nerve/synapse lectures 1-2

Question 1

what parts of nervous system are part of cns and pns

Answer 1

cns = brain and spinal cord
pns = everything else

Question 2

describe CNS

Answer 2

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

Question 3

describe brain

Answer 3

biggest and most complex part of nervous system

Question 4

what are the 2 components of peripheral system

Answer 4

input and output
brings info

Question 5

describe input of pns

Answer 5

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)

Question 6

describe output of pns

Answer 6

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

Question 7

how many neurons in nervous system

Answer 7

100 billion

Question 8

what are neurons

Answer 8

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

Question 9

describe how neurons talk to each other

Answer 9

communication takes place at special sites called synapses

Question 10

how many synapses in nervous system

Answer 10

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

Question 11

what is fastest that impulses can be sent

Answer 11

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

Question 12

are neurons all the same shape and size

Answer 12

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

Question 13

describe some neurons morphologically

Answer 13

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

Question 14

what happens when neurons have more dendrites

Answer 14

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

Question 15

what characteristic structures do neurons share

Answer 15

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

Question 16

describe polarization of neuron

Answer 16

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

Question 17

describe soma of neurons

Answer 17

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

Question 18

describe axon

Answer 18

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

Question 19

describe flow of information through neuron

Answer 19

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

Question 20

describe resting membrane potential

Answer 20

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

Question 21

what is resting membrane potential used as

Answer 21

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

Question 22

what is voltage

Answer 22

measure of electrical potential energy
kinda like pressure

Question 23

describe electrical potential energy across neurons

Answer 23

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

Question 24

what are millivolts

Answer 24

1/1000 of a volt

Question 25

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

Answer 25

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

Question 26

what is resting membrane potential created by

Answer 26

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

Question 27

how is concentration gradient for various physiological ions created

Answer 27

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

Question 28

describe concentrations of ions inside and outside cell - gen

Answer 28

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

Question 29

describe concentrations of ions inside and outside cell - numbers

Answer 29

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

Question 30

describe selective permeability of the resting membrane to K+

Answer 30

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

Question 31

describe why resting neuronal membrane is highly permeable to K+

Answer 31

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+

Question 32

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

Answer 32

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

Question 33

do many K+ ions leak out of cell

Answer 33

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

Question 34

why does barely any K+ leak out

Answer 34

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)

Question 35

when do the gradients stop

Answer 35

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

Question 36

the membrane potential at equilibrium can be describe by what

Answer 36

nernst equation find when - specific concentrations

Question 37

describe nernst equation

Answer 37

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

Question 38

what is main factor for determine the neuron resting membrane potential

Answer 38

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

Question 39

describe ion channels

Answer 39

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

Question 40

what is resting permeability to K+ caused by

Answer 40

leak chanells

Question 41

describe leak channels

Answer 41

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

Question 42

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

Answer 42

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

Question 43

what does each ion have

Answer 43

equilibrium potential

Question 44

what is equilibrium potential determined by

Answer 44

the ions charge internal and external concentrations

Question 45

state equilibrium potentials for sodium, potassium and chlorine

Answer 45

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

Question 46

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

Answer 46

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+

Question 47

what is membrane potential determined by

Answer 47

concentration gradients and relative permeabilities of membrane to different physiological ions

Question 48

do concentration gradients change much

Answer 48

NOOOO

Question 49

do permeabilities change much

Answer 49

yes they can change rapidly and dramatically

Question 50

what makes greatest contribution to the membrane potential

Answer 50

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

Question 51

what is dominant permeability when neuron is at rest and active

Answer 51

rest = K+ active = Na+