B1 OCR

B1 OCR

1. Diet and Exersize

   • Blood pressure has 2 readings: diastolic and systolic, in mmHg
     • Smoking, a high alcohol intake and a diet rich in saturated fats and salt increase blood pressure
       • High blood pressure can damage the brain (stroke) and kidneys
   • Being fit is the ability to do exersize, being healthy is being free from disease
   • A balanced diet will vary according to age, gender, activity, religion or personal choice

2. Drugs and Disease

   • Harmful drugs are classified as class A, B and C. Class A being the most harmful
     • Depressant and stimulant drugs affect the nervous system by affecting the transmission across synapses
       • High levels of alcohol can cause cirrhosis of the liver
   • Immunisation protects against certain diseases by using harmless pathogens
   • Changes in the lifestyle can reduce the risk of certain cancers
   • The mosquito is the vector that carries malaria
     • Plasmodium is the pathogen that causes malaria. It is a parasite and humans are its host

3. Homeostatis and Plant Hormones

   • Homeostatis is maintaining a constant internal environment
   • Vasodilation and vasconstriction control heat transfer from the body
     • Auxins are involved in phototropism (response to light) and geotropism (response to gravity)
       • A spinal reflex involves a receptor, sensory, relay and motor neurones and an effector
   • Auxins are a group of plant hormones. They cause shoot curvature by cell elongation
     • The hormone insulin controls blood sugar levels. It converts excess blood glucose into glycogen
       • Automatic systems in the body keep water, temperature and carbon dioxide levels constant

4. The Nervous System

   • Light rays are refracted as they pass through the corneas and lens
   • Monocular vision has a wider field of view but poorer distance judgement than binocular vision
     • Long and short sight is caused by the eyeball or lens being the wrong shape
     • The eye accommodates by altering the shape of the lens
   • A nerve impulse travels along the axon of a neurone
     • A neurotransmitter substance diffuses across a synapse, so the nerve impulse can pass to the next neurone
       • A spinal reflex involves a receptor, relay, sensory and motor neurone and an effector

5. Variation and Inheritance

   • Inherited disorders are cause by faulty alleles
     • Most faulty alleles are recessive
   • Dominant alleles are expressed if present, recessive alleles are expressed in the absence of a dominant allele
     • Alleles are different versions of the same gene
   • Being homozygous is having 2 identical alleles, being heterozygous is having two different alleles
   • Human body cells have 23 pairs of chromasomes
     • Sex is determined by sex chromosomes, XX in female, XY in male