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Physiology Test 1
N/A
131
Physiology
Graduate
02/01/2011

Additional Physiology Flashcards

 


 

Cards

Term
What is the relationship between movement, driving force, and resistance?
Definition

Movement = Driving force/resistance

 

"Movement is directly proportional to driving force and inversely proportional to resistance."

Term
3 types of solute transport
Definition

1. passive/non-carrier mediated - simple diffusion through lipid bilayer, through pores, through gated channels

2. passive/carrier mediated - facilitated diffusion

3. active - primary (ATP hydrolysis, energy release from redox reactions) and secodary (coupled transport, co-transport, exchangers)

Term
Water is transported via
Definition
osmosis
Term
Describe the general structure of biological membranes. Include the phospholipid strucutre, the function and importance of cholesterol in membranes and the terms bilayer, monolayer, hydrophobic, hydrophilic, and amphipathic
Definition
Biological membranes are usually a lipid bilaryer with a hydrophilic phosphate head and a hydrophobic lipid tail, which makes it amphipathic. The phosphate oreints itself outward and interacts with the extracellular space which is mostly water. The lipid chains interact with each other on the inside of the membrane, creating a hydrophobic reigion. cholesterol binds to the hydrophobic region and allows it to be liquefied. without cholesterol, this fatty region is solid and would prohibit diffusion across the membrane. Another biological membrane is composed of a phospholipid monolayer, called a micelle and is formed by the phospholipids creating a sphere with the hydrophilic heads pointing out and the tails pointing in.
Term
Describe what substances can pass directly through the lipid bilayer
Definition
Substances that can pass through the bilayer must be uncharged and hydrophobic. These include respiratory gasses, steroid hormones, and anesthetics. THings that cannot pass directly through include ions and proteins that are too big.
Term
Describe the various functions of proteins associated wtih biological membranes (3)
Definition

Pores - proteins located in membranes that are always open. flux through pores depends on concentration gradient and permeability (size and # of pores/unit surface area)

 

Gated channels - pores with a gate. if it's closed, nothing goes through. if it's open, it acts like a pore

 

Carriers - protein that undergoes conformational change when selected molecule binds and dissociates

Term
What organelle contains the cell's genetic material, is where DNA replication takes place, controls cellular functions, transcription takes place here as wel
Definition
nucleus
Term
what organelle produces ATP via the Kreb's cycle?
Definition
mitochondria
Term
What organelle synthesizes lipids and steroids, metabolizes carbohydrates, regulates calcium concentraiton, drug detox, attachment of receptors on cell membrane proteins, and steroid metabolism
Definition
smooth ER
Term
What organelle contains binding sites for ribosomes that are making proteins for the secretory pathway?
Definition
rough ER
Term
What organelle translates mRNA into protein, contains a small and large subunit
Definition
ribosome
Term
what organelle modifies, sorts, and packages macromolecules for cell secretion (exocytosis) or for use within the cell.
Definition
golgi apparatus
Term
what organelle has an enzyme that binds to a peptidoglycan molecule and breaks glycosidic bonds
Definition
lysosomes
Term
What equation describes simple diffusion of a molecule across a cell membrane?
Definition
deltaG = RTln(Xi/Xo)
Term
HOw is passive transport through pores different than that through channels?
Definition
through pores can happen anytime, channels have to be open
Term
IF the electrochemical gradient is postive, then net movement is into/out of the cell? If it is negative?
Definition
Positive = out, Negative = in
Term
Define primary active transport. Identify and briefly describe the two sources of energy used to drive primary active transport.
Definition

Primary active transport: solute movemnt against an electrochemical gradient. Carrier-mediated, requires enerrgy that can be provided by:

 

ATP hydrolysis (Na/K pump)

Direct link to a primary metabolic reaction (redox rxn that occurs in intermitochondrial membrane of electron transport chain)

Term
How does the Na/K ATPase move ions (ratio, what's in/out?)
Definition

3 Na+ out

2 K+ in

Term
How does the Na/K ATPase work?
Definition

The pump binds ATP and 3 intracellular Na ions.

ATP is hydroluzed, which phosphorylates the pump and releases ADP

A conformaitonal change of the pump exposes Na to the outside. The pump also now has a low affinity for Na, so it releases it.

