Chapter 12 Flashcards Preview

A&P I - Dr Lian > Chapter 12 > Flashcards

Flashcards in Chapter 12 Deck (99):
1

Two kind of cells of neural tissue

1. Neurons
2. Neuroglia

2

Cells that send and receive signals

Neurons

3

Cells that support and protect neurons

Neuroglia (glial cells)

4

Functions of neuroglia

• Maintain physical structure of tissues
• Repair tissue framework after injury
• Perform phagocytosis
• Regulate the composition of the interstitial fluid surrounding neurons

5

Anatomical Divisions of the Nervous System

• Central nervous system (CNS)
• Peripheral nervous system (PNS)

6

division of the nervous system that consists of the spinal cord and brain and functions to process and coordinate sensory data, motor commands, and higher functions of brain intelligence, memory, learning, and emotion

Central Nervous System (CNS)

7

Functional Divisions of the PNS

• Afferent division
• Efferent division

8

Division of the PNS that carries sensory information from PNS sensory receptors to CNS

Afferent division

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Division of the PNS that carries motor commands from CNS to PNS muscles and glands

Efferent division

10

These detect changes or respond to stimuli and consists of neurons and specialized cells

Receptors

11

These respond to efferent signals

Effectors

12

Part of the efferent division that controls voluntary and involuntary (reflexes)
muscle skeletal contractions

Somatic nervous system (SNS)

13

Part of the efferent division that controls subconscious actions, contractions of
smooth muscle and cardiac muscle, and
glandular secretions

Autonomic nervous system (ANS)

14

Part of the ANS division that has a stimulating effect

Sympathetic division

15

Part of the ANS division that has a relaxing effect

Parasympathetic division

16

What structures are found in the cytoskeleton of a neuron?

Neurofibrils, neurofilaments and neurotubules

17

bundles of neurofilaments that provide support for dendrites and axon

Neurofibrils

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Dense areas of RER and ribosomes that make neural tissue appear gray (gray matter)

Nissl bodies

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Area where a neuron
communicates with another cell

synapse

20

expanded area of axon of presynaptic neuron that contains synaptic vesicles of neurotransmitters

synaptic terminal

21

chemical messengers that are released at presynaptic membrane that affect receptors of postsynaptic membrane; they are broken down by enzymes and are reassembled at synaptic terminal

Neurotransmitters

22

Neurotubules within the axon that transport raw materials between cell body and synaptic terminal, and are powered by mitochondria, kinesin, and dynein

Axoplasmic transport

23

Type of synapse between neuron and muscle

Neuromuscular junction

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Type of synapse between neuron and gland

Neuroglandular junction

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Type of neuron found in brain and sense organs (small)

Anaxonic neurons

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Type of neuron found in special sensory organs (sight, smell, hearing, one axon and one dentrite)

Bipolar neurons

27

Type of neuron found in sensory neurons of PNS (Fused dendrites and axon)

Unipolar neurons

28

Type of neuron common in the CNS and include all skeletal muscle motor neurons (Multiple dendrites, one axon)

Multipolar neurons

29

Afferent neurons of PNS

Sensory neurons

30

Efferent neurons of PNS

Motor neurons

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Association neurons that are responsible for distribution of sensory information, coordination of motor activity, and are involved in higher functions such as memory, planning, and learning

Interneurons

32

Functions of Sensory Neurons

• Monitor internal environment (visceral sensory neurons)
• Monitor effects of external environment (somatic sensory neurons)

33

Three Types of Sensory Receptors

1. Interoceptors
2. Exteroceptors
3. Proprioceptors

34

Type of sensory receptors that monitor internal systems (digestive, respiratory, cardiovascular, urinary, reproductive) and internal senses (taste, deep pressure, pain)

Interoceptors

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Type of sensory receptors that monitor external senses (touch, temperature, pressure) and distance senses (sight, smell, hearing)

Exteroceptors

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Type of sensory receptors that monitor position and movement (skeletal muscles and joints)

