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physio > intro to nervous system > Flashcards

intro to nervous system Flashcards

1
Q

What is a nerve?

A

bundle of axons (nerve fibers) wrappe din connective tissue

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2
Q

What is a ganglion?

A

swelling or bulbous region of a nerve where the cell bodies of neurons are concentrated

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3
Q

What are the functions of the spinal cord?

A
  • walking movements
  • reflexes
  • postural support
  • reflex control of bv, gi movements and urinary excretion
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4
Q

What are the functions of the subcortical (CNS)?

A
  • arterial pressure
  • equilibrium
  • feeding reflexes
  • emotional responses
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5
Q

What are the functions of the cortical (CNS)?

A

-association and integration of information from lower nervous system levels

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6
Q

What are the information pathways for the somatosensory system?

A

spinal cord, reticular formation, cerebellum, thalamus, cerebral cortex

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7
Q

Is the motor functional division of the PNS efferent or afferent?

A

Efferent (CNS to effectors)

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8
Q

What are the properties of neurons?

A
  • excitability (irritability)
  • conductivity
  • secretion
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9
Q

What is the ability to respond to changes in the body and external environment?

A

stimuli

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10
Q

What is the difference between somatic sensory and visceral sensory?

A

somatic carries signals from receptors in the skin, muscles, bones and joints while viscerl carries signals from internal organs

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11
Q

What are interneurons?

A

association neurons
lie between sensory and motor pathways in CNS
90% of our neurons
-process, store, retrieve information performing an integrative function

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12
Q

What are the two divisions of the autonomic nervous system?

A

sympathetic and parasympathetic

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13
Q

What do visceral motor neurons do in the ANS?

A

carry signals to glands, cardiac muscle, and smooth muscle of organs and blood vessels

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14
Q

What do somatic motor neurons do?

A

carry signals to the skeletal muscle (voluntary and reflexes)

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15
Q

Afferent neurons carry…

A

signals ot the CNS

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16
Q

Efferent neurons carry…

A

signals from the CNS to effectors

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17
Q

What are other anmes for the cells body of a neuron?

A

perikaryan or soma

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18
Q

What is the primary site for receiving signals form other neurons?

A

dendrites

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19
Q

What is lipofuscin?

A

material that cannot be digested by lysosomes

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20
Q

What are neurofibrillary tangles?

A

prominent feature of degeneration neurons in Alzheimer’s, ALS, and down syndrome

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21
Q

What is the axon cytoplasm and its membrane called?

A

axoplasm

axolemma

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22
Q

Each branch of an axon ends in a synaptic knob. What is this?

A

little swelling that forms a junction (synapse) with the next cell

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23
Q

What is important in maintianing axonal diameter?

A

neurofilaments

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24
Q

What are microtubules important for in axons?

A

important as tracks for fast anterograde and retrograde axonal transport

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25
Q

What is the myelin in the CNS called? In the PNS?

A 
CNS= oligodendrocytes
PNS= Schwann cells
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26
Q

In PNS, as many as a hunndred layers wrap around an axon. What are the layers?

A

outermost coil is Schwann cell

covered by basal lamina and endoneurium

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27
Q

Where do signals begin?

A

intial segments and axon hillock form trigger zone

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28
Q

When does myelination occur?

A

begins during fetal development but proceeds most rapidly in infancy

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29
Q

MS is a chronic demyelinationg disease of the CNS. What is ti often characterized by?

A

remission and relapse

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30
Q

Patients with MS have CNA plaques (scar) formed by ____ in the white matter.

A

astrocytes

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31
Q

What are the most common symptoms of MS?

A

unilateral visual impairment, diplopia (double vision), paresthesias (pins and needles), ataxia, vertigo, fatigue, muscle weakness, dysarthria, mental disturbances

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32
Q

What is Tay-Sachs disease?

A

hereditary disorder of infants of eastern european jewish ancestry
-abnormal accumulation of glycolipid called GM2 in the myelin sheath

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33
Q

What effect would a person homozygous for Tay-Sachs allele be missing?

A

the lysosomal enzyme that would usually decompose the glycolipid GM2

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34
Q

In Tay-Sachs, accumulation of ganglioside GM2 disrupts cnoduction of nerve signals. What are the symptoms of this disease and to what age do they live?

A
  • blindness, loss of coordination and dementia

- fatal before age 4

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35
Q

What are the three neuronal types?

A

unipolar, bipolar, multipolar

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36
Q

The multipolar neuron is the most common. What are the characteristics?

A

many dendrites, one axon

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37
Q

The unipolar neuron is sensory from what?

A

skin and organs to spinal cord

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38
Q

What is the anaxonic neuron?

A

many dendrites, no axon

-help in visual processes in retina

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39
Q

What is an electrical synapse?

A

gap junction allowing ion movement between neurons– this is common in smooth and cardiac muscle

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40
Q

When are electrical synapses found in the CNS?

A

when groups of interconnected neurons need to be fired synchronously

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41
Q

How do ionotropic post-synaptic neurons work?

A

on a short time scale

Na+, K+, Ca2+, Cl-

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42
Q

How do metabotropic post synaptic neuron work?

