Peripheral Nervous System Flashcards
peripheral nervous system can be divided into…?
somatic and autonomic
sensory (afferent) carry information….. the CNS
towards
motor (efferent) carry information….. …..the CNS
away from
name the 12 pairs of cranial nerves
- olfactory
- optic
- oculomotor
- trochlear
- trigeminal
- abducens
- facial
- vestibulocochlear
- glossopharyngeal
- hypoglossal
- vagus
- accessory
are the cranial nerves part of the peripheral nervous system? Why or why not?
yes, because they are outside the brain
what is a plexus derived from?
lots of nerve fibres derived from spinal cord segments
if you damage a single spinal nerve segment, what will happen?
more than one muscle that is innervated by that nerve will be damaged
spinal nerves have a ……, peripheral nerves have a……
spinal nerves have a letter and number
peripheral nerves have a name
what are the cauda equina?
nerves around intevertebral foramina, come from a spinal cord segment, need to travel further to get to their exit point?
where do somatic nerves bring information from/to?
afferent - from the skin, skeletal muscle, and joints
efferent - convey information to skeletal muscles
what is a dermatome?
area of skin supplied by single spinal nerve
myotome
group of muscles innervated by a single spinal nerve
visceral afferent nerves carry information from the……
viscera (thoracic, abdominal, and pelvic organs)
visceral efferent nerves can be divided into…..
sympathetic and parasympathetic
sympathetic efferent nerves innervate what?
viscera and periphery (vasculature and sweat glands)
parasympathetic efferent nerves innervate what?
viscera only (organs)
what is a collection of cell bodies outside the CNS?
ganglion
what is a collection of cell bodies inside the CNS?
nucleus
what is a network of interconnecting nerves?
plexus
all afferent fibres (somatic and visceral) have their cell body where?
spinal ganglia
visceral efferent nerves synapse in a ……….. ganglion
peripheral (close to target organs, or in sympathetic trunks, or pre-aortic plexuses)
what are peripheral nerves arranged into?
fascisculi (bundles)
what is the name of the external vascular layer?
epineurium
what are the individual fascicles covered in?
perineurium
what are the individual axons covered in, outside the myelin sheath?
endoneurium
how do we classify the peripheral nerves?
2 classification systems:
one based on conduction velocity A, B and C (A is the fastest)
one based on axon diammeter (sensory only) uses roman numerals I-IV (I the largest diammeter
is myelination consistent across all nerves?
no, you can have no myelin - thickly myelinated axons
external sensory receptors are called
exteroreceptors
what do exteroreceptors detect?
pain
temperature
touch
pressure
internal sensory receptors are called….
proprioreceptors and enteroreceptors
proprioceptors detect
movement and joint position
enteroceptors detect
movement through gut and blood pH
chemoreceptors detect
chemicals
photoreceptors detect
light
thermoreceptors detect
temperature
mechanoreceptors detect
pressure
nociceptors detect
damage to tissue
if the pathway got to your brain you would feel pain although you would not feel it under anaesthetic for example even though they are active
what do propioceptors do?
tell us about the status of our joints within the body
alpha motor neuron is the upper or lower motor neuron?
Is ……polar?
Has its cell bodies where?
lower motor neuron
multipolar
ventral horn
where are upper and lower motor neurons located?
(Where do they each send their signals?)
Upper motor neurons are located in your brain and spinal cord.
(They send signals to lower motor neurons.)
Lower motor neurons are in your brain stem and spinal cord.
(When they get a signal from the upper motor neurons, they send another signal to your muscles to make them contract)
neuromuscular junction
specialised synapse between motor neuron and muscle fibre
which neurons are involved with the stretching of muscle?
sensory neurons
what do muscle spindles do?
detect changes in muscle length
golgi tendon organs
detect changes in TENSION in the tendons
joint receptors
found in joint capsules and detect the start and end of movement
motor unit
single motor neuron together with all the muscle fibres it innervates
smallest functional unit with which to produce force
how many motor neurons do humans have approximately?
420,000
how many skeletal muscle fibres do humans have approximately?
250 million
how many muscle fibres does a motor neuron supply on average?
