npb 110a - midterm 2

Ca2+ levels (inside and outside traits)

low cytoplasmic concentration and higher extracellular concentration

two classes of hormonal effects

organization and activational

organizational hormonal effects

impact the system early in development and usually have a permanent change

activational hormonal effects

trigger immediate behavior later in life after development that are usually reversible changes

describe the activational and organizational effects of testerone

organizational is impacting the early development of gonadal hormones from structural development that might not require continued hormone exposure to maintain sexual differentiation

what is the circuit system in which birdsong is produced in the brain

first auditory input goes to the motor pathway which consists of HVC then to RA and then to vocal organ of birds

HVC (high vocal center) importance for bird song

nucleus in brain that produces bird song and control song timing

RA (robust nucleus of arcopallium) importance for bird song (hint physical mech)

responsible for song motor behavior

when comparing make and females HVC and RA’s whcih one had the larger two and why

males because they’re they only one that sing

list the order of the sex hormone synthetic pathway

cholestrol produces testosterone which makes DHT and estradiol

androgens and impact on bird song

hormones that maintain male trait and affect song variability such as syllables and traits

what is estradiol/E2

active and potent form of estrogen

trill (bird song)

rapid repetition of a single note or syllabus in birds

what is another purpose of estradiol and describe the purpose

CAN REGULATE NEURONAL GROWTH, first estradiol enters the plasma membrane by itself bcs its a steroid and then forms pre-initiation complex which then acetylates histones and thus transcription finally proteins for neuronal growth

what is reproductive behavior in birds impacted by

season and they sing more in spring and early summer due to the increased sunlight

what are the activation effects of testosterone in birds (3)

bird song is seasonal, reproductive behavior is seasonal, and testis size varies based on the season so it changes color

describe the avian photoperiodic response for birds

first the light reaches the deep-brain photoreceptors since the skull is thinner than humans and then it makes TSH (thyroid stimulating hormone) and then it makes DIO3 which is an enzyme that then makes rT3 and T2 and rT3 is inactive and activates based on the season

describe the mammalian photoperiodic response

first light reaches the eye which then activates the SCN (circadian pacemaker) then melatonin is produced then TSH is made so then DIO2 can be made that then can make T3

what is the importance of thyroid hormones (T3 and T4)

regulators of metabolic rate and thermoregulation process and are important for normal growth and function of all body tissues

two main character traits of channels

permeable to certain ions and have high flux rate

what two forces are ions subjected to when channels open

chemical and electrical

chemical driving force

difussion due to thermal motion from high to low concentrations

five factors of fick’s law (laws of diffusion

concentration gradient, permeability of membrane, SA, MW of solute, and thickness of membrane

osmosis

water diffusing its concentration gradient

what happens when the membrane is permable to water but not solute

results in no net difusion of water when osmotic pressure appeares

osmotic pressure

pressure to stop inward flow of solvent across membrane and counteracts hydrostatic pressure

electric driving force

movement of charge particles along an electrical gradient due to electrostatic attraction/repulsion

restng membrane potential and formula

voltage difference across plasma membrane when cell is at rest (inside-outside voltage) and measured in millivolts

WHAT IS THE STANDARD RESTING MEMBRANE POTENTIAL and why

-70 mV due to more negative charges inside cell

how come standard resting membrane potential isn’t 0

since the remainder of the fluid is electrically normal but then charges at the membrane line up

does charge seperation across cellular membrane impact concentration gradients (y or no)

no

Na+/K+ATPase impact on establishing membrane potential (step 1) and describe how much sodium andp otasisum is tranproted and where

establishes unequal concentrations of sodium and potassium ions and uses ATP to pump 3 Na+ OUT of the cell and then 2 K+ into the cell

diffusion properties of Na+ and K+ and A- down their concentration gradient through leak channels (step 2) and describe permeabilities

Na+: extracellular permeability is much higher than intracellular making relative

