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physiology > nerve cells & connections > Flashcards

nerve cells & connections Flashcards

1
Q

name the 2 nervous systems

A

CNS, PNS

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2
Q

name the separate components of the CNS

A

brain and spinal cord

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3
Q

name the separate components of the PNS

A

autonomic and somatic nervous system

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4
Q

name the components of the autonomic nervous systems

A

sympathetic, parasympathetic, enteric nervous system

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5
Q

what is the smooth section of the brain

A

sulcus

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6
Q

what is the ridges of the brain

A

gyrus

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7
Q

name the sections of the brain

A

cerebellum, cerebrum, diencephalon, brainstem

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8
Q

what is the meninges

A

connective tissue that covers the brain to suspend the brain

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9
Q

name the 4 lobes of the cerebrum

A
  • Frontal lobe
  • Temporal lobe
  • Parietal lobe
  • Occipital lobe
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10
Q

name the 2 components of the diencephalon

A
  • Thalamus
  • Hypothalamus
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11
Q

name the 3 components of the brainstem

A
  • Midbrain
  • Pons
  • Medulla oblongata
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12
Q

what different types of spinal nerves does the spinal cord contain and how many pairs are there

A

31 pairs of spinal nerves
cervical, thoracic, lumbar, sacral, coccygeal

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13
Q

how many lumbar and sacral in the spinal word, provide where they are located

A

5 lumbar : hips and legs
5 sacral: Genitalia and gastrointestinal tract

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14
Q

how many cervical, coccygeal & thoracic in the spinal word, provide where they are located

A

12 thoracic : chest & abdomen
1 coccygeal
8 cervical : neck, shoulders and arms

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15
Q

determine the difference between dorsal and ventral

A

ventral refers to the front of the body, and dorsal refers to the back

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16
Q

describe the pathway of a stimulus using the spinal cord cross section, include grey/white matter

A

afferent –> dorsal root ganglion –> grey matter (interneuron) –> ventral root –> efferent
(need to go through which matter go get to grey both in and out)

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17
Q

what and where is the axon hillock in a neuron

A

initial segment of axon that triggers A.P, located in end of cell body and start of the axon

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18
Q

what is the soma of a neuron

A

cell body, contains nucleus

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19
Q

name 3 different types of neurosn

A

afferent, interneurons and efferent neurons

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20
Q

describe the pathway of an electrical impulse using the different types of the neurons

A

stimulus–>afferent sensory receptor –> interneurons –> efferent motor neuron –> muscle/gland/neuron

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21
Q

provide the different types of morphologies of the afferent sensory neuron and describe what they look like

A

bipolar and pseudo unipolar, 1 dendrites and 1 axons on either side

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22
Q

provide the different types of morphologies of the interneuron and describe what they look like

A

multipolar and anaxonic, cell bodies are in the middle of neuron, which more than 2 dendrites and axons

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23
Q

provide the different types of morphologies of the efferent motor neuron and describe what they look like

A

multipolar, cell body is at the end of the neuron

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24
Q

what are the 4 types of glia in CNS

A

Astrocytes, Oligodendrocytes, Microglia, Ependymal cells

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25
Q

what is the function of astrocytes (glia type)

A

Maintain external environment for the neurons
Surround blood vessels and form blood brain barrier

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26
Q

what is the function of oligodendrocytes (glia type)

A

form myelin Ssheath

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27
Q

what is the function of microglia (glia type)

A

macrophages of the CNS, hoover up infection

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28
Q

what is the function of ependymal cells (glia type)

A

produce cerebrospinal fluid

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29
Q

what are the 2 types of glia in PNS

A

Schwann cells and satelitte cells

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30
Q

what is the role of Schwann cells and satellite cells

A

Schwann: forms myelin sheath
Satellite: support neuron cell bodies

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31
Q

what is a graded & action potentials

A

A.P : Transmit signals over long distances
G.P : Decide when an action potential should be fired

