Synapse

Question 1

What is an EPSP?

Answer 1

Excitatory Postsynaptic Potential: Depolarization (Na⁺/Ca²⁺ influx) that promotes neuron firing. Decays passively toward axon hillock.

Question 2

What is an IPSP?

Answer 2

Inhibitory Postsynaptic Potential: Hyperpolarization (Cl⁻ influx/K⁺ efflux) that suppresses firing. Acts locally (no propagation).

Question 3

Can IPSPs summate?

Answer 3

✅ Temporally (same synapse, rapid inputs). ❌ Spatially (no spread to combine with other IPSPs).

Question 4

Types of synapses?

Answer 4

1. Chemical (neurotransmitters) 2. Electrical (gap junctions). Chemical dominate in humans.

Question 5

Chemical synapse steps?

Answer 5

1. AP → Ca²⁺ entry 2. Vesicle fusion 3. NT release 4. Receptor binding → EPSP/IPSP.

Question 6

Electrical synapse features?

Answer 6

Fast, bidirectional (via connexons). Found in heart, retina, reflexes.

Question 7

Botulinum toxin mechanism?

Answer 7

Cleaves SNARE proteins → blocks ACh release → flaccid paralysis (e.g., botulism, cosmetic Botox).

Question 8

Tetanus toxin mechanism?

Answer 8

“Blocks glycine/GABA release in spinal cord → spastic paralysis (lockjaw, rigid muscles).