apk exam 3 Flashcards
nervous system
the master controlling/communicating syst of the body
- rapid, specific signals cause IMMEDIATE responses by the body
- employs electrical & chem. means to send messages from 1 cell to another
- faster than endocrine
endocrine system
communicates by chemical messengers, hormones, secreted into the blood
- takes longer for hormones in bloodstream to get to target organ
3 overlapping functions of the nervous system
- sensory function: monitors changes inside and outside body; sensory info moves along a neuron, towards the brain
- integration function: CNS receives and interprets sensory input & makes a decision for axn
- motor function: motor neurons elicits response by activating effector organs
tip: SIM
central nervous system (CNS)
brain + spinal cord
peripheral nervous system (PNS)
- all nervous tissue outside of CNS
- cranial & spinal nerves that can have sensory/motor functions
- connects CNS to rest of the body (muscles, glands, sensory receptors)
- 2 branches: afferent and efferent division
afferent (sensory) division of PNS
- made of somatic and visceral sensory nerve fibers
- conducts impulses from receptors to the CNS
efferent (motor) division of pNS
- made of motor nerve fibers
- conducts impulses from the CNS to effectors (muscles & glands)
- 2 types: somatic nervous system & autonomic
somatic nervous system
- part of PNS efferent division
- somatic motor - voluntary control
- conducts impulses de CNS to skeletal muscles
autonomic nervous system
- pt of PNS efferent division; a system of motor neurons that innervate the smooth muscle, cardiac muscle, and glands of the body
- autonomic inactivation or inhibition of the viscera; visceral motor (involuntary!!)
- conducts impulses de CNS to cardiac, smooth muscles, and glands
- sympathetic and parasympathetic divisions
sympathetic nervous system (thoracolumnar division of ANS)
mobilizes body syst during activity - fight or flight
- responds to stresses (physical and emotional)
- increase body functions that support physical activity
- decrease digestive & urinary function
- PNS, efferent, autonomic
parasympathetic nervous syst
- PNS, efferent, autonomic
- rest & digest
- conserves E, restore body E, promotes house-keeping functions during rest
- decr body functions that support physical activity
- incr digestive and urinary function
nervous tissue
- made of 2 types of cells: composed of excitable neurons and non-excitable cells, neuroglia
special characteristics of neurons
- conductivity: able to send elect. signals from 1 body pt to another called action potential/nerve impulses
- extreme longevity: neurons can live and funct. for lifetime
- can’t divide: cannot replace themselves if destroyed (few exceptions)
- high metabolic rate: require constant supply of o2 and nutrients
tip: Conie meticulously long divides (conductivity, metabolism, longevity, divide)
neuron structure
- cell body: aka soma/neurosoma; where nucleus and organelles are
- dendrites: extensions from cell body; act as receptive regions; signals then move down to cell body
- axon hillock: signal moves from cell body to here; tapered area
- axon: where signal travels away from cell body; acons can be really short or really long
- schwann cells: neuroglia; insulate axon; forms myelin sheath - sheath is not continuous
- node of Ranvier: gaps between myelin sheath
- terminal arborization/axon terminal: have terminal boutons; secretory region
structural classification of neurons
- multipolar
- bipolar
- unipolar
multipolar neuron
many processes extend de the cell body; all are dendrites except for a single axon
- most common
bipolar neuron
2 processes extend de the cell bod; 1 is a fused dendrite and the other is an axon
- ex: commonly are sensory neurons in eyes, nose, nasal cavity
unipolar neuron