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32
Q

what is the role of the Resting membrane potentials

A

Keeps cell ready to respond

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33
Q

why is the K channels know as leaky in the membrane

A

K+ leaks out down its concentration
gradient
* This builds up an electrical gradient

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34
Q

how does the conc. gradient and electrical gradient help maintain the resting membrane potential, regarding K+ ions

A

CG: K+ being pulled out cells
EG: K+ being pulled into cell

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35
Q

what does the the Nernst equation tell us

A

predicts the equilibrium potential for a single ion species

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36
Q

what is the Gold-Hodgkin-Katz equation measure

A

Predicts the equilibrium potential generated by several ions

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37
Q

how does the fact that the Na+/K+ pump is electrogenic mean

A

producing a change in the electrical potential of a cell

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38
Q

why is the leaky K+ channels needed

A

Without leaky K+ channels, only a small membrane potential would be generated

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39
Q

what happens if too much K+ is ingested

A

reduces K+ conc. grad. –> smaller electrical gradient at equilibrium –> resting membrane potential reduces –> cell depolarises –> neurons to fire A.P –> seizures

e.g. -70 to -50 mV

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40
Q

how does the B.B.B protect the brain

A

prevents changes in plasma as capillaries of the brain are especially “tight”
K+ (other polar substances) cannot cross through/or/between, the endothelial cells

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41
Q

provide examples of graded potential

A

Generator potentials
Postsynaptic potentials
End plate potentials
Pacemaker potentials

42
Q

where are the graded potentials located

A

Generator potentials
* At sensory receptors
Postsynaptic potentials
* At synapses
End plate potentials
* At neuromuscular junction
Pacemaker potentials
* In pacemaker tissues

43
Q

why are graded potentials called local potentials

A

as they only useful over a short distance
graded potentials are decremental- become smaller as they travel along the membrane

44
Q

do graded potentials excite or inhibit a cell

A

both as it depends on magic firing threshold
the Neurotransmitters can open channels that depolarise the cell, or different channels that hyperpolarise the cell

45
Q

what does the phrase ‘graded potentials can summate’ mean

A

A single neuron has lots of synapses, evoking their own postsynaptic potential
* If two occur at the same time, they can add to together
* This is important for synaptic integration

46
Q

provide a summary of the properties of the graded potentials

A

decremental, depolarising/hyperpolarising, summate

47
Q

provide the summary of the an ionic basis of graded potentials (EPSP and IPSPs)

A

EPSPs generated by opening NA+/K+ channels or closing leaky K+ channels
IPSPs generated by opening CL- channels or opening K+ channels

48
Q

describe ionic basis of AP using voltage

A

-70mV= resting potential, K+ in
40mV = K+ out and Na+ mV
-90mV = hyperpolarisation, K+ out

49
Q

what type of threshold do AP potentials have

A

all or nothing

50
Q

whats is a refractory period and where is it found

A

refractory period is is the time in which a nerve cell is unable to fire an action potential (nerve impulse)

in an AP

51
Q

do ionic, pacemaker APs travel fast/slow and why

A

slowly as no fast Na + channels , slower action potentials in SA node in terms of how rapidly they depolarize. Therefore, pacemaker AP are slow

52
Q

how is the stimulus encoded in the APs

A

through intensity of firing freq., not amplitude

53
Q

how to speed up an action potential in axon

A

large axon diameter, reduces axial resistance
&
myelination

53
Q

what’s the difference of channels between the postsynaptic & action potentials

A

action potentials : all mediated by voltage gated channels
postsynaptic: ligand gated channels

54
Q

describe what a larger axon diameter does

A

Electric current flows more easily down a large axon than a small axon (axial resistance is lower)
* Allows the Na+ channels to be more spaced out along the membrane

55
Q

provide examples of animals with large axons

A

squid/ fish/ earthworms

56
Q

define saltatory conduction

A

A.P spreads passively from node to node and still reach threshold

57
Q

what do the demyelinating diseases do to an axon

A

diseases attack the myelin sheath,
decreased membrane resistance –> more current leaks out of membrane
increased membrane capacitance more current wasted changing up the membrane
conduction fails

58
Q

nerve fibre type

A

Aα , Aβ, Aγ, Aδ, C

59
Q

describe Aα (a nerve fibre type)
anatomy? velocity? function?

