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PBL SEM 3 > 1 - intro to the nervous system lecture > Flashcards

1 - intro to the nervous system lecture Flashcards

1
Q

what is perception?

A

a constructive process in the brian that depends upon information about stimuli (sensations) and the mental structure of the perceiver
- derived from sensory input from nocicpetors

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2
Q

is pain subjective?

A

yes — it is a perception ie. a product of the brain
- the brains interpretation of sensory input means pain is subjective, therefore allowing different pain thresholds

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3
Q

what are some morphological features of a neurone?

A
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4
Q

what are the 4 reflex types?

A
  • stretch aka. monosynaptic
  • inhibitory
  • flexor
  • crossed extensor
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5
Q

what is a joint?

A

where 2 bones (or other hard surfaces) connect in the body:
- some joints allow movement (eg. hip, elbow)
- others lack movement (eg. sutures between skull bones)

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6
Q

tendons vs. ligaments

A

tendons — bind muscle to bone
ligaments — bind bone to bone

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7
Q

what does contraction of both flexor and extensor together result in?

A

stiffness at the joint with movement

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8
Q

flexion vs extension at joints

A
  • flexion — closing of a joint
  • extension — opening of a joint
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9
Q

what is the agonist and antagonist at the elbow joint during flexion/extension?

A

flexion:
- biceps = agonist
- triceps = antagonist

extension:
- biceps = antagonist
- triceps = agonist

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10
Q

for movement to occur, what must happen to the agonist and antagonist?

A

agonist must contract and antagonist must relax

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11
Q

what does activity in both the agonist and antagonist result in?

A

rigidity and tremor

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12
Q

what is the basic circuit in spinal cord reflexes?

A
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13
Q

what are the 2 basic parts of the simplest reflex?

A
  1. sensory, afferent neuron
  2. alpha motor neuron
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14
Q

what is the function of most reflexes?

A

protection

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15
Q

what is another naem for the stretch reflex?

A

myotatic reflex

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16
Q

in a stretch reflex, what happens when the tendon is tapped?

A

tapping the tendon causes that muscle to stretch slightly

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17
Q

what happens when the patellar tendon is tapped? (knee jerk reflex)

A
  • stretch of patellar tendon stretches the quadriceps
  • induces reflex quadriceps contraction
  • quadriceps is an extensor muscle, therefore contraction ‘opens’ the knee joint (straightens the leg)
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18
Q

what are the 2 types of muscle fibre?

A
  1. extrafusal fibres — forms the main body of muscle
  2. intrafusal fibres — forms the muscle spindle
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19
Q

what detects stretch?

A

sensory muscle spindle = a complex structure within muscles

20
Q

what is the spindle like when slack?

A

when slack there is no sensory output from the spindle — therefore no info being sent to the brain about muscle length

21
Q

what detects stretch?

A

mechanoreceptor eg. muscle spindle

22
Q

the spindle is in ____ with the main muscle fibres

A

parallel

23
Q

what happens when muscle fibres stretch?

A

spindle also stretches, increasing the sensory signal in its group 1a afferents

24
Q

where do the group 1a afferents project?

A

to the spinal cord via the dorsal horn

25
Q

what happens when muscle fibres contract?

A

the muscle length shortens, making the spindle fibres lose ‘tone’ (go slack) and stop signalling stretch

26
Q

how is the spindle muscle tone maintained during contraction?

A

gamma motor neurons excite the spindle’s intrafusal fibres

27
Q

how is measuring the amount of activity in gamma motor neurones useful?

A
  • helps estimate the true length of the main muscle
  • help to match the length of the muscle
28
Q

what is a motor unit?

A

the number of muscle fibres supplied by a motor neuron

29
Q

where do spindle 1a afferents synapse?

A

on alpha motor neurones in spinal cord

30
Q

small vs large number of motor units

A
  • motor units are small (low number of muscle fibres per motor unit) in order to deliver fine control of movements.
  • motor units are large (high number of muscle fibres per motor unit) for muscles involved in large, powerful movements where you need a small range of simple, powerful movements
31
Q

label

A
32
Q

describe the brief 5 steps that lead to muscle contraction in the monosynaptic stretch reflex

A
  1. stretching of muscle stimulates muscle spindles
  2. activation of sensory neuron (1a afferent)
  3. information processing at motor neuron
  4. activation of motor neuron (alpha motor neuron - efferent)
  5. contraction of muscle
33
Q

how is the stretch reflex protective?

A

prevents damage due to over-stretching of muscle fibres

34
Q

why is describing the stretch reflex as monosynaptic only partially correct? use knee jerk reflex as example

A
  • patellar tendon stretch causes reflex contraction of the quadriceps muscle (agonist) to extend the knee joint (via synapse at 1)
  • for this to occur the flexor (hamstrings; antagonist) must be inhibited (via synapse at 2 and inhibitory interneuron)
35
Q

what is clonus?

A

a neurological condition that creates involuntary muscle contractions

36
Q

what can deficitis in the control of the agonist and antagonist muscle by spinal interneurons result in? where is this often seen?

A

abnormal oscillation of flexion and extension around a joint (clonus) — often seen in spasticity

37
Q

what is spasticity?

A

abnormal increase in muscle tone or stiffness

38
Q

what is a golgi tendon organ? describe them

A

= another muscle proprioceptor at the junction of tendons and muscle fibres
- lie in SERIES with muscle fibres (spindles are in parallel)
- respond to tension developed by muscle during isometric contractions
- prevent heavy loading of msucle causing damage
- work by activating INHIBITORY INTERNEURONS to relax the muscle immediately
- 1b afferent

39
Q

why can golgi tendon organ detect loading and a muscle spindle cant?

A

muscle spindle — in PARALLEL therefore just detects stretch/muscle length

golgi tendon organ — in SERIES

40
Q

what kind of fibres are golgi tendon organ?

A

1b afferent

41
Q

how do golgi tendon organs work?

A
  • neuron from golgi tendon organ fires - 1b afferent
  • motor neuron is inhibited
  • muscle relaxes
  • load is dropped
42
Q

describe the flexor reflex

A
43
Q

describe the crossed extensor reflex

A
44
Q

why do people with Parkinson’s disease walk with a wide gate?

A

cant control movements very well so centre of gravity is not central and moves around a lot — therefore walk with wide gate to try and keep centre of gravity central

45
Q

what happens to motor neurons in spina bifida?

A

apoptosis of motor neurons — dysfunction of limbs

reflexes sometimes okay day 1 but bad by day 7

46
Q

surgery in spina bifida?

A

= prevents further damage
— cannot repair damage already made in terms of motor neurons
— prenatal repair offers very good chance of maintaining spinal (lower) motor function
— postnatal surgery stabilises but doesn’t repair

PBL SEM 3 (49 decks)

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