1 process extends de the cell bod and forms central & peripheral processes. which together comprise an axon
functional classfication of neurons
grouped according to the direction in which nerve impulse travels relative to the CNS
- afferent: towards CNS = SENSORY
- efferent: away from CNS = motor
- interneurons = within CNS = association
synapse
sites of communication b/w 1 cell to another
- 3 types:
- axosomatic
- axodendritic
- axoaxonic
tip: SAD
presynaptic neuron
neuron tht is sending the signal to another cell
postsynaptic neuron
neuron tht is receiving signal from another cell
axosomatic
axon synapses with the cell body
axodendritic
synapse b/w axon terminal and the dendrites of the postsynaptic neuron
axoaxonic
synapse b/w axon terminal of the presynaptic neuron and the axon terminal of the postsynaptic neuron
components of synapse
- axon terminal
- synaptic vesicles; whatever they contain will be released via exocytosis; ex: neurotransmitters
- nerve impulses - travel down from cell body to axon terminal -> signal exocytosis of neurotransmitters into SYNAPTIC CLEFT -> neurotransmitters bind to receptors on receiving side/postsynaptic cell
neuroglia
- similar to neurons; have processes
- different from neurons: non-excitable, don’t respond to electrical signals; smaller, more numerous (10:1), can divide thru/o life
- cover all non-synaptic surfaces of neurons
- 4 types of CNS neuroglia
- 2 types of PNS neuroglia
CNS neuroglia
- astrocytes
- microglial
- ependymal cells
- oligodendrocytes
tip: observe epic astroids through microscopes
astrocytes
- most abundant cns neuroglia
- incr neurotransmitter reuptake
- signal increased blood flow to active brain regions; they attach to blood vessels
- controls the ionic environment around neurons
- star-shaped
microglial cells
cns neuroglia; least abundant glial cells
- smallest gial cells
- macrophages of the CNS - eat up microorgs/pathogens
ependymal cells
cns neuroglia
- simple, ciliated epithelium
- forms a permeable lining of the ventricles, aka brain cavities filled w/ cerebrospinal
ogliodentrocytes
- cns neuroglia
- have processes tht form myelin sheaths around long axons in the cns
- electrically insular cns axons
- nodes of ranvier present
- looks like octopus - coils and forms insulatory sheaths - sheaths not continuous
pns neuroglia
- satellite cells: cover around cell body of neuron
- schwann cells: form myelin sheath
- different from oligodendrocytes bc they don’t have processes - the ENTIRE cell, itself, coils/wraps around axon
- they surround ALL axons in PNS, but only some axons have myelin sheath; ex: if we have 20 axons, schwann cells can just lightly wrap/bundle these together -> this is not considered a myelin sheath bc the coiling is not layered
- nodes of ranvier present along axon
myelin sheaths
concentric layers of plasma membrane of Schwann cells or oligodendrocytes tightly wrapped
- insulate axon; makes electrical conductivity faster
myelinated axon of PNS process
- schwann cell wraps around axon
- it wraps around the axon; wrapping plasma membrane loosely around in successive layers
- cell cytoplasm is forced from b/w the mmrbanes. the light membrane wrapping surrounding the axon forms the myelin sheath
- organelles and nucleus get pushed to the outside regions
diseases of myelin sheath
- degenerative disorders
- multiple sclerosis
- tay-sachs
multiple sclerosis
- neuroglia degenerate
- myelin replaced by hard scar tissue
- nerve conduction disrupted - double vision, tremors, numbness, speech defects
- can get various symptoms depending which myelin is affected - PNS or CNS
tay-sachs disease
hereditary; in Jewish infants
- abnormal accumulation of glycolipids in myelin sheath
*disrupts conduction of nerve signals
*blindness, loss of coordination, and dementia
*fatal b4 age 4
nonmyelinated axons in PNS