A

largest
myelinated
70-120 m/sec Proprioception,
motor neurons

60
Q

describe Aβ (a nerve fibre type) anatomy? velocity? function?

A

Large
myelinated
30-70 m/sec
Touch, pressure

61
Q

describe Aγ (a nerve fibre type) anatomy? velocity? function?

A

Small
myelinated
15-30 m/sec
Motor neurons of muscle spindles

62
Q

describe Aδ (a nerve fibre type) anatomy? velocity? function?

A

Smallest
myelinated
12-30 m/sec
Touch, cold, “fast” pain

63
Q

what generates a compound action potential

A

different nerve fibre types/axons all conduct different velocities therefore

extracellular recordings from a nerve (bundle of axons)

64
Q

what’s A.P and compound A.P
type of recording ?
where?

A

AP: intracellular recording
microelectrode through membrane
relative to outside the cell
C A.P: extracellular recording
electrodes outside axons
each A.P very small but add up to large waves

65
Q

what is the neuromuscular junction

A

synapse between the motor neuron and skeletal muscles

66
Q

what is the first step in triggering muscle contraction

A

it is to evoke an action potential in the skeletal muscle membrane (the sarcolemma)

67
Q

name the 3 sections of the neuromuscular junction

A
  • Presynaptic terminal filled with vesicles containing acetylcholine(ACh)
  • Synaptic cleft
  • Postsynaptic end plate of the skeletal muscle fibre

Note the folds of the end plate

68
Q

descrie the processes within the neuromuscular junction

A
  1. Action potential in motor neuron
  2. Fusion of vesicles (Ca2+-dependent exocytosis)
    3 ACh diffuses across synaptic cleft
  3. ACh binds to ACh (nicotinic) receptors
  4. Opens ligand-gated Na+/K+ channels
  5. Evokes end plate potential (graded potential)
  6. (Always) depolarises membrane to threshold
  7. Opens voltage- gated Na+ channels
  8. Evokes action potential
  9. Muscle contracts
  10. Acetylcholine cleared up
    by acetylcholinesterase
69
Q

the neuromuscular junction: key characteristics: what evokes end plate potentials

A

Ligand-gated Na+/K+ channels
evoke the end plate potentials

70
Q

the neuromuscular junction: key characteristics: describe the graded potential and also its relation to threshold

A

Very large graded potential,
always big enough to reach
threshold

71
Q

the neuromuscular junction: key characteristics: describe the function of post junctional folds

A

increase number of voltage-gated Na+ channels close to where it is evoked

72
Q

the neuromuscular junction: key characteristics: synaptic integration and define it

A

No synaptic integration occurs here, it acts more like a switch

SI: where multiple inputs combined from multiple neurons to generate AP

73
Q

describe the range of postsynaptic potentials

A
  • Fast EPSPs (ionotropic)
  • Slow EPSPs (metabotropic)
  • Fast IPSPs (ionotropic)
  • Slow IPSPs (metabotropic)
    These are generally small (~1 mV)
74
Q

What does the range of post synaptic potentials enable

A
  • Enables complex synaptic integration
75
Q

name the 3 anatomical arrangements of CNS synapses

A

Axo-dendritic
Axo-somatic
Axo-axonal

76
Q

synaptic connectivity: describe the difference between divergence and convergence

A

divergence: from one to many
convergence: many to one

77
Q

feedback inhibition: what activates the inhibitory interneuron

A

When action potential fired,
collateral (branch) activates an inhibitory interneuron

78
Q

feedback inhibition: what are the effects of the activation of inhibitory interneuron

A

Inhibitory neurotransmitter
released
* Blue neuron hyperpolarises
Prevents repeated firing

79
Q

describe the different pathways between monosynaptic reflexes & polysynaptic reflexes

