CBSE CLASS 10 CHAPTER 7 NOTES

CHAPTER 7

CBSE SCIENCE
CLASS 10

CONTROL &

CO – ORDINATION

CONTROL & CO – ORDINATION

·     Most organisms – move in response to the environment or stimuli

·     Specialised tissues are used to provide these control & co – ordination activities

 

ANIMALS – NERVOUS SYSTEM

·     When a hot object is touched – detected by tips of nerve cells (receptors) – in sense organs

·     Gustatory receptors – detect taste

·     Olfactory receptors – detect smell

·     This information acquired at the end of the dendritic tip – sets off a chemical reaction – creates an electric impulse

·     Impulse – travels from dendrite à cell body  axon

·     End of the axon – electrical impulse release off chemicals

·     Chemicals – cross the gap or synapse – reach dendrites of next neuron

·     Likewise, impulse travels from neuron à neuron & neuron à other cells

 

REFLEX ACTION

·     When a hot object is touched – stimuli taken by neurons in the sense organs – connected to the nerves that move muscles – response is immediate – Reflex arc

·     Connection between input  nerve & output nerve – happens at a particular point

·     Nerves from all over the body – meet in a bundle in the spinal cord – on their way to brain

·     Reflex arcs – formed in spinal cord

·     Although the input information – goes on to reach the brain

·     Reflex arcs – evolved from animals – as they don’t have thinking process that is complex 

HUMAN BRAIN

·     Apart from reflex action – spinal cord also has nerves – supply information for thinking

·     Thinking – complex process – involves many neural connections – concentrated in the brain

·     Brain + Spinal cord à CNS (Central Nervous System) – receives information from all parts of the body & integrate

·     Brain also sends information to the muscles – to do voluntary actions – writing, talking, riding, etc.,

·     Communication between the CNS and the other parts of the body – facilitated by Peripheral nervous system

·     Peripheral Nervous system consists of

·     Cranial nerves of Brain

·     Spinal nerves of Spinal Cord

·     Brain has 3 major parts

·     Fore brain      

·     Mid brain

·     Hind brain

·     Fore brain – Main thinking part

·     Receives impulses from various receptors

·     Fore brain – specialised separate areas for hearing, smell, sight, hunger & so on

·     Separate regions of association – where these information from receptors are interpreted with already stored information in the brain

·     Based on this – decision is made on how to respond – information is passed to motor areas – controls voluntary muscles

·     Mid brain & Hind brain – controls involuntary actions like mouth watering, heart beat, digestion of food, breathing, etc.,

·     Medulla in the hind brain – controls involuntary actions like blood pressure, salivation & vomiting

·     Cerebellum in the hind brain – responsible for activities like walking in a straight line, riding a bicycle, picking up a pencil

·     Cerebellum – responsible for body posture & balance of the body

PROTECTION OF THESE TISSUES

·     Brain – delicate organ – protected by the bony skull

·     Inside skull – brain is contained in a fluid filled balloon – provides shock absorption

·     Fluid – Cerebro spinal fluid

·     Spinal cord – protected by the vertebral column or the back bone

ACTION CAUSED BY NERVOUS TISSUE

·     When a nerve impulse reaches the muscle – it moves

·     Movement of the muscle is by changing the shape & arrangement of the muscle cells

·     Muscle cells – special protein – contractile protein – change the shape & arrangement of the muscle cells – in response to nervous impulse

 

CO – ORINATION IN PLANTS

·     Unlike animals – plants do not have nervous system or muscles to move

·     Plants show – 2 types of movement

·     Dependent on growth

·     Independent of growth

·     When seeds germinate – roots goes down – stem moves up into the air – movement dependent on growth

·     When we touch the plant – ‘Touch me not’ – begin to fold up & droop – movement independent of growth

IMMEDIATE RESPONSE TO STIMULI

·     Touch me not plant – moves when touched – this shows that the information is communicated

·     But plants do not have special tissues for conduction of information

·     So, Some cells – must change shape in order for the movement to happen

·     But instead of specialized protein present in animal muscle cells, plant cells change the shape by changing the amount of water in them – resulting in swelling or shrinking

MOVEMENT DUE TO GROWTH

·     Plants like pea plants – have tendrils – sensitive to touch

·     When they come in contact with an object – cling to the object – as they need support

·     As these plants grow in particular direction – seem to be moving

·     Environmental factors (light / gravity) change the direction of the growth of plant parts

·     These tropic directional movements – can be either towards or away from the stimulus

