Nervous Tissue Flashcards
(149 cards)
1
Q
What provides for the generation of nerve impulses (action potentials) that communicate with a regulate most body tissues?
A
Nervous tissue
2
Q
Who shares responsibility for maintaining homeostasis?
A
The nervous system and the endocrine system
3
Q
The nervous system regulates?
A
Body activities by responding rapidly using nerve impulses
4
Q
The endocrine system responds faster or slower by use of hormones to changes in homeostasis?
A
Slower
5
Q
What is the branch of medical science that deals with the normal functioning and disorders of the nervous system?
A
Neurology
6
Q
What comprises the central nervous system?
A
Brain
Spinal Cord
7
Q
What comprises the peripheral nervous system?
A
Cranial nerves (12 pairs; 1-Xii) Spinal nerves (31 pairs) Peripheral nerves (numerous)
8
Q
The nervous systems comprises?
A
The brain Spinal cord Spinal nerves Ganglia Enteric Plexuses Sensory receptors
9
Q
Which receptors detect changes in the internal or external environment?
A
Sensory
10
Q
Sensory neurons are afferent or efferent neurons?
A
Afferent neurons
11
Q
Sensory nerve cells (neurons) carry the sensory information from the receptor to the?
A
brain and spinal cord
12
Q
What do the integrative neurons do?
A
Analyze and store information
Make decisions
13
Q
Many integrative neurons are what kind of neurons?
A
Interneurons
14
Q
What are relatively short neurons in the brain, spinal cord, ganglia that connect to nearby neurons?
A
Integrative
15
Q
Which neurons respond to decisions and are efferent neurons?
A
Motor neurons
16
Q
Motor neurons carry information from the brain and spinal cord to?
A
Effectors (muscles or glands)
17
Q
What are somatic senses? What kind of motor control?
A
Sensation from body wall, limbs, head, and special senses (sight, hearing, taste, balance, smell)
Motor control of skeletal muscle (voluntary control)
18
Q
What are autonomic senses? What kind of motor control?
A
Sensation from internal organs like heart, lungs, bladder
Motor control of smooth and cardiac muscle, glands (involuntary control)
19
Q
What are Enteric senses? What kind of motor control?
A
Sensation from gastrointestinal tract
Motor control of smooth muscle and glands of the GI tract (involuntary control)
20
Q
The peripheral nervous system consists of all nervous tissue outside of the?
A
Central Nervous System
-SNS, ANS, ENS
21
Q
Each subdivision of the PNS has both of these neurons?
A
Sensory and motor neurons
22
Q
The motor part of the autonomic nervous system consists of what two branches?
A
Sympathetic division
Parasympathetic division
23
Q
What is an association (a bundle) of neuronal axons in the peripheral nervous system?
A
Nerve
24
Q
What is a group of neuronal cell bodies in the peripheral nervous system (plus associated tissue)?
A
Ganglion
25
What is an association (a bundle) of neuronal axons in the central nervous system?
Tract
26
What is an association (a bundle) of (unmyelinated) nerve cell bodies in the central nervous system?
Nucleus
27
What is an extensive network of nerves found within the peripheral nervous system (PNS)?
Plexus
28
The term plexus is also applied to?
A network of veins or lymphatic vessels
29
What are cells that have the property of electrical excitability, and are specially adapted to produce and transmit action potentials?
Neurons
30
What are cells of the nervous system that support, nourish, and protect the neurons?
Neuroglia
31
True or False
| There are less neuroglia than neurons
False
| There are more neuroglia
32
What are the basic parts of a neuron?
The cell body
| Nerve Fibers
33
What are nerve fibers comprised of?
An Axon
| Dendrites
34
What are the name adaptations for neurons?
Axoplasm (cytoplasm)
| Axolemma (plasmalemma)
35
Like most cells, what structures do neurons have (think organelles)?
Nucleus
Cytoplasm
Typical organelles
36
What are Nissl bodies?
Specialized forms of typical organelles in the neuron which are prominent clusters of rough ER
37
What are dendrites?
