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Psychology Psychology 210210

Lecture 6Lecture 6

Kevin R SmithKevin R Smith

The motor systemThe motor system

�� OutlineOutline

•• MusclesMuscles

•• ReflexesReflexes

•• Brain motor systemBrain motor system

•• Disorders of movementDisorders of movement

Types of MusclesTypes of Muscles

�� Smooth muscleSmooth muscle

•• Digestive tractDigestive tract

•• ArteriesArteries

•• Reproductive systemReproductive system

•• Controlled by autonomic nervous Controlled by autonomic nervous

systemsystem

�� Striated muscle: Two typesStriated muscle: Two types

•• Cardiac muscleCardiac muscle

•• Skeletal muscleSkeletal muscle

ReflexesReflexes

�� Monosynaptic reflexesMonosynaptic reflexes

•• Involves only one synapse (two Involves only one synapse (two

neurons)neurons)

�� Polysynaptic reflexesPolysynaptic reflexes

•• Involve more than one synapseInvolve more than one synapse

Monosynaptic reflexesMonosynaptic reflexes

�� Sensory neuron Sensory neuron

from muscle to from muscle to

spinal cordspinal cord

�� Motor neuron Motor neuron

from spinal from spinal

cord to musclecord to muscle

Polysynaptic reflexesPolysynaptic reflexes

�� Reciprocal Reciprocal

inhibitioninhibition

•• When one When one

muscle is muscle is

voluntarily voluntarily

contracted, contracted,

the other is the other is

automaticalautomatical

ly inhibitedly inhibited

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Polysynaptic reflexesPolysynaptic reflexes

�� Flexion reflexFlexion reflex

•• Jerking hand away Jerking hand away

from hot surfacefrom hot surface

•• Pain receptors Pain receptors

transmit info to transmit info to

interneuronsinterneurons in in

spinal cordspinal cord

•• InterneuronsInterneurons excite excite

the muscles and the muscles and

inhibit the inhibit the

reciprocal musclesreciprocal muscles

•• Leads to the actionLeads to the action

Reflexes changeReflexes change……..

�� Born withBorn with

•• RootingRooting

•• SteppingStepping

•• BabinskiBabinski

•• GraspingGrasping

�� All are gone by 1 year of ageAll are gone by 1 year of age

•• Never actually gone, but rather inhibitedNever actually gone, but rather inhibited

Pathway to the BrainPathway to the Brain

�� Two routesTwo routes

•• Lateral Lateral

pathwaypathway

�� Voluntary Voluntary

movementsmovements

•• VentromedialVentromedial

pathwaypathway

�� Automatic Automatic

processesprocesses

Lateral pathwayLateral pathway

�� Information comes from the motor Information comes from the motor

cortex or the red nucleus to the cortex or the red nucleus to the

spinal cordspinal cord

�� ContralateralContralateral organizationorganization

VentromedialVentromedial pathwaypathway

�� Posture Posture

�� Coordinating head and trunk Coordinating head and trunk

movements with eye movementsmovements with eye movements

�� Respiration, coughing, sneezingRespiration, coughing, sneezing

CerebellumCerebellum�� Does not appear to initiate Does not appear to initiate

movementsmovements

�� Plays a role in coordinating Plays a role in coordinating

movementsmovements

•• Contracts and relaxes the muscles at Contracts and relaxes the muscles at

the right times to produce a sequence of the right times to produce a sequence of

movementsmovements

�� Receives information from motor Receives information from motor

cortex via the cortex via the ponspons

�� Sends excitatory information back to Sends excitatory information back to

motor cortex via the thalamusmotor cortex via the thalamus

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Basal GangliaBasal Ganglia

�� Collection of cell Collection of cell

bodiesbodies

•• Caudate nucleusCaudate nucleus

•• PutamenPutamen

•• GlobusGlobus palliduspallidus

�� Like the cerebellum, Like the cerebellum,

receives information receives information

from the motor cortex from the motor cortex

and sends it back to and sends it back to

the motor cortex via the motor cortex via

the thalamusthe thalamus

•• The information is The information is

inhibitory thoughinhibitory though

The Basal GangliaThe Basal Ganglia

�� Damage can lead to ParkinsonDamage can lead to Parkinson’’s s

DiseaseDisease

�� TheoryTheory

•• Less Less dopaminergicdopaminergic activity in Basal activity in Basal

GangliaGanglia

•• Less inhibition of thalamusLess inhibition of thalamus

•• OverstimulationOverstimulation of thalamusof thalamus

•• Less activity in frontal lobeLess activity in frontal lobe

Symptoms of ParkinsonSymptoms of Parkinson’’s s DiseaseDisease

�� Difficulty movingDifficulty moving

�� Tremor in resting body partsTremor in resting body parts

�� Frozen facial expressionsFrozen facial expressions

�� Stooped postureStooped posture

�� Loss of balance, frequent fallsLoss of balance, frequent falls

�� Autonomic disturbancesAutonomic disturbances

�� Premature deathPremature death

Causes of ParkinsonCauses of Parkinson’’s Diseases Disease

�� Degeneration of substantia Degeneration of substantia nigranigra

(midbrain)(midbrain)

�� Less dopaminergic activity in basal Less dopaminergic activity in basal

gangliaganglia

�� Genetics in earlyGenetics in early--onset casesonset cases

�� Correlates with exposure to toxins:Correlates with exposure to toxins:

