physiology focus questions test #1

Question 1

1. What is the basic building block of a typical cell membrane?
   • Be able to draw a diagram to demonstrate the layout of a phospholipid membrane

Answer 1

A phospholipid is the main building block of a typical cell. And water and fats don’t mix! Phosphate head with lipid tail. Between tails there is a thick non-polar layer acting as a semipermeable membrane.

Question 2

2. Define the terms, hydrophobic, hydrophilic, diffusion, osmosis, hypotonic, hypertonic and isotonic (see I told you I would ask this :O)

Answer 2

Hydrophobic- doesn’t not dissolve in water very well
Hydrophilic-friendly with water and dissolves well in water.
Diffusion-Spontaneous movement of a substance from a region of higher concentration to a region of lower concentration without energy(ATP) being involved.
Osmosis-diffusion of water only, across a selectively permeable membrane.
Hypertonic-high concentrations of solute.(70Na & 30H20 in a cell)
Hypotonic-Low concentrations of soute. (10Na & 90H20)
Isotonic-Equal concentrations of solute and solvent 50/50

Question 3

3. What specific layers, if any, of a typical cell membrane are hydrophobic or hydrophilic?

Answer 3

The outer membrane is Hydrophilic and the inner membrane is hydrophobic.

Question 4

• Why are the layers hydrophilic or hydrophobic? (Hint: think about the structure of a phospholipid)

Answer 4

.i Like dissolves like, fats and water don’t mix well. Some things are polar water and some things are non-polar (hydrphobic tails) Tails allow membrane to be selectively permeable.

Question 5

4. Give examples of substances that can and cannot simply diffuse through a semi-permeable membrane

Answer 5

.Cannot: larger molecules, polar molecules. Na, Cl, K (ions/ other water soluble material)
Can:smaller and non-polar molecules can O2 CO2

Question 6

5. For substances that are not able to “easily/simply” diffuse across (through) a cell membrane what types of structures (channels, gates or transporters) and or processes help them to get across the membrane?

Answer 6

.Leaky aka Protein channels (always open) Sodium, Potassium,
Each Ion has it’s own leaky channel
• Gated channels (require key of sorts)(4 specific ones depending on the channel)
i. Mechanical
ii. Chemical
iii. Voltage (electricity)
iv. Thermal
• Transporters help change the gate structure. They move substances across the cell membrane

Question 7

• Which of the processes/ways you listed require ATP to be used and which do not?

Answer 7

Does not = diffusion, Facilitated diffusion Transporter proteins do not use energy, rather the shape of structure and affinity for the substance changes. It is a facilitated diffusion, secondary active transport.
•Active transport requires ATP – This is when you need to move a substance against the concentration gradients and that is why ATP (energy) is needed. An example of this is moving Na and K. It pumps to maintain the gradient

Question 8

6. What does a concentration gradient influence/determine?

Answer 8

RATE AND D
RECTION. The concentration gradient influences the chemical concentration of a cell. (# number of ions) and the electrical concentration (negative or positively charged). They either work with or against each other to make up the electrochemical gradient. Opposite charges have a level of attractive force and Sodium molecules want to be with other molecules so if more is inside they want to join there buddies.

Question 9

7. What is the purpose of diffusion in the body?

Answer 9

.It is important in body fluids, because it tends to eliminate local concentration gradients. It is important for the body to eliminate CO2 by diffusing down the concentration gradient…..traveling from cells interior to the interstitial fluid and then into the bloodstream to the lungs. To regulate the bodys chemical and electrical levels with in each tiyp of cell in the body.

Question 10

8. Why do ions move across a cell’s membrane?

Answer 10

THEY FOLLOW CONCENTRATION GRADIENT. To maintain correct concentration and charge within each of the different types of cells in the body. Since most cells have more Na, Cl, and Ca outside the cell and K inside cell it is important to regulate so it doesn’t reach equilibrium, As it would if left to simple passive diffusion.

