gessnic ianthe darrile
Elisa Rathrock
The human body is a complex machine that performs various functions to keep the body healthy and stable. The synergism of various organs of the body of an organism in a controlled manner to produce an appropriate reaction to a stimulus is called coordination.
The control and coordination of organs in an organism are done by the central nervous system of the body. This chapter gives a detailed picture of the structure of a neuron, tropic movements, reflex actions, hormones, the human brain and also about the types of nerves. These topics are explained diagrammatically and include all important concepts.
13. Which of the following is a growth movement and which is not?
(a) folding up of leaves of sensitive plant on touching with hand.
(b) folding up of petals of dandelion flower when light fades.
17. Plant parts show two types of movements, one dependent on growth and other independent of growth. Give one example of the movement in plant parts:
(a) which depends on growth
(b) which does not depend on growth
21. (a) What does a Mimosa pudica plant do in response to touch? What is this phenomenon known as?
(b) What happens to the dandelion flower (i) during daytime, and (ii) at night? What is this phenomenon known as?
22. (a) What does a plant root do in response to water? What is this phenomenon known as?
(b) What happens to the moonflower (i) during daytime, and (ii) at night? What is this phenomenon known as?
Phototropism: The stems of plants respond to sunlight by growing towards it. The plants also turn their leaves to face the sun. This enables their leaves to get as much sunlight as possible that is required for photosynthesis.
(a) The non-directional movement of a plant part in response to an external stimulus is known as nastic movement. Example: The folding and drooping up of leaves in sensitive plants in response to touch.
The folding up of leaves in a sensitive plant on touching is not a tropism because it is a non-directional movement. Tropism is a directional movement where the parts of plant move in a particular direction with response to stimulus.
The closing of a dandelion flower at dusk is not a tropism because it is a non-directional movement in response to the intensity of light. Tropism is a directional movement where the parts of plant move in a particular direction with response to stimulus. The intensity of light is not a keen factor.
34. (a) Define phototropism. Give one example of phototropism.
(b) How does phototropism occur in a plant stem (or shoot)? Explain with the help of labeled diagrams.
(c) What is meant by positive phototropism and negative phototropism? Give one example of each type.
36. (a) How does control and coordination take place in plants? How does it differ from that in animals?
(b) Name five stimuli which act on plants. Name the type of tropism produced by each one of these stimuli.
(c) Define hydrotropism. Give one example of hydrotropism. State whether this example is of positive hydrotropism or negative hydrotropism. Illustrate your answer with the help of the labeled diagram.
(c) The movement of plant parts in response to water is known as hydrotropism. The movement of plant roots towards water is hydrotropism. It is a positive hydrotropism because the roots move towards the stimulus.
37. (a) What is meant by positive tropism and negative tropism? Explain with examples.
(b) Define thigmotropism. Give one example of thigmotropism.
(c) What is the difference between thigmotropism and thigmonasty? Name one plant which exhibits thigmotropism and one plant which exhibits thigmonasty. What behaviour (or responses) of these plants make you think that they exhibit thigmotropism and thigmonasty respectively?
(b) The directional movement of plant parts in response to touch is known as thigmotropism. The movement of tendrils of climbing plants towards the things they happen to touch is an example of thigmotropism.
44. Which of the following is not caused by a growth movement?
(a) bending of the shoot of a plant in response to light
(b) closing up of leaves of a sensitive plant on touching with an object
(c) climbing up of a plant on an object by using tendrils
(d) movement of the root of a plant towards a source of water
47. The growth of tendrils in pea plants is due to the:
(a) effect of sunlight on the tendril cells facing the sun
(b) effect of gravity on the part of tendril hanging down towards the earth
(c) rapid cell division and elongation in tendril cells that are away from the support
(d) rapid cell division and elongation in tendril cells in contact with the support
68. Which of the following are not tropisms?
(i) growing of pollen tube in response to a sugary substance
(ii) folding up of leaves of sensitive plant in response to touch
(iii) winding of tendril around a support in response to touch
(iv) opening up of the leaves of a daisy flower in response to light
(b) Our nervous system allows us to react to our surroundings. Information from receptors passes along the sensory neurons to our brain. Our brain sends impulses along the motor neurons to our muscles.