K+: intracellular permeability is much higher than extracellular

A- (DNA/AA): intracellular permeability higher than extracellular so relative permeability is 0

what is equilibrium potential for ions

flow of a ion into or out of the cell is balanced

equilibrium potential (Vm) value for potassium

-90 mV

equilibrium potential (Vm) value for sodium

+60 mV

what equation describes equilibrium potential for a ion

Nernst equation

ion channels (two key traits)

permeable to certain ions and once open, ion move in response to electrical and chemical (diffusion) driving force

depolarization of cell

inside of cell BECOMES MORE POSITIVE so more positive charges flow inside

what is the purpose of the input zone (dendrites and cell body) in neurons

so that other neurons can give neurotransmitters that cause graded potentials (NO AP)

what is the purpose of axon hillock (trigger zone)

action potentials start from there

graded potentials defintion and chractertics

local changes in membrane potential that decay over short distances

what is the importance of the axon (conducting zone)

action potential runs down there

what is the purpose of the axon terminals (output zone)

release neurotransmitters to target neurons

four key steps on establishing membrane potential

1. Establishes and maintains concentration gradients for key ions (Na+, K+, A-) thru Na+/K+ ATPase (for those 2 ions)

2. Na+ and K+ diffuse down conc. gradient using leak channels

3. diffusion thru membrane results in charge separation. this creates a membrane potential; this voltage difference is an electrical gradient that exerts driving force on ion mvmt.

4. net mvmt. of charges continues until both forces (one exerted by electrical gradient and other from conc. gradient) balance one another

4 key properies of graded potentials

decay over short distances, decay over short times, scale with stimulus size, and get added together

A-

macromolecular anions w/ high intracellular conc. of nucleic acids and proteins that carry a negative charge

Concentration of Na+ (specfic values)

extracellular: 150

intracellular: 15

relative permeability: 1

Concentration of K+ (specific values)

extracellular: 5

intracellular: 150

relative permeability: 50-75

What membrane proteins underlie resting potential?

leak channels and Na+/K+ ATPase

hyperpolarization of cell

internal becomes more positive so then more negative ions flow in and more positive ions flow out

temporal summation of graded potentials

neuron receives rapid information from another synapse

spatial summation of graded potentials

neurons receives inputs from multiple other neurons

Why does Vm equal to -70 mV?

a large net diffusion of K+ outward drives this to a large negative potential and relatively small net diffusion of Na+ inward neutralizes some of the potential created by K+

what does summation do to graded potentials

adds up all positive and negative charges

why were squid giant axon important for actions potentials

help discover the ionic basis of action potentials

action potential

brief all-or-nothing reversal in membrane potential ("spike") that lasts ~1 millisecond that is brought by about by rapid changes in membrane permeability to Na+ and K+ ions

threshold for AP defintion and what happens afterwards and describe the positive feedback loo[

the level of stimulation required to trigger action potential and once it's crossed then depolarization occurs through positive feedback loop (depolarization leads opening of voltage gated sodium channels so then even more sodium flows in after the initial amount)

what does the action potential rely on (two things)

the voltage-gated K+ channel and the voltage gated Na+ channel

rising phase of action potential

Na+ activation gate opens ! and Na+ rushes in so membrane gets depolarized

falling phase of action potential (hypeprolatizaiton after hyper)

K+ channel opens! (Na+ inactivation gate closes so no more Na+ in ) and K+ out. then at hyperpolarization, Na+ inactivation gate opens, Na+ activation gate closes and then after hyp., K+ closes

what are the gates doing at resting potential?

both closed at -70mV

voltage-gated Na+ channel traits and then the three states it can be in a AP

open quickly in response to depolarization which allows Na+ to flow down its electrochemical gradient

3 states:

1. inactivated: closed and NOT capable of opening; can only be removed by depolarization to -70 mV

