CVR 17

Question 1

What are the determinants of volume pumped by the heart

Answer 1

preload or venous return

contractality of force at any given VEDV

Afterload or resistance

Question 2

Parts of the brain controlling the heart

Answer 2

higher centres, cerebral cortex eg frontal lobe orbital cortex motor cortex also affect HR or contractility

Question 3

How is the heart sympathetically innervated

Answer 3

T1-4 via cervical and stellate ganglia using NA and adrenaline via beta 1 receptors

Question 4

How is the heart parasympathetically innvervated

Answer 4

Originating in the medulla from dorsal motor nucleus of vagus and nucleus ambiguss routed via ganglia on surface of heart via M2 receptors with Ach on chillinergic receptors

Question 5

At rest what determines the pace of the heart

Answer 5

PNS vagal tone

Question 6

How does Ach work in the PNS for the heart

Answer 6

decreases rate by increasing gK+ efflux and decreasing GCa and gNa influx (decrease slope phase 4 )

Question 7

How does NA affect the heart

Answer 7

Increase gK out and increase slow Ca and Na (increase slope phase 4)

Question 8

How do beta blockers affect the heart

Answer 8

Atenolol causes teh heart rate to decrease and contractility to decrease by blocking beta 1 receptors adrenergic

Question 9

What does atropine do

Answer 9

muscarinic M1 blocker that increases heart rate

Question 10

What is preload

Answer 10

Factors contribituing to VEDV or ventricle muscle length.

This includes blood volume which is affected by RAAS, ADH, ANP

Question 11

What is a feature of veins that allows for blood flow against gravity

Answer 11

compression and valves

Question 12

What contributes to the contractality of the heart

Answer 12

sarcomere - starlings law

SNS - increases

PNS - minimally negative

Hormones - insulin, TH

Question 13

Where does the Ca++ go during diastole or relaxation

Answer 13

reuptake by SR via antiporter ATPase pump, Camp

Question 14

5 steps to muscle action (recap)

Answer 14

1. Relaxed state low Ca means myosin and actin bindling blocked by tropomyosin
2. AP causes Ca2 to bind to troponin forcing tropomyosin to move exposing myosin to actin
3. myosin binds to actin and racheting happen
4. ADP and Pi released
5. Binding of ATP to myosin forces detachment of head

Question 15

Stretching of cardiac muscle does what

Answer 15

increase Ca++ sensitivity of contraction

change overlap of thick and thin filaments

Question 16

Increase in VEDV results in

Answer 16

increase in SV and CO

Question 17

What is starlings law

Answer 17

contraction depends on fibre length

Question 18

How do positive inotropic agents work

Answer 18

calcium works by beta 1 agonist increasing cAMP.

cAMP causes increase in Ca++, calcium from SR, affinity for Ca, reuptake of Ca into SR

Final result is myocytes contract faster and stronger

Question 19

How does Digitalis work

Answer 19

inhibit Na/K atpase by increaseing intracelll Na by not letting any out resulting in more intra Ca++ (Foxglove plant)

Question 20

How do negative inotropic agents work

Answer 20

Hypoxia, acidosis diminish Ca amount from SR.

Beeta blockers like propanaol and attenlol do this.

Calcium channel blockers like benzothiazipines also do this

Question 21

What is Ficks Principle

Answer 21

02 delivered to pulmonary caps in pul artery plus 02 from alveoli must equal 02 carried away in pulmonary veins