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