L18 - nerve cells & excitability: resting memb potential

Question 1

what is a neurone?

Answer 1

• nerve cell
• most in CNS (brain + spinal cord)
• post mitotic cells (fully differentiated and unable to divide)

Question 2

cell body of neurone

Answer 2

• aka soma
• cytoplasm
• nucleus
• mitochondria
• LACK OF CENTRIOLES (used in cell division)

Question 3

dendrites

Answer 3

• branches on cell body
• send electrochemical signals to cell body + axon

Question 4

axon

Answer 4

• transports A.P across from cell body to terminals

Question 5

nerve fibre

Answer 5

• some axons are very long
• myelin sheath covers axons so A.P can jump from node to node to get past quicker
• saltatory conduction
• Schwann cells produce this lipid
• when axon is covered with this it is known as nerve fibre

Question 6

how do nerve cells communicate with each other?

Answer 6

• through dendrites and axons
• to terminals

Question 7

multipolar neurone

Answer 7

• one axon
• lots of dendrites
• most common

Question 8

bipolar neurone

Answer 8

• 2 axons which come out from each side of cell body

Question 9

unipolar neurone

Answer 9

cell body is extended off axon (cell bodies still in the middle)

Question 10

anaxonic neurone

Answer 10

• no axon

Question 11

afferent neurone

Answer 11

carries sensory information from the body’s periphery to the central nervous system (CNS)

Question 12

efferent neurone

Answer 12

carries signals from the central nervous system (CNS) to muscles, glands, and organs in the body

Question 13

interneurone

Answer 13

neurone which transmits impulses between other neurones, especially as part of a reflex arc

Question 14

excitable cell

Answer 14

• neurone is an excitable cell
• cell that can be electrically excited to produce A.P

Question 15

examples of excitable cells

Answer 15

• neurones
• muscular cells
• some endocrine cells

Question 16

examples of non-excitable cells

Answer 16

red blood cells

Question 17

what is resting membrane potential?

Answer 17

electrical charge across plasma membrane (inside is more negative than outside)

Question 18

what can resting membrane potential do in excitable cells?

Answer 18

change via stimulation

Question 19

resting membrane potential of excitable cells

Answer 19

-50mV to -85mV

Question 20

selective permeability of lipid membrane

Answer 20

• lipid soluble molecules easily pass
• charged ions/ proteins can’t without carrier/ transporter
• so Na+, K+, Cl- can’t pass

Question 21

electrical gradient

Answer 21

gradient based of charge

Question 22

as you increase conc of oppositely charged ions, what happens?

Answer 22

increase in forces of attraction

Question 23

facilitated diffusion

Answer 23

• ions diffuse down conc gradient
• selectively permeable to diff ions
• the one that doesn’t need to open and close
• memb spanning protein

Question 24

active transporters (pump)

Answer 24

• moves ions against conc gradient
  -na+/k+ channel
• uses atp to open and close

Question 25

K+ channels are usually...

Answer 25

leaky

Question 26

Na+/K+ pump to maintain excitability

Answer 26

- maintains conc of Na+ and k+ - 2K+ IN - for every 3Na+ OUT - always working

Question 27

what is RMP in most neurones?

Answer 27

around -70mV (use this one when u see a graph)

Question 28

distribution of charged ions

Answer 28

- conc of ions inside and outside are diff - ions move down conc gradient - movement restricted by memb

Question 29

why is cell membrane more permeable to K+ than Na+?

Answer 29

- due to K+ leak channels - no Na+ leak channels - so Na+ cannot return to cell

Question 30

what happens when the Na+/K+ pump works?

Answer 30

- as the Na+/K+ pumps transport K+ into the cell, the conc of K+ increases - memb potential becomes more negative - so conc gradient of K+ increases - K+ begins to diffuse out to area of lower K+ conc - RMP established when the diffusion of K+ out of the cell is balanced by the rate of K+ influx from the pump - once this inward rate of K+ flow from the pumps  balances rate of K+ flow out of the cell through the leak channels a resting membrane potential stabilizes at  approximately -70mV.

Question 31

equilibrium potential (Eion), Nernst equation

Answer 31

Eion = RT/ zF x logn [ion]outside / [ion]inside - R= gas constant, 8.314 - absolute temp - F - faradays constant - z = valency of ion [ion] outside = ionic conc on outside of cell

Question 32

calculating resting memb potential (Vm), goldman equation

Answer 32

look at ppt