Principles - Structure of the Nervous System Flashcards
What do nerve cells consist of?
Dendrites (branched projections)
Body (contains the nucleus)
Axon/ nerve fibre (covered by myelin sheath)
What carries action potentials from the nerve cell?
the axon/ nerve fibre
What receives/ conducts information to the nerve cell?
Dendrites
What happens in a ganglion in the PNS?
One nerve fibre synapses onto another neurone’s cell body
Why must synapses occur in the ganglion in the PNS?
As this is where cell bodies are found
What is a synapse?
Where one neurone communicates with another neurone in a ganglion in the PNS or in a nucleus in the CNS
Here, the electrical AP becomes a chemical signal (neurotransmitter
) and then becomes an AP again
In the brain, what is a sulcus?
A depression or groove on the surface of the brain
In the brain, what is a gyrus?
A ridge on the surface of the brain
What are the four lobes of each cerebral hemisphere?
Named according to the cranial bone that they lie deep to.
Occipital, parietal, frontal, temporal
What is grey matter?
The outermost layer of the cerebral cortex, full of cell bodies
What is white matter?
Deep to the grey matter, contains many axons which are myelinated, giving the white appearance
How is the grey and white material arranged in the spinal cord?
The opposite to how it is in the brain - white matter is superficial and grey matter is deep
What is CN I? Is it sensory, motor or both?
Olfactory nerve
Sensory
What is CN II? Is it sensory, motor or both?
Optic nerve
Sensory
What is CN III? Is it sensory, motor or both?
Oculomotor nerve
Motor
What is CN IV? Is it sensory, motor or both?
Trochlear nerve
Motor
What is CN V? Is it sensory, motor or both?
Trigeminal nerve
Both
What is CN VI? Is it sensory, motor or both?
Abducens nerve
Motor
What is CN VII? Is it sensory, motor or both?
Facial nerve
Both
What is CN VIII? Is it sensory, motor or both?
Vestibulocochlear nerve
Sensory
What is CN IX? Is it sensory, motor or both?
Glossopharyngeal nerve
Both
What is CN X? Is it sensory, motor or both?
Vagus nerve
Both
What is CN XI? Is it sensory, motor or both?
Spinal Accessory nerve
Motor
What is CN XII? Is it sensory, motor or both?
Hypoglossal nerve
Motor
Which foramen does CN I enter the brain through?
Cribriform plate of the ethmoid bone
Which foramen does CN II enter the brain through?
Optic canal
Which foramen does CN III, CN IV, CN V1 and CN VI leave the brain through?
Superior orbital fissure
CN V1 is both sensory and motor so enters and leaves the brain through this
Which foramen does CN V2 leave/enter the brain through?
Foramen rotundum
Which foramen does CN V3 leave/enter the brain through?
Foramen ovale
Which foramen do CN VII and VIII go through?
Internal acoustic meatus
Which foramen do CN IX, X and XI leave the brain through?
Jugular foramen
Which foramen does CN XII leave the brain through?
Hypoglossal canal
What leaves the brain through the foramen magnum?
Spinal cord
Where are the two enlargements of the spinal cord?
Cervical
Lumbosacral
Where does the spinal cord end?
Inferiorly at L1/L2 intervertebral disc level
Adult vertebral column is longer then the adult spinal cord
How do lumbar and sacral spinal nerves leave the vertebral column? (seeing as the spinal cord ends at L1/L2)
They have to descend in the vertebral canal to their respective intervertebral foraminae
What are the spinal nerves?
8 pairs of cervical (C1 to C8) 12 pairs of thoracic (T1-T12) 5 pairs of lumbar spinal nerves (L1-L5) 5 pairs of sacral spinal nerves (S1-S5) 1 pair of coccygeal spinal nerves (Co)
How are spinal nerves named?
According to the vertebrae above it EXCEPT in the cervical region where they are named according to the vertebrae below it
What do spinal nerves supply?
The soma (body wall) Each pair supplies one strip of the soma
Where are spinal nerves located?
ONLY within the intervertebral foraminae
From the intervertebral foraminae what do the spinal nerves connect with?
Structures of the soma via rami
The spinal cord via roots and rootlets
What do posterior rami supply?
The posterior paramedian strip
What do anterior rami supply?
The remainder of the posterior part of the strip, the lateral and the anterior parts of the strips
Supply all the limbs via a plexus - no rami in the limbs
True or False - the posterior rami is bigger than the anterior.
False
The anterior rami is always bigger as it supplies more
What is a dermatome?
An area/strip of skin supplied by both the anterior and posterior rami of a spinal nerve
Where is the T4 dermatome?
male nipple
Where is the T10 dermatome?
umbilicus
What is a nerve plexus?
Networks of intertwined anterior rami
What does mixing of anterior rami via plexuses result in?
Less predictable shapes of the limb segments
What is the cervical plexus?
C1-C4 anterior rami
Posterior scalp, neck wall, diaphragm
What is the brachial plexus?
C5-T1 anterior rami
Upper limb
What is the lumbar plexus?
L1-L4 anterior rami
Lower limb
What is the sacral plexus?
L5-S4 anterior rami
Lower limb, gluteal region and perineum
What are the 5 named nerves of the brachial plexus?
Axillary nerve Median nerve Musculocutaneous nerve Radial nerve Ulnar nerve
Containing various mixes of the original 5 spinal nerves’ axons (C5,6,7,8,T1)
Describe sympathetic outflow.
- Originates from autonomic centres in the brain
- Passes down spinal cord in spinal cord lateral grey columns (lateral horns)
- Exits spinal cord with T1-L2 spinal nerves, in anterior rootlets/root (T1-L2 are the only segments of the spinal cord that have lateral horns)
- Travel to sympathetic chains running the length of vertebral column - paravertebral ganglion of the right sympathetic trunk
- Pass into all spinal nerves (anterior and posterior rami) and ‘hitch a ride’
- Pass into splanchnic nerves to eventually supply organs
What does the sympathetic axon leave the spinal cord in?
Anterior rootlets/root
How do parasympathetic axons leave the CNS?
Via cranial nerves III, VII, IX and X and via sacral spinal nerves
(craniosacral outflow)
