Neurons & the Nervous System

Nervous System Network of connected cells, tissue, and organs Controls thoughts, movement, life processes Quick responses Ex: Sunny day  pupils shrinking Eye in bright light Eye in dim light

What must happen in order to pick up the apple? Light reflects off the apple and into your eyes… Photoreceptors (rods and cones) send a signal to your brain… Your brain receives the signals and sends another signal down your spine… Down your arm… To your hand… Hand muscles react to those signals and grab the apple

Neurons AKA: Nerve Cells Function: Transfer electrical impulses to/from the brain 3 Main Parts Cell body: contains nucleus and organelles Dendrites: branches that receive impulses from neighboring cells Axon: extension that carries impulse away from the cell body Cell Body Dendrites Axon

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

Three Types of Neurons: 1) Sensory Detect stimuli and transmit signals to/from the brain Detect sense (sight, smell, sound, taste, touch) 2) Interneuron Located in the brain Receive signals from the sensory neurons

Three Types of Neurons: Muscle cell Motor Neuron 1) Sensory Detect stimuli and transmit signals to/from the brain Detect sense (sight, smell, sound, taste, touch) 2) Interneuron Located in the brain Receive signals from the sensory neurons 3) Motor Pass signal to other tissue Ex: Nerve attached to muscle Muscle reacts by contracting/stretching

- - - - - - - - - - - Resting Potential Defined: Neuron at rest An electrode can be inserted to measure the internal charge Exterior Lets zoom into the cell membrane of this neuron… - - K+ Interior - - - -70mV - Defined: Neuron at rest Neuron Interior = negative charge due to cytoplasm proteins (although K+ inside) - K+ K+ - - - - K+

Resting Potential Defined: Neuron at rest Exterior Na+ Na+ Na+ Na+ Na+ Na+ Na+ Interior Defined: Neuron at rest Neuron Interior = negative charge due to cytoplasm proteins (although K+ inside) Neuron Exterior = positive charge due to abundance of Na+ ions

- - - - - - - - - - - - - - - - - - - - - - - - - - Resting Potential 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+ Exterior Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ - - - - K+ Interior - K+ K+ - K+ - - - - - - K+ - - - K+ - K+ - - - K+ - - - - - K+ - K+ K+ - K+

Action Potential Defined: Electrical impulse is triggered & moves quickly down axon Analogy: An action potential is like people doing “the wave” at a sporting event.

Action Potential Defined: electrical impulse 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 Na+ Na+ Na+ Na+ Na+ -90mv K+ -40mv K+ +50mv K+ K+ K+

Here is an action potential (impulse) moving down a neuron… 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+ Lets zoom in… 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+

-40mV: Na channels open & positive Na+ ions diffuse inside +50mV: Na channels close & K channels open. K+ ions diffuse outside. Na+ -90mV: K channels close & Na channels open. Na+ ions diffuse inside. Na+ +50mV: Na channels close & K channels open. K+ ions diffuse outside. Na+ Na+ -90mV: K channels close & Na channels open. Na+ ions diffuse inside. 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+ +50mV +50mV K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ +50mV 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+ -90mV -90mV -90mV 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+

The impulse moves down the length of the axon. Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ - - - - - - - - - - - + K+ + K+ + K+ + K+ + K+ + K+ + K+ + K+ + - - - - - - - - - - - - - - - - - - - - - The impulse moves down the length of the axon.

Too much potassium (K+) on the outside of the cell Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Problem: Too much potassium (K+) on the outside of the cell 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+ Problem: Too much sodium (Na+) on the inside of the cell 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+

Cleaning Up the Mess Who? Na/K pump How? Active transport (use of ATP) What? 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 K+ K+ K+ K+ K+ heat A P P Na+ Na+ Na+ Na+ Na+

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+

Normally negative charge 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+ 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+ Normally negative charge 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+

Lets continue moving the impulse… Na Na Na Lets continue moving the impulse… Na Na vesicle receptor Lets zoom in again…

Synapse Defined: Gap between neurons vesicle receptor K K Defined: Gap between neurons Problem: Impulse cannot cross the gap Solution: Neurotransmitter proteins sent from one cell to another Steps: 1) Impulse reaches axon terminal (end) 2) Neurotransmitters (from vesicles) attach to neighboring receptors 3) Na channels open on neighboring cell…new impulse created

Synapse Defined: Gap between neurons vesicle K K Defined: Gap between neurons Problem: Impulse cannot cross the gap Solution: Neurotransmitter proteins sent from one cell to another Steps: 1) Impulse reaches axon terminal (end) 2) Neurotransmitters (from vesicles) attach to neighboring receptors 3) Na channels open on neighboring cell…new impulse created

-40mV: Na channels open & positive Na+ ions diffuse inside +50mV: Na channels close & K channels open. K+ ions diffuse outside. Na+ -90mV: K channels close & Na channels open. Na+ ions diffuse inside. Na+ +50mV: Na channels close & K channels open. K+ ions diffuse outside. Na+ Na+ -90mV: K channels close & Na channels open. Na+ ions diffuse inside. 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+ +50mV +50mV K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ +50mV 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+ -90mV -90mV -90mV 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+

Synapse Neurotransmitters are released across the synapse Na Na Na Na vesicle receptor K K The impulse reaches the terminal end…

A new impulse is triggered Synapse Na Na vesicle K K A new impulse is triggered

Brain . . . . . . . . . . . . Feet

Impulses eventually reach the muscles… Muscle cell and causes MOVEMENT!

Practice Quiz What is the function of the nervous system? Name the 3 types of neurons. List the 3 main parts and describe their purpose. Describe the internal and external environment of a neuron in resting potential. What is a synapse and why is it a problem for neurons? What are the roles of the following during an action potential? Na+ ions, K+ ions, Neurotransmitters, Receptors, Na/K pump Explain (paragraph form) how an action potential is passed from one neuron to another.