CBSE CLASS 9 CHAPTER 13 NOTES

CHAPTER 13

CBSE SCIENCE
CLASS 9

WHY DO WE FALL ILL?

INTRODUCTION

·     Cells – made of variety of substances – proteins, carbohydrates, fats or lipids & so on

·     A living Cell – dynamic place – many processes takes place

·     Cells – move from place to place; even if it doesn’t move – some repair process takes place in it

 

ACTIVITIES IN OUR BODY

·     Our body – specialized activities takes place

·     Heart – beats

·     Lungs – breathe

·     Kidney – filters Urine

·     Brain – thinks

·     All the activities – interconnected

·     For example: Kidneys – not filtering urine – waste poisonous substances – accumulate – Brain – will not think properly

 

·     For all these activities – we need energy & raw materials – from outside in the form of food

·     Anything that prevents proper functioning of cells & tissues – lead to lack of proper activity of the body

HEALTH & ITS FAILURE

·     Health – defined as ‘Being Well’ or Effective functioning

·     Health – a state of being well enough to function well physically, mentally & socially

 

PERSONAL & COMMUNITY ISSUES BOTH MATTER FOR HEALTH

·     Health – not something that each one of us can achieve entirely on our own

·     Health of all organisms – depend on – surrounding environment

·     Our physical environment – decided by our social environment

·     Example: If there is garbage thrown in our streets & open drainage water lying stagnant – possibility of poor health

·     Therefore,  Public cleanliness – very important – for individual health

·     We need food for good health – food – earned by doing work

·     Therefore, good economic conditions & jobs – needed for individual health

·     We need to be happy – to be truly healthy

·     If we mistreat Each other & are afraid of each other – we cannot be healthy

·     Social equality & harmony – necessary for individual health  

DISTINCTIONS BETWEEN ‘HEALTHY’ & ‘DISEASE FREE’

·     Disease – means ‘disturbed ease’

·     Other words – Being uncomfortable

·     Disease – referred to have caused by a particular causative organism – this is not true

·     We can say – someone is suffering from diarrhoea – without knowing – what caused the loose motion

·     Simply not being diseased – not the same as being healthy

 

·     Example :

·     Good health for a dancer – able to stretch his body – in graceful position

·     Musician – being able to control his breathe – play the flute

·     We can be in poor health – without a cause for an identifiable disease

DISEASE AND ITS CAUSES

·     How do we know that there is something wrong with our body?

·     Many tissues in body – make up organ systems – carry out body functions

·     When there is a disease – functioning or the appearance of one or more system – change for the worse

·     These changes – gives symptoms & signs of diseases

·     Symptoms – things we feel as being ‘wrong’

·     Example: Headache, cough, loose motions, wound with a pus, etc.,

·     Symptoms – indicate – there may be a disease – but don’t indicate what disease

·     Doctors – look for the symptoms

·     Doctors – get laboratory tests done – pinpoint the disease

 

ACUTE & CHRONIC DISEASE

CHRONIC DISEASE & POOR HEALTH

·     Any disease – causes poor functioning of some part of the body – affects health

·     Acute disease – gets cured very soon – doesn’t cause major effects to our health

·     Example: Cough & cold – gets cured within a week – no bad effects on health

CHRONIC DISEASE & POOR HEALTH

·     Chronic disease – affects us for a longer period – Show major effects on health

·     Example: If a person is affected by Tuberculosis of the lungs – over the years – lose weight – feel tired all the time

·     Chronic diseases – have very drastic long term effects – on health – compared to acute disease

 

CAUSES OF DISEASES

·     There are many levels of causes – leads to disease

·     Example: A baby – suffering from loose motion

·     Immediate cause – Virus – microorganism – causes loose motion

·     Other reasons for loose motion

·     Lack of clean drinking water

·     Baby – not healthy – due to poor nourishment

·     Baby – may be from poor family

·     Poor public services in the area

·     These are contributory causes

·     All diseases – have immediate & contributory causes

INFECTIOUS & NON-INFECTIOUS CAUSES

·     Diseases – where microbes – immediate cause – called Infectious diseases

·     Because – microbes spread in the community – diseases spread with them

·     Diseases – not caused by infectious agents – called Non-Infectious diseases

