human physiology 100 - cardiovascular system

What are the five functions of blood?

1. Transport of dissolved substances
2. Regulation of pH and ions, absorbs and neutralises lactic acid
3. Resurrection of fluid losses at injury sites (blood clotting)
4. Defence against toxins and pathogens (WBCs)
5. Stabilisation of the body temperature, absorbs heat from active muscles and distributes to other tissues

What does blood consist of?

55% plasma

45% plasma
- erythrocytes (RBC)
- leukocytes (WBC)
- thrombocytes

What is hemocrit?

Is the measure of % of RBC in whole blood

- male: 47% (40-54%)
- female: 42% (38-46%)

How are blood cells formed?

Through the process of hematopoiesis which produces hemocytoblasts that differentiate into:

1. Myeloid stem cells that give rise to RBC, platelets etc.

2. Lymphiod stem cells that give rise to lymphocytes

What are the characteristics of erythrocytes?

- 99% of bloods formed elements
- high surface are to volume ratio
- biconave disks
- contains haemoglobin
- no mitochondria
- no nucleus
- replaced at a rate of 2 million/ sec

What's regulates erythropoiesis and why would it be released?

Is regulated by erythropoetin (EPO) hormone

Is released due to:
- anaemia
- low blood flow to kidney
- damage time respiratory surface of lung
- low O2 in lungs

What are the four basic blood types?

1. A (surface antigen A) (antibodies to B)
2. B (surface antigen B) (antibodies to A)
3. AB (antigens A and B) (no antibodies)
4. O (neither A nor B) (antibodies to A and B)

What is the Rhesus factor?

- refers to the D antigen
- Rh+ = surface antigen present
- Rh- = no surface antigen

e.g RBC - surface antigen A and Rh antigen = A+ blood type

What are the functions of platelets?

- release important clotting chemicals
- temporarily patch damaged vessel walls
- actively contract tissue after clot formation

What are the phases of hemostasis?

1. Vascular phase
2. Platelet phase
3. Coagulation phase

What are the key concepts of hemostasis?

- platelets are involved
- platelets, activated by abnormal changes in local environment, release clotting factors and other chemicals
- is a complex cascade that builds a fibrous patch that can be remodeled and removed as the damaged area is repaired

What is clot retraction and repair?

- platelets pull on fibrin threads, clot contracts drawing wound edges together
- fibroblasts form connective tissue and new endothelial cells repair vessel lining
- clot dissolves due to plasma enzyme

What is the pulmonary circuit and what is the systemic circuit?

- pulmonary circuit: carries blood to and from gas exchange surface of lungs. Takes deoxygenated blood from the heart and returns oxygenated blood

- systemic circuit: carries blood to and from the rest of the body. Takes oxygenated blood from the heart and returned deoxygenated blood.

What is the pericardium?

- encloses the heart and stabilises it
- fibrous network of collagen fibres
- lines by serous membrane with two layers:
1. Outer: parietal pericardium
2. Inner: visceral layer (epicardium)

What makes up the heart wall?

1. Epicardium
- visceral layer of serous membrane
2. Myocardium
- cardiac muscle tissue
- provides pumping action
3. Endocardium
- continuous with endothelium lining of great vessels

What are the characteristics of the myocardium?

- cardiac muscle fibre ( one central nucleus)
- connected via gap junctions
- have very high aerobic capacity

What are intercalated disks?

- specialised contact points between cardiomyocytes
- join cells via gap junctions and desmosomes
- enhance molecular and electrical connections
- conduct action potentials

What are the chambers of the heart?

left and right upper atria
- receive blood into heart
- left atria = pulmonary (deoxygenated)
- right atria = systemic (oxygenated)

Left and right lower ventricles
- pump blood away from heart
- left ventricle = systemic (oxygenated)
- right ventricle= pulmonary (deoxygenated)

What is the difference between the left and right ventricles?

Right ventricle pumps blood to pulmonary circulation (to and from lungs)
- has thinner wall
- less pressure than left

Left ventricle pumps blood to systemic circulation (to and from rest of body)
- thicker walk
- greater pressure
- rounder in shape

What are the atrioventricular valves (AV valves)?

- low between atria and ventricles
- pressure in atria > pressure in ventricles = valves open, blood flows into ventricles
- pressure in ventricles > pressure in atria = valves close, blood in aorta it's pulmonary aorta

What are the semilunar valves?

- between ventricles and major arteries
- prevent blood flowing back into heart
- stop backflow of blood from aortic and pulmonary trunks into ventricles

What are coronary artistries and coronary sinus?

- coronary arteries carry oxygenated blood to the myocardium

- coronary sinus carries deoxygenated blood back to the right atrium

What are the types of cardiac muscle fibres?

Autoryrhmic fibres
- initiate and conduct action potential
- form conduction system

Contractile fibres
- provide mechanical work of the pump

What is the sinotrial (SA) node?

- is the pace maker
- spontaneously depolarises (80-100 times/min)
- rate of depolarisation modifies by neurotransmitters

What is the atrioventricular (AV) node?

- spontaneous depolarisation (40 - 60 times / min)
- conduction slows at the AV node (AV normal delay)
- delay allows atria time to contract and fill ventricles

What are the phases of cardiac action potential?

1. Rapid depolarisation
- voltage gated sodium channels open
2. Plateau
- sodium channels close
- calcium channels opens, balances slow sodium outflow
3. Repolarisation
- calcium channels close
- potassium channels open

What is the sequence of electrical events?

