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A and P semester 2 > Chapter 11: nervous system > Flashcards

Chapter 11: nervous system Flashcards

1
Q

What are the 3 functions of the nervous system?

A

1) SENSORY INPUT: collection of stimuli
2) INTEGRATION: interpretation of the sensory information and decide response
3) MOTOR OUTPUT: activation of effector organs (muscles and glands) to produce a response

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2
Q

What type of neuron fulfills each of the three functions of the nervous system?

A

Sensory neurons receive stimuli

Interneurons (association neurons) interpret and decide

Motor neurons produce response

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3
Q

What are the 2 main divisions of the nervous system?

A

CNS = brain and spinal cord (integration and command)

PNS = paired spinal and cranial nerves that carry messages to and from the CNS

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4
Q

What are the 2 functional divisions of the PNS?

A

SENSORY (afferent) division

MOTOR (efferent) division

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5
Q

What are the 2 subdivisions under the sensory (afferent) division of the PNS?

A

somatic afferent fibers carry info away from skin, skeletal muscles, and joints

visceral afferent fibers carry info from visceral organs

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6
Q

What are the 2 subdivisions under the motor (efferent) division of the PNS?

A

Somatic (voluntary) nervous system:
- conscious control of skeletal muscles

Autonomic (involuntary) nervous system (ANS)

  • unconscious control
  • regulates smooth muscle, cardiac muscle, and glands
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7
Q

What are the two subdivisions of the ANS (autonomic (involuntary) nervous system)?

A

Sympathetic

Parasympathetic

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8
Q

What are the two major cell types of the nervous tissue?

A

NEURONS: excitable cells that carry info by transmitting electrical signals

NEUROGLIAL (accessory) cells that assist neurons

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9
Q

What are the 4 kinds of neuroglial cells in the CNS?

A

ASTROCYTES

MICROGLIA

EPENDYMAL cells

OLIGODENDROCYTES

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10
Q

What are astrocytes and what is there function?

A

They are the most abundant cell, they are star shaped and highly branched

  • SUPPORT and ANCHOR the neurons to capillaries
  • TRANSFER glucose from blood to neurons
  • GUIDE GROWTH of young neurons - aid in synapse formation
  • control ION CONTENT around neurons (remove excess K+)
  • signal each other and influence neuron signals
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11
Q

What do microglia look like and what do they do?

A

Small ovoid cells with thorny processes

  • MONITOR condition of neurons
  • MIGRATE toward injured neurons
  • convert to MACROPHAGES to phagocytize microorganisms and debris
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12
Q

What do ependymal cells look like and what do they do?

A

range in shape from squamous to columnar

  • line the central cavities of the brain and spinal column
  • cilia move the CSF (cerebrospinal fluid)
  • form the BLOOD-BRAIN BARRIER
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13
Q

What do oligodendrocytes look like and what do they do?

A

large branched cells

  • Processes wrap around several nerve fibers, FORMING insulating MYELIN SHEATHS
  • Gaps between are called NODES OF RANVIER
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14
Q

What are the 2 types of neuroglial cells in the PNS?

A

SATELLITE CELLS

SCHWANN CELLS

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15
Q

What do satellite cells do?

A
  • surround neuron cell bodies in the PNS
  • same role as astrocytes in CNS
  • support, nurture, control environment around cell bodies
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16
Q

What do schwann cells do?

A

smaller than oligodendrocytes

  • surround peripheral nerve fibers and form myelin sheaths
  • gaps between cells called nodes of ranvier
  • vital to regeneration of peripheral nerve fibers
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17
Q

What are the 5 special characteristics for neurons?

A

1) long lived (100 yrs plus)
2) amitotic (don’t divide, with a few exceptions)
3) high metabolic rate (depends on continuous supply of oxygen and glucose b/c it can’t store its own)
4) irritable - respond to stimuli
5) plasma membrane functions in electrical signaling

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18
Q

What are the two other names for the cell body of a neuron?

A

perikaryon or soma

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19
Q

What organelles do neurons lack?

A

centrioles (do not divide)

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20
Q

What is the rough ER of a neuron called? what is significant about this feature?

A

Nissl bodies:

  • they are specialized while developed rough ER and are there because the neurons need to produce large numbers of proteins/neurotransmitters.
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21
Q

What is a cluster of cell bodies in the CNS called?

A

Nucleus

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22
Q

What is a cluster of cell bodies in the PNS called?

A

Ganglion

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23
Q

What are the two types of neural appendages?

A

dendrites - receive input

axon - the cells output

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24
Q

How many axons are there per neuron?

A

1

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25
Q

Where are stimuli integrated?

A

at the axon hump.

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26
Q

What is longer, an axon or a dendrite?

A

axons

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27
Q

What happens to an axon if it is cut? why?

A

it degenerates quickly because it has no ER or Golgi bodies and depends on transport of proteins from the neuron’s body

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28
Q

What makes up the myelin sheath?

