- At one time people believed their emotions came from their hearts because the heart beats faster when a person is scared or excited.

- We now know that emotions come from the brain and that the brain controls the heart.

- The circulatory system is the transport system of the body and has four major functions:

To transport oxygen and carbon dioxide around the bodyTo distribute nutrients and transport wasteTo maintain body temperatureTo circulate hormones

The roles of the circulatory system

Our circulatory system is a “closed” system

“Closed” system “Open” system

Our circulatory system is a “complete, double” system

Oxygenated blood De-oxygenated blood Mixed blood

complete, single incomplete, double complete, double

Major components of the Circulatory System

STRUCTURE and FUNCTION

The circulatory system is made up of 3 components:

a)The heart (a pump) – that pushes blood through the vesselsb)Blood vesselsc)A fluid in which materials are transported (i.e. blood)

heart

blood vessels

blood

Major components of the Circulatory System

heart

blood

blood vessels

- No body cell is farther than 2 cells away from a blood vessel that can deliver what that cell needs to survive.

- There are 96,000 km of blood vessels in your body that are responsible for delivering the required materials to 100 trillion cells.

- The heart beats, on average, 72x per minute from the beginning of life until death.

Organization of the Circulatory System

The circulatory system is broken down into 2 main circuits:

a) The Pulmonary circuit – blood vessels that carry blood to the lungs where it picks up oxygen and then back to the heart.

b) The Systemic circuit – blood vessels that carry oxygen rich blood to the body tissues and deoxygenated blood back to the heart.

pulmonary

systemic

systemic

1. The heart is really a double pump separated in the middle by a wall called a septum.

septum

right lung left lung

neck and head

trunk and legs

2. The heart consists of 4 chambers. The chambers closer to the top of each side are called atriums, the chambers closer to the bottom are called ventricles.

3. The left side of the heart receives oxygen-rich blood from the lungs and pumps it to the body.

4. The right side of the heart receives deoxygenated blood back from the body and pumps it to the lungs to pick up more oxygen.

Vena cava

Vena cava

The Heart

Vein Artery

Arteriole

Venule

Capillary

blood exchange in the capillaries

Blood from heart blood going to heartO2 CO2

Blood vessels

a) Arteries: blood vessels that carry blood away from the heart. thick walls of muscular layers largest is the aorta that leads directly from the left ventricle into many arteries that carry blood around the body.

b) Veins: blood vessels that carry blood towards the heart. veins have thinner walls than arteries and contain valves to prevent back flow of blood (i.e. so blood can be pumped against gravity). major veins are the vena cava’s that carry deoxygenated blood to the right side of the heart.

c) Capillaries: very small blood vessels, red blood cells must travel single-file, gases exchange across the walls of capillaries and into the surrounding tissues.

Blood vessels

Blood components The average adult has about 5L of blood. Blood is 55% liquid, called plasma and 45% cells (red blood cells,

white blood cells and platelets)

Blood component

Diagram Function

Plasma Allow cells to easily travel through vessels

Red blood cells(erythrocytes)

Carry O2 to the cells, and carry CO2 from the cells to the lungs to be exhaled

White blood cells(leukocytes)

Act as your immune system, circulate through the body engulfing harmful particles

Platelets Platelets + red blood cells join and form clots

Your body is constantly fighting to maintain “things” within normal levels in the body.

1.Role of the Nervous System: Sensors in your brain detect when blood oxygen levels fall below normal levels (i.e. if you are exercising). Your brain then sends a signal to your heart to beat faster and distribute more oxygen to the cells of your body.

2.Role of the Endocrine System: During stressful situations your body releases hormones such as adrenaline. Adrenaline prepares your body for the “flight or fight” response by increasing your heart rate which provides more oxygen to your cells and sending blood to your muscles where it is needed.

The Homeostasis regulation of the cardiovascular system

A blood cell travels from ….

superior vena cava

inferior vena cava

right atrium

right ventricle

right pulmonary veinleft pulmonary vein

left pulmonary arteryright pulmonary artery

left atrium

left ventricle

aorta

Let’s take a closer look at the heart

What causes the heart to contract regularly? More parts of the heart: ….

Sinoatrial (S.A.) node

Atrio-ventricular (A.V.) node

Semi-lunar valves

A.V. valves(tricuspid valves)

A.V. valves(bicuspid valves)

More parts of the heart: ….

superior vena cava

inferior vena cava

right atrium

right ventricle

right pulmonary veinleft pulmonary vein

left pulmonary arteryright pulmonary artery

left atrium

left ventricle

aorta

Sinoatrial (S.A.) node

Atrio-ventricular (A.V.) node

Semi-lunar valves

A.V. valves(tricuspid valves)

A.V. valves(bicuspid valves)

What causes the heart to contract regularly?

3. More parts of the heart :

Sinoatrial (S.A.) Node: is the pace maker of the heart. Beats are regulated at about 72 beats/min. S.A. node activity is triggered by the swelling of the atrial walls. Its job is to trigger the A.V. node.

Atriaventricle (A.V.) Node: is another pace maker of the heart. Its job is to prepare the fibres in the septum to contract the Right and Left Ventricles.

Valves:There are 2 types of valves in the heart. One is the atrioventricular set of valves,

located between the atria and ventricles. These valves open when the atria contract, filling the ventricles. Once the ventricles have filled, the atrioventricular valves snap shut, this prevents the backflow of blood to the atria.

The second set of valves in the heart is the semi-lunar valves. The semilunar valves open when the ventricles contract. After the ventricles have contracted (the right sending blood to the pulmonary artery, and the left sending blood into the aorta) the semilunar valves shut. This prevents the backflow of blood into the ventricles.

4. “Lubb-dubb”: Heart sound ‘lubb dubb’ is the shutting of the 2 sets of valves respectively.

http://www.sciencehelpdesk.com/unit/bg3/2 - The work of the heart (I)

5. Blood pressure: your pulse is what you feel as a surge of blood passes through your arteries. This surge of blood stretches the artery open, causing a pressure. This pressure of blood, as it is pumped out of the left ventricle into the artery is called Systolic pressure. When there is no surge of blood pumped into the artery, the artery is in a state of relaxation because it is not being stretched open. The pressure in the artery walls in this state of relaxation is called Diastolic pressure.

What is happening in the heart during Diastolic Pressure?The atria + ventricles are filling with blood.

Blood pressure is measured in mm of Hg, and is measured using a sphygmomanometer. Blood pressure is written as systolic pressure over diastolic pressure. Normal blood pressure is 120/80.