Chapter 3a: Neurons, Neurotransmitters, and Drugs

Sensory neurons

Transmit sensory information to the brain and spinal cord

Schwann cells and Glial cells

Support and protect neurons, aiding in the maintenance of neurons, hold neurons in place

Synapse

The space between two neurons where neurotransmitters are released to transmit signals, (axon terminals to dendrites).

Resting Potential

The electrical charge difference across the neuronal membrane when the neuron is not actively transmitting a signal, typically around -70mV.

Action Potential

An electrical signal that occurs when a neuron's stimulation exceeds the threshold, traveling down the axon to trigger neurotransmitter release at the axon terminal

All or none

Action potentials occur at a uniform and maximal intensity, or they do not occur at all

Depolarization

The inside of the neuron becomes less negative, sodium in → makes inside more positive, and it kickstarts an action potential

Absolute Refractory period

During this period, cell cannot fire again, it limits how often nerve impulses can occur, and ensures that impulses only travel in a single direction

Terminal buttons

The small knobs at the end of axons that release neurotransmitters into the synapse, facilitating communication between neurons.

Five stages of chemical communication

1. Synthesis → make the neurotransmitters in the neuron

2. Storage → held in synaptic vessels

3. Release → into synaptic space

4. Binding → attach to receptor sites

5. Deactivation → Stop the neurotransmitters

Acetylcholine (ACh)

• Excitatory

• Functions at synapses

• Involved in muscle movement and memory

• Connected to Alzheimer’s

Dopamine

• Excitatory and inhibitory

• Functions at various sites

• Involved in voluntary movement, learning, motivation, pleasure

• Low → Depression, Parkinson’s disease

• High → Schizophrenia

Glutamate

• Excitatory

• Expressed in whole brain

• Involved in control of behaviours, especially learning and memory

GABA (gamma-aminobutyric acid)

• Inhibitory

• Expressed in whole brain

• Involved in control of behaviours, especially anxiety and motor control

• Related to Huntington’s disease (less = less inhibition = too much/uncontrolled movements)

Norepinephrine

• Excitatory and inhibitory

• Functions at various sites

• Involved in learning, memory, alertness, and eating

• Fight or flight, High → Panic disorders

• Low → Depression

Serotonin

• Mostly inhibitory

• Functions at various sites

• Mood, eating, sleep, arousal

• Low → depression, no melatonin, eating disorders

• High → Less sleeping, agitation, seizures, unconsciousness

Endorphin

• Inhibitory

• High → Insensitivity to pain

• Low → Hypersensitivity to pain and immune problems

Agonists

Mimic or enhance the effect of a neurotransmitter

Antagonists

Block or reduce the effects of a neurotransmitter

Interneurons

transmit signals within the central nervous system

Motor neurons

transmit commands from the brain and spinal cord to muscles

Repolarization

Restoring negative charge inside the neuron and bringing it back towards its resting state, potassium out → makes inside negative again

Inhibitory vs. Excitatory Neurotransmitters

Hyperpolarizes neuron’s membrane and decreases likelihood of action potential vs. Depolarizes neuron’s membrane and increases likelihood of action potential

Specialized neurotransmitters

Different brain systems are sensitive to different transmitters, chemical specificity