Biology Unit 1a

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  • Created by: Zoe
  • Created on: 01-04-13 16:22

Diet and Metabolic Rate

A Balanced diet keeps you healthy

It must provide energy you need

Must contain enough: Carbs to release energy, fats to keep warm and release energy, protein for growth and cell replacement, fibre for digestive system and vitamins and minerals

energy is needed to fuel your metabolism, the speed is called your metabolic rate

Metabolic rate varies because of: Age,gender,Inherited factors, Proportion of muscle to fat and amount of excercise

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Factors Affecting Health

Health is affected by having an unblanced diet

Eating to much can lead to obesity

What can lead to obesity: 1. Excess carbs or fats  2. Bad diet, overeacting and lack of excercise

Health problems such as: Arthritis, type 2 diabetes, high blood pressure and heart disease can be caused by obesity

Not enough exercise affects your health

Excercise makes you healthier, decreases the amount of stored fats and builds muscle to boost metabolic rate

Inherited factors can affect metabolic rate e.g underactive thyroid gland can lower metabolic rate and cause obesity. Also inherited factors can affect your blood cholesterol level e.g the factor can increase blood cholestrol levels increasing the risk of heart disease

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Fighting Disease

Two main types of Pathogen:Bacteria and Viruses

Bacteria- very small living cells that make you feel ill by damaging cells and producing toxins

Viruses- Arent cells they replicate themselves and take over your cells using your cell to produce copies od themselves. The cell will burst releasing the new viruses the damage makes you feel ill

Your bodies defence system

  • Your skin, hairs and mucus in your respiratory tract stop viruses getting inside your body
  • Small fragments of cells help clot the blood to seal a wound
  • your immune system- white blood cells consume viruses and digest them, produce antibodies which latch onto the foreign antigen and kill it
  • Producing antitoxins to counteract toxins produced by the invading bacteria
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Fighting disease- Vaccinations

Vaccination- Protects from future Infections

If you are infected by a new microorganism, white blood cells learn how to deal with it but the time it takes can make you ill

Vacinnations inject small amounts of dead microorganism that carry antigens which cause your body to produce antibodies which attack them If live microorganisms appear after that, the white blood cells rapdily mass produce antibodies to kill off the pathogen


  • Controlled lots of infectious diseases such as polio, measles,rubella,whopping cough,mumps and tetanus
  • epidemics can be prevented


  • Dont always work
  • can have a bad reaction to a vaccine
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Fighting Disease- Dugs

Some drugs relieve the symptons- others cure the problem

  • Pain Killers- Relive the pain and reduce the symptons

Some drugs do similar things to painkillers, they reduce the symptons without tackling the cause

  • Antibiotics- kill the bacteria causeing the problem without killing cells but they dont destroy virsuses like flu

Bacteria can become Resistant to Antibiotics

  • Bacteria can mutate causing a resistance to antibiotics
  • Some Bacteria in different Infections might be resistant to Antibiotics
  • The individual resistant bacteria will survive and reproduce making the strain increase in size
  • Resistant strains can cause serious infections that antibiotics cant treat
  • To slow down a resistant strain its important doctors dont over prescribe antibiotics
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The Nervous System

Sense Organs Detect Stimuli

Stimulus-A change in your enviroment which you might need to react to. You have 5 different Sense Organs:

  • Eyes
  • Ears
  • Nose
  • Tongue
  • Skin

They all contain different Receptors (groups of cells which are sensitive to a stimulus) They change Stimulus energy into Electrical impulses

A stimulus can be Light,sound,touch,pressure,pain,chemical or a change in position or temperature

The eye is a sense organ- it contains light receptors 

The Ear is a sense Organ-it contains sound receptors

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The Nervous System 2

The Central Nervous system Coordinates a response

  • The central Nervous system (CNS) is where all the sense organs send information, and also where reflexes and actions are coordinated.
  • It consists of the Brain and spinal Cord
  • Neurones (nerve cells) transmit information to and from the CNS
  • Information from the CNS is sent to the effectors

The five sense organs and the receptors that each contain:

  • Eyes: Light Receptors-sensitive to light. These cells have a nucleus,cytoplasm and cell membrane
  • Ears: Sound Receptors- Sensitive to sound & Balance receptors-Sensitive to changes in position
  • Nose:Smell Receptors- Sensitive to chemical stimuli
  • Tongue:Taste Receptors-sensitive to bitter,salt,sweet and sour and savoury tastes
  • Skin: Sensitive to touch,pressure,pain and temperature change
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The Nervous System 3

Sensory Neurons- The Nerve Cells that carry signals as electrical impulses from the receptors in the sense organs to the central nervous system

