Lecture notes
PNS 2
- Module
- Physiology (BM4MAP)
- Institution
- Aston University, Birmingham (Aston)
part 2 of PNS topic, in depth lecture notes
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2 efferent nervous divisions1. Somatic- voluntary
2. Autonomic- involuntary
- Sympathetic
- Parasympathetic
Afferent fibres travel within the same nerves as efferent fibres but in the opposite direction.
ü Anatomy of PNS
Spinal nerves contains both sensory and motor fibres.
31 pairs of fibres and each are named and numbered according to the region of vertebra
column from which they emerge.
- 8 pairs of cervical nerves
- 12 pairs of thoracic nerves
- 5 pairs of lumber nerves
- 5 pairs of sacral nerves
- 1 coccygeal nerve
Difference between the somatic and autonomic efferent divisions.
Somatic Autonomic
Motor neurone localised in the ventral hole First neurone is localised in the lateral hole
of the spinal cord. of the spinal cord and the second neurone
is localised in autonomic ganglion.
Single myelinated neuron 2 neurones, first neurone is myelinated,
and the second one is unmyelinated.
Voluntary branch Involuntary neurone
From CNS to effector organ= skeletal From CNS to effector neurone= cardiac and
muscle smooth muscle etc.
Autonomic nervous system
- The first neurone (preganglionic fiber) which is myelinated goes from lateral
horn of the spinal cord to the autonomic ganglion.
- Another neurone (post ganglionic fiber) which is unmyelinated goes from the
autonomic ganglion the effector organs.
Autonomic ganglion is localised in the vertebra column.
Difference between sympathetic and parasympathetic.
1. Parasympathetic is localised in the brain or sacral region whereas Sympathetic is
localised in the thoracic and lumber region.
2. Parasympathetic has long preganglionic fibres and end in terminal ganglia which are
very close to the organ they innervate whereas sympathetic has short preganglionic
fibres.
3. The neurotransmitter for the preganglionic fibre is the same for both (Ach) but the
difference is with the neurotransmitter released by post ganglionic fibre. It is Ach for
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