How the Nervous System Works

Learning goals…

1. Describe the electrochemical “action potential”. (5 steps on diagram)

2. Justify why nerve signals are electrical and chemical!!

3. Break down the reflex arc

4. Defend why Action Potentials are a type of active transport

5. Describe the 3 types of neurons

A. CNS PNSbrain nervesspinal cord

Somatic: regulates activites under concious control like-wiggle toes, lift up arm, walking

Autonomic: regulates activites, not under concious control..its automatic like-heart rate, sweat, digestion

B. Brain Signals Neurons are brain cells. Neurons send messages

electrochemically; this means that chemicals (ions) are charged – or +, and this can lead to an electrical impulse.

Neurons are electrically excitable cells, which means that they can transmit electrical nerve impulses.

Neurons are insulated by a fatty covering called myelin. Just like wires are coated with plastic!!!!

C. The Parts of the Neuron

1- DendritesAct like antennas receiving messages 2- The Cell Body or SomaContains the biochemical machinery to keep

the neuron alive 3- The AxonTransmits messages away from the cell body

to other neurons

D. 3 Types of Neurons

1. Sensory neurons : from sense organs (skin, eyes, tongue, ears) …“senses”

2. Interneurons: in brain and spinal cord

“decisions made”

3. Motor neurons: from brain to muscle or glands . “action”.

E. The Action Potential: the way a nerve impulse travels.

1. A neuron is at rest, it is negatively charged inside (-70mv) and positive outside.

2. Na-K pump uses ATP energy to move ions across membrane, Active Transport.

3. Neuron receives an impulse…causing protein gates to open and allow Na+ ions to rush in.

4. Inside of cell membrane is now more positive (-10mv) than outside membrane reaching its threshold and causing an action potential or nerve impulse!

5. At +30, Impulse passes, Na+ ions exit! Nerve cell back at rest (-70 mv).

6. Impulse on to next axon to dendrite and so forth!

F. Action Potential Diagram

G. The Reflec Arc

Reflex arc: a super fast nerve impulse that travels from the sensory neuron ( skin, ear, etc ) to the interneuron (spinal cord) to the motor neuron ( muscle cell).

The Pathway **skips the brain

Sensory interneuron motor/effector

Hot iron pain move hand

BBC - GCSE Bitesize - Reflex actions

How do medicines work?

http://www.paxilcr.com/favicon.ico

What I learned…answer learning goals!