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555- Physiology & Pathophysilogy > Exam 4 - Cardiac Potentials & ANS > Flashcards

Exam 4 - Cardiac Potentials & ANS Flashcards

1
Q

What does cardioplegia do

A
  • Stops heart by decreasing [K] gradient…stops flow of K out of cell…..holding heart in a depolarized state
  • Keeps K channel gates from resetting
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2
Q

Cardiac Action Potentials

A
  • Very fast….happen in cardiac cells

- Created by changing permeability of Na, K, Ca channels

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3
Q

Phase 0

A
  • Depolarization
  • Big increase in Na permeability
  • Na rushes into cell making more +
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4
Q

Phase 1

A
  • The overshoot at top of peak (due to excess Na into cell)
  • Na permeability DECREASE
  • Ca permeability INCREASE
  • K permeability STARTS INCREASE
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5
Q

Phase 2

A
  • Plateau phase (pronounced in cardiac cells)
  • Caused by increase Ca into cell
  • Na permeability back to normal
  • K permeability continues to increase (K moves out)
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6
Q

Which ion is needed for actual muscle contraction

A
  • Ca

- In fast action potential cells only

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7
Q

Phase 3

A
  • Repolarization phase
  • Ca permeability back to normal
  • Na permeability back to normal
  • BIG INCREASE in K permeability
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8
Q

Phase 4

A
  • Normal resting potential….cell is polarized
  • RMP for cardiac cells is -90 mV
  • RMP in muscle cells is stable
  • RMP in SA/AV node is NOT stable
    - Leaky Na channels slowly depolarize cell at phase 4
    - Eventually trigger Action Potential
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9
Q

Speed of Muscle cells AP

A

Fast

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10
Q

Speed of AP in SA/AV node

A
  • Slow
  • Also a slowly depolarizing phase 4 (automaticity)
  • Ca drives this slow depolarization
  • No plateau in slow cells because Ca doesn’t contribute to contraction
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11
Q

Absolute refractory

A
  • Not able to generate action potential
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12
Q

Relative refractory

A
  • If given enough voltage…can cause AP
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13
Q

Supranormal refractory

A
  • Smaller than normal voltage can cause AP
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14
Q

How is AP conduction velocity determined

A
  • Diameter of fiber (AV is small…Purkinje are big)
  • Intensity of local depolarization
  • Resistance of cell junctions
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15
Q

Which node is pacemaker of heart

A
  • SA node….doesn’t have to be but usually is

- Steepest phase 4 slope

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16
Q

What does AV node do to AP

A
  • Slows it down
  • Makes sure Ventricles can fill all the way
  • Slow due to small size of cells
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17
Q

PR Interval

A
  • Conduction time through atria and AV node
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18
Q

QT interval

A
  • duration of ventricular systole
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19
Q

