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प्रश्न
A cylindrical structure P in our body begins in continuation with medulla and extends downwards. It is enclosed in a bony cage Q and surrounded by membranes R. As many as x pairs of nerves arise from the structure P. The structure P is involved in the reflex actions of our body and conduction of nerve impulses to and from another organ S of our body with which it forms CNS.
(a) Name the structure P.
(b) Name (i) bony cage Q, and (ii) membranes R.
(c) How much is x?
(d) Name the organs S.
(e) What are the reflexes involving structure P only known as?
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उत्तर
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- The structure P is the spinal cord. It is a cylindrical structure that begins in continuation with the medulla and extends downwards.
- (i) The bony cage Q is the vertebral column. The spinal cord is enclosed by the vertebral column.
- x represent the number of pairs of spinal nerves. They are 31 in number.
- S is the brain. The central nervous system consists of the brain and the spinal cord.
- The reflex actions involving the spinal cord (P) are known as spinal reflexes.
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संबंधित प्रश्न
What is the role of the brain in reflex action?
With the help of a neat and labelled diagram, describe reflex arc.
Which of the following is not a natural reflex action?
A. Knee-jerk
B. Blinking of eyes due to strong light
C. Salivation at the sight of food
D. Sneezing when any irritant enters the nose
A person walks across a room in barefeet 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.
What is the difference between a voluntary and an involuntary action? Which kind of action is digestion? Explain your choice.
Which of the following is not an involuntary action?
(a) vomiting
(b) chewing
(c) heart beat
(d) salivation
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
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
Note the relationship between the first two words and suggest the suitable word/words for the fourth place.
Stimulus : Receptor :: Impulse : ______.
State whether the following is simple reflex, conditioned reflex or neither of the two.
Contraction of eye pupil
Reflex action is controlled by the
What type of reflex is the following?
Sweating in summer
What type of reflex is the following?
Blinking of the eye
Mention, if the following statement is True or False
A reflex action is a spontaneous response to a stimulus.
Give an example for conditioned reflexes.
Reflex arc allows the rapid response of the body to a stimulus.
What kind of reflex is cycling?
Categorise the following under stimulus and response.
Pain in the eye if something falls into it.
The diagram given below shows the internal structure of a spinal cord depicting a phenomenon. Study the diagram and answer the following questions.
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- Name the phenomenon shown in the figure and define the same.
- Identify the parts labelled as 1 and 2. Write one functional difference between these two.
- Name the bony protective covering and the membranous protective covering of the spinal cord.
- Label the guidelines 3 and 4.
- How is the labelled part 3 different from part 4 with respect to its composition (part of neuron)?
- Give the technical term for the point of contact between the two nerve cells.
- Name the fluid filled inside the central canal of spinal cord.
- Name the term used for a small gap between two neurons.
- Give one example of a neurotransmitter.
- Draw a neat diagram of a nerve cell and label the parts: Perikaryon, Node of Ranvier, Myelin sheath and Axon terminals.