2. activated: open

3. deactivated: closed but capable of opening

voltage-gated K+ channel traits and the two states it can be in a AP

opens more slowly in response to depolarization which allows K+ ions to flow out of cell down electrochemical gradient. two states are deactivated and activated

absolute refractory period

brief period when a second spike CANNOT be generated. it begins with activation of voltage-gated Na+ changes and ends when inactivation is removed

relative refractory period

brief period following a spike during which a HIGHER intensity stimulus is NEEDED to generate a second spike. it begins with Na+ channel inactivation being removed and ends when voltage-gated K+ channels deactivate (CAN generate another if membrane reaches above threshold and helps move AP in one direction)

synapses

junctions between two neurons to electrically communicate with each other

two types of synapses

electrical and chemical

chemical synapse (5 steps)

1. action potential reaches the presynaptic neuron from axon terminal

2. Ca2+ influx into the presynaptic terminal due to the opening of voltage-gated calcium channels

3. release of neurotransmitter by exocytosis via vesicles into the synaptic cleft (gap btwn neurons)

4. receptor binding onto the postsynaptic cell’s receptor

5. opening of specific ion channels in the sub synaptic membrane (receiving target cell) to change its voltage and get the message across

at rest is the voltage-gated Ca2+ channel closed or opened

closed at rest

is a neurotransmitter receptor a ligand or chemically locked

ligand

what are postsynaptic potentials (PSP)

temporary changes in the charge of a neuron’s membrane that occur when neurotransmitters bind to its receptors ALSO is a graded potential

What ion flux in the presynaptic neuron drives neurotransmitter release by letting vesicles of neurotransmitter fuse with the membrane

Ca2+

inhibitory postsynaptic potential (IPSP) (also a type of graded potential)

HYPERPOLARIZING events that bring the membrane potential away from threshold TO MAKE IT LESS LIKELY TO FIRE AN AP

what is the ion selectivity of ipsp’s and why those ions

Cl- and K+ are selected for since Cl- will make internal more negative and K+ because it likes to exit the intracellular part

excitatory postsynaptic potential (EPSP) (also a graded potential)

DEPOLARIZING events that bring resting membrane potential closer to threshold SO MORE LIKELY TO FIRE AP

what is the ion selectivity of epsp’s

Na+ and Ca2+ because Na+ will enter the cell to make it more positive and then Ca2+ will also enter to make it more positive

common inhibitory neurotransmitters (2 types, hint double g)

GABA and glycine (Gly)

common excitatory neurotransmitters (2 types)

glutamate (Glu) and acetylcholine (Ach)

two classes of neuotransmitter receptors

ionotropic and metabotropic

ionotropic receptor properties

FAST synapses and ligand-gated ion channels

gap junctions

directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells

metabotropic

slow synapses and GPCR’s so coupled to G proteins

purpose of acetylcholine esterase

breaks down acetylcholine

what three mechanisms limit the duration of neurotransmitters (can cause it to stop)

dilution, degradation, and reuptake into the presynaptic terminal by transporter proteins or into glial cells

do neutrotransmitter receptors have a low or high affinity for neurotransmitters

low

How are destinations identified?

by specific amino acids sequence (signal sequences/peptides)

Where does protein sorting start?

in cytosol, n-terminal signal sequence sends protein to the ER

cotranslational translocation

translocation and translation occur simultaneously

when a SRP binds can translation occur yes or no

no

exocytosis defintion and purpose and examples

contents of a cell vesicle are released to the exterior of cell and a form of active transport, can be used to get rid of waste and to insert membrane proteins into the cell membrane

to enter translocon, proteins must be....

UNfolded

endocytosis

active transport where a cell engulfs a protein and transport contents into the cell

three types of endocytosis

pinocytosis, phagocytosis, and receptor mediated endocytosis

pinocytosis (selective or not)

cell drinking and non selective

phagocytosis (selective or not)

cell eating and selective

receptor mediated endocytosis and describe with coat protiein is being used

uses receptors that then communicate with the clathrin (coat proteins) in order to dictate if the contents will be taken into the cell