Velocity of AP in Atrial muscle

A

0.3 m/s

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20
Q

Velocity of AP in Internodal pathways

A

1.0 m/s

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21
Q

Delay in AV node and AV bundle system

A

0.13 seconds

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22
Q

Velocity of AP in Purkinje

A

1.5 - 4.0 m/s

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23
Q

Velocity of AP in Ventricular Muscle

A

0.3 - 0.5 m/s

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24
Q

Intrinsic rate of SA node

A

100 bum

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25
Intrinsic rate of AV node
40 - 60 bpm
26
Intrinsic rate of Purkinje
15 - 40 bpm
27
What innervates the nodes
- Both the sympathetic and parasympathetic
28
What innervates the cardiac muscle
- Sympathetic
29
Parasympathetic fibers release what
- Ach - Interacts with muscarinic receptors - Changes RMP and phase 4 slope - Increase K permeability in RMP - Decreases Na permeability - Decrease HR
30
Sympathetic fibers release what
- Norepi - Interacts with B-1 receptors - Changes slope of phase 4 only - Increases Na and Ca permeability - Increase HR
31
Chronotropic
- Affects HR | - High Ca tends to decrease HR
32
Dromotropic
- Affects conduction velocities | - High sympathetic tone increases velocity (affects AV node)
33
ANS control centers
- Spinal cord - Brain stem - Hypothalamus - Visceral reflexes
34
Which vessels innervated by ANS
Arterioles
35
Hypothalamus controls...
- Food control - H2O balance - Temp. regulation - All parasympathetic things
36
Brain stem controls....
- Bladder - Pneumotaxic - Cardiac speed up - Cardiac slow down - Respiratory center
37
Effector organs controlled by....
- Either sympathetic or parasympathetic....not both
38
Sympathetic neuron set up
- Short pre-ganglionic (Ach) - Long post-ganglionic (Norepi) - Fibers originate from T1 to L2
39
Paravertebral sympathetic ganglion chains
- two of them - run either side of spinal cord - can move message up and down chain - once message received....3 transmission options
40
3 paravertebral ganglion chains transmission options
- synapse directly with post-ganglionic fibers - pre-ganglionic to ciliac/hypogastric ganglia to post-ganglionic - through sympathetic chain to adrenal medulla
41
Parasympathetic neuron setup
- Long pre-ganglionic (Ach) (pass all the way to organ) - Short post-ganglionic (Ach) (located in wall of organ) - Arise from Cranial nerves 3, 7, 9, 10...and 2-3 sacral nerves - 75% of parasympathetic nerves are in 10
42
Synapse structure
- Mitochondria: make ATP for transmitter production - Vesicles: store transmitters - Cleft: space between - Presynaptic terminal has voltage gated Ca channels
43
Transmitter release steps
- AP reaches Ca channels and activates them - Ca rushes in to the terminal end - Stimulates release of transmitter into cleft - Amount of transmitter released proportional to amount of Ca
44
Receptor protein structure
- Outside Binding portion - Transmembrane ionophore portion - ionophore part can be ion channel (short term effects) - or second messenger activator (long term effects)
45
Types of ion channel receptors on post-synaptic membrane
- Cation: think Na / tends to be excitatory (depolarize) | - Anion: think Cl / tends to be inhibitory (hyperpolarize)
46
Second messenger ionophore
- G-protein - 3 proteins grouped on inside - Alpha part is activator - Beta and Gamma stay put
47
4 actions of alpha component
- Open ion channels - Activate cAMP - Activate enzymes - Activate gene transcription -All activate actions happen at effector organ site
48
Cholinergic fibers
- Release Ach
49
Adrenergic fibers
- Release norepi
50
Ach
- Parasympathetic transmitter - Acetyl CoA + Choline = Ach - needs choline acetyltransferase - Removed by acetylcholinesterase degradation - choline end product transported back into terminal for recycle
51
Norepi sympathetic post-ganglionic exceptions
- Sweat glands, some blood vessels, pilorector muscles release Ach
52
Norepi production
- Tyrosine -> Dopa -> Dopamine - Dopa -> Dopamine done in vesicles - In adrenal medulla... 80% converted to Epi....20% remain norepi
53
Norepi removal (3 ways)
- 50-80% moved back into terminal via active transport - Most of the rest diffuse away - Small amount destroyed by enzymes in liver
54
Norepi active time
- Several seconds unless released by adrenal medulla....then 10-30 seconds. - 1-3 minutes to go away completely
55
Two types of Cholinergic receptors
- Muscarinic: on effector organ innervated by parasympathetic post-ganglionic fibers - Nicotinic: on neuromuscular junction of muscles and postganglionic fibers of all ANS fibers
56
Two types of adrenergic receptors
- Alpha: 1 and 2 (affected by Norepi and Epi) - Beta: 1, 2, and 3 (affected by Epi) - Both can be either excitatory or inhibitory (depends on organ)
57
Tone
- # of impulses - How active system is - 1 impulse/second will maintain - 10-20 impulse/second will fully activate
58
Systemic arterioles diameter
- Kept at 1/2 of normal diameter by sympathetic tone
59
Normal adrenal medulla tone
- 0.05 Norepi - 0.2 Epi - ug/kg/min - Note if all sympathetic innervation lost...basal secretion of these two would maintain normal arterial blood pressure - Sympathetic tone is combo of neural (synapse) and humoral (adrenal)
60
Alpha 1 receptors function
- vasoconstriction - intestinal relax - iris dilation - bladder constriction
61
Alpha 2
- inhibits neurotransmitter release
62
Beta 1
- Increase HR | - Increase strength
63
Beta 2
- Vasodilation - intestinal relax - bronchodilation
64
Beta 3
- Thermogenesis
65
Parasympathetic effects
- Slow HR - Dilate heart/lung vessels - Constrict bronchi - Increase gut activity - Glycogen synthesis

555- Physiology & Pathophysilogy (12 decks)

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