- schwann cell surrounds multiple axons, but doesn’t have concentric layers/tight coils so no insulation
conduction speed of nerve fibers
- speed @ which nerve signal travels along a nerve fiber depends on 2 factors:
1. diameter of fiber (larger = faster)
2. myelinated = faster - signal conduction occurs along the surface of a fiber
*lrgr fibers have more surface area and conduct signals more rapidly
*myelin further spreads signal conduction
grey and white matter of the cns
grey matter: butter-fly shaped; consist of short nonmyelinated interneurons, neuroglia, and cell bodies of interneurons and motor neurons
* ex: cerebral cortex, central cavity
white matter: groupings of myelinated axons; fiber tracts of myelinated and nonmyelinated axons; consist of neuroglia
*DO NOT RELATE TO PNS AT ALL
pns nerves
- cable-like ORGANS with parallel arranged axons
- around an entire nerve, we have a fibrous connective tissue sheath, called EPINEURIUM
- within the nerve, we have bundles of axons called FASICLCES
- PERINEURIUM encase fasiclces
- within fasicles, we have individual axons that are covered by its own ENDONEURIUM
(very similar to what occurs with muscle tissue)
integration of the pns and cns
- they can work together: info from peripheral goes to central and then central tells what peripheral can do
- ex: reflexes
REFLEX = rapid, automatic, motor response to stimuli
reflex arc involved
reflex
rapid, automatic, motor response to stimuli
- 4 important properties of a reflex:
- require stimulation: reflexes are not spontaneous axns, but r responses to sensory input
- quick: involve few, if any, interneurons and minimum synaptic delay
3.: involuntary: occur w/o intent and difficult to suppress; automatic response
4.: stereotyped: occur essentially the same way every time
tip: stick stereo in quick
stick = put something in = input/stimulation
STEREOtyped
INvoluntary
quick
reflex arc
- receptor
- sensory neuron
- integration center
- motor neuron
- effector
ex: getting pricked by needle
receptor senses pain, sensory neuron brings signal to spinal cord; spinal cord = integration b/w pns and cns; interneurons synapse with motor neuron to send signal to effector; effector carries out axn, like contracting muscles to remove finger
knee-jerk (patellar) reflex
- ex of a stretch/tendon reflex
- dr taps on ur patellar tendon -> hammer pulls tendon a bit
- sensory/strecth receptor: quadriceps senses slight pull
- sensory afferent nueron: sends signal to spinal cord; DIRECTLY SYNPASES WITH MOTOR EFFERENT - does not to go all the way to the brain
- motor efferent neuron: sends signal to quadriceps/effector
- effector: quadricepts contract and extends the knee
- how many neurons and synapses are involved?
- 2 neurons - 1 afferent, 1 efferent
- 1 synapse
thus, this is called a monosynaptic stretch reflex
- reciprocal inhibition also occurs
reciprocal inhibition
reflex phenomenon that prevents muscles from working against e/o by inhibiting the antagonist
- ex: during knee reflex, ur hamstring are inhibited while quadriceps contract
types of reflexes
- stretch
- withdrawal
flexor/withdrawal reflex
- contraction of flexor muscles resulting in the withdrawal of a limb from an injurious stimulus
- ipsilateral reflex arc: communication b/w sensory and motor neurons occur on same side of spinal cord
- ex: u touch a thumb tack and u quickly pull away
- sensory receptor detects prick
- sensory afferent neuron sends signal to spinal cord
- interneuron: sensory afferent neuron synapses with interneuron, which synapses with motor efferent neuron
- motor efferent neuron: sends signal to effector
- effector: carry out action; biceps contract
- ex of polysynaptic reflex; 3 neurons, 2 synapses
do all reflexes have to cause a response to the same side of the body as where the stimulus occurred?
