IB Biology Review Circulatory System Why do we need blood

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IB Biology Review

• Circulatory System

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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!

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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

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A Closer Look at the Heart
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Identify the structures of the heart.
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Be able to draw something like this.
Pulmonary veins
Atrioventricular valves
Semilunar valves
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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

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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!

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Which arteries help out the heart?

• Coronary arteries supply heart muscle with
• Oxygen
• Nutrients

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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

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Composition of Blood

• Blood is made of
• Plasma
• Erythrocytes (red blood cells)
• Leucocytes (white blood cells)
• Phagocytes
• Lymphocytes
• Platelets

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1. Which vessel carries deoxygenated blood?
(1 mark)
IB Exam Question

• A. The pulmonary artery
• B. The coronary artery
• C. The aorta
• D. The pulmonary vein
• Correct answer A

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2. What is the function of the right ventricle?
(1 mark)
IB Exam Question

• A. Pumping blood into the pulmonary artery
• B. Pumping blood into the pulmonary vein
• C. Pumping blood into the aorta
• D. Pumping blood into the coronary artery
• Correct answer A

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3. Draw a labelled diagram to show the internal
structure of the heart.
(6 marks)
IB Exam Question

• 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.

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4. Explain the relationship between the structure
and function of arteries, veins and capillaries.

(8 marks)
IB Exam Question

• (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

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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).
IB Exam Question

• 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

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6. State four substances that are transported by
blood. (4 marks)
IB Exam Question

• Nutrients
• Oxygen
• Carbon dioxide
• Hormones
• Antibodies
• Urea
• Heat

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