600
stimulation of one motor unit causes…
contraction of all the muscle fibres in that unit
what happens if you cut back a nerve when it grows back?
it will innervate other muscles that are being innervated by other nerves, offsetting the balance
what is a reflex action?
an involuntary coordinated pattern of muscle contraction and relaxation elicited by peripheral stimuli
what is the periphery of the body?
the periphery of the body is the part that is away from the central or core regions
what are the exceptions to the noradrenaline neurotransmitter being released by post-ganglionic neurons in the sympathetic nervous system?
sweat glands and blood vessels
visceral sensory brings information back from core
which spinal and cranial nerves are involved?
T1-S2
S2-S4
cranial nerves IX and X (9 and 10)
visceral motor carries outflow of information to core and body wall,
what does it control?
pupils
sweat glands
salivary glands
heart muscle
airways
visceral motor involves outflow from which nerves?
thoracolumbar (T1-L2)
craniosacral (cranial nerves III, VII, IX and X [3, 7, 9 and 10])
the highest level of outflow from the spinal cord is at which spinal segment?
T1
How do the nerve fibres from T1 get to the skull
‘hitching a ride’ on arteries
pre-ganglionic neurons of the sympathetic system are where (in general) ?
spinal cord
what are the sympathetic trunks?
Where pre-ganglionic neurons go into after coming out of the spinal cord.
They are a paired bundle of nerve fibers that run from the base of the skull to the coccyx. The sympathetic trunk lies just lateral to the vertebral bodies for the entire length of the vertebral column.
why do sympathetic trunks have enlargements?
they have post-ganglionic neurons in them
How do sympathetic trunks appear in cadaveric specimens?
Where is their location?
Thin white nerves with enlargements
Inside chest, outside spinal cord
where are the cell bodies for pre-ganglionic sympathetic outflow between T1 and L2?
Where do they send their pre-ganglionic axons out to?
in the spinal cord, in an extra bit of grey matter called an intermediate horn halfway between posterior horn and anterior horn
mixed spinal nerve and then through either the white ramus communicans to a ganglion where it synapses with the post-ganglionic efferent neuron
gray ramus communicans contains …………. nerves
white ramus communicans contains …………. nerves
gray (contain unmyelinated nerves) ramus communicans
or
white ( contains myelinated nerves ) ramus communicans
where do the post-ganglionic neurons coming from T1-L2 go to after synapsing in the ganglion if they are carrying information to the skin?
either towards head and upper limbs or towards lower limbs
or straight out via gray ramus communicans to the part of the body between the upper and lower limbs
where do the post-ganglionic sympathetic neurons coming from T1-T4 go to after synapsing in the ganglion if they are carrying information to the heart?
Straight out to the heart, or up and out to the heart via the next superior ganglion in the sympathetic trunk
Reaches heart via cardiac plexus
where do the pre-ganglionic neurons coming from T3/5-L2 go to if they are carrying information to the viscera (not the heart) ?
through mixed efferent nerve bundle, white ramus communicans and ganglia without synapsing, goes straight through and continues out… synapsing in the pre-aortic ganglia with the post-ganglionic neuron
how does the aorta divide in the pelvis?
into 2, going off to pelvic organs
which cranial nerves are associated with parasympathetic outflow?
III, VII, IX, X
what is the transition of innervation of the abdominal viscera?
from supply by cranial nerve X and pelvis splanchnic nerves (S2-S4)
sacral parasympathetic outflow is via which nerves?
pelvic splanchnic nerves
cranial nerve III innervates which gland?
lacrimal gland
cranial nerve VII innervates which parasympathetic systems?
pupillary constriction
salivary glands
cranial nerve IX innervates which gland?
parotid gland
cranial nerve X innervates which parasympathetic systems?
heart
abdominal viscera
how many neurons in motor pathway?
where are their cell bodies?
It is composed of two neurons, the upper motor neuron and the lower motor neuron. The upper motor neuron has its cell body in the primary motor cortex of the frontal lobe and synapses on the lower motor neuron, which is in the ventral horn of the spinal cord and projects to the skeletal muscle in the periphery
https://open.oregonstate.education/aandp/chapter/14-5-sensory-and-motor-pathways/
what information do visceral sensory neurons bring back from the core? Which spinal nerves?
what do visceral motor neurons control?
sensory brings back information about pain, fullness, blood pressure
T1-L2, S2-S4, cranial nerves 9 and 10
controls pupils, sweat glands, salivary glands, heart muscle, airways
outflow from thoracolumbar T1-L2 and craniosacral outflow (3, 7, 9 and 10)
