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Lecture 7

Lecture 7 - Motor Control

7 Pages
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Department
Psychology
Course Code
PSY290H1
Professor
Franca Placenza

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Movement
1.All movement involves contraction of muscles
oContractions of muscles are orchestrated by neural circuits in the spinal cord
and brain
2.Neural circuits
oLower motor neuron circuits >>> control simple reflexive movements by
spinal cord
oUpper motor neurons circuits >> found in various parts of the brain that
control
voluntary movement and execution
oEX = reaching for a glass
3.Cardiac muscle and smooth muscle (found in organs) are other types
Anatomy of Muscles
4.Skeletal muscles = voluntary movement
oMade up of hundreds of muscles fibers (essentially the cells of the muscle)
Are multi-nucleid (more than one nucleus)
oMain type of muscle
5.Each muscle enclosed in connective tissue
oForms tendons at ends that connects to bones
6.2 main types of muscle fibers:
oExtrafusal fibers = make up the bulk of the muscle
oIntrafusal fibers = found within a specialized receptor called muscle spindle
7.Structure of Skeletal Muscle Fibers
8.Muscle fibers made up of organelles
9.Bundles of myofibril (protein molecules joined together)
oMyofibril are divided into segments (sarcomere)
Thin filaments > made up of actin
Thick filaments > made up of myosin
Muscle Contraction
10.Muscle contractions occur in response to firing of motoneuron
11.Firing of motor neuron releases acetylcholine (AcH) at neuromuscular junction
oNeuromuscular junction where motor neuron synapse directly on the muscle
fiber
Highly specialized
1:1 relationship between firing and creation of action potential in the
muscle fiber
oBinds at nicotinic receptor on muscle fiber
Depolarizes it and causes action potential
12.Action potential propagates (spreads) along muscle fibers
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oCauses the opening of voltage-gated Ca2+ channels from sarcoplasmic
reticulum
(stores Ca2+)
oCa2+ floating around in the intracellular fluid
oThen Ca2+
13.In thin filaments, actin has binding sites for myosin (what thick filaments are made
of)
oTropomyosin intertwined within the thin filament and blocks the myosin
binding
sites (in relaxed state)
oTroponin holds ribbon of tropomyosin in place
Has Ca2+ binding sites along it as well
Both are proteins found on thin filaments
14.Myosin heads contain ATP
15.Myosin binds to actin causing myosin heads to pivot, pulling thin filaments toward
center of thick filament and sarcomere shortens
oSarcomere shortening = muscle contraction
16.As long as you have ATP and Ca2+, a muscle can contract
17.Once action potential is stopped, Ca2+ is taken back up into the reticulum for reuse
Lower Motor Neurons
18.Directly controls and connects to muscles
19.Mostly found in the spinal cord
20.Have cell bodies in the ventral horns of spinal cord
21.Alpha motor neurons = innervating extrafusal
oLower motor neuron
22.Most muscle fibers are innervated by a single alpha motor neuron BUT a single
alpha motor neuron innervates many muscle fibers
23.Motor unit = smallest component of motor control
oOne alpha motor neuron and all the muscle fibers it innervates
24.Motor neuron pool = collection of alpha motor neurons that innervate a single
muscle
oEX = the neurons that innervate the bicep muscle
Motor Reflexes
25.Reflex = stereotyped, involuntary motor response elicited by a defined stimulus
oAre fast
oInvolve few synaptic connections
oInvolve sensory input and motor output
oEX = breathing, muscle tone while you are sitting up in a chair
26.Monosynaptic reflex - a single synaptic connection
www.notesolution.com

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Description
Movement 1. All movement involves contraction of muscles o Contractions of muscles are orchestrated by neural circuits in the spinal cord and brain 2. Neural circuits o Lower motor neuron circuits >>> control simple reflexive movements by spinal cord o Upper motor neurons circuits >> found in various parts of the brain that control voluntary movement and execution o EX = reaching for a glass 3. Cardiac muscle and smooth muscle (found in organs) are other types Anatomy of Muscles 4. Skeletal muscles = voluntary movement o Made up of hundreds of muscles fibers (essentially the cells of the muscle) Are multi-nucleid (more than one nucleus) o Main type of muscle 5. Each muscle enclosed in connective tissue o Forms tendons at ends that connects to bones 6. 2 main types of muscle fibers: o Extrafusal fibers = make up the bulk of the muscle o Intrafusal fibers = found within a specialized receptor called muscle spindle 7. Structure of Skeletal Muscle Fibers 8. Muscle fibers made up of organelles 9. Bundles of myofibril (protein molecules joined together) o Myofibril are divided into segments (sarcomere) Thin filaments > made up of actin Thick filaments > made up of myosin Muscle Contraction 10.Muscle contractions occur in response to firing of motoneuron 11.Firing of motor neuron releases acetylcholine (AcH) at neuromuscular junction o Neuromuscular junction where motor neuron synapse directly on the muscle fiber Highly specialized 1:1 relationship between firing and creation of action potential in the muscle fiber o Binds at nicotinic receptor on muscle fiber Depolarizes it and causes action potential 12.Action potential propagates (spreads) along muscle fibers www.notesolution.com
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