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Cell Phys > Lec 16: Cardiac Muscle > Flashcards

Lec 16: Cardiac Muscle Flashcards

1
Q

Cardiovascular system is comprised of: (2)

A

heart

blood vessels

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2
Q

Cardiovascular System Functions: (5)

A
  1. ) Deliver blood to all organs and tissues of the body
  2. ) Provide nutrients & oxygen to the tissues
  3. ) Remove wastes
  4. ) Deliver hormones
  5. ) Deliver immune system cells to sites of infection
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3
Q

Memorize Pulmonary/Systemic Circuit pressure system (screenshot)

A

plzzzzzzzzz

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4
Q

(Cardiac Muscle)
Only in…

  • Cells =
  • like skeletal, they are…
  • …but…
A
  • the heart

= cardiac myocytes

  • they are striated,
  • involuntary (autonomic NS control)
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5
Q

(Cardiac Muscle)
- Cardiac myocytes are…

  • Ultrastructure is
  • Lots of…
A
  • short, irregular in shape, and sometimes branched with a central nucleus
    ~10 mm in diameter
  • very similar to skeletal muscle (i.e., sarcomere, myofibrils, t-tubules, SR)
  • capillaries & mitochondria
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6
Q

Heart Function =

A

= Pump blood throughout the cardiovascular system – pulmonary & systemic circulation

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7
Q

Blood vessels are…

A

highly specialized tubes

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8
Q

3 kinds of Blood vessels:

A

arteries
capillaries
veins

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9
Q

NEVERMIND
(Arteries)
- Handle…

  • Regulate: (2)
A
  • high blood pressures & pulse pressure (= SP-DP) (physical exertion)
  • mean arterial pressure (70-110 mm Hg) (Resistance vessels) & tissue perfusion
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10
Q

NEVERMIND
(Capillaries)
Facilitate the Transfer of: (4)

A
  1. ) O2 and nutrient molecules to the tissues from blood
  2. ) wastes from the tissues to the blood
  3. ) hormones to the tissues from blood
  4. ) immune system cells to the tissues from blood
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11
Q

NEVERMIND
(Veins)
- Require…

  • May have…
A
  • low pressures (in order for blood to flow through capillaries)
  • valves to insure one-way flow to the heart
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12
Q

The cardiac myocytes are connected…

Allows for…

A

…in series via intercalated discs
Intercalated disc = combination of gap junctions and desmosomes

… electrical coupling (“functional syncitium”), passing of AP from cell to cell

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13
Q

Heart functions as a

A

‘pump’

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14
Q

Diastole =

Systole =

A

= the phase of the heartbeat when the heart muscle is relaxed

= the phase of the heartbeat when the heart muscle contracts.

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15
Q

Heart pumping steps: (3)

& Thus…

(use pic screenshot for visualization)

A
  1. ) Both atria and ventricles are relaxed and both fill with returning blood.
  2. ) Atria contract (atrial systole)– pumping blood into the ventricle.
  3. ) Ventricle contracts second (ventricular systole)-pumping blood out of the heart.

…the heart has a system to control the order and rhythm of myocyte contraction

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16
Q

S-A Node =

A-V Node =

A

= sinoatrial node (sets rhythm of the heartbeat)

= atrioventricular node

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17
Q

(Conducting System of Heart)
- Heart contains a specialized conduction system for: (2)

Note =

A
  1. ) Setting the rhythm of the heart beat – autorhythmicity
  2. ) Transferring the electrical signal to various parts of the heart musculature

= These are all cardiac muscle cells NOT nerve cells

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18
Q

(Conducting System of Heart) Steps: (6)

A
  1. ) S-A node fires AP first
  2. ) AP spreads throughout the Atria (Atria contract – blood flows from atria to ventricles)
  3. ) AP conduction is delayed at the A-V node
  4. ) AP is carried to the apex of the ventricles via conducting fibers (Bundle of His)
  5. ) AP is carried to the ventricular muscle via Purkinje fibers
  6. ) AP spreads throughout the ventricles (ventricles contract – blood flows out of ventricles to systemic and pulmonary circuits
19
Q

APs are…

A

different at various regions

20
Q

(S-A Node)
- Cells in the SA node set…

  • since they…
  • They are:
  • SA node cells are aka
  • NOTE =
A
  • the rhythm of the heart beat,
  • fire (AP) first and all other cells will follow in succession.
  • Autorhythmic – fire an AP spontaneously
  • “Pacemaker cells”

= other cells in the heart are also auto- rhythmic, but the activity of the S-A node normally sets their pace and the pace of the heart rate.

