The Basic Anatomy & Functioning of the Peripheral Nervous System Flashcards
Which type of neurone (no. of poles) is most common in the ANS and motor nervous system?
Multipolar
Which type of neurone (no. of poles) is most common in the sensory nervous system?
Unipolar (or pseudounipolar)
How many tracts are in the motor pathway?
2: Lower Motor Neurone (LMN) and Upper Motor Neurone (UMN)
How many tracts are in the sensory pathway?
3: 1st Order neurone, 2nd order neurone, 3rd order neurone.
What is the name for a group of nerve cell bodies in the CNS?
Nucleus
What is the name for a group of nerve cell bodies in the PNS?
Ganglion
What is the name for a bundle of axons in the CNS?
A tract (usually single modality)
What is the name for a bundle of axons in the pNS?
A nerve (often mixed)
How many pairs of spinal nerves are there?
31
Where can spinal nerves be found?
Intervertebral foramina
What kind of information is carried in the posterior roots and rootlets?
Sensory (towards cord)
What kind of information is carried in the anterior roots and rootlets?
Motor (away from cord)
What location does the smaller posterior rami serve?
Posterior body wall
What location does the larger anterior rami serve?
Anterolateral body wall
What information travels in the Spinothalamic Tract (STT)?
Sensory (afferent)
What information travels in the Corticospinal Tract (CST)
Motor (efferent)
Where do tracts decussate (cross) in the STT?
They crossover in the spinal cord, usually 1-2 spinal nerve segments above their point of entry. The second order neurone travels to the thalamus and synapses with a 3rd order neurone.
Where do tracts decussate (cross) in the CST?
Around 90% of the tract decussates in the medulla, forming the lateral corticospinal tract. The remaining 20% form the ventral corticospinal tract and cross at the appropriate spinal level
Which spinal nerve corresponds to dermatome covering the male nipple?
T4
Which spinal nerve corresponds to the dermatome covering the umbilicus?
T10
Which spinal nerves correspond to the upper limb dermatomes?
C5-T1
Which spinal nerves correspond to the lower limb dermatomes?
L2-Co1
What is a plexus?
A network of intertwined anterior rami.
What are the roots of the cervical plexus?
C1-C4
What are the roots of the brachial plexus?
C5-T1
What are the roots of the lumbar plexus?
L1-L4
What are the roots of the sacral plexus?
L5-S4
What is a dermatome?
The area of skin supplied by the anterior and posterior rami of a specific spinal nerve.
What is a myotome?
The skeletal muscles supplied with motor innervation by both the anterior and posterior rami of a specific spinal nerve.
NB - dos not always correspond to dermatome (e.g. diaphragm)
Sympathetic outflow occurs at which spinal levels?
T1-L2 into sympathetic chains (paravertebral ganglion)
How do sympathetic nerves reach the body wall?
They pass into all spinal nerves from anterior rootlets and then synapse in the paravertebral ganglion.
How do sympathetic nerves reach the organs?
They hitch a ride with arteries to all head an neck organs.
What is different about sympathetic outflow to the abdominopelvic organs?
Axons synapse in the pre vertebral ganglia (beyond sympathetic trunk). All the others synapse in the paravertebral ganglia (within sympathetic trunk)
What is different about sympathetic innervation to the adrenal glands?
Axons synapse directly onto the organ.
How do parasympathetic nerves reach the organs?
NB - no parasympathetic supply to body wall
CN III, VII, IX, X and sacral spinal nerves.
What is different about the Vagus nerve (CN X) and the sacral spinal nerves?
These synapse in ganglia on or very close to the organs themselves. The others synapse in ganglia distant to their target organs e.g. ciliary ganglion
