IGCSE Edexcel Biology: structure of heart + circulation system

Name structures 1,2,5

1 — aorta

2 — superior vena cava

5 — right atrium

Name structures 6,7,8

6 — tricuspid valve

7 — right ventricle

8 — inferior vena cava (same part as superior vena cava)

Name structures 9,10,11

9 — pulmonary artery

10 — pulmonary vein

11 — left atrium

Name structures 12,13,14,16

12 — bicuspid valve

13 — semilunar valve

14 — left ventricle

16 — septum

Show the pathway of blood. El diagram de la miss Kitchen

What is meant by the term double circulatory system? In which organisms?

In one complete cycle, blood is pumped into the heart twice (blood pumped from heart → gas exchange organ (lung) → back to heart → rest of body) It invokes 2 circulation:

• Pulmonary (circulation between lung and heart. From deoxygenated to oxygenated)

• Systemic (circulation between heart and body. From oxygenated to deoxygenated)

Humans and other mammals

What is meant by the single circulatory system? Which organisms?

A system where the blood is pumped from the heart to the gas exchange organ, and then directly to the rest of the body.

Fish

What type of circulatory system is more efficient?

Double circulatory system

From textbook: it is more efficient because heart pumps twice, so higher pressure maintained = blood travels quickly to organs (O2).

Not in textbook: It prevents oxygenated and deoxygenated blood from mixing which increases the efficiency of oxygen transport and energy production in the body. And helps to alter the pressure from the different chambers of the heart (both circulation systemic and pulmonary can be controlled independently)

The human circulatory system comprises

• The heart - pump

• Blood vessels - carry blood around body

• Blood - the transport medium

Which side does oxygenated (high O2) blood enter? What is the destination? Why kind of circulation is this + path?

Left side of the heart → body cells

Systemic circulation:

• Left side of the heart — oxygenated blood through atrium → ventricle → aorta → rest of the body cells → returns deoxygenated blood through vena cava to right side of heart

Which side does deoxygenated blood (high CO2) enter? What is the destination? Why kind of circulation is this + path?

Right side of heart → lungs

Pulmonary circulation

• Right side of heart — deoxygenated blood through atrium → ventricle → pulmonary artery → lungs → oxygenated blood returns to left side heart through pulmonary vein.

How is the left ventricle different from the right? Why? (4)

The left ventricle has a thicker (1) muscle (1) wall than the right ventricle as it has to pump blood at high pressure (1) around the entire body (1).

The right ventricle is pumping blood at a lower pressure to the lungs prevents damage to capillaries in the lungs and lungs are closer.

How are the walls of the atria? What does this allow the atria to do?

The walls of the atria are thin. This allows them to be stretched to receive blood as it returns to the heart, but it can contract with enough force to push blood through the bicuspid and tricuspid valves into the ventricles

Describe how the blood in the left side of the heart differs from the blood in the right side (2)

- More oxygen/oxygenated blood
- Higher pressure

What is the septum + its function? What would happen if there was no septum?

It is a muscle wall that separates both sides of the heart so that oxygenated blood doesn't mix with deoxygenated blood.

Mixing of theses two will decrease the efficency of blood to carry oxygen and our organs won't be able to work properly.

What is the function of the valves?

They prevent blood from flowing backwards.

Describe what would happen to the flow of blood in the left side of the heart if the bicuspid valve did not function effectively (2)

• Flow of blood cannot pass to ventricle (goes backwards)

• Less oxygenated blood pumped to body

Blood is pumped ____ the heart in veins and ____ from the heart in arteries.

towards

away (arteries away)

The coronary arteries supply the ____ of the heart with oxygenated blood. Why?

Cardiac muscle tissue.

As the heart is a muscle it needs constant supply of oxygen (and glucose) for aerobic respiration to release energy to allow continued muscle contraction. If not enough oxygen is supplied, it can damage or result in the death of the heart muscle.

How are the cardiac muscles different from other muscles in our body?

They can contract and relax continuously be without becoming fatigued

What is the artery connected to the left ventricle? What is the vein connected to the right atrium called?

Aorta — where blood flows away from the heart TOWARDS the body cells.

Vena cava — where blood flows from body cells INTO the right atrium.

Describe the pathway of DEOXYGENATED blood through the heart.

- Deoxygenated blood coming from the body flows through the vena cava and into the right atrium.

- The atrium contracts and the blood is forced through the tricuspid valve into the right ventricle.

- The ventricle contracts and the blood is pushed through the semilunar valve into the pulmonary artery.

- The blood travels to the lungs and moves through the capillaries past the alveoli where gas exchange takes place

- Low pressure blood flow on this side of the heart prevents damage to the capillaries in the lungs.

Describe the pathway of OXYGENATED blood through the heart.

- Oxygenated blood returns via the pulmonary vein to the left atrium.

- The atrium contracts and forces the blood through the bicuspid valve into the left ventricle.

- The ventricle contracts and the blood is forced through the semilunar valve and out through the aorta.

- Thicker muscle walls of the left ventricle produce a high enough pressure for the blood to travel around the whole body.

NOTE: remember both atria contract at the same time and both ventricles contract at the same time.

