structure & function of nervous system Flashcards
what do sensory nerves do?
allow us to sense our environment (internal environment like heartbeat, pain of muscles etc and also external environment like someone has touched us, a smell etc)
what are special senses?
things like taste, touch, sight, hearing etc
what do motor functions do?
allows us to react & respond (can be voluntary or involuntary like glands or hormones)
what are the 2 ways the nervous system can be divided?
- split down anatomically
- also can be split functionally
what is the CNS?
central nervous system
= brain & spinal cord
brain & spinal cord = also called central controller
what is the PNS?
peripheral nervous system
= all other tissues not within CNS
= spinal nerves (connect spinal cord)
= cranial nerves (connect with brain)
= autonomic nerves (organs, smooth muscle, glands, visceral afferents, sympathetic nerves, parasympathetic nerves)
= wiring
what does afferent mean?
fancy word for sensory
what does efferent mean?
fancy word for motor
what is visceral afferent?
organ sensory
what is the structure of a neuron?
has main cell body with nucleus and dendrites and other long processes extending out body
cell body = have connections to other cell bodies, they send & receive electrical impulses
what are dendrites?
extensions that just receive signal and conduct them towards the body (increase surface area for reception)
what are the long processes coming off cell body of neuron?
nerve fibres/axons = send signal away from cell body
axons - can be up to metre long but can be in sequence & synapse so cover entire length of body
what is the purpose of myelin sheath?
makes conduction easier & faster (cover lots of nerves but not all)
what is a collection of nerves called in the CNS?
nucleus
what is a collection of nerves called in the PNS?
ganglion
what are nerves made up of?
1 nerve is made up of bundles of axons or nerve fibres (axons & nerve fibres the same thing)
how do travelling bundles of axons leave original nerve?
they leave as branches at like limbs for example
what is modality?
type of nerve fibre/axon
what are named nerves?
generally larger nerves supplying body wall, body cavities & organs
what are the 6 different modalities?
- somatic sensory function = carries sensory information from soma
- somatic motor function = nerve fibre from brain or spinal cord and tells muscle to contract
- special sensory function = carry special sensations back to spinal cord & brain
- visceral afferent function = carry sensory information back from organs
- sympathetic function = motor going to smooth muscles & cardiac muscles etc
- parasympathetic function = motor going to smooth muscles & cardiac muscles etc
what is soma?
body wall
what is viscera?
organs
what modality do nerves tend to have?
they tend to be mixed as nerves = bundles of axons (axons have different types) - some nerves have same function but unlikely
each axon carries 1 type
what direction to motor (efferent) nerves run?
action potential towards body wall, body cavity or organs
- from CNS →PNS
what direction to sensory (afferent) nerves run?
action potential towards brain
- from PNS →CNS
what is gyri?
singular = gyrus
- it’s the ridge (bumps) of the brain
what is sulci?
singular = sulcus
- it’s the dips of the brain
how is the brain divided?
into same regions as bone above
- so occipital at back, temporal at sides, frontal at front and parietal on top towards back
what is a good trick for identifying anterior vs posterior of a brain?
look for temporal lobe as always points anteriorly (forward)
how many cranial nerves are there?
12 pairs
what is the trick for remembering modality of cranial nerves?
Some Say Marry Money But My Brother Says Big Brains Matter More
S= sensory
M = motor
B = both
what is name, number (in roman numeral) and modality of cranial nerve 1?
- cranial nerve I
- olfactory nerve (smell)
- sensory (special)
what is name, number (in roman numeral) and modality of cranial nerve 2?
- cranial nerve II
- optic nerve (sight)
- sensory (special)
what is name, number (in roman numeral) and modality of cranial nerve 3?
- cranial nerve III
- oculomotor nerve (motor)
- motor
what is name, number (in roman numeral) and modality of cranial nerve 4?
- cranial nerve IV
- trochlear nerve (moves 1 muscle of the eye)
- motor
what is name, number (in roman numeral) and modality of cranial nerve 5?
- cranial nerve V
- trigeminal nerve
- both
what is name, number (in roman numeral) and modality of cranial nerve 6?
- cranial nerve VI
- abducent nerve (abducts eye)
- motor
what is name, number (in roman numeral) and modality of cranial nerve 7?
- cranial nerve VII
- facial nerve (supplies muscle of facial expression)
- both
what is name, number (in roman numeral) and modality of cranial nerve 8?
- cranial nerve VIII
- vestibulocochlear nerve (hearing & balance)
- sensory (special)
what is name, number (in roman numeral) and modality of cranial nerve 9?
