Question -
Answer -
Listed below are thedifferences:
(a) Myelinated andnon-myelinated axons
| Characteristics/Features | Myelinated axons | Non-myelinated axons |
| Myelin sheath | Present | Absent |
| Nodes of Ranvier | Present | Absent |
| Location | Found in grey matter of the brain, autonomous nervous system, spinal cord | Spinal cord, white matter of the brain, autonomous nervous system |
| Conduction of nerve impulse | Node to node | Smooth |
| Speed of impulse-conduction | 50 times faster than non-myelinated axon | Comparatively lower |
(b) Dendrites andaxons
| Dendrites | Axons |
| Dendrites are short processes | They are long processes |
| They carry impulse towards the cell body of the neuron | They carry impulse away from the cell body to the neuron |
| They are branched, always | Axons may or may not be branched |
| Nissl’s granules are found in neuroplasm | Nissl’s granules are absent in neuroplasm |
(c) Rods and cones
| Rods | Cones |
| Sensitive to dim light | Sensitive to bright light |
| Contains rhodopsin pigment | Contains iodopsin pigment |
| Not involved in colour vision | Crucial in imparting colour vision |
| Rods are of one kind only | Three kinds of cones exist sensing – red, blue, green lights |
(d) Thalamus andHypothalamus
| Thalamus | Hypothalamus |
| Consists of grey matter only | Consists of white and grey matter |
| Does not secrete hormones | Secretes several hormones that control the activity of pituitary gland |
| Located above the midbrain | Located at the base of the thalamus |
| Has the centre for sensations namely – cold, pain, heat | Has the centre for sensations namely – regulating body temperature, homeostasis, blood pressure |
(e) Cerebrum andcerebellum
| Cerebrum | Cerebellum |
| Brain is majorly covered by the cerebrum | Second largest part of the brain after cerebrum |
| It is portion of forebrain | It is part of hindbrain |
| It is divided into two cerebral hemispheres | It is divided into three lobes namely – central vermis, two lateral cerebral hemispheres |
| It is the centre for intelligence and memory | It is the centre for posture and body equilibrium |