What are the three main types of blood vessels?

Arteries, veins, capillaries

What are the key features of arteries?

- Carry blood away from the heart

- Carry oxygenated blood (except the pulmonary artery)

- Have thick muscular walls containing elastic tissue

- Have a narrow lumen

(Blood flows through at a fast speed)?

- Does not have valves

How is the structure of an artery adapted to its function?

- Narrow lumen creates high pressure

- Thick muscular walls containing elastic fibres stops from bursting under high pressure blood and maintains the blood pressure as it recoils after the blood has passed through

- Textbook: Have thick muscular walls (helps control flow of blood by dilating and constricting vessels) containing elastic tissue allowing them to stretch and recoil (maintain high blood pressure)

What are the key features of veins?

- Carry blood towards the heart

- Carry deoxygenated blood (except the pulmonary vein)

- Have thin walls

- Have a large lumen

- Contain valves

(Blood flows through at a slow speed) ?

How is the structure of a vein adapted to its function?

- A large lumen reduces resistance to blood flow under low pressure.

- Valves prevent the backflow of blood as it is under low pressure. (Backflow of blood towards the feet al parecer)

What are the key features of capillaries?

- Carry blood at low pressure within tissues

- Carry both oxygenated and deoxygenated blood

- Very narrow

- Have walls that are one cell thick + 'leaky' walls

- Speed of blood flow is slow

How is the structure of a capillary adapted to its function?

- Very small/narrow so are close to the tissues so short diffusion distance for fast diffusion of glucose, CO2, urea (in liver), etc

- Capillaries have one cell thick walls (short diffusion distance) to allow fast diffusion of glucose, oxygen, CO2, etc

- No need to learn: The 'leaky' walls allow blood plasma to leak out and tissue fluid bathes cells delivering glucose, oxygen, CO2, etc.

Circulatory system function + what does it consist of?

(aka cardiovascular system) This system works as the transportation highway for the body. It consists of the heart, blood, and blood vessels.

It transports substances such as oxygen, carbon dioxide, and nutrients (e.g glucose) in the body.

What is the pathway of blood in the circulatory system?

- Oxygenated blood is carried away from heart towards organs in arteries.

- These narrow into capillaries as they pass through the organ.

- In the organ, cells use up the oxygen in the blood for respiration and produce waste product CO2.

- The capillaries widen into veins as they move towards the heart.

- Deoxygenated blood is carried back towards the heart in veins.

What other network is there? What does it do?

Network of lymphatic vessels collect all the excess tissue fluid that leaks out of the capillaries and delivers it back to the circulatory system.

What are the main blood vessels of the circulatory system?

Heart

Towards organ: coronary artery

Away from organ: coronary vein

Lung

Towards organ: pulmonary artery

Away from organ: pulmonary vein

Kidney (removes urea)

Towards organ: renal artery

Away from organ: renal vein

Liver (produces urea)

Towards organ: hepatic artery

Away from organ: hepatic vein

What is heart rate measured in?

Beats per minute (bpm)

What is the pacemaker + its function? How does it work?

Group of cells in the right atrium that coordinate the contraction of the heart muscle and regulate the heart rate (natural resting heart rate is also controlled by this).

Send out electrical impulses which initiate contraction in the cardiac muscle.

Why does the heart pump blood?

To supply oxygen and glucose and remove respiratory waste (CO2).

What happens when we exercise?

• Our muscle cells produce more CO2 in aerobic respiration

• Receptors in aorta and carotid artery detect this increase and send electrical signals(nerve impulses) to the medulla

• Medulla responds by sending nerve impulses along the accelerator nerve (when CO2 levels back to normal, medulla responds by sending nerve impulses along the deceleration nerve)

• Accelerator nerve increases heart rate: heart beats with more force and so increases blood pressure

- An increase supply of oxygen and glucose (and waste removal) in muscle cells is needed.

- To release more energy in aerobic respiration for muscle contractions.

- This causes an increase in heart rate.

How does the nervous system respond to the increase respiration/demand for oxygen and glucose?

- Heart rate increases (number of beats per minute increases) to deliver oxygen and glucose more frequently.

- Volume of blood pumped per minute increase to supply larger amounts of oxygen and glucose.

Why does the heart rate remain high for a period of time after doing intense excercise?

Oxygen is required in the muscles to break down the lactic acid from anaerobic respiration into CO2 and water.
Oxygen debt.

Why does heart rate increase under the influence of adrenaline?

Adrenaline binds to specific receptors in the heart. This causes the cardiac muscle to contract more frequently and with more force, so heart rate increases and the heart pumps more blood.

This increases oxygen supply to muscles, getting the body ready for action.

It is part of the 'fight or flight' response to provide more oxygen to the muscles.

Adrenaline stimulates the liver to break down glycogen into glucose to provide quick source of energy.

Design an experiment for the effect of exercise on breathing rate

C - exercise/no exercise

O - same age/sex people

R - repeat 3 times to ensure results are reliable

M - measure BREATHS (not beats) per minute

M - before and after exercise S - same duration of exercise

S - same type of exercise (intensity, all Zumba, all running, etc)