The pump now has a high affinity for K, so it binds 2 extracellular K, which causes dephosphorylation of the pump, reverting it to it's original conformation and exposing the K (which the pump now has a low affinity for) to the inside of the cell

K is released, ATP binds, and the process starts over

Term
___ is an ion pump that catalyzes auto phosphorylation. Ex: Na/K ATPase
Definition
P-Type ATPase
Term
____ acidifies a wide array of intracellular organelles and pumps protons across the plasma membranes of various cell types. They couple the energy of ATP hydrolysis to proton transport across intracellular and plasma membranes of eurkaryotic cells
Definition
V-type ATPase
Term
Describe how the F-type ATPase establishes a driving force responsible for operating the ATPase
Definition
energy is captured by 3 H+ pumps and that drives the H+ out of the mitochondrial matrix and into the intermembrane space. the result is a large concentration gradient across the intermitochondrial space and that gradient drives the ATPase, which synthesizes ATP
Term
2 domains of F-type ATPase
Definition

F0 - domain which is integral in the membrane

F1 - peripheral

Term
Briefly describe secondary active transport
Definition
transport of 2 or more solutes that are coupled. one of the solutes (usually Na+) is transported down its gradient and provides potential energy for the transport of the other solute against its gradient (kinetic energy).
Term
2 types of secondary active transport
Definition

Co-Transport/symport: If solute moves in teh same direction across the cell membrane

ex: Na+, glucose cotransport in small intestine

 

Exchange/antiport: if solute moves in the opposite direction across cell membrane (Ca2+/Na+ exchange)

Term
What is an example of "tight" epithelium? What is an example of "leaky" epithelium?
Definition

tight: distal convoluted tubule and collecting duct of kidney

 

leaky: proximal tubule of kidney

Term
What are the excitable tissues of the body? What's the diff between excitability and conductivity?
Definition

nerve and muscle

 

excitability is the ability of cells to respond to stimuli by a change in membrane potential or generation of action potential

 

conductivity is a property of a cell which enables the effect of a stimulus to be transferred from one part of a neuron to another, an excitation of one part of a neuron is conducted to all other parts

Term
___ are signaling molecules that are involved in regulation.
___ is a process by which a chemical messenger binds to a receptor and brings about a response in the target cell.
___ is regulation from inside the cell
___ is regulation from outside the cell
Definition

chemical messengers

signal transduction

intrinsic regulation

extrinsic regulation

Term
Differentiate between direct and indirect intercellular communication
Definition

Direct: the ions and small molecules pass directly through connexons (gap junctions) from the cytoplasm of one cell to the cytoplasm of another (cardiac muscle). The tissue functions as a single unit. Much faster.

 

Indirect: a ligand secreted from one cell binds to a receptor on itself or another cell

Term
4 functional classifications of chemical messengers
Definition

paracrine - messenger secreted into ECF and diffuses and binds to a receptor on a neighboring cell

Autocrine - messenger secreted into ECF and binds to a receptor on itself

Neurotransmitter - also paracrine, are secreted from neurons, cross the synaptic cleft and bind to a receptor on the postsynaptic cell

Hormones - are secreted into the blood and transport to the target cell where they bind to a receptor

Term
ID the five structural classifications of chemical messengers and describe their chemical structure
Definition

amino acids - amine group, carboxyl grou, R groups

Amines

Steroids - 3 six-carbon rings bound to a 5-carbond ring

proteins

eicosanoids

Term
ID the 4 amino acid messengers and whether they are excitatory or inhibitory
Definition

glutamate - excitatory

aspartate - excitatory

glycine - inhibitory

GABA - inhibitory

Term
Identify the amine messengers
Definition

Catecholamines (derived from tyrosine):

epinephrine (from adrenal medulla) and norepinephrine (CNS and PNS neurotransmitter AND hormone - from adrenal medulla)

 

Dopamine - CNS neurotransmitter

 

Thyroid hormones (T3 & T4)

 

Serotonin - CNS neurotransmitter from tryptophan

Histamine - paracrine derived from histadine

Term
Identify the 5 steroid messenger families and the most prominent member of each
Definition

Glucocorticoids - cortisol

Mineralcorticoids - aldosterone

adrogens - testosterone

estrogens - estradiol

progestins - progesterones

Term
___ are polypeptides that serve a function in the body. They are the largest number of chemical messengers. ___ include a variety of paracrines that are produced by virtually all cells in the body.
Definition
Proteins, eicosanoids
Term
4 properties of messengers
Definition

Receptors show specificity for the messenger

Receptor-messenger binding is brief and reversible

A single messenger can bind to more than one receptor

A target cell may have receptors for more than one type of messenger

Term
3 factors that mitigate the magnitude of the target cell response to a signaling molecule
Definition

messenger concentration

number of receptors on target cell

affinity of receptor for messenger (strength of binding)

Term
Receptor agonists v. antagonists.
Definition

agonists: are exogenous compounds that bind to a receptor and cause normal biological function

Anatgonists: exogenous compounds that bind to a receptor and block its function

Term
Differentiate between lipophilic and lipophobic messengers and give examples of each
Definition

lipophilic - can cross lipid bilayer and bind to intracellular receptors

steroid hormones bind to receptors in cytoplasm

thyroid hormones bind to receptors in nucleus

 

lipophobic - cannot cross lipid bilayer and thus bind to membrane receptors

proteins - amino acids - amines (except for thyroid hormones)

Term
Describe the mechanism of action for chemical messengers binding to intracellular receptors
Definition

hormone binds to receptor

receptor-hormone complex bind to DNA a beginning of specific gene. 