1. SA node generates action potential

2. Stimulus spreads across atria and reaches AV node

3. AV nodal delay - atrial contraction begins

4. Action potential spreads along AV bundle, bundle fibres, purkinje fibres

5. Action potential relayed across ventricles, ventricles contractv

What are the criteria for efficient pumping?

1. Atria must contract before ventricles

2. Coordinate excitation so that each heart chamber contracts as a syncitium

3. Two atria should contract together and two ventricles should contract together

What is the cardiac cycle?

The period between the start of one heartbeat and the beginning of the next

Includes both contraction and relaxation

What are the heart chambers that are linked to pulmonary circuit?

The right ventricle and left atrium

Deoxygenated blood leaves the right ventricle and oxygenated blood enters the heart through the left atrium

What are the heart chambers that are linked to systemic circuit?

The left ventricle and right atrium

Oxygenated blood leaves the left ventricle and deoxygenated blood enters the heart through the right atrium

What is the difference between atrioventricular and semilunar valves?

- AV valves stop the backflow of blood from ventricles into atria

- semilunar valves stop backflow of blood from aortic and pulmonary trunks into ventricles

What do these ECG waves represent:
- P wave
- QRS complex
- T wave

- P wave= atrial depolarisation
- QRS complex= ventricular depolarisation
- T wave= ventricular repolarisation

What is the EDV and ESV?

End diastolic volume (EDV) = volume of blood in each ventricle at end of ventricular diastole

End systolic volume (ESV) = volume of blood remaining in each ventricle at the end of ventricular systole (40% of EDV)

What is stroke volume?

The volume of blood pumped out of each ventricle during a single beat

SV = EDV - ESV

What is the ejection fraction?

Percentage of EDV represented by SV = 60% of EDV

What is cardiac output?

The volume of blood pumped by left ventricle in one minute

CO = HR x SV

What factors affect heart rate?

1. Autonomic innervation of the heart
2. Hormones

What factors affect stroke volume?

1. End diastolic volume
- filling time
- venous return
- preload

2. End systolic volume
- preload
- contractility
- after load

What does ACh do to the heart rate?

- ACh increases the amount of time that the membrane repolarises
- slows depolarisation
- slowing action potentials
- slowing the heart rate

What does adrenaline do to the heart rate?

- shortens repolarisation
- accelerates rate of spontaneous depolarisation
- increasing heart rate

What are elastic arteries?

- conducting arteries
- largest diameter arteries
- carries blood away from the heart
- stores elastic energy
- helps move blood during diastole
- is a pressure reservoir

What are muscular arteries?

- medium sized arteries
- distributes and regulates blood flow to muscles and internal organs (construct and dilate)
- superficial muscular arteries form pressure points

What are arterioles?

- highly muscular
- well innervated
- small radii
- regulate systemic vascular resistance through vascoconstriction (sympathetic) and vascodilation

What are capillaries?

- thin walled
- highly permeable
- exchange vessels

What are veins?

- thin walled
- highly muscular
- highly distensible
- many contain valves to prevent backflow of blood
- hold 60% of blood
- are capacitance vessels (volume reservoir)

What is blood flow?

Volume of that flows through a tissue per unit of time

Determined by blood pressure and resistance

Blood flow is proportional to _______ and inversely proportional to _______

- pressure gradient
- resistance

What are the following blood pressures:

- arterial pressure
- capillary hydrostatic pressure
- venous pressure
- circulatory pressure

- arterial =
• 120 mmHg at aorta
• 35 mmHg at start of capillary
- CPH = 35-18 mmHg
- venous = ~ 18 mmHg
- Circulatory pressure = ~ 100 mmHg

Vascular resistance is ____ and is dependent on ___

Is the opposition of blood flow due to friction between blood and vessel wall

Depends on:
- vessel length
• increase length = increase resistance
- vessel diameter
• decrease diameter = increase resistance

Resistance is inversely proportional to:

The 4th of radius of lumen

Velocity decreases as ______ and increases as _____

Decreases as blood flows from aortas to capillaries

Increases as blood flows from capillaries to heart

Mean arterial pressure / blood pressure equations:

MAP = diastolic BP + 1/3 pulse pressure

MAP = 2/3 diastolic BP + 1/3 systolic pressure

What is venous return and what is it maintained by?

Is the volume of blood returning to heart from systemic veins

Maintained by:
- pressure gradient established by heart
- skeletal muscle pump
- respiratory pump
- valves

Low blood pressure:

Is hypotension (< 90/60)

- blood vessels collapse
- blood flow stops
- tissues die

High blood pressure:

Is hypertension (> 140/80)

- vessel walls stiffen
- capillary beds may rupture

What are the methods that substances enter and exit capillaries by?

1. Diffusion (most important)
2. Transcytosis
3. Bulk flow (filtration and absorption)

How to baroreceptors sense and react to abnormal heart rates?

Low BP
- baroreceptors stretched less
- send impulse to CV centre
- increase cardiac output and vascoconstriction via sympathetic stimulus

High BP
- baroreceptors stretched more
- send impulse to CV centre
- vascodilation occurs

What are cardiovascular responses to exercise?

- extensive vasodilation
- increase in cardiac output
- increase in venous return
- decrease in total peripheral resistance (TPR)