A

workj through second messanger systems

functions on a long term scale (seconds to possibly months or years)

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43
Q

What are the 4 possible metatropic receptors?

A
  • ion channel opening
  • cAMP or cGMP activation
  • intracellular enzyme activation (MAPK, PKC)
  • direct changes in gene transcription
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44
Q

What are the characteristics of small molecule chemical neurotransmitters?

A

short lasting effect
1000’s per vesicle
produced in synaptic terminal
ex: ACh, glycine, nitrous oxide

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45
Q

What are the characterisitics of the neuropeptide chemical neurotransmitters?

A

long lasting effect
100’s per vesicle
produced in soma within Golgi
ex: prolactin, carnosine, enkephalins, substance P, gastrin

46
Q

What are the differences in speed of nerve signal depending on size and myelination?

A

small, unmyelintaed- 0.5-2 m/sec
small, myelinated- 3-15.0 m/sec
large, myelinated- up to 120 m/sec

47
Q

What do slow signals supply?

A

stomach and dilate pupil

48
Q

What do fast signals supply?

A

skeletal muscle and transport sensory signals for vision and balance

49
Q

What effects excitatory neurotransmission?

A
  • sodium channel opening
  • decrease in Cl- or K+ channels
  • change in # of channels via changes in gene expression
50
Q

What effects inhibitory neurotransmission?

A
  • Cl- channel opening
  • increased K+ conductance
  • inhibition of excitatory channels
  • decreased # of excitation channels
51
Q

Describe neuronal excitation.

A

excitatory neurotransmitter–> increased sodium permeability results in EPSP (excitatory post-synaptic potential)

  • need 40-80 vesicles to cause action potential
  • summation of EPSPs can cause depolarization sufficient to initiate action potential
52
Q

Describe neuronal inhibition.

A

inhibitory neurotransmitters are release form presynaptic neuron–> opening of Cl- and/or K+ channels

  • increased Cl- or K+ permeability results in hyperpolarization of the cell
  • IPSP (inhibitory post-synaptic potential)
53
Q

NO action potentials in dendrites, ONLY ____ ____.

A

electrotonic conduction

54
Q

Describe dendrites channels.

A

low numbers of sodium channels, high numbers of K+ and Cl- leaky channels (decremental conduction)

55
Q

What does resting membrane potential (RMP) result from?

A
  • ions diffuse down their concentration gradient through the membrane
  • plasma membrane is selectively permeable and allows some ions to pass easier than others
  • electrical attraction of cations and anions to each other
56
Q

What provides the greatest contribution to the resting membrane potential?

A

leaking of potassium ions

57
Q

During RMP, what is the membrane much less permeable to?

A

high concentration of sodium found outside the cell

58
Q

What accounts for 70% of the energy required for the nervous system?

A

Na+/K+ pump

  • pumps out 2 sodium for every 2 potassium it brings in
  • requires a lot of ATP
59
Q

What is an action potential and when does it occur?

A
  • dramatic change produced by voltage-regulated ion gates in the plasma membrane
  • only occur where there is high enough density of voltage-regulated gates
60
Q

Where is the action potantial generated?

A

trigger zone (350-500 gates per micrometer squared)

61
Q

Where can an actional potential NOT be generated?

A

soma (only 50-75 gates per micrometer squared)

62
Q

How does an action potential work?

A
  • a rapid up and down shift in the membrane voltage
  • sodium arrives at the axon hillock
  • depolarize the membrane at that point
  • threshold must be reached, neuron fires and produces an action potential
63
Q

What is a threshold and what is the value to create an action potential?

A

critical voltage to which local potentials must rise to open the voltage-regulated gates
-55 mV

64
Q

What is the spike of an action potential?

A

when more and more sodium channles open in the trigger zone in a positive feedback cycle creating a rapid rise in membrane voltage

65
Q

What are the characteristics of action potential?

A
  • all or none law
  • nondecremental- do not get weaker with distance
  • irreversible- once started goes to completion and cannot be stopped
66
Q

What is the refractory period in an action potential?

A

period of resistance to stimulation

67
Q

What are the two phases of the refractory period?

A
  • absolute refractory- no stimulus od any strength will trigger AP
  • relative refractory period- only especially strong stimulus will trigger new AP
68
Q

What are 4 ways that receptors can be activated?

A
  • mechanical deformation of the receptor
  • chemical
  • change in temp
  • effect of EM radiation
69
Q

What is the labeled-line theory?

A

each sensory receptor is tied to a specific nerve in the central nervous system

70
Q

Pacinian corpuscle activation

A
  • deformation of the nerve fiber induces Na+ channel opening (receptor potential)
  • receptor potential induces local current whihc travels to 1st Node of Ranvier
  • if the local current is high enough it will generate an action potential
71
Q

increase strength of stimulus to the pacinian corpuscle=

A

increase in amplitude of receptor potential which leads to increase in action potential frequency

72
Q

increase in membrane potential will cause an increase in….

