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BIO 181-171 > CH 12: 9-20-13 (BIO 181) > Flashcards

CH 12: 9-20-13 (BIO 181) Flashcards

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Biology 101 flashcards
1
Q

the nervous system includes all ___ ____ in the body

A

neural tissue

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2
Q

____, ____ ___, ____ receptors, and nerves are all involved in the nervous system

A

brain, spinal cord, sensory receptors

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3
Q

nervous system divided into the ___ nervous system, and the ___ nervous system

A

central; peripheral

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4
Q
  • includes the brain and spinal cord
  • processing and coordinating of information
  • sensory information (input) from inside and outside body
  • motor commands (output) control activites of perpheral organs (skeletal muscles)
  • higher functions of brain: learning, memory, emotion and intelligence
A

CNS

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5
Q
  • includes all neurual issue outside the CNS
  • deliver sensory information to the CNS
  • carry motor commands to peripheral tissues and systems
  • consists of nerves that are bundles of fibes with connective tussues and blood vessels and carry sensory information and motor commands via
    - cranial nerves->connect to brain
    - spinal nerves -> attach to spinal cord
A

PNS

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6
Q

___ and ____ divisions of PNS

A

afferent; efferent

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7
Q
  • carries sensory information
  • contains receptors and effectors
  • receptors (source) detect changes or respond to stumuli, consist of neurons and highly specialized cells, complex sensory organs (eyes, ears)
  • effectors (target) respond to efferent signals and consist of target cells and organs
A

afferent division (input) of PNS

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8
Q
  • carries motor commands
  • from CNS to PNS muscles and glands
  • composed of the somatic and autonomic nervous system
A

efferent division (output) of PNS

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9
Q

nervous system in efferent division of PNS that controls skeletal muscle contractions (voluntary and involuntary muscles contractions)

A

somatic nervous system

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10
Q

nervous system in efferent division of PNS that

  • controls subconscious actions: contractions of smooth muscle and cardiac muscle and glandular secretions
  • sympathetic division has a stimulating effect
  • parasympathetic division has a relaxing effect
A

autonomic nervous system

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11
Q
  • the basic functional units of the nervous system
  • specialized cells that control and monitor body activities and physiological functions
  • sense changing conditions, process sensory input, and direct the body’s responses
  • come in all shapes and sizes but all have certain characteristics in common.
A

neurons

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12
Q
  • Contains nucleus and organelles
  • Large nucleus and nucleolus (the brain of neuronal cells)
  • Perikaryon (cytoplasm)
  • Nuclear Pores (provides a route for the transferring of information)
  • Mitochondria (produce energy)
  • RER and ribosomes (produce neurotransmitters)
  • Cytoskeleton consists of 3 types of filaments that give the cell structural support and enable some degree of motility/contractility
A

cell body (soma)

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13
Q

consists of 3 types of filaments that give the cell structural support and enable some degree of motility/contractility
• Together, these filiments keep the organelles suspended in the cytosol.

A

cytoskeleton

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14
Q

• _____and_____: resemble the microfilaments and microtubules seen in other cell types

A

Neurofilaments; neurotubules

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15
Q

bundles of neurofilaments that provide support for dendrites and axon

A

neurofibrils

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16
Q
  • Dense areas of RER and ribosomes

* Make neural tissue appear gray (gray matter)

A

nissl bodies

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17
Q
  • Highly branched projections from the soma

* Function in receiving information from extracellular environment, other cells, or other neurons

A

dendrites

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18
Q
  • Single long processes extending from the soma
  • Functions in sending out (or carrying) information to various targets
  • Carries electrical signal (action potential)
  • structure is critical to function
A

axon

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19
Q
  • Contain synaptic terminals, which contain synaptic vessicles that are filled with neurotransmitters
  • It is these neurotransmitters that, when released, affect the transmembrane potential of another cell
A

telondenria (collaterals)