·     Causes – not external – but mostly internal, non-infectious causes

·     Examples:

·     Cancers – caused due to genetic abnormality

·     High BP – caused due to excessive weight & lack of exercise

·     The way diseases spread & the way they can be treated / prevented – differs for each disease – depend on whether it is – infectious or non-infectious

 

INFECTIOUS DISEASES

INFECTIOUS AGENTS

·     Organisms – cause diseases – classified as – Viruses, bacteria, fungi, single-celled animals or protozoans, multicellular organisms – worms, etc.,

·     Example:

 

 

 

·     Categories of infectious agents – important factors – decides what kind of treatment to use

·     Members of each group of infectious agents – common characteristics

·     Example:

·     All viruses – live inside host cell; bacteria donot

·     Viruses, Bacteria & fungi – multiply very quickly; worms – multiply slowly

·     Many important life processes – similar in bacteria group; but not shared in Virus group

·     Let us consider – Anti biotics

·     block chemical pathways – in Bacteria

·     Bacteria – make a cell wall to protect themselves

·     Antibiotic Penicillin – blocks bacterial processes – that build cell wall

·     So, bacteria – unable to grow cell walls – die easily

·     Human cells – donot make cell walls – therefore – antibiotics donot affect them

·     Viruses – donot use such pathways – that’s why antibiotics do not work against virus

·     Example:

·     If a person have common cold – taking antibiotics – does not work

·     If a person get bacterial infection along with viral cold – antibiotics will work – only against bacterial infection 

MEANS OF SPREAD

·     Diseases – spread from affected person to healthy person – Communicable disease

·     Disease causing microbes – spread through – Air, water, sexual contact, insects, animals (vectors)

 

AIR BORNE DISEASE

·     Disease causing microbes – spread through air

·     When an infected person – sneezes or coughs – little droplets with microbes – thrown out

·     When someone close by – breathe in the droplet – get infected

·     Example: Common Cold, Pneumonia & Tuberculosis

 

WATER BORNE DISEASE

·     Disease causing microbes – spread through water

·     When excreta from infected person suffering from gut disease – get mixed with drinking water – microbe spreads to those people drinking unclean water

·     Example: Cholera

DISEASES - SPREAD THROUGH SEXUAL CONTACT

·     Microbial diseases – Syphilis or AIDS – transmitted by sexual contact – from one partner to another

·     Also spreads through – blood to blood contact – with infected person – or from an infected mother to her baby while pregnancy or through breast feeding

 

DISEASES – SPREAD THOUGH VECTORS 

·     Many diseases – transmitted by animals – carry microbes – from a sick person to another potential host

·     These animals – called Vectors

·     Example:

·     Female mosquitoes – feed on human blood – as they need nutritious food to lay mature eggs

·     Dogs – vectors for Rabies disease

ORGAN SPECIFIC & TISSUE SPECIFIC MANIFESTATION

·     Different species of microbes – enter body & goes to different parts of the body

·     The part where they manifest – depends on the point of entry

·     If they enter from air – through nose – affect the lungs; Ex: Bacteria – Tuberculosis

·     If they enter through mouth – go to the gut; Ex: Bacteria – Typhoid;

·     or go to the Liver; Ex: Viruses – Jaundice 

·     Exceptions: Example: HIV infection – comes through sexual organs – spreads to lymph nodes all over the body

·     Malaria causing microbes – mosquito bites – goes to liver – then to RBCs

·     Virus – causing Japanese encephalitis or Brain fever – mosquito bite – infects the brain

SIGNS & SYMPTOMS

·     Signs & symptoms – disease – depend on tissue or organ – which the microbe targets

 

 

 

 

 

 

·     Addition to tissue specific effects – there will be other common effects too

·     Common effects – caused by – immune system

·     An active immune system – recruits many cells – to the affected tissue – to kill off disease causing microbes – process called – Inflammation

·     As a result of inflammation – local effects – swelling & pain – general effects like fever

HIV MANIFESTATION

·     HIV infection – virus goes to immune system – damages its functions

·     Many effects of HIV-AIDS – body can no longer fight against minor infections

·     Example: Small cold – becomes pneumonia; small gut infection – lead to major diarrhoea with blood loss