Proprioceptors

37

Four Types of Neuroglia

1. Ependymal cells
2. Astrocytes
3. Oligodendrocytes
4. Microglia

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Cells with highly branched processes and contact neuroglia directly; they secrete cerebrospinal fluid (CSF)

Ependymal cells

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Type of neuroglia that have large cell bodies with many processes

Astrocytes

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Type of neuroglia that have smaller cell bodies with fewer processes

Oligodendrocytes

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Type of neuroglia that has the smallest and least numerous neuroglia with many fine-branched
processes

Microglia

42

Functions of astrocytes

• Maintain blood–brain barrier (isolates CNS)
• Create three-dimensional framework for CNS
• Repair damaged neural tissue
• Guide neuron development
• Control interstitial environment

43

Function of oligodendrocytes

responsible for myelination

44

What are the benefits of myelination?

• Increases speed of action potentials
• Myelin insulates myelinated axons

45

Regions of CNS with many myelinated nerves

White matter

46

Unmyelinated areas of CNS

Gray matter

47

Masses of neuron cell bodies surrounded by neuroglia and are found in the PNS

Ganglia

48

Also called amphicytes, they surround ganglia and regulate environment around neuron

Satellite cells

49

Also called neurilemma cells, they form myelin sheath (neurilemma) around
peripheral axons

Schwann cells

50

The transmembrane potential of resting cell and ranges from –10 mV to –100 mV,
depending on cell type

Resting potential

51

Temporary, localized change in resting potential, caused by stimulus

Graded potential

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an electrical impulse produced by graded potential and propagates along surface of axon to synapse

Action potential

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resting potential of the neuron

70mV difference between the inside and
the outside

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powered by ATP and carries 3 Na+ out and 2 K+ in, balances passive forces of diffusion and maintains resting potential (–70 mV)

Sodium–potassium ATPase (exchange pump)

55

Channels that are always open and their permeability changes with conditions

Passive Channels (Leak Channels)

56

Channels that open and close in response to stimuli

Active Channels (Gated Channels)

57

How does an action potential fire?

• The action potential is a rapid depolarization
of the membrane.
• It starts at the axon hillock and passes quickly
along the axon.
• The membrane is quickly repolarized to allow
subsequent firing.

58

Four Steps in the Generation of Action Potentials

• Step 1: Depolarization to threshold
• Step 2: Activation of Na+ channels
• Step 3: Inactivation of Na+ channels and activation
of K+ channels
• Step 4: Return to normal permeability

59

What happens during rapid depolarization?

• When partial depolarization reaches the activation
threshold, voltage-gated sodium ion channels open.
• Sodium ions rush in.
• The membrane potential changes from -70mV to +40mV.

60

What happens during activation of Na+ channels (Step 2)?

• Rapid depolarization
• Na+ ions rush into cytoplasm
• Inner membrane changes from negative to positive

61

The time period from beginning of action potential to return to resting state, during which membrane will not respond normally to additional stimuli

Refractory Period

62

Moves action potentials generated in axon hillock along entire length of axon

Propagation

63

Two methods of propagating action potentials

1. Continuous propagation (unmyelinated axons)
2. Saltatory propagation (myelinated axons)

64

Steps in propagation

• Step 1: Action potential in segment 1
• Step 2: Depolarizes second segment to threshold
• Step 3: First segment enters refractory period
• Step 4: Local current depolarizes next segment

65

Method of propagating action potentials that occur along myelinated axon, and is faster and uses less energy than continuous
propagation; Myelin insulates axon which prevents continuous
propagation, so local current “jumps” from node to node and depolarization occurs only at nodes

Saltatory Propagation

66

The larger the diameter of an axon, the ________ the resistance

lower

67

Three Groups of Axons

1. Type A fibers
2. Type B fibers
3. Type C fibers

68

A group of axon that are myelinated, has a large diameter and high speed, and carry rapid information to/from CNS (ex: position, balance, touch, and motor
impulses)