no
crossed extension reflex/contralateral reflexes possible
- ex: u go to the beach and step in something sharp- 1 foot lifts off/withdraws, but the other needs to contract & extend to keep u balanced or else u fall
directional terms for the CNS
- rostral: towards the snout
- caudal: towards tail; in humans, caudal does not mean our back, but the end of our spinal cord, near the tail bone
major divisions of the brain
- cerebrum
- diencephalon
- cerebellum
- brain stem
cerebrum
largest part of the brain, over 80% of brain’s mass -> left and right hemisphere
- cerebral hemispheres; cortex, white matter, basal nuclei
- wrinkles incr SA
- associated with lateral ventricles
diencephalon
includes thalamus, hypothalamus, and epithalamus
Tip: THE
- also includes the retina
- associated with the third ventricle
cerebellum
2nd lrgst part of the brain; underneath diencephalon
associated with the 4th ventricle
- similar arrangement as the cerebrum
*2 hemispheres
*cortex: grey matter with many folds called FOLIA
*white matter: tracts called ARBOR VITAE
*deep gray matter
*vermis: connects 2 hemispheres of cerebellum
brain stem
rostral continuation of the spinal cord; consists of the:
- medulla oblongata
- pons
- midbrain: associated with the cerebral aqueduct
medulla and pons associated with 4th centricle
brain ventricles
- cerebrospinal fluid-filled spaces in the brain; continuous w/ e/o and the central canal
- lined with ciliated ependymal cells
- provide CSF to nearby brain regions
spinal cord
associated with central canal; pt of CNS
cerebrospinal fluid
- plasma filtrate; nourishes and removes waste
- cushions brain during jolting
- allows brain to be buoyant
anatomy of ventricles
- lateral ventricle: we have 2 total, 1 for each hemisphere (looks like a ram’s horn anteriorly); largest ventricles
- third ventricle: lateral vent. flows into this one; have 1 on each side of cerebrum; small middle section inferior to lateral ventricle; looks like a rooster’s head + beak
- cerebral aqueduct: more caudal, small
- fourth ventricle: small canal
**LOOK UP PICS SO U KNOW HOW TO ID THEM
cerebrum gross anatomy
- cerebral cortex: most superficial aspect of the cerebrum; gray matter
- deep gray matter: deeper, short nonmyelinated axons
- cerebral white matter: elongated areas of axons; vast majority are myelinated axons even tho u have unmylienated ones
- fissure: deep groove, divides brain in half
- sulcus: groove
- gyrus: folds/peaks
lobes of the brain
- frontal
- parietal
- temporal lobe
- occipital
- insular lobe: need to take off frontal and temporal lobe to see this bc it’s deep within the brain
longitudinal fissure
splits brain into right and left hemispheres
main sulci
- central sulcus: divides frontal and parietal lobe
- parietal-occipital sulcus: separates pariet. and occip. lobe
- lateral sulcus: separate temporal lobe from other lobes
important gyri
- precentral gyrus: fold that comes before the central sulcus, part of the frontal lobe
- postcentral gyrus: after central sulcus; part of parietal lobe
have specific functions in motor and sensory commands
frontal lobe
- motor command
- has precentral gyrus, primary motor cortex
parietal lobe
- has postcentral gyrus where the primary somatosensory cortex is
- skin sensations: pressure, heat, cold, pain; info from joints and muscles - muscle stretch info
occipital lobe
- has primary visual cortex
temporal lobe
- has primary auditory cortex
somatotopy
a mapping of areas of the body associated with specific areas of the brain
- is an upside-down map of the contralateral side of the body - this is bc left side of body is controlled by right side of brain and vice versa
- amt of cortex devoted to a given body region is proportional to either the # of muscles and motor units there or the # of receptors for a particular body part
- ex: on motor side, face and hand is enlarged bc u have more motor neurons associated with these areas bc u do more movements here
cerebral white matter
3 types
1. commissural fibers: fibers move b/w right and left hemispheres, connecting them; largest structure formed by these = corpus callosum
- associational fibers: intrahemispheric; they travel to different parts of a hemisphere, but they don’t cross over and stay in 1 hemisphere
- long or short
- projection fibers: move b/w cerebral cortex and lower CNS areas; verticle fibers
cerebral deep grey matter
- basal nuclei (nuclei = cluster/grp of cell bodies)/ganglia
