Chapter 12: Nervous Tissue (Part 1) Flashcards
1
Q
What systems maintain the internal coordination? (2)
A
endocrine & nervous system
2
Q
Which system communicates using chemical messengers secreted into the blood?
A
endocrine
3
Q
Which system employs electrical & chemical means to send messages?
A
nervous
4
Q
3 basic tasks of the nervous system
A
- Receive info about changes in the body & transmit info to spinal cord & brain
- Brain & spinal cord process the info and determine response
- Brain & spinal cord issue commands to muscles & glands to carry out response
5
Q
What are the 2 subdivisions of the nervous system?
A
- central nervous system (CNS)
- peripheral nervous system (PNS)
6
Q
What is included in the CNS?
A
spinal cord & brain
7
Q
What is the PNS composed of?
A
ganglia & nerves
8
Q
nerves
A
a bundle of nerve fibers wrapped in fibrous connective tissue
9
Q
ganglion
A
a knotlike swelling in a nerve where neuron cell bodies are concentrated
10
Q
What are the 2 subdivisions of the PNS?
A
sensory & motor
11
Q
sensory afferent division
A
carries sensory signals from various receptors to the CNS
12
Q
somatic sensory division
A
carries signals from receptors in the skin, muscles, bones, & joints
13
Q
visceral sensory division
A
carries signals from the viscera of the thoracic and abdominal cavities
14
Q
afferent
A
towards the CNS
15
Q
efferent
A
away from the CNS
16
Q
motor efferent division
A
carries signals from the CNS to gland and muscle cells that carry out body responses
17
Q
effectors
A
cells and organs that respond to commands from CNS
18
Q
somatic motor division
A
carries signals to skeletal muscles
19
Q
visceral motor division is also known as_____
A
autonomic nervous system
involuntary that carries signals to glands, smooth muscle
20
Q
visceral motor division is divided into
A
sympathetic & parasympathetic system
21
Q
sympathetic division
A
“fight or flight” response
tends to arouse body for action
22
Q
parasympathetic division
A
“rest or digest”
tends to have calming effect
23
Q
excitability
A
respond to environmental changes called stimuli
24
Q
properties of neurons (3)
A
- excitability
- conductivity
- secretion
25
conductivity
neurons respond to stimuli by producing electrical signals
26
secretion
when electrical signal reaches end of nerve fiber and a chemical is secreted
27
______->________->________
afferent; interneurons; efferent
28
interneurons (3)
- lie entirely within the CNS
- carry out the integration function of the CNS
- 90% of neurons
29
integrative function
ability to process, store, and retrieve info to make decisions
30
soma (4)
- the control center of the neuron
- made of microtubules & neurofibrils
- no centrioles = no cell division
- inclusions
31
dendrites
vast number of branches that come from thick branches of the soma that receive signals from other neurons
32
axon?=______
nerve fiber
| originates from mound on one side of the soma
33
branches of the axon?
axon collaterals
34
extensive complex of fine branches?
terminal arborization
35
axoplasm
cytoplasm of axon
36
axolemma
plasma membrane of axon
37
bipolar neuron
one axon and one dendrite
38
unipolar neuron
single process leading away from the soma
39
anaxonic neuron
many dendrites but no axon
40
axonal transport
two way passage of proteins, organelles, and other material along an axon
41
What are the 2 types of axonal transport? describe?
anterograde: movement down the axon from soma
retrograde: movement up the axon toward the soma
42
What helps guide materials along axon
microtubules
43
Motor proteins used to carry material along microtubules?
kinesin(anterograde) & dynein(retrograde)
44
fast anterograde vs fast retrograde transport
anterograde: for small particles, organelles, enzymes, synaptic vesicles (immediate)
retrograde: for recycled materials and pathogens
45
slow axonal transport (2)
- always anterograde
| - damaged nerve fibers regenerate at a speed governed by this
46
neuroglia (4)
- outnumber neurons 50 to 1
- support & protect the neurons
- bind neurons together & form framework for nervous tissue
- allow signals to move fast
47
Neuroglial cells in CNS? (4)
- oligodendrocytes
- astrocytes
- ependymal cells
- microglia
48
Neuroglial cells in PNS? (2)
- schwann cells
| - satellites cells
49
oligodendrocytes
form myelin sheath in CNS
50
ependymal cells
secrete & circulates cerebrospinal fluid
51
microglia
- immune system
| - small macrophages formed WBC (monocytes)
52
astrocytes (2)
- busy (multiple functions)
| - most abundant glial cell in CNS
53
functions of astrocytes (5)
- form supportive framework
- have perivascular feet to form blood brain barrier
- convert blood glu to lactate (generate energy)
- promote nerve growth factors
- regulate chemical composition (absorb excess neurotransmitter)
54
astrocytosis
when neuron is damaged, astrocytes form hardened scar tissue & fill space formerly occupied by the neuron
55
compartmentalized rough ER in soma
nissal bodies
56
schwann cells
produce myelin sheath in PNS
57
satellite cells (2)
- surround the neurosomas in ganglia
| - provide electrical insulation around the soma
58
tumors
masses of rapidly dividing cells
59
brain tumors arise from ____
meninges & metastasis from nonneuronal tumors
60
gliomas (3)
- grow rapidly & highly malignant
- blood brain barrier decreases effectiveness of chemotherapy
- treatment with surgery or radiation
61
_______- can regenerate unlike neurons
neuroglia
62
myelin sheath
an insulating layer around the nerve fiber; consists of 20% protein & 80% lipid
63
The myelin sheath is created by the ______ in the CNS and the ______ in the PNS
oligodendrocytes; Schwann cells
64
myelination
production of the myelin sheath begins at week 14 of fetal development
65
How is the myelin sheath added to nerve fibers in the PNS?
