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psy290 lecs 6 (chp7).pdf

28 Pages
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Department
Psychology
Course Code
PSY290H1
Professor
Junchul Kim

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Sensorimotor System 12-05-22 1:25 PM
Movement: Sensorimotor System
3 steps: voluntary movements
brain:
o sends motor commands to motor neurons in spinal cord
motor neurons in spinal cord:
o release acetylcholine (ACh) at neuromuscular junction
Ach:
o binds to nicotinic ACh receptors on muscle fiber
! trigger contraction of muscle
Muscles moving body parts
flexor muscles:
o bend/flex a join (biceps + tendons)
extensor muscles:
o straighten/extend joint (triceps + tendons)
synergistic muscles:
o any 2 muscles whose contractions produce same movement
(biceps + tendons)
antagonistic muscles:
o any 2 muscles that act in opposition (biceps & triceps)
Muscle Contraction
Is triggered by spinal motor neurons
3
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Neuromuscular junction:
site of ACh release
o cell bodies of motor neurons are found in ventral horns of
spinal cords
spinal motor neurons:
o sends AP to muscle through ventral horn
AP arrives at axon terminals
o release ACh at neuromuscular junction
lower motor neurons (in ventral horn)
o ventral root
! mixed spinal nerve
" neuromuscular junction (at muscle fiber)
ACh binds to nicotinic receptors on muscle fiber
o postsynaptic potentials arise & trigger AP in muscle fibers
Spinal Motor Neurons
most muscle fibers:
o innervated by a single alpha motor neuron
single motor alpha motor neuron:
o innervates many muscle fibers
a motor unit (smallest component of motor control)
o is a single alpha motor neuron & its associated muscle fibers
motor neuron pool:
o collection of alpha motor neurons that innervates a single
muscle
!
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Anatomy of Muscles: Skeletal muscle
each muscle:
o connected to bones
o through tendons
o is made up of hundreds of muscle fibers
each muscle fiber:
o is a single, large cell with multiple nuclei
o contains bundles of myofibrils
Structure of skeletal muscle fibers
each myofibril is divided into segments:
o composed of myofilaments
! thin called actin
! thick called myosin
myofilament:
o a functional unit of muscle
2 types of muscle fibers:
o extrafusal fibers:
! bulk of muscle
o intrafusal fibers:
! within specialized receptors (muscle spindle)
7
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Muscle fibers shown at progressively
greater magnification

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Description
Sensorimotor System 120522 125 PM Movement Sensorimotor System 3 steps voluntary movementsbraino sends motor commands to motor neurons in spinal cordmotor neurons in spinal cord orelease acetylcholine ACh at neuromuscular junction 012 Ach 1o binds to nicotinic ACh receptors on muscle fiber1334405673 trigger contraction of muscle782590001234123204506102544136744123471002889631947414711809062469650416319447141433500281800600000242660010203014050146303Neuromuscular junction site of ACh release 4 Muscles moving body partsflexor muscles3 o bendflex a join bicepstendonsextensor muscleso straightenextend joint tricepstendonssynergistic muscleso any 2 muscles whose contractions produce same movement bicepstendonsantagonistic muscleso any 2 muscles that act in opposition bicepstriceps Muscle ContractionIs triggered by spinal motor neurons o cell bodies of motor neurons are found in ventral horns of spinal cordsspinal motor neurons o sends AP to muscle through ventral hornAP arrives at axon terminals o release ACh at neuromuscular junctionlower motor neurons in ventral horn o ventral rootmixed spinal nerve neuromuscular junction at muscle fiber ACh binds to nicotinic receptors on muscle fiber o postsynaptic potentials arisetrigger AP in muscle fibers Spinal Motor Neuronsmost muscle fibers o innervated by a single alpha motor neuronsingle motor alpha motor neuron o innervates many muscle fibersa motor unit smallest component of motor control o is a single alpha motor neuronits associated muscle fibersmotor neuron poolo collection of alpha motor neurons that innervates a single muscle 61787101234563450247011213487452501116
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