Question 11

9. How is active transport different from diffusion? (think of more than one way – think of many!)

Answer 11

Active transport requires some sort of energy to move ions or molecules across the membrane. Diffusion does not take any energy. Active transport does not depend on a concentration gradient. DIFFUSION WORKS TO CREATE A EQUILIBRIUM AND ACTIVE TRANSPORT PREVENTS.

Question 12

10. How are leaky channels different from gated channels?

Answer 12

.Leaky channels are always open gates need a key to open and shut.

Question 13

11. How are channels different from transporters?

Answer 13

.Transporters help to move the substance in and out of a cell. Channels are open and closed depending on the type for a substance to flow through.

Question 14

12. What is the physiological importance of active transport? What would happen if we did not have it?

Answer 14

.Active transport helps cells get what it needs quicker then diffusion. It can do what is needs to do without relying on intra or extra cellular concentrations.Needs to go against the concentration gradient and if it gains equilibrium we would die.

Question 15

13. Name the two different methods that could be used to move glucose across a cell membrane
    • Explain how they are different.

Answer 15

i. Facilitated diffusion by binding to a receptor site on a protein. The protein changes shape and lets the molecule move across the plasma membrane, a continuous channel never occurs.
ii. Secondary active transporter helps move glucose, but it gets a “free ride” because the concentration gradient of Na provides the driving force for the glucose to get in too.

Question 16

14. What determines the rate that glucose can enter a cell? (Think carefully on this one! :O) )

Answer 16

ONLY WORKS WHEN BOTH SUBSTANCES ARE AVAILABLE Na and Glucose.

How many open Glu transportes and or # of NA and Glu transporter and Na concentration outside cell after Na, K, ATP ase pump has pumped 3 Na+ and out 2 K+ in.

Question 17

15. If I place a cell that has a 0.85% NaCl solution inside of the cell into a solution of 0.05% NaCl, what will happen to the cell?
    • Which way will water move and why?

Answer 17

The water will want to move into the cell and the NaCl will want to move out of the cell and into the solution. The inside of the cell will become a Hypertonic solution and expand the cell.

Question 18

17. Define what a membrane potential (MP) is

Answer 18

.is the difference in electrical charge between the inner membrane and the outer membrane.

Question 19

18. What types of cells are excitable?

Answer 19

Excitable cells produce an impulse like muscle (cardiac/skeletal) and nerve cells. SOME GLAND CELLS????

Question 20

19. Describe the concept of an electrochemical gradient

Answer 20

The concept of electrochemical gradient are the two factors that make up and influence diffusion. Sometimes the factors work together and sometimes they work against each other to bring a substance in or out of a cell. The chemical factor has to do with the number of ions in or out of a cell and the electric factor has to do with the charge of the substance and the charge of the cell’s environment. RATE AND DIRECTION of diffusion.

Question 21

20. For an excitable cell, describe:
    a. What ions are involved in generating the membrane potential?
    b. Describe the concentrations of those ions both intracellularly and extracellularly
    c. What direction do those ion move and why in that direction? (Be specific)

Answer 21

a. Na and K and Cl
b. K inside, Cl and Na outside
c. It depends upon the electrochemical gradient. ENa = +60mV EK = -90mV

Question 22

Resting membrane potential:

d. Which of those ions plays a greater role in the value of the resting membrane potential (RMP) and why?
e. What evidence do you have for your claim that “x” ion plays a greater role in the RMP?
- HINT: There is a concept that you could use
f. What protein structures in the cell membrane play a role in establishing the RMP?
g. What protein structure plays a role in maintaining the value of a resting membrane potentially

Answer 22

.D. Potassium because it wants to be closer to the RMP of -70mV
e. Potassium’s electrochemical equilibrium is -90mV
E.ALWAYS MORE LEAKY CHANNELS FOR POTASSIUM
f. Leaky Sodium and Potassium Protein channels letting ions diffuse.
g.3NAout/2Kin using ATPase pump

Question 23

21. Describe how a chemical equilibrium is different from an electrochemical equilibrium.
    • What exactly are the different influences (“forces”) at work with these forces?
    • Does the effect of these different influences remain the same or do they change? Use an example to demonstrate your answer.

