PSYC Exam #2 - Neurotransmission

Neurotransmission

the signal conveyed to a target cell by chemical neurotransmitters; information flow is chemical

Synapse

junction where chemical information is transmitted from one neuron to another

Presynaptic

the neuron transmitting the signal

Postsynaptic

the neuron receiving the signal

Synaptic cleft

a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron

Vesicle

contain neurotransmitters; found in terminal buttons of presynaptic cells

Exocytosis

process by which neurotransmitters exit the terminal button

Neurotransmitter

chemicals that transmit information from one neuron to another

Receptor

membrane receptor proteins that are activated by neurotransmitters

Ion channel

proteins in the plasma membrane that form pathways to allow ion movement and creating electrical signals

Reuptake

the presynaptic terminal buttons re-absorbs neurotransmitters that were released into the synaptic cleft ; regulates levels of neurotransmitters available for signaling

Enzymatic degradation

an enzyme makes neurotransmitters inactive by changing their structure so that they’re no longer recognized by the receptor

Diffusion

neurotransmitters drift out of the synaptic cleft, where they are absorbed by glial cells

Excitation (excitatory neurotransmitter)

increases the likelihood that the neuron will fire an electrical signal

Inhibition (inhibitory neurotransmitter)

less likely that a neuron will fire an action potential

Divergence

condition in which one neuron signals many others

Convergence

condition in which many neurons signal fewer others

Steps of neurotransmission

1. Action potential arrives at a terminal button → calcium flows from outside of the neuron to inside of the terminal button

2. Vesicles move toward the end of the terminal button and membranes bind together

3. Neurotransmitter binds to postsynaptic receptor → ion channel opens

Role of Ca⁺ in neurotransmission

When a neuron is activated, Ca⁺ rushes inside and causes the vesicles to fuse with the axon membrane, releasing their neurotransmitters into the synapse to bind with postsynaptic receptors

• If calcium is too low, neural signaling weakens or fails 

Neurotransmitter vs. hormone

Neurotransmitters are local and effect cells in neighboring environment. Hormones are released into the bloodstream and target cells are far away to have an effect

Acetylcholine (ACh)

• produced in the brain (CNS)

• released by motor neurons controlling skeletal muscles

Glutamate

• excitatory

• released at the site of an injury

• can lead to cell death

GABA

• inhibitory

• medical uses (can balance out excess glutamate, general anesthetics, anti-anxiety/seizures)

• alcohol increases amount of GABA released

Dopamine

• reward/reinforcement, pleasure/addiction

• motor function

• hormone control

Serotonin

• emotions

• appetites

• aggression

• sleep

• sex

Norepinephrine

• attention (survival related)

• fight or flight/emergency responses

Opiates

• pain relief by blocking pain signals between brain and body

• people can develop tolerance to them/use for pleasure

• inhibit function of GI tract and increase infection probability

Otto Lowei’s discovery of the first neurotransmitter (ACh)

• Heart #1 was connected to the vagus nerve in one chamber that was connected to a second with Heart #2

• He electrically stimulated the vagus nerve of Heart #1, causing it to slow down

• After a delay, Heart #2 also slowed down