Circulation

Question 1

Elastic arteries

Answer 1

largest arteries, smooth muscle in medial layer largely replaced by elastic tissue
High compliance
recoil of elastic fibres forces blood to move

Question 2

Muscular arteries

Answer 2

Arranged circumferentially
Majority of tunica media is smooth muscle
Greater vasoconstriction and vasodilation to adjust flow rate
Vascular tone - partial contraction maintains vessel pressure and flow

Question 3

Arterioles

Answer 3

finer - smaller than artery
within tissues
Smooth muscle important for regulating diameter and controlling blood pressure

Question 4

Venules

Answer 4

less muscular than arterioles
still some smooth muscle
within tissues

Question 5

Veins

Answer 5

Less muscular and elastic but dispensable enough to adapt to variations in volume and pressure

Question 6

Large veins

Answer 6

More muscular
Valves prevent backflow
Slow blood flow and low pressure

Question 7

Capillaries

Answer 7

Endothelial cells and basement membrane
Exchange of substances between blood and interstitial fluid
continuous capillary, fenestrated capillary, sinusoidal capillary

Question 8

Starlings forces

Answer 8

Fluid movement = hydraulic conductance ((capillary hydrostatic pressure - interstitial hydrostatic pressure) - (capillary oncotic pressure - interstitial oncotic pressure))

Question 9

Oncotic pressure

Answer 9

form of osmotic pressure induced by the proteins, notably albumin, in a blood vessel’s plasma (blood/liquid) that causes a pull on fluid back into the capillary

Question 10

Principal proteins in plasma

Answer 10

Albumin
Fibrinogen
Globulin
Other coagulation factors

Question 11

Neutrophil

Answer 11

phagocytose bacterial

Question 12

Eosinophils

Answer 12

combat parasites and viruses

Question 13

Basophils

Answer 13

release IL4, histamine, heparin, peroxidase

Question 14

Lymphocytes

Answer 14

mature into T cells and B cells

Question 15

Monocytes

Answer 15

macrophages and dendritic cells

Question 16

Feedback mechanism for platelet production

Answer 16

Abundant platelets bind to TPO –> megakaryocytes not generated –> platelets not made –> receptors do not bind to TPO –> TPO stimulates megakaryocyte production –> platelets made

Question 17

mechanism of haemostasis

Answer 17

Constriction of blood vessel

Formation of temporary platelet plug

activation of coagulation cascade

Formation of fibrin plug/clot - semi solid mass of platelets and fibrin mesh

Question 18

what do blood clots consist of

Answer 18

Euthrocytes, leukocytes, serum, mesh of fibrin, platelets

Question 19

intrinsic pathway of clotting

Answer 19

surface contact activation on membrane of activated platelets
activation of factor XII
kininogen and prekallikrein are proteins that facilitate this activation

Question 20

Extrinsic pathway of clotting

Answer 20

(membrane bound tissue factor activation) activated when blood contacts material from damaged cell membranes

Tissue factor receptor on cell – binds to factor 7 at sight of injury (activated factor 7)

Forms Ca2+, factor 7 and tissue factor complex which activates factor 10

Question 21

Sequence of depolarisation in the heart

Answer 21

SA node depolarises
cardiac cells conduct cell to cell through atrial muscle
Signal hits AV node
Antrioventricular ring prevents impulse spread to ventricles
Impulse sent to bundle of His and Purkinje fibres

Question 22

Steps in the cardiac cycle

Answer 22

Atrial diastole - Blood flows into atria, AV valve closed
Atrial systole - atria contracts, blood leaves atria and enters lower chambers
Ventricular diastole - AV and SL valves closed, as pressure in ventricle decreases relative to atria, AV valves open and blood flows into ventricle
Ventricular systole - ventricles contract, pressure higher than atria, AV valves close, SL valves open, blood es ejected from heart

Question 23

what does the P wave represent?

Answer 23

Atrial depolarisation

Question 24

What does the QRS wave represent

Answer 24

Ventricular depolarisation

Question 25

What does the T wave represent

Answer 25

Ventricular repolarisation

Question 26

Main components of blood

Answer 26

Plasma, Ethrocytes, Leukocytes, Platelets

Question 27

How do erythrocytes maintain their shape

Answer 27

cytoskeleton bound to plasma membrane by glycophorin and CL- HCO3 exchanger

Question 28

What factors effect blood viscosity

Answer 28

haemocrit, fibrinogen plasma concentration, vessel radius, linear velocity, temperature

Question 29

How is blood clotting prevented?

Answer 29

Anticoagulant molecules (TFPI, antithrombin, proteins S and C, thrombomodulin) move from endothelium to interact with elements in the coagulation pathways

Question 30

Deep vein thrombosis (DVT) risk factors

Answer 30

venous stasis, vascular injury, hypercoagulability

Question 31

Pressure in the arteries

Answer 31

Under high pressure as they receive blood directly from the heart

Question 32

Pressure in the arterioles

Answer 32

walls have tonically active smooth muscle to maintain pressure
site of highest resistance to flow

Question 33

How do blood vessels constrict?

Answer 33

innervated by sympathetic adrenergic nerve fibres, when activated cause constriction of vascular smooth muscle, reducing diameter of arteriole and increasing resistance to flow

Question 34

Equation for velocity of blood flow

Answer 34

V (velocity) =Q (flow) /A (cross sectional area)

Question 35

Equation for flow

Answer 35

Q (flow) = ΔP (pressure difference)/R (resistance)

Question 36

Equation for resistance to blood flow

Answer 36

R (resistance) = 8n (viscosity of blood) l (length of blood vessel) /πr^4

Question 37

Diastolic pressure

Answer 37

lowest arterial pressure during ventricular relaxation

Question 38

Systolic pressure

Answer 38

highest arterial pressure after blood is ejected from ventricles

Question 39

Pulse pressure

Answer 39

systolic pressure - diastolic pressure

Question 40

Mean arteriole pressure

Answer 40

diastolic pressure + 1/3 pulse pressure