Question

Question 9 Differentiate between:

(a) Myelinated and non-myelinated axons

(b) Dendrites and axons

(c) Rods and cones

(d) Thalamus and Hypothalamus

(e) Cerebrum and Cerebellum

Class - XI - Biology Chapter Neural Control and Coordination Page No. 329

Answer 1

(a) Myelinated and non-myelinated axons

Myelinated axons

Non myelinated axons

These appear whitish in colour.These appear greyish in colour.Myelin sheath is presentMyelin sheath is absentNodes of Ranvier are present at intervals.Nodes of Ranvier are absent.Transmission of nerve impulse is faster.Transmission of nerve impulse is slowerIon exchange can occur only at the nodes.Ion exchange occurs all over the surface.
(b) Dendrites and axons

Dendrites

Axons

These are extension of cyton present at anterior position.These are extension of cyton present at posterior position.These conduct impulses towards the cell body.These conduct impulses away from the cell body.Dendrites are always non-myelinated.Axons can be myelinated or non-myelinated.The terminals of dendrites become receptors.The terminals of axon ends in a group of branches called terminal arborisations.
(c) Rods and cones

Rods

Cones

Rods are sensitive to dim light.Cones are sensitive to bright light only.They have visual purple pigment called rhodopsin.They have visual violet pigment called iodopsin.Colours are not visible with rod cells.Cones help to see colours.
(d) Thalamus and Hypothalamus

Thalamus

Hypothalamus

It represent the side of diencephalon.It represents the lower part of diencephalon.It is the major coordinating centre for sensory and motor signalling.It is the major centre for regulation of body temperature, thirst, hunger etc.It does not secrete any hormone.It secretes several hormones.
(e) Cerebrum and Cerebellum

Cerebrum

Cerebellum

It is part of fore brainIt is part of hind brainIt consists of two cerebral hemispheres.It consists of two cerebellar hemispheres and a median vermis.It initiates voluntary movements.It maintains posture and equilibrium.