Lecture 3 Test 3 Flashcards by Eric Barretto

What are the 4 spinal reflex pathways?

Stretch reflex
Tendon reflex
Withdrawal reflex
Crossed extensor reflex

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Which reflex are for muscle stretch/tension?

Stretch reflex
Tendon reflex

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Which reflex are for pain?

Withdrawal reflex
Crossed extensor reflex

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Gives feedback to the CNS when muscles are stretched or contraction has occurred and elicit a reflex

Tension sensors

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Can sensory fibers go all the way through the dorsal horn and project a synapse to the anterior motor neuron?

Yes if the signal is strong enough

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A “bridge” for the sensor neuron and motor neuron.

Interneuron releasing inhibitory transmitter

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Most common signal that uses efferent pathway out of the CNS?

Motor output

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Reflexes can affect which side of the body?

Sometimes 1 side and sometimes both

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How does the L side of the sensor neuron talk to the R side?

Through the Interneuron

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Goal of stretch reflex

To keep posture constant for support. Stretch and contraction of muscles helps keep us standing straight

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Stretch sensors can go through the cord and synapse to ___

Motor neuron (anterior of the cord)

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Do we use interneurons for the stretch reflex?

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“spring” found within the muscle that sense the tension in the muscle

Muscle spindles

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Test for stretch reflex

Hit the patellar tendon/ligament with a rubber mallet

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Senses large amount of tension within the tendon/muscles

Tendon reflex

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build up of collagen and fibrin tissues

Tendon

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What happens when there’s massive tension placed on the muscles/tendon?

Stretch sensors activated and tells muscles to relax to prevent tendon tears.

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What doesn’t break when you fall of a tree?

Muscles

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What prevents muscles from being pulled out of tendons/muscle insertion points?

Tendon reflex

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If tendon reflex are protective, how can someone lift a car off a kid during an emergency??

The body has a way of overriding this but I don’t know how.

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2 groups of interneurons

Excitatory and inhibitory

If there’s tension in the quadricep muscle, tendon reflex would cause relaxation of the quads and reflex of the hamstring. This is called?

antagonistic muscle contraction

(unilateral ) Flexor reflex is also called…

Withdrawal reflex (unilateral)

What pulls the limb away from the pain source? (ex. toe hits a nail)

Flexor/withdrawal reflex (unilateral)

In order for the flexor reflex to function faster, what gets involved?

Antagonistic muscle contraction

What part of the cord is involved with flexor reflex?

Many levels up the cord and down the cord (2 up, 2 down) for better results

What type of neurons are involved with flexor reflex?

Ascending and descending interneuron

Where can you find the ascending/descending interneurons?

In the white matter between the tip of dorsal gray horn and tip of the cord "Tract of Lissauer"

more levels involved with flexor reflex =

better result

Which pain reflex involves both sides of the cord?

Crossed extensor reflex

What interneurons do we use for crossed extensor reflex? (ex. L side of body contracts, R side relaxes)

(Left) Ascending/descending interneurons (Right) Ascending/descending interneurons

When do we usually use the crossed extensor (pain) reflex?

During an activity (walking, shifting weight)

Which reflexes uses the most interneurons?

Crossed extensor reflex

What can inhibit these reflexes?

Spinal block

How do you know how deep is the spinal block?

Check for reflexes

Main purpose of reflexes?

Protecting the body from harm

Different types of n-Ach-R

Low conductance channel (immature) "fetal" High conductance channel (mature) "adult" a7 ACH-R (in CNS)

Where can you find n-Ach-R in adults?

NMJ of skeletal muscles

5 binding domains of "mature" n-ACh-R

a/a1 - where acetylcholine binds b1, d, E

Meaning of "high conductance" in mature n-ACh receptor

High speed when it's open for ions to flow in but a short period of time

4 binding domains for "immature" n-ACh-R

a/a1, b1, y, d

Where can you find n-Ach-R in infants?

NMJ and periphery of skeletal muscles (outside NMJ)

Meaning of "slow conductance" in immature receptor

shorter/slower ion flow but stays open longer.

Binding domains for a7 ACh-R

a7 acetylcholine

Succs in adult vs fetal n-ach-r

prolongs depolarization in adult but even longer for the fetal receptor.

When injury (stroke) occurs the body does what to n-ACh-R? ex. when the brain tells the muscle to contract but the feedback "spring" doesn't confirm the contraction, CNS thinks something is wrong)

increase immature n-ACh-R availability

If you give succs to a stroke Pt...

Depolarized way longer d/t immature receptors and more potassium leak in ECF (V-fib).

What is the junctional zone?

- Perijunctional area (near the outside of junctional area) - Junctional area - Postjunctional area (borders of muscle)

Paralytics main purpose?

Preventing the neuron to talk to the muscle.

Are there n- ACh-R located in the post junctional area?

No, only in the peri and junctional area.