Week 7 - The Motor Unit Flashcards
how many pairs of nerves does the PNS have ?
43 pairs
how many pairs of nerves are cranial nerves ?
12
how many pairs of nerves are spinal nerves ?
31
what are the 5 spinal nerves ?
- cervical nerves
- thoracic
- lumbar
- sacral
- coccygeal
how many pairs of cervical nerves are in the PNS ?
8
where are cervical nerves located
head and neck
how many pairs of thoracic nerves are in the PNS ?
12
where are thoracic nerves located ?
upper extremities, chest, upper abdomen
how many pairs of lumbar nerves are in the PNS ?
5
where are lumbar nerves located ?
lower abdomen, hips, legs
how many pairs of sacral nerves are in the PNS ?
5
where are sacral nerves located ?
lower extremities, pelvis
how many pairs of coccygeal nerves are in the PNS ?
1
where are coccygeal nerves located ?
coccyx
define nerve
a bundle of fibres within a connective tissue sheath
define neruon
a single nerve
what are the 3 types of neuron ?
- efferent (motor)
- afferent (sensory)
- interneurons (connector)
what type of motor neuron initiates a muscle contraction ?
alpha motor neurons
what type of motor neuron innervate muscle spindles ?
gamma motor neurons
what are the 6 components of a motor neuron ?
- cell body (soma)
- dendrites
- axon
- terminal branches
- myelin sheath
- Ranvier node
define soma
- cell body
- contains nucleus
- within grey matter of spinal cord or ganglia
define dentrites
- projections of the cell body
- receive signals from other neurons
define axon
- the nerve fibre
- exits spinal cord via ventral root
- large in motor neurons
define terminal branches
- unmyelinated branches at end of axon
- form neuromuscular junction with muscle fibres