*initiates and terminates body mvnts
*suppresses unwanted mvnts
*dont need to know these bottom ones
- basal forebrain nuclei
- claustrum
- amygdala
diencephalon
- thalamus: egg-shaped; 1 in each hemisphere; relay station
- hypothalamus: directly inferior to thalamus
- epithalamus aka pineal gland - releases melatonin (regulates sleep); also includes posterior commissure
thalamus
pt of diencephalon
- “gateway to the cerebral cortex” bc it is a relay center; nearly all input to the cerebrum passes by way of synapses in the thalamic nuclei, filters info on its way to cerebral cortex
- ventral posterolateral nuclei = relay sensory
- medial geniculate body = relay auditory
- lateral geniculate body = relay visual
tip: Later, VIew Victoria SEcret Model AUDitions
hypothalamus
controls homeostasis: hunger, thirst, body temp, release of hormones from pituitary gland
- forms the lateral walls of the 3rd ventricle
- have mammillary bodies on inferior side (2 small projections)
- infundibulum: where pituitary gland hangs off of; connects hypothalamus to pituitary gland
optic chiasm
where optic nerves cross over , looks like an X
interthalamic adhesion
little tissue that connects the 2 thalamus on either side of brain
midbrain
- cerebral peduncles
- cerebral aqueduct
- corpora quadrigemina
cerebral peduncles
composed mostly of motor axons from the cortex to the cerebellum and spinal cord
- look like columns/pillars supporting the cerebrun
- located ventrally/anteriorly
cerebral aqueduct
passes thru the center of the midbrain
- skinnier canal that will move the CSF from 3rd ventricle -> 4th ventricle
corpora quadrigemina
nuclei that form 4 bumps on the dorsal midbrain
- superior colliculi - visual reflexes; ex: snap neck to look at something when u detect it in ur peripheral region
- inferior colliculi - auditory reflexes; ex: turning ur head quickly when u hear a loud sound
pons
like a “bridge”
- connect brain step to cerebellum
- viewed ventrally as superficial, transverse fibers
- superior pontine border & inferior pontine border = ends of the pons
medulla oblongata
- key to homeostasis
- continuous with superior aspect of the spinal cord
- from the foramen magnum to inferior pontine border
- pyramids - motor tracts that form bulges on the anterior surface of the medulla; send info down spinal cord to effector; site of MOTOR DECUSSATION only (not sensory)
- olives - nuclei that form bulges just lateral to the pyramids; sensory relay station
motor decussation
crossing over point for motor information; in pyramids of medulla oblongata
lobes and functions of the cerebellum
- anterior lobe
- posterior lobe
- flocculonodular node: coordination of head and eye movements
- posterior and anterior lobes important for motor coordination of trunk and limbs; make sure you’re coordinating your body movements; balance; smoothing out movements
meninges
protective coverings around brain and spinal cord; made of CT tissue
3 layers:
- dura mater: most superficial matrix
- arachnoid mater: middle meninx
- pia mater: deepest meninx
protective coverings of the cns
- skull: protect brain
- vertebrae: protect spinal cord
- meninges
dura mater
has 2 layers
- periosteal
- meningeal layer: below periosteal layer
- both layers stuck together; only come apart when they form sinuses
meninges: spaces and septa
- superior sagittal sinus: lrgst sinus in the brain
- subdural space: b/w dura and arachnoid mater
- subarachnoid space; lots of blood vessels within; CSF fills up this area a lot
- arachnoid granulation: open up and allow CSF to get drained into the sinuses
- dura mater: periosteal, meninges
- arachnoid mater
- pia mater
- falx cerebri: ct layer that fuses together and moves down the longitudinal fissure
- CSF is found inside and outside the brain
- CSF gets deposited into dural venous sinuses around the brain
falx cerebri
separates the cerebral hemispheres
falx cerebelli
separates the cerebellar hemispheres
tentorum cereblli
- like a tent
- separates the cerebellum from cerebrum
spinal cord
sensory and motor innervation of the whole body (inferior to the head)
- 2-way conduction pathway b/w brain and body (inferior to the head)
- major integration center for reflexes
- bc the spinal cord doesn’t extend to the. endof the spinal column, spinal cord segments are typically located superior to su respective vertebrae
- spinal cord ends at L1 or a little beyond
