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A & P Unit 3 > Chapter 11 Nervous System > Flashcards

Chapter 11 Nervous System Flashcards

1
Q

3 main functions of the nervous system

A

sensory input, integration and motor output

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2
Q

Sensory input

A

monitoring stimuli/changes inside and outside the body

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3
Q

Integration

A

interpretation of sensory input

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4
Q

Motor output

A

response to stimuli

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5
Q

Organization of the nervous system

A

Central Nervous System (CNS) and Peripheral Nervous System (PNS)

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6
Q

What makes up the CNS?

A

*Brain and spinal cord

*integration and command center

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7
Q

What makes up the PNS?

A

*Paired spinal and cranial nerves

*spinal nerves: impulses to/from the spinal cord

*cranial nerves: impulses to/from the brain

**carries messages to and from the spinal cord and brain

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8
Q

2 functional divisions of the PNS

A

*sensory (afferent) division

*motor (efferent) division

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9
Q

Sensory afferent fibers-

A

carry impulses from skin, skeletal muscles, and joints to the brain (CNS)

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10
Q

Visceral afferent fibers-

A

transmit impulses from visceral organs to the brain (CNS)

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11
Q

Motor (efferent) division-

A

transmits impulses f_rom CNS to effector organs, muscles and glands_

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12
Q

Two main parts of the motor division are

A

Somatic Nervous System-Voluntary

Autonomic Nervous System (ANS)-Involuntary

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13
Q

Somatic Nervous System is

A

voluntary

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14
Q

Autonomic Nervous System is

A

involuntary

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15
Q

What does ANS (autonomic Nervous System) regulate?

A

smooth muscle and cardiac muscle

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16
Q

What are the divisions of ANS?

A

sympathetic and parasympathetic -one stimulates and the other will inhibit

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17
Q

2 principle cell types of the nervous system

A

Neurons and supporting cells

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18
Q

Neurons are

A

excitable cells that transmit electrical signals

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19
Q

Supporting cells are

A

cells that surround and wrap neurons

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20
Q

Other names for supporting cells: neuroglia or glial cells

A

provide a supportive scaffolding for neurons

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21
Q

Other names for supporting cells: astrocytes

A

*most abundant, versatile and highly branched glial cells *barrier between neurons and capillaries

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22
Q

Other names for supporting cells: microglia

A

small ovoid cells with spiny processes

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23
Q

Other names for supporting cells: ependymal cells

A

range in shape from squamous to columnar *line cavities of CNS (brain &spinal cord)

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24
Q

Other names for supporting cells: oligodendrocytes

A

*branched cells that wrap CNS nerve fibers *form myelin sheaths

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25
Q

Other names for supporting cells: Schwann cells

A

*surround fibers of PNS *form myelin sheaths

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26
Q

Other names for supporting cells: satellite cells

A

surround neuron cell bodies with ganglia, in the PNS

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27
Q

What type of division occurs in neurons?

A

long, lived, amitotic (a simple division of the nucleus with replication of chromosomes)

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28
Q

The function of a neurons plasma membrane is

A

electrical signaling

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29
Q

other names for a nerve cell body

A

Perikaryon or Soma

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30
Q

The structure of a nerve cell body

A

*contains the nucleus and a nucleolus *has no centrioles *has well developed Nissl bodies (rough ER) *contains an axon hillock

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31
Q

what are the processes?

A

axons and dendrites

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32
Q

Dendrites

A

*short branched processes *receptive *create enormous surface area for receptions of signal from other neurons *conduct impulse toward cell body

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33
Q

Axons-structure

A

*slender processes arising from the hillock *may be short or very long *long axons are called nerve fibers *usually there is only one *rare branches, if present, are called axon collaterals *larger diameter causes faster conduction

34
Q

Axons-Function

A

*generates and transmits action potential

*carries impulses away from cell body

*secrete neurotransmitters from the axon terminals

*movement:

