Question

Q4. Give reasons for the following:
a) Neurons are often long and wire like.
b) Alveoli in lungs have thin membrane.
c) Plasma membrane plays an important role in generating immune responses.
d) Nucleus occupies a peripheral position I mature plants cells.​

Answer 1

Answer:

a) Neurons are the special cells of the nervous system which facilitate and transmits the nerve impulses or action potentials. Thus, they possess such a structure which helps in easy transmission of the nerve impulses. ​

The dendrites of a neuron are thin, branching projections that receives the neurotransmitters and creates a change in voltage in the cell. The axons on the other hand are long projections whose function is to carry the action potential away from the cell body toward the next neuron. The axon through its axon terminal, transmits the signal to the dendrites of the next neuron, which is separated by a small gap called synapse.

b) Alveoli are the small balloon like structures present in the lungs in numerous quantities, which help in the exchange of gases between blood and lungs. When we inhale oxygen enters into the bloodstream by passing through the walls of alveoli and release carbon-dioxide when we exhale.

c) Plasma membrane is the membrane that separate the inner environment of the cell with the outer environment. It is also known as the cell membrane or cytoplasmic membrane. It is present as an outer most layer in animal cell and as a layer inner layer nest to cell wall in the plant cell.

d) With the help of Rutherford Experiment we can see that only some rays are reflected back to their path that there is small area of positive charge called nucleus.Nucleus is at the centre of Atom it consist maximum mass of atom.