A&P 2.4 stretch reflex, CNS anatomy Flashcards Preview

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Flashcards in A&P 2.4 stretch reflex, CNS anatomy Deck (24)
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Reflex arc

Fast and involuntary action in response to a stimulus
Simplest form of integration
Shortest pathway from a stimulus to a response

7 steps

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Stretch reflex

Defined

Myotatic reflex - causes the contraction of a skeletal muscle (the effector) in response to stretching the muscle.

Example: knee jerk reflex

7 steps

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Myotatic

Of the muscle

3

Stretch reflex

Knee jerk example

Stimulus

Stretch the muscle belly via tap on tendon or muscle

4

Sensory receptor

Dendrite or specialized structure that stimulates a dendrite = muscle spindle

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Sensory neuron

Afferent - conducts a nerve impulse from receptor to the CNS

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Integrating center

Sensory neurons synapse (directly with motor neurons therefore are MONOSYNAPTIC)


NO INTERNEURON OR ASSOCIATION NEURON

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Motor neuron

Efferent - conducts a nerve impulse from the CNS to an effector

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Effector

The muscle that was stretched

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Response

Muscle contraction

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Muscle spindle

Three bullets

Specialized structure that stimulates a dendrite

- PNS subtype: proprioceptors- found in muscles, fascia and tendons
- cellular characteristics: free nerve ending, simple, encapsulated
- stimulus: mechanoreceptor- main function is to measure muscle length and respond to sudden or prolonged stretching of muscle spindle fibers

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MONOSYNAPTIC

Only one synapse in the CNS

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Knee jerk example

Three steps

- Quads are stretched by tapping on the tendon
- quads are the agonist/prime mover and contract
- hamstring are the antagonist are inhibited by reciprocal innervation

Ipsilateral reflex- entire reflex from stimulus to response happens on 1 side or the same side of the body

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Argonist

Prime mover

Muscle that's contracting

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Antagonist

Muscles opposing the contraction/ muscles that do the opposite action at the SAME JOINT

Prime stopper

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Ipsilateral

One side or same side

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Reciprocal innervation

When a stretched muscle contracts during a stretch reflex, antagonist muscles oppose the contraction relax. Reciprocal innervation prevents conflict between opposing muscles and is vital in coordinating body movements. These are motor pathways that excite a muscle and simultaneously inhibit its' antagonist.

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Reflexes categorized according to

2 things

Effector: Somatic versus visceral

Location of integration: spinal versus cranial

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Effector

Somatic- body(skeletal, muscles, bones, fascia)

Visceral- organs in the abdomen, often G.I tract (example: defication after eating)

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Location of integration

Spinal reflexes - integration in the grey matter of the spinal cord; includes most proprioceptive and pain reflexes are spinal (including stretch reflex)

Cranial reflexes - integration takes place in the brain stem; eye reflex, startled reflex, propriocepative/pain reflex

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Propriocepative/pain reflex

Mostly spinal reflexes unless arising muscles are innervated by cranial nerves

Examples: muscles of the head, face, jaw, SCM, trapezius

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Startled reflex

Looking in the direction of the stimulus

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Teres minor

A, I, O

A - laterally rotate the shoulder, stabilize the head of the humerus in the glenoid cavity

O - upper 2/3 of lateral/axillary border

I - greater tuberercle of the humerus

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Subscapularis


A, I, O

A - medially rotate the shoulder, stabilize the head of the humerus in the glenoid cavity

O - subscapular fossa of the scapula (costal surface of the scapula)

I - lesser tubercle of the humerus