Week 1- Part 3- Resting potential.

Question 1

What is this overall about?

What happens when neurons are resting?

Answer 1

How neurotransmission works.

Still doing a lot.

Question 2

The Nervous System:

What is the Central Nervous System (CNS) comprised of?

Where is it encased?

Answer 2

Brain + spinal cord.

Within the skull and spinal column.

Question 3

Continuation from the nervous system

What is the Peripheral Nervous System (PNS) comprised of?

Answer 3

Nerve tissue located outside of the brain and spinal cord.

Question 4

When it comes to psychoactive drugs, what are we looking at mostly?

What about cocaine?

Answer 4

What it does to the central nervous system- that’s where your psychology is.

Its anesthetic effects- what it does to the peripheral nervous system.

Question 5

Cells for the nervous system:

What is there inside our central nervous system?

Name one cell and what they do.

What do neurons do?

What does transmitting signals lead to?

Answer 5

Lots of different types of cells.

Glial cells- provide metabolic support, protection, and insulation for neurons.

Transmit signals within the nervous system.

Transmit signals = process information- happens through that.

Question 6

What does the soma do?

What do the dendrites do?

Answer 6

Cell body; contains nucleus and other organelles- leads to the dendrites.

Projections from the soma that receive information- essentially receive signals from other neurons.

Question 7

What is the axon?

What is the axon hillock?

Answer 7

Extension that conducts electrical signals from the cell body to the terminal buttons- the terminal buttons form synapses with dendrites of other neurons.

Where action potentials start- whether or not a neuron fires depends on what happens here.

Question 8

Is there lots of different types?

Explain the cell body of neurons?

Answer 8

Yes- some have more dendrites than others and some have short or long axons.

Cell body of neurons- in the cortex- reside in cerebral grey matter- axons form the white matter connecting cells to each other.

Question 9

What are we interested in?

How many elements are there to this?

Are there different orders through which the sequence could be studied?

Answer 9

The process by which signals leave a neuron and travel down the axon and stimulate other neurons.

Two- how signals are transmitted within neurons, then when they get to a synapse, how they are transmitted between neurons.

Yes- we learn one way- before telling us what gets a neuron to start firing, we learn how signals travel within neurons then how they jump from one neuron to the next and how they get that neuron to fire.

Question 10

How do signals travel within neurons:

What has happened to the neurons we are speaking about?

What does it depend on?

What is the membrane?

Answer 10

They have been stimulated- there will be a signal travelling down its axon.

The cell membrane that encases the neuron.

The membrane is a highly complex piece of machinery- it is responsible for generating and propagating signals, the action potentials- not a rigid structure.

Question 11

What is the cell membrane also?

What is it permeable to?

Answer 11

Lipid bilayer- a layer of fatty molecules separating the external world from the internal world- from the interior of the cell to the exterior of the cell.

Permeable to some things + not permeable to other things- some things can travel through it quite easily and other things cannot.

Question 12

What is inside the cell membrane?

What is it?

Does the channel let things through?

Answer 12

Lots of really important structures.

Special channels- let charged molecules (ions) in or out of the cell- channels can be opened or closed, depends on circumstances- can be in response to electrical things happening or neurotransmitters doing stuff to them.

Yes- in certain circumstances- but the cell membrane is impermeable to some things, does not let it in or out.

Question 13

What happens when a neuron is at rest?

How do we know this?

Answer 13

Uneven distribution of charged ions across the cell membrane- slight excess of negatively charged ions on the inside compared to the outside.

Stick an electrode inside and outside the neuron- inside, particularly of the axon, is slightly more negatively charged than the outside.

Question 14

How much more negatively charged?

Is this what a neuron is like when it is resting?

Answer 14

-70 million millivolts (or even -65, in that range) more negatively charged- number varies- depends on the type of neuron.

Yes- it is working hard to keep it like this- called a neuron at rest.

Question 15

Most important ions- Ions contributing to resting potential:

What is the most important positively charged ion?

What is the most important negatively charged ion?

What is another important positively charged ion?

Answer 15

Sodium (NA+)- Higher concentration outside, than inside.

Chloride (CL)- Higher concentration outside, than inside.

Potassium (K+)- Higher concentration inside, than outside.

Question 16

Continuation from most important ions- Ions contributing to resting potential:

For the negatively charged protein ion, where is there more?

Where does a slight negative charge on the inside relative to the outside come from?

Answer 16

Negatively charged proteins (A-)- many more inside- trapped here.

Comes from when you add all these positives and negatives together, will have slightly more negative stuff on the inside than the outside.

Question 17

Look at the picture in the doc and answer the following questions:

What can you say about the blue sodium ions?

What can you say about the green chloride ions?

What can you say about the orange potassium ions?

What should you not worry about now?

What about the black molecules?

Answer 17

Slightly more on the outside- they are positively charged.

Slightly more of them on the outside.

Slightly more of them on the inside.

Calcium ions.

Black molecules- big negatively charged protein molecules stuck on the inside- Have an imbalance.

Question 18

Ionic basis of the resting potential:

How should you think of the particles?

What is homogenising?

What is the rate of diffusion affected by?

Answer 18

As wanting to try to go somewhere.

Molecules do it- random motion- particles move down their concentration gradient- means they move from high concentration to less concentration- due to kinetic energy, will be evenly distributed, stops here- through a process of diffusion.

Temperature, size of molecules and steepness of the concentration gradient.

Question 19

Continuation from ionic basis of the resting potential:

Do other forces come into play?

What happens if the membrane is positively charged on one side and negatively charged on the other?

Answer 19

Yes- electrostatic pressure- positively charged ions repel each other- negatively charged ions + positively charged ions will attract each other.

The positively charged ions (potassium) will have this tendency to try and get to the other side- are attracted through electrostatic forces as well- driven out by concentration gradient.

Question 20

Factor contributing to uneven distribution:

Why does the membrane stay in a situation where the ions are unevenly distributed?

Can they get in?

Answer 20

Membrane is selectively permeable- does not let all cross- even if there is a high concentration of positive ions (sodium) outside which are trying to get in due to the concentration gradient + are attracted to the negative ions inside.

No- membrane wont let them- when they go get in, the sodium potassium pump which is inside pumps them back out- it pumps sodium out and potassium in- it helps keep the distribution uneven- this keeps the membrane polarised.

Question 21

Neuron’s resting membrane potential:

Where is negatively charged?

What is it called?

What is it?

What is the general thing to remember?

Answer 21

Inside of the neuron- relative to the outside.

Called the resting membrane potential- -70 mv- the membrane is polarised, carries a charge.

Membrane at rest- before an action potential is generated.

Slightly negatively charged inside than it is on the outside.

Question 22

Extra information:

What passes readily through?

What has little movement?

What happens to the sodium ions?

What happens to the chloride ions?

What happens to the potassium ions?

What balances out when the neuron is resting?

Answer 22

K+ and CL- can be equilibrate.

NA+- tendency to flow in but blocked when channels closed.

Positively charged- want to get into the cell- can’t, membrane won’t let them.

Negatively charged- want to get through- can’t, membrane won’t let them through.

Positively charged- want to leave- get through- balance out- slightly more on the inside than the outside- are attracted to negative charge on the inside.

Chloride ions.