Study sets, textbooks, questions
Upgrade to remove ads
Physiology Chapter 6
Terms in this set (42)
The extracellular environment includes everything located outside the cells.
Cells receive nourishment from and release wastes into the extracellular environment.
Cells communicate with each other by secreting chemical regulators into the extracellular environment.
67% of our water is within cells in the intracellular compartment; intracellular fluid (ICF)
33% is in the extracellular compartment (extracellular fluid, ECF).
- 20% is in blood plasma.
- 80% makes up what is called tissue fluid, or interstitial fluid; connects the intracellular compartment with the blood plasma.
Contains protein fibers (structural support) of collagen and elastin, and ground substance (glycoproteins and proteoglycans)
Protein fibers provide structural support.
Plasma Membrane Transport
-The plasma membrane is selectively permeable, meaning that it allows some molecules to cross but not others.
-Generally not permeable to proteins, nucleic acids, or other large molecules
-Generally permeable to ions, nutrients, and wastes
Membrane Transport: Noncarrier-mediated
1. Simple diffusion of lipid-soluble molecules
2. Simple diffusion of ions through nonspecific channels
3. Simple diffusion of water = osmosis
Membrane Transport: Carrier-mediated
1. Facilitated diffusion
2. Active transport
Molecules move from higher to lower concentration without using metabolic energy.
Molecules move from lower to higher concentration using ATP and specific carrier pumps.
Diffusion: Plasma Membrane
Small, nonpolar (or uncharged) lipid-soluble molecules pass easily through the lipid portion of the membrane.
Oxygen, carbon dioxide, and steroid hormones
Gas exchange: net diffusion of O2 into cells and CO2 out of cells due to concentration gradients; opposite in lungs.
Water can pass through using special channels called aquaporins in a process called osmosis
Osmosis. what 2 requirements are needed for osmosis?
Water molecules do not carry a charge, so they can pass through the plasma membrane slowly.
This is the diffusion of solvent instead of solute, it is unique - osmosis
Many aquaporins are found in the kidneys, eyes, lungs, salivary glands, and the brain
1.There must be a solute concentration difference on either side of a membrane permeable to water.
2.The membrane must be impermeable to the solute, or the concentration difference will not be maintained.
Solutes that cannot cross and permit osmosis are called osmotically active.
what are aquaporins
Osmotic pressure is the force surrounding a cell required to stop osmosis.
Can be used to describe the osmotic pull of a solution. A higher solute concentration would require a higher osmotic pressure.
Pure water has an osmotic pressure of zero
Osmolality is the total molality of a solution when you combine all of the molecules within it.
A 360 g (2m) glucose solution and a 180 g glucose (1m) + 180 g fructose (1m) solution would have the same osmolality.
These are both 2 Osm solutions
NaCl dissociates into Na+ and Cl- in water and must be counted as separate particles.
NaCl Na+(aq) + Cl-(aq)
1m NaCl solution would actually be a 2 Osm solution.
Tonicity is the effect of a solute concentration on the osmosis of water.
Solutions with a lower solute concentration than the cell are hypoosmotic and hypotonic.
Will pull water into the cell; cell will swell and could lyse
Solutions with a higher solute concentration than the cell are hyper-osmotic and hypertonic.
Will pull water out of the cell; cell will shrivel up and could crenate
Regulation of Blood Osmolality
Constant osmolality must be maintained, or neurons will be damaged.
in the hypothalamus detect increases in osmolality (due to dehydration). This triggers:
-Decreased excretion of water in urine
With a lower plasma osmolality, osmoreceptors are not stimulated, so more water is excreted in urine
Channels: Plasma Membrane
-Charged ions can pass through ion channels that cross the plasma membrane that may always be open or gated.
-Larger polar molecules can not pass through the membrane by simple diffusion but need special carrier proteins
Molecules that are large or polar cannot diffuse across the membrane.
Includes amino acids, glucose, and other organic molecules
Carrier proteins within the plasma membrane move these molecules across.
Specific characteristics (2) do carrier proteins exhibit & understand what saturation and transport maximum are?
They are specific to a given molecule.
The may be competition for similar carriers or molecules
Saturation - number of carriers is limited. Transport Maximun=maximum amount of substance that can be reabsorbed
Powered by the random movement of molecules - no ATP used
Net movement from high to low concentration
Requires specific carrier-mediated proteins
Ex. Glut 4(glucose transport protein)= found in skeletal muscle&fat) control through exercise and insulin
Molecules must be moved from an area of low concentration to an area of high concentration (move uphill)
This requires the expenditure of ATP.
Often, these carrier-mediated proteins are called pumps.
Primary Active Transport
Occurs when the hydrolysis of ATP is directly responsible for the carrier protein function.
The transport protein is also an ATPase enzyme that will hydrolyze ATP
Pump is activated by phosphorylation using a Pi from ATP.
ATPase enzyme pumps 3 Na+ out of the cell and 2 K+ into the cell
Na+/K+ Pump functions
1. Provides energy for coupled transport of other molecules
2. Produces electrochemical impulses in neuron and muscle cells
3. Maintains osmolality
Secondary Active Transport or coupled transport
acquired by moving sodium back into the cell.
