Lecture 10 - Myocardial EC Coupling Flashcards Preview

FHB Exam 1 - Cardiovascular Physiology > Lecture 10 - Myocardial EC Coupling > Flashcards

Flashcards in Lecture 10 - Myocardial EC Coupling Deck (67)
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1

Which part of the EKG shows atrial depolarization? Which shows the time from start of atrial depolarization to start of ventricular depolarization?

P Wave

- P-R interval

2

Which part of EKG show ventricular depolarization? Which show ventricular depolarization, ventricular contract, and ventricular depolarization?

QRS

- Q-T interval

3

What does the T wave on an EKG show? What does an inversion often indicate?

Ventricular depolarization

- inversion may indicate recent MI

4

What is the ST segment show?

Ventricles depolarized

5

What causes the U wave?

1. Hypokalemia
2. Bradycardia

6

What is the order of speed of conduction in the heart? Pacemaker?

What is the conduction pathway??

1. Purkinje> Atria> Ventricles> AV Node

2. SA Node> AV> Bundle of His/Purkinje/ventricles

3. SA Node --> Atria --> AV NODE --> common bundle -> Bundle Branches --> Fascicles --> Purkinje fibers --> Ventricles

7

What is the function of the sarcolemma?

Plasma membrane of Cardiac cells
1. propagates Action Potentials
2. controls Ca influx by activating SLOW INWARD CALCIUM current

8

What part of the cardiac cell activates the SLOW inward calcium current?

depolarization of T-tubules from sarcolemma

9

What is the function of T-Tubules?

Transmits AP from Sarcolemma
- depolarization activates slow Ca influx

10

Where are T-tubules found?

Z-lines

- connected by RyR receptors to SR

11

What is the function of the Sarcolemma?

intracellular Calcium storage site

12

Where are terminal cistern & longitudinal cistern found?

SR!!

13

What is the function of Terminal Cisternae?

Site in SR where Ca influx TRIGGERS opening of Calcium release channels to initiate contraction

14

What is the function of LONGITUDINAL cisternae?

RECYCLING
- site of Ca re-uptake to initiate RELAXATION

15

What is the function of Troponin C?

- binds Calcium to initiate contraction

Calcium receptor on contractile protein (actin)

16

What is the function of Troponin I?

(phosphorylating it activates it)

- prevents the binding of Calcium to Troponin C
= causes RELAXATION when phosphorylated

17

Is the contraction mechanism (actin myosin cross bridge) the same in cardiac & skeletal muscle contraction?

YES

18

What is the mechanism of E-C coupling?

1. AP sent down sarcolemma, enters T-tubule
2. T-tubule depolarization activates slow inward Ca channels
3. Ca influx binds & opens RyR receptors
4. Increase Ca influx from SR --> binds Troponin C
5. Tropomyosin shifts, and actin & myosin can bind
6. CONTRACTION (CICR= calcium induced calcium release)

19

How can we maintain contraction?

Maintain elevated cytosolic Calcium

20

What are the mechanisms of relaxation?

1. Ca re-uptake into SR by Ca-ATPase (SERCA) - 80%
2. NA/Ca antiporter (18%)
3. Ca out of CELL via Sarcolemma Ca pump(2%)

21

What is a mechanism for reducing CYTOSOlIC calcium?

SERCA

- brings it back to SR

22

What is a mechanism for reducing CELLULAR calcium?

Na/Ca pump
(3 Na in/1 Ca out)

23

What occurs if Sodium influx is decreased via Na/Ca antiporter?

- reverse action
- less Na in
- less Ca OUT = increase Ca in cell for CONTRACTION

24

Which cells, cardiac or skeletal, function by syncytium? How is this achieved?

CARDIAC

- coordinated via gap junctions

25

How are cardiac and skeletal muscles activated?

1. Cardiac = gap junctions

2. Skeletal = NMJ --> via ACh (released into clft & binds to post-synaptic membrane causing Na influx resulting in DEPOLARIZATION

26

Contraction of skeletal muscle is dependent on what? Cardiac?

1. AP via NMJ!

NOT CICR --> Voltage Sensor of Calcium (DHPR) that allows Calcium to enter cell via RyR receptors

2. Calcium induced Calcium release

27

How is contraction increased in cardiac cells? Skeletal?

1. INCREASE CALCIUM influx via SLOW CALCIUM CURRENT & SR Ca Content!

2. increase in AP frequency increases amplitude of contraction (& recruitment of muscle fibers)

28

Which cells, cardiac or skeletal, experiences tetany or summation?

Skeletal (summation of AP & muscle fiber recruitment)

29

True or false: Cardiac cells utilize primarily anaerobic metabolism

FALSE!

- use Aerobic, have a lot of mitochondria & use a lot of ATP

- skeletal is primarily via Glycolysis

30

Relaxation is occurred when what is reduced?

CYTOSOLIC CALCIUM