mod 3 - NS 1 Flashcards
(84 cards)
1
Q
nervous system function
A
coordinates voluntary & involuntary actions & transmits signals to & from diff. parts of body
2
Q
NS has how many parts
A
2 parts -
1. CNS (central nervous system): brain & spinal cord
2. Peripheral nervous system (PNS): nervous tissue outside brain & SC
3
Q
PNS is divided how
A
2 parts -
- sensory division (afferent): brings info towards CNS
- efferent division of PNS: takes info away from CNS
4
Q
efferent division of PNS divided how
A
- autonomic neurons: visceral, cardiac muscle, etc
- sympathetic & parasympatheic - somatic motor neurons
5
Q
3rd branch of PNS
A
enteric nervous system
- can act autonomously or can be controlled by the CNS thru the autonomic division of the PNS
- ex: digestive tract
6
Q
organization of NS summary
A
- CNS: brain & spinal cord
- PNS: nerve tissue outside CNS - cranial nerves & branches, spinal nerves & branches, ganglia, plexuses & sensory receptors
- subdivisions: afferent & efferent
3.? enteric division
7
Q
afferent division & efferent divisions
A
afferent:
- somatic sensory
- visceral
- special
efferent:
- autonomic: sympathetic & parasympathetic
8
Q
2 main types of cells in NS
A
neurons & glia
9
Q
define neurons
A
the basic signaling units of the NS
10
Q
glia function
A
support & signalling cells
11
Q
neuron functions
A
carry electrical signals
- communication in body
12
Q
define soma
A
cell body: control center of neuron
- processes extend outward: dendrites & axons
13
Q
dendrites function
A
input area of neuron
- receive incoming signals from neighbouring cells
-
14
Q
axon function
A
output area of neuron
- carry outgoing signals from integrating center to target cells
15
Q
presynaptic terminals
A
contain transmitting elements (chemical transmitting elements)
- come into close contact with other dendrites
16
Q
different neuron structures
A
- pseudounipolar
- bipolar
- anaxonic
- multipolar
17
Q
pseudounipolar neuron
A
single process called an axon
- dendrites fused w axon
- most in body
- can get v long
18
Q
bipolar neuron
A
2 equal fibers that extend off the central cell body
19
Q
anaxonic CNS
A
interneurons have no apparent axons
- help form networks
20
Q
multipolar neurons
A
- interneurons highly branches
- lack long extensions
- 5-7 dendrites
- each dendrite branches 4-6x
21
Q
interneurons
A
complex branching neurons that facilitate communication between neurons
22
Q
nerve vs neurons
A
nerve = bundle for neurons (esp. peripheral neurons)
23
Q
axon are specialized to what
A
specialized to convert electrical & electrical signals that need a variety of different types of proteins
24
Q
axons lack what
A
axons lack ribosomes & ER needed for protein production
- proteins created in cell body
- then transported down to axon
25
fast axonal transport
membrane bound proteins & organelles (vesicles or mitochondria)
- anterograde: cell body (soma) to axon term., 400 mm/day
- retrograde: axon term. to cell body, 200 mm/day
26
slow axonal transport
moves cytoplasmic proteins (enzymes) & cytoskeleton proteins
- anterograde, 8mm/day
- may be slower due to frequents period of stoppage
27
motor proteins (fast axonal proteins)
1. kinesin
2. dynein
28
kinesin vs dynesin
kinesins: anterograde - cell body to periphery
dynesins: retrograde
- both use atp hydrolysis = drive movement of proteins to “walk” along filaments
29
kinesins follow what
kinesins follow a positive charge located at the presynaptic terminal
30
dyneins follow what
dyneins follow a negative charge at the cell body
31
kinesin & dynein walk along what
walk along microtubule
32
define synapse
point of connection between 2 neurons or between a neuron & another cell type
33
synaptic cleft
space that contains extracellular matrix (proteins & carbs) that hold pre & post synaptic cells close together
34
2 types of synapses
1. chemical - majority of synapses
2. electrical
35
electrical synapses contain what & allow for what
electrical synapses contain GAP junctions channels & allow for passage of ions
- much faster than chemical
- move directly from 1 cell to another
36
why is chemical synapse slower
long process:
- release of chemical
- diffuse across
- create a signal
37
establishing synapses step 1
depends on chem. signals
- axons of embryonic nerve cells contains growth cones that sense & grow towards a specific chem. signal
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establishing synapses step 2
growth does depend on growth factors
- molecules in extracellular matrix & membrane proteins
39
establishing synapses step 3
once reaches a target cell, a synapse forms
- synapses must be maintains through repeated use (“use it or lose it”)
40
glia to neuron ratio
1-4 glia to 1 neuron
41
glia functions
communicate w neurons
provide imp. biochemical support
42
CNS glia cells
1. ependymal cells
2. astrocytes
3. microglia (modified immune cells)
4. oligodendrocytes
43
PNS glia cells
1. schwann cells
2. satellite cells
44
oligodendrocytes (CNS) & schwann cells (PNS) functions
myelin forming glia
- substance composed of multiple layers of phospholipid membrane wrapped around an axon
45
oligodendrocytes (cns) VS schwann cells (pns)
oligodendrocytes (cns): wraps around axons off multiple neurons up to 50x
- highly branching
schwann cells (pns): 1 cell wraps a segment of 1 neuron
46
myelin functions
- structural stability
- insulation around axon to speak up electrical signals (saltatory conduction)
- supply trophic factors
47
demyelination disease
multiple sclerosis (MS): demyelination in brain & spinal cord (CNS)
- improper signalling in neurons
48
MS cause/mechanics
autoimmune disease
- immune cells attack myelin
- reduced ability of myelin produced cells (oligodendrocytes are reduced)
- genetic & enviro. factors
49
satellite glial cells