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20
Q
  • Cytoplasm of axon

* Contains neurotubules, neurofibrils, enzymes, organelles

A

axoplasm

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21
Q
  • Specialized cell membrane of the axon

* Covers the axoplasm

A

axolemma

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22
Q
  • Thick section of cell body

* Attaches to initial segment

A

axon hillock

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23
Q

• Attaches to axon hillock

A

initial segment

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24
Q

fine extensions of distal axon

A

telodendria

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25
Q

tips of telodendria

A

synaptic terminals

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26
Q

area where neuron communicated with another cell

A

synpse

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27
Q

all synapses involve ___ and ___ cells

A

presynaptic; postsynaptic

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28
Q

– Cell that sends message (information)
– Usually a neuron
– Releases chemicals to the postsynaptic cell

A

presynaptic

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29
Q

– Cell that receives message (information)
– Can be a neuron or any other type of cell
• The synapse can be anywhere on the receiving cell

A

postsynaptic

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30
Q

• Synapse between neuron and muscle

A

neuromuscular junction

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31
Q

• Synapse between neuron and gland

A

neuroglandular junction

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32
Q
  • Is expanded area of axon of presynaptic neuron

* Contains synaptic vesicles of neurotransmitters

A

the synaptic knob (terminal buttons)

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33
Q
  • are chemical messengers
  • are released at presynaptic membrane
  • affect receptors of postsynaptic membrane
  • are broken down by enzymes
  • are reassembled at synaptic knob
A

neurotransmitters

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34
Q

Neurons are Classified into____ Types – Based on_____

A

four; structure

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35
Q
  • Found in brain and sense organs
  • Typically Smaller than other neurons
  • All cell processes look alike?……well, not really
  • Dendrites and axons are difficult to distinguish
  • Function is poorly understood
A

anazonic neruron

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36
Q
  • Found in special sensory organs (sight, smell, hearing)
  • Are small
  • One dendrite, one axon
  • Rare?
A

bipolar neurons

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37
Q
  • Found in sensory organs of the PNS
  • Have very long axons
  • Fused dendrites and axon
  • Cell body to one side
A

unipolar neuron

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38
Q
  • Common in the CNS
  • Include all skeletal muscle motor neurons
  • Have very long axons
  • Multiple dendrites, one axon
A

multipolar neurons

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39
Q
  • Afferent neurons of PNS

* Originate at the periphery and terminate in the CNS

A

• Sensory neurons

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40
Q
  • Efferent neurons of PNS

* Originate in the CNS and terminate at the effector organs (target)

A

• Motor neurons

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41
Q
  • Association neurons

* All located in the CNS

A

• Interneurons

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42
Q
  • Monitor internal environment (visceral sensory neurons)
  • Monitor effects of external environment (somatic sensory neurons)
  • Structure of sensory neurons
  • Cell bodies are grouped in sensory ganglia
  • afferent fibers extend from sensory receptors of the PNS to the CNS
A

• Functions of Sensory Neurons

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43
Q

carry instructions from CNS to peripheral effectors (targets)
• Via efferent fibers (axons)

A

Motor Neurons

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44
Q

• includes all somatic motor neurons that innervate skeletal muscles

A

• Somatic nervous system (SNS):

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45
Q
  • visceral motor neurons innervate all other peripheral effectors
  • e.g., smooth muscle, cardiac muscle, glands, adipose tissue
A

• Autonomic (visceral) nervous system (ANS):

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46
Q

• Motor neurons are grouped into

A

Ganglia (broad term = cluster of cell bodies)

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47
Q

• Neuronal cell bodies that make up the junction between_____ nerves originating from the CNS and autonomic nerves that innervate ___ organs

A

autonomic; peripheral

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48
Q

• Signals from CNS motor neurons to visceral effectors pass synapses at autonomic ganglia and then divide the axons into:

A

» preganglionic fibers

» postganglionic fibers

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49
Q

• Most interneurons are located in

A

brain, spinal cord, and autonomic ganglia

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50
Q
  • Between sensory and motor neurons

