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BIOL 223 Lecture > CH 11 - Functional Organization Of Nervous Tissue > Flashcards

CH 11 - Functional Organization Of Nervous Tissue Flashcards

1
Q

What are the 3 functions of the nervous system?

A

Sensory input (afferent), integration, motor output (efferent)

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2
Q

Afferent

A

Sensory input

Information is gathered from various sensory receptors inside and outside the body to monitor for changes

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3
Q

Integration

A

The processing and interpretation of incoming information from the sensory input

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4
Q

Efferent

A

Motor output

Effecting a response by activating or suppressing effectors

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5
Q

What are considered effectors?

A

Muscles, glands, organs, and tissues

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6
Q

What makes up the central nervous system?

A

The brain and spinal cord

Also nervous tissue, connective tissue, and blood vessels

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7
Q

What are the functions of the central nervous system?

A

Process & coordinate:

Internal/external sensory info

Peripheral organ activity

Higher functions (intelligence, memory, learning, emotion)

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8
Q

What makes up the peripheral nervous system?

A

All neural tissue outside of the CNS

Also cranial/spinal nerves, connective tissue, and blood vessels

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9
Q

What are the functions of the peripheral nervous system?

A

Carry sensory info to the CNS

Carry motor commands from the CNS

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10
Q

What do somatic sensory neurons monitor?

A

The external environment and positions within it

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11
Q

Where are the sensory receptors from in somatic sensory?

A

Skin, skeletal muscle, joints

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12
Q

Where are the sensory receptors from in visceral sensory?

A

Organs, tissues, smooth muscle

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13
Q

What do visceral sensory neurons monitor?

A

Internal environment and status of other organ systems

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14
Q

What information comes from special sense organs?

A

Seeing, hearing, balance & equilibrium, smell, taste

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15
Q

What is the somatic nervous system?

A

The voluntary nervous system

Effectors: skeletal muscles

Neurons: somatic motor neurons

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16
Q

What is the autonomic nervous system?

A

The involuntary nervous system

Effectors: everything except skeletal muscles

Neurons: 2 visceral motor neurons

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17
Q

What are the 2 divisions of the autonomic nervous system?

A

Sympathetic - fight or flight

Parasympathetic - rest and digest

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18
Q

Cranial nerve I

A

Olfactory

From olfactory receptors

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19
Q

Cranial nerve II

A

Optic

From retina of eye

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20
Q

Cranial nerve III

A

Oculomotor

To eye muscles

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21
Q

Cranial nerve IV

A

Trochlear

To eye muscles

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22
Q

Cranial nerve V

A

Trigeminal

From mouth and jaw muscles

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23
Q

Cranial nerve VI

A

Abducens

To eye muscles

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24
Q

Cranial nerve VII

A

Facial

From taste buds
To facial muscles and glands

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25
Q

Cranial nerve VIII

A

Vestibulocochlear

From inner ear

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26
Q

Cranial nerve IX

A

Glossopharyngeal

From pharynx
To pharyngeal muscles

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27
Q

Cranial nerve X

A

Vagus

From/to internal organs

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28
Q

Cranial nerve XI

A

Accessory

To neck and back muscles

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29
Q

Cranial nerve XII

A

Hypoglossal

To tongue muscles

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30
Q

List the spinal nerves.

A

Cervical nerves (C1-C8)

Thoracic nerves (T1-T12)

Lumbar nerves (L1-L5)

Sacral nerves (S1-S5)

Coccygeal nerve (C0)

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31
Q

What is a neuron?

A

Highly specialized cells that are the structural units of the nervous system

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32
Q

What is the function of a neuron?

A

Perform all communication (via nerve impulses), information processing, and control functions of the nervous system

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33
Q

What are 3 characteristics of neurons?

A

Extreme longevity - lasts a lifetime

Amitotic - cannot regenerate

High metabolic rate - aerobic respiration

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34
Q

What are the 4 regions of a multipolar neuron?

A

Cell body (soma) - contains the nucleus

Dendrites - short, branched processes off the soma

Axon - a single long process

Telodendria - terminal branches off the axon

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35
Q

Descibe the cytoskeleton of the cell body.

A

Consists of neurofilaments, neurotubules, microfilaments

Helps maintain shape/structure

Moves materials between cell body and axon

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36
Q

Nuclei

A

Clusters of cell bodies in the CNS

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37
Q

Ganglia

A

Clusters of cell bodies in the PNS

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38
Q

Nissl bodies

A

Free ribosomes and rough endoplasmic reticulum that gives the soma a grey color

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39
Q

Neurofibrils

A

Bundles of neurofilaments in the soma

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40
Q

Describe and list the functions of dendrites.

