Tag: reflex action and reflex arc

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Multiple choice zoology control and coordination in living organisms the reflex action reflex action and reflex arc basic reflex action and reflex arc

A sleeping cat suddenly gets up and chases a rat. The movement involved is similar to

  1. the movement of train on green signal

  2. the movement of the football when kicked by the player

  3. the ringing of alarm when the correct time is reached

  4. the movement of eyelids when something falls into the eye.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A sleeping cat suddenly gets up and chases a rat. The movement involved is similar to the movement of train on green signal, because it is involuntary action.

So, the correct option is ‘the movement of train on green signal’.

Multiple choice zoology control and coordination in living organisms the reflex action reflex action and reflex arc basic reflex action and reflex arc

Which of the following is an incorrect pair?

i. Effector organ of somatic reflex- Skeletal muscles
ii. Receptor organ of somatic reflex- Smooth muscles
iii. Effector organ of visceral reflex- Skin
iv. Receptor organ of visceral reflex- Epithelial lining of the gut

  1. (i) and (iii)

  2. (ii) and (iii)

  3. All of the above

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

The somatic reflex arc affects the muscles and the receptor organ is skin whereas, the effector organ is skeletal muscles. The visceral reflex arc affects the internal organs and the receptor organ is epithelial lining of the gut whereas, the effector organ is smooth muscles. 

Therefore, the correct answer is option B.

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

All are examples of cranial reflexes but not

  1. Salivation

  2. Scratching

  3. Blushing

  4. Sneezing
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Reflex arc consists of sensory receptor, afferent neuron, centre, efferent neuron and effector organ. The reflexes that involve sensory and motor nerve fibres of cranial nerves and control the head region are known as cranial reflexes. Since, cranial reflexes involve head, eyes, nose, mouth, swallowing and facial expression, they produce the vital and involuntary responses. Spinal reflexes are the one in which spinal cord serves as centre without involvement of brain. They control the voluntary responses of other body parts via spinal cord. Salivation in response to sight/smell/thought of food, blushing and sneezing are involuntary actions, which involve mouth, facial expression and nose, and thus are categorized under cranial reflexes. Scratching is a voluntary response to itch stimulus in which brain is not involved and thus is a spinal reflex. 

Therefore, the correct answer is option B.

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.

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.