by schwann cells repeatedly spiraling a single nerve fiber; no cytoplasm between the membrane
66
neurilemma (2)
- thick outermost coil of myelin sheath
| - contains nucleus & most of cytoplasm
67
endoneurium
external to the neurilemma made of a fibrous connective tissue
68
How is the myelin sheath added to nerve fiber in the CNS?
oligodendrocytes reach out to myelinate several nerve fibers in its immediate vicinity
69
T or F nerve fibers in the CNS have neurilemma or endoneurium
FALSE
70
node of ranvier
gap between segments of myelin sheath
71
internodes
myelin-covered segments from one gap to the next
72
initial segment
short section of nerve fiber between the axon hillock and the first glial cell
73
trigger zone
the axon hillock & the initial segment (play a role in initiating a nerve signal)
74
multiple sclerosis
- oligodendrocytes & myelin sheath in the CNS deteriorate
- myelin sheath is hardened by scar tissue
- nerve conduction disrupted
- fatal 25-30 years after diagnosis
75
tay-sachs disease
a hereditary disorder of infants with an abnormal accumulation of glycolipid called ganglioside(GM2) in the myelin sheath
76
mesaxon
neurilemma wrapping of unmyelinated nerve fibers
77
The speed at which a nerve signal travels along a nerve fiber depends on what 2 factors?
- diameter of fiber
| - presence or absence of myelin
78
Where is the signal conduction occur in a nerve fiber
along the surface
79
Which signal conduction is the fastest?
large & myelinated
80
denervation atrophy
due to loss of nerve contact by damaged nerve
81
When can regeneration of a damaged peripheral fiber occur?
- its soma is intact
| - at least some of the neurilemma remains
82
axon hillock contains ___ & ____
trigger zone & initial segment
83
When cant fibers be regenerated?
if they are distal to the injury because macrophages clean up tissue debris
84
During regeneration of a never fiber what happens?
soma swells, ER break up, and the nucleus moves off center
85
regeneration tube is produced by what? (3)
schwann cells
basal lamina
neurilemma near injury
86
Can regeneration of damaged fibers in the CNS occur?
NO
87
nerve growth factor
a protein secreted by a gland, muscle, & glial cell and picked up by the axon terminals of the neuron that prevents cell apoptosis
88
resting membrane potential
-70mV (negative means more negatively charge particles on the inside)
charge difference across the plasma membrane
89
What maintains the resting membrane potential?
Na/K pump (3 Na for 2 K)
90
What is the greatest influence on the RMP?
K because the membrane is more permeable to it & its more concentrated in the ICF
91
_____ is concentrated in the ICF & _____ is concentrated in the ECF when a membrane is at resting membrane potential?
K inside and Na outside
92
local potentials
(short range change)
disturbance in membrane potential when a neuron is stimulated; when a short current is produced by Na diffusing in that travels toward the cell trigger zone
93
process of neuron response (4)
1. begins at the dendrites
2. spreads through the soma
3. travels down the axon
4. ends at the synaptic knobs
94
what causes a membrane to depolarize?
when a neuron is stimulated by chemical, light or heat that causes Na channels to open and Na rushes in which results in the cell becoming less negative
95
action potential
more dramatic change produced by a voltage regulated ion gates in the plasma membrane; can not be regenerated by a soma
96
threshold
- 55mV
- critical voltage to which local potential must rise to open the voltage-regulated gates
- once reached a neuron fires and produces an action potential
97
spike (2)
when more and more Na+ channels open in a positive feedback cycle at the trigger zone that creates a rapid rise in the membrane voltage
-often called an action potential
98
hyperpolarization
the effect of leaving K+ gates open longer than Na+
99
What is affected during an action potential?
a thin layer of the cytoplasm next to cell membrane
100
action potential vs. local potential
action: all or nothing; nondecremential (do not get weaker with distance); irreversible
local: graded (vary in magnitude w/ stimulus strength);decremential ;reversible; either excitatory or inhibitory