–anterograde: toward axonal terminal

–retrograde: away from axonal terminal

35
Q

Function of myelin sheaths

A

*protect the axon

*electrically insulate fibers from one another

*increase the speed of nerve impulse transmission

36
Q

Nodes of Ranvier are

A

gaps in myelin sheath between adjacent Schwann cells

37
Q

Bothe myelinated and unmyelinated fibers are

A

present in CNS

38
Q

Myelin sheaths are formed bu

A

oligodendrocytes in the CNS

39
Q

White mater is

A

dense collections of myelinated fibers

40
Q

White matter is in

A

regions of the brain and spinal cord that have myelinated fibers

41
Q

Gray matter is

A

mostly soma and unmyelinated fibers

42
Q

Gray matter is mostly in

A

nerve cell body-unmyelinated

43
Q

Structural classifications of neurons

A

*multipolar-three or more process (most common)

*Bipolar-two processes (axon & dendrite)-rare

*Unipolar-single, short process in PNS ganglia

44
Q

Functional classifications of neurons

A

*Sensory (afferent)-transmit impulses toward the CNS

*Motor (efferent)-carry impulses away from the CNS

*Interneurons (association neurons)-shuttle signals through CNS pathways-99% of neurons in the body

45
Q

Action potentials, or nerve impulses are

A

*Electrical impulses carried along the length of axons

*Always the same regardless of stimulus

*the underlying functional feature of the nervous system

46
Q

There is potential on either side of membranes when:

A

1) the number of ions is different across the membrane
2) the membrane provides a resistance to ion flow

47
Q

Chemically gated channels open with binding of a

A

specific neurotransmitter

48
Q

Voltage-gated channels open and close in

A

response to membrane potential

49
Q

what is the resting membrane potential?

A

*the potential difference across the membrane of a resting neuron

*the polarity is more negative on the inside

50
Q

What generates the resting membrane potential?

A

It is generated by different concentrations of Na+, K+, Cl-, and protein (A-)

51
Q

Ion concentrations

A

*differential permeability of the neurilemma to Na+ and K+

*Operation of the sodium-potassium pump

52
Q

Changes in membrane potential are caused by

A

Depolarization, repolarization and hyperpolarization

53
Q

Depolarization

A

the inside of the membrane becomes less negative

54
Q

Repolarization

A

the membrane returns to its resting membrane potential

55
Q

Hyperpolarization

A

the inside of the membrane becomes more negative than the resting potential

56
Q

graded potentials are:

A
  • short-lived
  • decrease in intensity with distance
  • magnitude varies directly with the strength of the stimulus
  • sufficiently strong graded potentials can initiate action potentials
57
Q

Action potentials

A
  • a brief reversal of membrane potential
  • only generated by muscle cells & neurons
  • do not decrease in strength over distance
  • an action potential in the axon of a neuron is a nerve impulse
  • they are all or none
58
Q

Describe the resting state of an action potential

A
  • Na+ and K+ channels are closed
  • leakage accounts for small movements of Na+ and K+
  • Each Na+ channel has two voltage-regulated gates
  • activation gates closed in the resting state
  • inactivation gates-open in the resting state
59
Q

Describe the depolarization phase of an action potential

A
  • Na+ permeability increases; membrane potential reverses
  • Na+ (activation) gates are opened; K+ gates are closed
  • Threshold-a critical level of depolarization

(-55 to -50 mV)

60
Q

describe the repolarization phase of an action potential

A
  • sodium inactivation gates close
  • membrane permeability to Na+ declines to resting levels
  • As sodium gates close, voltage-sensitive K+ gates open
  • K+ exits the cell and internal negativity of the resting neuron is restored
61
Q

describe the hyperpolarization phase of an action potential

A
  • potassium gates remain open, causing an excessive efflux of K+
  • this efflux causes hyperpolarization of the membrane (undershoot)
  • the neuron is insensitive to stimulus and depolarization during this time
62
Q

Describe the role of the sodium-potassium pump in relation to an action potentials

A
  • repolarization
    1) restores the resting electrical conditions of the neuron
    2) Does not restore the resting ionic conditions
  • ionic redistribution back to resting conditions is restored by the sodium-potassium pump
63
Q

What are the phases of the action potential?