A

action potential frequency

73
Q

tonic receptors

A

slow adaptors

keep brain apprised of the status of the body and its relationship to the environment

74
Q

examples of tonic receptors

A

golgi tendon organs, muscle spindles, macula receptors in the vestibular apparatus, pain receptors, chemoreceptors

75
Q

phasic receptors

A

rapid adaptors

allows prediction of the future location of the body

76
Q

examples of phasic receptors

A

pacinian corpuscle- on with pressure–> rapid adaption–> on wiht pressure release

77
Q

temporal summation

A

-increased frequency of nerve impulses correlates with in increased strength of stimulus

78
Q

spatial summation

A
  • A,B,C firing alone cause partial depolarization but not enough for an action potential
  • but if they all fire simultaneously their combined effects will cause an action potential
  • increased stimulation recruits more nerve endings
79
Q

In neuronal pools, presynaptic neurons can synapse on multiple postsynaptic neurons. What are the 2 kinds of stimulation?

A

suprathreshold stimulation

subthreshold stimulation

80
Q

What is the discharge zone?

A

if the presynaptic fiber is excitatory then all postsynaptic neurons will generate action potentials

81
Q

What is the facilitation zone?

A

if the presynaptic fiber is excitatory then postsynaptic neurons will be more likely to generate action potentials

82
Q

What is the inhibitory pool?

A

inhibitory presynaptic fibers will prevent neurons in the center area from generating action potentials

83
Q

each neuron can have how many presynaptic knobs connecting to dendrites and cell body?

A

10,000-200,000

84
Q

How much information is disregarded as irrelevant?

A

99%

85
Q

sensory neurons are usually divergent or convergent and why?

A

usually divergent

allows wide distribution of snesory information

86
Q

motor neurons are usually divergent or convergent and why?

A

usually convergent

many presynaptic inputs are required for the activation of a motor neuron

87
Q

In amplifying divergence, pyrimidal neurons are capapble of activating how many muscle fibers?

A

10,000

88
Q

Dorsal column neurons that transmit information tot he cerebellum and the thalamus are an example of what?

A

multiple source divergence

89
Q

Why does convergence occur?

A

because neurons are almost never excited by 1 synaptic input

90
Q

Parts of spinal cord interneuron convergence

A
  • peripheral neurons entering spinal cord
  • propriospinal fibers from on espinal cord region to another
  • corticospinal fibers from cerebral cortex
  • other pathways including reticulospinal tract fibers
91
Q

special characteristics of synaptic transmission

A

fatigue
metabolic disturbances
synaptic delay

92
Q

What is the mechanism of fatigue in synaptic transmission?

A

protects against excessive activity

  • exhaustion of neurotransmitters
  • inactivation of post-synaptic receptors
  • abnormal ion concentrations in postsynaptic neuron
93
Q

the metabolic disturbances of synaptic transmission

A

alkalosis- increased neuronal excitability, can cause seizure activity
acidosis- decreased neuronal excitability, can lead to coma and death

94
Q

synaptic delay of synaptic transmission is used to…

A

estimate number of neurons in series in a circuit

95
Q

What arteries supply blood to the brain?

A

carotid and vertebral arteries

96
Q

What arteries merge to form the Circle of Willis?

A

carotid and vertebral arteries

supply the brain with blood

97
Q

What are metabolic factors that regulate cerebral blood flow?

A

concentrations of CO2, H+, O2

compounds released by astrocytes that regulate local blood flow (NO, arachidonic acid, K+, adenosine)

98
Q

increase in PCO2 will have what effect on CBF

A

increase in CBF
CO2+H2O⇔𝐻2𝐶𝑂3⇔𝐻𝐶𝑂3−+𝐻+
anything increasing H+ will increase CBF

99
Q

Why does a decrease in O2 cause vasodilation?

A

leads to anaerobic metabolism–> generation of acids

can lead to coma!

100
Q

How much CSF in CNS?

A

~150 mL

101
Q

What produces ~500 mL of CSF each day?

A

choroid plexus

102
Q

What regulates CSF pressure by acting as valves?

A

arachnoid villi

it allows CSF to flow back into venous system

103
Q

Granulation allow:

A

free flow of CSF
dissolved protein molecules
RBCs and WBCs back into venous blood

104
Q

Right side MCA stroke

A

left hemineglect
left upper motor neuron type muscle wekaness (usually face and arm)
left visual field and somatosensory deficits

105
Q

Left side MCA stroke

A

Broca’s aphasia
Wernicke’s aphasia
right upper motor neurons type muscle weakness
right visual field and somatosensory deficits

106
Q

Coup

A

initial impact of the brain( frontal)

107
Q

Contrecoup

A

when the brain recoils form the initial impact (occipital)

108
Q

Communicating hydrocephalus

A

obstruction is in the subarachnoid space

109
Q

non-communicating hydrocephalus

A

obstructione is within the ventricular space

110
Q

Causes of cerebral edema

A

trauma, cancer, ischemic stroke, inflammation, high-altitude cerebral edema

111
Q

treatments of cerebral edema

A

diuretics, corticosteroids, surgical decompression, osmotherapy

physio (14 decks)

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