Test 3 Review Powerpoint Flashcards
Isotonic contraction
agonist contracts, antagonist releases basis of movement
pulling up, like with a weight weight
isometric contraction
agonist/antagonist contract across joint, stabilizing joint
no movement
structure of skeletal muscle
axons from CNS innervate muscle fibers
actin in sarcomeres
alpha motor neuron
innervates extrafusal muscle fibers
contraction
motor unit
alpha motor neuron and all muscle fibers it innervates
innervation ration
number of muscle fibers innervated by a motor unit
higher is less fine control
lower is more fine control (1:1)
Lower motor neurons (LMN)
-Ventral horn
-Motor neurons that innervate SKELETAL muscle
directly command muscle contraction
-Ventral horn size differs along length of spine, # of motor neurons differ by how many muscles innervated (arms vs stomach)
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CNS Control of Contraction
Increasing firing rate of alpha
motor neurons
Recruiting more alpha motor neurons from motor neuron pool
Fast motor units
rapidly fatiguing white fibers
low mitochondrial content
slow motor units
slowly fatiguing
red muscle
high mitochondrial content
Excitation of Muscle
-Alpha motor neuron fires AP
-Ach released from alpha motor neuron at NMJ
-Nicotinic channels open
-Na+ rushes through sarcolemma, causing type of EPSP called EPP (end plate potential)
-one EPP depolarizes sarcolemma enough to cause AP
-AP sweeps down sarcolemma through T tubules
-Voltage gated Ca2+ channels in T tubules open
-Ca 2+ spills out of sarcoplasmic reticulum
Releases calcium all over, amplified, bigger response
Contraction of muscle
- Ca2+ binds troponin
- Myosin-binding sites on actin exposed
- Myosin head binds to actin
- Myosin heads rotate
- Myosin heads use ATP to disengage
- Cycle continues as long as Ca2+ and ATP are present
Sarcomere
basic contracting unit of muscle
Relaxation of muscle
-As EPP (end plate potential)s end, sarcolemma and T tubules return to resting membrane potential
-Ca2+ returns to sarcoplasmic reticulum via ATP-driven pumps
-Myosin-binding sites on actin are covered by troponin
Fast process because we can contract fast
Reflexive movement
- controlled by spinal cord and brainstem circuitry
- cannot improve with practice
- initiated by sensory stimulation
Voluntary movement
- controlled by cerebral corex
- can be improved with practice
- initiated by thoughts
Gamma motor neuron
- innervate intrafusal muscle fibers
- adjust tension in muscle spindle
- extrafusal muscle fibers to shorten
- if spinals are slack, can’t report length of muscle so GMN contracts poles of spindle to align and gage stretch
- contraction of two poles pulls on equatorial region, keeping 1a axons active
Myotatic reflex
- stretch reflex
- muscle spindle stretched –> mechanosensitive ion channels, depolarize, 1a afferent activated –> increased AP –> alpha motor neuron activated –> muscle contracts
- monosynaptic arch: one synapse separates primary input from motor output
- muscle length info
golgi tendon organ
- sensor in skeletal muscle, monitors muscle tension/force of contraction
- 1b axons
- muscle tension info
reverse myotatic reflex
- muscle tension increases
- 1b axons synapse on interneurons in ventral horn
- interneurons are inhibitory, protects muscle from being overloaded
- for example, if muscle tension increaes and almost snaps, inhibits motor neurons so that muscle neurons stop contracting
1a
muscle length info
1b
muscle tension info
corticospinal tract
- LATERAL PATHWAY (voluntary movement)
- voluntary movement in humans
- if cut, lose muscle control, rubrospinal can take over and help rebuild general control but lose fine muscle
rubrospinal tract
LATERAL PATHWAY (voluntary movement) important in non primates
tectospinal tract
VENTROMEDIAL (involun movement of proximal and axial muscles)
-orienting response, esp with eyes
vestibulospinal tract
VENTROMEDIAL (invol move of proximal and axial muscles)
-stability of head and back area to keep head
Pontine reticulospinal tract
VENTROMEDIAL (invol movement of prox and axial muscles)
enhances antigravity reflexes
balance
Medullary reticulospinal
VENTROMEDIAL (invol movement of prox and axial muscles)
liberates antigravity muscles
balance
motor area 6: what projects heavily into it?
basal ganglia and cerebellum
motor area 6: where does it project heavily?
area 4
roland’s tapping experiment
motor areas of brain
- M1=simple movement
- SMA + M1 complex movement
- SMA thinking about complex movement
premotor area
planning movement
function of motor cortex
M1 neurons code for force and direction of movement
Force
frequency of action potentials
direction
population coding of action potentials
Basal ganglia
willed movement
parts of basal ganglia
caudate nucleus putamen globus pallidus subthalamic nucleus substantia nigra
caudate nucleus
motor processes learning processes (associative, etc) executive functioning
globus pallidus
movement
pacemaker
putamen
regulate movements
learning
subthalamic nucleus
action selection
substantia nigra
rewards, eye movement, motor planning, addiction
