Exam 2 Flashcards
What is Simple Diffusion? Can it occur by more than one method? What substances can cross membrane by simple diffusion?
Random motion of molecules, occurs down the gradient.
Can occur through lipid bilayer and membrane pores/channels
Small uncharged particles : ethanol, glycerol, urea, O2, CO2, NO2 - go through lipid bilayer
Ions and Water pass through pores/channels
Discuss diffusion of electrolytes and non-electrolytes.
Electrolytes - if there is a potential difference across membrane, this will alter the rate of diffusion. Ex - If Na+ diffusing into area of cations then diffusion will slow.
Also, when an ion diffuses down conc. gradient, a potential difference is created called a diffusion potential.
Classify the following ions by ECF and ICF according to their high or low concentrations: Sodium, potassium, calcium, chloride, bicarbonate and proteins.
Na+, Ca2+, Cl-, and Bicarb are high conc. OUTside cell
K+ and proteins are high conc. INside cell
How does the cell maintain steep concentration gradients across the cell membrane?
Electrical charge imbalances and concentration differences play huge roles in maintaining the potential differences
Which substances require a carrier for diffusion and why?
How is diffusion potential generated across the membrane?
Uncharged substances that either cannot mix with lipid bilayer or too large to fit in pores
A carrier (integral membrane protein) is used to cross the membrane
Discuss the three factors that affect carrier-mediated transports.
How do they affect the rate of transport?
Stereospecoficity - the binding sites are stereospecific
Saturation - limited amount of binding sites may reduce solute binding rate
Competition - isomers can bind too reducing solute binding
Define Osmosis
Discuss effects of hypo and hypertonic solutions on the cell volume
net movement of water across a semipermeable membrane from high conc. water region to low conc. water region, when a barrier restricts the movement of solutes.
Hypertonic = shrinking
Hypotonic = swelling
What is meant by isotonic and isoosmotic solutions?
Which one of these three solutions should be given to dehydrated patient?
Isoosmotic - both solutions have same osmolarity
solution where RBC is normal volume is isotonic
dehydrated patient give hypotonic solution???
Describe the Donnan and Gibbs electrical equilibrium concept.
What is the Donnan effect upon the cell?
Inside of cell is net negative and many proteins cant diffuse outside.
Cl- moves down conc. gradient to inner cell
Na+ follows to maintain electric neutrality
Now inner cell is hyperosmotic (more conc.) so Donnan effect brings water into the cell
Swelling/lysis no happen cuz Na+/K+ pump pumping Na+ out of the cell
What is active transport?
Differentiate between primary and secondary active transport methods.
Which substances are co-transported?
Counter-transported?
Transport of solutes against conc./electrochemical gradient.
Primary - ATP is the direct source for energy in transport
Secondary - Gradient energy is the source for transport
Co-transported = symport = Na+ with glucose or AA in intestinal and renal tubule cells.
Counter-transported = antiport = Na+/K+ pump
Describe the Na/K pump
Found in ALL cell membranes
Keeps extracellular conc. of Na+ high and intracellular conc. of K+ high
3Na+ pumped out for every 2K+ pumped in
Electrogenic since creates charge separation
Describe the Ca2+ pump
found in sarcoplasmic reticulum
pumps Ca2+ ions agains their gradient
responsible for low conc. of Ca inside cell
Describe the H+/K+ pump
found in parietal cells of stomach mucosa
pumps H from ICF to the stomach lumen to acidify
What is the effect of cardiac glycosides on ATPase carrier complex?
cardiac glycosides disrupt the phosphorlyation-dephosphorlyation cycle.
this leads to higher conc. NA+ inside the cell and decrease in K
Describe the two types of ion channel gates.
What controls them and what passes through them?
What is the significance of these gates?
Voltage-gated Channels : open and close according to changes in membrane potential
Ligand-gated Channels : controlled by hormones, secondary messengers, and neurotransmitters. enable rapid communication between neurons and between neuron and muscle or gland cell. Insensitive to voltage change.
Na, K and Ca
Allows electrical impulses and cellular communication
In what way is the Na/K pump electrogenic?
Pumps 3 Na out for every 2 K in and creates a charge separation or potential difference.
Discuss the activation of voltage-gated Na+ channel.
2 gates, activation outside and inactivation inside.
Both need to be open for Na+ flow
Activation opens quickly, inactivation closes after time delay
Discuss the activation of voltage-gated K+ channel.
Both need to be open for Na to flow through
resting state inside gate is closed causing build up of K before go outside cell
when membrane gets more positive, gate slowly opens allowing K to go outside.
open at about same time Na inactivation closes
What is the importance of Ca channels?
