Chapter 13- Neural Tissue Flashcards
1
Q
nervous system
A
coordinate all body systems
- accomplished by the transmission of signals
- body parts to CNS
- CNS to body parts
- Electrochemical signaling
2
Q
endocrine system
A
slower scale
-uses chemicals in the blood stream called hormones
3
Q
general makeup of NS
A
- many organs, each composed of several tissue
- connective tissue
- blood vessels
- neurons
- neuroglia
4
Q
2 groups of NS
A
CNS
-brain and spinal chord
PNS
-cranial and spinal nerves (ganglia)
5
Q
CNS makeup
A
brain and spinal chord
- covered by meninges (house fluid)
- starts as a hollow tube
- bathed in cerebrospinal fluid
- integration center
6
Q
PNS makeup
A
consists of cranial and spinal nerves that contain both sensory and motor fibers
-connects CNS to muscles, glands, and all receptors
-brings info to and from CNS
(only sensory OR motor neurons)
7
Q
PNS: 2 types
A
Afferent division= sensory
Efferent division= motor
–somatic (conscious control)
–autonomic (unconscious)
8
Q
Receptors
A
detect stimuli
9
Q
sensory
A
afferent PNS
10
Q
integrative
A
CNS
11
Q
motor
A
efferent PNS
12
Q
effector
A
muscle/gland
13
Q
Nervous tissue
A
neurons -structural and functional units -excitable -amitotic (unrepairable) Neuroglia cells -accessory cells -act like connective tissue
14
Q
3 major structures of neurons
A
soma
dendrites
axon
15
Q
soma
A
cell body
-mononucleate
16
Q
soma consists of
A
nissi bodies: ribosomes clusters, give gray color
axon hillock: connects soma to axon
perikaryon: region around the nucleus
neuronfibrils: cytoskeleton that extend into dendrites/axons; gives shape
17
Q
dendrites
A
- respond to neurotransmitters
- short, branched, unmyelinated
- specialized for contact with other neurons
- conducts impulses towards the cell body
18
Q
axon
A
- only one cell
- conducts nerve impulses away from soma
- can give off collaterals (branches at end)
- end in synaptic terminals
- produce neuraltransmitters
- may contact one of three things: another neuron, muscle fibers, gland
19
Q
myelin sheath
A
glial cells that may wrap around the axon
20
Q
axonal transport (axoplasmic flow)
A
movement of cellular materials (NOT signals) through axon
21
Q
anterograde
A
away form soma; neurotransmitters, organelles, nutrients
22
Q
retrograde
A
toward soma; degraded materials to be recycled and extracellular substances
23
Q
axoplasma
A
- cytoplasm of an axon
- consists of
- few organelles
- cytoskeletal proteins
- -form cytoskeleton
- -maintain shape
- generate axonal transport
24
Q
axolemma
A
-plasma membrane of an axon consists of: -collaterals: side branches -telodendria: terminal extensions -synaptic terminal: contains synaptic vesicles; where neuron contacts pstsynaptic cell
25
structural classification of neurons
anaxonic
bipolar
unipolar
multipolar
26
anaxonic
small neurons
axons can not be distinguished from dendrites
-CNS, especially interneurons that coordinate special senses
no axon
27
bipolar
- several small dendrites converge onto one (one really long dendrite, looks like axon)
- dendrite and axon separated by soma
- unmyelinated
- sensory neurons of special sensory organs
28
unipolar
- pseuod-unipolar
- several small dendrites converge onto one large one
- dendrite and axon continuous
- usually myelinated
- majority of sensory neurons in PNS
29
multipolar
- many dendrites extend from soma
- long axon
- myelinated
- majority of motor neurons in PNS
- spinal interneurons in CNS
30
Afferent Neuons
Have sensory function
- cell body usually are outside CNS
- have receptor ends on dendrites or are associated with receptor cells in sense organs
- carry impulses from peripheral body parts to brain or spinal cord
31
afferent neruon receptors
exteroceptors: touch, temperature, pressure, light, chemicals
proprioceptors: monitor muscle and skeleton position
interoceptors: monitor internal systems (digestion, respiration, urinary)
32
Interneurons
- only in CNS
- classified based on effects
- -excitatory
- -inhibitory
- most abundant
- -link 2 or more neurons
33
efferent neurons
have motor function
- cell body usually are inside CNS
- carry impulses from the brain or spinal cord to peripheral body parts
34
somatic efferent neurons
controls skeletal muscle
35
autonomic/visceral efferent neurons
smooth muscle/glands
36
neuroglial cells in PNS
satellite
| schwan cell
37
neuroglial cells in CNS
astrocytes
oligodendrocytes
ependymal cells
microglia
38
Astrocytes
```
largest and most common
star shaped
functions:
-structure and repair
-metabolism
-regulate ions and nutrition
-guide neurons to targets
-form blood-brain barrier
```
39
oligodendrocytes
like astrocytes but smaller
functions
-form myelin in CNS
-sequester debris
40
Microglia
-smallest and least common
-derived from myeloid cells
functions:
-help support neurons
-phagocytosis
-increase in number during injury or disease
41
ependymal
-columnar/cuboidal
-microvilli on luminal surface
-joined by gap junctions
functions:
