4.4 circulation

Question 1

artery structure

Answer 1

thick muscular walls to handle high bp without damage
elastic tissue allows recoil
narrow lumen to maintain high blood pressure

Question 2

vein structure

Answer 2

thin walls bc low bp so minimal force exerted
valves to prevent back flow
less muscle and elastic tissue as blood flow does not have to be controlled
wide lumen

Question 3

capillary structure

Answer 3

one cell thick to reduce diffusion distance
very narrow so can permeate tissues, increase BP, increase speed, increase contact of RBC with capillary wall
numerous and highly branched for large SA

Question 4

double circulatory system

Answer 4

needed for mammals due to high metabolic rate
ensures rapid oxygen transport
steep concentration gradient
prevent mixing of oxygenated and deoxygenated blood
allows blood to be carried at high bp to body but lower to lungs due to use of small vessels to prevent damage

Question 5

diastole

Answer 5

heart relaxes and AV valves open
deoxygenated blood from vena cava flows into RA. oxygenated blood from pulmonary vein flows into LA
blood passes into ventricles passively

Question 6

atrial systole

Answer 6

SAN sends wave of excitation through atria walls causing contractions
atria contract simultaneously (top down) forcing blood into ventricles through AV valves
blood moves RA to RV and LA to LV

Question 7

ventricular systole

Answer 7

AVN receives wave of excitation. there is a pause in signal to allow atria to finish contracting
wave of excitation moves through walls of ventricles (through Purkyne Fibres) causing ventricle walls to contract (bottom up)
force of blood causes AV valves to close and prevents blood flowing back into atria
blood is forced RV to RA and from LV into aorta through semi lunar valves

Question 8

myogenic

Answer 8

without nerve impulse

Question 9

myogenic stimulation of the heart

Answer 9

1) SAN sends impulse across atria walls causing them to contract (top down) a region of non conducting tissue between atria and ventricles prevents impulse being sent down to ventricles, causing a slight delay in ventricle contraction
2)impulses reach AVN and are passed, via bundle of Hiss to Ventricles
3) bundle of His splits into two branches and sends impulse down the septum and through ventricles
4) impulse causes ventricles to contract from apex (bottom up) and squeezes blood out of heart

Question 10

plasma

Answer 10

carries water soluble materials
maintains body temp
pH buffer
involved in clotting

Question 11

erythrocytes

Answer 11

haemoglobin t bind and carry O2 for aerobic respiration
small and biconcave for large SA: vol
no nucleus for more haemoglobin

Question 12

leucocytes

Answer 12

neutrophils and monocytes engulf and digest pathogens in phagocytosis
eosinophils are involved in allergenic response ad protection against virus and pathogenic worms
lymphocyte (T and B cells) are part of non specific and specific immunity and production of memory cells and antibodies

Question 13

function of blood

Answer 13

mass transport system moving substance’s e.g. hormones and oxygen