* These comprise over 90% of all neurons

A

Interneurons

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51
Q
  • Are responsible for Distribution of sensory information and Coordination of motor activity
  • Are involved in higher functions: Memory, planning, learning
A

Interneurons

52
Q
  • Half the volume of the nervous system
  • Many types of neuroglia in CNS and PNS
  • These are the cells that support and protect neurons
A

neuroglia

53
Q
  • Cell with highly branched processes; contact neuroglia directly
  • Form epithelium called ependyma
  • Line central canal of spinal cord and ventricles of brain:
  • secrete cerebrospinal fluid (CSF)
  • have cilia or microvilli that circulate CSF
  • monitor CSF
  • contain stem cells for repair
A

Neuroglia in the CNS

• Ependymal cells

54
Q
  • large cell bodies with many processes
  • Maintain blood–brain barrier (isolates CNS)
  • Repair damaged neural tissue
  • Guide neuronal development
  • Control interstitial environment
  • Absorb and recycle neurotransmitters
A

• Astrocytes (CNS)

55
Q

• smaller cell bodies with fewer processes
• Processes contact other neuron cell bodies
• Wrap around axons to form myelin sheaths
(a membrane that wraps around the axon, giving it electrical insulation)

A

• Oligodendrocytes (CNS)

56
Q
  • Fewest and smallest of all microglia in the CNS
  • Migrate throughout neural tissue
  • Clean up cellular debris, waste products, and pathogens
A

• Microglia (CNS)

57
Q

• Also called amphicytes
• Surround ganglia
• Regulate environment around neuron
– O2, CO2, and nutrient levels

A

• Satellite cells (PNS)

58
Q
  • Also called neurilemmocytes
  • Form myelin sheath (neurilemma) around peripheral axons
  • One Schwann cell sheaths one segment of axon:
  • many Schwann cells sheath entire axon
  • Participates in repair after injury
A

Schwann Cells (PNS)

59
Q
  • makes nerves appear white

* Nerves that are not myelinated appear gray

A

• Myelination

60
Q
  • internodes: myelinated segments of axon
  • nodes
  • gaps between internodes
  • Extremely important in conduction
A

• Nodes of Ranvier

61
Q

– 1 oligodendrocyte can myelinate

A

portions of several axons

62
Q

– 1 schwann cell can only myelinate

A

one segment of a single axon

63
Q

• myelin ____ myelinated axons

A

insulates

64
Q

myelin _____ speed of electrical signals (action potentials)

A

increases

65
Q

• Neurons perform all _______, information processing, and_____ functions of the nervous system

A

communication; control

66
Q

preserve physical and biochemical structure of neural tissue and are essential to survival and function of neurons

A

neuroglia

67
Q

• All plasma (cell) membranes produce____ signals by ion movements

A

electrical

68
Q

• Transmembrane potential exists due to a difference in _____ and _____ gradients between the inside and outside of cells

A

chemical; electrical

69
Q
  • The transmembrane potential of resting cell
  • The “reference point”
  • (Typically –70mV)
A

resting potential

70
Q
  • Temporary, localized change in resting potential

* Caused by stimulus

A

graded potential

71
Q
  • Is an electrical impulse
  • Produced by graded potential
  • Propagates along surface of axon to synapse
A

action potential

72
Q
  • Releases neurotransmitters at presynaptic membrane

* Produces graded potentials in postsynaptic membrane

A

synaptic activity

73
Q

• Response (integration of stimuli) of postsynaptic cell

A

information processing

74
Q

• Concentration gradient of ions (Na+, K+)
• Selectively permeable through channels
• Maintains charge difference across membrane (resting potential –70 mV)
– Based on chemical and electrical forces

