Circulatory System

Question 1

What are the different types of circulatory systems?

Answer 1

Open circulatory system - blood not enclosed in vessels

Closed circulatory system - Blood enclosed in vessels

Single circulatory - blood travels in one loop and passes through the heart once for each circuit

Double circulatory - Blood travels in 2 loops and passes through the heart twice in one circuit

Question 2

Describe the structure and function of arteries?

Answer 2

Carry blood away from heart

Need to maintain high pressure

Thick muscular wall with lots of elastic tissue - withstand pressure

Endothelium is folded which allows artery to expand - withstanding pressure

Small lumen - maintain pressure

Question 3

Describe structure and function of veins

Answer 3

Carry blood to the heart

Blood flows at low pressure

Large lumen and thinner walls with little elastic tissue or muscle tissue

Valves to prevent blood flowing backwards

Contraction of nearby body muscles helps blood flow

Question 4

Describe the structure and function of capillaries

Answer 4

Connect arteries and veins

Substances move out of the blood

waste products move out of body into capillaries

Pores for exchange of substances

One cell thick - reduces diffusion distance

Question 5

How is tissue fluid formed?

Answer 5

At arteriole end of capillary, hydrostatic pressure exceeds oncotic pressure

fluids and dissolved subsatnces are forced out of capillary into spaces around the cell forming tissue fluid

At venule end of the capillary, there is less water so water potential is lower inside the capillary compared to tissue fluid

water moves into capillary by osmosis down a water potential gradient

excess tissue fluid drains into lymphatic system

Question 6

describe the structure of the heart

Answer 6

Made of 4 chambers:
Left and right atrium
Left and right ventricle

Left side is thicker as it needs to pump blood more strongly around the body

Left side carries oxygenated blood and right side carries deoxygenated blood

Atrioventricular valves and semi lunar valves

Question 7

Describe the flow of blood through the heart

Answer 7

Oxygenated blood enters the left atrium from the pulmonary vein and passes into the left ventricle through the AV valve

Left ventricle contracts and pumps blood out through the SL valves and aorta to the rest of the body

Deoxygenated blood flows into the right atrium via the vena cava and passes through the AV valve into the right ventricle

Right ventricle contracts and blood passes through SL valve and is pumped out via the pulmonary artery

Question 8

Describe atrial systole

Answer 8

Atria contracts and ventricles relax

Pressure increases in atria

AV valves open and blood enters the ventricles

SL valves are closed

Question 9

Describe ventricular systole

Answer 9

Ventricles contract while atria are relaxed

Increases pressure in ventricle

AV valves are closed and SL valves are opened

Blood if forced out of ventricles into arteries

Question 10

Describe Diastole

Answer 10

Both atria and ventricles are relaxed

Pressure is low in both chambers

SL valves close

Atria fills with blood

Question 11

explain myogenic contraction

Answer 11

SAN generates a wave of excitation which spreads across atrial walls causing them to contract simultaneously.

non-conducting tissue prevents excitation directly reaching ventricles

wave of excitation reaches AVN which delays excitation so atria fully contract

Wave of excitation is passed down Bundle of His before being spread across the ventricle walls across the purkyne fibres

Ventricles contract for the bottome up

Question 12

Describe an ECG

Answer 12

P wave - atrial systole

QRS complex - ventricular systole

T wave - Diastole

Question 13

What are the 3 heart problems?

Answer 13

Tachycardia - abnormally fast heart rate

Brachycardia - abnormally slow heart rate

Eptopic heartbeat - extra heartbeat

Fibrillation - complete loss of rhythm

Question 14

Describe the structure of haemoglobin

Answer 14

Large globular protein with a quaternary structure made of 4 polypeptide chain

2 alpha helixes and 2 beta pleated sheets

its 4 sub units each possess a haem group containing Fe ion

4 oxygen molecules form oxyhaemoglobin

Question 15

Explain haemoglobins affinity for oxygen

Answer 15

The higher the affinity the stronger it binds

High affinity in the lungs where there is high partial pressure of oxygen

Low affinity at repairing tissues where there is a low partial pressure of oxygen

Question 16

Explain the dissociation curve

Answer 16

Graph is S-shaped because binding of first oxygen molecule causes haemoglobin to change shape

Other oxygen binding sites are revealed

easier for oxygen to bind - cooperative bonding

once 3 oxygens have bound, it is harder for the last one to bind because there is only 1 binding site

Question 17

What is fetal haemoglobin?

Answer 17

has a higher affinity for oxygen compared to adult haemoglobin

Binds more strongly to oxygen

Ensures that it is still oxyhaemoglobin by the time it passes the placenta

On sissociation curve, fetal haemoglobin is slightly to the right

Question 18

What is the Bohr Effect?

Answer 18

At higher partial pressure of CO2, haemoglobin has lower affinity for oxygen

oxyhaemoglobin dissociates more readily

usefull with higher rates of respiration as more oxygen is needed and higher amounts of CO2 is produced