Are they clinically relevant?
Allows Ca to enter the neuron
L-type channel in muscle
N type in nerves
Increased conc. inside cell promotes neurotransmitter release and enzyme activity
To treat CV disorders prescription blocks L-Channels
Specific spider bite blocks Ca influx
Discuss diffusion potential and equilibrium potential.
What is the main purpose of the Nernst equation?
Diffusion Potential - charge across a selectively permeable membrane when ions diffuse down conc. gradient.
Equilibrium potential - the diffusion potential either balances or opposes the initial diffusion down the gradient
Used to calculate equilibrium potential for a given ion as long as gradient and permeability exists.
Define action potential (A.P.) Differentiate between an action potential and a nerve impulse.
AP is an individual and brief depolarization wave that is self renewing and conducted down the length of an axon to convey information
Nerve Impulse is traveling wave of excitation produced by self-propigating APs like falling dominos.
Describe the various phases of an A.P. Be sure to understand the ionic basis and the opening and closing of the various channels and their gates for the development of depolarization, repolarization, and hyperpolarization.
Rest: membrane potential is -70 to -90
Depolarization: rapid INflux of Na+ makes inside more positive (new potential +35)
Repolarization: K+ Efflux making the potential approach resting numbers
Hyperpolarization: becomes more negative than resting potential
Restoration: Na/K pump brings back to normal rates
Know the effect of various poisons, such as tetrodotoxin, or saxitoxin on the functioning of Na ionic channels in the nerves.
Lidocane: blocks Na+ volt channels prevents AP
Tetrodotoxin: blocks Inner Na+ channels
Saxitoxin: blocks Na+ channels causes life threatening paralysis
What is a threshold stimulus?
How many millivolts are needed to elicit an A.P.?
How many mV for depolarization and hyperpolarization?
Minimum amount of stimulus to elicit an AP (open Na gate)
needs to depolarize to -60 then spike to 35+ happens
Hyperpolarization occurs when its -92 or more negative
What is the effect of hypocalcemia on A.P. and muscular contraction?
Na+ channels open even if membrane potential barley deviates from -90mV to less negative
Nerve fibers fire nerve impulses repetitively without stimuli causing sustained muscular contraction - Tetany
Ca2+ ions bind with Na+ channels outer which opens voltage Na+ channel created action potential.
What is the refractory period?
Differentiate between absolute and relative refractory periods.
Explain on the basis of channels and ionic conductance.
When a new stimulus cannot cause a new second action potential.
absolute (ARP) - length of entire initial A.P.
Second AP NOT possible ever
Relative (RRP) - begins when ARP ends and is 1/4 to 1/2 time
Really strong stimuli can cause a second AP
K+ eflux is greater than rest cuz some voltage K gates are still open so harder to depolarize
Differentiate between slow and fast channels.
Which type of channels is found in cardiac, smooth, and skeletal muscles?
Slow - Voltage-gated Ca2+/Na+ channels
Found in smooth and cardiac
Fast - Na+ channels 10-20x faster found in skeletal muscle
What is meant by “Some action potentials have a plateau?”
Where and why do we have a plateau in A.P.?
Potential does not immediately repolarize after spike.
Happens cuz after spike slow opening of slow channels allow diffusion of Ca2+ but Na+ also. Very slow opening of voltage gate K+ channel delays return to resting potential
Found in heart helpful with heartbeat
What is the importance of having rhythmicity in some excitable cells?
Useful in heartbeat, peristalsis and rhythmic breathing.
How is the A.P. propagated?
One AP occurs at hillock and excites nearby segment of membrane which depolarizes to produce another AP
Describe the sequence of events involved in propagation of A.P. Does the initial A.P. travel all the way to the axon
terminal from the axon hillock? Or, does it decay?
AP triggered by influence voltage Na+ channels enough to AP -> local inflow of Na+ that triggers AP also diffuses down axon both ways -> then new trigger as old signal decays
What does the conduction velocity of the nerve fibers mean?
Which two factors affect the conduction velocity, and in which way?
What could be the effect of compression of the nerve fiber on its conduction velocity?
Speed at which AP are conducted along a nerve or muscle fiber.
Greater Diameter and Mylenation is Faster.
Pressure can hinder or block APs
Site two diseases of nerve impulse conduction.
What is the cause for these diseases?
MS - destruction of CNS myelin Cause unknown. possibly autoimmune
Tay-Sachs - defective enzyme which breaks down myelin excessively. Genetic inheritance.
