Neurons: cells that transmit information

Neuron Structure

Dendrite: receives the information from other neurons and sensory receptors

Nucleus: provides energy for the neuron to carry out its functions

Cell Body: the cell’s life support center

Axon: carries the neuron’s messages to the other body parts

Myelin Sheath: fatty layer cover the Axon, increases speed of neuron messages

Terminal Buttons: form junctions with other cells

Neuron Signal Transduction

Nerve impulse is an electrochemical signal called Action Potential

Action Potential: brief electrical charge that travels down an axon. It is caused by the movement of positive ions in and out of the axon.

Threshold: once a neuron reaching this level of stimulation, it triggers action potential and the jump in mV.

The Stages of Action Potential:

Resting Potential: positive ions on the outside and negative ions on the inside. Neuron has a charge of around -70mV. Neuron is ready to be used.

Depolarization: Positive ions start to enter the neuron making the charge increase in positive charge. Incoming messages stimulates the section of the axon.

Repolarization: Positive charges start to leave the neuron as K+ ions exit the neuron. Causes the next section to enter depolarization.

Flow of Depolarization: Do-si-do between K+ and Na+ (causes neuron to go back to resting potential and ready for a new cycle). Causes action potential to continuously move down the axon.

The Insulated Neuron

Glial Cells: cells that provide structural, nutritional, and other support for the neuron.

Schwann Cells: Wraps around the Axon

(Myelin Sheath insulates Axon)

Nodes of Ranvier: spaces between Shwann cells. Action Potential jumps from node to node along the Axon.

Synapse Structure, Function & Communication

Synapse: structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell.

A synapse includes: tips of terminal branches of Axon, tiny space between neurons, ends of dendrites of receiving neuron.

Axon Terminal Button: Produces Neurotransmitters and stores it in synaptic vesicles.

Action Potential: once AP reaches the Axon Terminal, Neurotransmitters are released from the synaptic vesicles into the synaptic gap. Neurotransmitters diffuse through gap & bind to receptors on receiving neuron.

Messages received as excitatory or inhibitory

• Excitatory Neurotransmitters: stimulate Action Potential on receiving neuron.
• ex: Glutamate

• Inhibitory Neurotransmitters: repress Action Potential on receiving neuron.
• ex: GABA

Action Potential continues if there is more excitatory than inhibitory.

Neurotransmitters in synapse is slowly getting deactivated by enzyme and reabsorbed by axon terminal. This is the process of recycling and allows for our nervous systems to react at the proper moments.

Neurotransmitters fit into receptor like a key in a lock. Some chemicals can interfere with this.

• NT effect depends on action of receptor. Receptor may/could be: Acetylcholine, Serotonin, Dopamine