21
Q

(Pacemaker cells of S-A Node_
- Have…

  • Other cardiac myocytes are at
  • Leaky to…
  • and have…
  • Also have very few…
A
  • a high resting potential (Vm) = ~ -60 to -65 mV
  • ~ -90 mV
  • Na+
  • a lower K+ permeabilty, thus Vm is a little closer to ENa+
  • voltage-gated Na+ channels
22
Q

(Pacemaker Cell AP (autorhythmicity))

Steps: (5)

A
  1. ) The pacemaker cells “spontaneously” depolarize (Pacemaker Potential)
    • Due to Na+ leaking in (called If for “funny” current) through “pacemaker channels”.
    • Some Ca2+ leaks in too.
  2. ) Once threshold is reached → fire AP
  3. ) AP is due to Ca2+ entering through voltage gated Ca2+ channels (L- & T-type)
  4. ) Repolarization is due to opening of voltage-gated K+ channels
  5. ) The L & T-type Ca2+ channels become inactivated leading to a refractory period
23
Q

(Atrial & Ventricular Contractile Myocytes)
- Have…

  • Highest permeability at rest is to…
  • Also have many: (2)
A
  • a low resting potential (Vm) = ~ -90 mV
  • K+, thus Vm is close to EK+
  • voltage-gated Na+ and Ca2+ channels
24
Q

(Atrial & Ventricular APs)
- Both are…

  • ______ __ is shorter in duration than _____ __
  • Both have…
A
  • prolonged 200 – 400 mSec (neuron AP lasts
  • Atrial AP is shorter in duration than ventricular AP
  • a plateau at the top
25
Q

(AP duration)
Nerve =

Skeletal Muscle =

Atrial & Ventricular Myocyte =

S-A Node =

A

= 1 - 2 mSec

= 2 – 5 mSec

= 200 – 400 mSec

= 200 mSec

26
Q

Review Atrial & Ventricular AP phase graph (screenshot)

A

plzzzzz don’t you want an AAAAAA

27
Q

Phase 4 =

Highest permeability =

Vm is…

A

= Rest

= K+

  • …close to EK+
28
Q

Phase 0 =

Highest permeability =

What opens?

Influx of

Causes…

A

= Depolarization (initiated by preceding myocyte)

= Na+

= Voltage-gated Na+ channels

  • Na+
  • the large depolarization (-90 to +30)
29
Q

Phase 1 =

Inactivation of…

Activation of…

The relatively gradual activation of

Note =

A

= Short small repolarization (+30 to +10)

  • Na+ channels
  • K+ channels accounts for the repolarization (slow)
  • L-type Ca2+ channels opposes repolarization and leads to the plateau (phase 2)

= The initial depolarization causes all of these changes

30
Q

Phase 2 =

What’s open?

Requires…

Cell remains…

K+ channels are…

K+ efflux is…

A

= Plateau

L-type Ca2+ channels are

  • several hundred mSec to completely inactivate
  • depolarized for several hundred mSec
  • open, but balanced by L-type Ca2+ channels
  • balanced by Ca2+ influx
    (stay at -10 to +10 mV)
31
Q

Phase 3 =

  • Complete inactivation of…

Returns __ towards…

A

= Repolarization

  • L-type Ca2+ channels
    Open K+ channels (they eventually close)
  • Vm towards EK+
32
Q

ECG =

A

Electrocardiogram

33
Q

P Wave =
QRS Complex =
T Wave =

& draw diagram (screenshot)

A

= Activation of the atria
= Activation of the ventricles
= Recovery Wave

34
Q

(Cardiac Myocyte contraction)

Similar to…

A
  • skeletal muscle (thick and Thin Filaments, sarcomeres, etc)
35
Q

(Cardiac Myocyte contraction)

The AP Causes: (2)

A
  1. ) Causes an influx of Ca2+

2. ) Causes release of Ca2+ from the SR

36
Q

(Cardiac Myocyte contraction)

2 sources of Ca2+ for cardiac muscle:

A

Extracellular

Sarcoplasmic reticulum

37
Q

E-C Coupling =

A

Ca2+ induced Ca2+ release

38
Q

(E-C Coupling)
Important Components: (2)

Contraction follows…

Relaxation due to…

A
  1. ) Ryanodine receptor
  2. ) L-type Ca2+ Channels.
  • the rise in free Ca2+.
  • Ca2+ removal: Ca2+ pumps at sarcolemma & SR and Na+/Ca2+ exchanger
39
Q

VICR –>

CICR –>

A

(skeletal muscle)

cardiac muscle

40
Q

How can heart rate be changed?

A

Modify the Pacemaker Potential

41
Q

2 ways to Modify the Pacemaker Potential:

A
  1. ) Epinephrine & Autonomic Sympathetic stimulation speeds up the pacemaker potential. Fight or flight response. (Top Panel on slide)
  2. ) Autonomic Parasympathetic stimulation slows down the pacemaker potential. Resting state. (Bottom Panel on slide)
42
Q

(Modifying the Pacemaker Potential/#1: Flight or flight)
- Increases…

  • Opens…
  • Reach…
  • Due to…
  • Faster…
A
  • If
  • pacemaker channels.
  • threshold quicker.
  • cAMP
  • HR
43
Q

(Modifying the Pacemaker Potential/#2: Autonomic…)
- Decreases…

  • Increases…
  • Reach…
  • Due to
  • Slower
A
  • If
  • IK+ (opening K+ channels)
  • threshold slower
  • muscarinic AchR
  • HR

Cell Phys (16 decks)

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