Nervous System Activities: Neurotransmission

Question 1

How does an action potential pass from one presynaptic neuron to a post synaptic neuron.

Answer 1

• Via chemical signals of neurotransmitters.

Question 2

Name and describe the function of the two types of synapeses.

Answer 2

• electrical: direct physical contact betwene two cells at gap junctions, an action potential is transmitted quickly and efficiently, located in the CNS and PNS but are rare, connected by connexons.
• chemical: most common, cells are not in contact, communication between neuron to neuorn and neuron to other cell, information is transmitted by chemcalled called neurotransmitters found in synaptic vesicles.

Question 3

Describe the process of neurotransmission.

Answer 3

1. Action potential arrives at the axon terminal
2. Voltage gated calcium ion channels open and calcium enters the axon terminal
3. Calciums entr causes neurotransmiter-containing synaptic vesicles to release their contents via exocytosis.
4. Neurotransmitters diffuse across the synaptic cleft and bind to complementary receptors on the post-synaptic membrane.

Question 4

What are the two types of neurotransmitters?

Answer 4

• Excitatory neurotransmitters (e.g., acetylcholine)
• inhibatory neurotransmitters (e.g., GABA)

Question 5

What is the role of a excitatory neurotransmitter?

Answer 5

• causes the membrane potential to become positive (depolerisation)
• promotes the generation of an action potential in the post-synaptic cell - promotse membrane potential to -60 mili volts.

Question 6

What is the role of an inhibatory neurotransmitter?

Answer 6

• causes membrane potential to become more negative than the resting membrane potential (hyperpolerisation)
• inhibits the generation of an action potential to be carried through the postsynaptic cell.

Question 7

How does the postsynaptic neuron process information from neurotransmitters?

Answer 7

• postsynaptic potentials: graded potentials develop in postsynaptic cells in response to neurotransmitters
• excitaroy post synaptic potential - depolerises membrane
• inhibatory post synaptic potential - hyperpolerises membrane more further away from threshold (-90 mili volts)

Question 8

What is summation and what are the two types?

Answer 8

• A process where the effects of all graded potenials are intergrated at one region of the plasma membrane i.e. all excitatory, all inhibitory or both excitatory and inhibitory.
• temporal and spatial summation

Question 9

What is temperal summation + the process?

Answer 9

• occurs on a membrane that recieves two depolerizing stimuli from the same soruce in rapid sucession. The effects of the second stimulus are added to those of the first.
• process:
  1. first stimulus arrives
  2. second stimulus arrives and is added to the first stimulus
  3. action potential is generated.

Question 10

What is spatial summation + the process?

Answer 10

• occurs when sources of stimuklation arrive simulatenously, but at different locations. Local currents spread the depolerizing effects, and areas of overlap experience the combined effects.
• process:
  1. two stimuli arrive simultaneously
  2. acion potential is generated

Question 11

What is and what are the two types of pre-synaptic modulation?

Answer 11

• Ability of passing on a signal might be affected before the release of a neurotransmitter.
• presynaptic excitation: increases neurotransmitter release from the pre-synaptic neuron because the action potential is comming from two neurons at the same time - spatial summation. Therefore more calcium is released, so more neurotransmitters are released.
• presynaptic inhibition: decreases neurotransmitter release from the pre-synaptic neuron. GABA is released, causing an inactiviation of calcium ion channels, threfore less neurotransmitters are released.

Question 12

How may neurotransmission be stopped?

Answer 12

• degredation by enzymes
• neurotransmitters diffsue away from the synaptic cleft
• neurotransmitters enter the pre-synaptic cell through endocytosis
• GABA act as a presynaptic inihibitor - reducing the release of neurotransmitters
• drugs or toxins block the receptor on post-synaptic cells.