Prof. Noriah's note (2)

Spinal cord

Note:

Tract: is a bundle of myelinated nerve fibers located in the CNS (brain + spinal cord).

Sensory (ascending tract) consist of fibers that carry impulse up the spinal cord to different region of the brain.

Motor (descending) tracts - nerve fibers that carry impulses down the spinal cord.


Pathway: is the route followed by a nerve impulse as it travel through the nervous system

In sensory pathway:
Sensory receptor → sensory neuron into spinal cord → travels up the spinal cord by way of sensory (ascending) tract → brain

In motor pathway:
Impulse starts in the brain → travel down the spinal cord by motor (descending) tract → exit spinal cord by way of motor nerve → ends of a muscle/gland

Prof. Noriah's note

Nervous system:
1. CNS
2. PNS


CNS
- consist of brain + spinal cord


PNS
- consist of nerves outside the brain and spinal cord

- cranial nerve (12 pairs) - emerging from the brain - mainly supply structure above the neck

- spinal nerve (31 pairs) - emerging from the brain - supply structures in the trunk + limb


Note: Neuron
- afferent (sensory) = carry impulses towards CNS
- efferent (motor) = carry impulse away from CNS
- interneuron = reside entirely within CNS


Efferent nerve - 2 types
(a) Somatic nerve (motor nerve) - innervate skeletal muscle(somatic nervous system)

(b) Autonomic nerve (motor nerve) - innervate cardiac muscle, smooth muscle or glands (Autonomic Nervous System - ANS)

Action carried out by somatic nervous system are voluntary.

Action carried out by ANS are involuntary + automatic


Sensory Neuron
Carry impulse into CNS from receptors.

Receptors
- for general senses (touch, pressure, vibration, temperature, pain + proprioceptor)

- for special senses ( smell, taste, vision, hearing + equilibrium)