Lecture 3

Question 1

what is the nervous system specialized for?

Answer 1

The transmission of electrical impulses between cells

Question 2

electrical impulses can be generated due to what?

Answer 2

The membrane potential maintained by neurons

Question 3

what is the asymmetric distribution of ions responsible for?

Answer 3

The membrane potential and the transmission of impulses

Question 4

what are the two parts of the nervous system?

Answer 4

1. Central nervous system - brain, spinal cord

2. Peripheral nervous system - limbs

Question 5

what are the two main types of cells in the nervous system?

Answer 5

1. Neurons - send and receive electrical impulses

2. Glial cells - help to support the function of neurons

Question 6

what do sensory neurons do?

Answer 6

they are specialized for the detection of stimuli.

• touch, taste
• detect and bring to brain

Question 7

what do motor neurons do?

Answer 7

transmit signals from the central nervous system to the muscles and glands they innervate
- sending a response back

Question 8

what do interneurons do?

Answer 8

process signals and transmit information between parts of nervous system
- connects neurons to other neurons

Question 9

what do microglia do?

Answer 9

• fight infections and remove debris

- remove waste at much higher capacity when sleeping

Question 10

what do oligodendrites and schwann cells do?

Answer 10

• form the myelin sheath around neurons and peripheral nerves
• help nerves fire at a faster rate

Question 11

what do astrocytes do?

Answer 11

• Control access of blood-borne components into the extracellular fluid around the nerve cells
• form blood brain barrier - helps keep pathogens out, more permeable when we sleep

Question 12

what are the two processes of the cell body?

Answer 12

• dendrites: receiving process

- axons: conducting process

Question 13

what is the axoplasm?

Answer 13

the cytosol within an axon

Question 14

what is the mylein sheath

Answer 14

• it’s discontinuous and surrounds many axons
• insulate segments of axons so that the signal strength is not lost - helps travel long distances much quicker
• separated by nodes of Ranvier

Question 15

what is a synaptic bouton and what do they do?

Answer 15

it is where the neuron is connected to the next cell and it helps transmit the signal to the next cell

Question 16

what is synapse?

Answer 16

• The junction between a nerve cell, gland or muscle cell

- for neuron to neuron junctions - typically occur between an axon and a dendrite

Question 17

what is the membrane potential?

Answer 17

voltage difference across a membrane

Question 18

what kind of membrane potential do cells at rest normally have?

Answer 18

• excess negative charge on the inside of the cell

- positive charge on the outside of the cell

Question 19

what do leak channels do?

Answer 19

allow ions to move down electrochemical gradient

Question 20

what does the sodium potassium pump do?

Answer 20

• moves sodium out and potassium into the cell against an electrochemical gradient
• three sodium’s out and two potassium’s in - more positive out - inside is more negative

Question 21

what is depolarization?

Answer 21

switching their membrane potential from negative to positive quickly

Question 22

what is hyper polarization/ Repolarization?

Answer 22

switching the membrane potential back to negative from positive

Question 23

what do excitable cells have in their plasma membrane’s?

Answer 23

ion channels

Question 24

what are ion channels?

Answer 24

integral membrane proteins that form ion-conducting pores in the lipid bilayer

Question 25

what do voltage gated ion channels respond to?

Answer 25

changes in the voltage across a membrane | - allows depolarization which allows signals

Question 26

when do ligand gated ion channels open?

Answer 26

when a ligand binds to the channel

Question 27

what does patch clamping record?

Answer 27

currents passing through individual channels

Question 28

What does an amplifier do?

Answer 28

keeps the membrane at a fixed membrane potential despite changes and it’s electrical properties

Question 29

what does the voltage clamp measure?

Answer 29

tiny changes in current flow through individual channels

Question 30

what are voltage gated potassium channels/ what are they like?

Answer 30

- Multimeric proteins - composed of four protein subunits - quaternary - each domain or subunit contains six transmembrane alpha helices

Question 31

what are voltage gated sodium channels/ what are they like?

Answer 31

- Large monomeric proteins with four separate domains - One big structure - tertiary - each domain or subunit contains six transmembrane alpha helices

Question 32

what do oxygen atoms in the amino acids at the centre of the channel do?

Answer 32

they are positioned to interact with ions as they move through the selectivity filter - allows ions to give up their waters of hydration

Question 33

are the channels hydrophilic or hydrophobic?

Answer 33

they are hydrophilic - don’t have to worry about hydrophobic tail

Question 34

What happens when voltage gated sodium channels respond to stimuli?

Answer 34

they can open rapidly and then close again. The open or close state is all or none

Question 35

what is channel inactivation?

Answer 35

- A secondary type of closed state in voltage gated channels. - it cannot reopen immediately even if stimulated to do so - inactivating particles found inside cytosol can close the channel - Plugs the channel which makes it unresponsive to detecting voltage for a certain period of time so it cannot fire a signal until the channel is unplugged