Neurons

Neurons AKA: Highly specialized nerve cells 4 Main Parts Transfer electrical impulses to/from the brain 4 Main Parts Cell body: contains nucleus and organelles Dendrites: branches that receive messages from neighboring cells Axon: extension that carries messages away from the cell body Axon Terminal: End of neuron

Three Types of Neurons: 1) Sensory Detect stimuli and transmit signals to/from the brain Detect sense (sight, smell, sound, taste, touch)

Three Types of Neurons: 2) Interneuron Located in the brain Receive signals from the sensory neurons

Three Types of Neurons: 3) Motor Pass messages to other tissue Ex: Nerve attached to muscle Muscle reacts by contracting and stretching

Resting Potential Defined: Neuron at rest Neuron Interior is negative K+ Interior K+ K+ K+ K+ K+ K+ K+ K+ Defined: Neuron at rest Neuron Exterior is positive in charge Due to abundance of Na+ outside Neuron Interior is negative Due to abundance of proteins and… Some K+ inside the cell

Action Potential Defined: The electrical impulse that is triggered & moves quickly down an axon Generating the Impulse Na channels in the membrane open and allow Na+ to diffuse into the cell Area becomes positively charged (impulse) After the Impulse K channels open to allow K+ to exit the cell Area returns to negative charge Process continues down the axon

impulse

Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ impulse K+ K+ K+ K+ impulse K+ K+ K+ impulse K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+

Cleaning Up the Mess Who? What? When? Where? Why? How? Na/K pump Na is pumped back out of the cell… K is pumped back into the cell When? After the impulse has passed Where? Located in cell membrane Why? To restore the initial charge inside & outside the cell How? Active transport (REQUIRES ATP)

Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ Na+ K+ K+ Na+ Na+ Na+ Na+ Na+ K+ Na+ K+ Na+ Na+ K+ K+ K+ K+ K+ Na+ K+ Na+ Na+ K+ K+ Na+ Na+ Na+ K+ K+ K+ K+ Na+ Na+ K+ Na+ K+ K+ K+ Na+ Na+ Na+ Na+ Na+ K+ K+ K+ Na+ Na+ Na+ Na+ Na+ K+ K+ K+ Na+ Na+ Na+ K+ Na+ Na+ K+ Na+ K+ K+ Na+ Na+ Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ K+ Na+ Na+ K+ Na+ Na+ Na+ K+ Na+ Na+ Na+ K+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ Na+ Na+ K+ Na+ Na+ Na+ Na+ Na+ K+ K+ K+ K+ K+ K+ Na+ K+ Na+ Na+ Na+ Na+ Na+ K+ K+ Na+ K+ Na+ K+ K+ Na+ Na+ Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+

Synapse Defined: Gap between neurons Problem: Impulse cannot cross the gap Solution: Neurotransmitter proteins are sent from one neuron to another Steps: 1) Impulse reaches axon terminal (end) 2) Vesicle releases neurotransmitters, which attach to receptors on neighbor 3) Channels open on dendrite of neighboring cell…new impulse created Neurotransmitter proteins

Vesicle exits the cell and dissolves Na Na Na Vesicle exits the cell and dissolves impulse impulse impulse K K K Impulse reaches the axon terminal Dendrite of another cell Terminal end of one cell

Neurotransmitters cause Na channels to open… creating new impulse Neurotransmitters diffuse across the synapse and attach to receptors of a neighboring neuron Na Na Na impulse impulse impulse impulse K K K Dendrite of another cell Terminal end of one cell

Brain Feet …. …. …. …. impulse impulse impulse impulse impulse neurotransmitters impulse …. neurotransmitters impulse …. neurotransmitters impulse …. neurotransmitters impulse Feet

Impulses eventually reach the muscles… and causes MOVEMENT!

ReView 1. What is the function of the nervous system? 2. List the 4 main parts and describe the purpose of the 4 main parts of a neuron. 3. The nervous system is divided into 2 parts. What are they and what do they include? 4. Describe the internal and external environment of a neuron in resting potential. How is resting potential reached? 5. What is a synapse and why is it a problem for neurons? 6. To what part of the nervous system do motor neurons, interneurons, and sensory neurons belong? 7. When an impulse is within a neuron it is electrical. When the signal moves to the next neuron it is _________________. What is the specific name for this? 8. Describe how an action potential moves down a neuron.