Monday, March 17, 2014
Friday, March 14, 2014
Muscles work by getting shorter. We say that they contract, and the process is called contraction.
Muscles are attached to bones by strong tendons. When a muscle contracts, it pulls on the bone, and the bone can move if it is part of a joint.
Muscles can only pull and cannot push. This would be a problem if a joint was controlled by just one muscle. As soon as the muscle had contracted and pulled on a bone, that would be it, with no way to move the bone back again. The problem is solved by having muscles in pairs, called antagonistic muscles.
Biceps and triceps
Thelets our forearm move up or down. It is controlled by two muscles, the biceps on the front of the , and the triceps on the back of the upper arm. The biceps and the triceps are antagonistic muscles.
- when thecontracts, the forearm moves up
- when the triceps muscle contracts, the forearm moves down.
This solves the problem. To lift the forearm, the biceps contracts and the triceps relaxes. To lower the forearm again, the triceps contracts and the biceps relax.
|Muscles in the arm|
Note to Students: Revise all the work you have done, there will be a TEST on Monday. BE PREPARED!
Wednesday, March 12, 2014
This page is about the joints in the skeleton that allow movement.
If two bones just moved against each other, they would eventually wear away. This can happen in people who have a disease called arthritis. To stop this happening, the ends of the bones in a joint are covered with a tough, smooth substance called cartilage. This is kept slippery by. Tough ligaments join the two bones in the joint and stop it .
The diagram shows theof a joint.
Different types of joint allow different types of movement.
- Ball and socket joints allow movement in more directions. Hip and shoulder joints are ball and socket joints.
The bones cannot move on their own - they need muscles for this to happen.
Monday, March 10, 2014
Why do we need a skeleton?
Our skeleton is made of more than 200 bones. Calcium and other minerals make the bone strong but slightly flexible. Bone is a living tissue with a blood supply. It is constantly being dissolved and laid down, and it can repair itself if a bone is broken. Exercise and aare important for a healthy skeleton.
The skeleton has three main functions:
- to support the body
- to protect some of the vital organs of the body
- to help the body move.
The skeleton supports the body. For example, without a backbone we would not be able to stay upright.
Here are some examples of what the skeleton protects:
- the skull protects the brain
- the ribcage protects the heart and lungs
- the backbone protects the.
Some bones in the skeleton are joined rigidly together and cannot move against each other. Bones in the skull are joined like this. Other bones are joined to each other by. Muscles are needed to move bones attached by joints
Friday, March 7, 2014
We need to get oxygen from the air into the blood, and we need to remove wastefrom the blood into the air. Moving gases like this is called gas exchange. The alveoli are adapted to make gas exchange in lungs happen easily and efficiently.
Here are some features of the alveoli that allow this:
- they give the lungs a really big
- they have moist, thin walls (just one cell thick)
- they have a lot of tinycalled capillaries.
The gases move by diffusion from where they have ato where they have a low concentration:
- Oxygen diffuses from the air in the alveoli into the blood.
- Carbon dioxide diffuses from the blood into the air in the alveoli
Wednesday, March 5, 2014
The respiratory system
Thecontains the organs that allow us to get the oxygen we need and to remove the waste carbon dioxide we don't need. It contains these parts:
- tubes leading from the lungs to the mouth and nose
- various structures in the chest that allow air to move in and out of the lungs.
Movements of the ribs, rib muscles and diaphragm allow air into and out of the lungs. Take care - this is called breathing or ventilation, not respiration. When we breathe in, we inhale. When we breathe out, we exhale.
|Parts of the respiratory system|
Each bronchus divides further in the lungs into smaller tubes called bronchioles. At the end of each bronchiole, there is a group of tiny air sacs. These air sacs have bulges called alveoli to increase their.
Monday, March 3, 2014
Respiration is a chemical reaction that happens in all living cells. It is the way that energy is released from glucose, for our cells to use to keep us functioning.
Remember that respiration is not the same as breathing (which is properly called ventilation).
The glucose and oxygen react together in the cells toand water. The reaction is called because oxygen from the air is needed for it to work.
Here is the word equation for aerobic respiration:
glucose + oxygen →+ water (+ energy)
(Energy is released in the reaction. We show it in brackets in the equation because energy is not a substance.)
Now we will look at how glucose and oxygen get to the cells so that respiration can take place and how we get rid of the carbon dioxide.
Glucose from food to cells
Glucose is a type of carbohydrate, obtained through digestion of the food we eat. Digestion breaks food down into. These can be absorbed across the wall of the small intestine into the bloodstream.
Glucose is carried round the body dissolved in, the pale yellow liquid part of our blood. The dissolved glucose can diffuse into the cells of the body from the capillaries. Once in the cell glucose can be used in respiration.
Oxygen from the air to cells
When we breathe in oxygen enters the small air sacs, called alveoli, in the lungs. Oxygen diffuses from there into the bloodstream.
Oxygen is not carried in the plasma, but is carried by the red blood cells. These contain a red substance called haemoglobin, which joins onto oxygen and carries it around the body in the blood, then lets it go when necessary. Like glucose, oxygen can diffuse into cells from the capillaries.
Red blood cells carry oxygen around the body
Carbon dioxide from cells to the air
The carbon dioxide produced during respiration diffuses out of the cells and into the blood plasma. The blood carries it to the lungs. It then diffuses across the walls of the alveoli and into the air, ready to be exhaled.