A

proteins and lipids (think of cell membranes that are wrapped around the axon)

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29
Q

What are the functions of the myelin sheath?

A
  • PROTECT and electrically INSULATE axon

- increase SPEED of nerve impulse

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30
Q

How are axons myelinated in the PNS?

A

many schwann cells wrap many times around the axon

  • myelin sheath is made of concentric layers of Schwann cell membrane
  • NEURILEMMA: peripheral bulge of Schwann cell cytoplasm (outer layer)
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31
Q

What is the neurilemma?

A

the peripheral bulge of schwann cell cytoplasm; the outer layer.

(because schwann cell, only in the PNS not CNS)

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32
Q

How is nerve tissue myelinated in the CNS?

A

formed by oligodendrocytes

  • much larger than schwann cells
  • each cell may myelinate multiple axons
  • formed by the processes of oligodendrocytes, not the whole cell

contains nodes of ranvier, but no neurilemma

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33
Q

What makes up grey matter?

A

non-myelinated fibers

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34
Q

What makes up white matter?

A

myelinated fibers

35
Q

What are the three structural classifications of neurons?

A

MULTIPOLAR: 3 + processes

  • most common
  • ex somatic neurons

BIPOLAR: 2 processes

  • very rare
  • ex specialized receptors in sensory organs

UNIPOLAR: 1 short process which branches into 2
(structure like 0-I) where O is the body.
- peripheral process often associated with a sensory receptor
- central process - branch entering CNS
ex most sensory neurons

36
Q

What are the three functional classifications of neurons?

A

SENSORY (afferent): carry info from receptors to CNS
- most are unipolar. cell bodies in ganglia outside cns

MOTOR (efferent): carry info from cns to effectors
- multipolar, cell bodies insided cns

INTERNEURONS (association): connect sensory and motor neurons

  • receive and integrate info and decide response
  • mostly multipolar
  • inside cns
37
Q

What percentage of neurons are interneurons?

A

99%

38
Q

Define voltage.

A

the measure of potential energy generated by separated charges

39
Q

What is potential difference?

A

voltage measured between two points

40
Q

What are the two main types of ion channels?

A

1) PASSIVE channels - always open, also called leakage

2) GATED channels - open in response to stimulus

41
Q

What are the two types of gated ion channels?

A

CHEMICALLY gated - open with binding of a specific neurotransmitter

VOLTAGE gated - open and close in response to changes in membrane potential

42
Q

What is a graded potential?

A

a potential change that occurs when a stimulus causes gated ion channels to open

43
Q

What are the characteristics of a graded potential?

A
  • amplitude varies directly with stimulus str
  • they are short-lived, localized changes in membrane potential
  • dec in magnitude with distance
44
Q

What are the characteristics of an action potential?

A

is large with amplitude of approx 100 mV

  • moves along whole axon of neuron
  • does not dec in magnitude with distance
  • is all or nothing
  • produced from the sum of many graded potentials
  • used for long-distance signalling
45
Q

What is the value of the resting potential?

A

-70 mV

46
Q

How is the resting potential maintained?

A

by the Na/K pump which keeps NA low and K high inside, and the opposite outside

47
Q

What is the value of threshold potential?

A

-50 to -55 mV

48
Q

What happens if threshold is reached by graded potentials?

A

an action potential is generated

49
Q

How do action potentials code for strength of a stimulus?

A

with frequency, NOT amplitude

it is always the same

50
Q

What are the two types of graded potentials?

A

Excitatory graded potentials (EP)
- rise in potential toward threshold (depolarizes)

Inhibitory graded potentials (IP)
- movement away from potential (hyperpolarizationg)

51
Q

What determines how a neuron responds to stimuli?

A

the sum of all the graded potential inputs

  • if the graded potentials add up to reach threshold
52
Q

To what voltage does the membrane depolarize to during an AP?

A

+ 30 mV

53
Q

What causes the absolute refractory period? What does this ensure that each action potential will be?

A

Na gates are still open so no new AP can be generated

  • ensures each AP is a separate event and keeps transaction unidirectional.
54
Q

Describe what the relative refractory is and what causes it.

A

relative refractory period is when the period during hyperpolarization when the Na channels are closed, but the membrane potential is more neg b/c the Na/K pumps haven’t restored normal resting conditions.

Therefore it can be stimulated to generate a new AP, but requires a stronger stimulus

55
Q

what are the two types of conduction of an AP?

A

CONTINUOUS conduction in unmyelinated

SALTATORY conduction in myelinated axons

  • signal jumps from node to node
  • approx 30x faster
56
Q

What 4 factors contribute to the speed of transmission of impulses?

A

1) axon diameter - larger = less resistance
2) Myelinated or not
3) presence of chems - (ex from drugs, usually slows transmission)
4) physical conditions around axon - ex low temp

57
Q

What are the two types of synapses?

A

ELECTRICAL SYNAPSE: rare in adult, common in embryo

  • like a gap junction, very fast.
  • used to synchronize actions of neurons in a single area (ex controlling eye muscles)

CHEMICAL SYNAPSE: most common
- neurotransmitter carries message across synaptic cleft

58
Q

How is transmission kept unidirectional in chemical synapses?

