Globular complex of 3 polypeptides, binds to: - actin - tropomyosin - calcium

Lecture IV Flashcards by Puck Bouter

3 types of movements:

Automatic movements (reflexes, for quick responses).
Voluntary movements (self-controlled, to achieve cognitive goals).
Fine control and adaptation of movements (learning, flexibility).

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Peripheral nervous system/PNS (2):

Nerves from spinal cord to muscles.
Divided into SNS and ANS:
- Somatic NS: voluntary
- Automatic NS: involuntary

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CNS for motor system (4):

Spinal cord, brainstem
Subcortical (basal ganglia)
Cortex: M1, PMC, PPC, SMA
Cerebellum

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Kinesthesia

Proprioception

Ability to sense motion(/position) of a joint/limb.

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Muscles are activated by the release of …

ACh

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4 important areas in cortex for motor system:

M1, PMC, PPC, SMA.

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5 structures of basal ganglia:

Caudate nucleus, globus pallidus, putamen, substantia nigra, subthalamic nucleus.

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Rapid, targeted movements have two phases:

Ballistic movement then error-correction movement.

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… innervates muscles via … release to contract muscles.

PNS via ACh.

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Sarcomere (2):

Z-disc to Z-disc.

Functional unit of skeletal muscle.

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… makes up the thick filaments.
Has … with … on it, for … and …
Interaction with thin filaments via …

Myosin makes up thick filaments.
Has heads with binding sites on it, for ATP and actin.
Interaction with thin filaments via actin.

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Thin filaments are made from actin. … polymerizes to form backbone - …

G-actin (globular) polymerizes to form backbone - F-actin.

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Each actin subunit has an active site where … can bind. When muscle fiber is …, these binding sites are blocked by spiraling strands of … around the backbone.

Actin has active sites where myosin can bind. When muscle fiber is relaxed, binding sites are blocked by strands of tropomyosin.

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Tropomyosin

Blocks myosin binding to actin when muscle is relaxed.

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Troponin

Globular complex of 3 polypeptides, binds to:

actin
tropomyosin
calcium

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Sarcoplasmic reticulum is a series of … that surround each …
Regulates levels of …, needed for …

Tubules that surround each myofibril.

Regulates levels of Ca2+, needed for muscle contraction.

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When the … stimulates muscle fibers, … on thick filaments bind to …
These attachments will form and break several times, as thick pulls thin into …
Thus pulling … towards the …
… shorten, … disappears
… from adjacent sarcomeres get closer together, so muscle cell will …, muscle contracts.

PNS stimulates
Myosin heads bind to actin subunits
Into sarcomere center.
Z-disc towards M-line
I-bands shorten, H-zone disappears
A-bands, muscle cell will shorten

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Neuromuscular junction/NMJ is the interface between … and …
Is a … between … and …

NS and skeletal muscle.

Chemical synapse between motor neuron and muscle fiber.

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NMJ contains … receptors, so when … is released into the synaptic cleft by the …, it binds to the junctional folds causing conformational change.
… binding opens ion channels - … influx, … efflux.
More … influx than … efflux - … of cell.
AP generation.
… will break down … - channels … - preventing further …
AP travels down … via … - opening .. channels.

ACh receptors, ACh is released by motor neuron.
ACh binding - Na+ influx, K+ efflux.
More Na+ influx than K+ efflux - depolarization.
Acetylcholinesterase breaks down ACh - closing channels.
AP travels down sarcolemma via T-tubules - opening Ca2+ channels.

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AP generated initiates excitation-contraction coupling.
AP causes .. levels in muscle fibers to …
Causing filaments to slide.

AP causes Ca2+ levels to rise.

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Muscle relaxed, … blocks myosin binding on actin subunits.
… binds to …
Change in shape which pushes … away.
Allows for …-… binding - muscle contraction.

Tropomyosin blocks myosin binding to actin.
Ca2+ binds to troponin.
Pushes tropomyosin away.
Allows myosin-actin binding - muscle contraction.

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… heads use … to change conformation and to pull … filaments to cause contraction.

Myosin uses ATP to pull actin filaments to cause contractions.

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2 types of motor neurons (regulating activity in muscles or glands):

Upper motor neuron (UMN) = originate in brain and brain stem, carry information in descending tracts.

Lower motor neuron (LMN) = influence activity of muscles/glands, activated by UMNs.

3 categories of LMNs:

Somatic - extend to skeletal muscle to control movement and tone.
Special visceral/branchial - supply muscles in head and neck.
General visceral - involved in ANS.

Somatic motor neurons - 3 types:

Alpha, beta, gamma.

Special about motor neurons (3)?

Large neurons with many synapses to each muscle fiber. Normally neurons synapse with other neurons not muscles. Arranged in antagonistic pairs: active pair causes contraction, non-active pair causes relaxation.

Reflex arc - controls reflexes (3):

Signals bypass the brain - acted upon in spinal cord. Build-in, innate behavior. Signals sent to brain later to evaluate further action, but first response in spinal cord.

Spinal neurons can generate ... without ...

Entire sequence of movements without feedback or input.

Spinal cord damage - antagonistic muscle pairs still show coordinated movement, even without input from brain. This means that coordination between two legs is ...

