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Tutorial 3 Subcortical areas

and anatomy of reflexes

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Objectives of this session:

Students will be able to:

Identify subcortical areas of the brain anddescribe basic function of each area

Identify components of reflexes and

differentiate between various somaticreflexes

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Brainstem

2. Relay point from SCto cerebral cortex

1. Cranial nerve supply

3. Integrative functions

- Respiration

- CV function

- Eye movement- Equilibrium responses

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Thalamus

Processing from many

areas (cortical and sub-cortical)

Control over autonomic functions

Integrative functions with brain stem

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Basal Ganglia

Thalamus

Receive inputs

from multiple

areas of the

cerebral cortex

Influence

movement via

projection to

thalamus

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Neurosurgery Correcting Movement Disorders

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LIMBIC LOBE

Concerned with

emotional state

Influences on

motor

performance

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Cerebellum

Comparator

receives afferent input

spinal cord and compares this to

commands from motor areas of

cerebral cortex.

Adjusts

motor responses bycomparing sensory signals

with motor plan

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Elements of reflex

Stimulus (to a receptor)

Response (of muscle)

Involuntary

Immediate

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Reflex vs VoluntaryReflexes

Voluntary movements

Rhythmic movements

Reflex

Most automatic/

Least controllableLeast automatic/

Most controllable

Rhythmic Voluntary

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Muscle spindles

Muscle length detection

Absolute

Rate

Under CNS control

Modifiable response

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Muscle spindle

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Muscle spindle

Two types of

sensory endings

Primary endingSecondary ending

Innervation

Gamma motor

neurons

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Monosynaptic reflex

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Activity 1 PNF stretching

Proprioceptive Neuromuscular Facilitation (PNF) works on modifying the muscle

spindle responses in order to increase the stretch in a muscle

PNF works on a contraction-relaxation-stretch protocol

- Slight variations in PNF methods but all work off this model

Break up into pairs partnered stretching of hamstrings

1. Traditional static stretch lying prone, partner takes leg and passively

stretches for 30s holds relax and repeat 2 to 3 times take note of how

much stretch improvements are made

2. PNF stretch lying prone, partner takes leg to point of stretch, person now

contracts against that stretch for 10s. Relax leg, and return stretch (should

now be further than previously) and repeat 2 to 3 times take note hof how

much stretch improvements are made

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Golgi tendon organ

Monitor tension

Rate and force production in

muscle

Safety device

Prevent tearing of muscle

Not always possible!

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Golgi tendon organ

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Golgi tendon organ

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Reciprocal Innervation

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Reciprocal activation

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Adaptability of reflexes

Under normal

conditions reflexes

can be modified to

adapt to the task

and control

movements in a

purposeful manner

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Activity 2 reflexes

See worksheet and work in small groups

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Kohnstamm's phenomenon

Forceful isometriccontraction

Provides aftermovementMechanisms not fully known

Thought to be increase in

spinal reflex activity

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Control of movement reflexes

Crossed-extension reflex

Flexion-withdrawal reflex

Stretch reflex

Deep tendon reflex

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Other reflexes

Plantar reflex

Downward flexion of

toes

Integrity of motor cortexand corticospinal tract

Babinskis sign

Abnormal response

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Crossed-extension reflex

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Crossed-extension reflex

Action in stimulated limb with opposite effect

in contralateral limb

excitation of extensor muscles inhibition of flexor muscles.

Serves to enhance postural support during

withdrawal of a foot from a painfulstimulus.

Counteracts the increased load onto one limb

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Flexion-withdrawal reflex

Mediated via

polysynaptic pathways

Ipsilateral excitation

Withdraw from stimulus

Contralateral excitation

Balance opposing leg

Inhibitory interneurons

Relax antagonist

muscles

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Flexion-withdrawal reflex

Stereotypical reflexes are subject to stimulus

Force of muscle contraction depends on

stimulusLight stimulus slightly hot stove plate

Extreme stimulus very hot stove plate

Duration of reflex increases with stimulus

intensityEvoked contractions always outlast stimulus

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Deep tendon reflex