A

Main input region of the neuron that is branched to increase surface area

Convey incoming info as a graded potential toward the cell body

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41
Q

Dendritic spines

A

Points of contact with other neurons at the end of a dendrite

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42
Q

Describe an axon and its functions.

A

Conducting component of a neuron
*One per neuron

Carries an action potential away from the cell body

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43
Q

Axoplasm

A

Cytoplasm of an axon

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44
Q

Axolemma

A

Plasma membrane of an axon

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45
Q

Axon Hillock

A

Cone-shaped thickened area of the cell body that joins the initial segment of axon

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46
Q

Trigger zone

A

Axon hillock plus the initial segment of axon

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47
Q

Axon collaterals

A

Side branches along the length of the axon

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48
Q

Telodendria (terminal branches)

A

End branches of the axon

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49
Q

Synaptic knob

A

Very ends of the axon where neurotransmitters are exocytosed and released into the synaptic cleft

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50
Q

Where are graded potentials generated?

A

On plasma membranes of dendrites and the cell body

*Becomes an action potential at the trigger zone

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51
Q

Where are action potentials generated?

A

On axolemma

*Travels to synaptic knobs

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52
Q

Anterograde movement

A

Movement toward the axon terminal carried out by kinesin

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53
Q

Kinesin

A

A molecular motor protein

Carries: mitochondria, cytoskeleton elements, membrane components, enzymes, and neurotransmitters

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54
Q

Retrograde movement

A

Movement toward the cell body carried out by dynein

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55
Q

Dynein

A

A molecular motor protein

Carries: recycled organelles

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56
Q

Synapse

A

Specialized site where a neuron communicates with another cell

*Every synapse involves 2 cells

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57
Q

Presynaptic neuron

A

Neuron that sends the message

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58
Q

Postsynaptic neuron

A

Neuron that receives the message

*Can be another neuron, a muscle cell, or a gland cell

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59
Q

What are 5 types of synapses?

A 
Neuromuscular junction 
Neuroglandular junction
Axodendritic 
Axosomatic
Axoaxonic
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60
Q

Synaptic cleft

A

The small gap that separates the presynaptic and postsynaptic membranes

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61
Q

Neurotransmitter

A

Chemical messengers released at presynaptic membrane into synaptic cleft that affect receptors of the postsynaptic membrane

62
Q

What are the 3 structural classifications of neurons?

A

Unipolar, bipolar, multipolar

63
Q

Describe unipolar neurons.

A

Found in sensory neurons of PNS

They have very long axons (fused to the dendrites) and a cell body on one side

64
Q

Describe bipolar neurons.

A

Rarest, but found in special sensory organs

Cell body is before the trigger zone

65
Q

Describe multipolar neurons.

A

Most common type in the body, CNS

Multiple dendrites and one long axon

*All somatic motor neurons are multipolar

66
Q

What are the 3 functional classifications of neurons?

A

Sensory (afferent), motor (efferent), interneurons (association neurons)

67
Q

What do sensory neurons do?

A

Transmit impulses from sensory receptors in skin/internal organs toward the CNS

*All sensory neurons are unipolar except the bipolar special sense organs

68
Q

What do motor neurons do?

A

Carry impulses away from the CNS to the effectors

*All are multipolar

69
Q

What do interneurons do?

A

Lie between sensory and motor neurons in neural pathways and shuttle signals through CNS pathways where integration occurs

  • Outnumber all other neuron types combined
  • Most located within CNS
  • More complex the response to a stimulus, the more interneurons will be involved
70
Q

What are 3 types of sensory receptors?

A

Interoceptors, exteroceptors, proprioceptors

71
Q

What do interoceptors do?

A

Provide info about the internal environment

Monitor internal systems (digestive, urinary..)
and internal senses (taste, pain…)

72
Q

What do exteroceptors do?

A

Provide info about the external environment

External senses (touch, temperature...)
and distance senses (sight, smell...)
73
Q

What do proprioceptors do?

A

Monitor position and movement of skeletal muscle and joints

74
Q

What are Neuroglia?

A

The supporting cell to the neuron

*Smaller and 25x higher population

75
Q

Name the 4 types of glial cells in the CNS, and the 2 in the PNS.

