons have special proteins called receptors. Receptors respond to signals in the environment like pressure, pain, vibrations, light etc.
Sensory neurons have sensory receptors, they get activated by the signal from the environment. The activated sensory neurons extend into spinal cord sending an electrical signal to another neuron, the interneuron.
Interneuron then relays the signal to the motor neuron. Motor neuron run out of spinal cord and connect with the muscle or effector.
Thus the correct sequence is a sensory receptor, sensory neuron, interneuron, motor neuron and last effector.
Multiple choice biology nervous system the reflex action reflex action and reflex arc basic reflex action and reflex arc

In spite of the presence of complex neuron  networks, reflex arcs continue to be more efficient for quick responses.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The process of response to a peripheral nervous stimulation that occurs involuntarily, that I without conscious effort or thought and requires the involvement of a part of the central nervous system, is called a reflex action. These actions are very rapid, automatic, stereotyped behaviour or responses in which same kind of stimulus evokes a short-lived response. The stimulus is detected by sensory receptors present in the skin. These  initiate nerve impulses in the sensory or afferent neurons leading from them to the spinal cord. These impulses enter the spinal cord and initiate impulses in one or more interneurons. Interneurons initiate impulses in one or more motor or efferent neurons. The motor neurons then carry these impulses to the effectors or skeletal muscles in which response will be shown. This entire pathway from sensory receptor to sensory neuron to spinal cord (having interneurons) to motor neuron to effectors is called the reflex pathway or reflex arc.
So, the correct answer is 'True'.
Multiple choice biology nervous system the reflex action reflex action and reflex arc basic reflex action and reflex arc

Reflex arcs are formed in the 

  1. Brain

  2. Spinal cord

  3. Heart

  4. Eye
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The process of response to a peripheral nervous stimulation that occurs involuntarily, that I without conscious effort or thought and requires the involvement of a part of the central nervous system, is called a reflex action. These actions are very rapid, automatic, stereotyped behaviour or responses in which same kind of stimulus evokes a short-lived response. The stimulus is detected by sensory receptors present in the skin. These  initiate nerve impulses in the sensory or afferent neurons leading from them to the spinal cord. These impulses enter the spinal cord and initiate impulses in one or more interneurons. Interneurons initiate impulses in one or more motor or efferent neurons. The motor neurons then carry these impulses to the effectors or skeletal muscles in which response will be shown. This entire pathway from sensory receptor to sensory neuron to spinal cord (having interneurons) to motor neuron to effectors is called the reflex pathway or reflex arc. Therefore, reflex arc is formed in spinal cord.
So, the correct answer is 'Spinal cord'.
Multiple choice biology nervous system the reflex action reflex action and reflex arc basic reflex action and reflex arc

The components of a reflex arc are

  1. Sensory neuron, receptor, motor neuron

  2. Receptor, sensory neuron, center, motor neuron

  3. Receptor, sensory neuron, center, motor neuron, effector organ

  4. Motor neuron, sensory neuron, center, effector organ
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A reflex arc is a simple nervous pathway and consists of the sensory/afferent neuron, center (spinal cord), motor/efferent neuron and effector organ. The afferent/sensory neurons transmit the sensory information from sensory receptors to the spinal cord (sensory pathway). 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.

Therefore, 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

Which one of the following reflex do not include innervation of brain?

  1. Spinal reflex

  2. Cranial reflex

  3. Afferent reflex

  4. Efferent reflex
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Spinal reflexes are responses to stimuli arising from the  spinal cord. These responses are quick usually to protect the body from a dangerous situation.

For example- the withdrawal of the hand on touching a hot object
So, the correct answer is 'spinal reflex'

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

Which one of the following is the component of reflex arc?

  1. Sensory neuron

  2. Brain

  3. Motor neuron

  4. Both A and C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A reflex arc is a simple nervous pathway and consists of a sensory/afferent neuron, center (spinal cord), motor/efferent neuron and effector organ. The afferent/sensory neurons transmit the sensory information from sensory receptors to the spinal cord (sensory pathway). 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. The brain is not the part of the reflex arc. 

Therefore, the correct answer is option D.