Energy comes from downhill transport (facilitated diffusion of Na+) there are 2 types: COTRANSPORT & COUNTERTRANSPORT
Cotransport or symport
molecules/ions move in same direction (ex. glucose- Na+)
Countertransport or antiport
the other molecule is moved in the opposite direction from sodium. (ex. Na+-Ca2+)
movement of molecules through the cytoplasm of the epithelial cells
movement across the tiny gaps between cells
-(OUT)Large molecules such as proteins, hormones, and neurotransmitters are secreted
-Involves fusion of a vesicle with the plasma membrane
Movement of large molecules such as cholesterol INTO the cell requires
Usually a transport protein interacts with plasma membrane proteins to trigger endocytosis.
There is a difference in charge on each side of the plasma membrane due to:
-Permeability of the membrane
-Action of Na+/K+ pumps
-Negatively charged molecules inside the cell
This difference in charge is called
The potential difference make the inside of the cell is negative compared to the outside which is positive
Membrane Potential: K+
K+ accumulates at high concentrations in the cell because:
The Na+/K+ pumps actively bring in K+.
The membrane is very permeable to K+.
Negative anions inside the cell attract cations outside the cell.
Limited by strong concentration gradient.
The K+ concentration inside is 150 mEq/L and out is 5 mEq/L
1. Even with all the K+ inside the cell, the negative molecules inside and all of the sodium outside, the cell is more negative inside compared to outside.
2. This potential difference can be measured as a voltage.
3. Because the membrane is so permeable to K+, this difference is often maintained by K+ concentration gradient
K+ Equilibrium (E*k)
The electrical attraction would pull K+ into the cell until it reaches a point where the concentration gradient drawing K+ out matches this pull in.
K+ would reach an equilibrium, with more K+ inside than outside.
Normal cells have 150mM K+ inside and 5mM K+ outside.
The resulting potential difference measured in voltage would be the equilibrium potential (EK) for K+; measured at −90mV.
This means the inside has a voltage 90mV lower than the outside; this is the voltage needed to maintain 150 mM K+ inside and 5mM K+ outside.
Sodium is also an important ion for establishing membrane potential.
The concentration of sodium in a normal cell is 12mM inside and 145mM outside.
To keep so much sodium out, the inside would have to be positive to repel the sodium ions.
The equilibrium potential for sodium is +66mV.
The membrane is less permeable to Na+, so the actual membrane potential is closer to that of the more permeable K+.
Resting Membrane Potential
Membrane potential of a cell not producing any impulses. Depends on:
Ratio of the concentrations of each ion on either side of the membrane
Specific permeability to each ion
K+, Na+, Ca2+ and Cl− contribute to the resting potential, but because the membrane is most permeable to K+, it has the greatest influence.
A change in the permeability of the membrane for any ion will change the resting potential.
A change in the concentration of any ion inside or outside the cell will change the resting potential.
In most cells, the resting potential is between -65mV and -85mV; neurons are usually at −70mV. These values are close to K+ equilibrium potential
When a neuron sends an impulse, it changes the permeability of Na+, driving the membrane potential closer to the equilibrium potential for Na+.
allow adjacent cells to pass ions and regulatory molecules through a channel between the cells
involves neurons secreting neurotransmitters across a synapse to target cells
A target cell receives a signal because it has receptor proteins specific to it on the plasma membrane or inside the cell.
Nonpolar signal molecules such as steroid hormones, thyroid hormone, and nitric oxide gas can penetrate the plasma membrane and interact with receptors inside the cell.
Large, polar signal molecules such as epinephrine, acetylcholine, and insulin bond to receptors on the plasma membrane
Cyclic adenosine monophosphate (cyclic AMP or cAMP) is a common second messenger.
1. A signaling molecule binds to a receptor.
2. This activates an enzyme that produces cAMP from ATP.
3. cAMP activates other enzymes.
4. Cell activities change in response.
what is the driving force behind diffusion?What types of molecules is the cell membrane permeable vs. impermeable to (need to know specific examples of each)
concentration difference across the cell membrane=concentration gradient
Permeable: NON POLAR: molecules (steroid hormones) & all gas (ex. o2 &co2)
Impermeable: large polar molecules (ex. proteins, glucose, aminoacids) charged inorganic ions (ex. na+, k+, Ca2+)
Recommended textbook explanations
Clinical Reasoning Cases in Nursing
Julie S Snyder, Mariann M Harding
Winningham's Critical Thinking Cases in Nursing
Barbara A Preusser, Julie S Snyder, Mariann M Harding
Sets with similar terms
Chapter 6 - Extracellular Enviornment
Bio 281 Ch. 6
A&P Ch. 5
Other sets by this creator
Mental Health: Childhood and Neurodevelopmental Di…
Mental Health Chapter 11- Childhood and Neurodevel…
Mental Health Nursing Chapter 20: Sexual Dysfuncti…
Chapter 17 Somatic Symptom Disorders: Mental Healt…
Other Quizlet sets
Keystone Bio -Set 3
Physiology Exam 1 Review Chp. 6
Ch.3 Plasma Membrane
Chapter 7: Membrane structure and function
If a person were born with only green and blue cone cells, which color would the person have trouble seeing? How might this condition affect the person?
Identify a nutrient that is at risk of deficiency for each of the following groups: a. teens b. pregnant women c. athletes d. vegans
Replace the underlined words with the correct term. Conflict resolution, advocacy, refusal skills, stress management, interpersonal communication, health skills. _Advocacy_ is a process to help you resolve conflict through cooperation and problem solving.
Name three ways that teenagers can show affection nonsexually.