A

Monosynaptic reflexes involve:
* Sensory (afferent) neurons
* Motor (efferent) neurons

Polysynaptic reflexes
involve:
* Sensory (afferent) neurons
* Interneurons
* Motor (efferent) neurons

80
Q

synaptic plasticity: what is it dependent on

A

Can be activity-dependent

80
Q

synaptic plasticity definition

A

changes in strength of synapses

81
Q

name a few examples of synaptic plasticity

A

Long-term potentiation
Long-term depression

82
Q

name the steps of a muscle spindle reflex

A
  1. extrafusal muscle fibres at resting length
  2. sensory neurons is tonically active
  3. spinal cord integrates function
  4. alpha motor neurons to extrafusal fibres receive tonic input from muscle spindles
  5. extrafusal fibres maintain a certain level of tension even at rest
83
Q

what does the addition of a load to do the muscle spindle reflex

A

muscle spindle stretch as arm falls and contraction is initiated by muscle spindle restores arm position

84
Q

how does the stretch reflex acts as a negative feedback system

A

the stretch reflex acts as a negative feedback system by detecting stretch of the muscle and making it contract accordingly

85
Q

what is the problem with muscle spindle reflex if the muscle is already partly contracted and how is this solved?

A

There is no tension on the
muscle spindle and it cannot
respond to stretch, solved with α-γ coactivation

86
Q

muscle spindle reflex; describe the orientation of extrafusal fibres compared to intrafusal fibres
how much of muscle do they form? innervated by? where to they lie in comparison to sensory muscle spindle ?

A

Extrafusal fibres
* Form the main bulk of the muscle
* Are innervated by α motor neurons
* Lie in parallel with the sensory muscle spindle
* Intrafusal fibres
* Form a very minor part of the muscle
* Are innervated by γ motor neurons
* Lie in series with the sensory muscle spindle

87
Q

Muscle spindle (stretch) reflex: what does the α-γ co-activation of extrafusal and intrafusal fibres allow for

A

α-γ co-activation of extrafusal and intrafusal fibres allows muscle spindle to respond to stretch whatever the length of the muscle

enables the muscle spindle to act as a stretch receptor, even if the muscle is part contracted

88
Q

what is the function of muscle spindle reflex

A

A mechanism to keep muscle at a constant length,
Stretch of the muscle is detected by muscle spindle receptors

89
Q

what is the function for Golgi tendon organ reflex

A

A mechanism to ensure that excessive tension does not damage the muscle

90
Q

name the processes of the golgi tendon organ reflex

A
  1. neuron from golgi tendon organ fires
  2. motor neuron is inhibited
  3. muscle relaxes
  4. load is dropped
91
Q

which reflex is muscle spindle/ Golgi tendon monosynaptic/polysynaptic reflex and provide an example for each

A

muscle spindle: monosynaptic reflex
patellar tendon (knee-jerk) reflex
Golgi tendon: A polysynaptic reflex
the clasp-knife reflex

92
Q

what activates the golgi tendon organ reflex

A

excessive tensions

93
Q

describe the process during golgi tendon organ reflex

A
  • Afferent fibres activate inhibitory interneurons in the spinal cord
  • Inhibits motor neurons supplying the muscle
  • Muscle relaxes to prevent damage
94
Q

what is a flexion reflex

A

a mechanism to remove a limb from a damaging/potentially damaging stimulus, and not fall over

95
Q

describe how the Flexion (withdrawal) reflex occurs

A

interneurons that activate motor neurons supplying ipsilateral flexors, and inhibit motor neurons supplying ipsilateral extensors = Flexion (withdrawal) reflex

95
Q

how is the flexion reflex detected

A

by nociceptors

96
Q

describe how the crossed extensor reflex occurs

A

activates interneurons that inhibit motor neurons supplying
contralateral flexors, and activate motor neurons supplying contralateral
extensors

97
Q

what can over-ride the reflexes

A

Motor neurons are also under the influence of descending controls that can over-ride the reflex

physiology (10 decks)

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