lecture 26 - intro to neurons and resting potential Flashcards Preview

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Flashcards in lecture 26 - intro to neurons and resting potential Deck (38):
1

2 functions of neurons/nerve cells

1. building blocks of the nervous system 2. instruments of communication

2

sensory components

monitor environment and internal events

3

integrative components

process and store information

4

motor components

responses to sensory input or commands

5

human brain composed of

100 billion neurons

6

Inputs from other neurons (______ inputs) are received at the ________. The signal spreads _______ to the _____ _____. The ____ conducts ______ ______ away from the _____ (cell body), to the tips of the axon, where their synaptic ______ also called axon _______ communicate with other neurons.

Inputs from other neurons (_sensory_ inputs) are received at the _dendrites_. The signal spreads _passively_ to the _trigger_ _zone_. The _axon_ conducts _action_ _potentials_ away from the _soma_ (cell body), to the tips of the axon, where their synaptic _boutons_ also called axon _terminals_ communicate with other neurons.

7

2 types of signals used in communication and where they are used

electrical signals (dendrites, cell body, axon) + chemical signals (synapses)

8

is the resting potential of most cells in the body positive or negative

negative mate

9

excitable tissue =

suddenly respond to stimuli with a transient change in the resting potential (i.e action potential)

10

excitable tissues include

muscle fibres, neurons, some endocrine cells

11

2 methods for measuring intracellular potentials

- patch clamp technique - microelectrode

12

resting membrane potential (RMP)

electrical potential difference of 50-70mV across the membrane which results from the seperation of charge.

13

more positive inside the cell than out. TRUE/FALSE

FALSE. By definition outside the cell is zero. Because the potential inside the cell is less, it is considered negative.

14

electrons and ions are responsible for the potential difference across the membrane. Yeah or no.

NO! electrons are not. ONLY ions are responsible for the difference in charge.

15

potential outside the cell is defined as being equal to _, meaning that the absolute intracellular potential is usually ________.

potential outside the cell is defined as being equal to _0_, meaning that the absolute intracellular potential is usually _NEGATIVE_. ~-65mV

16

3 things RMP is due too

1. unequal Na+/K+ concentrations inside/outside the cell 2. unequal permeability of the cell membrane to Na+/K+ [3. electrogenic action of NaKATPase] - very small contribution

17

[K+] outside vs. inside cell

HIGHER INSIDE - inside = 100mM - outside = 5mM

18

[Na+] outside vs. inside cell

HIGHER OUTSIDE - inside = 15mM - outside = 150mM

19

[Cl-] outside vs. inside cell

HIGHER OUTSIDE - inside = 13mM - outside = 150mM

20

[Ca2+] outside vs. inside cell

WAY HIGHER OUTSIDE - inside = 0.0002mM - outside = 2mM

21

does calcium affect the RMP?

no it doesn't because the membrane is not permeable to them at rest

22

does chlorine affect the RMP?

no because Cl- is distributed passively - there are no active Cl- pumps in neurons. This is why it has the same equilibrium potential as RMP (-65mV)

23

What affect to the numerous, negatively charged proteins in the cytosol have?

they DO NOT AFFECT RMP because the membrane is totally impermeable to them

24

how are Na+/K+ concentration gradients maintained?

by the Na+/K+ pumps. 3Na+ out, 2K+ in

25

2 ion channels present in neurons (open/ closed at rest?)

1. non-gated "LEAK" channels - OPEN at rest 2. gated channels (VOLTAGE, LIGAND, MECHANICALLY) - usually CLOSED at rest

26

number of K+ leak channels vs. number of Na+ leak channels at rest. PK+/PNa = ?

PK+/PNa+ = 40/1

27

nervous system =

cns + pns

28

equilibrium potential

net flow of ions is zero, in spite of concentration gradient and permeability. Electrical gradient and concentration gradient are opposing each other. e.g. as each K+ moves out, a negative charge replaces it

29

Nernst equation

calculate the equilibrium potential for each ion Eion = 61.5mV (at 37 degrees c) x log [ion]o / [ion]i

30

what are the equilibrium potentials for 1. K+ 2. Na+ 3. Cl- 4. Ca2+

1. K+ = -80mV 2. Na+ = +60mV 3. Cl- = -65mV 4. Ca2+ = +120mV

31

interpretate the value of Eion of 120mV for Ca2+

you would require an opposing potential of 120mV inside the cell, to prevent entry of Ca2+, if the membrane was fully permeable to it.

32

what are Cl- and Ca2+ important in

synapses

33

fault in Nernst equation

only applies to a situation where the membrane is permeable to only one type of ion (leak channels for just one ion)

34

Glia cells?

leak channels only for K+. therefore, RMP = -80mV

35

the higher the permeability of a membrane to a particular ion, the...?

the greater the ability for this ion to shift the RMP towards its equilibrium position. e.g. small permeability to Na+ is why RMP is much closer to the E of K+.

36

Goldman equation

a way of calculating the RMP by taking into account both the concentration gradients and permeability ratio between Na+/K+

37

what's this and where would you find it?

Q image thumb

multipolar neuron - motor neurons - carry signal from the CNS out to an effector

38

What's this and where would you find it?

Q image thumb

unipolar neuron - sensory neuron (e.g. in the PNS)