Answer 23

A chemical equilibrium only concerns the substance and ions. An electrochemical equilibrium IS DUE TO THE 2 FORCES:ELECTRICAL AND CHEMICAL.

ELECTRICAL TAKES OVER BECAUSE OF THE THRESHOLD

Question 24

22. What does ENa and EK specifically refer to about the membrane potential in association with each ion and what is the value of ENa and EK?

Answer 24

electrochemical equilibrium of either Sodium or Potassium
Ena is +60mV and EK -90mV
Very little to no net diffusion for potassium or Sodium when it reaches these THRESHOLD LIMITS.

Question 25

23. Think about a chemical synapse between two neurons. What type of channels are located on the postsynaptic membrane side of the synapse?

Answer 25

Postsynaptic have chemical gated channels. (Opens in presence of certain chemicals).

Question 26

24. You apply a stimulus (hmm, what kind? Does it matter?) to a cell membrane and ions flow … Does the MP become more negative or positive?

Answer 26

yes stimulus matters, what matters is how it affects the membrane potential. A stimulus must change membrane potential. For example if chemical or voltage gates are open for Na, Na will flow inside and the cell membrane becomes more positive. From -70mv to -55mv and the stimulus makes the action potential. If the ions are Sodium the membrane is becoming more positive.

Question 27

25. What does reaching the threshold of an excitable cell cause to happen in terms of voltage-gated channels and then what does that lead to?

Answer 27

It initiates action potentials and there is a change in permeability and channels open up for ions (mainly Sodium and Potassium) to cross membrane.

Question 28

26. Be able to graph an action potential (AP) and indicate (know the values in the brackets): a. The value of a resting membrane potential and of threshold in millivolts (mV) b. The ions involved in each stage of an action potential c. Direction of ion flux (which way are the ions moving – in or out?) d. Which gates are open/closed? and where in the graph that is taking place e. Different stages of the action potential f. The maximal “+” (positive) charge in the membrane potential in millivolts (mV) g. The maximal “-“ (negative) charge in the membrane potential in millivolts (mV

Answer 28

a. RMP is -70mV and Threshold is -55 b./c. Depolarization Na enters -55 to +30 Repolarization K leaves from +30 to -80?? d. Na is open in the beginning and floods in, K leaves slower and is open for longer. 1. During resting state All gated Na and K channels closed (Na activation gates closed;inactivation gates open. 2. Depolarizing phase; Na channels open 3. Repolarizing phase: Na channels closing and K channels opening 4. Hyperpolarization K channels remain open and Na channels closed Max positive is +30 Max negative is -80

Question 29

27. Describe the refractory period of an action potential – remember there are two parts.

Answer 29

a refractory period, which is divided into an absolute refractory period, during which it is impossible to evoke another action potential, and then a relative refractory period, during which a stronger-than-usual stimulus is required. These two refractory periods are caused by changes in the state of sodium and potassium channel molecules.

Question 30

28. How does the refractory period influence the formation of an action potential? • Why does the intensity of a stimulus need to change during a refractory period in order to initiate a second AP and why is this an issue for only one aspect of the refractory period?

Answer 30

The refractory period is a time for the cell to reset and reboot. This gives it time to get back to RMP -70

Question 31

29. Explain why an AP travels only way (typically, normally).

Answer 31

.It has to travel from presynaptic cell to postsynaptic cell. This is due to the domino effect that occurs with diffusion down the Nodes of Ranvier.

