electrical properties of nuerons

Question 1

what is the basic unit for nervous system

Answer 1

nuerons … they generate electrical signals and communicate to other nuerons

Question 2

neuron basic features

• cell body
• one side there is

Answer 2

• that hosts nucleus and different organelles

- dentrites= receives signals from environment or other nuerons

Question 3

neuron electrical signals

Answer 3

travel from dendrites, across axon

then signal is relayed at axon terminal to another neuron

Question 4

what happens on axon terminal

Answer 4

info relayed chemically thru synpatic commiucation

Question 5

function of neuron

Answer 5

transform electrical info into chemical info

Question 6

main function of plasma membrane

Answer 6

act as barrier , distingushes intracellular components from the extra cellular space

Question 7

structure of membrane

Answer 7

phospholipids, contains hydrophilic head which is polar (faces the cytosol and extracellular space)

Question 8

phosolipid tails

Answer 8

hydrophobic
face each other
provide a very hydrophobic environment that is v impermeable to lots of molecules

Question 9

what can pass the membrane

Answer 9

• gases
• very small uncharged molecules
• very few small charged molecules

Question 10

what can not pass the membrane

Answer 10

ions

large charged molecules

Question 11

water passing through

Answer 11

water can pass the membrane if the driving force is very strong

Question 12

types of transport across membrane

Answer 12

1. diffusion ( only for gases) no requirement for engery
2. facilitaed diffusion HIGH —-> LOW

active transport requires ATP. L—->H

Question 13

facilitated diffusion applies to

Answer 13

molecules that are not permeable in the membrane tf they cant pass on their own

tf they need protein … channels or protein carriers

Question 14

active transport

Answer 14

energy required to move a substance across a membrane against its concentration gradient

Question 15

why does active transport need ATP

Answer 15

going from low conc to high conc

tf need to break energetic barrier of going against conc.

Question 16

the electrochemical gradient is

Answer 16

combination of concentration and charge differences across the membrane

driving force for ion transport

Question 17

nueronal membrane charge

Answer 17

negatively charged on cytoplasmic side

positively charged on extracellular side

Question 18

membrane potential:
charge Q
current I

Answer 18

• net imbalance of number of positively charged and negatively charged particles in a given place
• flow of electrically charged particles , in body fluids these are ions eg Na+, K+ , Cl-

Question 19

membrane potential:

voltage V

Answer 19

measure of potential difference between two points . In these points , one of them is more positive than the other .

Question 20

in the context of nuerons and their membranes , electrical voltage represents the

Answer 20

electrical potential energy gradient.

since one side is + and other side is - , the electrical potential energy will drive charged particles to go from one side to another

Question 21

electrical potential (voltage)

Answer 21

difference in charged between inside v outside of cell

Question 22

why does interior of cell have relative negative net charge in comparison to outside of the cell

Answer 22

ionic composition of cytoplasm

Question 23

membrane potential:
electrical gradient
-influenced by
-ions

Answer 23

–overall electrical charge

-positive ions would flow to areas of negative charge

Question 24

membrane potential :
chemical gradient
-influenced by
-ions

Answer 24

• individual conc. of a particular ion

- all ions move to areas of high conc. to low

Question 25

the direction an ion will move depends on

Answer 25

overall net effect of chem and electrical gradients

Permeability of membrane to ion (no channels = no movement even with strong gradient)

Question 26

How is the gradient maintained

Answer 26

Na is more conc. on outside cell and K more conc on inside.

when channels open, Na will enter cell and K will leave cell

this is promoted by the sodium potassium pump by maintaining ATP from the ATP molecule

Question 27

Na+-K+ Pump is a

Answer 27

P-type transport ATPase

Question 28

how much energy does Na K pump use

Answer 28

1/3 of cells energy

Question 29

what changes the shape and structure of the pump

Answer 29

Phosphorylation

exposing ion binding sites on to extracellular and cytosolic faces of the membrane

Question 30

Equilibrium potential

Answer 30

electrical potential difference that exactly counterbalances diffusion due to conc difference

Question 31

Ion Channels
present in
states
ion selectivity:

Answer 31

all cells , most sophisticated on electrically excitable cells

conducting and non-conducting states eg open and close … transition between states is ‘gating’

Na+,K+,Ca2+,Cl- or cations.

Question 32

Na+-K+ ATPase exchanger

pt1

Answer 32

1. binding cytoplasmic Na+ stimulates ATP (autophosphorylation)
2. Phosphorylation causes conformational change
3. Na+ is released outside and by doing that the pump exposes K+ binding sites

Question 33

Na+-K+ ATPase exchanger

pt2

Answer 33

4. binding the K+ triggers the release of phosphate
5. release of phosphate restores the original conformation
6. K+ is released and Na+ binding sites are exposed again in cytoplasm