Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Nervous system:- It is consist of neurons, bundles of nerve fibres, neuroglia cells and have neurosecretory cells. Human nervous system is consist of two main parts:- CNS (central nervous system)- lies along the main axis of the body, consists of upper large brain in head or narrow spinal cord in neck or trunk.
PNS (peripheral nervous system)- It is associated with the CNS defined by afferent nerve fibre that transmit impulses from receptors present in organs to CNS) and efferent nerve fibre which transmit regulatory impulses from CNS to peripheral organs.
It is divided into two parts:
1. Somatic nervous system relays voluntary impulses from CNS to skeletal muscles.
2. Autonomic nervous system relays impulses from CNS to involuntary parts of the body.
On the other hand, hormonal mechanism is slower than nervous mechanism. Hormones are the chemical messengers which brings control, secreted by endocrine glands and released into the blood stream from axon ending. Various hormonal secretion is done by hypothalamus and are under control of secretion of neurosecretory cells.
Draw the structure of a neuron and explain its function.
Which signals will get disrupted in case of a spinal cord injury?
How does chemical coordination take place in animals?
Why is the use of iodised salt advisable?
The brain is responsible for
(a) thinking.
(b) regulating the heart beat.
(c) balancing the body.
(d) all of the above.
How do we detect the smell of an agarbatti (incense stick)?
How do auxins promote the growth of a tendril around a support?
Which part of the brain maintains posture and equilibrium of the body?
How does our body respond when adrenaline is secreted into the blood?
What is the need for a system of control and coordination in an organism?
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.
What is a good source of energy?
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
What are trophic levels? Give an example of a food chain and state the different trophic levels in it.
What changes can you make in your habits to become more environment-friendly?
What is the importance of DNA copying in reproduction?
If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Why should a magnesium ribbon be cleared before burning in air?
Define the principal focus of a concave mirror.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
Why should curd and sour substances not be kept in brass and copper vessels?
The autotrophic mode of nutrition requires
(a) carbon dioxide and water. (c) sunlight.
(b) chlorophyll. (d) all of the above.
What are the problems caused by the non-biodegradable wastes that we generate?
How does the embryo get nourishment inside the mother’s body?
An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.
Oil and fat containing food items are flushed with nitrogen. Why?
Why do HCl, HNO3, etc., show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?
On the basis of the issues raised in this chapter, what changes would you incorporate in your lifestyle in a move towards a sustainable use of our resources?
Explain the following.
(a) Why is the tungsten used almost exclusively for filament of electric lamps?
(b) Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?
(c) Why is the series arrangement not used for domestic circuits?
(d) How does the resistance of a wire vary with its area of cross-section?
(e) Why are copper and aluminium wires usually employed for electricity transmission?