Relay Neurons- The Nerve cells that carry signals from sensory neurones to motor neurones

Motor Neurons- The nerve cells that carry signals from the central nervous system to the effector muscles or glands

Effectors- Muscles and glands are know as effectors- they respond in different ways. Muscles contract in response to a nervous impulse, whereas glands secrete hormones

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Synapses and Reflexes

Synapses connect Neurones-The connection between two neurones is called a synapse

  • the nerve signal is transferred by chemicals which diffuse across the gap
  • chemicals set off a new electrical signal in the next neurone

Reflexes help prevent Injury

  • They are automatic responses to certain stimuli- e.g if a bright light is shinning in your eye, the pupil automatically gets smaller letting less light in-stopping damage
  • Or if you get a shock your body release adrenaline automatically
  • the passage of information in a reflex is called a reflex arc

The reflex arc goes through the central nervous system

  • Stimulus
  • Stimulation of the pain receptor
  • Impulses travel along the sensory neurone
  • Impulses passed along a relay neurone, via a synapse
  • impulse travel along a motor neurone, via a synapse
  • When impulses reach muslce, it contracts
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Hormones are chemical Messages which travel in the blood to activate target cells

Hormones are chemicals released into the blood. They are then carried in the blood plasms to particular cells in particular places. They control things in organs and cells that need constant adjustment

Hormones are produced in:

  • The Pituitary Gland- It produces hormones including FSH and LH which are involved in the menstrual cycle
  • The Ovaries- Produce Oestrogen

Hormoned and Nerves do similar jobs:

  • Nerves: 1.Very Fast Action 2. Act for a very short time 3. Act on a very Precise Area
  • Hormones: 1.Slower Actions 2.Act for a Long time 3. Act in a more general way
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The Menstrual Cycle

Hormones control the different stages

The three main hormones involved are:

FSH (Follicle-Stimulating Hormone):

  • Produced by the pituitary gland
  • Causes an egg to mature in one of the ovaries
  • Stimulates the ovaries to produse Oestrogen


  • Produced in the ovaries
  • Causes pituitary to produce LH
  • Inhibits the further release of FSH

LH (Luteinising Hormone):

  • Produced by the pituitary gland
  • Stimulates the release of an egg at the middle of the menstrual cycle
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Controlling Fertility-reducing fertility

Hormones can be used to reduce fertility

  • Oestrogen can be used to prevent the release of eggs
  • Progesterone reduces fertility by stimulating the production of thick cervical mucus which pervents the sperm reaching the eggs
  • The pill is an oral contraceptive. It contains high levels of oestrogen and progesterone

Pro's of the pill:

  • 99% effective at preventing pregnancy
  • it reduces the risk of getting some types of cancer


  • It isnt 100% effective
  • Can cause side effects like head aches,nausea,irregular mentrual bleeding
  • doesnt protect against STD's
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Controlling Fertility- Increasing fertility

Hormones can be used to increase fertility

Some women have levels of FSH that are to law to cause their eggs to mature. Meaning no eggs are released

The hormones FSH and LH can be injected by women to stimulate egg release in their ovaries


  • Helps women get pregnant


  • Doesnt always work- might have to do it many times, can be expensive
  • too many eggs could be stimulated, resulting in unexpected multiple pregnancies
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Can help couples have children

IVF (in vitro fertilisation) involves collecting eggs from the womens ovaries and fertilising them in a lab using the man's sperm.These are grown into embryos

Once the embryos are tiny balls of cells, one or two are transferred into the womans uterus to improve the chance of pregnancy

FSH and LH are given before egg collection to stimulate agg production


  • Fertility treatment can give an infertile couple a child


  • Some women have a strong reaction to the hormones e.g vomiting
  • can increase the risk of cancer due to the hormonal treatment
  • Can cause multiple births- risky for mother and baby e.g cause stillbirth, miscarriage
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Plant Hormones

Auxin is a plant growth hormone

Auxin is a plant hormone that controls growth near the tips of shoots and roots

It controls the growth of a plant in response to:

  • Light-Phototropism
  • Gravity-Geotropism
  • mositure

Auxin is produced in the tips and moves backward to stimulate the cell elongation process which occurs in the cells behind the tips.If the tip of a shoot is removed, no auxin is avaliable and the shoot may stop growing.Extra auxin promotes growth in the shoot but inhibits growth in the root

Shoots grow toward light

  • when a shoot is exposed to light more auxin moves to the side in the shade
  • This makes the cells grow faster on the shaded side so the shoot bends towards the light
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Plant Hormones 2

