Lecture 10

Question 1

Why can’t action potentials move in 2 directions?

Answer 1

Due to the refractory period-propogation must travel away from the site of initial stimulation

Question 2

What is myelination?

Answer 2

Oligodendrogliain CNS and Schwann Cells in PNS-speeds up neural impulses (200m/s).

Question 3

What are the Nodes of Ranvier?

Answer 3

Tiny gaps in the myelin-use saltatory conduction to propagate the action potential at successive nodes of ranvier.

Question 4

Why do action potentials remain the same size across the axon?

Answer 4

Because they are an all-or-none response.

Question 5

What does myelination and the nodes of ranvier result in?

Answer 5

Faster electrical signal that doesn’t dissipate.

Question 6

Is neural transmission instantaneous?

Answer 6

No. There is a finite amount of time between sense organs detecting phenomena and perception of the phenomena.

Question 7

What is the excitatory post synaptic potential (EPSP)

Answer 7

Brief depolarization of a membrane in response to stimulation-more likely to produce an action potential.

Question 8

What is the inhibitory post-synaptic potential (IPSP)

Answer 8

Brief hyperpolarization of a neuron in response to stimulation-less likely for an action potential.

Question 9

What are the two ways that neurons integrate information?

Answer 9

Temporal summation and spatial summation

Question 10

What is temporal summation?

Answer 10

Pulses that occur at approximately the same time on a membrane are summed.

Question 11

What is spatial summation?

Answer 11

Pulses that occur at approximately the same location on a membrane are summed.

Question 12

What is being summed in these 2 events?

Answer 12

EPSP- Influx of Na+ ions

IPSP- Efflux of K+ ions or influx of Cl- ions.

Question 13

What is the initial segment?

Answer 13

Overlaps with the axon hillock, it is rich in voltage sensitive channels, and is where EPSPs and IPSPs are integrated and action potentials start.

Question 14

What is back propogation?

Answer 14

Reverse movement of an action potential into the dendritic field-some neurons may have voltage gated channels on dendrites.

Question 15

What do voltage gated channels on dendrites do?

Answer 15

, which may underlie some of the plastic changes in learning and memory-makes dendritic field refractory and reinforces signals coming into certain dendrites.

Question 16

What are stretch sensitive receptors?

Answer 16

Ion channel on tactile sensory neuron that activates in response to stretching of the membrane, initiating a nerve impulse-causes stretch sensitive membrane to open, allowing an influx of Na+.

Question 17

What is an end-plate?

Answer 17

Receptor/ion complex that is activated by the release of the neurotransmitter acetylcholine: Action potential starts-produces contraction of muscle fibres.

Question 18

How does sensory info get into the nervous system?

Answer 18

Sensory info is transmitted to the brain, info is processed and a decision to respond (pull away or not) is generated, muscle neurons generate action potentials to make muscles contract.

Question 19

What is myasthenia gravis?

Answer 19

Autoimmune disease where the body attacks the end-plate receptors on muscles. By consequence, the receptors become less sensitive to Na+ and K+ ions.

Question 20

How do we cure myasthenia gravis?

Answer 20

Surgery or pharmacological intervention-try to keep acetylcholine in the synapse for longer so it might activate something

Question 21

What is the hard question of consciousness?

Answer 21

How is it that the movement of ions across a cell membrane translates to a rich perceptual experience of consciousness? (all you are is sodium and potassium moving around)

Question 22

Who was Otto Loewi?

Answer 22

Won the nobel prize in physiology/medicine (1936)-discovery of chemical transmission of nerve impulses (using frog hearts)

Question 23

How did Otto Loewi discover the chemical transmission of nerve impulses?

Answer 23

Stimulated a frog heart in water, which decreased beating. Took a second frog heart and allowed fluid transfer. Stimulating the first frog heart caused the same change in the second frog heart.

Question 24

What was Otto Loewi’s conclusion?

Answer 24

There must be a chemical released by a nerve that is the basis for communication between neurons. Also discovered acetylcholine (inhibits heart rate and activates muscles) and epinephrine (speeds up heart rate, adrenaline).

Question 25

What are neurotransmitters?

Answer 25

Chemicals released by a neuron onto a target with an excitatory or an inhibitory effect.