A

1-resting state

2-depolarization phase

3-repolarization phase

4-hyperpolarization

64
Q

What is threshold? Describe all or none phenomenon.

A
  • threshold-membrane is depolarized by 15-20 mV
  • established by the total amount of current flowing through the membrane
  • weak (subthreshold) stimuli are not relayed into action potentials
  • strong (threshold) stimuli are relayed into action potentials
  • All-or-nothing phenomenon-action potentials either happen completely or not at all
65
Q

Describe the absolute refractory period

A

Time from the opening of the Na+ activation gates until the closing of the inactivation gates

the absolute refractory period:

  • prevents the neuron from generating an action potential (can’t respond to another stimulus)
  • ensures that each action potential is separate
  • enforces one-way transmission of nerve impulses
66
Q

Describe the relative refractory period

A

The interval following the absolute refractory period when:

*sodium gates are closed

*potassium gates are open

*repolarization is occurring

  • the threshold level is elevated, allowing strong stimuli to increase the frequency of action potential events
  • during the ‘after-hyperpolarization’ stage-another stimulus could open the Na gates, but only a strong stimulus (Shari)
67
Q

Rate of impulse propagation is determined by:

A

axon diameter-the larger the diameter, the faster the impulse

presence of a myelin sheath-myelination dramatically increases impulse speed

68
Q

Describe Saltatory Conduction

A

*current passes through a myelinated axon only at the nodes of Ranvier

*action potentials are triggered only at the nodes and jump from one node to the next

69
Q

Explain multiple sclerosis

A

*it’s an autoimmune disease that mainly affects young adults

-the immune system attacks myelin proteins

-axons are not damaged

*symptoms: visual disturbances, weakness, loss of muscular control and urinary incontinence

*nerve fibers are severed and myelin sheaths in the CNS become nonfunctional sclerosis (when sheaths are reduced to hard lesions)

70
Q

presynaptic neuron

A

conducts impulses toward the synapse

71
Q

Postsynaptic neuron

A

transmits impulses away from the synapse

72
Q

Describe two types of postsynaptic potentials

A

*EPSP-excitatory postsynaptic potentials

*IPSP-inhibitory postsynaptic potentials

73
Q

what is temporal summation

A

presynaptic neurons transmit impulses in rapid-fire order

74
Q

what is spatial summation

A

a postsynaptic neuron is stimulated by a large number of terminals at the same time

75
Q

Neurotransmitters

A

*chemical used for neuronal communication with the body and the brain

*50 different neurotransmitters have been identified

*classified chemically and functionally

76
Q

Neurotransmitters and diseases

A

*GABA-Gamma(y)-aminobutyric acid

-the most prevalent neurotransmitter in the brain

-inhibitory

-Huntington’s-lack of GABA releasing neurons

*Acetylcholine-refer to next card

*Norepinephrine-feel good, reuptake blocked by cocaine

*Dopamine-feel good, regulation of skeletal movement

-Parkinson’s-substantia nigra degenerates-decreased dopamine

*serotonin-inhibitory, regulates mood, Prozac block reuptake

*endorphins-inhibit pain, morphine, heroin mimic

77
Q

Neurotransmitters : Acetylcholine

A

*first neurotransmitter identified, and best understood

*released at the neuromuscular junction

*synthesized and enclosed in synaptic vesicles

*degraded by the enzyme acetylcholinesterase (AChE)

*released by:

-all neurons that stimulate skeletal muscle

-some neurons in the autonomic nervous system

78
Q

Two classifications of Neurotransmitters

A

excitatory and inhibitory

*excitatory neurotransmitters cause depolarizations (e.g., glutamate)

*_Inhibitory neurotransmitters cause hyper_polarizations (e.g., GABA and glycine)

79
Q

Can neurotransmitters have both effects? Give an example.

A

*some neurotransmitters have both excitatory and inhibitory effects

*determined by the receptor type of the postsynaptic neuron

*example: acetylcholine

  • Excitatory at neuromuscular junctions with skeletal muscle
  • inhibitory in cardiac muscle
80
Q
A

A & P Unit 3 (3 decks)

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