Hormone acts as transcription factor to cause gene exporession and results in protein synthesis

new protein regulates cell activity

Term
Describe the mechanism of action for fast ligated gated channel linked receptors
Definition
receptor and channel are the same protein (nicotinic receptor) - when the messenger binds, the channel opens and lets the messenger through
Term
What is a nicotinic receptor?
Definition
the protine actions and both the receptor and the ion channel
Term
How does the G protein-linked receptor work for adenylate cyclase?
Definition

ligand binds

alpha subunit of the g-protein dissociates and binds to adenylate cyclase

ATP is converted to cAMP

cAMP activates protein kinase A, which phosphorylates a protein to cause a response in the cell

Term
___ is addition of a phosphate. ___ is removing a phosphate
Definition
phosphorylation, hydrolyzation
Term
3 subunits of g protein
Definition

alpha

beta

gamma

 

beta and gamma act as a dimer

Term
What is up-regulation?
Definition
more of the signal is produced and less of it is cleared from the cell. results in more response from the cell
Term
How does coffee work, and what does that have to do with G-proteins?
Definition

epinephrine works on a g-protein system.

phosphodiesterase convers cAMP to AMP to end the cycle and the action of the kinase.

Coffee inhibits phosphodiesterase and thus allows the action of epinephrine to keep working without being cleared from the cell.

Term
Mechanism of action of the phospholipase c g-protein system
Definition

ligand binds, alpha subunit dissociates and activates phospholipase C

PIP2 is convered to IP3 on DAG

IP3 opens ER Ca2+ channels to allow Ca2+ out of ER

CA2+ binds to calmoduline, which activates protein kinase, which phosphorylates the protein, which causes a response in the cell

Term
what do protein kinases do?
Definition
phosphorylate proteins
Term
How do enzyme-linked receptors work?
Definition

receptor is also enzyme

 

ligand binds to receptor , causing conformational change

conformational change activates tyrosine kinase

tyrosine kinase activates intracellular protein

phosphorylated protein brings about target cell response

Term
3 types of membrane receptors
Definition

Channel-linked

enzyme-linked

g-protein

 

Term
Describe the concept of signal amplification
Definition

one messenger binds to one receptor. several G proteins are activated. Each G protein activates an adenylate cyclase. Each adenylate cyclase generates hundreds of cAMPs. each cAMP activats a protein kinase A. each protein kinase A phosphorylates hundreds of proteins.

 

Amplification occurs at adenylate cyclase and protein kinase A

Term
Differentiate between endocrine and nervous system regulation
Definition

endocrine - releases hormones into the blood to be transported throughout the body

nervous system - transmit electrical signals along the axon which triggers a chemical signal across a synapse

Term
primary and secondary endocrine organs
Definition

primary: major fxn is to secrete hormones.

hypothalamus, pituitary, pineal gland, thyroid, parathyroid, thymus, adrenal gland, pancreas, gonads

 

secondary: has another major fxn but also secretes hormones.

heart, liver, stomach, small intestine, kidney, skin

Term
Describe the hypothalamus-posterior pituitary axis
Definition

the hypothalamus synthesizes and releases oxytocin and ADH in secretory vesicles which are transported to neural endings in the posterior pituitary. the posterior pituitary releases the oxytocin and ADH after receiving a signla from another neuron. They are then released through exocytosis.

 

ADH = vasopressin = antidiuretic hormone.

Term
Describe the hypothalamus-anterior pituitary axis.
Definition

The hypothalamus produces hormones that are transported through the H-P portal system to the anterior pituitary.

These hormones signal the anterior pituitary to release other hormones that it has synthesized.

Term
Name the anterior pituitary hormone that is secreted in response to each hypothalamus hormone.

