Physiological Function Of The CVS

Question 1

What is the process of the cardiac action potential?

Answer 1

• depolarisation: of the cardiac cells by fast volt-gate Na ch opening and Na flows in after reaching threshold potential
• plateau: volt-gate K ch open and K+ flows out, also slow volt-gate Ca ch open Ca entering the cell
• repol: volt-gate Ca ch close and volt-gate K remain open allowing repol

Question 2

What is the process of the heart pumping blood around the body?

Answer 2

Atrial systole: - the atria fill from the vena cava and the pulmonary artery, dictated by the SAN leads to the atria contracting and forcing the blood into the ventricles, the pressure exceeds the pressure needed to open the bicuspid and tricuspid valves
Early ventricular systole: - the ventricles fill with blood and the atria relax, the bi and tricuspid valve close to stop flow back
Late ventricular systole: - the ventricles contract causing the pressure to exceed the pressure needed to open the semilunar valves in the pulmonary vein and aorta to push blood into the lungs and around the body
Early ventricular diastole: - all the chambers of the heart relax and all the valves are shut (atrial pressure high and arterial trunk pressure lower)
Late verification diastole: - all the chambers are relaxed, the bi and tricuspid valves are open, the atrial pressure drops
This is the full cycle of the heart

Question 3

Describe the electrical process of the heart cycle?

Answer 3

• SAN starts to the AVN to the bundle of His, to the Purkinje fibres leading to contraction
• lasts approx 0.75s

Question 4

What is the definition of systole, atrial systole and ventricular systole?

Answer 4

To contract
Contraction of the atrial myocardium
Contraction of the ventricular myocardium

Question 5

What is the definition of diastole, atrial diastole and ventricular diastole?

Answer 5

To dilate
Relaxation of atrial myocardium
Relaxation of atrial myocardium

Question 6

What does each wave of the ECG relate to in the cardiac cycle?

Answer 6

P wave: - SAN generates pacemaker potential depolarising across the atria
QRS complex: - AP reaches AVN to ventricles, ventricles are depolarised and contract
- atrial repol masked by QRS
T wave: - ventricular repol, ventricles are relaxed

Question 7

The scientific name for a change in heart rate?

Answer 7

Chronotropic

Question 8

What is the scientific word for changes in force of contraction?

Answer 8

Inotropic

Question 9

What are examples of controls of the cardiac cycle?

Answer 9

Blood volume and pressure
Drugs
Local blood flow
ADH, ANG II and aldosterone

Question 10

What is the conduction system of the SAN?

Answer 10

• gradual rise in mem pot due to hard reduction in outward K and increase in inward current of Na and Ca (until threshold is reached -55mV)
• depol: large influx of Ca one threshold is reached
• early repol: Ca ch start to close
• late repol: K efflux repolarises cells

Question 11

What are some facts about the heart?

Answer 11

Weight: 250-350g and 12cm L and 9cm W
Resting heart rate: 60-80 bpm 
Exercise heart rate: 140-180 bpm
Heart pumps 70ml per hb, approx 5L per min
Heart average lifespan of 78yrs

Question 12

What are some characteristic of cardiac conduction cells?

Answer 12

Automaticity: - initiate electrical impulse
Excitability: - respond to an electrical impulse
Conductivity: - transmit electrical impulse from one cell to another

Question 13

What is the physiology of cardiac conduction?

Answer 13

Cardiac electrical activity is the result of the movement of ions across the cell mem
Resting state cardiac muscles are polarised, creating an electrical difference between -ve inside and +ve outside

Question 14

What are the definitions of the basic concepts of polarisation, voltage and current?

Answer 14

Polarisation: - different in charge between side of a mem
Voltage: - different in positive charges from one side of mem to the other
Current: flow of charged particles across a mem

Question 15

What is the refractory period of non-pacemaker cells?

Answer 15

Allows the heart to refill before the next contraction
ARP: absolute RP; - second stim will no cause response
ERP: effective RP; - second stim can cause AP

Question 16

What is the physiological characteristic of the vascular system?

Answer 16

Blood is ejected from the Lab into the aorta and conducted via arterioles to capillary beds within organ system and allowing nutrient exchange
Inner surface of BVs lines by EC and layers of SMCs
Elastin provides elasticity and collagen provides stiffness
Microcirculation: smallest arterioles, capillaries and post-capillary benules
Allow transfer of gas, water and waste products between blood and tissues

Question 17

What do the BVs transport?

Answer 17

Transport blood that also transport water, glucose, lipids, amino acids, vitamins, mineral, oxygen and CO2 (waste)

Question 18

What is the physiology of the elastic arteries such as the aorta?

Answer 18

Role to buffer the pressure wave originating from the LV (to reduce damage on weaker arteries)
75% of the SV is accompanied by the distinction of elastic arteries
Elastin recoils the artery in diastole

Question 19

What is the physiology of the muscular arteries such as the femoral/brachial and radial arteries?

Answer 19

They distribute blood to the organs, higher SM competent and lower elastin content
Smooth muscle contraction provides active reg of diameter

Question 20

What is the physiology of the veins such as the vena cava?

Answer 20

Recycle the blood back to the heart, and removes waste products to the lungs
Venous tone determines distribution of blood between periphery (limbs and mesentery and thorax), regs central venous pressure (SV and CO)
Mobilising venous blood (perfusion of essential organs during exercise)