NEW TOPICOn a full page write in big letters:

Coordination and Control

B1 2.1 Responding to ChangeText p.46

Homework• Using the GCSE workbook –

complete questions on pages 12,13,14,15

Starter

Sheepdash reaction test

Experiment – how sensitive are youone point or two?

1. Choose a place on the skin to test2. Set the sticks 4cm apart3. Press lightly on the skin and then lift off4. Your partner should feel 2 sticks5. Repeat number 3, each time moving the points closer

together until they can only feel one point6. Measure the distance between the points carefully7. Write this in your results table8. Oh and by the way, you must be sure they are not

cheating. So every few goes you could just touch them with one point to see if they are concentrating!

Results Table: Which area of the skin is most sensitive?

Skin surface tested

Minimum distance that two points can No longer be distinguished (mm)

Mean(mm)

Rep 1 Rep 2 Rep 3

Conclusions

• What is the independent variable?• What is the dependent variable?• Give a control variable.• What type of graph would you plot?• Which is the most sensitive area? When they

can only feel one point you know they must be sending one impulse along one sensory neurone to the brain

B1 2.1 Coordination and ControlResponding to Change

p.46

Syllabus B1.2.1 The Nervous Systema) The nervous system enables humans to

react to their surroundings and coordinate their behaviour.

b) Cells called receptors detect stimuli (changes in the environment).

Receptors and the stimuli they detect include: ■ receptors in the eyes that are sensitive to

light ■ receptors in the ears that are sensitive to

sound ■ receptors in the ears that are sensitive to

changes in position and enable us to keep our balance

■ receptors on the tongue and in the nose that are sensitive to chemicals and enable us to taste and to smell

■ receptors in the skin that are sensitive to touch, pressure, pain and to temperature changes.

c) Light receptor cells, like most animal cells, have a nucleus, cytoplasm and cell membrane.

d) Information from receptors passes along cells (neurones) in nerves to the brain. The brain coordinates the response. Reflex actions are automatic and rapid. They often involve sensory, relay and motor neurones.

The Nervous System

• All organisms respond to changes in their environment

• Your nervous system makes this possible.• Your nervous system carries electrical

signals (impulses) that can travel between 1 and 120 metres per second.

Sensory Receptors

Ears – receptors sensitive to sound

Eyes – receptors sensitive to light

Nose and Tongue – receptors sensitive to chemicals for taste and smell

Ears – receptors sensitive to changes in position for balance

Skin – receptors sensitive to touch, pressure, pain and temperature changes

What are neurones? Neurones are specialized cells that conduct electrical impulses through the body.

nerve fibre

A nerve is a bundle of many nerve fibres enclosed within a protective sheath. Nerve fibres are the long axons of neurones together with any associated tissues.

nerve

What do neurones look like?

The axons of most neurones are wrapped in an insulating lipid layer called the myelin sheath. Why is this important?

Thin projections called dendrites extend from the cell body and connect with other neurones, allowing electrical impulses to pass from one to the other.

Neurones are elongated cells consisting of a cell body and long, thin axon.

myelin sheath

axon

cell body

dendrites

What are sensory neurones?Sensory neurones transmit messages from sense receptors, such as the eye or nose, to the brain or spinal cord.

cell body

nerve impulse from sense organ

nerve impulse to CNS

COPY INTO BOOKS – 3 MINUTES

What are motor neurones?Motor neurones transmit messages from the brain and spinal cord to the muscles and glands.

cell body

muscle

COPY INTO BOOKS – 3 MINUTES

The rapid responses of our nervous system allows us to respond to our surroundings

quickly – and in the right way!

Video - Wired• Science in Focus – Wired (copied to DVD too)• Answer questions from A5 sheet during video• PJO 20.0

Sequence of events p.47

Add to notes:• Process of responding to a stimulus, from

receptor to effector (in bold on p.47)• Now complete first half of the ‘controlling

conditions’ worksheet and stick in books

Homework• Using the GCSE workbook –

complete questions on pages 12-13