Biology B1 OCR Gateway

High or low bp can cause health problems;

Too high - blood vessels bursting leading to kidney damage, brain damage or strokes.
Too low- causes poor circulation which can lead to fainting and dizziness.

Carbon monoxide - combines with haemolytic in red blood cells, decreasing the oxygen carrying capacity of the blood. To make up for this, the heart rate has to increase so the muscles can get the oxygen they require. This increases bp.

Nicotine - a stimulant drug that increases the heart rate consequently increasing bp.

Saturated fats can cause a build up of cholesterol.

• Cholesterol is a fatty substance carried in the blood.
• Cholesterol is essential for making things like cell membranes, but too much can lead to a build up in your arteries.
• Eating a diet high in sat fats has been linked to high cholesterol levels in the blood
• This forms plaque in the artery walls which narrows them
• plaques can restrict blood flow which can lead to a heart attack.
  High salt levels can increase bp
• lots of salt can increase bp.
• a high bp increases the risk of damage to the arteries.
• this damage can encourage the formation of plaques in artery walls
• this can lead to a heart attack.
  A thrombosis is a blood clot
• if a thrombosis occurs alongside narrow arteries then the oxygen supply in the blood to the heart will be restricted completely.
• this causes a heart attack.

White blood cells can do three things when they come across a foreign body;
1. Consume them - WBC can engulf foreign cells and diet them.
2. Produce antitoxins - they counteract the effects of toxins produced by invading pathogens.
3. Producing antibodies - each pathogen has unique antigens (surface molecules) when WBC come across a foreign antigen it will start to produce proteins called antibodies. Antibodies lock onto the invading cell and kill them. These are then produced rapidly and some remain as memory cells. Memory cells are remember the antigen and kill it if the body ever becomes infected again. This person is then naturally immune.

The cornea - refracts light into eye!

The iris - controls how much light enters the pupil!

The lens - refracts light focusing it onto retina!

The retina - light sensitive part covered in rods and cones (they detect light)!

Rods - sensitive in dim light not to colours!

Cones - sensitive to colours but not good in dim light!
(red-green colour blindness is due to a lack of specialised come cells)

The optic nerve - carries impulses from receptors to the brain!

The lens is elastic allowing it to change shape so it can focus light - accommodation

Distant objects - ciliary muscles relax.
suspensory ligaments tighten.

This allows the lens to be a less rounded shape so less refraction.

Near objects - ciliary muscles contracts
Suspensory ligaments slacken

This allows the lens to be a more rounded shape, refracting more light.

Longsightedness - unable to focus on close objects.
Lens is wrong shape and doesn't refract the light enough.
Eyeball is too short.
The images of close objects are brought into focus behind the retina.
Convex lenses.

Shortsightedness - unable to focus on distant objects
Lens refracts the light too much.
Eyeball is too long.
The images are brought into focus in front of the retina.
Concave lenses or corneal laser surgery.