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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
Q

Intrinsic rate of AV node

A

40 - 60 bpm

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26
Q

Intrinsic rate of Purkinje

A

15 - 40 bpm

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27
Q

What innervates the nodes

A
  • Both the sympathetic and parasympathetic
28
Q

What innervates the cardiac muscle

A
  • Sympathetic
29
Q

Parasympathetic fibers release what

A
  • Ach
  • Interacts with muscarinic receptors
  • Changes RMP and phase 4 slope
  • Increase K permeability in RMP
  • Decreases Na permeability
  • Decrease HR
30
Q

Sympathetic fibers release what

A
  • Norepi
  • Interacts with B-1 receptors
  • Changes slope of phase 4 only
  • Increases Na and Ca permeability
  • Increase HR
31
Q

Chronotropic

A
  • Affects HR

- High Ca tends to decrease HR

32
Q

Dromotropic

A
  • Affects conduction velocities

- High sympathetic tone increases velocity (affects AV node)

33
Q

ANS control centers

A
  • Spinal cord
  • Brain stem
  • Hypothalamus
  • Visceral reflexes
34
Q

Which vessels innervated by ANS

A

Arterioles

35
Q

Hypothalamus controls…

A
  • Food control
  • H2O balance
  • Temp. regulation
  • All parasympathetic things
36
Q

Brain stem controls….

A
  • Bladder
  • Pneumotaxic
  • Cardiac speed up
  • Cardiac slow down
  • Respiratory center
37
Q

Effector organs controlled by….

A
  • Either sympathetic or parasympathetic….not both
38
Q

Sympathetic neuron set up

A
  • Short pre-ganglionic (Ach)
  • Long post-ganglionic (Norepi)
  • Fibers originate from T1 to L2
39
Q

Paravertebral sympathetic ganglion chains

A
  • two of them
  • run either side of spinal cord
  • can move message up and down chain
  • once message received….3 transmission options
40
Q

3 paravertebral ganglion chains transmission options

A
  • synapse directly with post-ganglionic fibers
  • pre-ganglionic to ciliac/hypogastric ganglia to post-ganglionic
  • through sympathetic chain to adrenal medulla
41
Q

Parasympathetic neuron setup

A
  • 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
Q

Synapse structure

A
  • Mitochondria: make ATP for transmitter production
  • Vesicles: store transmitters
  • Cleft: space between
  • Presynaptic terminal has voltage gated Ca channels
43
Q

Transmitter release steps

A
  • 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
Q

Receptor protein structure

A
  • Outside Binding portion
  • Transmembrane ionophore portion
    • ionophore part can be ion channel (short term effects)
    • or second messenger activator (long term effects)
45
Q

Types of ion channel receptors on post-synaptic membrane

A
  • Cation: think Na / tends to be excitatory (depolarize)

- Anion: think Cl / tends to be inhibitory (hyperpolarize)

46
Q

Second messenger ionophore

A
  • G-protein
  • 3 proteins grouped on inside
  • Alpha part is activator
  • Beta and Gamma stay put
47
Q

4 actions of alpha component

A
  • Open ion channels
  • Activate cAMP
  • Activate enzymes
  • Activate gene transcription

-All activate actions happen at effector organ site

48
Q

Cholinergic fibers

A
  • Release Ach
49
Q

Adrenergic fibers

A
  • Release norepi
50
Q

Ach

A
  • Parasympathetic transmitter
  • Acetyl CoA + Choline = Ach
    - needs choline acetyltransferase
  • Removed by acetylcholinesterase degradation
    - choline end product transported back into terminal for recycle
51
Q

Norepi sympathetic post-ganglionic exceptions

A
  • Sweat glands, some blood vessels, pilorector muscles release Ach
52
Q

Norepi production

A
  • Tyrosine -> Dopa -> Dopamine
    - Dopa -> Dopamine done in vesicles
  • In adrenal medulla… 80% converted to Epi….20% remain norepi
53
Q

Norepi removal (3 ways)

A
  • 50-80% moved back into terminal via active transport
  • Most of the rest diffuse away
  • Small amount destroyed by enzymes in liver
54
Q

Norepi active time

A
  • Several seconds unless released by adrenal medulla….then 10-30 seconds.
  • 1-3 minutes to go away completely
55
Q

Two types of Cholinergic receptors

A
  • Muscarinic: on effector organ innervated by parasympathetic post-ganglionic fibers
  • Nicotinic: on neuromuscular junction of muscles and postganglionic fibers of all ANS fibers
56
Q

Two types of adrenergic receptors

A
  • 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
Q

Tone

A
  • # of impulses
  • How active system is
  • 1 impulse/second will maintain
  • 10-20 impulse/second will fully activate
58
Q

Systemic arterioles diameter

A
  • Kept at 1/2 of normal diameter by sympathetic tone
59
Q

Normal adrenal medulla tone

A
  • 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
Q

Alpha 1 receptors function

A
  • vasoconstriction
  • intestinal relax
  • iris dilation
  • bladder constriction
61
Q

Alpha 2

A
  • inhibits neurotransmitter release
62
Q

Beta 1

A
  • Increase HR

- Increase strength

63
Q

Beta 2

A
  • Vasodilation
  • intestinal relax
  • bronchodilation
64
Q

Beta 3

A
  • Thermogenesis
65
Q

Parasympathetic effects

A
  • Slow HR
  • Dilate heart/lung vessels
  • Constrict bronchi
  • Increase gut activity
  • Glycogen synthesis

555- Physiology & Pathophysilogy (12 decks)

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