- cranial nerve IX
- glossopharyngeal nerve (tongue & pharynx)
- both
what is name, number (in roman numeral) and modality of cranial nerve 10?
- cranial nerve X
- vagus nerve (what is name, number (in roman numeral) and modality of cranial nerve)
- both
what is name, number (in roman numeral) and modality of cranial nerve 11?
- cranial nerve XI
- spinal accessory nerve (comes by spine)
- motor
what is name, number (in roman numeral) and modality of cranial nerve 12?
- cranial nerve XI
- hypoglossal nerve (underneath the tongue)
- motor
when looking at underneath of brain - what is a way you can know which nerve is which?
go from 1 -12
- when you go anterior to posterior and medial to lateral
what is the brain stem made up of?
- mid brain (bump bit)
- pons
- medulla oblongata
what cranial nerves are in anterior cranial fossa?
only cranial nerve I
what cranial nerves are found in middle cranial fossa?
CN II, III, IV, V (all 3 types of 5), VI
what cranial nerves are found in posterior cranial fossa?
CN VII, VIII, IX, X, XI, XII
is sensory or motor nerve going into/out of cranial cavity?
sensory = into cranial cavity (cause needs to tell brain message)
motor = out cranial cavity (cause needs to action to muscle etc)
what cranial nerve goes through cribriform plate of ethmoid bone?
cranial nerve I in anterior cranial fossa
what cranial nerve comes through optic canal?
cranial nerve II (middle cranial fossa)
what cranial nerves comes through superior orbital fissure?
CN III, IV, V1 (one of 3 cranial nerve 5) & VI
- middle cranial fossa
(3, 4, 5, 6)
what cranial nerve comes through foramen rotundum?
cranial nerve V2 ( 2 out of 3 of cranial nerve 5)
- middle cranial fossa
what cranial nerve comes through foramen ovale?
Cranial nerve V3 (3rd of the 3 cranial nerve 5)
- middle cranial fossa
what cranial nerve comes through internal acoustic meatus?
cranial nerve VII & VIII
- posterior cranial fossa
what cranial nerve comes through jugular foramen?
cranial nerve IX, X & XI
- posterior cranial fossa
what cranial nerve comes through hypoglossal canal?
cranial nerve XII
what comes through foramen magnum?
spinal cord
what is spinal cord protected by?
vertebral canal
what are 2 enlargements of spinal cord?
- cervical
- lumbasacral
= enlarged as a lot of nerve tissue since control upper & lower limbs
how many pairs of spinal nerves?
31 pairs
= spinal connects bilaterally with spinal nerves
how many cervical spinal nerves are there?
8
how many thoracic spinal nerves are there?
12
how many lumbar spinal nerves are there?
5
how many sacral spinal nerves are there?
5
how many coccygeal spinal nerves are there?
1
when does spinal cord end?
at L1/L2 inter vertebral disc level
= called conus medullaris (looks like cone shape)
how are spinal nerves named?
named according to vertebrae ABOVE it
EXCEPTION!! = in cervical region they’re named according to vertebrae BELOW it
is adult vertebral column or adult spinal cord longer?
adult vertebral column is longer than the spinal cord (bony bits are longer than the spinal cord)
what is cauda equina?
since bones are getting bigger and longer at end of vertebral column, nerves have to come down longer to get out at correct place →this means collection of nerves at end (also called horse tail)
what is the only bit of nerve that is actually spinal nerve?
located only within the intervertebral foramina (in the little gap between inter vertebral foramen)
what do spinal nerves supply?
the soma (body wall)
what are rami?
what spinal nerves turn to to connect with structures of the soma
(away from spinal cord)
what are roots & rootlets?
nerves that the spinal cord turns into when going into spinal cord
(towards spinal cord)
- roots come together to make spinal cord
out of posterior/anterior rami/roots which are biggest and why?
anterior rami = much bigger as do everything else, come all the way round and supply body wall
what does each pair of spinal nerves supply?
just 1 strip stroma
what does posterior rami supply?
supply small posterior strip
what does anterior rami supply?
supply the remainder of the posterior part, the lateral and the anterior parts of the strips = supply all of the limbs
what do dermatomes show?
shows strip that spinal nerves is supplying = area of skin supplied by both the anterior & posterior rami of spinal nerve
what are the dermatomes i should know?
T4 = nipple
T10 = umbilicus
what are plexuses?
= intertwining of nerves (only anterior rami are involved, posterior rami don’t participate in cervical plexuses)
what are types of plexus and what do they supply?
