CNS part 3 Flashcards
what does the somatic motor system of the CNS control
skeletal muscles
what does the ANS control
involuntary functions
where is the ANS distriubted
throughout the visceral organs, CV system, and exocrine glands
what does the reflex arc consist of
receptor, sensory neuron, efferent neuron, and effector
upper motor neurons?
efferent pathways that relay info from the cerebrum to brainstem or spinal cord
what do upper motor neurons synapse with
interneurons
what do UMN control the activity of
LMN
if UMN are destroyed, what occurs
partial recovery
if LMN are destroyed, what occurs
permenant paralysis
where do LMN cell bodies originate? where do their axons go?
cell bodies gray matter of spinal cord, but their axons extend to the PNS
what do LMN have a direct influence on
muscles
what do we need for voluntary muscle activity
UMN stimulation
what is the final common pathway for all voluntary mvmt
alpha LMN
what are the 2 types of LMN
alpha motor neurons and gamma motor neurons
what do alpha motor neurons innervate
extrafusal muscle fibers
what do gamma motor neurons innervate
intrafusal muscle fibers
what are alpha motor neurons involved in
muscle contraction
what are gamma motor neurons involved in
sensing position
what do interneurons connect
UMN and LMN
where do alpha motor neurons originate
ventral gray matter of spinal cord and brainstem nucleu
what are the 3 inputs to alpha motor neurons what determine which fibers will contract
upper motor neurons, spinal interneurons, and sensory neurons
are UMN inhibitory or excitatory
inhibitory
what mvmts are UMN involved in?
voluntary
are spinal interneurons inhibitory or excitatory
they can be either
what are central pattern generators
basic motor programs encoded in spinal circuits such as walking
what do sensory neurons from muscle proprioceptors do
provide feedback about muscle length and tension
what can damage to LMN cause
atrophy, fasciculation, hypotonia, hyporeflexia
what is atrophy?
dec in bulk
what is hypotonia?
dec in tone of skeletal muscles
what is hyporeflexia?
dec muscle stretch
what are fasciculations/fibrillations?
involuntary twitches of LMN when denervated motor units discharge spontaneously
what can damage to LMN result in
loss of all voluntary and reflex mvmt
ex of pure lower motor neuron lesion?
poliomyelitis
what does poliovirus infect
motor neuron cell bodies in the ventral horn of spinal cord
what does polio lead to
paralysis
amyotrophic lateral sclerosis affects what neurons
both upper and lower motor neurons
where does ALS begin
cervical spine
what do pt with ALS present with
flaccid paresis in upper extremities and spastic paresis in lower extremities
what is lambert eaton myasthenic syndrome
antibodies bind to Ca channels and inhibit Ca entry into the nerve terminal
what do aminoglycoside antibiotics do
impair Ca channel function
what do clostridium botulinum toxins do
cleave presynaptic proteins and prevent NT release at neuromuscular and parasympathetic cholinergic synapses
what occurs at the cellular level in myasthenia gravis
autoantibodies bind to the nicotinic AChR and block neurotransmission by inhibiting receptor function and activating complement mediated lysis of postsynaptic membrane
what do somatosensory receptors affect
senses of the body
what are mechanoreceptors responsible for
position, vibration, vouch
what are nococeptors responsible for
pain
what do somatosensory pathways do
provide tactile info, guide mvmt, protect
what is a stimulus?
distinct type of nrg such as light, sound, heat, mechanical, and chemical
receptors are transducers that convert the stimulus energy into what in neurons
electrical signals
what detects sensation of cold and warm
thermoreceptors
most numerous type of thermoreceptor
cold fibers
temps lower that what are considered painful
16C or 60F
when do warm fibers have their peak response
43C or 109 F
why does a sudden change in temp transmit initial shock
thermoreceptors are rapidly adapting
what receptors resond to extreme heat, cold, and pain
nociceptors
which receptors have a high threshold of activation and are silent unless a noxious stimulus is applied
nociceptors
what does superficial pain arise from
body surface
what does deep pain arise from
muscles and joints
initial pain?
sharp highly localized pain that comes on fast bc of myelinated nerve fibers with rapid conduction velocities
delayed pain?
