Advertisements
Advertisements
प्रश्न
With the help of a neat and labelled diagram, describe reflex arc.
Sketch and label reflex arc
Advertisements
उत्तर
Reflex arc: The pathway of nerve fibers along which the reflex impulse travels is known as a reflex arc. It is always unidirectional from receptor organs to the effector organ, CNS. The reflex arc is the structural and functional unit of reflex action.
Components of simple reflex arc:
The simple reflex arc is formed of five components as given below:
1. Receptor organ:
It is a specialized part of the body called the sense organ that receives the stimulus and converts it into an impulse. e.g. skin, eye, tongue, nose, and ears.
2. Sensory or Afferent neuron:
It carries sensory nerve impulses from the receptor organ to CNS. Its cyton is located in the dorsal root ganglion. Its dendron is long and connected to a receptor, while the axon enters the grey matter of the spinal cord to form a synapse.
3. Associated or Intermediate neuron:
It is present in the grey matter of the spinal cord. It receives a sensory impulse, interprets it, and generates motor impulses.
4. Motor or effector neuron:
Its cyton is present in the ventral horn of grey matter and the axon travels through the ventral root. It conducts motor impulses from the spinal cord to the effector organ.
5. Effector organ:
It is a specialized part of the body that is excited by receiving the motor impulse. It gives a proper response to the stimulus. e.g. Muscles and glands.
APPEARS IN
संबंधित प्रश्न
Name the most important part of the human brain.
A neuron which carries an impulse to the brain is called a ______ neuron.
What is spinal cord?
Which of the following are cerebral reflexes?
(i) a person pulls away his hand on touching a hot object
(ii) a person spits out immediately when a fly enters his mouth while talking
(iii) A person walking bare foot lifts his foot at once on stepping on to a nail
(iv) A person's pupil contracts at once in the presence of bright light
(a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (ii) and (iv)
The involuntary actions in the body are controlled by :
(a) medulla in forebrain
(b)medulla in hindbrain
(c) medulla in spinal cord
(d) medulla in midbrain
The part of brain which controls the involuntary action such as heart beat, breathing, blood pressure, etc. is :
(a) pons
(b) medulla
(c) cerebrum
(d) cerebellum
Which of the following statements are true?
(i) sudden action in response to something in the environment is called reflex action
(ii) sensory neurons carry electrical signals from spinal cord to muscles in a reflex action
(iii) motor neurons carry signals from receptors to spinal cord in a reflex action
(iv) the pathway of transmitting signals from a receptor to a muscle is a reflex action
P is a cell (or group of cells) in the human body which is sensitive to a particular type of stimulus and conveys the messages to CNS through nerves Q. On the other hand, R is a part of the human body which can respond to a stimulus according to the instructions sent from the CNS through nerves S.
(a) What is P? Name five organs which contain cells (or group of cells) like P.
(b) Name the nerves Q.
(c) What is R? Give two examples of R.
(d) Name nerves S.
(e) How do messages travel through the nerves Q and S?
Which of the following is an example of unconditioned reflex?
Categorise the following under stimulus and response.
Seeing a green light turning into red at a road crossing before applying the brakes.