Describe the structure and basic function of three types of muscles.
Make sure that you know the details of the physiologic histology of the skeletal muscle.
Skeletal - long cylindrical parallel cells, striated and voluntary
Cardiac - extends short distances to some major vessels, myocytes connected by intercalated discs. striated and involuntary.
Smooth - short and fusiform spindle shape, non striated and involuntary
Define and describe the muscle fiber
myofilaments,
myofibrils,
sarcomeres
thick and thin filaments.
Muscle Cell containing normal Sarco-structures
Contractile protein filaments
in the sarcoplasm, thousands make up a fiber
Myofilaments of a myofibril are stacked in small compartments - these are contractile unit of muscle
Thick: Myosin protein molecules
Thin: Actin, Tropomyosin, and Troponin
Describe in detail the structure of actin and myosin filaments.
Actin: called g-actin in globular form. polymerized in 2 helical strands to form filimous actin called F-actin. Each actin has a myosin binding site which is covered by a tropomyosin
Myosin - cross bridges that bind actin proteins on the thin filaments, action responsible for muscle contraction.
Describe tropomyosin
filamentous protein that runs in the groove of eacth twisted actin filament and blocks myosin-binding site on actin at rest
Describe troponin
located at regular intervals along tropomyosin filaments, has three globular proteins : troponin T I and C
Describe Troponin T I and C
T: attaches troponin to tropomysosin
I: inhibits actin-myosin interaction by covering myosin binding sites on actin
C: calcium binding protein that binds calcium and plays crucial role in muscle contraction initiation
Describe Light meromyosin LMM
heavy chains in myosin, long and rod like, form myosin tails and bundle together to form body of filament
Describe Heavy meromyson HMM
globular region with short tail in myosin. s1 is globular region, which contains actin binding site and ATP binding site. S2 is the tail region.
Describe titin
largest protein in the body, allows side by side relationship of actin and myosin. lines up the sarcomere. links thick filaments to the Z line
Describe Nebulin
links thin filaments to the Z line
Descibe Myomesin
myosin binding protein present at the m line of thick filaments
alpha actin
bundles actin filaments and attaches them to X line
Describe the 6 steps of how a nerve impulse causes contraction of skeletal muscle.
- AP arrive at synaptic knobs in axon terminal
- Ca2+ ions diffuse into synaptic knobs
- Vesicles release ACh
- ACh binds to receptors in sarcolemma
- Ion channels in sarcolemma open allowing Na+ influx and depolarization. This causes the end plate potential EPP
- The AP spreads in all directions and reaches T tubules.
Describe the 6 steps in Excitation-Contraction Coupling in Skeletal Muscle
- T-Tubules receive AP and carry depolarization from surface to within fiber
- Voltage sensitive Ca2+ channels open and allow release of Ca stored in sarcoplasm. Intracellular conc. now increase.
- 4 Ca2+ ions bind to one Troponin C to cause a conformational change in troponin complex.
- This conformational change causes tropomyosin to shift away and expose myosin bind site
- Cross bridges formed by actin/myosin binding. Power stroke and Recovery stroke both need ATP. This continues as long as Ca2+ is bound to troponin C
- Relaxation. Acetylcholinesterase inhibits nerve impulse. Ca2+ pumped from sarcoplasm to SR where it binds to calesquestrin for storage until next contraction. This causes lack of Ca so troponin complex shift to resting state.
Why do the skeletal muscles become stiff as soon as a person dies?
What is this condition called?
Why do the muscles relax after a day or two?
No ATP. Deteriorating SR releases calcium into sarcoplasm and no energy to pump them back. Ca binds to troponin C and muscles contract but remain contracted because no ATP to release myosin head from actin.
Rigor Mortis
Proteins break down
Describe spastic paralysis and flaccid paralysis and the reasons for these conditions.
Spastic paralysis : continual contraction because of cholinesterase inhibitors prevent breakdown of ACh. Pesticides are examples.
Flaccid Paralysis: no contraction. “Curare” is a poison in blow darts which competes with ACh receptor sites so no stimulation of muscle fiber.
What is the effect of tension on the length of the skeletal muscles?
The tension generated by contraction depends on how stretched or contracted the muscle was before stimulation
Describe Passive tension
tension from stretching a muscle to various lengths.
force exerted by muscle as it is stretched before stimulation
Describe Total Tension
tension developed when muscle is stimulated to contract at different pre-loads
sum of active tension from contractile elements of the sarcomeres + the passive tension caused by stretching of muscle.
