IB Biology Review
Circulatory System
Why do we need blood circulation?
Move blood around the body to
Bring oxygen to cells
Take away carbon dioxide
Take away other metabolic waste
Bring metabolic reactants (sugar)
Bring water
Bring hormones
Bring antibodies
Bring nutrients
Distribute heat
Basically, to keep our bodies doing what they do!
What are the components of the
circulatory system?
Heart
Arteries
Veins
Capillaries
Remember Arteries Away from heart
Arteries have oxygenated blood
Veins have deoxygenated blood
A Closer Look at the Heart
Identify the structures of the heart.
1
15
2
14
3
13
12
4
11
5
6
7
10
8
9
Be able to draw something like this.
Pulmonary veins
Atrioventricular valves
Semilunar valves
The Path of Blood through the Heart
Deoxygenated blood comes from body through
superior and posterior vena cava
Enters right atrium
Goes through atrioventricular valve
Enters right ventricle, pumped into pulmonary artery
Passes through semilunar valve
Gets oxygen from lungs
Enters left atrium via pulmonary veins
Goes through atrioventricular valve
Enters left ventricle, pumped into aorta
Passes through semilunar valve
Blood goes to rest of the body
How Blood Gets Oxygen
(2) Goes from right
ventricle to pulmonary
artery
(3) Goes to lungs
(4) Comes through
pulmonary vein to left
atrium
(5) Goes to left ventricle
(6) Goes through aorta
(7) (8) To body!
Which arteries help out the heart?
Coronary arteries supply heart muscle with
Oxygen
Nutrients
How does the heart know when to pump?
The heart beats by itself (myogenic)
The SA node sends an electrical signal to the walls of
the atria
This causes them to contract (think about when you get
electrocuted, your hand snaps back because your muscles contract)
SA signal reaches the AV node, which delays the signal
AV node sends signal to ventricles, which contract
Atrioventricular valves snap shut
After blood leaves ventricles, semilunar valve closes to
prevent back flow
Composition of Blood
Blood is made of
Plasma
Erythrocytes (red blood cells)
Leucocytes (white blood cells)
Phagocytes
Lymphocytes
Platelets
IB Exam Question
1. Which vessel carries deoxygenated
blood?
(1 mark)
A.
B.
C.
D.
The pulmonary artery
The coronary artery
The aorta
The pulmonary vein
Correct answer: A
IB Exam Question
2. What is the function of the right
ventricle?
(1 mark)
A.
B.
C.
D.
Pumping blood into the pulmonary artery
Pumping blood into the pulmonary vein
Pumping blood into the aorta
Pumping blood into the coronary artery
Correct answer: A
IB Exam Question
3. Draw a labelled diagram to show the internal
structure of the heart.
(6 marks)
Award [1] for each of the following structures clearly drawn and
labelled correctly in a diagram of the heart.
left and right ventricle;
left and right atria;
atrioventricular valves;
semilunar valves;
aorta and vena cava;
pulmonary artery and pulmonary vein;
ventricle wall thicker than atria;
left ventricle wall thicker than right ventricle wall;
Do not award marks for a diagram with only the ventricles or atria.
However, it is not necessary to show the cordae tendinae.
IB Exam Question
4. Explain the relationship between the structure
and function of arteries, veins and capillaries.
(8 marks)
([3 max] for information on arteries)
thick wall / elastic fibres to help withstand the high(er) pressure;
outer fibrous coat prevents artery from rupturing under the high
pressures;
valves in aorta and pulmonary artery to prevent back flow into
ventricles in diastole;
layers of (smooth) muscle to allow arteries to contract / elastic recoil;
allows the pressure to be altered (vasoconstriction and vasodilation);
([3 max] for information on veins)
thinner wall (than arteries) since pressure low(er);
very little muscle since not needed for constriction;
valves to prevent back flow between pulses;
([3 max] for information on capillaries)
no muscle / elastic tissue since pressure very low;
endothelial layer one cell thick to allow permeability / diffusion of
chemicals / tissue fluid;
no valves since pressure very low;
IB Exam Question
5. Outline the control of the heartbeat in terms of myogenic
muscle contractions, the role of the pacemaker, nerves, the
medulla of the brain and epinephrine (adrenaline).
The heart beats by itself (myogenic)
SA node (pacemaker) in the heart muscle produces an
electrical signal across nerves throughout walls of atria to
begin cycle
This nerve impulse causes the atria to contract
SA signal reaches atrioventricular (AV) node which delays
the electrical signal
Electrical signal spreads across nerves, causing ventricles to
contract
Atrioventricular valves snap shut
After ventricles are emptied, semilunar valves close
Under certain circumstances, adrenaline carries messages
from the brain to pacemaker telling the pacemaker to speed
up the beating of the heart
IB Exam Question
6. State four substances that are
transported by blood.
(4 marks)
Nutrients
Oxygen
Carbon dioxide
Hormones
Antibodies
Urea
Heat