Question 32

30. Describe how a graded current is different from an action potential. Make sure you think about • Where in a neuron these take place and the direction they travel. • How does the strength of the signals change as it travels • Explain any differences in the velocity (how fast) of travel

Answer 32

Graded currents are affected by the ions and there electrical charge or ion diffusion (electrochemical gradient). A graded current occurs from the dendrite to the axon hillock. Once the axon hillock is reached the action potential begins. The ions travel in every direction. As Sodium ions move away from each other in the dendrite they become less prevalent. Once -70 is reached in axon hillock a domino affect occurs and signal changes occur rapidly down the Axon

Question 33

31. Describe the different types of axons (Type A …) in terms of diameter and velocity of impulses

Answer 33

Type A fibers are FAST! will trave at 268mph they have the largest diameter and are mylinated. Good for hearing/sound Type B fibers are smaller in diameter about 20mph, used in peristalsis to move food bolus. Type C fibers are slower (2mph) and smallest in diameter and are unmylinated

Question 34

32. Starting with the arrival of an AP on the telodendria of a presynaptic neuron and ending with the creation of a graded depolarization on the postsynaptic membrane describe in detail the sequence of events that are needed for this to take place. Be as detailed as you can.

Answer 34

******Needs work******The telodendria releases a neurotransmitter to open up the Na only chemically gated channels (NO voltage gated channels in soma or dendrites) into the postsynaptic nerve membrane. Note that the entire RMP is -70mV. Sodium "cloud" now flows into the postsynaptic nerve in all directions making the membrane more positive and depolarizing the membrane. Sodium diffuses mainly the direction of the lower membrane potential. Once the Sodium gets to the axon hillock and makes the value -55mv (reaches threshold). Voltage gated Sodium channels can open at the axon hillock. (Voltage gated channels run along the entire length of Axon.) (1) sodium voltage channels open (Niagara falls style), and the membrane depolarizes rapidly to +30mV; (2) sodium channels close; (3) potassium channels open at +30 (slow flow), and (4) the membrane re-polarizes (slowly with slow amount of K entering)

Question 35

33. Describe how an EPSP and an IPSP are formed – be specific • What neurotransmitters are involved? • Identify/describe the ions involved and direction of ion flow across the cell membrane that leads to an EPSP and IPSP • During a EPSP or a IPSP how does the resting membrane potential change? i. What physiological terms are used to describe the change in the membrane potential? (There are two you want to be thinking of)

Answer 35

.EPSP (Excitatory postsynaptic potentials) or depolarization occurs to create a "fight or flight" stimulus. It decreases its membrane potential by having more Na move in and K moves out. Release Ach,(open's chemical gated channels) sodium ions increase into the cell. IPSP's (Inhibitory postsynaptic potentials) Increase the membrane potential by hyperpolarizing. The is an increase in the ion Cl (negative) so the positive ions (K and NA) are attracted to is so the do not reach the axon hillocks and create an action potential. Or K comes out of the neuron. GABA (nerotransmitter) is released by presynaptic nerve to inhibit.

Question 36

34. What are the terms “EPSP” and “IPSP” referring to specifically – what are they talking about?

Answer 36

Excitatory postynaptic potential and inhibitory postsynaptic potentials. The excited phase means it is decreasing the membrane potential for a "fight or flight" stimulus. Na and K head to the initial segment due to Ach opening chemical gated channels. An Inibitory postsynaptic potential (IPSP) increases the membrane potential (hyperpolarizing occurs) and makes sure there is less of a chance that Action Potentials are produced at the axon hillock because we are trying to sleep! Due to GABA opening chemical gated channels for Cl to flow in and K to flow out.

Question 37

35. Do excitatory and inhibitory postsynaptic membrane regions generate action potential or graded potential?

Answer 37

excitatory postsynaptic membrane also created a graded potentials until it reaches -55mV at axon hillock Inhibitory postsynaptic potentials create a graded potential.

Question 38

16. Describe axoplasmic transport …

Answer 38

Axoplasmic transport is the movement of materials between the cell body and synaptic knobs. It moves in two directions, toward synaptic terminal is anterograde or towards the soma of neuron retrograde. The slow movement or “slow stream” is 1-3mm/day. The fast movement or “fast stream” is 5-10mm/hour.