(a) Spinal cord is a cylindrical structure made up of nervous tissue, extends from medulla to the lumbar region of vertebral column by a bony cage called the vertebral column. The spinal cord is responsible for spinal reflex actions and the conduction of nerve impulses from the brain.
34. (a) Name the three types of nerves which constitute the peripheral nervous system.
(b) What is the difference between a reflex action and walking?
(c) How do we detect the smell of an incense stick (agarbatti)?
(c) The olfactory receptors present in our nose helps to detect the smell of an incense stick. These receptors through electrical signals send the information to brain. Then the brain interprets this information as the smell of incense stick where it has been already stored.
(b) Cerebrum: It is known as the logical part of the brain. It helps in building logical skills like learning, reasoning, intelligence, personality and memory. The thoughts, sensations, actions and movements are controlled by the cerebrum.
The function of insulin hormone is to regulate the blood sugar level. The metabolism of sugar is maintained by insulin. Diabetic patients are treated by giving injections of insulin as these patients suffer from deficiency of insulin in their body.
45. 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.
The action performed by the person is reflux action. The person feels the pain in the foot and hence withdraws his foot from the pin. Foot acts as receptor and pain acts as stimulus. The neurons transmits the message sent from the impulse to sensory organ and the message is transmitted to spinal cord. Then the impulse is passed to a relay neuron which, in turn, passes it to a motor neuron. The motor neuron passes the impulse to the muscle in the foot. The muscle, then, contracts and pulls the foot away from the drawing pin.
Puberty and adolescence are results of the activities of testosterone in males and oestrogen in females. In males during puberty, testosterone secretion is increased resulting in the development of male sex organs and male characters such as deeper voice, moustache, beard and more body hair.
53. (a) Name the structural and functional unit of the nervous system.
(b) Draw a flow chart to show the classification of the nervous system into various parts.
(c) What is the autonomic nervous system? What is its function?
(d) What is voluntary nervous system? Explain the working of the voluntary nervous system with an example.
(c) The autonomic nervous system is the part of the nervous system. It regulates the functions of the internal organs of the body. The vital function is to control and regulate involuntary actions like heartbeat, blood flow, breathing and digestion.
(d) Voluntary nervous system is the part of the nervous system that is responsible for carrying motor and sensory information both to and from the central nervous system (CNS). It is associated with voluntary control of body movements through the actions of skeletal muscles. It is also responsible for sensing external stimuli, which helps the body to remain in touch with its surroundings. The nerve impulses are generated in the sensory nerves and conducted to the brain. The brain sends instructions to the skeletal muscles (effector muscle) through the motor nerves to remove the pin. Then the muscle acts accordingly and removes the pin.
54. (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?
55. (a) What is the function of our nervous system?
(b) What are the main organs of the human nervous system? Draw a labelled diagram to show the main organs of the human nervous system.
(c) How does the human nervous system work? Explain.
(c) Our body has five sense organs such as eyes, ears, nose, tongue, and skin. When these are affected a message is sent to brain via electrical impulse through the sensory organs. The brain does the specific action to be carried out. The motor neurons receives information from brain and the concerned muscles performs the action.
56. (a) What is a neuron? Draw a labelled diagram of a neuron.
(b) 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.
(b) Synapses are microscopic gaps present in between pairs of adjacent neurons over which nerve impulses pass from one neuron to the next. A stimulus acts an electrical impulse is sent from the sensory organ. The impulse travels from the dendrites of the sensory neuron (say A) to its cell body and, then, along its axon. The electrical impulse releases chemical substances called neurotransmitters into the synapse which cross the synapse and start a similar electrical impulse in the dendrites of the next neuron.
c01484d022