Neural Tissue (ch12) Flashcards
1
Q
Central Nervous System
A
brain and spinal cord
2
Q
Peripheral Nervous tisse
A
neural tissue outside the CNS
3
Q
Neural tissue cells
A
Neurons and Neuroglia
4
Q
Neurons
A
unable to divide, send a receive signals
5
Q
Neuroglia
A
support, nourish and protect neurons, maintains interstitial fluid the surrounds neurons, maintaiin regeneration capabilities
6
Q
we have lots of neurons at _______
A
birth
7
Q
neuron cytoskeleton includes
A
intermediate filament and microtubules
8
Q
slow transport
A
1-5mm/day, moves material in one direction only
9
Q
fast transport
A
200-400mm/day, moves material by way of motor proteins, flow can go in both directions
10
Q
forward movement
A
anterograde
11
Q
backward movement
A
retrograde
12
Q
which cells makes up about half of the volume of cells of CNS
A
neuroglia cells
13
Q
which cell can multiply in times of injury or illness to fill space formerly occupied by neurons
A
Neuroglia
14
Q
Astrocytes
A
- produce scar tissue
- largest and most numerous neuroglia
- connects with capillaries
- helps surround blood vessels
15
Q
function of astrocytes
A
- create blood-brain barrier
- transfer nutrients between capillaries and neurons
- in embryo = help regulate growth and migration
- maintain interstitial fluid
16
Q
ependymal cells
A
- cuboid or columnar cells
- produce cerebrospinal fluid
- long extensions
17
Q
microglial cells
A
- small cells with slender projections
- immune cell
- function as phagocyte
18
Q
oligodendrocytes
A
- responsible for forming & maintaining myelin sheath around axons
- around 15-20 flat processes (extend to axons)
- absent neurolemma, limits regrowth after injury
19
Q
schwann cells
A
- form and maintain myelin sheath around axon
- neurolemma permits regeneration of axons following injury
20
Q
satellite cell
A
- surrounds bodies of neurons & peripheral nerves
- regulate exchange of material between cells
21
Q
which nervous tissue has a possibility of repair?
A
PNS if cell body is intact
22
Q
_______ cannot grow if gaps are _______ or ______
A
Axons, too large, filled with collagen fibers
23
Q
which nervous tissue has little to no repair
A
CNS - because of rapid formation of scar tissue
24
Q
overall the body is ___________
A
electrically neutral
25
membrane potential is established by
chemical disequilibrium between ICF and ECF
26
resting membrane potential for cells in the body is
-5mV- -100mV
27
what creates membrane potential
1. unequal distribution of ions across plasma membrane
2. most intracellular anions
3. electrogenic nature of Na+ and K+
28
Nernst equation
looks at 1 ion and describes membrane potential
29
Goldman-Hodgkins-Krats equation
predicts membrane potential of all ions that can cross membrane potential
30
how is resting membrane potential altered
changing membrane ion permeability
31
channels that open is response to depolarization will only close when cell ______
repolarizes
32
channels may spontaneously ______
inactivate with continual stimulus
33
what are the gated channels
- ligand-gated channel
- mechanically-gated channel
- voltage-gated channel
34
what happens to the cell when the membrane potential becomes less negative than the resting potential
the cell depolarizes
35
what happens to the cell if the membrane potential becomes more negative
the cell hyperpolarizes
36
Recovery from hyperpolarization is known as what
repolarization
37
graded potentials
- take place in dendrite and cell of body neurons
38
action potentials
circulate along the axon through voltage-gated channels
39
why are graded potentials decremental
- they take place in the dendrites and cell body of neuron
- signal strength depends of the number of open channels
- signal loses strength due to: current leak and cytoplasmic resistance
40
trigger zone at axon hillock contains high concentration of what
voltage-gated channels
41
how many gates does voltage-gated channels have?
2
- activation gate
- inactivation gate
42
activation gate
- fast
- first to respond
- influx of Na depolarizes membrane
43
inactivation gate
- .5msec delay
- depolarization stops
44
repolarization phase (AP)
- Na+ channels reset
- membrane becomes permeable to K+
- delay in closing hyperpolarizes membrane
45
hyperpolarization phase
- some but not all channels have a reset
- K+ channels are slowly closing
- natural permeability to Na+ and K+ allow membrane to return to resting potential
46
absolute refractory period
-typically 1-2 msec
- time required for Na+ channels to resent to resting position
47
relative refractory period
- may last as long as 15 msec
- stronger than normal graded potential required to reopen Na+ channels
48
two methods of propagation
continuous propagation & saltatory propagation
49
saltatory propagation
- myelin sheath prevents Na+. and K+ from leaving cell
- allow action potential to leap from node to node
- myelinated axons
50
continuous propagation
unmyelinated axons
51
Demyelinating diseases
- multiple sclerosis
- reduces or block conduction
52
factors that affect the speed of propagation
1. amount of myelination
2. axon diameter
3. temperature
53
hypokalemia
low K+ concentration
54
hyperkalemia
high K+ concentration
55
hyperpolarized cell
- harder to reach threshold
- trouble activating muscle
56
depolarized cell
- easier to reach threshold
- muscle spasm
57
hyponatremia
low Na+
58
hypernatremia
high Na+
59
synapses communication occurs between
- two neurons (interneural synapse)
- neuron and an effector cell (neuromuscular or neuroglandular)
60
electrical synapse
- pass electrical signals through gap junctions
- signal can be bi-directional
- allows for fast communication
- found in the CNS as well as in cardiac and smooth muscle
61
chemical synapse
- use neurocrine molecules to transmit signal
- chemicals cross synaptic cleft and bind onto receptor
62
neurotransmitters
- direct affect on signal post-synaptic membrane
63
neuromodulators
- diffuse away from synaptic cleft to influence many other neurons
64
neurohormone
- diffuse into blood and behave as a hormone
65
inonotropic receptors
- binding sit and ion channel
- mediate rapid responses
- how most neurotransmitters function
- specific to ion
66
matabotropic receptors
- G-protein mediated receptors
- mediate slower responses
- how most neuromodulators function
67
types of chloinergic receptors
- nicotinic receptors
- muscarinic receptors
68
nicotinic receptors
- produces EPSP
69
muscarinic receptors
- G-protein coupled receptors
- Mostly produces IPSP
70
Convergent circuit
- several presynaptic neurons influence one postsynaptic neurons
71
diverging circuit
- one presynaptic neurons influence several postsynaptic neurons
72
reverberating circuit
- impulses are ultimately sent back to the original neuron
- ex) brainstem
73
parallel after discharge circuit
one presynaptic neuron stimulates a group of neurons which synapse on a common neuron