- cervical plexus, C1-4
(posterior scalp, neck wall…and diaphragm) - brachial plexus, C5-T1
(upper limb) - lumbar plexus, L1-4
(lower limb) - sacral plexus, L5-S4
(lower limb, gluteal region & perineum)
= intertwining of nerves
what are senses sensed by mechanoreceptors?
- coarse touch
- fine touch
- vibration
- proprioception
what are senses sensed by thermoreceptors?
- temperature
what are senses sensed by nociceptors?
pain
what is somatic nervous system made up of?
- soma (head & neck walls, chest wall, back, diaphragm, abdominal wall, pelvic wall, limbs)
- structures (skin, fascia, skeletal muscle, skeleton, internal lining of body cavities)
what type of pain would a patient describe for somatic pain?
sharp or stabbing - localised (would be able to say where)
what is the general route of somatic sensation if sensory stimulation on thigh?
- somatic sensory mechanoreceptors in L2 dermatome are stimulated
- action potentials conducted along axons within the L2 anterior ramus
- the same L2 axons weave their way through the lumbar plexus to the L2 spinal nerve
- APs conducted via the same axons which pass through the dorsal (posterior) root ganglion, the dorsal (posterior) roots and dorsal (posterior) rootlets
- APs arrive at the posterior horn of the L2 spinal cord segment
- AP’s cross over the midline and then ascend towards the brain
what is the general route of somatic sensation after sensory stimulation? (from brain -> action)
- somatic motor axons cross over in brainstem then descend to the anterior horn
- APs conducted along axons within anterior rootlets, then anterior roots, then into spinal nerves
- APs conducted along axons in named nerves of lumbar plexus
- Synapse onto skeletal muscle of lower limb
- skeletal muscles contract and move the lower limb
what happens in spinal reflexes?
- reflex is extremely rapid
- miss out pathway to brain
- involuntary response
sensation travels through posterior root/rootlets but need to quick so we miss out connection to brain and there’s quick connection that goes to motor nerve for response
what is included in autonomic nervous system?
- viscera e.g. heart, lungs, kidney
- glands e.g. muscous, sweat, salivatory
- smooth & cardiac muscle
- external lining of organs
where is autonomic nervous system found?
- internal organs in body cavities = chest cavity, pelvic cavity, abdominal cavity
- body wall organs = sweat glands, arrector smooth muscle, arterioles
what sensations can be detected by autonomic nervous system?
- touch, temperature, pain
- ischaemic
- colicky (comes & goes)
what type of pain would patient describe if autonomic pain?
dull, achy, nauseating - poorly localised
what dual motor control is involved in ANS?
many organs have both sympathetic & parasympathetic nerve supply
= both motor controls
= like accelerator or brake
what are effects of sympathetic division? (7)
fight or flight response - supplies all internal organs, body wall organs, arterioles
pupils - dilate (so you can see clearly)
heart rate - increase (try to pump blood around body)
lungs - bronchioles dilate (more oxygen)
GI tract - motility reduced (don’t want to waste time digesting)
liver - released glucose (for energy)
adrenal gland - adrenalin
arterioles - dilate(muscles) or constrict (skin) →so skin feels cold and looks pale because want blood to go to muscles not skin
what is sympathetic outflow?
thoratholumbar outflow (between T1&L2)
= control central in brain starts to provide sympathetic innervation →passes down spinal cord → only exits between T1-L2 →travels to sympathetic chain and can leave there and then get higher or lower →gets a ride with arteries (runs along surface to get to where it needs to go)
sympathetic axon direction of travel?
leaves spinal cord in anterior rootlets or roots as sympathetic type of motor
what are effects of parasympathetic division?
=rest & digest - often supplies same organs as sympathetic, doesn’t supply body wall organs or arterioles
Pupils - constrict
Heart - rate decreases
Lungs - bronchioles constrict
GI tract- motility is increased
Liver - glucose synthesis
Bladder – sphincter relaxes
what is parasympathetic outflow?
= craniosacro
cranial nerves (3,7,9, 10 have parasympathetic innervation)
S2, S3, S4 - carry parasympathetic innervation
- lots of ganglia in head
- vagus nerve important for carrying parasympathetic innervation
what does vagus nerve supply?
organs of the neck, chest and abdomen as far as the mid-gut
what does parasympathetic ganglia in head supply?
to lacrimal gland and salivary glands
what does sacral spinal nerves do in parasympathetic outflow?
‘carry’ parasympathetic axons to the hindgut, pelvis and perineum