Shoots grow away from gravity

  • If a shoot grows sideways, gravity produces an unequal distribution of auxin in the tip=more auxin on the lower side
  • This causes the lower side to grow faster,bending the shoot upwards

Roots grow towards gravity

  • A root growing sideway=more auxin on the lower side
  • In a root the extra auxin inhibits growth. Meaning the cells on top grow faster bending the root downwards

Roots grow towards moisture

  • more auxin is produced on the side with more moisture. inhibits growth on that side causing the root to bend, towards the moisture
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Plant Hormone- uses in agriculture

Can be extracted and used by people, or artificial version can be made

Weeds in crop fields have broad leaves. Selective  weedkillers are made of plant growth hormones-they only affect broad leaved plants. They disrupt their normal growth patterns which kill them without killing the crops

Plant cuttings wont always grow in soil. By adding root powder which contains auxin, the cutting produces roots rapidly and start growing as new plants. This helps farmers grow clones of good plants very quickly

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Your body needs some things to be kept constant

  • Ion content
  • water content
  • Sugar content
  • Temperature

Ion Content is regualted by the Kidneys

  • Ions are taken into the body in food,then absorbed into the blood
  • If it contains to much of any kind of ion it needs to be removed e.g salt
  • some ions are lost in sweat
  • The kidneys remove excess from the blood through urine

Body temperature is controlled by the brain

  • All enzymes work best at body temperature-37 degrees
  • The brain is sensitive to the blood temperature in the brain, it recieves messages from the skin that provide info about the skin
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Homeostasis 2

Water is lost from the body in various ways

water is taken into the body as food and drink and is lost through:

  • The skin as sweat
  • Via the lungs in breath
  • Via the kidneys as Urine

The balance depends what kind of day it is. For example if its a cold day when you're not excercising you don't sweat a lot compared to a hot day when your excercising you sweat a lot and loss lots more water through your breathe

Blood sugar levels need to be controlled

  • Eating foods containing carbs puts glucose into the blood from the gut
  • metabolism of cells removes glucose from the blood. If a lot of excercise is done much more glucose is removed
  • Insulin helps maintain the right level of glucose in your blood, so cells get a constant supply of energy
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Drugs change your body chemistry

Some of the chemical changes caused by drugs lead to the body becoming addicted and can suffer withdrawal symptons e.g heroin and caffeine are addictive

Drugs can be Medicinal, Recreational or Performance enhancing

  • Medicinal=antibiotics
  • Recreational are for fun.They can be legal or illegal
  • Performance enhancing can improve a persons performance e.g Lance Armstrong

Performance Enhancing drugs have health and ethnical impacts

  • They are taken to make athletes better at sport e.g Lance Armstrong
  • Several different types: Anabolic steriods (increase muscle size) and stimulants (increase heart rate)
  • Some are banned by law or prescription only but all are banded by sporting bodies
  • Ethnic problems against drugs: unfair advantage,may not no the serious health risks
  • Ethnic problems For drugs: Its the athletes own desicion,drug free sport isnt fair to all, differences in training facilities,coaching,equipment ect
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Testing Medicinal drugs

Three Main stages of drug testing: Stage 1:

  • Drugs tested on human cells and tissue in a lab
  • But human cells and tissues arent used to test drugs that affect whole or multiple body systems e.g drug for blood pressure=animal used because of its intact circulatory systerm

Stage 2:

  • Then its tested on live animals to see if it works, find out its toxicity and best dosage
  • It must be tested on twodifferent live animals some think its cruel but others think its the safest way

Stage 3:

  • Tested on human volunteers in clinical trial
  • tested on healthy volunteers to make sure it doesnt have any harmful side effects
  • Then tested on ill people to find the optimum dose, then put into two groups, one given the drug one given a placebo-the doctor can see the drugs affect
  • Clinal trials are double blind- the patients and doctors dont no the effects till the results are gathered
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Recreational Drugs

Recreation Drugs can be legal or illegal

  • Illegal drugs are often put into two classes- soft and hard- Hard drugs are the ones thought to be most addictive
  • Soft drug-cannabis and hard drug- heroin and ecstasy can all cause heart and circulatory system problems

Various reasons why people use recreational drugs:

  • Some use cannabis for enjoyment,relaxation,stress relief,to get stoned or for inspiration
  • Background,personal life problems

Some legal drugs have more of an impact than illegal drugs

  • Smoking causes heart,blood vessel and lung diseases. Tobacco smoke causes cancer and nicotine is addictive
  • Alcohol affects the nervous system,slows down reactions, leads to impaird judgement,poor coordination and unconsciousness, can cause brain damage and liver disease, is addictive
  • Both have economical effects  and affect people directly or indirectly
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