- gives ride to 31 pairs of spinal nerves
gross anatomy of spinal cord
- cervical, thoracic, lumbar, sacral spinal nerves
- allow spinal nerves to exit out - SPINAL NERVES ARE ONLY PT OF THE PNS, NOT CNS
- cervical enlargment: slight bulge in cervical region
- dura and arachnoid mater: thoracic region
- lumbar region: lumbar enlargment, conus medullaris (most caudal structure of the CNS, end of spinal cord), cauda aquina (spinal nerves; pt of PNS)
- filum terminals: extension of pia mater of the meninges; acts as anchor for spinal cord
gross anatomy of spinal cord and nerve roots
- gray matter: neuron cell bodies and axons with little myelin
*gray commissure (cross bar of the H/butterfly shape) connects both sides
*dorsal horn, ventral horn, lateral horn: how to tell ventral. vs dorsal: gray matter on dorsal side/backside extends right to the edge of the spinal cord; ventral side: gray matter doesn’t touch the front of the spinal cord; lateral horn only associated with the thoracic segments of the spinal cord - white matter: abundantly myelinated axons
*dorsal, ventral, lateral funiculus/column: elongated column; area outside of H/butterfly shape - nerve roots: pt of PNS not CNS
- central canal: hole @ center of spinal cord
- dorsal median sulcus
- ventral median fissure: deeper than sulcus, on front side
- meninges & it’s 3 layers
spinal cord segments
*need to know what they all look like
- cervical: lrg amts of white matter; anterior grey horn is lrg; elongated oval shape
- thoracic: v small amt of grey matter; less elongated; lateral horn of grey matter specific to this segment
- lumbar: large anterior/posterior grey horns; considerably less white matter compared to cervical
- sacral: small in diameter, but relatively lrg amts of gray matter
dorsal and ventral roots
specific to PNS
- dorsal roots bring sensory info in towards the spinal cord
- ventral: sends commands out of spinal cord
tracts
parallel bundles of axons within CNS traveling up or down
- grpings. of white matter columns are named according to where a tract begins (soma) and where it ends (axon terminals)
- spinal cord white matter is both sensory and motor
- ASCENDING tracts: sensory info
- DESCENDING TRACTS: motor info
mixed nerves
contain afferent & efferent axons
motor nerves
contain only efferent axons
sensory nerves
contain only afferent axons
somatic sensory
- part of sensory/afferent division of PNS
- general: touch, pain, pressure, vibration, temp, and proprioception in skin, body wall, and limbs
- special: hearing, equilibrium, vision
visceral sensory
- part of sensory/afferent division of PNS
- general: stretch, pain, temp, chem changes, irritation in viscera; nausea, hunger
- special: taste, smell
cranial nerves
- 12 pairs of nerves
- attached to brain & pass thru skull foramina
- numbered with roman numerals de rostral to caudal
- each nerve is either: motor, sensory, or mixed
olfactory nerve (i)
- it projects thru the cribriform foramina of the ethmoid bone
- function: special visceral sensory, sense of smell
- origin: olfactory receptor cells (bipolar neuron) in the olfactory epithelium of the nasal cavity
optic nerve (ii)
- special somatic sensory nerve, vision
- crosses over @ optic chiasma
- passes thru optic canal of sphenoid bone
- origin: retina of eyes
oculomotor nerve (iii)
- motor nerve: both somatic and visceral
somatic:
- innervates the 4 extrinsic eye muscles to move the eye:
1. superior rectus
2. medial rectus
3. inferior rectus
4. inferior oblique
- innervates levator palpebrae superiors muscle that elevates the upper eyelid
visceral:
- constricts muscles or the iris to constrict pupil
- ciliary muscle controls lens shape
trochlear nerve (iv)
- motor-only type of cranial nerve
- innervates 1 muscle of the eye: superior oblique muscle
trigeminal nerve (v)
- mixed nerve
- somatic motor function: mastication (chewing)
- somatic sensory: touch, temp, and pain on the face
- has 3 divisions: ophthalmic (v1), maxillary (v2), and mandibular (v3)
abducens nerve (vi)
- 3rd nerve that innervates eye muscle: lateral rectus
- somatic motor function: abducts the eye
facial nerve (vii)
- mixed nerve
- somatic motor nerve function: controls facial muscles for facial expression; parasympathetic innervation to glands
- somatic sensory: special sensory taste from anterior 2/3 of tongue
vestibulocochlear nerve (viii)
- 2 nerves in 1: vestibular and cochlear nerve