A

CNS: ependymal cells, microglia, astrocytes, oligodendrocytes

PNS: satellite cells, Schwann cells

76
Q

Describe ependymal cells.

A

Line the central canal in the spine and ventricles in the brain

Form an ependyma (simple cuboidal/columnar epithelium)

Forms the blood-CSF barrier

Secretes CSF into ventricles and remove waste from CSF

77
Q

Describe microglia.

A

Least numerous and smallest Neuroglia

Long processes that touch/monitor health of nearby neurons

Phagocytic cells

Migrate through neural tissue

78
Q

List the functions of astrocytes.

A

Maintain blood-brain barrier with processes that wrap around capillaries

Regulate embryonic neuron development

Control interstitial/chemical environment

Aid learning/memory by forming neuronal synapses

Repair damaged neural tissue

79
Q

Describe oligodendrocytes.

A

Aids structural organization by tying clusters of axons together

Wraps axons in a myelin sheath

80
Q

What does myelination do?

A

Increases the speed of action potentials

Makes nerves appear white

81
Q

Nodes of ranvier

A

Gaps between internodes, and sites of potential axon collaterals

82
Q

Internodes

A

Myelinated segments of the axon

83
Q

Describe satellite cells.

A

Surround PNS cell bodies

Regulate environment around the neuron (PNS version of the astrocyte)

84
Q

Describe Schwann cells.

A

Form a myelin sheath around PNS axons (PNS version of oligodendrocytes)
*Takes multiple Schwann cells to fully enclose axon

Wallerian degeneration (regeneration of peripheral nerve fibers)

85
Q

Neurolemma

A

Plasma membrane of a Schwann cell

86
Q

Voltage

A

Measurement of electrical potential energy created by the separation of opposite charges

Units of volts (V) or millivolts (mV)

87
Q

Current

A

The flow of electrical charge from one point to another that can be used to do work

Units of Amperes (A) or milliamperes (mA)

*Amount of charge (current) that moves between the points depends on voltage and resistance

88
Q

Resistance

A

The hindrance to charge flow by a substance through which the current must pass

Unit of ohms

*A measure of how much the membrane restricts ion movement (membrane resistance)

89
Q

Tell whether the concentrations are higher inside or outside of the cell: sodium, potassium, calcium, chloride.

A

Sodium: higher outside

Potassium: higher inside

Calcium: higher outside

Chloride: higher outside

90
Q

What activates a leak channel?

A

Randomly activates (passive)

  • Establishes resting membrane potential
  • NOKIA
91
Q

What are 3 types of gated channels?

A

Ligand-gated, voltage-gated, mechanically-gated

*Active channels

92
Q

What activates a ligand-gated channel?

A

The binding of a specific chemical

*Most common on dendrites/soma

93
Q

What activates a voltage-gated channel?

A

Changes in the transmembrane potential (membrane potential)

94
Q

What activates a mechanically-gated channel?

A

Physical distortion of membrane surface

*Sensory receptors that respond to touch…

95
Q

Resting membrane potential

A

-70mV, but varies with time and cell type

All neural activity begins with a change in resting potential of a neuron

96
Q

Electrogenic pump

A

A transport protein that generates voltage across a membrane

*Na+ - K+ ATPase pump contributes to the voltage potential across the plasma membrane (NOKIA)

97
Q

Electrochemical gradient

A

Drives the diffusion of ions across a membrane

Made of:
Chemical gradient (the ion’s concentration gradient)
Electrical gradient (the effect of the membrane potential on the ion’s movement)
98
Q

Depolarization

A

Reduction in membrane potential (inner leaflet less negative)

99
Q

Hyperpolarization

A

Increase in membrane potential (inner leaflet more negative)

100
Q

Repolarization

A

Process of restoring resting membrane potential (return to -70mV) from a less negative number

*Called return to resting potential when going from more negative to resting membrane potential)

101
Q

Graded potential

A

Short distance signals that open ligand or mechanically-gated channels

A temporary, localized change in the resting potential that decreases with distance from stimulus

102
Q

Action potential

A

Long distance signals along plasma membrane of axon that do not diminish with distance from source

Opens voltage-gated channels

GP -> AP at trigger zone (membrane potential must be -55mV)

*Once initiated at threshold potential (-55mV) cannot be undone “all-or-nothing”

103
Q

Why can’t action potentials generate from dendrites?

A

Dendrites only have ligand-gated or mechanically-gated channels, not voltage-gated channels

104
Q

What happens at -70mV?