-help produce cerebrospinal fluid
-form porous layer
-monitor CSF composition
42
satellite
associated with soma
assist with exchange of nutrients
isolates neuron from extraneous stimuli
43
schwann cells
produce myelin in PNS
encloses axons of longer peripheral nerves
functions:
-support neurons
-prevent contact
-myelinate large PNS axons (myelin sheath)
44
unmyelinated axons
- appear gray
- many axons associate with a single schwann cell
- CNS: no glial cells
45
myelinated
- appear white
- CNS: oligodendrocytes myelinate part of several axons
- PNS: schwann cell myelinates part of one axon
46
myelin structure
- myelin
- neurilemma
- nodes of ranvier
47
myelin
plasma membrane of schwann cell wrapped around axon
48
neurilemma
part of schwann cell that contains cytoplasm
49
nodes of ranvier
gaps in myelin sheath
50
myelination process
starts at week 14 and completed by age 2-3 years
51
myelin functions
isolate axons
| increase rate of action potential
52
regeneration of nerve fibers: PNS
can regenerate a fraction of axons
- schwann cells participate in process
- called wallerian degeneration
53
wallerian degeneration
regeneration of PNS axons
54
steps of nerve regeneration
1. injury separates axon from cell body
- distal portion of axon will deteriorate along with myelin sheath
2. macrophages clean up
- some schwann cells remain
- get thin basement membrane and layer of CT around schwann cells
3. forms hollow tube leading to original connection of axon
- proximal end sprouts
- sprout may grow into tube
4. remaining schwann cells produce new myelin around growing axon
- new axon grows 3-4mm/day
55
repair in CNS
more limited
- degeneration occurs after injury
- oligodendrocytes do not proliferate
- proximal end sprouts but has no tube to follow
- astrocytes produce scar tissue and chemicals blocking regrowth
- generally results in paralysis
56
irritability
ability to respond to stimuli
57
excitability
ability to transport and impulse
58
action potential
an electrical impulse changing the permeability of a membrane
59
nerve impulse
AP moving down an axon
- impulse travels faster when:
- -axon is myelinated
- -has a larger diameter
60
synapse characteristics
```
functions as control/transmission point
site of communication between
-sensory structure and neuron
-neuron and effector
-2 neurons
-any two cells with gap junctions
```
61
electrical synapse
- gap junctions cause the exchange of charged ions between two cells
- communicating charge through ions
62
chemical synapse: definition
chemicals are released by one cell and travel to another
63
chemical synapses: about
- synaptic vesicles house neurotransmitter
- only exist in the presynaptic cell
- release neurotransmitter into the synaptic cleft
- receptors on post-synaptic membrane register the neurotransmitter
- proliferates AP from one cell to the next
- communication in one direction only
- only axons have synaptic vesicles
64
steps at chemical synapse
1. AP reaches synaptic knob of presynaptic neuron
2. neurotransmitter released
3. neurotransmitter crosses cleft and binds to receptors in post-synaptic membrane
- change in permeability results, can be excitatory or inhibitory
4. neurotransmitter is then removed from synaptic cleft
- permeability returns to original state
65
neuronal pools
- receive impulses from afferent fibers (input)
- impulses carried away on efferent fibers (output)
- afferent fibers can branch manny times as they enter a pool
66
types of neuronal pools
```
convergence
divergence
serial processing
parallel processing
reverberation
```
67
serial processing
one neuron to another in series
68
divergence
when impulse leaves a pool, it may spread into several output fibers
-allows impulse to be amplified
69
convergence
single nerve in pool may receive impulses from 2 or more incoming fibers
- if lead to same nerve they are said to converge
- allows summation of impulses from different sources
70
parallel processing
processing information from several neurons at once
71
reverbration
positive feedback continues activity of circuit
- enhances signal so happens repeatedly
- promote a behavior, keep responding same way
72
facilitation: threshold
- one neuron may receive either excitatory and inhibitory stimuli from multiple neurons
- the net effect of all this input results in a net charge. if this charge is positive enough it will result in AP
- this point where AP can be produced is known as threshold
73
facilitaiton: facilitated
if a neuron is excited, but still below threshold:
-no impulse, but nerve is more excitable to next impulse
-nerve is said to be facilitated
whole system allows for multiple sources to manage nervous system
74
CNS structures
nuclei
center
tracts
75
nuclei
collection of neuron cell bodies
76
center
collection of neuron cell bodies working together
77
tracts
bundles of axons
78
PNS structures
ganglia
| nerves
79
ganglia
collection of neuron cell bodies
80
nerves
bundles of axons
