9/10 - The neuron/Synaptic Transmission

Question 1

Who was the first to demonstrate that individual cells comprising the nervous system remain separate?

Answer 1

Santiago Ramon y Cajal

Question 2

What are interneurons/intrinsic neurons?

Answer 2

Those whose dendrites and axons are completely contained within a structure.

Question 3

What do cerebellum Purkinje cells look like?

Answer 3

They branch extremely widely within a single plane.

Function is closely related to the shape of a neuron

Question 4

What is thiamine used for in the brain?

Answer 4

It is a chemical necessary for the use of glucose

Question 5

What is the sodium-potassium pump?

Answer 5

A protein complex that continually pumps three sodium ions OUT of the cell while drawing IN two potassium ions

This helps to maintain the electrical gradient across a cell’s membrane.

Question 6

What are the two types of action potential conductions used by neurons?

Answer 6

• Passive conduction (slow)

- saltatory conduction (fast)

Question 7

Define a nerve

Answer 7

A distinct peripheral extension of the CNS conducting electronic messages (Action potentials) to and from the CNS

They do not exist in the CNS, rather the CNS has tracts.

Question 8

What are the three layers of a nerve?

Answer 8

• Endoneurium (wraps each neuron)
• Perineurium (covers nerve bundles called fascicles)
• Epineurium (Covers fascicles)

Question 9

How is action potential intensity expressed?

Answer 9

impulses/sec

Question 10

Who discovered ACh and how?

Answer 10

Otto Loewi. He stimulated the vagus nerve and removed fluid sample. He then applied it to recipient heart and noticed heart rate slowing.

He found that vagusstoffll is actually ACh, showing that synaptic signalling used chemical messengers. (came to him in a dream as well…)

Question 11

Describe electrical synapses

Answer 11

Six connexins form a channel (connexon) and two connexons (one from each cell) form a gap junction channel. Many channels comprise one gap junction.

Pore large enough to allow cellular ions to pass through directly.

Question 12

List the functional properties of electrical synapses

Answer 12

• Ions/small molecules can pass in both directions
• Cells are electrically coupled
• Very fast, if synapse is large, fail-safe. An action potential in the presynaptic neuron can produce almost instantaneously an AP in the postsynaptic neuron

Question 13

Describe escape reflex mechanism in invertebrate species (eg. crayfish)

Answer 13

Electrical synapses found between sensory and motor neurons to mediate escape reflexes

Question 14

True or false? Electrical synapses are common in every part of the mammalian CNS?

Answer 14

True

For:

• Synchronization
• Developmental coordination
• Non neuron cells

They don’t usually produce postsynaptic potentials (PSP) large enough to trigger an AP in the postsynaptic cell

Question 15

Define the two types of synapses based on size and shape

Answer 15

Gray’s type I: asymetrical (thick postsynaptic membrane). Excitatory.

Gray’s type II: Symmetrical. Inhibitory

Larger synapses have more active zones.

Question 16

List four examples of CNS synapses

Answer 16

• axodendritic
• Axosomatic
• Axoaxonic
• Dendrodendritic

Question 17

Give five requirements of chemical synaptic transmission

Answer 17

1. Able to synthesize and pack NT
2. Able to release vesicular content
3. Able to produce electrical/biochemical resposne to NT
4. Able to remove NT from cleft
5. Events occur very rapidly for sensation, perception and control of movement.

Question 18

What is a SNARE?

Answer 18

SNAp REceptor

SNAP: Soluble NSF attach protein

NSF: N-ethylmaleimide-sensitive factor

Synaptic vesicles bind with SNAP-25 (syntaxin and synaptobrevin) that is associated with a calcium channel. Influx of calcium causes vesicle fusion with presynaptic membrane =,

Question 19

True or false? Potassium channels cause depolarization and are excitatory?

Answer 19

True…

Question 20

What do nerve agents do?

Answer 20

Inhibit the enzyme AChE (prolonging ACh transmission)

Question 21

What is synaptic integration?

Answer 21

The process by which multiple synaptic potentials combine within one postsynaptic neuron

Question 22

What is patch clamping good for?

Answer 22

Measuring ion movements through a single channel (not only in whole cell)

Question 23

What is temporal summation?

Answer 23

In synaptic integration, when the same presynaptic fibre fires APs in quick succession, the individual EPSPs add together

Question 24

What is shunting inhibition?

Answer 24

Inhibiting current flow from soma to axon hillock

• Binding different NTs can allow different ions to pass through channels
• IPSPs can be generated when ion channels are opened causing hyperpolarization of membrane
• Shunting inhibition is inward movement of Cl anions that negate the outward flow of positive ions, inhibiting current flow from some to axon hillock

Question 25

Where are spines located in excitatory/inhibitory synapses?

Answer 25

Excitatory (gray’s type I): Spines at excitatory synapses

Inhibitory (Gray’s type II): clustered on soma and near axon hillock