Question 39

What happens to an ion channel of an excitable cell as a result of a stimulus being applied? (What does a stimulus cause to happen to that ion channel?) • What does that cause to happen then ... How does that stimulus change the membrane’s permeability?

Answer 39

Stop it from having an action potential or speed up the action potential depending on what is released by the presynaptic neuron. (Either Ach or GABA.)

Question 40

37. Describe temporal and spatial summation and how are they the same or different? • Remember you NEED to be specific and detailed in answering this

Answer 40

A temporal summation is a SINGLE synaptic neuron RAPIDLY AND REPEATEDLY stimulating postsynaptic structures. A spatial summation is 2 OR MORE synaptic nobs that will SIMULTANEOUSLY stimulate the post synaptic structure.

Question 41

38. Explain how presynaptic inhibition and presynaptic facilitation takes place – be specific.

Answer 41

Presynaptic inhibition = Less Calcium gated channels are open (no exocytosis) and presynaptic nerve is shutdown. (Make it harder for them to talk to each other) (GABA is released, Ca voltage gated channels stay closed) FORCED TO QUIT!! Presynaptic facilitation takes place when Serotonin is released, more Ca is released because channels stay open longer. MORE exocytosis, more neurotransmitter released!

Question 42

39. What is the function of presynaptic inhibition and presynaptic facilitation?

Answer 42

Influencing a post synaptic neuron by inhibiting or facilitating the presynaptic structure. Prevent it or help it!

Question 43

40. How are the effects of neurotransmitters (NT) reduced or terminated (ended)?

Answer 43

Less Ca is released due to closed voltage gated channels. This happens because of the GABA released from presynaptic neurons

Question 44

41. What is an MAO and an MAOI? | • What do the letters stand for?

Answer 44

``` MAO = monoamine oxidase MAOI = monoamine oxidase inhibitors ```

Question 45

How do MAOIs prolong the effects of a neurotransmitter?

Answer 45

It prevents an enzyme from breaking down any neurotransmitter that has a single amino acid in its structure.

Question 46

43. Name a type of medication that is specific for preventing a neurotransmitter’s (NT) reuptake.

Answer 46

SSRI's = Serotonin selective reuptake inhibitors

Question 47

44. Name a type of medication that is “general” (not specific) for preventing reuptake of an NT.

Answer 47

TCA = tricyclics (shotgun approach) effect more then one kind.

Question 48

45. What are cholinergic and adrenergic fibers – why are they called this?

Answer 48

.cholinergic fibers are any fiber that releases acetylcholine (Ach). Adrenergic fibers release norepinephrine. Adrenaline releasing fibers!

Question 49

46. Name the two specific types of cholinergic and adrenergic receptors

Answer 49

cholinergic - Nicotinic receptors (many) and Muscarinic M1-M5 Adrenergic - Alpha and Beta

Question 50

47. What neurotransmitters bind with cholinergic or adrenergic receptors?

Answer 50

Cholinergic = acetylchoine

Question 51

48. In terms of the sympathetic and parasympathetic nervous system, which has cholinergic and/or adrenergic receptors?

Answer 51

parasympathetic is boring used for acetylchoine in presynaptic and nicotinic and muscarinic receptors in postsynapic with acetylcholine released in postsynaptic and nicotinic and muscarinic. Sympathetic presynaptically releases acetylchoine for muscarinic and nicotinic postsynaptically it releases norepinephrine for alpha and beta receptors

Question 52

49. Describe the specific effects of the different neurotoxins on the formation of action potentials or the ability of neurons to stimulate a postsynaptic structure as discussed in seminar.

Answer 52

BTX (Brotrodotoxin) increases voltage gated sodium channels to remain open so it cannot go back down to -80. Pufferfish toxin (TTx) tetrodotoxin inhibits voltage gated channesl for Na to open. Botox inhibits exocytosis of neurotransmitters. Either way with too much Na or too little Na your body goes into paralysis. (Excess exocytosis over stimulates until it doesn't work.) Heavy metals destroy schwan cells