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Physiology 190 > Neurophysiology (1, 2) > Flashcards

Neurophysiology (1, 2) Flashcards

1
Q

How much of our body is our nervous system?

A

3%

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2
Q

What does the NS do?

A

DETECTS changes that impact the body, then works with the endocrine system to RESPOND

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3
Q

What are the 3 fundamental steps of the NS…

A
  1. (PNS) DETECTION - sensory function

> > afferent&raquo_space;

  1. (CNS) INTERPRETATION (analyze/store) - integration function

> > efferent&raquo_space;

  1. (PNS) REACTION - motor function
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4
Q

What do we base the classification of neurons on?

A

The electrophysiological properties and the DIRECTION in which the AP is conveyed.

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5
Q

What are the two components of the CNS?

A

The Brain&raquo_space; integrates sensory information and coordinates body

The SC&raquo_space; pathway for signals and involved in reflexes

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6
Q

What are the two components of the PNS?

A

Autonomic NS&raquo_space; lungs, heart, involuntary unconscious movement;

Somatic NS&raquo_space; skeletal system, conscious movement; consists of afferent and efferent neurons

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7
Q

What are the three components of the ANS?

A

Sympathetic NS&raquo_space; Fight or flight!

Parasympathetic NS&raquo_space; Rest and Digest!

Enteric NS&raquo_space; involuntary controls of digestive organs; operates mostly in GI tract, and in combination with ANS

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8
Q

The brain of the gut is

A

The enteric NS; is functionally independent

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9
Q

Define neuron

A

specialized cells that transmit information

  • respond to stimuli
  • conduct impulses
  • release chemical regulators/ NT’s
  • are amitotic and hypoxic sensitive
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10
Q

Define axon terminal

A

= telodendria

  • highly branched
  • interact with dendritic trees
  • some have bulb shaped structures
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11
Q

What are the three structural classifications of neurons?

A
  1. multipolar: large cell body, several short dendrites and a single long axon
  2. bipolar: one main dendrite, one axon
  3. Unipolar: dendrites and axon are fused together and emerge from cell body as a continuous process
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12
Q

Define synapse

A

site of communication

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13
Q

Define synaptic cleft

A

space between pre- and post- synaptic cells

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14
Q

define synaptic vesicles - what do they do?

A

Pouches which store and release NT’s into synapse

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15
Q

How do neurons communicate?

A

Through action potentials&raquo_space; neurons are electrically excitable

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16
Q

Distinguish between graded potentials and action potentials

A

graded potentials: are small deviations in membrane potential; cover short distances; occur mainly in dendrites and cell bodies
APs: cover long distances, can be muscle(contraction) or nerve(impulse) AP;

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17
Q

Action potentials depend on two things…

A
  1. RMP: resting membrane potential = electrical charge across the membrane “the potential difference”
  2. ION CHANNELS: ions move across the membrane&raquo_space; changes membrane potential
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18
Q

What is the RMP?

A

RMP: means that the outside of the cell is positive, and inside is negative

= -70mv inside cell

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19
Q

What are the three factors influencing RMP?

A
  1. unequal distribution of ions in and out (cyotosol, ECF) of cell
    > in ECF: Na and Cl
    > in cell: K, amino acids and P

An increase in K leaky channels leads to more K out of cell compared to incoming Na resulting IN THIS NEGATIVE RMP

  1. inability of negative ions to LEAVE cell
    > most cannot diffuse because attached to non-diffusing molecules

This results in a -70 RMP

3. Na/K pump
> active transport 
- Na is pumped in 
- K is pumped out
 >> there are 3 sodium for every 2 potassium

LEADING TO A NEGATIVE RMP

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20
Q

What are 6 different types of ion channels?

A
  1. Resting K channel
  2. Voltage gated channel
  3. Ligand gated channel (extracellular molecule)
  4. signal gated channel (intracellular molecule)
  5. leak channels open/close randomly
  6. mechanically gated channel
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21
Q

What are the THREE MAIN ion channels?

A
  1. Voltage gated channel > opens transiently(short time) in response to change in membrane potential
  2. Ligand gated channel > opens/closes in response to a specific ECF NT
  3. Mechanically gated channel > respond to mechanical deformation
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22
Q

Define nerve

A

a group of axons + connective tissue wrappings and blood vessels

e. g. epineurium: around entire nerve
perineurium: around each fascicle
endoneurioum: around each axon

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23
Q

What is the funny bone?

