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6a > CNS basic physiology > Flashcards

CNS basic physiology Flashcards

1
Q

Astroglia

A

integrate/modulate signals
part of BBB
part of synaptic transmission

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2
Q

Microglia

A

blood-borne macrophages

resident immune cells of the brain

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3
Q

AP propagation in the brain

A

1) NaV open, AP generated
2) passive current flows to the next NaV
3) passive current opens next NaV, another AP generated

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4
Q

Resistance (AP)

A

lower in larger axons

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5
Q

Capacitance (AP)

A

larger in larger axons - want to minimize this for faster current propagation
role of myelin sheath

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6
Q

Saltatory conduction

A

AP is not jumping; tunneling under myelin sheath

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7
Q

Synapse events

A

1) AP opens CaV channels
2) Ca influx causes NT-filled vesicles to fuse with the cell membrane
3) NT released into synaptic cleft; binds to receptors, causes opening of ion channels
4) postsynaptic cell depolarizes, AP generated

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8
Q

EPSP channels

A

Na channels

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9
Q

IPSP channels

A

Cl- channels

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10
Q

Amino acid NTs

A

Glutamine - ex
GABA - in
Glycine - in

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11
Q

Biogenic amine NTs

A

Dopamine - D1 ex, D2 in
Norepi, epi, histamine - ex
Serotonin - in or ex

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12
Q

Purine NTs

A

ATP - ex

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13
Q

Neuropeptide NTs

A

Substance P - ex
Met-enkephalin - in
Opioids - in
Adrenocorticotropin - ex

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14
Q

Synesthesia

A

Neurological phenomenon in which stimulation of one sensory pathway –> automatic, involuntary experiences in a second sensory pathway
e.g. Grapheme

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15
Q

Pressure receptor types (general)

A

Exteroceptors

Interoceptors and proprioceptors

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16
Q

Meissner’s corpuscles

A

light touch receptors

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17
Q

Palcinian corpuscle

A

deep pressure and vibration receptors
20-60 concentric lamellae composed of fibrous CT separated by gelatinous material
Centre: inner bulb, a fluid-filled cavity with a single afferent unmyelinated nerve ending

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18
Q

Ruffini’s corpuscle

A

sensitive to skin stretch sense of position and movement

19
Q

Merkel’s disc

A

sensitive to vibrations at low frequencies

20
Q

Temporal summation

A

frequency coding

more impulses along a single fiber

21
Q

Spatial summation

A

population coding

increasing number of parallel fibers that transmit information

22
Q

Adaptation

A

prolonged presence of a stimulus –> decreased perceived intensity
all sensory receptors adapt to constant stimulation, but rate of adaptation varies

23
Q

2-point discrimination

A

Helps to assess nerve damage

Depends on receptor density and size of receptive fields

24
Q

Lateral inhibition

A

Blocks lateral spread of excitatory signals –> increase degree of contrast in sensory pattern

25
Q

Alpha motor neuron

A

skeletomotor

innervate extrafusal fibers

26
Q

Gamma motor neuron

A

fusimotor
innervate intrafusal fibers
2 main types

27
Q

Small motor units

A

small number (e.g. 10) of fibers per motor neuron
fine movements
e.g. eye muscles

28
Q

Large motor units

A

large number (1000s) of fibers per motor neuron
gross movements
e.g. leg muscles

29
Q

Muscle spindles

A

stretch-sensitive mechanoreceptors
found in virtually all skeletal muscles
particularly dense in muscles connected with fine, manipulative tasks (intrinsic hand muscles, highest density in neck muscles for direction)
small, elongated structure - scattered among and parallel to contractile extrafusal fibers
CT sheath surrounding intrafusal muscle fibers

30
Q

Intrafusal fibers

A

modified muscle fibers lacking myofibrils in the centre
1/3 length of extrafusal fibers
Provide information about muscle length and velocity of contraction to the CNS

31
Q

Bag2 intrafusal fibers

A

largest
most important?
no striations in the middle region and swells to enclose nuclei
“bag”

32
Q

Bag1 intrafusal fibers

A

smaller than Bag2

33
Q

Bag intrafusal fibers

A

extend beyond capsule

based upon contraction speed and motor innervation

34
Q

Chain fiber3

A

half as long as bag, smaller diameter
row of nuclei in the middle
“chain”

35
Q

Typical muscle spindle

A

1 Bag1, 1 Bag2, 4 chain fibers

36
Q

Muscle spindle - sensory innervation

A

Large diameter group Ia afferent

  • enter capsules and branches
  • unmyelinated terminals wrap around fiber
  • annulospiral ending on nucleated Bag1, Bag2 and chain intrafusal fibers
  • All 3 types of intrafusal fibers receive innervation from Goup Ia afferents

Smaller group II afferents

  • enter with Ia afferents; unmyelinated spray terminals on one end of Bag 2 and chain fibers
  • no Bag1
37
Q

Muscle spindle - motor innervation

A

Gamma or fusimotor neurons
2 types of gamma:
1) static - Bag2 and chain
2) dynamic - Bag1 ONLY

38
Q

Muscle spindle function

A

Sensory neurons fire when centre intrafusal fiber stretches
Opening of spiral endings and initiation of impulses: stretch-operated cation channels; membrane depolarization and action potential firing
Viscoelastic properties affect activation
Ends of intrafusal fibers contract when stimulated by gamma motor neurons –> affect centre of intrafusal fibers, not overall muscle tension
Group Ia: muscle length and velocity info
Group II: length only
Gamma dynamics: increases velocity sensitivity
Gamma static: increases length sensitivity

39
Q

Muscle spindle sensory neurons

A

tonically active
Fire AP when muscle is at resting length
Signal to alpha motor neurons in ventral horn
tonic excitation –> muscle contraction in extrafusal fibers = resting muscle tension
Firing rates of gamma MN can change in different situations

40
Q

Stretch reflex

A

Intrafusal fibers stretched –> sensory neurons fire more rapidly
Reflex contraction of muscle to relieve stretch –> stimulus removed (negative FB)
Monosynaptic and polysynaptic excitatory connections between Group Ia and II afferents and alpha motor neurons

41
Q

Myotatic unit

A

collection of nervous pathways controlling a single joint

42
Q

Reciprocal inhibition

A

Relaxation of antagonist muscle during agonist contraction

Divergent pathways in spinal cord and inhibitory interneurons

43
Q

Hoffman reflex

A

electrically evoked analogue of the stretch reflex

44
Q

Ia inhibitory interneuron

A

receives convergent input from CST and other descending pathways

6a (26 decks)

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