Topic 6 Nervous System: Transmission Across a Synapse

Question 1

• A signal is transmitted across a synapse by traveling from the pre-synaptic neuron to the post-synaptic neuron

Answer 1

What happens

Question 2

• Electrical

- Chemical

Answer 2

Types of Transmission

Question 3

• bidirectional action potential that travels along membranes of gap junctions; is less common in the body, fast, and found in cardiac and visceral smooth muscle

Answer 3

Electrical Transmission

Question 4

• an unidirectional action potential that is most typical in animal cells

Answer 4

Chemical Transmission

Question 5

1. Ca2+ gates open
2. Synaptic vessels release neurotransmitter
3. Neurotransmitter binds with postsynaptic receptors
4. Postsynaptic membrane is excited or inhibited
5. Neurotransmitter is degraded/ recycled/ diffused away

Answer 5

Steps of Transmission Across Chemical Synapse

Question 6

• depolarization allows Ca2+ to enter the cell via VDCC’s

Answer 6

Ca2+ gets open

Question 7

• influx causes release of neurotransmitters into the synaptic cleft

Answer 7

Synaptic vessels release neurotransmitter

Question 8

• diffusion via Brownian motion and binding

Answer 8

Neurotransmitter binds with postsynaptic receptors

Question 9

• Excitatory postsynaptic potential

- inhibitory postsynaptic potential

Answer 9

Postsynaptic membrane is excited or inhibited

Question 10

• Na+ gates open and membrane is depolarized; if threshold potential is succeeded, an action potential is generated

Answer 10

Excitatory postsynaptic potential

Question 11

K+ gates open and membrane is hyperpolarized; it becomes more difficult to generate an action potential

Answer 11

Inhibitory postsynaptic potential

Question 12

• neurotransmitters are broken down by enzymes in the cleft, reuptake, or diffused

Answer 12

Neurotransmitter is degraded/ recycled/ diffused away

Question 13

• Diameter

- Myelination

Answer 13

Factors that alter the rate which impulses travel

Question 14

• greater diameter allows an impulse to propagate faster since a larger diameter results in a less resistance to the flow of ions (think of passing water through a large pipe)

Answer 14

Diameter

Question 15

• heavily myelinated axons allow impulses to propagate faster since Na+ ions can’t leak out, thereby driving saltatory conduction to occur faster

Answer 15

Myelination