Study of the parts & functions of neurons

WHAT A NEURON LOOKS LIKE

Cells are specialized to… 1.) Receive information from the neurons that feed it. 2.) Process the information 3.) Pass on information to the next neuron. 3 MAIN TASKS OF NEURONS

 Carries sensory information toward the brain & spine.  What are your senses? 3 TYPES OF NEURONS: SENSORY NEURONS

 Transport messages away from the brain to the muscles, organs and glands. 3 TYPES OF NEURONS: MOTOR NEURONS

 aka the middle man  Sensory and motor neurons do not communicate directly with each other.  Found in the brain and spine 3 TYPES OF NEURONS INTERNEURONS

REFLEXES EVEN A HEADLESS WARM BODY COULD DO THAT!

parts & functions

 Receives messages from incoming terminal branches of other cells  Passes message to cell body PARTS & FUNCTION: DENDRITES

 Contains the cell’s nucleus (life-support)  Assesses all messages & passes on info at the appropriate time PARTS & FUNCTION: CELL BODY

 Cell body sends the message down the axon  Moves info from cell body to terminal branch  This is a one way street  Brain; the axons are very short  Leg; they can reach 3 feet long PARTS & FUNCTION: AXON

 Layer of fatty tissue that insulates the axon and speeds up the impulse and protects the message  Covering on your headphones PARTS OF THE AXON: MYELIN SHEATH If myelin sheath deteriorates: Communication to muscles slows leading to eventual loss of muscle control aka, Multiple Sclerosis (MS)

 Forms junction with next cell by releasing the message into the synapse PARTS & FUNCTION: TERMINAL BRANCH

How neurons communicate!!!!

 Information travels along the axon electrochemically (chemical change causes an electric signal)  What are the messages?  Neurotransmitters & hormones ELECTROCHEMICAL COMMUNICATION

 Dendrites send two types of messages to the cell body  If ‘excitatory’ messages outnumber ‘inhibitory’ messages, the cell reached absolute threshold  Now the cell body releases an impulse that sends the message down the axon  The impulse and the movement of the message is called ACTION POTENTIAL HOW THE CELL BODY KNOWS WHEN TO SEND AN ACTION POTENTIAL

 Once the cell body releases an Action Potential, the message gets carried down the axon and ends at the terminal branches HOW THE MESSAGE GETS ‘THERE’…WHERE?

 While the neuron is waiting to receive a message, its called ‘resting potential’  The cell body processes the message and if absolute threshold is reached, the impulse is fired.  Once the cell body fires an impulse, there is no going back!  ALL OR NOTHING PRINCIPLE  It fires in the same direction every time (dendrites to terminal branches)  Once the cell body fires, it needs time to reset; refractory period  Just because the signal is stronger doesn’t mean the message goes faster!  How do we tell the difference between a tap and a slap? PARTS OF ACTION POTENTIAL

 When an action potential reaches a terminal branch, it releases the message into the synapse  These neurotransmitters stimulate the dendrites on the next cell; the whole process starts over again WHAT HAPPENS AT THE TERMINAL BRANCH?

MR. N GOES TO THE BATHROOM