1. Central Nervous System
National 4 & 5: Multicellular Organisms

2. Internal Communication
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

3. Learning Outcomes
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

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

5. The Brain Cerebrum - conscious thought, reasoning, imagination
Cerebellum
- balance and co-ordination
Medulla (brain stem)
- heart rate and breathing rate

6. Brain facts 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

7. Central Nervous System (CNS)
Consists of the brain and spinal cord 1)
Stimulus (change) picked up by receptor 2)
Impulse carried along nerve cell (Sensory neurone) to spinal cord 3)
CNS processes info & sends a response
Impulse carried along nerve cell (motor neurone) to effector organ 4) 5)
Effector organ brings about a response

8. Receptors and effectors
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

9. Sight
Sense
Stimulus
Sense organ
Sight
light
eyes

10. Smell
Sense
Stimulus
Sense organ
Smell
chemicals
nose

11. Skin Sense Stimulus Sense organ Temperature heat / cold skin Pain
damage
Pressure
force
Touch
contact

12. Hearing/balance Sense Stimulus Sense organ Hearing sound ears Balance
movement / position
part of inner ear

13. Taste
Sense
Stimulus
Sense organ
Taste
chemicals
tongue and throat

14. The Reflex Arc A reflex is a rapid, unconscious response to a stimulus
e.g. blinking, pulling a hand off a hot surface
Receptor cells send an impulse along the sensory neurone to the CNS
Relay neurone
The relay neurone transfers the impulse to the motor nerve
sensory
neurone
The motor neurone transfers the impulse to the effector cells, to carry out the response
motor neurone

15. What happens in a goalie’s body as he tries to save a goal?
The greatest goals of all time

16. 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?

17. Reflex responses
You have been given a series of cards for a series of reflex actions
You must arrange them under the following headings
Stimulus
Receptor
Response Co-ordinator
Effector
Response

18. 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

19. Results
Name
Result 1 (mm)
Result 2 (mm)
Result 3 (mm)
Average (mm)

20. Who is the fastest - Class results
Name
Average reflex (mm)
Remember Title,
label axis,
Graph
Average reflex (mm)
Pupil Name

21. Transfer of information along neurones
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

22. 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

23. Re-Cap What is meant by the term reflex action?
Give an example of a reflex action.
What is the function of the sensory nerve?
What part of the brain controls our breathing rate?
What part of the brain controls our balance?
What part of the brain is responsible for our memory?