Lecture 10

Question 1

What is the purpose of the heart?

Answer 1

To supply the rest of the body with oxygenated blood to satisfy the metabolic demands of all the other tissues and organ systems

Question 2

What is the pumping action of the heart influenced by?

Answer 2

Preload and after load

Question 3

What is preload?

Answer 3

Volume of blood returned from venous circulation - the amount of blood that the rest of the body is trying to pump from the heart

Question 4

What is after load?

Answer 4

Resistant to blood exiting the ventricles to the rest of the body

Question 5

How do you know if after load has increased?

Answer 5

If it becomes more difficult to pump against the pressure

Question 6

What are the two main mechanisms that help the heart adapt to changing circumstances?

Answer 6

Stretch-sensitive contraction and sympathetic drive

Question 7

Who found the stretch sensitive contraction?

Answer 7

Frank starling

Question 8

Describe the stretch sensitive contraction

Answer 8

the greater the stretch on the myocardium before systole (preload, the stronger the ventricle contraction

Question 9

What does the length tension relationship indicate - from frank -starlings law?

Answer 9

Indicates an optimal range of sarcomere length (1.6-1.2 microns)

Question 10

What is a process that initiates the frank-starling technique?

Answer 10

Running up the stairs - not just the ventricle that responds

Question 11

What happens in the frank starling mechanisms for increased venous return?

Answer 11

Increased venous return usually distends ventricles within the range of the optimal sarcomere length and this facilitates increased force of next contraction

Question 12

What did brain bridge discover?

Answer 12

Discovered the right atrial response

Question 13

What did bainbridge show?

Answer 13

That increasing the amount of blood returning to the heart stretched the right atrium

Question 14

What is the stretch of the heart sensed by?

Answer 14

By lots of mechanical-sensed channels, which induces the elevation of cytosolic ca2+ due to the opening of L type channels - increased the SA node

Question 15

What is cardiac rhythmicity matched to?

Answer 15

Matched to mechanical preload in beat-to-beat manner

Question 16

What are the 4 mechanisms in the sympathetic drive?

Answer 16

Chronotropic, ionotropic, lusitropic and dromotropic

Question 17

What is chronotropic?

Answer 17

Increased heart rate

Question 18

What is ionotropic?

Answer 18

Increased force of contraction, via a cellular process occurring at the level of myofilaments

Question 19

What is luistropic?

Answer 19

Increased relaxation

Question 20

What is dromotropic?

Answer 20

Increased conduction

Question 21

What des the sympathies drive occur from?

Answer 21

As a result of the beta-agonist signal transduction and the phosphorylation of many potential targets

Question 22

What happens when you activate the sympathetic nervous system?

Answer 22

You have an activation of adrenergic receptors

Question 23

What happens when adrenaline adrenergic receptors are activated?

Answer 23

Adenylyl cyclase increases production of protein kinase A which phosphorylates proteins

Question 24

What happens when you phosphorylate a protein?

Answer 24

Change the conformation of the protein, structure which influences the shape and what the protein binds to.

Question 25

What can the phosphorylated protein sometimes be?

Answer 25

Inhibitory or stimulators - depends on the nature of the phosphorylation changes the structure of the protein

Question 26

Where are the substrates of cardiomyocytes located?

Answer 26

Located on contractile proteins on the myofilaments

Question 27

In cardiomyocytes what does the beta agonist isoprenaline do?

Answer 27

Decreases action potential duration, action potential is shortened

Question 28

What else does the beta agonist isoprenaline do?

Answer 28

Increase T-type current and increase L-type ca2+ current

Question 29

How can the ion channel be altered - from isoprenaline?

Answer 29

The PKA can target the T type and L type channels and increase the opening of the channels and increase the flow of ion current through those channels with beta receptors stimulation

Question 30

What happens in a shorter periods of duration of the ca2+ - due to isoprenaline?

Answer 30

Get more influx over the plasma lemma which activates been more CICR at the junctions of the SR

Question 31

What happens in a single isolated cardiomyocytes by the beta-agonist isoprenaline

Answer 31

Increase in ca2+ amplitude, contraction, rate of ca2+ returning to the base line and rate of relaxation

Question 32

Why is the rate of relaxation increased?

Answer 32

Because of phospholamban which contributes to the SERCA pump in the SR to regulate the dynamic

Question 33

What effect does phospholamban have on the SERCA pump?

Answer 33

Inhibitory effect

Question 34

What needs to happen because you have a shorter action potential?

Answer 34

The contraction needs to have a shorter period as well

Question 35

What does an increase of contraction shorter time period need?

Answer 35

Cardiac troponin and myosin binding protein C

Question 36

what is the stretch of the chamber sensed by?

Answer 36

myofilaments which enhances the contraction of the stroke volume of the heart