Chapter 5: Blood and Circulation

As  the blood travels around, it collects materials from some places and unloads them in others. In mammels, blood transports:

•  Oxygen from the lungs to all other parts of the body
•  Carbon Dioxide from all parts of the body to the lungs
•  Nutrients from the gut to all parts of the body 
•  Urea from the liver to the kidneys

Hormones, Antibodies and many other substances are transported by the blood. It also distributes heat around the body.

Single-celled organisms DO NOT have a circulatory system because materials can move around easily without one 

Single-celled organisms DO NOT have a circulatory system because materials can move around easily without one.

One-celled organisms obtain oxygen through the surface membrane of the cell ----- THE AREA OF THE CELL'S SURFACE DETERMINES HOW MUCH OXYGEN THE ORGANISM CAN GET!

Single-celled organisms = high surface area to vol. ratio

Mutli-celled organisms = lower surface area to vol. ratio

Main function of a Circ. Sys. in an animal is to transport oxygen.

• In single circulatory systems the blood is pumped from the heart to the gas exchange organ and then directly to the rest of the body
• In double circulatory systems the blood is pumped from the heart to the gas exchange organ, back to the heart and then on to the rest of the body.

There are two distinct parts to a double circulation:

• The Pulmonary circulation, in which blood is circulate through the lungs where it is oxygenated

• The systemic circulation, in which blood is circulated through all other parts of the body where it unloads its oxygen

The human circulatory consists of :

• the HEART - which is the pump
• BLOOD VESSELS - These carry the blood around the body, ARTERIES carry blood AWAY from the heart and towards otehr organs, VEINS carry blood towards the heart and away from the other organs. CAPILLARIES carry blood through organs
• BLOOD - the transport medium

Parts of the Heart:

• vena cava (superior)
• semi-lunar valves
• left and right atrium
• tricuspid valve
• vena cava (inferior)
• aorta
• pulmonary artery
• pulmonary vein
• bicuspid (mitral valve)
• left and right ventricle

When a chamber of the heart is contracting, we say it is in Systole. When it is relaxing, we say it is in Diastole.

• The heart is divided into a left and right side by the septium
• the right ventricle pumps blood only to the lungs while the left ventricle pumps blood to the whole body
• valves ensure that blood can flow only in one direction through the heart
• The walls of the atria are thin + can be stretched to recieve blood as it returns to the heart but can contract with enough force to push blood through the bicuspid and tricuspid valves into the ventricles.

• Valves ensure that blood can flow only in one direction through the heart.
• The walls of the heart are made of cardia muscle which can contract and then relax continuously, without becoming fatigued.
• the cardiac muscle has its own blood supply - The coronary circulation. Blood reaches the muscle via coronary arteries. These carry blood to capillaries that supply the heart muscle with oxygen and nutrients. Blood is returned to the right atrium via coronary veins

Blood is moved through the heart by a series of contractions and relaxations of cardiac muscle in the walls of the 4 chambers. These events form the cardiac cycle

normal HR = 70 bpm

exercise = anerobic respiration = higher Oxygen demand = Higher heart rate

the changes in out heart rate are brought about by nerve impulses from the Medulla.

• Arteries carry blood AWAY from the heart
• Veins carry blood from the organs back towards the heart
• Capillaries carry blood through organs