Lecture 12 Flashcards
what is the function of basal ganglia
they initiate movement and habit learning
what is the function of the cerebellum
coordinates and corrects ongoing movement, motor learning
what is the function of the upper motor system
cell boides in brainstem or verebral cortex, initates and plans voluntary movement
what does the lower motor system consist of
cells in the spinal cord that directly contact the muscles and spical cord cell that regulate them
name the final common path for initiating movement
lower motor system
skeletal muscles are made up of inidividual muscle cells called
muscle fibers
fibers are innervated by ..
lower motor neurons
where are the cell bodies of flower motor neurons found
in the brainstem or spinal cord
motor neuron cell bodies exist in ___ of neurons that innervate similar targets
pools
the motor neuron ool are arranged in the spinal cord in a way that reflects the body arrange ____ to _____
rostrally to caudally
first cervical segments :
neck flexors
sacral and lambar segments
feet and legs
within a segment , how are pools arranged?
pools are aragned so that proximal muscla are represented medially
how many types of motor neurons are there
2
list the types of motor neurons
alpha motor neurons , gamma motor neurons
what is the function of an alpha motor neuron
innervate the extrafusal skeletal muscle fibers that generate the force of contraction
is the function of a gamma motor neuron
innervate the muscle spindles
how many motor neurons innervate a muscle fiber
1
how many fibers do motor neurons innervate
several
what is a motor unit
a single alpha motor neuron and all the fibers it innervates
t/f alpha motor neurons vary in the number of fibers they innervate
true
do small alpha motor neurons innervate a lot or a little amount of muscle fibers
a few
do small alpha motor fibers generate large or small forces
small
do small alpha motor neurons fatigue easily
no , they are resistant to fatigue
small alpha motor units are also known as
slow motor units
does a small or intermediate motor unit innervate more muscle fibers
intermediate
what size force does an intermediate motor unit create
medium
fast fatiuge resistant motor units are also known as
intermediate sized
large alpha motor neurons are also known as
fast fatigable motor units
the small the force a motor unit makes, the ____ its ____
slower, fatigue
the neurons that are apart of the small units have the highest/lowest threshold for activation
lowest
__ units are used in sudden forceful movements like jumping
ff
explain the size prinicple
during a movement, alpha motor neurons are recruited in size order , from smallest to largest
what is the primary role o fthe lowermotor neuron
to pass instructions from the upper motor neurons to the muscles
are lower motor neurons capable of independently causeing behavior
yes
what is responsible for spinal reflexes
lower motor neurons
what makes up the central pattern generator for walking
the lower motor neurons
define a reflex
simple involuntary reactions in response to a stiumuls
how are spinal reflexes mediated
by the lower motor neurons of the spinal cord
what are the 2 spinal reflexes
stretch reflex and flexion reflex
define stretch reflex
as a muscle is stretched , it is activated to counteract the stretch
define flexion reflex
allows you to withdraw your foot from a noxius stiumuls and still remain standing
when a muscle is stretched it will reflexively contract. what is the name of this concept?
the stretch reflex
what is the main purpose of the stretch reflex
in ensures that your muscles stay at a certain length
what is a homonymouse muscle
the main muscle that is being contracted
what does a stimulated alpha motor neuron cause
the stretched muscle to contract
when stretch activates muscle spindles what do sensory neurons do
they send action potentials at higher frequency to the spinal cord
what do sensory neurons synapse with
directly with the alpha motor neurons that exire fibers of the stretched muscle
do alpha motor neurons innervating an anatagonist fire more or less
less
is a monosynaptic connection fast or slow
fast
the stretch refles is also called___
the deep tendon or myotatic reflex
list 5 places on your body where you can test the stretch reflex
knee, ankle, jaw m biceps m triceps
describe the flexor reflex
a painful stimulus cause you to flex the affected limb
what is the crossed extensor reflex
it allows to to balance after youve withdrawn a hurt limb
during the flexor reflex what is excited and what is inhibited
ipsilateral flexors are excited and extensors are inhibited
during the crossed extension reflex what is inhibited and whate is excited
contralateral flexors are inhibited and and extensor muscles are excited
in both the flexor reflex and the crossed extension reflex what kind of connection to the muscles is there
a polysynaptic connection
if you touch something painful do you feel the pain or move your limbs why
move your limbs , it takes longer for your brain to process the pain
is brain input needed to carry out reflexes
no
is brain input in reflexes excitatory or inhibitory
inhibitory
descending input from the brain can ___the amount of movement
modulate
during walking the -__ and ___ alternate in activity
extensors and flexors
walking motion in cates is due to what
central pattern generators in the spinal cord that coordinate the extension and flexion of each limb
what kind of netwoeks are central pattern generators
nerual netwoeks
what do central pattern generators produce
rhythmic mpatterned outputs without sensory feedback
humans with spinal cord injury can not rely on their
___ ______ __ to walk
central pattern generators
motor contorl centers in the brainstem maintain what 3 things
balance
posture
eye gaze
t/f in the anticipation of movmemnt muscles contract
true
what 2 areas of the brain send axons to the lower motor neurons in the spinal cord
the primary motor cortex and the premotor cortex
what are the main responsibilities of the primary motor cortex and the premotor cortex
the are responsible for initiation of voluntary movmemnt and plannaing and coordinating complex movements
the __ ____ ___ has the most direct connection s to the lower motor neurons
primary motor cortex
what do axons leaving the primary motor cortex and the premotor cortex form ?
axons leaving the primary motor cortex and the premotor cortex form the corticobulbar and corticospinal tracts
where does the corticobulbar tract terminate
at the brainstem
motor information from the corticobulbar tract goes to the ….
face
where does the corticospinal tract terminate
at the spinal cord
motor information from the corticospinal tract goes to ..
the body muscles
at the base of the pons, the corticospinal tracts forms the …
medullary pyramids
what occurs at the medullary pyramids
90% of the axons cross
the crossing of axons at the medullary pyramids is known as
decussation of the pyramids
some of the corticospinal tract axons synapse directly with what
alpha motor neurons in the forearm and hand
where are the 2 targets of corticospinal tracts
synapse directly with alpha motor neurons / terminate among pools of local circuit neurons in the spinal cord
where does the primary motor cortex get input from
the sensory and other areas of the brain
where does the primary motor cortex output information to
to the lower motor neurons in layer 5
what is the name of the largest cells in layer 5 of the primary motor cortex
Betz cells
describe the axons of Betz cells
theyy descend and enter the spinal cord
are there only betz cells in the spinal cord
no
do Betz cells handle connections to distal or proximal extremities
distal
firing of ____ ____ cells precedes and is associated with ___ ____
primary motor cortex, muscle contraction
t/f stimulation of primary motor cortex can cause movements
true
microstiumulation of small sites in the ___ ___ ___ can cause large and hand movement
primary motor cortex
what 2 parts of the body are over represented in the primary motor cortex
the hands and tongue
the primary motor cortex has similar a map to
the somatosensory cortex
the premotor cortex recieves input form the other cortical areas of the brain areas relating to ___ ___ and ___
spatial signals and intention
the premotor cortex connects exclusivley with the
the primary motor cortex
neurons in the ___ ___ __ fire in anticipation of a movement
premotor cortex
describe a mirror neuron
with a movment is performed and when the monkey sees someone else performing that movment
where is the brocas area located
in the permotor cortex in humans
what isthe brocas area
it is responsible for movements important for speech