Purely controlled by spinal reflexes.

Sensory feedback of one leg is cut - ... Feedback from both legs is cut - ... Thus, limb with intact feedback is ..., but feedback ... to produce walking.

One leg cut - stop using that leg. Both legs cut - use both legs but walk less fine. Limb with intact feedback is preferred, but feedback is not necessary to produce walking.

Peripheral neuropathy causes errors during ... and ...

Sequences of automatic actions and guided movements.

CNS has different systems for different motor functions (5):

``` Cortico-spinal tract - voluntary Rubro-spinal tract - gait/walking Tecto-spinal tract - eyes Vestibulo-spinal tract - head Reticulo-spinal tract - reflexes ```

M1 - ... and ... | Consists of ..., which form direct connections to ... in ...

Simple movements and directions. | Betz cells, connections to alpha motor neurons in spinal cord.

Damage to M1 - ... ... to lesion site. Relatively common because close to ... Loss of cortical ... - reflexes become ... ... recovery.

Paralysis contralateral to lesion site. Close to middle cerebral artery. Loss of cortical inhibition/control, reflexes become stronger. Minimal recovery

PMC - sends signals to: - ... to achieve ... - ... to adapt movement to ... - ... to adapt movement to ...

M1 to achieve simple movements. Higher-order areas to adapt movement to context. Thalamus to adapt movement to remembered actions.

PMC activity reflects ... and ...

Global behavioral planning and goal depending on context.

Damage to PMC - no responses to ... and ...

No responses to cues. | Anosognosia = unaware of having inability.

M1 ... movements, PMC ... ... movements

M1 initiates movements. | PMC plans context-dependent movements.

Posterior parietal cortex/PPC - sensory feedback, movement control. Controls ...-generated movements. ...-controlled movements, ... coordination.

Externally-generated movements. | Visually-controlled movements, visuomotor coordination.

Damage to PPC - impaired ... motor adjustments. ... = difficulties ... and ... motor movements. Can ... them, but not ... to them.

Impaired vision-based motor adjustments. Apraxia = difficulties planning and adjusting motor movements. Can initiate them, but not adjust to them.

Ideomotor apraxia (4):

Distorded imitation and identification. Automatic intact, voluntary damaged Lesions in PMC, superior parietal areas. Deficit of visual input.

Ideational apraxia (3):

Know desired action but can't execute. Problems with motor plan/scheme. Lesions left inferior parietal.

PMC - ... feedback | PPC - ... feedback

PMC - contextual | PPC - visual

SMA - ...-generated movements planning, ... | SMA neurons are specialized in ...

Internally-generated movements, temporal ordering. | Specialized in certain sequences.

Damage in SMA - defects in ... ..., ... movements. ... syndrome - ... to lesion site.

Defects in appropriate action planning. Uncontrolled, unexpected movements. Alien-hand syndrome - contralateral to lesion site.

Externally-generated actions (4) versus internally-generated actions (4):

Externally: PMC, PPC, cerebellum, sensory feedback. Internally: SMA, PFC, basal ganglia, motivation to achieve goal.

Basal ganglia = ... nuclei to ... | ... of execution and inhibition.

Subcortical nuclei to gate action. | Timing of execution and inhibition.

Basal ganglia contain mostly ... neurons to ... planned actions ... ... from ... removes this ...

GABA neurons to inhibit planned actions until needed. | Go-input from cortex removes this inhibition.

Reward value of actions manipulates the degree of inhibition. Basal ganglia also contain ... neurons. Basal ganglia promote ... and inhibit ... actions.

Dopamine neurons. | Promote successful and inhibit unsuccessful actions.

Damage to basal ganglia causes ...: - positive symptoms: - negative symptoms:

PD. Positive: tremors, rigidity. Negative: instable posture, hypokinesia.

Hypokinesia

Partial/complete loss of muscle movement.

Causes of PD and treatment.

Loss of dopaminergic neurons in substantia nigra (SN). | Increase dopamine levels - only effective in early stages.

Cerebellum - close to brainstem containing many circuits for ... Smooth control of ... movements. Coordination of ... On-line error correction.

Automatic movements. Skilled movements. Repetitive movements.

Damage to cerebellum - deficits in ... Cerebellar ataxia = ... ... intact, no ... ... is off: agonist and antagonist muscles are activated ...

Deficits in peripheral limb coordination. Cerebellar ataxia = lack of control of voluntary movements. Initiation intact, no smooth control. Timing is off, muscles activated too late.

Early learning starts in ... to plan movement - then ... for visuomotor coordination - then ... - then ... for automatization and precision.

PMC - PPC - feedback - cerebellum.

3 areas mirror neurons:

PMC, PPC, parietal-temporal areas.

``` Spine - Brainstem - Basal ganglia - Cerebellum - M1 - PMC - PPC - SMA - ```

Spine – reflexes Brainstem – control of automatic reflexes Basal ganglia – inhibiting and controlling move onset Cerebellum – fine-tuning motor activity and error-correction M1 – control of simple movements PMC – planning and guiding actions PPC – external, visuomotor control SMA – internal, inhibition of actions