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FM1010 > P: Reflexes > Flashcards

P: Reflexes Flashcards

1
Q

What is a reflex

A

An involuntary stereotyped but coordinated response to specific stimulus

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2
Q

What is a muscle spindle

A

Stretch receptor

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3
Q

What are golgi tendon organs

A

They are located at junction between tendon and muscle; sensitive to muscle force/tension

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4
Q

Two classifications of reflexes

A

Somatic - voluntary
Autonomic - involuntary

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5
Q

What root do afferent nerves enter the spinal cord (sensory nerve)

A

Dorsal root

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6
Q

Name the 6 essential components of a reflex

A

Stimulus
Sensory receptor
Afferent nerve fibre
Synapse
Motor fibres
Effector organ

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7
Q

What are spindle fibres made of

A

Intrafusal muscle fibres

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8
Q

What is the orientation of intrafusal muscle fibres and what does this allow

A

Lie parallel to extrafusal fibres (main contracting fibres in muscle)
Therefore responds to length changes in the muscle

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9
Q

What two types of tissue do intrafusal fibres have and where

A

Non contractile at centre
Contractile at the poles (ends)

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10
Q

What are the two types of intrafusal fibres

A

Nuclear bag
Nuclear chain

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11
Q

What do the primary (annulospiral) nerve endings do in the spindle

A

Type 1A afferents
Detect amount of muscle stretch and rate of stretching (dynamic response)

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12
Q

What are primary nerve endings

A

Type 1A afferents
Myelinated , rapidly conducting neurons
Faster and larger than type 2
Detect muscle stretch + rate of change of stretching

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13
Q

What do the secondary flower spray endings do

A

static response

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14
Q

Secondary flower spray endings properties

A

Type 2 afferents
Myelinated
Slower conduction than type 1
Respond to maintained stretch

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15
Q

What do primary sensory nerve endings innervate

A

Both nuclear bag and chain fibres

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16
Q

What do the secondary flower spray endings innervate

A

mainly nuclear chain fibres

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17
Q

What is the motor innervation of spindle and where

A

Gamma motor neurons
Innervate contractile fibres at the poles

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18
Q

What is meant by the spindle being unloaded or slack

A

Occurs after reflex contraction
Over relaxed /under stretched

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19
Q

How is a slack spindle reloaded

A

Gamma motor neurons cause contraction of intrafusal(spindle) fibres
Tightens the spindle
Allows it to continue to respond

20
Q

What’s the inverse myotonic reflex

A

Golgi tendon reflex

21
Q

What innervate the collagen of tendon

A

nerve terminals

22
Q

What happens if there’s excessive tension in contraction

A

GTO sends info to spinal cord via 1b afferents
Synapses with interneurons
Inhibition of contraction muscle
Reflex relaxation occurs

23
Q

Where are muscle spindle and stretch reflexes especially prominent

A

In anti gravity muscles
Neck muscles
Where fine control is required eg finger

24
Q

What does the GTO reflex prevent

A

Excessive force generation in a muscle

25
Q

What have a dampening/smoothing effect on jerky muscle movements

A

GTO and spindle fibres
Important in feedback control of muscle length in response to a load and prevent jerky movement

26
Q

What’s the most powerful reflex

A

Flexion (withdrawal) reflex

27
Q

What is the flexion reflex also called

A

Crossed-extensor reflex

28
Q

What information do dorsal columns carry

A
  • Proprioception
    • Discriminative touch
    • Pressure + vibration sense.
29
Q

Spinothalamic tracts transmit information regarding:

A
  • Pain
    • Temperature
    • Crude touch
  • Itch + tickle
30
Q

Difference between monosynaptic + polysynaptic reflexes

A

Monosynaptic - single synapse, no interneuron
Polysynaptic - many interneurones connect afferent and efferent motor signals.

31
Q

Stretch reflex:

A

Sensory receptor –> muscle spindle
Afferent nerve fibre –> IA afferents
Synapse –> spinal cord
Motor neuron –> alpha motor neuron
Effector organ –> skeletal muscle contracts

32
Q

Tonic receptors vs Phasic receptors

A
  1. Tonic receptors do not adapt to stimuli. Tonic receptors fire action potentials constantly. (pain)
  2. Phasic receptors adapt to stimuli rapidly; eventually the individual no longer senses the stimulus. Phasic receptors fire action potentials when the stimulus is initiated and when the stimulus is removed. (seeing your nose, feeling clothes on skin)
33
Q

What are dorsal columns made of

A

Large myelinated axons

34
Q

Where do the dorsal columns enter the spinal cord and where do they go

A

Enter spinal cord at different levels via dorsal route
Travel up the cord in a highly organised fashion

35
Q

What is somatotopic organization?

A

Correspondence of a specific point in the body to a specific point in the primary motor and sensory cortexes

36
Q

Where do dorsal columns synapse

A

In the medulla on either side of the dorsal column nuclei

37
Q

What are second order neurons also known as

A

Medial lemniscus

38
Q

Where do second order neurones synapse and become third order neurones

A

In the thalamus and travel up to the somatosensory cortex

39
Q

Definition of receptive field

A

The receptive field of a sensory neuron is an area of skin that, once stimulated, produces a response for that neuron.
Receptive fields vary inversely with numbers of receptors in the area (bigger the area, smaller the number of receptors)

40
Q

What are the different types of sensory receptors and their modalities?

A
  • Chemoreceptors –> chemical changes
  • Thermoreceptors –> warm and cold
  • Photoreceptors –> light
  • Mechanoreceptors –> pressure
  • Nocioreceptors –> noxious stimuli (generate pain)
  • Propioreceptors –> info about body and limb position
41
Q

How do sensory receptors transmit sensory information?

A

Action potentials are generated when generator potentials reach threshold for depolarization. Bigger the stimulus, greater number of APs generated.
Generator potentials = local graded changes in membrane potential

42
Q

What order neurons are dorsal columns?

A

First order neurons

43
Q

Damage to lower motor neurone?

A

Reduced stretch reflexes & flaccid paralysis

44
Q

Physiological benefit of stretch reflex

A

Muscle tension, posture maintenance

45
Q

Name the sensory receptor for stretch reflex + what stimulates it?

A

Mechanoreceptors - length changes in muscle

46
Q

Define gamma motor neuron

A

Innervates intrafusal fibres of muscle spindle

47
Q

What stimulates GTO receptors

A

Proprioceptors detect muscle contraction

FM1010 (50 decks)

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