heart as a pump

Question 1

EDV

Answer 1

end diastolic volume (EDV) = volume in the heart’s left ventricle refer to the volume (in mL) of blood just prior to the heart beat
from 65mL (resting volume) to 135 mL

Question 2

ESV

Answer 2

end systolic volume (ESV) = volume in the heart’s left ventricle refer to the volume (in mL) of blood after heart beat
back to 65mL (resting volume)

Question 3

how parasympathetic ns affects autorhymtic cells

Answer 3

1. ACh of muscarinic receptors
2. limits positive ions that enter the cell so Ca2+ influx decreases and more K+ leave too (efflux)
3. cells hyperpolarise= slower depolarisation, takes longer to reach pacemaker potential
4. lowers the frequency of AP fired

== heart rate decreases

Question 4

how sysmpathetic ns affects autorhymtic cells

Answer 4

1. nor/adrenaline of beta one receptors of those autorhythmic cells.
2. increases positive ions that enter the cell so Ca2+ influx decreases and less K+ leave too (efflux)
3. cells depolarise = faster to reach pacemaker potential
4. increases the frequency of AP fired

== heart rate increasee

Question 5

Cardiac output (CO)

Answer 5

Cardiac output (CO)
* Volume of blood pumped (per ventricle), per given time (mLs/min)
* Indicator of total blood pumped around the body
CO = Heart Rate (HR) x SV
e.g. 70bpm x 70ml per beat =4.9L per min

Question 6

how to control SV

Answer 6

stroke volume
* Directly related to the force generated by cardiac muscle which is controlled by two factors:
1. Length of the muscle fibres
* EDV (End-diastolic volume) determines length prior to contraction
== Length-Tension Relationship

2. Contractility of the heart
   * Ca2+ availability determines contractility

Question 7

Length-Tension Relationship

Answer 7

The length of the sarcomere, and thus the length of the fibre directly relates to the force that muscle fibre can produce
* Similar to skeletal muscle
* If more blood flows (volume increases) into the heart, muscle fibres stretch and therefore contract more forcefully
* Eject more blood (increased SV)
* Relationship is known as the Frank-Starling law of the heart

Question 8

how to alter EDV

Answer 8

• EDV is determined by Venous Return = Blood returning to the heart from venous circulation
• Factors that alter venous return:
  1. Contraction or compression of veins = Skeletal Muscle or Musculovenous pump
  2. Pressure changes in abdomen and thorax = Respiratory pump
  3. Sympathetic innervations of veins = Vasoconstriction

Question 9

how to increase contractability

Answer 9

innervated by your sympathetic nervous system again
1. nor/adrenaline binds to beta one receptors in your cardiac muscle cells.
2. activates cAMP system second messenger system
3. phosphorylases voltage gated Ca2+ channels and phospholabam

voltage gated Ca2+ channels =
open longer, more Ca2+ enter into muscle, for contraction

phospholamban=
increases the activity of calcium A TP ase in the sarcoplasmic reticulum
–> increase Ca2+ stores in SR = more Ca2+ released
–> faster recycling of Ca2+ = shorter contractions, higher frequency of contractions

Question 10

resistance factors of blood flow

Answer 10

Resistance is affected by 3 factors:
* Radius of the vessel (r)
* Length of the tube (L)
* Viscosity of the fluid (𝜂)

Poiseuille’s law
Rresistance proportional to 1/r^4
e.g. Vessel 1 has r = 1 and Vessel 2 has r =2
Vessel 2:
R == 1/16 resistance comparred to Vessel 1
and flow rate is 16x more

Question 11

Driving pressure in arterial system

Answer 11

1. when ventricles contract, semilunar valves open, blood flows from ventricles to aorta/arteries
2. aorta/arteries expand to accommodate the high pressure blood
3. ## pressure is stored in the elastic walls
4. when ventricle relax, semilunar (aortic valve) valves close to prevent blood flow back into ventricles
5. elastic walls recoil of arteries, driving blood forward to rest of the circulation

Question 12

Mean arterial pressure (MAP)

Answer 12

average between your systolic and your diastolic pressure that is driving blood forward into the tissues

MAP = diastolic pressure + 1/3(pulse pressure)
* 80mmHg+13mmHg = 93mmHg
* PP = SP – DP
* 120 mmHg – 80 mmHg = 40 mmHg
not 100mmHg because 2/3rds of the time its spent in relaxation and diastole and only 1/3 is in systole and contraction
–> Arteries offer little resistance to flow, therefore MAP is similar in all arteries