burning sensation that lasts longer than initial pain. onset is delayed bc unmyelinated neurons have slow conduction velocity
where are photoreceptors located
rods and cones in retina
what are chemoreceptors stimulated by
change in chemical composition of environment
taste, smell, and visceral receptors are what kind of receptor
chemoreceptor
what do visceral receptors detect
changes in plasma level of O2, pH, and osmolality
where are proprioceptors located
tendons, muscles, joints
what do proprioreceptors do
relay info about muscle length and tension
what receptors convey sensory info from the skeletal system
proprioreceptors
dermatome?
area of skin supplied with afferent nerve fibers by a single dorsal root
sciatica?
back pain that radiates down the leg
MCC of sciatica?
spinal disc herniation that impinges upon a spinal nerve and results in a dermatomal pattern of pain
where does L5 pain radiate?
back to butt, posterolateral thigh, anterolateral lower leg to the large toe
where does S1 pain radiate?
back to butt, posterolateral thigh, and calf to the lateral border of the foot
merkel discs?
sense fine discrimination; slowly adapting and sense pressure
meissners corpuscles?
sense fine discrimination; rapidly adapting and sense rapid changes in skin contacts
are ruffinis endings slow or rapidly adapting?
slow
what do ruffinis endings detect
local stretching of skin
are pacinian corpuscles slow or rapidly adapting
rapidly
what do pacinian corpuscles detect
vibration
what do hair follicles detect
displacement of hair
what is visceral pain
pain arising from internal organs that is dull, burning, and poorly localized
what afferents do visceral pain receptors follow
sympathetic
what afferents do visceral sensations (like satiety) receptors follow
parasympathetic
what do noxious stimuli cause
referred pain
where is referred pain perceived? why do we feel referred pain?
perceived on bodys surface; occurs from afferent fibers from the visceral converging on the spinal cord via the dorsal roots
where is the ANS located
CNS and PNS
what are the diff types of muscles/cells in the ANS
smooth muscle, cardiac muscle, and gland cells
what NS maintains a steady state among visceral/internal organs
ANS
divisions of the ANS
SNS, PSN, and enteric NS
are preganglionic neurons myelinated or unmyelinated?
myelinated
are postganglionic neurons myelinated or unmyelinated?
unmyelinated
3 functions of the ans
- maintenance of homeostasis- negative feedback
- integration of stress response- fight vs flight
- integration of visceral function- coordinate digestive organs
what 2 major organs is the ANS associated closely with
hypothalamus and pituitary
when is the SNS turned on
in resp to stress
what is the function of the PNS
conserve or restore nrg reserves
what NS is responsible for the fight or flight response
SNS
what does the SNS receive innervation from
cell bodies from the T1-L2 (thoracolumbar division)
what occurs in the body in the fight or flight response
sweat secretion, pupil dilation, BV constriction, inc. HR
what NS is the rest or repose response
PSN
what does the PNS receive innervation from
cell bodies in the cranial nuclei and sacral region of the spinal cord (craniosacral division)
tell me about preganglionic neurons in the PNS
they go right to the site; are long
tell me about preganglionic neurons in the SNS
they are short; postganglionic neurons are longer and go right to the target
what receptors interact with the sympathetic preganglionic fibers
acetycholine and cholinergic receptors
what receptors interact with the sympathetic postganglionic fibers
norepinephrine and adrenergic receptors
what receptors interact with the parasympathetic pre and post ganglionic fibers
acetycholine and cholinergic receptors
what is the primary NT released by postganglionic sympathetic neurons
norepinepherine
the cholinergic postganglionic receptors serve what glands
sweat
when norepinepherine binds to a target cells, what does the response depend on
specific adrenergic receptor type such as alpha 1, or 2 or beta 1, 2 ,or 3
what receptors do drugs target
adrenergic
what does a beta blocker block
beta adrenergic receptors
what happens to number of neurons as we age?
dec
what happens to brain size and weight as we age?
dec
what happens to adherence of dura mater to skull as we age?
inc
what happens to meninges as we age?
fibrosis and thickening
what happens to gyri and sulci as we age?
gyri narrow and sulci widen which inc size of subarachnoid space
cellular changes as we age to the NS
deposition of lipofuscin, senile plaques, neurofibrillary tangles, lewy bodies
what happens to neural signals to as we age?
they slow
