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MED 310 > reflexes > Flashcards

reflexes Flashcards

1
Q

what are the two functions of the spinal chord

A
  1. neuronal link bw the brain and the PNS
  2. integrating centre for spinal reflexes
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2
Q

how many pairs of spinal nerves are there

A

31

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3
Q

where do spinal nerves come out from

A

from spaces between adjascent vertebrae

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4
Q

how many pairs of cervical (neck) nerves are there

A

8

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5
Q

how many pars of thoracic (chest) nerves are there

A

12

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6
Q

how many pairs of lumbar (abdominal) nerves are there

A

5

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7
Q

how many pairs of coccygeal (tailbone) nerves are there

A

1

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8
Q

how many nerves of sacreal (pelvic) nerves are there

A

5

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9
Q

what connects spinal nerves with each side of the spinal chord

A

dorsal root and ventral root

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10
Q

what fibres are there in the spinal nerve

A

afferent and efferent fibres

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11
Q

what is a nerve

A

a bundle of peripheral neuronal axons enclosed by a connective tissue covering and following the same pathway

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12
Q

nerve fascicle

A

many axons bunbdled in connective tissue

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13
Q

how is white matter organized

A

into nerve tracts

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14
Q

what are nerve tracts

A

bundles of nerve fibres with a similar function. each begins or ends with a particular area of the brain

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15
Q

ascending nerve tracts

A

afferent, sensory input

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16
Q

descending nerve tracts

A

efferent, motor output

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17
Q

how many and what are the horns that divide up the grey matter

A
  1. dorsal horn: contains cell bodies of interneurons on which afferent neurons terminate
  2. ventral horn: contains cell bodies of efferent motor neurons supplying skeletal muscles
  3. lateral horn: contains cell bodies of autonomic sympathetic nerve fibres
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18
Q

reflex

A

involuntary stereotyped response to a sensory input occuring automatically without conscious effort linking biological stimulus with response

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19
Q

how many and what are the two types of reflexes

A
  1. simple or basic (innate)- built in unlearned responses
  2. acquired or conditioned reflexes (practice and learning)- result of practice and learning
20
Q

range of reflexes

A

simple to complex neural subroutines

21
Q

somatic (monosynaptic or polysynaptic)

A

somatic motor neurons and skeletal muscles
-spinal- integrated in spinal chord
-cranial- integrated in the brain

22
Q

autonomic or visceral (polysynaptic)

A

involve autonomic neurons (sympathetic or parasympathetic)
- spinal- urination/ defication
-integrated in brain- brainstem, hypothalamus, thalamus, homeostasis (gag, vomiting, sneezing, coughing, swallowing)

23
Q

how many components are in a reflex pathway

A

5

24
Q

what are the five components in a reflex pathway

A
  1. sensory receptor (muscle spindles in the case of somatic muscle reflexes)
  2. afferent pathway to CNS (sensory axon)
  3. integrating centre consisting of one or more synapses in the CNS
  4. efferent pathway to the periphery (motor axon)
  5. effector (mucsle)
25
Q

monosynaptic reflex

A

has a single synapse between the afferent and efferent neurons

26
Q

what kind of reflex is a stretch reflex

A

monosynaptic reflex

27
Q

example of stretch reflex

A

pateller tendon (knee jerk reflex)

28
Q

what is the preliminary assesment of the nervous system function

A

stretch reflex

29
Q

polysynaptic reflexes

A

have two or more synapsys

30
Q

example of a polysynaptic reflex

A

flexion (withdrawal) reflex
touching something hot

31
Q

muscle spindles

A

in muscles and sense stretch

32
Q

golgi tendon organ

A

in tendon and sense force

33
Q

joint receptors

A

sense pressure. position

34
Q

proprioceptros

A

skeletal muscle reflex sensory receptors

35
Q

isotonic contraction

A

alpha motor neurons are stimulated to generate contraction.

36
Q

muscle contraction and receptor response

A

alpha motor neurons are stimulated to generate contraction. the length changes by tension is constant. when the whole muscle mass shortens, the spindle also passively shortens. the firing rates of the spindle afferent axons are reduces because the tension in the receptor portion of the intrafusal fibres is relieved. without adjustment, they will no longer detect changes in muscle length

37
Q

function of v neurons

A

modulate sensitivty of the spindles

38
Q

unloading spindles

A

the intrafusal fibres slacken when a muscle shortens

39
Q

how is it ensured that info on cahnges in muscle length are transmitted

A

the CNS regulates the loading of the intrafusal fibres with v motor neurons

40
Q

what is this called “the CNS regulates the loading of the intrafusal fibres with v motor neurons”

A

innervation via reticulospinal and vestibulospinal tracts

41
Q

isometric contraction

A

a motor neurons are stimulated with the muscle firmly fixed at both ends. tension inc but length is constant therefore due to no change in length, the fiting of spindle afferents stays the same. tension is transferred to GTO and those afferents (IB) inc firing

42
Q

golgi tendon organs

A

sense tension

43
Q

loss or reduction of reflex

A

interruption of refllex arc by either peripheral sensory or lower motor neuron lesions (LMN). reduces or eliminates muscle stretch reflex and reduces muscle tone. loss of innervation to the muscle

44
Q

increased reflex and muscle tone (spasticity)

A

injury to upper motor neurons - UMN- above the anterior horn cell (spinal chord, motor cortex,) leads to loss of descending inhibition. increases muscle tone - hyperreflexia

45
Q

UMN

A

neurons in higher brain levels that influence neurons in spinal chord

46
Q

LMN

A

effector neurons in spinal chord

47
Q

muscle stretch reflex

A

MED 310 (47 decks)

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