A

• Three Requirements for Transmembrane Potential

75
Q
  • Typical neuron is permeable to potassium and sodium (via leak channels that are always open)
  • But, 25 times more permeable to______
A

potassium

76
Q

• Outside cell

– Lots of____ and chloride

A

sodium

77
Q

• Inside cell

– Lots of ____ and organic anions

A

potassium

78
Q
  • Chemical driving forces are pushing:
  • ____ out
  • ____in
A

K+; Na+

79
Q
  • Since the membrane is more permeable to K+

* K+ leaves cell ____ than Na+ enters

A

faster

80
Q
  • As a result, Electrical forces develop that want to push BOTH:
  • Na+ ___ cell
  • K+ ___ cell
A

into; into

81
Q

pump maintains this resting potential

A

sodium/potassium

82
Q

• The sum of chemical and electrical forces acting on a given ion

A

• Electrochemical Gradient

83
Q

• The transmembrane potential at which there is no net movement of a particular ion across the cell membrane
• Examples
K+ = –90 mV
Na+ = +66 mV
So, the resting membrane potential is closer to the potassium equilibrium potential

A

• Equilibrium Potential

84
Q
  • Transmembrane potential ___ or ___
  • In response to temporary changes in membrane permeability
  • Resulting from opening or closing specific membrane channels
A

rises; falls

85
Q

reference point

A

resting potential

86
Q

more postitive

A

depolarization

87
Q

more negative

A

repolarization

88
Q

more negative than the resting potential

A

hyperpolarization

89
Q

• Membrane permeability to Na+ and K+ determines changes in ____ potential

A

transmembrane

90
Q

– are always open

– permeability changes with conditions

A

passive channels (leak channels)

91
Q

– open and close in response to stimuli

– at the resting potential, most gated channels are closed

A

active channels (gated channels)

92
Q
  • Open in the presence of specific chemicals (e.g., ACh) at a binding site
  • Found on neuron cell body and dendrites
A

chemically gated channels

93
Q
  • Respond to changes in transmembrane potential
  • Have activation gates (open upon stimulation) and inactivation gates (close to stop Na+ influx)
  • Characteristic of excitable membrane
  • Found in neural axons, skeletal muscle, cardiac muscle
A

voltage-gated channels

94
Q
  • Respond to membrane distortion

* Found in sensory receptors (touch, pressure, vibration)

A

mechanically gated channels

95
Q

• Transmembrane potential exists across

A

plasma membrane

96
Q

• Cytosol (ICF) and extracellular fluid (ECF) have different

A

chemical/ionic balance

97
Q

• The plasma membrane is

A

selectively permeable

98
Q

• Changes in the Transmembrane potential occur

A

in response to chemical or physical stimuli

99
Q
  • Graded Potentials

* Action Potentials

A

two types of transmembrane potentials

100
Q
  • Also called local potentials
  • Changes in transmembrane potential that cannot spread far from the site of stimulation
  • Any stimulus that opens a gated channel produces a graded potential
  • determine whether or not an action potential will occur
A

graded potentials

101
Q

• Opening sodium channel produces graded potential:
– resting membrane exposed to chemical (Na+)
– sodium channel opens
– sodium ions enter the cell
– transmembrane potential rises (becomes more positive)
– depolarization occurs

A

Graded Potentials: The Resting State

102
Q
  • A shift in transmembrane potential toward 0 mV or becomes more positive:
  • movement of Na+ through channel
  • produces local current
  • depolarizes nearby plasma membrane (graded potential)
  • change in potential is proportional to stimulus
A

Graded Potentials: Depolarization

103
Q

a ____ is produced by the spread of sodium ions inside the membrane.
•This results in depolarization of adjacent portions of the plasma membrane – and this continues

A

local current

104
Q
  • The transmembrane potential is most affected at the site of stimulation – and this affect decreases with distance
  • The effect spreads passively via local currents
  • Whether the membrane depolarizes or hyperpolarizes in response to a given stimulus, depends on the nature of channels that are involved in the membrane itself
  • The strength of the response is determined by the strength of the stimulus
A

graded potentials

105
Q

• When the stimulus is removed, transmembrane potential returns to normal resting potential

