Lecture 25: The Nervous System

Question 1

What are the 3 different neuronal types?
Also how do neurons transmit information?

Answer 1

sensory neurons, interneurons, and motorneurons
Neurons transmit information through propagated changes in membrane potential, known as action potentials

Question 2

Neurons

Answer 2

Nerve cells that transfer information within the body

Question 3

What types of signals do neurons use?

Answer 3

Electrical signals-for long distance
Chemical signals-for short distance

Question 4

Ganglia, Brain

Answer 4

This is where processing of information takes place
Ganglia-simple clusters of neurons
brain- more complex organization of neurons

Question 5

What are the 3 steps of information processing?

Answer 5

1. Sensory input (information)
2. Integration (brain processes information)
3. Motor output (reaction)

Question 6

Explain the process of neurons transmitting information

Answer 6

1. A neuron (dendrite specifically) recieves information and transmits it to the cell body
2. It is then transmitted along an axon. The axon hilock connects the axon and cell body and this is where the action potential is generated
3. Electrical impulses PROPOGATE down the axon in 1 direction
4. The signal reaches the synaptic terminal in which the information is passed across the synapse to another neuron (postsynaptic cell)

Question 7

How do neurons cells divide

Answer 7

THEY DONT LOL. Goes through apoptosis (cell death) if they did divide. Neurons are the most precious cells in the body

Question 8

What is glia, what are the 5 types?

Answer 8

Cells that nourish or insulate most neurons
1. astrocytes- support and nourish neurons that forms blood barriers
2. Ependymal- promote circulation of cerebrospinal fluid
3. Microglia- protect the nervous sytem from microorganisms (prevent viruses in brain)
4. Oligodendrocytes (CNS) and Schwann cells (PNS) form myelin sheath around axons

Question 9

Membrane potential

Why is membrane potential important

Answer 9

The difference in electrical charge between extracellular space and inside of the cell.

Messages are transmitted as changes in membrane potential

Question 10

Resting potential

Answer 10

Membrane potential of a neuron is not sending signals (resting potential is around -70 mV)

Question 11

What would happen if ion pumps (such as the Na+/K+ Pump) was nonfunctional?

Answer 11

The ion concentration gradients across the membrane would disappear

Question 12

Explain how the Sodium/Potassium pump works

Answer 12

1. Na+ binds to pump with high affinity for Na+ ions
2. 3 Na+ ions bind and stimulates phosporylation of a kinase using ATP
3. Change in protein shape reduced affinity for Na+; 3 Na+ are removed
4. New shape has high affinity for K+, so 2K+ bind on extracellular side triggering release of phosphate
5. Loss of phosphate group restores original shape
6. 2 K+ are released and Na+ affinity is high again

Question 13

What contributes to the resting membrane potential?

Answer 13

• A neuron at resting potential contains many open K+ leak channels and fewer Na+ channels as K+ diffuses out th ecell
• Anions trapped inside the cell contribute to the negative charge within a neuron
• Sodium potassium pump also sends 3 Na+ ions out the cell and only 2 K+ inside the cell which resulting in a negaitve membrane potential

Question 14

Voltage gated ion channel

Answer 14

Neurons contain voltage gated ion channels that open or close in response to stimuli (change in membrane potential)

Question 15

Voltage gated sodium channel

Answer 15

importnat for depolarizing the membrane (more positive) during action potentials. Opens rapidly allowing influx of sodium
- closed at resting potentials
- Opened when membrane is depolarized

Question 16

Action potential

Answer 16

A nerve impulse or signal that carries info along axon
- Action potential triggered by depolarization that reaches threshold at -55 mV which is an all or none response (stimulus must be strong enough to create action potential)

Question 17

How many action potentials can neurons produce? Also the frequency of action potentials reflect what?

Answer 17

1. up to hundreds of action potentials/second
2. The frequency of action potentials can reflect strength of a stimulus

Question 18

What are the steps of the generation of an action potential?

Answer 18

1. Resting state- channels are closed
2. Depolarization- SOME Na channels open
3. Rising phase of action potential- MOST gated Na channels open and Na floods in cell
4. Falling phase of action potential- gated Na channels close and most K channels open
5. Undershoot- Voltage gated K channels close
6. Resting potential is restored