Hypothalamus:
Prolactin releasing hormone
prolactine inhibiting hormone
thyrotropin relaseing hormone
cortiocotropin releasing hormone
growth hormone releasing hormone
growth hormone inhibiting hormone
gonadotropin releasing hormone
Definition

prolactin

prolactin

thryoid stimulating hormone

adrenocorticotropic hormone

growth hormone

growth hormone

follicle stimulating hormone and luteinizing hormone

Term
Describe the hypothalamus-pituitary axis. Identify all hormones and target organs involved in each axis.
Definition

Thyroid axis - thyroid releasing hormone secreted from hypothalamus. causes ant pituitary to release thyroid stimulating hormone. acts on thyroid gland and releases thyroid hormone.

 

Adrenal Axis - corticotropin releasing hormone secreted from hypothalamus. causes anterior pituitary to release adrenocorticotropin hormone. acts on the adrenal cortex and releases cortisol.

 

Liver axis - growth hormone releasing hormone and growht hormone inhibiting hormone are released from hypothalamus. causes ant pituitary to release growth hormone. acts on liver and releases insulin like growth factors.

 

Gonad axis - gonadotropin releasing hormone released from hypothalamus. causes ant pituitary to relase leutenizing hormone and follicle stimulating hormone. acts on the gonads - males release androgens, females release estrogens and progesterone

Term
Describe how secretion of blood hormones is controlled.
Definition
negative feedback - if blood level is low, hormones are released more. if blood levels are low, then less hormones are released.
Term
How is carrier protein binding of blood hormones controlled?
Definition
lipophilic hormones must be bound. the concentration of unbound hormones is the active pool
Term
How is clearance rate and release rate of blood hormones controlled?
Definition
hormones are degraded by enzymes when the signal is removed. the process is quick for lipophobic hormones and slow for lipophilic hormones
Term
Identify, describe, and give examples of each of the 4 types of hormone interactions.
Definition

antagonistic - 2 hormones that have opposite effects. parathyroid hormone increases blood calcium levels and calcitonin decreases them.

 

additive - 2 hormones have the same effect and the net effect equals the sum of the individual effects.

 

synergistic - 2 hormones have the same effect and the net effect is greater than the individual effects.

 

permissive - one hormone is needed for another hormone to exert its actions. such as when epinephrine caues bronchodilation.

Term
____ describes the electrical charge of an ion and the electrostatic force between 2 ions. What is the equation?
Definition

coloumb's law

 

F=K(qa.qb/r^2)

F= force between two particles

qa = charge of particle a

qb = charge of particle b

r = separation between particles

K = constant

Term
___ describes flow of electric charge (current). What is the equation?
Definition

Ohm's Law

 

I=V/R

I = currrent

V = voltage

R = Resistance

Term
___ is the rate of flux of charge particles from one area to another.
___ is the charge difference between 2 areas. It is the driving force for charge flow.
___ is anything that slows current flow.
Definition

current

voltage

resistance

 

To increase current, you must either increase voltage or decrease resistance

Term
Describe positive and negative current flow as it relates to a cell membrane
Definition

current flow for cations will be:

negative when membrane pot is below equilibrium potential

positive when membrane pot is above equilibrium pot

Term
3 factors that affect resting membrane potential
Definition

1. Gibbs-Donnan potential - determined by fixed, negative charges (proteins, AMP/ADP/ATP)

2. Net Diffusion potential (Ediff) - MOST SIGNIFICANT

3. Electromagnetic ion pump potential (Ep) - LEAST SIGNIFICANT

 

Term
Describe the various funcitons of K+ voltage-gated channels and the channel type that is utilized to accomplish each fxn.
Definition

Delayed outward rectifying: repolarize membrane. Slow to open and close.

 

Transient outward rectifying: early repolarization in myocyte APs. Open and close quickly

 

Inward rectifying: stabilize Vm. Allow one-way movement of K+ into cell to oppose the electrochemical gradeitn diffusion of K+ out of cell.

Term
Describe the current/voltage relationship of inward rectifying K+ channels. Identify the mechanism of action.
Definition

function to stabilize resting membrane potential at Vm=-90. Allows K+ to flow in to counterbalance other channels' outward flow. 

 

Mg2+ ions block K+ from flowing out of cell through these channels, but allows K+ to flow in.

Term
Describe the neuronal AP
Definition

RMP

Stimulus - if threshold, voltage-gated Na+ channels open and depolarize membrane

Kv1.1 channels (delayed outward rectifying) and repolarize membrane

K+ close slowly, resulting in hyperpolarization of membrane

Term
Describe the activation and inactivation of voltage-gated Na+ channels. How do delayed rectifier K+ channels differ from Na+ channels in this regard?
Definition

Na+ channels have an activation gate and an inactivation gate. When at RMP, the activation gate is closed and inactivation gate is open. When threshold is reach, the activation gate opens, allowing for inward flow of Na_. Almost simulataneously,, the inactivation gates reset to their original orientations (absolute refractory period).