The receiving portion of a neuron
Typically short, tapering, highly branched
(incoming)
38
What is an axon?
Propagates impulses to another neuron, muscle, or nerve.
Can approximate three feet long in humans.
(outgoing)
39
How many axons are there per neuron?
Only a single axon
40
Where do axons typically arise from?
An elevation in the cell body called the axon hillock (= small hill)
41
In the axon, where do (action potentials) generally arise?
In the trigger zone
42
What is the trigger zone of the axon?
The junction of hillock and initial segment
43
What dies if the an axon is cut?
The distal fragment dies
44
What does the axon contain?
Mitochondria
Microtubules
Neurofibrils
45
What does the axon not contain?
Rough ER so protein synthesis does not occur in the axon
46
What may branch off of the main axon?
Axon collaterals
47
Axon and collateral end by dividing into what?
Axon terminals (telodendria)
48
Telodendria end in either?
Synaptic end bulbs, bulb-shaped structures
| Varicosities, string of swollen bumps
49
What is the cytoskeleton of a neuron made of?
Neurofibrils
| Microtubules
50
What are neurofibrils of the cytoskeleton made of?
Intermediate filaments
| Provide cell shape and support
51
What are microtubules of the cytoskeleton made of?
Tubulin
| Participate in moving material between the cell body and axon
52
What contains only some cytosol, mitochondria, cytoskeleton, smooth endoplasmic reticulum, and synaptic vesicles?
Axon terminals
53
Where does synthesis of new proteins, vesicles, etc. take place in the neuron?
The cell body
54
About how far apart might the cell body and axon terminals be?
Over a meter apart
55
Things made in the cell body must be transported along the?
Interior of the axon to reach the axon terminal
56
What is one-way only transport from cell body to axon terminals?
Slow axonal transport
57
What is two-way transport, both toward and away from the cell body?
Fast axonal transport
58
What transports axoplasm to growing or regenerating axons?
Slow axonal transport
59
What uses microtubules as tracks and motors?
Fast axonal transport
60
What transports organelles and materials that are used to form axolemma membranes, synaptic end bulbs, and synaptic vesicles?
Fast axonal transport
61
What is structural classification of a neuron based on?
The number of processes extending from the cell body
62
Which class of neurons have several dendrites and only one axon and are located throughout the brain and spinal cord?
Multipolar neurons
63
The vast majority of the neurons in the human body are?
Multipolar neurons
64
Which class of neurons have one main dendrite and one axon?
Bipolar neurons
65
Which class of neurons are used to convey the special senses of sight, smell, hearing and balance?
Bipolar neurons
66
Where are Bipolar neurons found?
In the retina of the eye, the inner ear, and the olfactory area of the brain.
67
Which class contain one process which extends from the body and divides into a central branch that functions as an axon?
Unipolar (pseudounipolar) neuron
68
When is the unipolar structure often employed for?
Sensory neurons that convey touch and stretching information from the extremities.
69
In cases of injury or disease, what can multiply to fill in the spaces formerly occupied by neurons?
Neuroglia
70
What are characteristics of neuroglia?
Not excitable cells
Smaller, more numerous than neurons
Make up about half the volume of the CNS
71
What are Neuroglia of the CNS?
Astrocytes
Oligodendrocytes
Microglia
Ependymal Cells
72
What are the neuroglia of the PNS?
```
Schwann Cells (neurolemmocytes)
Satellite cells
```
73
The neuroglia of the PNS is completely surround the what?
Axons and cell bodies of neurons
74
These do not typically undergo mitosis, meaning if a neuron dies there is no reservoir of cells to replace it...
Neurons
75
Mitosis of nervous system cells
| These do undergo mitosis
Neuroglial cells
76
Myelin is produced by?
Schwann cells and oligodendrocytes
77
What is multi-layered complex of lipids and proteins, layers of plasma membrane?
Myelin
78
What does myelin do?
