B5
By Claire Hagger…read more

Bones and Cartilage
· The job of the skeleton is to support and protect vital
organs, there are two types; internal and external.
· Bones are made from living cells that grow and repair
themselves. Long bones are hollow which makes them
lighter and movements become more effective.
· Blood vessels deposit calcium and phosphorus into the
cartilage to turn it into bone= ossification.
· Cartilage and bone are living tissue so can become
infected.
· Elderly people sometimes have broken bones more
due to osteoporosis which means there is a lack of
calcium making bones softer and more brittle.…read more

Joints and Muscles
· Synovial joints are held together by ligaments (high
tensile strength and elastic).
· Ends of bones are covered in cartilage as it stops the
bones rubbing together.
· Synovial membrane releases synovial fluid to lubricate
joints, allowing them to move more easily.
· Ball and socket and hinge are both types of joints.
· Bones are attached to muscles using tendons.
· Muscles come in pairs (antagonistic) because when
one muscle contracts it moves the joint in one
direction and when the other muscle contracts it
moves the joint in the opposite direction.…read more

Circulatory System
· In single celled organisms, materials can just diffuse in and
out of the cells, but in larger animals this would be too slow
so they require a blood circulatory system.
· Animals with gills have a single circulatory system which
means their heart has two chambers- one to receive blood
and the other to pump around the body.
· Other mammals have a double circulatory system which
means that the heart has four chambers in order to keep
the blood flowing at a high pressure.
· In single circulatory systems, the pressure is quite low
whereas in double circulatory systems, the pressure is high
which means that materials can be transported around the
body more quickly.…read more

The Cardiac Cycle and Circulation
· The sequence of events in one complete heartbeat is the cardiac cycle.
· First, the blood flows into the two atria. The atrio-ventricular valves are
open but the semilunar valves are closed.
· Then, the atria contract, pushing the blood into the ventricles. The valves
remain the same as before.
· The ventricles then contract, forcing blood into the aorta and the
pulmonary artery. The atrio-venticular valves close automatically and the
semilunar valves open.
· The blood then flows along the arteries, the atria fill again and the whole
cycle repeats.
· Galen- thought arterial blood was made by the heart, whilst blood in the
veins was made by the liver.
· Harvey- showed that the heart valves stopped the back flow of blood, the
heart is a pump, pulse is caused by the heart pumping blood into the
arteries and the same blood was circulated around the body.…read more

Heart Rate
· Hormones and exercise can affect your heart rate as
your heart pumps faster to deliver more oxygenated
blood to the muscles.
· Pacemakers are a small group of cells that send an
electric current to the heart telling it to contract.
· The sino-atrial node (SAN) stimulates first in order to
make the atria contract. The atrio-venticular node
(AVN) then stimulates to make the ventricles contract.
· Doctors can measure the heart function by doing an
electrocardiogram (ECG) which shows the electrical
activity in the heart. Or they can do an echocardiogram
which is an ultrasound of the heart.…read more