 

K+ channels only have an activation gate, which is either open or closed.

Term
Describe the skeletal muscle AP
Definition

RMP = -90mV

Threshold = -70mV

Depolarization - carried by Na+ current (INa channels)

Repolarization - K+ current as a result of opening of Kv1.1 voltage-gated channels

 

takes about 15-20 msec

Term
Describe the cardiac myocyte AP, include all 5 phases and the current associated with each phase
Definition

Phase 4 - RMP. Kept at -90mV by inward rectifying voltage-gated K+ channels (Kir), which stabilize the membrane by providing an inward rectifying flow of K+ (IKir) to counterbalance outward flow of K+ due to electrochemical gradient.

 

Phase 0 - upstroke (depolarization) carried by Na+ current (INa)

 

Phase 1 - early repolarization. results from a transient outward K+ current (Ito) through A-type rectifying channels (Kv1.4) which open as the membrane potential becomes more positive due to inactivation Na_ channels and close shortly thereafter.

 

Phase 2 - plateau. results from balance between inward Ca2+ and outward K+ current. Ca 2+ is carried through long-lasting L-type voltage-gaed channels that open slowly at about -40mV during Phase 0. K+ current is the result of the dying out of Ito and the opening of delayed rectifying K+ channels Kv1.1.

 

Phase 3 - Final repolarization. Carried by K+ through Kv1.1 channels as Ca2+ channels close, resulting in a strong outward IKv1.1.

Term
Describe the cardiac automatic cell AP. Include all 3 phases and the currents with each phase.
Definition

Phase 4 - Slow diastolic depolarization. AKA Pacemaker potential. Happens spontaneously. Made up of 3 currents:

- Funny current (If) - carried by Na+ through nucleotide channels which open when the membrane potential drops below -50mV during repolarization. This is predominating current.

- Transient Ca2+ current (ICaT) - carried through T-type Ca2+ channels, which open when Vm reaches -55mV during depolarization.

- Delayed rectifier K+ current (Kv1.1) - outward current that opposes the two inward currents.

 

Phase 0 - upstroke (depolarization). After threshold is reached, carried by Ca2+ L-type channels (ICaL)

 

Phase 3 - Repolarization. Carried by K+ delayed rectifier current (IKv1.1)

Term
Describe smooth muscle AP
Definition

Depolarization: Ca2+ channels open.

Repolarization: IKv1.1

 

Smooth muscle doesn't have Na+ channels so it uses Ca2+ channels and therefore it happens more slowly

Term
Differentiate between absolute and relative refractory periods
Definition

Absolute: time during which a second AP cannot occur at the location of the first on eunder any circumstances due to Na+ channel inactivation.

 

Relative: Period during which a second AP can occurs but it requires a much stronger than usual stimulus. Due to Kv1.1 channels being open, whcih tends to hyperpolarize the membrane, so it requires a lot of Na+ to counteract the hyperpolarization. Begins about when the membrane reaches threshold during repolarization.

Term
Describe cross-bridge cycling
Definition

G-Actin monomers combine into an F-actin filament. Each G-Actin has a myosin binding site.

 

In the resting state, the myosin head is at a 90 deg angle to the actin, but it is not bound. the mysoin head has ADP and Pi bound. Tropomyosin is blocking the myosin binding sites on actin.

Ca2+ binds to troponin, which causes a conformational change, which pulls tropomyosin off of actin and epxoses the myosin binding sites. the myosin head binds to the actin. still at 90 deg angle.

The ADP and Pi are released, causing the powerstroke where the myosin head contracts to a 45 deg angle and moves the actin filament, shortening the sarcomere.

ATP binds to myosin head, myosin releases from actin.

ATP is hydrolyzed and myosin head resets to 90 deg angle.

Term
What is excitation-contraction (EC) coupling?
Definition

The sequence of events that links the AP to contraction (and to the cross-bridge cycle).

 

During an AP, Ca2+ is released from the sarcoplasmic reticulum into the cytoplasm where it can bind to troponin and pull tropomyosin off actin to allow myosin to bind.

Term
How is muscle contraction (and the cross-bridge cycle) terminated?
Definition
Sarcoplasmic reticulum removes Ca2+ from the cytoplasm via Ca2+ pumps on the SR membrane.
Term
Describe the mechanism of EC coupling for skeletal and cardiac muscle.
Definition

Skeletal: mechanical coupling. channels connected to the T-tubules. membrane depolarization opens the L-type Ca2+ channel and causes the Ca release channel to open.