exist in ganglia (bundles of cell bodies) in PNS
- form a supportive capsule around cell bodies of neurons (sensory & autonomic)
50
astrocytes (CNS)
majority of glial cells = highly branched, 20-40% cells in any regions are astrocytes
-star shaped
51
astrocytes form what
astrocytes form a functional network
- communities between each other thru calcium waves
52
astrocytes functions
1. take up & release chems. at synapses
2. provide neurons w substrates for ATP prod. (e.g. capable to storing nitrogen)
3. help maintain homeostasis in ECF (take up K+ & H2O)
4. surround vesicle = part of blood brain barrier, influence vascular dynamics
53
if the membrane potential of a cell changes from -70mV to +10mV, the cell is:
depolarizing
- membrane pot. becomes more positive = depolarizing
54
define microglia (CNS)
specialized immune cells in CNS
- protect & preserve neurons
55
how do microglia work/mechanism
- star shaped cells
- overlapping network, sit in 1 area
- feel around for pathogen/damage
- sense damage & phagocytosis
- release inflammatory mediators = recruits other microglia
- when activated, changes shape
56
chronic state of damage & constantly activated microglia
microglia that are constantly active can be detrimental
- affects the nearby neurons, damages them —> creates debris, & creates a cycle
ex: alzheimer’s, ALS, neuropathic pain
57
ependymal cells (CNS)
line fluid filled a cavities in brain & SC
- help to move & produce cerebrospinal fluid
58
ependymal cells (CNS) functions
1. help circulate cerebral spinal fluid (which fills cavities) & surrounds brain & CS —> cushion
2. chemical stability
3. clearing wastes
59
CNS neuron injury
CNS repair less likely to occur naturally —> glia seal off & form scar tissues (prevents reformation of synapses)
60
Peripheral neuron injury
depends on where the injury is:
- cell body damage: cell dies
- axon damage: portion connected to cell body survives (proximal axon), distal portion degenerates (lacks organelles, no proteins from cell body)
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schwann cells regeneration tube
- schwann cells if not too damaged, begin to divide in distal area —> create glia in regeneration tube
- sensory neurons (small neurons) - 1mm/day
- motor neurons (bigger neurons) - 5 mm/day
62
why are neurons & muscle cells “excitable”
their ability to propagate electrical signals over long distances in response to a stimulus
63
what created electrical signals
ion movements in & out of cell
- change in permeability to ions = alters membrane potential
64
depolarization
membrane potential becomes more positive
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hyperpolarization
membrane potential becomes more negative
66
T/F: a significant change in membrane potential indicates a change in concentration gradient
F: v few ions need to move to alter membrane potential
- concentration gradient for ions remain pretty constant during changes in membrane potential
67
what changes membrane potential & creates electrical signals
gated channels
- opening & closing ion channels in membrane —> alters ion permeability
- new open channels can be added/removed to alter permeability (slow)
68
5 major types of ion channels
1. Na+
2. K+
3. Ca2+
4. Cl-
5. mono alert cation channels (allows Na+ & K+ to pass)
69
conductance
the ease with which an ion can flow through a channel
- varies w the gating state of channel
- channel protein isoform
70
types of gated channels
1. mechanically gated channels
2. chemically gated ion channels
3. voltage gated channels
71
mechanically gated channels
open in response to physical forces (pressure or stretch)
- found in sensory neurons
72
chemically gated ion channels
respond to ligands (extracellular neurotransmitters, neuromodulators, intracellular signalling molecules)
- in neurons
73
voltage gated channels
respond to changes in cells membrane potential
74
variation in gated channels
- voltage for channel opening
- speed @ which channels open or close
- channels that open during depolarization, close during depolarization
- some channels spontaneously inactive
75
channelopathies
diseases where mutations in dna responsible for creating ion channel
- incorrect amino acid
- disrupt how ions normally flow thru ion channel
- alter channel activation
- alter channel inactivation
ex: cystic fibrosis, muscle disorders etc
76
current
flow of electrical charge carried by an ion is the ion’s current
77
current flow follows ?
ohms law
- current flow is directly proportional to the electrical potential difference between two points & inversely proportional to resistance
78
2 sources of resistance in a cell
1. membrane resistance (Rm): resistance of phospholipid bilayer
2. internal resistance of the cytoplasm (Ri): cytoplasmic composition & size of the cell
- resistance determines how far current will flow in a cell before energy is dissipates
79
2 types of electrical signals
1. graded potentials
2. action potentials
80
graded potentials
- variable strength signals
- short distances
- lose strength as they travel
- either depolarizing or hyperpolarizing
81
actions potentials
- v brief
- large depolarizations
- travel long distances thru a neuron w/o losing strength
- rapid signals over long distances
82
graded potentials regions
- produced in dendrites, in response to presynaptic neurons (info coming in)
- travels thru cell body towards axon
- if depolarization is large enough —> leads to actions potential
83
why are graded potentials considered graded
amplitude (size) can change depending on the strength of stimulus & can vary
- decrease in strength as they spread out from the point of origin
- generated by chemical gated ion channels or closure of leak channels (CNS & efferent neurons)
84
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