Central Nervous System

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Central Nervous System

National 4 & 5:Multicellular Organisms

Multicellular organisms are made up of many different tissues and organs

Cells do not work independently, so they communicate with each other

Also, different tissues and organs need to communicate with each other

Communication is usually carried out in 2 ways:

- hormones - nerve signals

Internal Communication

Identify the discrete areas of the brain and understand their functions

Identify the different typed of nerves/neurones in the human body

Examine the role of each type of nerve/neurone

Explain how a reflex action works, and identify examples of this

Examine how information is passed from one neurone to another

Learning Outcomes

What is the nervous system composed of? The nervous system is composed of: - the brain - the spinal cord - nerves

Cerebrum - conscious

thought, reasoning, imagination

Cerebellum- balance and co-ordination

Medulla (brain stem)- heart rate and breathing rate

The Brain

The brain is approximately 75% water It weighs about 3 pounds, BUT uses between 20%-25% of

your energy supplies each day Your brain can survive without oxygen for 4-6 minutes

before it starts to die There are over 100, 000 miles of blood vessels in your brain There are over 100 billion neurons in your brain

It’s not true that humans only use 10% of their brains; each part of the brain has a purpose

The slowest speed information passes around your brain is approximately 260 mph

The number of internal thought pathways that your brain is capable of producing is one followed by 10.5 million kilometers of standard typewritten zero’s!

Brain facts

Stimulus (change) picked up by receptor

Impulse carried along nerve cell (Sensory neurone) to spinal cord

CNS processes info & sends a response

Impulse carried along nerve cell (motor neurone) to effector organ

Effector organ brings about a response

Central Nervous System (CNS)Consists of the brain and spinal cord

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2)

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Receptors are found all over the body, often as part of sense organs

E.g. eyes, ears, skin They work in response to a stimulus The more receptors, the more sensitive an

area usually is to a stimulus

Effectors are also found all over the body They act in response to the CNS The more effector cells are in a body part,

the more it can move or the faster it can act

Effectors are often either muscles or glands - muscles respond rapidly - glands respond more gradually

Receptors and effectors

Sense Stimulus Sense organSight light eyes

Sight

Sense Stimulus Sense organSmell chemicals nose

Smell

Sense Stimulus Sense organTemperature heat / cold skinPain damage skinPressure force skinTouch contact skin

Skin

Hearing/balance

Sense Stimulus Sense organHearing sound earsBalance movement

/ positionpart of inner

ear

Sense Stimulus Sense organTaste chemicals tongue and

throat

Taste

The Reflex Arc A reflex is a rapid, unconscious response to a stimulus e.g. blinking, pulling a hand off a hot surface

Relay neurone

motor neurone

sensory neurone

• Receptor cells send an impulse along the sensory neurone to the CNS

• The relay neurone transfers the impulse to the motor nerve

• The motor neurone transfers the impulse to the effector cells, to carry out the response

What happens in a goalie’s body as he tries to save a goal?

The greatest goals of all time

What happens in a goalie’s body as he tries to save a goal?

Mark each other’s work:

1 point if they have used any of these words:Eye(s) Brain

2 Points:Nerve(s) Muscle(s)

3 Points:Neurone(s) Receptor(s) Spinal cord

4 Points:Motor (neurone) Sensory (neurone)

Use your judgement – any other scientific words that they have used correctly that should get points?

You have been given a series of cards for a series of reflex actions

You must arrange them under the following headings

Reflex responses

Stimulus

Receptor

Response Co-ordinator

Effector Response

How fast are your reflexes??

1.Using a ruler you have to see how quickly you can catch it.

2. Each person will try three times and record their results in a table

3. We will then collect the class data

Name Result 1 Result 2 Result 3 Average

Name Average reflex (cm) Graph

0

Remember Title,

label axis,

Pupil Name

Aver

age

refle

x (c

m)

Information is carried through the CNS by a series of neurones

Information is picked up by a neurone through a dendrite Then it is passed to the cell body It then gets passed towards the next neurone by an axon

fibre

Transfer of information along neurones

Structure of a synapse• Between each

neurone is a small gap called a synapse

• To pass information between neurones, a chemical passes across this synapse

• These chemicals are called neurotransmitters

Re-Cap

1. What is meant by the term reflex action?2. Give an example of a reflex action.3. What is the function of the sensory nerve?4. What part of the brain controls our breathing rate?5. What part of the brain controls our balance?6. What part of the brain is responsible for our memory?