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6a > CNS basic physiology > Flashcards

CNS basic physiology Flashcards

(44 cards)

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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

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A

sensitive to skin stretch sense of position and movement

19
Q

Merkel’s disc

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A

sensitive to vibrations at low frequencies

20
Q

Temporal summation

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A

frequency coding

more impulses along a single fiber

21
Q

Spatial summation

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A

population coding

increasing number of parallel fibers that transmit information

22
Q

Adaptation

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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

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A

Helps to assess nerve damage

Depends on receptor density and size of receptive fields

24
Q

Lateral inhibition

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A

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

25
Alpha motor neuron
skeletomotor | innervate extrafusal fibers
26
Gamma motor neuron
fusimotor innervate intrafusal fibers 2 main types
27
Small motor units
small number (e.g. 10) of fibers per motor neuron fine movements e.g. eye muscles
28
Large motor units
large number (1000s) of fibers per motor neuron gross movements e.g. leg muscles
29
Muscle spindles
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
Intrafusal fibers
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
Bag2 intrafusal fibers
largest most important? no striations in the middle region and swells to enclose nuclei "bag"
32
Bag1 intrafusal fibers
smaller than Bag2
33
Bag intrafusal fibers
extend beyond capsule | based upon contraction speed and motor innervation
34
Chain fiber3
half as long as bag, smaller diameter row of nuclei in the middle "chain"
35
Typical muscle spindle
1 Bag1, 1 Bag2, 4 chain fibers
36
Muscle spindle - sensory innervation
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
Muscle spindle - motor innervation
Gamma or fusimotor neurons 2 types of gamma: 1) static - Bag2 and chain 2) dynamic - Bag1 ONLY
38
Muscle spindle function
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
Muscle spindle sensory neurons
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
Stretch reflex
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
Myotatic unit
collection of nervous pathways controlling a single joint
42
Reciprocal inhibition
Relaxation of antagonist muscle during agonist contraction | Divergent pathways in spinal cord and inhibitory interneurons
43
Hoffman reflex
electrically evoked analogue of the stretch reflex
44
Ia inhibitory interneuron
receives convergent input from CST and other descending pathways

6a (26 decks)

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