1. Sensitivity

2. Vocab at a glance Stimuli: changes in the environment
Receptors: sensory cells (eyes)
Effectors: thing that responds to stimuli (mouth watering)
Neuron: nerve cell
Impulse: electrical signal

3. Coordination
How receptors pick up stimuli and pass the information to effectors.
This can be done by 2 systems:
-the nervous system (nerves)
-the endocrine system (hormones)

5. Nervous System Is actually split into 2 systems:
Central Nervous System (CNS): spinal cord and brain; functions to coordinate all actions of the body
Peripheral Nervous System (PNS): body’s nerves; functions to connect the CNS to the rest of the body through neurons

6. Parts of the nervous system
The nervous system is made up of three main parts;
The brain
The spinal cord
Nerve fibres
It detects stimuli such as light, sounds, temperature, pressure, pain and co-ordinates the bodies response.

7. Parts of the nervous system
For example;
If you smell something burning…
Your nose (receptor) detects the stimulus (smell)
Nerve fibres send the message to the brain
Your brain then sends a message to move your body away or to put out the fire!
SIMPLE RIGHT!

8. Lets look at some bits more closely RECEPTORS
Receptors are sensors on the body that detect stimuli
They convert stimuli into electrical signals (messages) called impulses.
Eyes pick up
light waves
through the
retina
Nose picks up
chemical signals
through the
nostrils
Ear picks up
sound waves
through the
eardrum
Can you think
of any receptors?

9. EFFECTORS
An effector is any part of the body that produces the response.
Here are some examples of effectors:
a muscle contracting to move the arm
a muscle squeezing saliva from the salivary gland
a gland releasing a hormone into the blood

10. Assignment
With someone sitting close to you, come up with 2 coordinated responses.
Remember to include
Stimulus (good smelling food)
Receptor (nose)
Effector (salivary glands)

11. NERVE FIBRES
Nerve fibres are bundles of nerve cells (neurons) that pass on electrical signals (impulses) to the brain.
From the brain, nerve fibres send impulses to effectors (muscles).

12. Neurons
Draw the diagram in your notes, don’t forget about the labels!

13. Neurons
The cell body of a neuron is like any other animal cell, it has a nucleus, cytoplasm, and a cell membrane

14. Neurons Dendrites pick up signals from the receptor or other neurons.
Those impulses are passed along the axon, where they exit the neuron

15. Neurons
The axon is sometimes surrounded by a layer of protein and fat called myelin.
This insulates the axon, and allows the electrical impulse to travel MUCH faster (100 m/s vs. 5 m/s)

16. NEURONS 3 types of neurons
Sensory neuron – carries impulses from the receptors to the spinal cord.
Relay Neuron – carries impulses to and from the spinal cord and the brain
Motor Neuron – carries impulses from the brain to the effector

17. Relay neuron

18. Reflex Arc