Type A Fibers

69

A group of axon that are myelinated, has a medium diameter medium speed (18 m/sec) and carry intermediate signals (ex: sensory information, peripheral
effectors)

Type B Fibers

70

A group of axon that are unmyelinated, has a small diameter, slow speed (1 m/sec), and carry slower information (ex: involuntary muscle, gland controls)

Type C Fibers

71

Two Types of Synapses

1. Electrical synapses
2. Chemical synapses

72

Type of synapse involving direct physical contact between cells

Electrical synapses

73

Type of synapse involving signal transmission across a gap by chemical
neurotransmitters

Chemical synapses

74

Two Classes of Neurotransmitters

1. Excitatory neurotransmitters
2. Inhibitory neurotransmitters

75

Type of neurotransmitteres that cause depolarization of postsynaptic membranes and promote action potentials

Excitatory neurotransmitters

76

Type of neurotransmitteres that cause hyperpolarization of postsynaptic membranes and suppress action potentials

Inhibitory neurotransmitters

77

A type of neurotransmitter that usually promotes action potentials, but inhibits cardiac neuromuscular junctions

acetylcholine (ACh)

78

What are cholinergic synapses?

Any synapse that releases ACh at:
1. All neuromuscular junctions with skeletal muscle
fibers
2. Many synapses in CNS
3. All neuron-to-neuron synapses in PNS
4. All neuromuscular and neuroglandular junctions of
ANS parasympathetic division

79

Occurs when neurotransmitter cannot recycle fast
enough to meet demands of intense stimuli and synapse inactive until ACh is replenished

Synaptic Fatigue

80

Neurotransmitters that are released by adrenergic synapses, and have an excitatory and depolarizing effect

Norepinephrine (NE)

81

CNS neurotransmitter that may be excitatory or inhibitory and is involved in Parkinson’s disease and cocaine use

Dopamine

82

A CNS neurotransmitter that affects attention and emotional states

Serotonin

83

A neurotransmitter that has an inhibitory effect and functions in CNS

Gamma Aminobutyric Acid (GABA)

84

Characteristics of neuromodulators

• Effects are long term, slow to appear
• Responses involve multiple steps, intermediary compounds
• Affect presynaptic membrane, postsynaptic membrane, or
both
• Released alone or with a neurotransmitter

85

Neuromodulators that bind to receptors and activate
enzymes

Neuropeptides

86

Neuromodulators in the CNS that bind to the same receptors as opium or morphine and relieve pain

Opioids

87

Four Classes of Opioids

1. Endorphins
2. Enkephalins
3. Endomorphins
4. Dynorphins

88

Work through second messengers, and are enzyme complex that bind GTP; they are the link between neurotransmitter (first messenger) and
second messenger and they activate enzyme adenylate cyclase

G Proteins

89

Which activated enzyme produces messenger cyclic-AMP (cAMP)?

adenylate cyclase

90

Graded potentials developed in a postsynaptic cell in response to neurotransmitters

Postsynaptic Potentials

91

Two Types of Postsynaptic Potentials

1. Excitatory postsynaptic potential (EPSP)
2. Inhibitory postsynaptic potential (IPSP)

92

Graded depolarization of postsynaptic membrane

Excitatory postsynaptic potential (EPSP)

93

Graded hyperpolarization of postsynaptic membrane

Inhibitory postsynaptic potential (IPSP)

94

Two types of summations

1. Temporal summation
2. Spatial summation

95

Type of summation that occurs multiple times as rapid, repeated stimuli at one synapse

Temporal Summation

96

Type of summation that occurs in multiple locations and the stimuli arrive at multiple synapses

Spatial Summation

97

Action of an axoaxonic synapse at a synaptic terminal
that decreases the neurotransmitter released by
presynaptic membrane

Presynaptic inhibition

98

Action of an axoaxonic synapse at a synaptic terminal
that increases the neurotransmitter released by
presynaptic membrane

Presynaptic facilitation

99

Can alter either the rate of neurotransmitter release or
the response of a postsynaptic neuron to specific
neurotransmitters

Neuromodulators