A

Voltage-gated Na+ inactivation gate channels open

Voltage-gated Na+ activation gate channels close

*Graded response from Na+ influx depolarizes to -55mV

105
Q

What happens at -55mV?

A

Voltage-gated Na+ inactivation gate channels open

Voltage-gated Na+ activation gate channels open

*Results in rapid Na+ influx, depolarizing to +30mV

106
Q

What happens at +30mV?

A

Voltage-gated Na+ inactivation gate channels close

Voltage-gated Na+ activation gate channels remain open

Voltage-gated K+ channels open, resulting in repolarization to -70mV

107
Q

What happens at the return to -70mV?

A

Voltage-gated Na+ inactivation gate channels open

Voltage-gated Na+ activation gate channels close

Voltage-gated K+ channels begin slowly closing, resulting in hyperpolarization to -90mV

108
Q

What happens at -90mV?

A

Voltage-gated K+ channels fully close, resulting in return to resting potential of -70mV

109
Q

What are the 2 methods of propagating action potentials?

A

Continuous propagation and saltatory propagation

110
Q

Continuous propagation

A

Occurs in unmyelinated axons

Both activation and inactivation gates of voltage-gated sodium channels open and sodium enters. Sodium that enters segment 1 spreads to segment 2, bringing it to threshold for another AP, while segment 1 repolarizes. Continue down the axolemma until it reaches the synaptic knob

111
Q

Saltatory propagation

A

Occurs in myelinated axons

Action potential jumps from node to node between myelinated internodes, for the same reasons as continuous propagation

Faster

112
Q

What do propagation velocities (speeds of AP propagation) depend upon?

A

Axon diameter- larger diameter, lower resistance, faster propagation

Degree of myelination- faster in myelinated axons

Temperature- lower temp, slower propagation

113
Q

Describe type A fibers:

Size
Myelination
Speed/type
Where found

A

Large
Thick myelin
Fast, saltatory
Somatic sensory neurons, somatic motor neurons

114
Q

Describe type B fibers:

Size
Myelination
Speed/type
Where found

A

Medium
Light myelin
Medium, saltatory
Visceral sensory neurons, all pre-ganglionic axons of ANS

115
Q

Describe type C fibers:

Size
Myelination
Speed/type
Where found

A

Small
No myelin
Slow, continuous
Some somatic sensory, some visceral sensory, and all post-ganglionic axons of ANS

116
Q

What are the 2 varieties of synapses?

A

Electrical and chemical

117
Q

Electrical synapses

A

Rare

Presynaptic and postsynaptic membranes are connected by gap junctions

Propagation of AP travels very quickly resulting in the electrically coupled cells having a simultaneous AP

118
Q

Chemical synapses

A

Synaptic end bulb releases a neurotransmitter that binds to the postsynaptic plasma membrane, producing a GP there

Common; unidirectional communication

119
Q

What do excitatory neurotransmitters do?

A

Promotes the generation of action potentials by causing depolarization

*Neurotransmitters are excitatory or inhibitory depending on what type of channel it opens

120
Q

What do inhibitory neurotransmitters do?

A

Suppresses the generation of action potentials by causing hyperpolarization

*Neurotransmitters are excitatory or inhibitory depending on what type of channel it opens

121
Q

List the 7 steps that happen at a chemical synapse.

A
  1. Nerve AP arrives at synaptic end bulb of presynaptic axon
  2. Voltage-gated calcium channels open and calcium diffuses into neuron
  3. Increased intercellular calcium concentration triggers exocytosis of neurotransmitters into synaptic cleft
  4. Neurotransmitters bind to receptors on postsynaptic cell
  5. Ligand-gated channels open allowing influx/reflux of sodium, potassium, or chloride
  6. Change in resting membrane potential (depolarization or hyperpolarization)
  7. If threshold is reached, AP is initiated on the postsynaptic cell (neuron or effector)
122
Q

Postsynaptic potential

A

Graded potential that develops in the postsynaptic membrane of the soma or dendrites in response to a neurotransmitter

123
Q

What are the 2 types of postsynaptic potentials?