Insulate axons: myelin prevents loss of electrical signal; speeds up conduction of nerve impulses
79
Myelination requires the glial cell to have?
wrapped its plasma membrane around the axon many times
80
A schwann cell myelinates a 1 mm-long segment of an
axon
| Migrates around the axon multiple times and multiple layers of the schwann cell plasma membrane surround the axon
81
What is the neurolemma?
The outer nucleated cytoplasmic layer of the schwann cell, which encloses the myelin sheath
82
Which axons have no myelin sheath and no neurolemma?
Unmyelinated axons
| Can be associated with schwann cells, but the axons simply lay in grooves on the surface of the schwann cell.
83
What inner portion successively encircles the axon, forming many layers that comprise the myelin sheath?
Schwann cell (neurolemmocyte)
84
What comes to reside in neurolemma, which is the outer nucleated cytoplasmic layer of the schwann cell?
The nucleus of the neurolemmocyte
85
What is the neurolemma?
- Outer layer of a myelinating schwann cell
- Contains the nucleus and virtually all the cytoplasm
- Not to the axolemma
- Found only around axons in the PNS
86
What are the Nodes of Ranvier?
- Only on nerve fibers supplied by potentially myelin-producing cells
- Gaps between myelinating cells
- Found in PNS and CNS
87
A nerve fiber consists of?
an axon plus myelin sheath (if present)
88
What surrounds the nerve fiber?
The endoneurium
89
What overlies the schwann cell?
Endoneurium
90
What are the schwann cells of the CNS?
Oligodendrocytes
91
Each process of a oligodendrocytes can form a?
Myelinated segement
- can myelinate several segments
- can participate in myelination of several axons
92
Why is a neurolemma not present in the CNS?
Because oligodendrocyte cell body and nucleus do not envelop the axon.
93
One oligodendrocyte can myelinate how many times?
Multiple
There is no neurolemma
There are nodes of Ranvier
94
A region of the brain predominantly filled with myelinated tract fibers, The appearance is due to the whitish color of myelin.
White matter
95
A region of the brain predominantly filled with neuronal cell bodies. There is little or no myelin in these areas, and the Nissl bodies impart gray color.
Gray matter
96
Nerve cells are highly adapted for using ________ potentials, and changes in _______ potentials, to initiate and transmit nerve impulses
Membrane potential
97
What are the two types of electrical signals neurons communicate with?
```
Action Potentials (nerve impulses)
Graded Potentials (localized)
```
98
What is for both short and long distance communication within the body? "all or none"
Action potentials
99
What neuronal signals are for short-distance communication only?
Graded potentials
100
What is the physiological role of graded potentials?
Is to affect (and effect) the generation of action potentials.
101
Both types of neuronal signals depend on two features of the plasma membrane of excitable cell, which are?
-Existence of a resting membrane potential
| _presence of specific ion channels
102
Voltage is measured across the __________, and is relative to the outside of the cell (cell's environment)
plasma membrane
103
Membrane Potential
| Potential means?
potential energy that can cause a flow of electrical current
- attractive force is the potential measure in volts
104
An electrical current is what?
The flow of electrons
| Current means flow of ions- sodium (Na+), potassium, calcium.
105
When current flows through a membrane charges are _____ across the membrane and potential changes
redistributed
106
What gives the cells the property of electrical excitability?
Ion channels
107
When ion channels are opn, specific ions are allowed to do what?
Move across the plasmalemma, down their electrochemical gradient
108
The flow of ions comprise a flow of electrical current that can change the ________.
membrane potential
109
Ion channels open and close due to the presence of?
Gates
110
A gate is the part of a channel protein that does what?
Opens or closes to allow or prevent the passage of ions
111
T or F
| All membrane channels have gates
F
112
Are leakage channels gated?
No, they randomly open and close
113
Between K+ and Na+ there are more specific leakage channels for? The resting membrane is more permeable to?
K+
| K+
114
Is the voltage difference measured across the plasma membrane when the neuron isn't signaling?
Resting membrane potential
Varies from cell to cell
115
Is the resting membrane potential polarized or unpolarized?