·     Ultimately – other infections – lead to death of HIV infected person 

SEVERITY OF DISEASE MANIFESTATION

·     Severity – depends on number on microbes in the body

·     Number of microbes – small – disease manifestation – minor or unnoticed

·     Number of microbes – large – disease will be severe

·     Immune system – major factor – determines the number of microbes that survives in the body

PRINCIPLES OF TREATMENT

·     2 ways – to treat infectious disease

·     Reduce the effects of the disease

·     Kill the cause of the disease

·     Reduce the effects – take medicines – bring down fever, reduce pain or loose motion

·     Take bed rest – conserve energy

·     Eat bland food – easily digested – gives instant energy

·     This kind of symptom directed treatment – never kills disease causing microbe

·     To kill microbes – medicines are used

·     Microbes classified – different categories – Bacteria, viruses, fungi or protozoa

·     Each category – has specific biological pathway – synthesise new substances or respiration

·     These pathways – never used by another microbe category – nor by human beings

·     So, drug will be given – blocks this pathway – kills the microbe – cures infection  

·     Likewise – there are drugs – targets – Protozoa, fungi & viruses

·     Making anti-viral medicines – difficult – as viruses use biochemical pathways of their hosts

·     Despite these difficulties – effective anti-viral drugs – available

·     Example: Drugs that keeps HIV under control

 

PRINCIPLES OF PREVENTION

·     Three limitations – for curing disease from an infected person

·     A diseased person – body functions damage – may never recover completely

·     Treatment – takes time – meanwhile the infected person – bedridden

·     Infected person – serve as a source – from where infection spreads to other people

·     Because of these reasons – prevention is better than cure

 

 

·     Two ways – preventing diseases

o  GENERAL WAYS

·     Preventing exposure to infecting agents

·     Providing proper nourishment – builds proper immune system – fights against diseases

o  SPECIFIC WAYS

·     Through immunisation

GENERAL WAYS OF PREVENTING DISEASES

AIR BORNE DISEASE

·     Prevented – providing living conditions – not overcrowded

WATER BORNE DISEASE

·     Prevented – providing safe drinking water

VECTOR BORNE DISEASE

·     Prevented – providing clean environment

·     Clean environment – will not allow mosquito breeding

IMPROVING IMMUNE SYSTEM

·     Immune system – recognises infectious microbes – enters our body – kills it

·     Severe infections – when immune system fails

·     Immune system – may not work properly – if proper & sufficient food – not available

·     Proper nourishment is essential

SPECIFIC WAY OF PREVENTING DISEASES

·     Related to immune system – fights microbial infections

·     Earlier days – people – afraid of small pox – took many lives

·     But, a group of people – survived small pox – who had small pox earlier

·     Other words – if you had small pox once – there is no chance of catching the disease again

·     Having the disease once – means of preventing subsequent attacks

PRINCIPLE OF IMMUNISATION

·     Immune system – first sees an infectious microbe – responds against it – remembers it

·     Next time – if the same microbe / close relative – enters the body – immune system fights against it – more vigorously – kills it

·     Basis of Principle of Immunisation

IMMUNISATION

·     Edward Jenner – found milk maids – who was previously infected with cowpox – did not catch small pox

·     Cowpox – mild disease

·     Jenner – deliberately gave cowpox virus to people – found them to be resistant to small pox – because cow pox virus – closely related to small pox

·     ‘Cow’ – ‘Vacca’ in Latin; Cowpox – ‘Vaccinia’ – From this – ‘Vaccination’ originated

VACCINES

·     Our immune system – fooled to develop a memory – for a particular infection – by putting something that mimics the microbe – that we want to vaccinate against

·     This doesn’t cause the disease – prevents infecting microbe from turning into a disease

·     Many vaccines – available – prevents many infectious diseases – means of prevention

·     Example: Vaccines against Tetanus, Diphtheria, whooping cough, measles, polio, etc.,

 

·     Some Hepatitis virus – cause Jaundice – spread through water

·     Vaccine for one of them – Hepatitis A – available in the market

·     Majority of children in India – already immune to Hepatitis A – by the time they are 5 years

·     Because – they are exposed to the virus – via water

·     So, no need of vaccinating these children for Hepatitis A – as they are already resistant to it