somatosensory 1 Flashcards
in the descending pathway cell bodies are located in the
primary motor cortex
axon fibers descend to the
corticospinal tract
most descending fibers decussate in the
medullary pyramids (90%)
fibers synapse on to the LMN in the
ventral horn of the spinal cord
in the descending pathway cell bodies in the ventral horn can be found in this laminae
9
LMN will always use __ as their Neurotransmitter
Ach
Ach binds to the ___ receptors
excitatory nicotinic
When ACh binds to the receptor, the channel opens, allowing for ion exchange and __
muscle fiber depolarization.
Excess ACh in the synapse is degraded locally by
Excess ACh in the synapse is degraded locally by acetylcholinesterase (AChE).
A motor unit is defined
A motor unit is defined as a motor neuron and all the fibers it contacts.
small motor units vs large motor units
Smaller motor units regulate fine motor activity, while large motor units control more gross movements.
gamma motor neurons and alpha
alpha: tells muscle to contract
gamma : intrafusal fibers that control the length/tension of muscle spindles
what happens When alpha motorneurons cause shortening of the extrafusal fibers?
sensory input is loss
polysynaptic vs monsynaptic
poly: indirect
mono: direct. These afferent proprioceptive sensory neurons directly synapse onto
ipsilateral lower motor neurons.
in reciprocal pathway :Afferent proprioceptive sensory neurons directly synapse onto
ipsilateral lower motor neurons to cause quadriceps contraction
and
interneurons that inhibit the lower motor neurons innervating the hamstring muscle.
interneurons are usually
inhibitory
reciprocal inhibition
activate one and relax other muscle ..
CROSSED EXTENSOR aka
(WITHDRAWAL) REFLEX’
explain withdrawl reflex
Afferent nociceptive sensory neurons cause contraction of the ipsilateral hamstring and reciprocal inhibition of the ipsilateral quadriceps, for flexion of the ipsilateral leg
Sensory neurons also cause extension of the contralateral leg
cerebellum
The cerebellum receives and integrates information about balance, body position, motor intention
The cerebellum is also involved in fine motor memories such as typing or playing the piano.
vestibulocerebellum
The vestibulocerebellum helps maintain balance and controls eye movements.
The spinocerebellum
The spinocerebellum enhances muscle tone and helps coordinate voluntary movements, especially fast, phasic motor activities
The cerebrocerebellum
The cerebrocerebellum plays a role in initiating voluntary movement
function of basal ganglia
Inhibiting muscle tone throughout the body – prevent unintentional movement
Monitoring and controlling slow, sustained contractions
Rubrospinal
- Integration of cortical and cerebellar information. Distal musculature preferentially.
Reticulospinal
Reticulospinal - excite motorneurons to proximal extensors for postural control
Tectospinal
Tectospinal - Head movement in response to stimuli
Vestibulospinal
Vestibulospinal – Postural control
Corticobulbar axons innervate the
Corticobulbar axons innervate the cranial nerve motor nuclei Ipsilateral system
in descending pathway Axons exit the spinal cord via the
Axons exit the spinal cord via the ventral
root and project in spinal nerves to innervate
target muscles.
parkisons is a Neurodegenerative disease of the
nigrostriatal dopamine pathway
BROWN-SEQUARD SYNDROME
spinal cord hemisection
ipsilateral defects
Loss of fine touch, vibration, proprioception
Loss of function-upper motor neurons
Spastic paralysis
Hyper-reflexia
BROWN-SEQUARD SYNDROME
spinal cord hemisection
contralateral defects
loss of pain and temp
NEUROMUSCULAR JUNCTIONMYASTHENIA GRAVIS
Autoimmune disorder.
Targets nicotinic receptors at the neuromuscular junction.
Muscle weakness, ptosis
Treated with acetylcholinesterase inhibitors
