2.1.4 The Secret to Signals HBS PLTW WCHS Human Body Systems Mr. Alasti

Label the flow chart

1. Sensory pathways

2. Motor pathways

3. Somatic (voluntary) nervous system

4. Autonomic (involuntary) nervous system

5. Parasympathetic nervous system (rest & digest)

6. Sympathetic nervous system (fight or flight)

Neuropharmacology

The study of the action of drugs (including medicines and illegal drugs) on the nervous system

Action potential

A brief electrical impulse that travels along the axon of a neuron

What does the fluid around cells contain?

Ions (small, electrically charged atoms… we are focused primarily on sodium and potassium ions)

What do ions impact concerning a cell?

The overall charge of a cell (both inside and outside)

How is electricity (nerve impulse) created?

By the sudden reversal of the overall cell charge

Sodium-Potassium Pump

Moves sodium and potassium ions back to the side where they started using ATP (active transport)

How many sodium and potassium ions does a sodium-potassium pump, and in which direction?

3 sodium out, 2 potassium in

Resting Potential

When the outside of the neuron is more positive than the inside (-70 mV)

What happens to the sodium channels within a neuron when it receives a signal?

They open (the potassium doors stay closed), allowing sodium to rush in

Depolarization

The process of sodium rushing into the cell, making the inside of the cell more positive

What does depolarization cause?

A depolarization domino effect

Repolarization

The cell returns to its resting potential due to the switch of channel doors opening

Membrane Potential

The difference in voltage across the cell’s membrane

Synaptic Cleft

The small space between the sending cell and the receiving cell

Where are neurotransmitters found?

Within vesicles or sacs that are found within axon terminals

What do different classes of neurons contain different types of?

Neurotransmitters

What happens when a nerve impulse reaches axon terminals?

Calcium ions move into the cell via calcium channels, allowing the vesicles to fuse with the membrane and release neurotransmitters into the synaptic cleft

What moves across the synaptic cleft to bind to receptor cells? Where are the receptor cells located?

Neurotransmitters, on the receiving cell

What are receptors specific to?

The type of neurotransmitter that binds them

What happens after neurotransmitters bind to receptor cells?

They activate specific ion channels in the membrane of the receiving cell, causing depolarization

What does the cell become once the action potential travels down the neuron?

The receiving cell becomes a sending cell

Summarized steps of action potential graph

1. Stimulus is applied to the cell, causing the membrane potential to rise

2. The resting membrane potential of a neuron is typically -70 mV

3. After stimulation, the neuron reaches its threshold membrane (-55 mV)

4. Lots of sodium channels open, allowing positively charged sodium ions into the cell (depolarization— the membrane potential rises to 0 and then becomes positive

5. Action potential reaches its peak, sodium channels close, potassium channels open, and potassium flows out of the cell

6. Voltage inside the cell falls (repolarization), and the membrane potential drops back towards resting

7. The neuron overshoots resting potential and becomes hyperpolarized (membrane potential drops below resting)

8. Potassium channels close, and the sodium-potassium pump allows the membrane to return to resting potential, ready to be activated again