phospholipid

cholesterol

proteins: integral vs. peripheral

membrane fluidity

-weak intermolecular forces..

-presence of..

-type of..

-bilayer together

cholesterol

fatty acids of "tails"

at diff temps, non-adapted plasma membranes change fluidity

-Hi T:

-Lo T:

-Too fluid

-Too rigid

-degree of fatty acid (FA)

-Amt of

-Length of

Saturated FA's

-no..

unsaturated FA's

-one or more...

-ea. double bond ("point of unsaturation") creates a .. in the molecule

-the more unsaturated, the more double bonds, the .. in the molecule

-mono vs. poly

-"kink"

-more kinks

amount of membrane cholesterol:

-cholesterol acts to ..

-immobilizes 1st few hydrocarbon groups of phospholipid, making lipid bilayer ..

-warm-adapted membranes have .. of cholesterol

-stabilize (increase thermostability)

-less deformable

-higher proportions

FA chain length

-chain length prop. # .. between adjacent phospholipid molecules

-the more forces formed between adjacent phospholipids, the "tighter" the association between them --> more..

-intermolecular forces

-rigid bilayer

FA chain length

-the longer the FA chains in phospholipid "tails," the more .. are formed, the .. the bilayer

-the shorter the chains, the .. the bilayer

-forces, rigid

-less rigid

homeoviscous adaptation (summ)

-At hi T, problem: membranes ..

-Solution: make membranes..

-.. FA saturation

-..amt. cholesterol-..stability

-..FA chain length-..stability by .. # intermolecular forces betw. molecules

-too fluid

-more rigid

-increase

-increase, increase

-increase, increasing

homeoviscous adaptation

-at low T, problem: ..

-Solution: make membrane..

-..FA saturation

-..amt. cholesterol

-..FA chain length

-too rigid

-more fluid

-decrease

-decrease

-decrease

Plasma membranes are

-semi-..

-barriers to..

.. can pass easily

-permeable

-free diffusion

-small and uncharged and non-polar molecules

simple diffusion

-mov't of solute molecules from .. via random thermal motion ("down a [gradient]")

facilitated diffusion

-substances cross membrane .. thru protein channels (e.g. ions) or w/ assistance from carrier proteins e.g. glucose

active transport

-transport of substances by carrier proteins .. the [gradient] ("uphill")

-requires nrg=

-..(primary active transport), or

-..(secondary active transport)

-against

-ATP

-directly

-indirectly

Na+/K+ pumps function to

-regulate ..

-produce ..

-maintain ..

-drive ..

-cell volume

-heat

-membrane potential

-secondary active transport

Active Transport

-this pump contains binding sites for

-..

-..

-..

-Na

-K

-phosphate (P) from ATP

The Na+/K+ pump

-.. in the concentrations of Na+ & K+ inside and outside the cell

symporter

-both molecules move in .. direction

e.g. Na+/amino acid symporters in enterocytes

e.g. Na+/glucose symporters in enterocytes (=absorptive cells in small intestine)

antiporter

-the two molecules move in .. directions

-e.g. Na+/Ca +2 anitporters in .. cells

-E.g. Na+/H+ antiporters in ..

-opposite

-heart

-mammalian kidneys

ion transporters

-two types of ion channels

-..

-..

-leak channels

-gated channels

Membrane Potential (V_m)

-ions seperated by p.m. give rise to..

-seperation of charges across p.m. established by active pumps used to regulate..

-this electrochem potential diff is measured as..

-membrane potential

-[ion] of ICF different from ECF

-voltage

Ohm's Law

-Voltage (V)

-Current (I): flow of ions across p.m.

-Resistance (R): how "resistant" p.m. is to ion flow

Conductance (g)=..

-how "open" p.m. is to ion flow

-V=IR

-I/R, so V=I/g

membrane potential

-magnitude depends on:

-[gradients] betw. ..

-ion transport ..

-ICF and ECF

-capacities of p.m.

membrane potential

-ions move down [gradients] (chemical) if no..

-movement of charges establishes electric force that is..

-opposing forces exist

-electrochemical equilibrium

nernst equation

-expresses relationship between ..

-assumes p.m. permeable only to..

-membrane potential (Vm) and electrochem gradient for a specific ion

-this ion

membrane potentials that produce "electrical signals" via ion movement through membrane channels

-..

-..

-graded (local) potentials

-action potential

charge seperation-->..