 

Cardiac: Ca induced Ca release (CICR) - Ca enters the cell via L-type Ca channels, whcih activates the Ca release channels. No physical connection between T tubule and channel

 

Term
Isometric v. isotonic
Definition

isometric - if a muscle is anchored at both ends and stimulated it will generate force without chanign length (force is less than load) - like trying to push the wall back

 

isotonic - if a muscle is anchored at one end and a weight is attached to the other, muscle stimulation results in force generation and muscle shortening (force is greater than load) - like lifting a marker

Term
3 phases of an isometric twitch and factors contributing to each
Definition

latent period - events of EC coupling to the point of Ca release from SR

 

contraction phase - ca binds to troponin and cross-bridge cycling rate is increasing. (upstroke)

 

relaxation phase - ca is being pumped back into SR and CB cycling rate is decreasing

Term
Describe effects of increasing stimulus intensity on isometric force development in skeletal muscle.
Definition

summation - with each successive stimulus, more ca is released and the muscle contracts more than it would have because it has not fully relaxed by the time the next stimulus comes.

 

tetanus - myosin binding sites are saturated and muscle does not have time to relax between stimuli so it remains at full contraction.

Term
Describe the conduction of current (depolarization) through the cytoplasm of a neuron
Definition
the ability of the cytoplasm to transmit current is referred to as the cell's cable properties. once the current is presented to the cell body via axon, the charges will flow from initial area and diffuse across the cytoplasm, depolarizing adjacent areas. if the stimulus is strong enough to depolarize the axon hillock to threshold, an AP will occur.
Term
Describe the relationship of the membrane and cytoplamsic resistance to conduction of depolariztaion and how they relate to the length constant for a neuron.
Definition

Length constant decreases with increased cytoplasmic resistance (indirectly porportional)

 

Length constant increases with increase in membrane resistance (directly proportional). the more impermeable the membrane is to chare, the greater resistance it has.

Term
differentiate between an electrical and chemical synpase.
Definition

electrical: plasma membranes of adjacent cells are linked together by gap junctions such that when an electrical signal is generated in one cells, it is directly trasnfered to the adjacent cell. Fast communication.

 

Chemical: one neuron secretes a neurotransmitter into the ECF in response to an AP arriving at its axon terminal. the neurotransmitter then binds to receptors on the plasma membrane of a second cell, triggering an electrical signal that may or may not initiate an AP.

Term
3 functional components of chemical synapses
Definition

presynaptic neuron

postsynaptic neuron

synaptic cleft

Term
Describe current flow through an electrical synapse
Definition

current flow via gap junctions. gap junctions are areas of the membrane containing connexon proteins that form channels linking the cytoplasm of two adjacent cells

 

signal jumps at nodes of ranvier

Term
Definition of length constant
Definition
distance over which depolarization decrease to 37% of its maximal value
Term
saltatory conduction
Definition
electrical conduction of signals - myelinated areas conduct a signal. nodes of ranvier allow signal to leave and new signal to enter
Term
Describe the concept of an equilibrium potential. What equation do you use to calculate it?
Definition

Equilibrium potential = the point at which the electrical gradient and chemical gradients for a specific ion are equal and the net movement is zero.

Calculated with Nernst Equaiton:

Ex= (-RT/zF)ln(Xi/Xo)

Term
How does water transport across a lipid bilayer? And what are the two types of water channels?
Definition

Water can cross a lipid bilayer but only does so very slowly. For water to cross easily, it needs a pore that it can go through called an aquaporin.

 

2 types of aquaporins:

AQP1: are always present in a cell membrane. used for high volume water transport, such as in RBCs and renal proximal convoluted tubules.

AQP2: are inserted by hormonal control as needed. For instance Antidiuretic hormone inserts these aquaporins regularly. Lasix facilitate the function of AQP2 in CHF pts. When someone is on lasix and lots of AQP2 are functioning, they have to pee a lot.

Term
Describe Gibbs-Donnan equilibrium and the relationship between it and osmotic work
Definition

Gibbs-Donnan Equilibrium: fixed negative charges in cytoplasm lead to ionic movement across membranes. Results in chemical, electrical, and osmotic equilibrium.

 

Osmotic work is done to counteract the excess pressure of H2O entering a cell from Donnan forces. It is accomplished by active transport of Na/K ATPase which keeps an equal number of neg and pos ions on either side of the membrane and thus keeps excess water from entering the cell to equalize the solute concentration inside the cell, which would lyse the cell.

