Synaptic Communication (Exam 1)

What is the resting membrane potential?

~ -70 mV

What is the distribution of Na⁺ and K⁺?

Na⁺ high outside, K⁺ high inside

What does the Na⁺/K⁺ pump do?

3 Na⁺ out, 2 K⁺ in (uses ATP)

Where does the action potential (AP) begin?

Axon hillock

What happens when the AP reaches the terminal?

Triggers neurotransmitter release

What does AP arrival cause at the terminal?

Depolarization of terminal

What channels open when the AP arrives?

Voltage-gated Ca²⁺ channels

What enters the cell during neurotransmitter release?

Ca²⁺

What is the role of Ca²⁺ in neurotransmitter release?

Triggers vesicle fusion

Where do vesicles dock?

Active zone

What are the key proteins involved in vesicle fusion?

SNARE proteins

What is the function of SNARE proteins?

Pull vesicle → membrane

What is exocytosis?

Vesicle fusion → neurotransmitter release

What is endocytosis?

vesicle membrane removed fro cell membrane and recycle through local uptake

Does the membrane build up during neurotransmitter release?

No

How is the membrane recovered after neurotransmitter release?

Endocytosis

What structure helps with vesicle recycling?

Endosome

What is the size of the synaptic cleft?

20-50 nm

How does the neurotransmitter cross the synaptic cleft?

Diffusion

What happens after the neurotransmitter crosses the cleft?

Binds postsynaptic receptors

Why is it important to clear neurotransmitters?

Prevent continuous activation

What is the main method for clearing neurotransmitters?

Reuptake transporters

What cells assist in neurotransmitter recycling?

Astrocytes

What are glutamate and GABA converted into?

Glutamine

What is the purpose of glutamine in neurotransmitter recycling?

Reused to make neurotransmitter

What enzyme breaks down acetylcholine (ACh)?

Acetylcholinesterase

What are the breakdown products of ACh?

Choline + acetate

What happens to choline after ACh breakdown?

Reuptake → reused

What is the effect of reuptake blockers?

Increase neurotransmitter in cleft

What does cocaine block?

Dopamine, serotonin, norepinephrine

What do SSRIs do?

Increase serotonin availability

Where are receptors located?

Postsynaptic membrane

What are receptors?

Membrane proteins with ligand binding site

What is a ligand?

Molecule that binds receptor

What are the two classes of receptors?

Ionotropic + metabotropic

What is the mechanism of ionotropic receptors?

Direct ion channel

How fast are ionotropic receptors?

Fast

What is the duration of ionotropic receptor action?

Short

What is the mechanism of metabotropic receptors?

G-protein → second messenger

How fast are metabotropic receptors?

Slow

What is the duration of metabotropic receptor action?

Long-lasting

Can one neurotransmitter use multiple receptors?

Yes

What determines the effect of a neurotransmitter?

Receptor type (not NT itself)

What blocks NMDA receptors at rest?

Mg²⁺

What removes the block from NMDA receptors?

Depolarization

What ions pass through NMDA receptors?

Na⁺, Ca²⁺, K⁺

What is EPSP?

Depolarization (Na⁺ in, usually glutamate)

What is IPSP?

Hyperpolarization (K⁺ out or Cl⁻ in, usually GABA)

What is spatial summation?

Multiple synapses at same time

What is temporal summation?

Rapid repeated input from one synapse

Where does summation occur?

Axon hillock

What is long-term potentiation (LTP)?

Strengthened synapse after repeated activity

What does LTP underlie?

Learning and memory

Why does the balance of excitation/inhibition matter?

Maintains normal brain function

What happens with loss of inhibition?

Overactivation (e.g., tetanus)

What can too much excitation cause?

Epilepsy

What other disorders are linked to excitation/inhibition imbalance?

Autism, schizophrenia

Describe Tetanus

Bacteria that degrades SNARE proteins needed for vesicle exocytosis. Loss of inhibition results in uncontrolled motoe neuron activation and massive muscle contraction