Neurons

Neural and Hormonal Systems will explain why we feel…

▪ Pain

▪ Strong

▪ Sick

▪ Nervous

It all starts with the neuron.

Neuron Structure

Neurons do NOT touch each other – the space between is called the synapse.

How a Neuron Fires

▪ It’s an electrochemical process–Electrical inside the neuron

–Chemical outside the neuron (this is neurotransmitters that are triggered at the synapse

–This firing is called action potential (this is a nerve impulse)

The All-or-None Response

▪ The idea that neuron fires or it does not–There is no part way firing

–Think like a gun firing

Steps of Action Potential

1. Dendrites receive neurotransmitters from another neuron across the synapse and move toward cell body.

2. Once it reaches a threshold, it then fires based on all-or-none response.

3. Opens up a portal in axon. This lets in positive ions (sodium) which mix with negative ions (potassium) that is already inside the axon. This means neurons at rest have a slightly negative charge.

4. The mixing of + and - ions causes an electrical charge that opens the next portal (letting in more potassium) while closing the original portal.

5. Process continues down axon to the axon terminal.

6. Terminal buttons turn electrical charge into chemical (neurotransmitter) and shoots message to next neuron across synapse.

Action Potential

Neurotransmitters

▪ These are neuron-produced chemicals that cross synapses to carry messages to other neurons or cells

▪ Cross the synaptic gap and bind to receptor sites on the receiving neuron– Act as excitatory or inhibitory signals

– Process begins anew

– Reuptake – sending neuron absorbs any excess neurotransmitters left in gap

▪ These neurotransmitters carry specific messages that affect our behavior and emotions

▪ There are 4 types we should know…

Acetylcholine (ACh)

▪ Function: –Motor movement, learning, and maybe memory

▪ Example of Imbalance:–Lack of ACh is associated with Alzheimer’s disease

(ACh producing neurons deteriorate)

Dopamine

▪ Function:– Influences movement, learning, alertness (attention),

emotion

▪ Example of Imbalances:– Too little – associated with Parkinson’s Disease

– Too much – associated with schizophrenia

Serotonin

▪ Function:– Deals with mood, hunger, sleep

▪ Examples of Imbalance:– Lack of serotonin linked to depression

Endorphins

▪ Function:–Pain control (lessen pain, boost mood)

–Our natural opiate

▪ Example of Imbalance:–Lack of may cause addiction

Agonists & Antagonists

▪ Agonists are drugs that activate certain receptors in the brain– Examples: heroin, oxycodone, hydrocodone, morphine

▪ Antagonists block opioids by attaching to opioid receptors without activating them– Naloxone is an example with can reverse a heroin

overdose