Human Nervous System is made up of the Central Nervous System (CNS) & the Peripheral Nervous System (PNS).
- PNS consists of the cranial nerves (12 pairs) & the spinal nerves (31 pairs).
- CNS is the control centre of the body.
- Spinal Cord (SC) link between the brain & the PNS.
- In a cross section, SC consists of :
1) grey//gray matter which consists mainly of cell bodies of neurones (nerve cells).
2) white matter (surrounding the grey matter), which consists of myelin-coated axons of neurones. - Spinal nerves arise from the SC & has a dorsal root & a ventral root.
- Dorsal root ganglion - contains cell bodies of afferent neurone.
*note: in the above diagram, an Interneurone should be drawn to connect the Sensory neurone to motor neurone via synapse.
- Neurones (nerve cells):
1) a typical neurone has a cell body, dendrites & usually one axon.
2) neurones transmit nerve impulses (NI)/electrical signal to other nerve cells, glands or muscles. - There are 3 types of neurones.
1) Afferent neurone (AN) / sensory neurone
2) Interneurone (IN) / (relay neurone, association neurone)
3) Efferent neurone (EN) / motor neurone
*note: EN (neurone P), IN (neurone Q), AN (neurone R).
** unipolar, bipolar, multipolar neurones are not part of spm syllabus.
- State the differences between neurones:
1) AN has cell body located at one side, EN has cell body located at one end while IN has cell body located at the centre.
2) AN transmits/sends NI from the sensory receptor to the CNS, EN transmits NI from the CNS to the effectors while IN transmits NI from the AN to the EN.
3) - State the function of dendrite, axon, myelin sheath, node of Ranvier. (refer yr notes.)
- draw a labelled diagram of EN. (refer yr notes for drawing)