Polarized
116
All membrane potentials are reported as the potential of the
Inside of the membrane relative to the outside of the membrane
117
What is the resting membrane potential due to?
A small buildup of anions in the cytosol just inside the membrane.
Equal buildup of cations in the ECF just outside the membrane
118
The relative permeability of the resting membrane is 50 to 100 times more permeable to?
K+ than to Na+
| Cl- is in between
119
What is the membrane impermeable to?
Nearly all of the negatively charged intracellular molecules
120
Explain the steps of establishing the resting membrane potential
- K+ moves out of cell
- IC negatively charged ions cant get through membrane
- The interior of the membrane becomes negatively charged; the exterior becomes positively charged; net diffusion of K+ stops
-Na+ goes into cell but slower rate than K+ existing
A little Cl- leave the cell, interior of cell more negative
- net result= resting membrane potential
121
What produces graded potentials in response to stimuli?
Ligand-gated or mechanically gated ion channels
122
What means the size of the change in the membrane potential varies in proportion to the strength of the stimulus (all or none)?
Graded
123
What are local effects only of the graded potentials?
Channels open, current flows through the membrane and along the membrane, and travels only a short distance before diminishing to zero.
124
A graded potential can either do what to the membrane since the membrane is polarized?
Depolarize or hyperpolarize
125
A membrane becomes more polarized
Hyperpolarization
126
A membrane becomes less polarized (less negative or more positive)
Depolarization
127
The positive charges of the calcium ions alter the what of the channel protein?
Electrical state
Increasing the voltage level required to open the gate.
128
Calcium ion deficit in the extracellular fluids, what becomes activated by very little change of the membrane potential from its normal resting level?
Sodium channels
129
What becomes highly excitable, sometimes discharging repetitively without provocation, rather than remaining in the resting state?
Calcium ion deficit
130
Propagation depends on what?
Positive feedback
131
The movement of nerve impulses are called?
Propagation
132
Nerve impulses must travel from the ________ down the neuron to the axon _____.
Trigger zone
| Axon terminal
133
Step-by-step depolarization and repolarization of adjacent segments is termed?
Continuous conduction
134
This is a special mode of impulse propagation that occurs along myelinated axons
Saltatory conduction
135
Saltatory conduction happens on what type of axons?
Only myelinated
136
In saltatory conduction, voltage-gated channels are concentrated at the _______, with few regions where the myelin sheath covers the _______.
Nodes of Ranvier
| Axolemma
137
In saltatory conduction, electric current is carried by extracellular and intracellular ions from one node to the next.....?
the nodes depolarize and repolarize.
138
Saltatory or continuous, which one is faster?
Saltatory
| It is also more energy efficient, requiring less ATP to repolarize
139
What do neurons produce virtually all their ATP from?
Aerobic metabolism of glucose
140
Metabolism requires large amounts of oxygen, the nervous system requires?
High blood flow, and is consequently highly vascularized.
141
Most of the brains energy consumption goes into?
Sustaining the electric charges of neurons.
142
Who devotes more basal metabolism to the brain, vertebrates or primates?
Primates
143
The great the diameter of the axon, the _____ the conduction will be.
Faster
144
Describe the three different fibers of the effect of axon diameter.
```
A fibers
-large diameter
-myelinated
B fibers
-Medium fibers
-myelinated
C fibers
-small diamerter
-unmyelinated
```
145
What are the two mechanisms that enable stimuli of differing intensities to be registered as such?
Frequency of impulses
| Number of sensory neurons activated (recruited)
146
What are the characteristics of frequency of impulses?
- A light touch generates a low frequency of widely spaced nerve impulses
- A firm pressure causes nerve impulses to go down the axon closer together
147
What the characteristics of number of sensory neurons recruited?
- A light touch stimulates only a few pressure sensitive neurons
- A firm pressure stimulates more pressure sensitive neurons
148
T or F
| No action potential is generated by a subthreshold stimulus.
T
149
Several action potentials result from what kind of stimulus?
Suprathreshold
All have the same amplitude. This is perceived as a stronger stimulus