A

Ulnar nerve

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24
Q

Define neural glial cells

A

specialized cells that support neurons > 90% of cells in NS

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25
Identify the glial cells in the CNS
astrocytes oligodendrocytes microglia ependymal cells
26
Identify the glial cells in the PNS
satellite cells | schwann cells
27
Astrocytes
provide physical and nutritional support in CNS contribute to BBB help with scar tissue
28
oligodendrocytes
provide insulation > myleination in CNS
29
microglia
digest the dead cells in CNS
30
ependymal cells
produce, monitor, circulate CSF.
31
satellite cells
provide physical support in the PNS
32
schwann cells
provide insulation > myleination in PNS
33
Contrast neurons and glial cells
NEURONS > 2 processes (axon and dendrite), can generate AP's, have synapses that use NT's GLIAL > 1 process, cannot generate AP's and do not have chemical synapses BUT have 10-50X more in brain than neurons
34
Define mylein sheaths
insulate and increase nerve impulse speed are made from lipids and proteins are formed by oligodendrocytes and schwann cells provide electrical insulation have nodes of ranvier
35
Gray vs. white matter
Gray > cell bodies, white > the axonal connections (white due to myleination)
36
A cell with an RMP is ______ to produce ____
primed, AP
37
____ must be produced to depolarize a cell to a threshold, in order for an AP to take place
graded potential
38
Define graded potential
a small deviation from membrane potential which causes a cell to become either more, or less polarized " a small local change" occurs when mechanical gated or ligand gated channels open or close mainly occur in dendrites and cell bodies (thats where these channels are numerous)
39
Define a dopolarizing graded potential
the cell is LESS negatively charged (on graph moves higher)
40
Define a hyperpolarizing graded potential
the cell is MORE negatively charged (on graph moves lower)
41
The size of a GP is related to ___
the size of the stimulus. | a strong stimulus >> a large GP
42
The strength of the stimulus is related to ___
the duration and number of open channels
43
define decremental conduction
GP's die out as they spread across the plasma membrane
44
define summation
adding together GP's
45
What are the two types of summation?
Temporal and spatial
46
define temporal summation
in response to stimuli that occurs at the same location in membrane but at different TIMES
47
define spatial summation
in response to stimuli that occur at different LOCATIONS but at the same time
48
SO if a GP reaches the threshold (-55mv)… ___
then an AP occurs. AP spreads down the axon of neuron to terminals. It the GP is not strong enough, there will be no nerve impulse. "all or none"
49
Define Action potential
the sequence of events that decrease and reverse the membrane potential, and then restore it
50
Identify the 5 phases of an AP
1. RMP: membrane must be at rest for an AP to occur. Na channels and K channels are closed 2. Depolarization: membrane potential becomes LESS NEGATIVE. Na opens, and influxes 3. Repolarization: returns to RMP. Na channels close, K channels open and K out fluxes 4. After-hyper-repolarization: membrane temporarily becomes more negative than resting because K channels have not yet closed 5. refractory period: period of time following an AP where another cannot by generated
51
Identify the two refractory periods
absolute refractory period: even a strong stimulus canNOT elicit another AP (during depolarization) relative refractory period: a 2nd AP CAN be initiated, if the stimulus is strong enough. (during repolarization)
52
Where does an AP propagate?
travels down the axon to the end terminals; regenerates along the axon. One AP triggers the next...
53
So in summary… a GP >> Na channels open >> Na enters >> local depolarization >> Na in adjacent segments are activated >> continued….
:)
54
Identify and explain the two types of AP conduction
1. continuous conduction: step by step del. and rep. of membrane. One triggers another locally, axons are unmyleinated and propagation is slow. 2. saltatory conduction: less channel opening > less Na and K pump use > more energy efficient. AP's jump across NoR and result in quicker propagation. Axons are myleinated. - NoR: dep. opens Na channels and AP is replenished - myleinated sections: current flows quickly with minimal leak
55
Identify the three factors affecting speed of AP conduction
1. myleination: more is better 2. diameter: bigger is better (decreases resistance) 3. temperature: warmer is better
56
How many nerve fibres are there? Name them.
3: A, B and C
57
define Nerve fibre A (DIA, myelin, speed)
most efficient, refractory period is shortest. | Diameter 5-20 nm, axon is myleinated > super fast!
58
define nerve fibre B (DIA, myelin, speed)
less efficient, refractory period is bigger | diameter 2-3 nm, axons is myleinated > relatively quick
59
define nerve fibre C (DIA, myelin, speed)
least efficient | diameter .5-1.5 nm, axons are unmyleinated > very slow
60
Distinguish between a neuronal AP and a muscular AP… (RMP, impulse duration, speed)
Neuronal - -70mv RMP - 0.2. ms impulse duration - large diameter (18x) faster than the sarcolemma of a skeletal muscle Muscular - -90mv RMP - (skeletal) 1-5 ms; (cardiac) 10-300ms impulse durations
61
A chemical synapse consists of three things..
- axon terminal of pre-an - synaptic cleft ~20-30 nm - dendrites/ motor end plate of post -sn (membrane)
62
List the events of an AP at terminal end of a pre-an bulb
1. nerve impulse moves down the axon to the terminal end 2. Ca channels open and influx 3. vesicles release NT into synapse 4. NT's diffuse across cleft 5. NT's bind to receptors sites of post -sn 6. a post synaptic potential is generated 7. a nerve impulse is elicited
63
Synaptic connections can be either inhibitory or excitatory - explain
IPSP's: GP results in hyper polarization (NO) EPSP's: GP results in depolarization (GO)
64
What is the relationship between NT's and receptors? Give examples
Receptors are specific to a type of NT e. g. - cholinergic receptors are for ACh (movement) - glutaminergic receptors are for glutamate (excite) - GABA-ergic receptors are for GABA (inhib)
65
Define the two types of receptors
1. inotropic: receptor contain a binding site and an ion channel > direct 2. metabotropic: receptor contains binding site, but works through a G protein. The G protein can either directly open own channel, or can indirectly thru a signalling molecule
66
What are three ways to remove excess NT's from the cleft?
1. diffusion 2. enzymatic degredation 3. re-uptake @ pre-synaptic cell
67
Distinguish between the 4 different neural circuits that can occur
1. diverging: single >> to many 2. converging: many >> to single 3. reverbrating: reversal influences (single line) 4. parallel-after discharge: parallel lines, reversal influence
68
What are to mechanisms that help s to repair and regenerate nervous tissue?
1. our ability to change based on experience = PLASTICITY > sprouting > synthesis > changes in contact 2. our ability to replicate/repair = REGENERATION > can occur in PNS IF cell body is intact and schwann cells are active > limited to none repair in CNS
69
Define neurogenesis
in CNS: birth from stem cells in the HPX: crucial for learning > may not occur in SC because oligodendrocytes in PNS: cell body must be intact and schwann cells must be active, scar tissue also cannot form too fast

Physiology 190 (6 decks)

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