physio exam 1 part 1

homeostasis

• maintenance of stable conditions in body’s internal environment

• dynamic “equilibrium”

• e.g. blood glucose

• maintaining the volume of and composition of body fluids

• maintaining many other physiological parameters (blood pressure, body temperature)

• ECF composition maintained = ICF composition maintained

body fluid compartments

• icf (introcellular fluid)

• ecf (extracellular fluid)

• total body water (volume = 40 L, 60% of body weight)

icf (intracellular fluid)

• 2/3 of body fluids

• volume = 25 L

• 40% of body weight

• fluid within cells

ecf (extracellular fluid)

• 1/3 of body fluids

• volume = 15 L

• 20% of body weight

• fluid outside cells

• the internal enviornment when talking about homeostasis

two categories of ECF

plasma

• fluid within blood vessels/vascular system, surrounds blood cells)

• 20% of ECF

interstitial fluid

• fluid outside vascular system, in small spaces between tissue cells

• 80% of ECF

exchanges between fluid compartments

cell membranes separate ICF and ECF

• exchange of solutes and water can occur

blood vessel walls separate plasma and interstitial fluid

• exchanges can occur at capillary beds

disturbances in homeostasis

external environment

• changes in weather: extreme heat/cold

internal environment

• blood glucose spikes right after meal, declines if you haven’t eaten in a while

• dehydration (loss of water from ECF) can result in water movement out of cells, cell shrinkage

negative feedback loops

• response reverses the initial change in the variable

• brings body back to homeostasis

• stabilizes physiological variables

• sweating, regulation of blood glucose levels, blood pressure

positive feedback loops

• response enhances/reinforces the initial change brought about by the stimulus (more and more)

• blood clotting, childbirth

ions

• are charged atoms or groups of atoms

• are atoms or molecules that have gained or lost electrons

• Na+, Cl-, Ca2+, HCO3-

electrolyte

• are substances that conduct an electric current

• ions or ionic compounds that dissociate into ions when placed in H2O

• important electrolytes → Na+ and K+

• most solutes in body fluids are electrolytes

anions

negatively charged ions

cations

positively charged ions

acid

• molecule that releases H+ into solution

• carbonic acid

• as [H+] increases → more acidic

base

• molecule that combines with H+

• bicarbonate

• as [H+] decreases, more basic

pH

• neutral: pH = 7.0

• acidic solutions: pH < 7.0

• basic solutions: pH > 7.0

• human blood is slightly basic: 7.35-7.45

buffer systems

• maintain the pH of a solution by combining with/releasing H+ ions

• carbonic acid-bicarbonate buffer system

organic molecule types

carbohydrates, lipids/fats, proteins, nucleic acids

carbohydrates

• important source of chemical energy of the body

• are hydrophilic (attract water)

• monosaccharides (one + simple), disaccharides (two + simple), polysaccharides (many + complex)

lipids/fats

• are hydrophobic (fear of water + not soluble)

• triglycerides

  • major source of stored energy in the body

• phospholipids

  • chief components of cell membranes

• cholesterol

  • structural basis for manufacture of all body steroids

• lipoproteins

  • lipoid and protein-based substances that transport fatty acids and cholesterol in the bloodstream

proteins

• made from chains of monomers called amino acids

  • amino acids connected via peptide bonds

• enzymes - catalyze chem reactions

• keratin - hair, nails, skin

• collagen - tendons, ligaments, skin, blood vessels

• can also be called polypeptides

• 20 different amino acids

nucleic acids

• DNA - stores our genetic information, double-strand, thymine

• RNA - transcribed from DNA, template for protein synthesis, single strand, uracil

• nucleotides - monomers make up DNA and RNA

• base - part of nucleotide that differs btwn RNA and DNA

main component of cell membrane

phospholipids

• have hydrophilic (water-loving) heads and hydrophobic (water-fearing) tails

simple diffusion

• substances move directly through phospholipid bilayer

• O2, CO2, fat-soluble substances, urea, water

osomsis

• diffusion of water across a membrane

• water moves directly through membrane range and via aquaporins

• direction of water movement is determined by solute concentrations of solutions on either side of membrane

• moves from more dilute to less dilute solution = moves from lower solute concentration to higher

facilitated diffusion

• substances diffuse through protein channels in membrane; substances usually charged

• common channels: K+, Na+, Cl-, Ca2+

• carrier-mediated, channel-mediated

• protein carriers move substances across membrane

• include larger substances (glucose)

active transport

• requires a membrane protein and energy (ATP)

• substances move from low to high concentration (up/against concentration gradient)

• primary and secondary

primary active transport

• carrier protein breaks down ATP and uses resultant energy to pump one or more substance against gradient (energy comes directly from ATP breakdown)

• the sodium-potassium pump

secondary active transport (cotransport)

• relies on the energy stored in on gradients that have been created by primary active transport

• always involves more than one substance: one substance moves against its gradient, the other moves down it gradient

  • symport: substances moved in same direction

  • antiport: substances moved in opposite directions

Na+ -K+ -ATPase (sodium-potassium pump)

• primary active transport - moving against gradient concentration

• moves 3 Na+ ions out of the cell AND moves 2 K+ into the cell

  • Na Na Na OUT, Na Na Na OUT, K K in inside

• necessary for maintaining water balance, proper nerve, muscle, and cardiac functioning, and secondary active transport to occur

electrochemical gradient

• combination of concentration gradient and charge gradient that exists across all cell membranes

• ICF

  • High [K+], Low [Na+], Low [Cl-], High [organic anion (A-)], Low [Ca2+]

• ECF

  • Low [K+], High [Na+], High [Cl-], Low [organic anion (A-)], High [Ca2+]

resting membrane potential

• potential when cell is in homeostatsis (not responding to a stimulus)

• -70mV value for most (usually -40 to -90 mV)

• established by the unequal leakage of K+ and Na+ down their gradients, large anions in the ICF which cannot cross the membrane, and Na+ -K+ pumps