Reflex Arc

Q.

Which is the correct sequence of the components of a reflex arc?

1. $\text{Receptors}\to \text{muscles}\to \text{sensory neuron}\to \text{motor neuron}\to \text{spinal cord}$

2. $\text{Receptors}\to \text{motor neuron}\to \text{spinal cord}\to \text{sensory neuron}\to \text{muscles}$

3. $\text{Receptors}\to \text{spinal cord}\to \text{sensory neuron}\to \text{motor neuron}\to \text{muscles}$

4. $\text{Receptors}\to \text{sensory neuron}\to \text{spinal cord}\to \text{motor neuron}\to \text{muscles}$

Q. Explain reflex action? [5 MARKS]

Q. b) What is meant by receptors and effectors? Give two examples of each.

Q.

What are voluntary actions? Give any two examples of these actions.

Q.

(a) What is a reflex action ? Explain with the help of an example.

(b) Define reflex arc. Give the flow chart of a spinal reflex arc.

(c) How are involuntary actions and reflex actions different from each other ?

Q.

The long fiber that carries impulses away from the cell body is called

1. dendrite

2. interneuron

3. axon

4. axon terminal

Q.

The electrical impulse travels in a neuron from

1. $\mathrm{dendrite}\to \mathrm{axon}\to \mathrm{axonal}\mathrm{end}\to \mathrm{cell}\mathrm{body}$

2. $\mathrm{cell}\mathrm{body}\to \mathrm{dendrite}\to \mathrm{axon}\to \mathrm{axonal}\mathrm{end}$

3. $\mathrm{dendrite}\to \mathrm{cell}\mathrm{body}\to \mathrm{axon}\to \mathrm{axonal}\mathrm{end}$

4. $\mathrm{axonal}\mathrm{end}\to \mathrm{axon}\to \mathrm{cell}\mathrm{body}\to \mathrm{dendrite}$

Q.

Give three examples of reflex actions.

Q.

One of the following gives the correct sequence of the components in a reflex arc. This is :

(a) Receptors $\to$ Muscle $\to$ Sensory neuron $\to$ Motor neuron $\to$ Spinal cord

(b) Receptors $\to$ Motor neuron $\to$ Spinal cord $\to$ Sensory neuron $\to$ Muscle

(c) Receptors $\to$ Spinal cord $\to$ Sensory neuron $\to$ Motor neuron $\to$ Muscle

(d) Receptors $\to$ Sensory neuron $\to$ Spinal cord $\to$ Motor neuron $\to$ Muscle

Q.

Give two examples of conditioned reflexes.

Q.

What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?

Q. Why has reflex arc evolved in vertebrates??

Q.

If we happen to touch a hot object unknowingly, we immediately pull back our hand. What is this type of action known as?

Q.

Why are the reflex actions controlled by the spinal cord and not the brain?

Q.

The gustatory receptors of our body are in one of the following organs. This organ is :

(a) ear

(b) nose

(c) tongue

(d) skin

Q.

Name the part of the neuron:

1. Where information is acquired
2. Through which information travels as fast as an electrical impulse.

Q.

Trace the sequence of events, which occur in our body when a bright light is focused on eyes

Q.

A person walks across a room in bare feet and puts his foot on a drawing pin lying on the floor. He lets out a cry. Explain what happens in his nervous system in bringing about this response.

Q.

The sequence of the components of a reflex arc is

$Receptors\to Spinalcord\to Sensoryneuron\to Motorneuron\to Muscles$

1. True

2. False
   

Q.

Which of the following is an example of reflex action?

1. To shoot the bird after aiming

2. Watering of the mouth after seeing the good edibles

3. To obey the order

4. To read story

Q. What is a synapse? ​
What happens at the synapse between two neurons? ​
How are the messages carried across a synapse?
Explain with the help of a labelled diagram. ​

Q.

What is true about unmyelinated nerve fibre?

1. Not enclosed by both Schwann cells and a myelin sheath

2. Enclosed by Schwann cells that do not form a myelin sheath

3. Not enclosed by Schwann cells but enclosed by a myelin sheath

4. Not found in the autonomous and the somatic neural system

Q.

Blink our eyes when light suddenly falls on our eye is controlled spinal cord.

1. Reflex action

2. Voluntary action

Q.

Why does the nerve impulse flow more rapidly in myelinated nerve fiber than in the non-nucleated fibers.

Q.

What is the difference between reflex action and voluntary action?

Q.

When we touch a hot plate unknowingly, then this heat is sensed by a receptor P present in our fingers. The receptor triggers an impulse in neuron Q which transmits the message to an organ R which is a part of the central nervous system. Here the impulse is passed on to a neuron S which in turn passes it to a yet another neuron T. The neuron T passes the impulse to a tissue U in our arm. The tissue U then contracts and pulls our hand away from the hot plate.

(a) What is the name of (i) receptor P (ii) neuron Q, and (iii) organ R ?

(b) What is (i) neuron S, and (ii) neuron T ?

(c) Name the tissue U.

(d) What name is given to the phenomenon in which hand is pulled away quickly from the hot plate ?

(e) Name the effector in this whole process.

Q.

The junction between two neurons is called a:

1. Synapse

2. Axon

3. Dendrites

4. None of the above

Q.

Match the following-

1. 1 – v; 2 – iv; 3 – ii; 4 – iii; 5 – i

2. 1 – iv; 2 – v; 3 – ii; 4 – iii; 5 – i

3. 1- iv; 2 – iii; 3 – iv; 4 – ii; 5 – i

4. 1 – iv; 2 – v; 3 – iii; 4 – ii; 5 – i

Q.

The contraction of pupil of the eye in the presence of bright light is an example of :

(a) Voluntary reflex

(b) Spinal reflex

(c) Cerebral reflex

(d) Adrenal reflex

Q.

When you smell a favourite food your mouth begins to water (that is, you secrete saliva). Write down what the following are examples of :

(a) the smell of the food

(b) the cells in your nasal passage which perceive the smell

(c) the gland which stimulated to secrete saliva.