A

Only the presynaptic neuron contains neurotransmitter vesicles and only postsynaptic neuron has the appropriate receptors

59
Q

Describe what an EPSP is.

A

Excitatory post synaptic potentials (a type of graded)

  • binding of neurotransmitter causes Na and K channels to open, more Na moves in then K moves out (depolarizes slightly)
  • travel to the axon hillock where they are integgrated
60
Q

Describe what an IPSP is.

A

Inhibitory post synaptic potential
- binding of neurotransmitter changes permeability so K moves out or Cl moves in -> hyperpolarization and less likely to generate an AP

61
Q

What two factors contribute to the strength of the post synaptic potential?

A

amount of neurotransmitter released

time the neurotransmitter is in area

62
Q

What are the two types of summation of graded potentials?

A

TEMPORAL summation: over time
- mult. EPSPs over a short time interval at same point on membrane

SPATIAL summation: over space

  • mult EPSPs occurring at different places on membrane at same time
  • the closer to hillock, the greater the effect
63
Q

What is synaptic potentiation?

A

the more often a synapse is used, the stronger its effect on the post synaptic neuron becomes

the ability of a neuron to learn

  • presynaptic neuron contains more Ca -> more NT released -> more effect
64
Q

What is multiple sclerosis?

A

an autoimmune disease that mainly affects young adults

  • immune system attacks the myelin sheaths of the CNS
  • results in shunting and short-circuiting of impulses
  • conduction slows and eventually ceases
65
Q

What are 6 common neurotransmitters?

A 
Acetylcholine
Biogenic amines
Amino acids
Peptides
Gasotransmitters
Purines
66
Q

where is ACH found?

A

in all neuromuscular junctions, in CNS, and some autonomic synapses

67
Q

What are biogenic amines synthesized from?

A

from amino acids

from tyrosine -> dopamine -> norepinephrine -> epinephrine

from tryptophan -> serotonin

from histidine -> histamine

68
Q

Where are biogenic amines commonly found?

A

in CNS and autonomic

- play a role in emotions

69
Q

Where are amino acid NT found? give some examples.

A

only in CNS

ex GABA, glutamate, glycine, aspartate

70
Q

give some examples of peptide NT

A

substance P - causes pain
endorphins - pleasure chems, reduce pain
gut brain peptides - somatostatin, CCK

71
Q

give a few examples of gasotransmitters

A

NO - involved in learning and memory, excess release causes brain damage in stroke patients

CO - regulates cGMP in brain

H2S - not much known

72
Q

Give a few examples of purine NT

A

ATP

Adenosine

73
Q

What are the three functional classifications of neurons?

A

EXCITATORY (depolarizing) ex glutamate

INHIBITORY (hyperpolarizing) ex GABA

NEURMODULATOR

74
Q

What does the neuromodulator class of neurotransmitter do?

A

it is a NT that is released by a neuron that doesn’t directly cause EPSPs or IPSPs, but affects the strength of synaptic transmission

ex. controlling synthesis, release or reuptake, changing of sensitivity of post synaptic membrane to NT

75
Q

What are the two mechanisms of action neurotransmitters can have?

A

DIRECT - binds to receptor which then opens channels to change permeability

INDIRECT - binds to G receptor which activates cAMP to exert its effects

76
Q

What is a neuronal pool?

A

a functional grouping of neurons that integrate information from receptors or other neuronal pools

  • forward process information to the next level of the nervous system
77
Q

What are the 4 types of neural circuits?

A

DIVERGING

CONVERGING

REVERBERATING

PARALLEL after discharge

78
Q

What is a diverging circuit?

A

it is an amplifying circuit

one fiber stimulates many others

  • common for motor and sensory circuits
  • ex one motor neuron in the brain stimulates hundreds to the skeletal muscles
79
Q

What is a converging circuit?

A

the opposite of diverging

  • many different impulses funneled into a single receiving area
  • produces strong inhibition/stimulation
  • common in motor and sensory systems
80
Q

What is a reverberating circuit?

A

it is an oscillating circuit

-> 0 -> 0 -> 0
I I
0<- 0

used in control of rhythmic activities
- sleep/wake cycles, breathing

81
Q

What is a parallel after discharge circuit?

A
  • one incoming fibers stimulates many parallel neurons which then stimulate a single output cell.
  • signals arrive at different times at the output cell
  • involved in complex mental activities
82
Q

What are the two patterns of processing?

A

SERIAL processing

PARALLEL processing

83
Q

What is serial processing?

A

input travels along a single pathway to specific destination

- much faster, but takes longer to get a complete picture

84
Q

What is parallel processing?

A

input travels along several different pathways to integration points in CNS

  • allows for the brain to process many different aspects at same time
  • much faster at determining connections than with serial
  • important for higher mental functioning

A and P semester 2 (10 decks)

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