- sensory function
*vestibular: special somatic sensory, equilibrium- cochlear: special somatic sensory, hearing
glossopharyngeal nerve (ix)
- mixed nerve
- somatic motor function: swallowing; innervate muscles of the tongue, the pharynx, and the parotid salivary gland
- sensory: taste posterior 1/3 of tongue, middle ear cavity
vagus nerve (x)
- mixed nerve
- somatic motor function: swallowing and vocalization
- parasympathetic innervation to the thoracic and abdominal viscera; alter heart rate, dictate constriction and relaxation of airways
accessory nerve (xi)
- motor only nerve
- innervates skeletal muscles: trapezius and sternocleidomastoid muscles that move head and neck
hypoglossal nerve (xii)
- motor only
- somatic motor function: innervate the intrinsic and extrinsic muscles of the tongue; aid tongue mvmnt during feeding, swallowing, and speech
spinal nerves
- C1-C8
- T1-T12
- L1-L5
- S1-S2
- Coccygeal nerve Co1
grouped into:
- cervical plexus
- brachial plexus
- cervical enlargement
- intercostal nerves
- lumbar enlargement
- lumbar plexus
- sacral plexus
- cauda equina
- spinal nerves exit out above the vertebra for all the c1-c8 nerves, but starting from the thoracic region, the corresponding nerves exit below the vertebra
spinal cord structure
- each spinal nerve is attached to the spinal cord by a ventral root and a dorsal root
- each root forms from a series of rootlets, which span the length of the spinal cord
- only the dorsal root will have a ganglion (called the dorsal root ganglion)
- spinal nerve: formed the roots coming together; spinal nerve is mixed (motor and sensory)
- spinal nerve splits; the split is called the ramus (the rami are mixed - motor and sensory)
dorsal root ganglion
a cluster of cell bodies
- the cell bodies = unipolar neurons
ventral roots
carry only motor axons
- motor info makes it way thu ventral side of spinal cord and out thru ventral root -> spinal nerve -> ventral or dorsal ramus
dorsal roots
carry only sensory axons
ex: sensory info from arm -> ventral ramus -> spinal nerve -> dorsal root ganglion -> dorsal root -> gray matter
nerve plexuses
- the ventral rami of all spinal nerves (except T1-T12) branch and join 1 another forming an interlacing network of axons
- primarily serve the limbs
- bc of this arrangement, if a single spinal nerve is damaged, it does not completely paralyze any limb muscle
T2-T12 (back & thoracic) innervation
- all dorsal rami supply the back of the trunk in a segmented fashion
- the ventral rami of the thorax (T2-T12) supplies the remainder of the thorax in a segmented fashion via the intercostal nerves
cervical plexus (C1-C5)
- located deep in the neck, under the sternocleidomastoid muscle
- phrenic nerve = primary nerve; innervates diaphragm
brachial plexus (C4-T1)
- axillary nerve: posterior shoulder region
- radial nerve: posterior of upper limbs
- musculocutaneous nerve: upper portions of arm
- ulnar nerve: forearm, pinky finger and half of the ring finger
- median nerve: along radius/thumb side; remainder of digits
tip: ur mam
lumbar plexus (L1-L4)
- femoral nerve: innervates vast majority of the thighs
- obturator nerve: innervates the medial side. of the thighs
sacral plexus (L4-S4)
- sciatic nerve: back of thighs and legs
dermatomes
- an area of the skin tht provides sensory input to the CNS via 1 pair of spinal nerves; a map that denotes which pair of nerve is responsible for sensory info along that part of the skin
- compare the arrangement on the trunk to that on the limbs
- they run down the limbs
- trunk: they are more segmented and are more circular and horizontal
somatic motor vs autonomic motor
somatic NS:
multipolar neuron from CNS -> heavily myelinated axon from PNS -> Ach released @ neuromuscular junction -> stimulate effector = skeletal muscle to contract
autonomic NS:
sympathetic option 1: multipolar neurons from CNS -> lightly myelinated, preganglionic axon from PNS -> Ach released @ ganglion (meeting. pt b/w 2 neurons in the ANS) -> postganglionic axon (some of these will be unmyelinated) -> NE (norepinephrine) released -> incr/decr effect of effector = smooth muscle, glands, cardiac muscle
sympathetic option 2: multipolar neurons from CNS -> lightly myelinated, preganglionic axon from PNS -> ganglion release Ach @ synapse with adrenal gland -> NE released from adrenal medulla -> incr/decr effect of effector = smooth muscle, glands, cardiac muscle