•• Synthetic heroinSynthetic heroin

•• Agricultural chemicalsAgricultural chemicals

•• SolventsSolvents

Treatments of ParkinsonTreatments of Parkinson’’s Diseases Disease

�� LL--DOPADOPA

•• Precursor to DopaminePrecursor to Dopamine

•• Leads to an increase in the amount of Leads to an increase in the amount of

dopaminergicdopaminergic activity throughout the bodyactivity throughout the body

•• Benefit: increases in dopamine levels in the Benefit: increases in dopamine levels in the

basal ganglia lead to a decrease in the PD basal ganglia lead to a decrease in the PD

symptomssymptoms

•• Cost: BAD side effectsCost: BAD side effects

�� Increases in dopamine levels throughout the body Increases in dopamine levels throughout the body

lead to issues with the liver and other organslead to issues with the liver and other organs

�� ONLY treats the symptoms, not the causeONLY treats the symptoms, not the cause

Motor cortexMotor cortex

�� Primary motor cortexPrimary motor cortex

�� Supplementary motor area (SMA)Supplementary motor area (SMA)

�� PremotorPremotor areaarea

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Primary motor cortexPrimary motor cortex Motor HomunculusMotor Homunculus

SMA and SMA and PremotorPremotor areasareas SMA SMA

�� Involved in the Involved in the planning of planning of controlled controlled movementsmovements

�� Receives Receives information from information from the visual pathway the visual pathway and send info to and send info to primary motor primary motor cortex and the cortex and the brainstembrainstem

PremotorPremotor areasareas

�� Involved in the Involved in the

sensory guidance sensory guidance

of movementsof movements

�� Orienting the body Orienting the body

correctly to pick up correctly to pick up

a glassa glass

�� The fine The fine

coordination coordination

needed comes needed comes

from the from the

cerebellumcerebellum

FeedbackFeedback

�� Motor systems are highly intertwined Motor systems are highly intertwined

with feedback from the visual systemwith feedback from the visual system

�� Gives the ability to change a Gives the ability to change a

movement throughout the movement throughout the

movementmovement

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Disorders of the motor systemDisorders of the motor system

�� ToxinsToxins

�� Myasthenia gravisMyasthenia gravis

�� Muscular dystrophyMuscular dystrophy

�� PolioPolio

�� Lou Lou GehrigGehrig’’ss diseasedisease

�� HuntingtonHuntington’’s Diseases Disease

�� ParkinsonParkinson’’s Diseases Disease

ToxinsToxins�� Cholinergic agonists Cholinergic agonists

(e.g. black widow (e.g. black widow

spider toxin) spider toxin)

overstimulateoverstimulate the the

neuromuscular neuromuscular

junction, producing junction, producing

convulsions followed convulsions followed

by paralysis.by paralysis.

�� Cholinergic Cholinergic

antagonists paralyze antagonists paralyze

muscles:muscles:

•• CurareCurare

•• BotulinumBotulinum toxintoxin

•• Cobra venomCobra venom

Myasthenia gravisMyasthenia gravis�� Autoimmune disorderAutoimmune disorder

�� Results in the breakdown of Results in the breakdown of acetylcholine (acetylcholine (AChACh) receptors on the ) receptors on the muscle fibermuscle fiber

�� Symptoms include extreme Symptoms include extreme weakness, fatigue, droopy eyelids, weakness, fatigue, droopy eyelids, slurred speech, difficulty swallowing slurred speech, difficulty swallowing and breathingand breathing

�� Treatments include medications that Treatments include medications that suppress the immune system or suppress the immune system or inhibit inhibit acetylcholinesteraseacetylcholinesterase ((AChEAChE))

Muscular dystrophyMuscular dystrophy

�� Heritable Heritable

conditions conditions

involving the involving the

muscle protein muscle protein

dystrophindystrophin..

�� Premature muscle Premature muscle

growth is followed growth is followed

by degeneration.by degeneration.

�� Gene therapy may Gene therapy may

provide effective provide effective

treatments soon.treatments soon.

PolioPolio

�� The polio virus The polio virus

destroys alpha destroys alpha

motor neurons.motor neurons.

�� Without neural Without neural

input, muscles input, muscles

degenerate.degenerate.

�� Vaccination may Vaccination may

eradicate polio eradicate polio

worldworld--wide in the wide in the

next few years.next few years.

Lou Lou GehrigGehrig’’ss DiseaseDisease

�� akaaka Amyotrophic Lateral Sclerosis Amyotrophic Lateral Sclerosis

�� Motor neurons in the spinal cord and Motor neurons in the spinal cord and

brainstem degenerate.brainstem degenerate.

�� 55--10% of cases are due to genetic defects10% of cases are due to genetic defects

•• The rest are sporadic: no known causeThe rest are sporadic: no known cause

�� Correlated environmental factors include Correlated environmental factors include

vigorous activity and viruses.vigorous activity and viruses.

�� Treatments for symptoms are being Treatments for symptoms are being

developeddeveloped

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HuntingtonHuntington’’s Diseases Disease

�� A genetically A genetically

programmed programmed

degeneration of degeneration of

neuronsneurons

�� Produces Produces

involuntary, jerky involuntary, jerky

movements, movements,

depression, depression,

hallucination and hallucination and

delusions.delusions.

HuntingtonHuntington’’s Diseases Disease

�� Heritable conditionHeritable condition

•• Parents with HD pass it on 50% of the Parents with HD pass it on 50% of the

timetime

�� Antibiotics and fetal tissue Antibiotics and fetal tissue

transplants and maintaining activity transplants and maintaining activity

may provide treatment in the future.may provide treatment in the future.