ANATOMY- neurons and nerves Flashcards
what makes up the CNS?
-brain
-spinal cord
what makes up the PNS?
-all other nerve tissue not within CNS
-12CNs and 31 spinal nerves
(CNS= spinal cord and brain)
what do spinal nerves connect to?
-spinal nerves connect with the spinal cord
what do cranial nerves connect with?
-cranial nerves connect with the brain
basic unit of the nervous system?
-the neuron
where are the collection of nerve cell bodies in the CNS called?
-the nucleus
Cns= nuCleus
where are the collection of nerve cell bodies in the PNS located?
-in the ganglion
what are the two main types of neurons?
-motor neurons (multipolar)
-sensory neurons (Unipolar/ pseudounipolar)
what are the main type of neurons in the CNS and describe it
-Multipolar neurons
-they have 2 or more dendrites
-they are motor neurons
-they are efferent so their impulses move from the brain towards the body wall, body cavity or organ
what are the main type of neurons in the PNS and describe it
-unipolar/ pseudounipolar
-they have a double process
-these are sensory neurons
-they are afferent so their impulses move towards the brain
what are nerves?
-collections of axons surrounded by connective tissue and blood vessels
what are the 2 modalities of nerves?
- single modality (one of somatic motor, somatic sensory, special sensory, sympathetic, parasympathetic, or visceral afferent)
- mixed modality (somatic motor, somatic sensory and sympathetic all together in one nerve
what modality do ‘tracts’ tend to consist of?
-tracts tends to consist of single modality
single modality: one of the somatic motor, somatic sensory, special sensory, sympathetic, parasympathetic, or visceral afferent
name the spinal nerves
31 pairs
8 cervical: C1- C8
12 thoracic: T1-T12
5 lumbar: L1- L5
5 sacral: S1- S5
1 coccygeal: Co1
where are spinal nerves found?
only found in the intervertebral foramina
what do the spinal nerves connect with?
-they connect with structures of the soma via rami
-the spinal cord segment of the same number via roots and rootlets
What are A-G
A= right anterior/ventral rootlet
B= right anterior/ventral root
C= right posterior/dorsal rootlet
D= right posterior/dorsal root
E= posterior rami (smaller and connects to posterior wall)
F= anterior rami (larger and connects to anterolateral body wall)
G= spinal nerve
Where do motor axons in the spinal nerves pass?
-pass from anterior horn of spinal cord
-from anterior horn to anterior rootlets
-anterior rootlets to anterior root
-anterior root to spinal nerve
anterior horn > anterior rootlets > anterior root > spinal nerve
Where do sensory axons in the spinal nerves pass?
-all sensory axons pass from the spinal nerve
-from spinal nerve into the posterior root
-from the posterior root into the posterior rootlets
-from the posterior rootlets into the posterior horn of the spinal cord
spinal nerve > posterior root > posterior rootlets > posterior horn of the spinal cord
what do general sensory nerves supply?
-all structures
what do somatic motor nerves supply?
skeletal muscle
what do sympathetic nerves supply?
-the skin and the smooth muscle of arterioles
how is a dermatome innervated?
-area of skin supplied with sensory innervation from a single spinal nerve
-also supplies sensory innervation to deeper structures
-innervation of skin by adjacent spinal nerves shows overlap
how is a myotome innervated?
-the skeletal muscles supplied with motor innervation from a single spinal nerve
-may be deep to dermatome of same spinal nerve, but not always
What dermatome is the nipple?
T4
what dermatome is the umbilicus?
T10
what dermatome are the posterior scalp, neck and shoulder?
C2-C4
what dermatome are the upper limb?
C5-T1
what dermatome are the lower limb, gluteal region and perineum?
L2- Co1
what is a nerve plexus?
-intermingled anterior rami from a number of adjacent spinal nerves
what spinal nerves are involved in the cervical plexus and what does this cover?
C1-C4
-posterior scalp, neck and diaphragm
what spinal nerves are involved in the brachial plexus and what does this cover?
C5-T1
-upper limb
what spinal nerves are involved in the lumbar plexus and what does this cover?
L1-L4
Lower limbs
what spinal nerves are involved in the sacral plexus and what does this cover?
L5-S4
Lower limb, gluteal region and perineum
what levels of the sympathetic chain have lateral horns?
T1- L2
does the sympathetic chain pass through anterior or posterior rootlets/ roots?
anterior as sympathetic chain provides motor innervation
what spinal nerves are part of the sympathetic chain?
-all of them
however only T1-L2 have lateral horns meaning that the signals can just by pass and go straight from the spinal cord through these levels
what 4 routes does the sympathetic chain take?
-can ascend and then synapse (innervation of neck and upper limb)
-can synapse at the level of entry (innervation of middle trunk)
-can descend and then synapse (innervation of lower limb)
-can pass through sympathetic trunk without synapsing to enter an adominopelvic splanchnic nerve (for innervation of abdominopelvic viscera only)
are para or pre vertebral ganglia involved in the sympathetic innervation of the heart?
cervical paravertebral ganglia
are para or pre vertebral ganglia involved in the sympathetic innervation of the lungs?
upper thoracic paravertebral ganglia
are para or pre vertebral ganglia involved in the sympathetic innervation of the abdominopelvic organs?
in the prevertebral ganglia
where do the presynaptic parasympathetic axons leave the CNS?
Presynaptic parasympathetic axons leave the CNA via:
-cranial nerves III, VII, IX + X
-sacral spinal nerves
Where do the presynaptic parasympathetic axons travel to reach the eye?
-they leave the CNS via CN III (oculomotor) and travel through the ciliary ganglion to reach the eye
where do the presynaptic parasympathetic axons travel to reach the lacrimal and salivary glands?
-they leave the CNS via CN VII (facial) and CN IX (glossopharyngeal) and travel through the parasympathetic ganglia in the head to reach the lacrimal and salivary glands
where do the presynaptic parasympathetic axons travel to reach the organs of the neck, chest, abdomen and mid gut?
-they leave the CNS via CNX (vagus) and travel to reach the organs of the neck, chest, abdomen and mid gut
where do the sacral spinal nerves travel to reach the organs of the hindgut, pelvis and perineum?
they leave the sacral spinal nerves (S2, S3, S4) and travel to reach the hindgut, pelvis and perineum