MOVEMENT DUE TO GROWTH

Phototropic Movement

·     Shoots – grow / bend towards light

·     Roots – bend away from light

Geotropic Movement

·     Shoots – grow away from gravity 

    (upwards)

· Roots – grow towards gravity (downwards)

MOVEMENT DUE TO GROWTH

·     If plants respond to chemicals – Chemotropism Eg: Growth of pollen tube towards the ovules

·     Movement due to growth is very slow

·     Even in animal bodies – there are carefully controlled directions to growth

·     Our arms & fingers – grow in certain directions

·     Controlled growth can be either slow or fast

·     Response to stimuli – fast – then information transfer must happen quickly

·     Electrical impulses – are the best means for this

LIMITATIONS OF ELECTRICAL IMPULSES

·     Electrical Impulses – will reach only those cells – that are connected by nervous tissue

·     Will not reach each an every cell in the animal body

·     Once a cell generates an electrical impulse & transmits it – will take some time to reset its mechanisms to transmit a new impulse

·     Therefore most multicellular organisms use another means of communication between cells namely – Chemical Communication  

CHEMICAL COMMUNICATION

·     Instead of electrical impulse, stimulated cells release a chemical compound

·     These chemical compound will diffuse & reach the other cells

·     Other cells which have special molecules on their surface detect this chemical compound & transmit it

·     This is slow but it can reach each & every cell regardless of nervous connections

·     These chemical compounds – called hormones

HORMONES

·     Hormones used by multicellular organisms for control & co-ordination – show great diversity

·     Different plant hormones help to co-ordinate growth, development & response to environment

·     Hormones are synthesized at places away from its point of action

HORMONES IN PLANTS

·     When plants detect light – Auxin hormones are synthesize at shoot tip – helps the cells to grow longer

·     When light is coming from one side of the plant – auxin diffuses towards the shady side of the shoot

·     This makes the cells to grow longer on the shady side

·     Thus plant appear to bend towards light

·     Gibberellins – another hormone like auxin helps in – growth of the stem

·     Cytokinins – promote cell division & is present in great concentration in fruits & seeds

·     Abscisic acid – inhibits growth in plants which include wilting of leaves

HORMONES IN ANIMALS

·      When an animal comes across a scary situation – its body gets prepared to either fight or run away

·      When this is done by our nervous tissue – electrical impulse will reach only few cells

·      When a hormone is secreted – diffuses to every cell – animal will be ready to face the situation

·      This happen even in humans – Hormone adrenaline – secreted by Adrenal glands – present above the kidneys

ADRENALINE   HORMONE

·      Adrenaline – secreted directly into blood – carried to different parts of the body – including heart

·      Result – heart beats faster & more O₂ is supplied to muscles

·      Blood to digestive system & skin is reduced – due to contraction of arteries around these organs

·      Blood is diverted to skeletal muscles

·      Breathing rate – increases – because of contraction of diaphragm & rib muscles

·      All these makes the animal body to be ready to face the situation

·      Such hormone – part of Endocrine System

·     Endocrine system – second way  of control & co-ordination in our body

HOW HORMONES WORK IN AN ANIMAL BODY?

(I) THYROXINE

·      Thyroxine – secreted by Thyroid gland

·      Thyroxine – regulates carbohydrates, protein and fat metabolism & provide best balance for growth

·      It is advised to take iodised salt – enriched with iodine

·     Iodine – necessary for thyroid gland to make thyroxine hormone

·      In case of iodine deficiency – result in Goitre disease (Symptoms – Swollen neck)

(II) GROWTH  HORMONE

·      We may have come across people who are very short (Dwarfs) or extremely tall (Giants)

·      This is because of growth hormones secreted by the Pituitary gland

·      Growth hormone – regulates growth & development of the body

·      Deficiency of growth hormone – result in Dwarfism

·      Excess of growth hormone – result in Gigantism

(III) OESTROGEN & TESTOSTERONE

·      Boys & girls – shows many changes in their appearance – age of 10 to 12 years

·      These changes are associated with puberty

·      These changes occurs because of – hormones – Testosterone in males – Oestrogen in females

(IV) INSULIN

·      Diabetes patients – take insulin injections

·      Insulin – hormone produced by Pancreas & it helps to regulate blood sugar levels

·      Insulin – not secreted in proper amounts – result in harmful effects

FEED BACK MECHANISMS

·      It is very important – hormones are secreted in precise quantities

·      To check that we have feed back mechanism

·      Example: Sugar level increases – detected by pancreas cells – respond by producing more insulin

·      If blood sugar level falls – insulin secreted is reduced