7369200
Description
Flashcards by Francisco Sacadura, updated more than 1 year ago
|
Created by Francisco Sacadura
over 7 years ago
|
|
| Question | Answer |
| The RMP of a muscle fiber is close to: a. 0 mV b. -90 mV c. +50 mV d. The K+ equilibrium potential | b and d |
| The RMP is mainly determined by: a. The K+ gradient b. The Na+ gradient c. The Ca2+ gradient | a |
| Use the Nernst equation to calculate E for the following distribution of ions in mammalian SKM (values in mmol/L) (RT/F=26.7mV at 37°C) | |
| Using the data from the previous question calculate the electrochemical gradients for Na+, K+, Ca2+, Cl-, and HCO3- when Vm is -90mV, -30mV, +50mV, and +100mV. | The electrochemical gradient for a particular ion is given by the difference between the Vm and the E. By convention, inward I<0, so for all those values where electrochemical gradient<0, the inward mov of cations (influx) is favored. For I>0 outward mov of cations (efflux) is favored. An electrochemical gradient<0 would give rise to an efflux of anions and a value>0 would give rise to an influx of anions. |
| If Vm=-90mV at rest and +30mV at peak of AP what changes in relative P of Na+ and K+ take place? Hint: Use the Goldman equation ignoring the term for Cl- as it's passively distributed according to the prevailing K+ gradient (you could do the experiment in a Cl-free medium) | At RMP the Na+/K+ P ratio is 0.008 and during the AP it's 5.46, an increase in P of the membrane to Na+ by factor of ~700. The approach provides an understanding of way the Vm can change without changing ionic gradients. Selective alterations in membrane P are key to understanding why synaptic V may either be depolarizing or hyperpolarizing. They also explain changes in Vm seen in non-excitable cells in response to agonists. |
| T/F? Hormones: a. Are chemical signals secreted into blood b. Can influence the behavior of many different cell types c. Act only on neighboring cells d. Are secreted by specialized glands | Only c is F: hormones are secreted by endocrine glands into the blood to act on distant cells. Paracrine signals act locally. |
| T/F? The following are released by 1 type of cell specifically to regulate activity of others: a. NO b. Prostaglandins c. Insulin d. Epinephrine e. Ca2+ f. Glucose g. cAMP | e and f only F. NO and prostaglandins are paracrine signaling molecules. Insulin and adrenaline are hormones. Ca2+ and cAMP are both INC mediators but cAMP can spread from cell to cell via gap junctions. Glucose is a substrate for metabolism. |
| T/F? Receptors: a. Are always proteins b. Are always located in the cell membrane c. May be membrane-bound enzymes d. Can activate 2nd-messenger cascades via GP | Only b is F. Many R are membrane proteins (hydrophilic ligand) but some are INC proteins (e.g.steroid hormone R, hydrophobic ligand). R may directly activate ICH but some are PK activated upon ligand binding. Many R activate GP modulating levels of 2nd messengers |
| T/F? Prostaglandins: a. Are secreted by exocytosis b. Are synthesized from phospholipids c. Are hormones d. Act on GPCRs | a&c are F. Prostaglandins are metabolites of arachidonic acid, which is derived from membrane phospholipids by the action of phospholipases. They are lipid-soluble molecules that are secreted as they are formed. They are paracrine and autocrine signaling molecules which activate GPCRs in the plasma membrane |
| T/F? Steroid hormones: a. Are lipid soluble b. Directly activate ICH c. Can alter gene transcription d. Are secreted as they are synthesized | Only b is F. Steroid hormones are lipid signaling molecules that act mainly by altering gene transcription. As they are lipids they can't be stored in vesicles and thus are secreted as they're synthesized and cross membrane to bind to INC receptors to regulate transcription |
| T/F? a. Only excitable cells have Vm b. RMP can be positive or negative c. Vm generally between -40mV to -90mV d. In excitable cells Vm is a physiological variable e. RMP is an equilibrium potential | a. F (All mammalian cells have Vm) b. F (RMP always <0mV) c. T d. T (In excitable cells Vm changes in response to signals producing APs&GPs) e. F (RMP is a dynamic diffusion potential because relies on const expenditure of E via ion pumps) |
| Which factors contribute to the RMP? | Na+/K+ pump (mainly to maintain it) K+ leak channels (high P to K+) Low P to Na+ (Na+ unable to replace K+)Impermeable to major INC anions-proteins Outward K+ diffusion down c gradient offset by Vm<0 that attracts K+ When 2 tendencies balance =>E(k+)~RMP |
| Why is RMP different from E(k+)? | The exact Vm is determined by all the ion gradients and number and type of open channels (permeability to all ions) |
| Cells communicate in 3 ways: | • Diffusible chemical signals • Direct surface contact (adhesion) • Direct cytoplasmic contact (gap junctions) |
| Cells use chemical signals in 3 ways: | Localized signaling (paracrine & autocrine) Generalized signaling (endocrine) Synaptic signaling (NTs) |
| What is the difference between paracrine, autocrine and endocrine signals? | Autocrine: affect secreting cell itself Paracrine: cells within small radius Endocrine=>hormones released by specialized endocrine glands into blood act on distant targets (with specific R) Difference between paracrine and endocrine: quantity of chemical secreted |
| What are the advantages of synaptic compared to endocrine signaling? | Hormones regulate activity of many cell types but have general and slow effects, whereas neurons are adapted for fast and specific activation of target cell(s) |
| Signaling molecules are very diverse in structure. What are the main 10 chemical classes they can be divided into? | Esters (ACh) AAs (Glu) Amines (adrenaline/epinephrine) Peptides (ADH) Proteins (insulin, growth hormone) Steroids (testosterone, oestradiol) Iodinated AAs (thyroid hormones) Eicosanoids (prostaglandin E2) Inorganic gas (NO) Nucleosides&nucleotides (adenosine) |
| What is the difference between agonist and antagonist? | Agonists activate a receptor Antagonists block the effects of an agonist |
| What are the 4 basic ways cells respond to signals (depending on ligand and R)? | 1- Direct control of ICH 2- Direct control of effector enzyme 3- Indirect (GP) coupling via 2nd messengers/ICH 4- Control of DNA transcription |
| Certain GP subunits activate INC enzymes that synthesize INC signaling molecules (2nd messengers) which act on specific INC targets. Give 3 examples of 2nd messengers and their activity. | cAMP (activates PKA which regulates activity of many enzymes) IP3 (triggers Ca2+ release from INC stores) DAG (regulates activity of some enzymes via PKC) |
Want to create your own Flashcards for free with GoConqr? Learn more.