Describe Active Tension
Subtraction of the passive from the total tension
It is the additional force above passive force when muscle is stimulated
When stretched more and more, active tension increases then falls as muscle increases in length.
it is at its peak when thick and thin filaments maximally overlap each other and maximum number of cross bridges is formed
Rest length describe
length at which muscle develops maximum tension in response to a stimulus
What is the effect of load on the force of contraction of a skeletal muscle?
When does Vmax occur?
When will the muscle have a zero velocity of contraction?
Force-velocity relationship is determined by allowing muscle to shorten.
force is fixed not length
Velocity of shortening is greatest (Vmax) when after load on muscle is zero
As after load increases, velocity decreases.
If load increase too high, then velosity is zero.
(lift a feather super fast, not a 200 lb bag)
What is a muscle twitch?
rapid force response to single stimulus. quick cycle of contraction and relaxation
What are the phases of a muscle twitch?
Latent period - 2msec between stimulus and onset of twitch. time needed for excitation
Contraction phase - muscle shortening period
Relaxation phase - muscle return to original length
Toatal time is 7 to 100 msec
What is treppe?
if stimuli are repeated in regular intervals, muscle has ample recovery time and successive contractions sho increase in force. This staircase phenom is called Treppe. Example is athletes warming up to increase efficiency.
Temporal Summation
if second stimulus arrives after refractory period but before twitch has relaxed completely then it starts a new twitch that “piggy backs” of first. Second twitch gets higher level of tension.
Describe incomplete and complete tetanus (tetany)
Incomplete - Stimuli are so frequent that complete relaxation no occur and temporal summation occurs. Muscles only relax partially.
Complete - So frequent that no time to relax at all so twitches fuse into a smooth prolonged contraction.
(this happens often and is useful for work) Lifting cup of coffee)
Compare and contrast isotonic and isometric contractions.
Isometric - muscle not allowed to shorten. When you kneel to lift a box, your muscles have tension even thought not move box yet. Slight contraction at cellular level but tension is absorbed by elastic connective tissue around mucle
Isotonic - Tension is so great that it can overcome the resistance, the muscle shortens and moves the load all while maintaining constant tension.
What are the two types of isotonic contraction? How are they used?
Concentric - muscle shortens when contracts (biceps)
Eccentric - muscle lengthens when contracts (triceps)
Use concentric when lifting a barbell and eccentric when lowering it to floor.
Describe production and use of ATP in a resting muscle.
resting muscle breaks down fatty aids through aerobic respiration to make ATP
Surplus ATP is used to build energy reserves of ATP, posphocreatine PCR, and glycogen.
ATP + Cr -> P-Cr + ADP
What is ATP required for?
- providing energy to power Na+/K+ pump
- providing energy for cross-bridge cycle
- powers calcium pump in sarcoplasmic reticulum
- Needed to detach cross bridge after power stroke
Describe ATP in moderate activity
glucose and FA are catabolized aerobically
ATP -> ADP + p
Describe ATP in peak activity
not enough O2 so anerobic glycolysis takes over. lactic acid build up.
ADP + P-Cr -> ATP + Cr
What is lactic acid recycling
lactic acid deyhydrogenase converts pyruvate produced in glycolysis into lactic acid.
Why do you sometimes have cramps and muscle fatigue when you perform strenuous muscle activity?
Explain with the help of oxygen debt, oxygen repayment.
Prolonged muscle use causes fatigue from low oxygen levels. This decreases ATP synthesis and glycogen is used up. Lactic acid builds up and decreases pH and impairs muscle contraction by impairing ATP synthesis
Energy consumed during workout - energy supplied by oxidative metabolism = debt.
(why u breathe real heavy after)
How do professional athletes like John Elway and Randall Cunningham develop muscle endurance, especially a few Days before the football games?
Training and supply of organic nutrients
Carbo-loading to increase glycogen storage
What is malignant hyperthermia? What causes it? Is it useful or detrimental for the patient?
Sensitivity to anesthetics. Exposure followed by full skeletal muscle activation and heat production. Positive feedback loop created causing rapid temp increase and death.
Compare and contrast the slow and fast muscle fibers. Michael Jordan and Karl Malone use what kind of muscle fibers (slow or fast) during their championship games?
How about Picaboo Street when she is doing skiing?
Fast twitch - Short bursts, Use ATP fast. through glycolysis, large white and ton of SR and little myoglobin,fatigue easy,
Slow twitch - prolonged contractions, oxidative metabolism tons of mitochondria, red fibers hight myoglobin, endurance.