 

 

Term
How does Ouabain work?
Definition
it blocks the Na/K ATPase and thus causes the cell to lyse due to excess water entering the cell due to lack of osmotic work
Term
____ is the total number of osmotically active solutes in a single solution.
Definition
Osmolality
Term
What two layers do epithelial cells generally separate in the body? What are the two membranes associated with epithelial cells?
Definition

Epithelial cells separate interstitial fluid from lumen

 

2 membranes:

1. Apical, AKA:

a. brush border

b. mucosal membrane

c. luminal membrane

Faces toward lumen

2. basolateral membrane. AKA serosal or peritubular membrane. Faces toward interstitium

Term
Transcellular v. paracellular epithelial transport
Definition

Transcellular: substances cross the cell by sequentially passing through the apical and basolateral membranes

 

Paracellular: substaces bypass the cell and cross throguh tight junctions

Term
2 types of channel-linked receptors
Definition

fast and slow

 

Fast - receptor and channel are the same protein

Slow - receptor and channel are different proteins coupled by a G protein

Term
What are the electrical consequences of a Donnan equilibrium for a cell?
Definition

1. Affects the resting membrane potential

2. Creates the fixed negative charge in a cell because big, negatively charged ions are unable to get out of a cell.

3. Contributes to ion movement into and out of a cell

Term
describe the indirect effect of the Na/K ATPase on the resting membrane potential
Definition
The pumps creates a concentration gradient across the membrane that allows ions that were originally pumped to flow back down their gradients throguh ion leakage channels
Term
What would you calculate with the chord conductance equation?
Definition
net diffusion potential
Term
Describe how the Na/K ATPase generates an electrogenic pump potential
Definition
By pumping 3Na+ ions out and 2K+ in, it creates a charge difference across the membrane with it being more positive outside and more negative inside
Term
Approximate equilibrium potentials for K+ and Na+. Approximate resting membrane potential
Definition

K: around +60

Na: around -90

RMP: -90

Term
Rank these factors on biggest effect on Resting membrane potential: Gibbs Donnan potential, indirect effects of Na/K ATPase, Direct (electrogenic) effect of ATPase.
Definition

Indirect effect of Na/K ATPase (80% contribution)

Gibbs-Donnan potential (14%)

Direct effect of Na/K ATPase (6%)

Term
What equation do you use to calculate resting membrane potential
Definition

Em=Ediff+Ep

 

Ediff = diffusion potential (calculated by chord conductance equation) - combined contributions of Gibbs-Donnan effect and charge separation

Ep = electrogenic ion pump potneital (-4mV, unless otherwise given)

Term
Threshold during an AP is the point at which (a) channels open. Depolarization is due to the rapid influx of (a) into the cell, which causes the membrane potential to become more positive, toward that ion's equilibrium potential of +60mV. Repolarization is when (a) channels close and (b) channels open to bring the membrane potential down closer to RMP. Hyperpolarization is when (b) channels remain open and bring the membrane potential lower than the RMP, closer to that ion's equilibrium potential of -90mV.
Definition

a = Sodium

b = potassium

Term
A ___ channel is opened or closed by changes in membrane potential and is what action potentials result from.
Definition
voltage-gated ion channel
Term
What is the effect of activation of voltage-gated Na+ channels in neurons, skeletal muscle, and cardiac muscle cells.
Definition
Na+ rapidly enters cell, causing depolarization during AP
Term
Identify 4 specific Na+ channel blockers
Definition

2 neurotoxins:

TTX (tetrodotoxin)

STX (Saxitoxin)

 

and 2 local anesthetics:

Lidocaine

Tetracaine

Term
___ channels are the basis for APs in cardiac and smooth muscle
Definition
Voltage-gated Ca++ channels
Term
Compare and contrast L-Type and T-Type Voltage-gated Ca channels. Duration (kinetics), voltage activation (threshold), pharmacology, location, and function
Definition

L-type:

Long lasting

high threshold (>-30mV)

blocked by DHP's

Located in heart, skeletal muscle, neurons, smooth muscle, uterus, and neuroendocrine cells

Function to link depolarization to intracellular Ca signaling

 

T-type

Transient

low threshold (<-30mV)

not easily blocked by DHPs

Found in SA node and brain neurons

Function by repetitive firing of APs in heart and neurons

Term
Describe the mechanism of release of a neurotransmitter from a chemical synapse and the effect of the neurotransmitter on the post-synaptic cell.
Definition
Neurotransmitter is released from the presynaptic cell, through the synaptic cleft, and then binds to receptors on the postsynaptic cell. it induces a fast or slow response in the postsynaptic neuron
Term
Summarize the synaptic propertie of electrical, inotropic, and metabotropic synapses
Definition

Inotropic - form transmembrane ion channels that open and allow ions to flow upon binding of a ligand

 

Electrical - form voltage-gated channels where electrical gradients form allowing ions to move between cells.