A

Excitatory (EPSP) & inhibitory (IPSP)

124
Q

Excitatory postsynaptic potential

A

Graded depolarization caused by neurotransmitter binding to postsynaptic membrane receptors

Results from opening of ligand-gated sodium channels

Increases a postsynaptic neuron’s ability to generate an AP because it is closer to threshold voltage

125
Q

Inhibitory postsynaptic potential

A

Graded hyperpolarization caused by neurotransmitters binding to postsynaptic membrane

Results from opening of ligand-gated potassium or chloride channels

Reduces a postsynaptic neuron’s ability to generate an AP because it is father from threshold voltage

126
Q

Summation

A

The adding of EPSP’s together in order to increase probability of reaching threshold potential to produce an action potential in the postsynaptic neuron

*Single EPSP’s cannot induce an AP

127
Q

Spatial summation

A

Occurs when sources of stimulation arrive simultaneously but at different locations

Causes large amounts of neurotransmitters to be released together that increase depolarization at trigger zone

128
Q

Temporal summation

A

Occurs when one synapse receives stimuli occurring in rapid succession

Burts of neurotransmitters are released in quick succession, causing more and more ligand-gated channels to open, increasing degree of depolarization

129
Q

Why do neurotransmitter effects need to be terminated?

A

As long as a neurotransmitter is bound to its postsynaptic receptor, it will continue to affect membrane permeability and block additional messages from presynaptic neurons

130
Q

What are 3 mechanisms to terminate a neurotransmitter’s effects?

A

Degradation by enzyme, reuptake by cells, diffusion away

131
Q

Describe degradation by enzymes.

A

An enzyme will be present on the postsynaptic membrane or synaptic cleft that will break down the neurotransmitter

132
Q

Describe reuptake by cells.

A

The neurotransmitter will be taken up by astrocytes or the presynaptic terminal to be stored or destroyed by enzymes via neurotransmitter transporters

133
Q

Describe diffusion away.

A

The neurotransmitter will diffuse away from the synapse

134
Q

Name 2 excitatory amino acids.

A

Glutamate, aspartate

135
Q

Name 2 inhibitory amino acids.

A

Gamma-aminobutyric acid (GABA),

glycine

136
Q

Neuropeptides

A

Neurotransmitters consisting of 3-40 amino acids

Numerous and widespread in CNS and PNS

Many function as hormones that regulate physiological responses in the body

137
Q

Describe substance P.

A

Found in sensory neurons, spinal cord pathways, and parts of the brain associated with pain

Enhances perception of pain

138
Q

Neural circuits

A

Functional groups of neurons that process specific types of information

139
Q

What are 4 types of neural circuits?

A

Diverging circuits
Converging circuits
Reverberating circuits
Parallel after-discharge circuits

140
Q

Describe diverging circuits.

A

One input, many outputs

An amplifying circuit

141
Q

Describe converging circuits.

A

Many inputs, one output

A concentrating circuit

142
Q

Describe reverberating circuits.

A

Signal travels through a chain of neurons, each feeding back to previous neurons

An oscillating circuit that controlls rhythmic activity

143
Q

Describe parallel after-discharge circuits.

A

Signal stimulates neurons arranged in parallel arrays that eventually converge on a single output cell

Impulses reach output cell at different times, causing a burst of impulses called an after-discharge

144
Q

Rabies

A

A viral infection of the nervous system transferred to humans by the bites of infected animals that causes brain inflammation, delirium and death

Virus transported via retrograde movement in peripheral nerve axons to the CNS

145
Q

Multiple sclerosis

A

Demyelinating autoimmune disease

Symptoms: visual/speech disturbances, muscle weakness/paralysis, urinary incontinence

146
Q

Neuropathy

A

Any disease of nervous tissue, particularly degenerative diseases of nerves

147
Q

Neurotoxin

A

A substance that is poisonous or destructive to nervous tissue

148
Q

Shingles

A

A viral infection of sensory neurons serving the skin, characterized by scaly/painful blisters lasting for weeks, caused by varicella-zoster virus

When dormant, it remains in the sensory ganglia until immune system is weakened

149
Q

Hansen’s disease (leprosy)

A

A disease caused by mycobacterium leprae that results in skin sores, nerve damage, and muscle weakness that worsens over time

Not contagious, long incubation period

More common in children

150
Q

Compare Schwann cells, myelin sheaths, and internodes.

A

Schwann cell- glial cell responsible for myelinating PNS axons

Myelin sheath- layers of Schwann cell’s plasma membrane that cover the axon

Internode- length of Schwann cell or myelin sheath

151
Q

Absolute refractory

A

The period when no action potential can be generated regardless of strength of the stimulus

152
Q

Transmembrane potential

A

Potential difference measured in volts or millivolts in plasma membranes

Measured at the inner leaflet, so value will always be negative

BIOL 223 Lecture (26 decks)

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