***preganglionic axons will always be short!!!! post ones are long!!!
parasympathetic: multipolar neurons from CNS -> lightly myelinated, preganglionic axon from PNS -> releases Ach @ ganglion -> unmyelinated post ganglionic axon releases Ach -> > incr/decr effect of effector = smooth muscle, glands, cardiac muscle
***preganglionic axons will always be long!! post ones are short!!
autonomic nervous system neurons
- preganglionic neuron: soma located in the CNS
- sympathetic: lateral horn of thoracolumbar spinal cord
- parasympathetic: brainstem or sacral spinal cord
- postganglionic neuron: soma located in PNS
parasympathetic ganglia (terminal ganglia)
- aka craniosacral division of ANS
- terminal ganglia: located close to or within the wall of an organ
- bc terminal ganglia are located close to the effector organ:
- long preganglionic axons (CNS-> ganglia)
- short postganglionic axons (ganglia -> effector)
- cranial outflow: 4 cranial nerves
- sacral outflow: sacral spinal nerves
cranial nerves associated with parasympathetic function
CN III Oculomotor - pupillary constriction
CN VII Facial - lacrimal gland (tear production); sublingual and submandibular salivary glands
CN IX Glossopharyngeal - Parotid gland
CN X Vagus - visceral organs of the thorax (ex: heart) and upper 2/3rds of the abdomen; 90% of preganglionic parasympathetic fibers
tip to remember:
3 + 7 = 10 (cn 3, 7, and 10) and u just need to memorize 9 is also included
Paris Occultists Face Glossy Vaginas (Parasymapthetic, Oculomotor, Facial, Glossopharyngeal, Vagus)
sympathetic ganglia
- paravertebral ganglia: located in a vertical row to either side of the vertebral column
- prevertebral ganglia: located anterior to the vertebral column, on the abdominal aorta
- bc most sympathetic ganglia are near spinal cord:
*short preganglionic axons (spinal cord -> ganglion)
*long postganglionic axons (ganglion -> effector)
adrenal glands
- paired adrenal (suprarenal) glands on the superior poles of the kidneys
- each is 2 glands w/ diff functions (2 layers)
- adrenal cortex
*adrenal medulla
- adrenal cortex
adrenal cortex
- outer layer of adrenal gland
- secretes steroid hormones
adrenal medulla
inner core
- stimulated by preganglionic sympathetic neurons that terminate on these cells
- secretes a mix of hormones into bloodstream: 85% epinephrine (adrenaline) & 15% norepinephrine (noradrenaline)
autonomic tone
describes the normal backgrnd rate of activity that represents the balance of the 2 systems (symp/para) according to the bod’s changing needs
- the 2 systems often oppose e/o
exceptions = skin, liver, adrenal gland, which are key effectors that is innervated by only the sympathetic NS
ex: autonomic control of the heart
- heart has pacemaker cells tht can self generate electrical signals that dictate heart rate
- vagi can innervate the pacemaker cells & decr heart rate (parasymp. effect)
- sympathetic chain (nerves of symp. NS): some of these nerves can go to pacemaker cells & incr heart rate; can also go to muscular wall of heart & control the force that the heart beats with
ex: autonomic control of the bronchioles
- smooth muscle found in wall of bronchioles - dictate dilation/constriction
- sympathetic: causes bronchodilation; muscle relaxes to open airways -> can supply more o2 to muscles for movement
- parasympathetic: causes constriction; muscle contracts to close airways
adrenergic vs cholinergic receptors
adrenergic = autonomic receptors. tht bind to adrenaline & noradrenaline; serve sympathetic NS
cholinergic: autonomic receptors tht bind to Ach