-inside cell (inner membrane) more ( ) relative to outside

polarization

(-)

changes from Vr

depolarization

-p.m. becomes..

changes from Vr

repolarization

-p.m. goes from...

changes from Vr

hyperpolarization

-p.m. becomes

more (-) than Vr

= negative outshoot

Graded (local) potentials

-.. changes in Vm

- vary in magnitude & duration, which depend on ..

-local

-stimulus

AP's

-Always begin w/ .. --> Vm becomes less (-)

-All-..

-I..

-S..

-N..

-depolarization

--or-none

-irreversable

-self-propagating

-non-decremental

AP's Sequence of Events

1-6

1. opening of ligand-gated channels

2.If local (generator) potential rises to critical level= threshold, voltage-gated ion channels will open

3.Neurons begin to "fire" an AP

4.Vm reaches peak

5. Membrane repolarizes w/ rapid K efflux

6. Return to Vr

AP sequence of events

#1

opening of ligand-gated channels

-Na+ rushes into cell--> depolarization

-local potential: incoming Na+ diffuses for short distances along inside of p.m. of soma and produces current that travels from pt. of stimulus to trigger zone

-local potential= generator potential

AP Sequence of Events

#2

AP Sequence of Events

#3

Neuron begins to "fire" an AP

-Na+ gates open quickly

-Vm becomes more (+) due to Na influx

-Positive feedback--> rapid Na influx

AP Sequence of Events #4

Vm reaches peak

-polarity reverses as Vm passes 0 mV

-Na+ gates inactivated (close)

-Voltage-gated K+ channels ("K+ gates") fully open

AP Sequence of Events

#5

Membrane repolarizes w/ rapid K efflux

-K+ gates stay open longer than Na+ gates, so K+ efflux > Na+ influx --> Vm drops below Vr (=negative overshoot or hyperpolarization)

AP Sequence of Events

#6

Return to Vr

-all voltage-gated channels fully closed

-Na+/K+ pumps restore membrane back to it's resting potential

absolute refractory period

-no stimulus..

-spans from onset of..

-of any strength will produce a new AP

-AP to duration of Na+ gate inactivity (i.e. until membrane hyperpolarizes)

relative refractory period

-only an extra-strong stimulus will produce a new AP (in order to..)

-lasts until end of..

-override K+ efflux and depolarize cell enough to initiate new AP

-hyperpolarization

1. increase axon diameter

-lower resistance along longitudinal axis

2. increase insultation

-insulating the axon

allowing for saltatory conduction

electrical synapses

-adjacent cells joined by gap junctions through which ions can...

-allows for...

-diffuse directly from one cell to next

-rapid transmission of electrical impulses

1. an A.P. is propagated to the terminal of presyn. neuron

2. Ca 2+ enters synaptic knob

3. NT is released by exocytosis into the synaptic cleft

4. NT binds to receptor sites on postsyn neuron

5. specific ion channels open in the subsynaptic membrane

Excitatory Post-Synaptic Potentials

(EPSPs)

any voltage change that increases the likelihood that neuron generates an AP

-depol via Na+ influx

any voltage change that decreases the likelihood that neuron generates an AP

-hyperpol via opening of ligand-gated Cl- (and K+) channels

temporal summation

..

-if EPSP's add up to threshold -->..

-If IPSP's summate --> ..

single pre-synaptic neuron fires at high freq over relatively short period of time

-AP fired in post-syn neuron

-No AP

Spatial Summation

..

-If threshold reached-->..

-If potential moved away from threshold --> ..

Multiple stimuli from multiple pre-syn neurons--> collective effect

-AP fired

-No AP

-not summation of IPSP's

-one presyn neuron inhibits another

-used to reduce unwanted synaptic transmission (via decrease NT release)

2 nerves extending from CNS

-preganglionic

-postganglionic

cholinergic nerves release..

-bind to ..

Acetylcholin (ACh)

-nicotinic and muscarinic receptors

adrenergic nerves release..

-bind to ..

norephinephrine (NE)

-alpha- and beta-adrenergic receptors

Brain can distinguish stimulus intensity based on

-..

-..

-..

-# of neurons firing APs

-types of neurons firing APs

-frequency of APs

sensory adaptation

-receptor "adapts" to stimulus by..

-decline in afferent AP's firing despite

-reducing its response to it

-sustained stimulus strength on receptor

Tonic Receptors

-adapt slowly or not at all

-generate nerve impulses continually

stimulus transduction

-odorant binding --> activation of ..-->opening of Na+ channel --> Na+ influx--> ..

-secondary messenger sustem

receptor potential--> AP's down axon

Two major olfactory pathways

1. cerebral cortex, bypasses thalamus, conscious percept of smell

2. limbic system (behavioral rxns, also emotion and memory)