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PHGY 209 > nerve/synapse lectures 1-2 > Flashcards

nerve/synapse lectures 1-2 Flashcards

1
Q

what parts of nervous system are part of cns and pns

A

cns = brain and spinal cord
pns = everything else

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2
Q

describe CNS

A

central nervous system
info processing system centered in brain but involves all parts
brain processes and outputs

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3
Q

describe brain

A

biggest and most complex part of nervous system

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4
Q

what are the 2 components of peripheral system

A

input and output
brings info

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5
Q

describe input of pns

A

all sensory systems convey info about world into cns - from outside to inside
other sensory system = monitor inside of you - critical for internal milieu (homeostasis)

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6
Q

describe output of pns

A

enable you to act - cns connected to skeletal muscles = makes you have voluntary movements
autonomic nervous system = internal (makes intestines contract, etc), part of pns

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7
Q

how many neurons in nervous system

A

100 billion

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8
Q

what are neurons

A

electrical cells
Specialized
electrical properties = very diverse and at highest level

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9
Q

describe how neurons talk to each other

A

communication takes place at special sites called synapses

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10
Q

how many synapses in nervous system

A

hundred of trillions
creates neural network of vast complexity
approx 1000 synapses per neuron - many on all neurons

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11
Q

what is fastest that impulses can be sent

A

100 impulses/second = fastest that info moves around ~100m/s
carries out many functions at once

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12
Q

are neurons all the same shape and size

A

NOOOO
come in a large range of shapes and sizes
morphologically diverse

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13
Q

describe some neurons morphologically

A

perkinje = found in cerebellum, involved in coordination, leaves through axon
pyramidal = found in cerebral cortex (outer coating of brain, consciousness/perception)

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14
Q

what happens when neurons have more dendrites

A

more branches = more input synapses and places to communicate with other neurons

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15
Q

what characteristic structures do neurons share

A

cell body (soma)
branching dendrites
single axon (can be a few milimeters or more than a meter long)

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16
Q

describe polarization of neuron

A

in through dendrites - receive info from other neurons
goes out through axons towards presynaptic terminals
input and output generates impulse

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17
Q

describe soma of neurons

A

cell body
nucleus, DNA, ribosomes, protein synthesis
keeps cell alive
if crush cell body = dead

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18
Q

describe axon

A

can be long or short
enables communication
propagates info from one part to another - signals and many functions

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19
Q

describe flow of information through neuron

A

moves in certain direction
dendrites receive input from other axons
adds info together and makes decision if to send to another neuron
chain of info

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20
Q

describe resting membrane potential

A

inside typical neuron = -60 to -70 mV compared to outside
resting membrane potential caused by small excess of negatively charged ions inside cell

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21
Q

what is resting membrane potential used as

A

source of potential energy gradient to send info from one part to another

22
Q

what is voltage

A

measure of electrical potential energy
kinda like pressure

23
Q

describe electrical potential energy across neurons

A

neurons are surrounded by plasma membrane
electric potential energy differs across membrane - but its very small, 0.7 volts

24
Q

what are millivolts

A

1/1000 of a volt

25
Q

why is the inside of a neuron more negative compared to the outside

A

both the inside and outside have dissolved ions (like NaCl - dissociates)
tiny imbalance of negative charges inside so more negative on inside but not balanced by positive charges
can only be measure electrically - creates voltage gradient - essentially all cells have this

26
Q

what is resting membrane potential created by

A

concentration gradients for various physiological ions
selective permeability of the resting membrane to K+ ions

27
Q

how is concentration gradient for various physiological ions created

A

not spontaneous
gradients created by ATP
pumps Na+ out and K+ in

28
Q

describe concentrations of ions inside and outside cell - gen

A

Na+ high outside cell and low inside - wants to flow in
K+ low outside and high inside
Cl- high on outside and low inside
Anions (A-) high inside = lots of negatively charged atoms (amino acids) floating around

29
Q

describe concentrations of ions inside and outside cell - numbers

A

outside =
Na+ = 145mM
K+ = 5mM
Cl- = 100mM
A- = 50mM

inside =
Na+ = 10mM
K+ = 140 mM
Cl- = 5mM
A- = 145mM

positives and negatives on inside and outside equal each other, but inside has very little more negatives floating around

30
Q

describe selective permeability of the resting membrane to K+

A

when neuron at rest = skin on outside is almost completely impermeable to ions (like Na+) - sodium wants to flow in but cannot
also less permeable to Cl- and anions
BUT IS HIGHLY PERMEABLE TO K+ IONS

31
Q

describe why resting neuronal membrane is highly permeable to K+

A

a cell has a bunch of pores that are gated and only allow K+ through, they all open at same time and K+ flows out to outside of cell since low concentration of K+

32
Q

what happens when pores open in membrane (what happens to K+)

A

ions leak out of cell down concentration gradient
leaves behind negatively charged atoms and these cannot flow since membrane is impermeable to them

33
Q

do many K+ ions leak out of cell

A

NOOOO
outward movement of K+ stops rapidly and hardly any K+ will leak out before process stops

34
Q

why does barely any K+ leak out

A

the more K+ moves out it attracts negative ions
creates an electrical gradient that pulls K+ back into cell (opposite direction, since attracted to negatives inside cell)

35
Q

when do the gradients stop

A

when system is at equilibrium
concentration gradient (pushing out K+) = electrical gradient (pulling K+ back in)
rates will be equal

36
Q

the membrane potential at equilibrium can be describe by what

A

nernst equation
find when - specific concentrations

37
Q

describe nernst equation

A

measures voltage when electrical force is equal to concentration force
E(ion) = (2.3RT/zF) log (ion out/ion in)

R = gas constant
T = temp in kelvin
F = faradays constant
z = charge on ion
log of concentration on outside and inside

38
Q

what is main factor for determine the neuron resting membrane potential

A

equilibrium potential for K+ (Ek)
- 90mV
equilibrium state when inside of cell is -90mV compared to outside of cell

39
Q

describe ion channels

A

membrane protein with hole in centre
makes a pore/channel for ions
separate channels per ion
many are gated

40
Q

what is resting permeability to K+ caused by

A

leak chanells

41
Q

describe leak channels

A

proteins that form K+ selective pores through membrane
open at resting membrane potential
surface of neuron have many of these proteins
leak channels are leaky - even when membrane is resting K+ will still flow

42
Q

what would happen if the membrane of the resting neuron were exclusively permeable to K+

A

voltage difference across membrane would be Ek = -90mV
but irl its closer to -70mV

43
Q

what does each ion have

A

equilibrium potential

44
Q

what is equilibrium potential determined by

A

the ions charge
internal and external concentrations

45
Q

state equilibrium potentials for sodium, potassium and chlorine

A

Na+= +70mV
K+ = -90mV - has large influence since membrane is permeable to it
Cl-=-80mV

46
Q

why is resting membrane potential a bit more positive than equilibrium potential for K+

A

due to small inward leak of Na+
pushes membrane slightly towards Ena
Na+ leaks in and trys to get potential to +70mV - makes it a bit more positive but too much since membrane is more permeable to K+

47
Q

what is membrane potential determined by

A

concentration gradients and relative permeabilities of membrane to different physiological ions

48
Q

do concentration gradients change much

A

NOOOO

49
Q

do permeabilities change much

A

yes they can change rapidly and dramatically

50
Q

what makes greatest contribution to the membrane potential

A

dominant permeability
at rest = dominant permeability is to potassium and membrane potential close to Ek

51
Q

what is dominant permeability when neuron is at rest and active

A

rest = K+
active = Na+

PHGY 209 (19 decks)

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