 

Metabotropic - are indirectly linked with ion channels, but do not form them. When the ligand binds, the synapse releases signals which then leads to the opening of an ion channel

Term
Describe the sequence of events at the neuromuscular junction leading to the AP in the skeletal muscle cell
Definition

1. Presynaptic cell contains vesicles of acetylcholine. When it is released, it binds to the nicotinic acetylcholine receptors on the postsynaptic cell.

2. When Acetylcholine binds, it increases permeability of that membrane for cations, which allows Na and K to move and results in depolarization of the membrane, first by the opening of ligand-gated Na/K channels (graded response) and then throguh the opening of voltage-gated Na channels once threshold is reached.

3. The AP travels across the sarcolemma and down the t-tubules and triggers the release of Ca2+ from the sarcoplasmic reticulum and triggers muscle contraction through cross-bridge cycling

Term
Describe and differentiate betweeen EPSPs and IPSPs in neurons
Definition

EPSP - Excitatory postsynaptic potential. the electrical impulse that causes depolarization down the axon hillock during a synaptic transmission. makes it  easier for an AP to occur. Na moves in, Cl- moves out.

IPSP - inhibitory postsynaptic potential. the electrical potential results in hyperpolarization of the cell due to Na coming back in the cell. keeps another AP from occuring. Na+ moves out, Cl- moves in.

 

Both are graded potentials

Term
Differentiate between temporal and spatial summation (facilitation)
Definition

Temporal - several impulses from one neuron over time.

Spatial - multiple impulses from several neurons occuring at the same time.


Whether or not threshold is reached is dependent on these summations.

Term
3 types of muscle and what kind of cells stimulate them
Definition

skeletal: electrical stimulation by somatic motor neurons

cardiac: electrical stimulation by autorhythmic cells through gap junctions

smooth: neuron stimulus or gap junctions

Term
Describe the excitation process of cardiac muscle
Definition
Pacemaker (autorhythmic) cells generate a spontaneous depolarization that reaches threshold to start action potentials in the SA and AV nodes without external stimuli
Term
What is the contractile component of skeletal muscle? What is the series elastic component of skeletal muscle/
Definition

contractile component: sarcomeres

series elastic component: cytoskeletal material connecting myofibrils to ends of fibers, connective tissue that anchors fibers to tendons, and tendons that anchor muscle to bones... all generate passive force when stretched and act like a rubber band.

Term
Describe active and passive force as they apply to isometric skeletal muscle contraction
Definition
during isometric contraction, sarcomeres shorten, generating active force. then sarcomeres begin to "take the slack" of the series elastic component, genrating passive force.
Term
Describe the length/tension curve as it applies to active, passive, and total force generation during isometric contraction of skeletal muscle
Definition

active - optimum length of 100-120% for generating maximum active force. any length overlap or below 100% when contracting decreases force. any length greater than 120% decreases force.

 

passive - force generation increases as the series elastic components are stretched past their resting state.

 

total force - maximum total force is generated when active and passive forces are generated from the optimum length.

 

Term
Describe threshold stimulus and maximal stimulus as they apply to whole muscle contraction
Definition

threshold - minimum stimulus required to get a measurable twitch

maximal stimulus - minimum stimulus that results in recruitment of all motor units for that muscle, generating the most force of contraction possible for that muscle

Term
Describe an isotonic twitch in skeletal muscle. discuss the effect of increasing load on the characteristic of an isotonic twitch
Definition

isotonic twitch has 3 phases:

latent - muscle is developing tension without changing length

plateau - muscle is shortening at constant tension

relaxation - muscle tension decreases to zero

 

the larger the load, the longer the latent period and relaxation periods, but the shorter the plateau period. once the load force exceeds the muscle force, it is isometric contraction (no plateau because no change in muscle length)

Term
Describe the isotonic force/velocity curve as it relates to skeletal muscle
Definition

the smaller the load, the higher the velocity.

velocity is highest with no weight

when load > power of contraction = isometric contraction = no velocity

the shorter the muscle fiber, the smaller the load to reach isometric contraction, so larger muscles can maintain a higher velocity for longer

Term
Which generates more force, a muscle with sarcomeres in parallel or one with sarcomeres in series?
Definition
parallel. larger muscles tend to have more sarcomeres in parallel and thus generate more force
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