Sensitivity

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

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)

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

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.

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!

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?

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

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)

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).

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

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

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

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)

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

Relay neuron

Reflex Arc