A

repolarization

106
Q
  • Here, the stimulus causes the opening of K+ channels
  • When K+ channels open, positive ions move OUT of the cell (not in)
  • This Increases the negativity of the resting potential
  • Opposite effect of opening a sodium channel
  • But when stimulus is removed, potential returns to rest
A

hyperpolarization

107
Q

• The effect of _______ depends on WHERE they happen:
• At cell dendrites or cell bodies:
– trigger specific cell functions
– e.g., exocytosis of glandular secretions
• At motor end plate:
– releases ACh or other neurotransmitters into synaptic cleft

A

Graded Potentials

108
Q
  • Propagated changes in transmembrane potential
  • Affect an entire excitable membrane
  • Link graded potentials at cell body with motor end plate actions
A

action potential = nerve impulses

109
Q

• A graded depolarization of axon hillock large enough (10 to 15 mV) to change resting potential
( -70 mV) to threshold level of voltage-gated sodium channels (–60 to –55 mV)

A

• Initial stimulus must reach threshold!

110
Q

• If a stimulus exceeds threshold amount:
– the action potential is the same
– no matter how large the stimulus
• Action potential is either triggered, or not!

A

• All-or-none principle

111
Q

Resting State Prior to Action Potential

A
  • Na+ activation gate = closed
  • Na+ inactivation gate = open
  • K+ gate = closed
112
Q
  • Step 1: Depolarization to threshold
  • Step 2: Activation of Na+ channels
  • Step 3: Inactivation of Na+ channels, activation of K+ channels
  • Step 4: Return to normal permeability
A

Four Steps in the Generation of

Action Potentials

113
Q
  • From beginning of action potential to the return to resting state
  • During this time, the membrane will not respond normally to additional stimuli
A

refectory period

114
Q
  • Sodium channels open or inactivated

* No action potential possible

A

absolute refractory period

115
Q
  • Membrane potential almost normal

* BUT, Very large stimulus can initiate action potential

A

• Relative refractory period

116
Q
  • The movement of action potentials that have been generated in axon hillock
  • This travels along the entire length of the axon
  • Consists of a series of repeated actions, NOT passive flow (as we saw in graded potentials)
A

• Propagation

117
Q
  • Continuous propagation: ______ axons

* Saltatory propagation: ______ axons

A

unmyelinated; myelinated

118
Q

unmyelinated axon propagation is very ____, repeats in ___ like fashion (tiny steps)

A

slow; chain

119
Q
  • Faster and uses less energy than continuous propagation
  • Myelin insulates axon and prevents continuous propagation
  • Local current “jumps” from node to node
  • Thus, Depolarization occurs only at nodes (rather than along the entire length of the axon in tiny steps)
A

Saltatory Propagation along Myelinated Axon

120
Q

• Axons behave like electrical cables, so the speed at which action potentials are propagated are determined by

A

axon diameter and mylenation

121
Q

» Large axon =___ propagation

» Small axon = ___ propagation

A

fast; slow

122
Q

» Myelinated axons =____ propagation

» Unmyelinated axons = ___ propagation

A

fast; slow

123
Q

• The most important information (vision, balance, motor commands) is carried by

A

large-diameter, myelinated axons

124
Q
  • Are transmitted from presynaptic neuron
  • To postsynaptic neuron (or other postsynaptic cell)
  • Across a synapse
A

• Action potentials (nerve impulses)

125
Q
  • Direct physical contact between cells
  • Are locked together at gap junctions (connexons)
  • Allow ions to pass between cells
  • Produce continuous local current and action potential propagation
  • Are found in areas of brain, eye, ciliary ganglia
A

• Electrical Synapses

126
Q
  • Signal transmitted across a gap by chemical neurotransmitters
  • Are found in most synapses between neurons and all synapses between neurons and other cells
  • Cells not in direct contact
  • Action potential may or may not be propagated to postsynaptic cell, depending on
  • Amount of neurotransmitter released
  • Sensitivity of postsynaptic cell
A

• Chemical Synapses

BIO 181-171 (12 decks)

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