Quiz #1 Flashcards
What are the levels of organization in the body?
cell tissue organ organ system organism
What are the 4 major cell groups/tissue types?
neurons/nerve
muscle
epithelial
connective
What is homeostasis?
the ability to maintain a relatively constant internal environment that is the basis for all physiological function
What are the main components of the negative feedback system for homeostasis?
receptors
- sensitive to change in physiology
afferent nerve
control/integrating centre
- receives info from receptors and interprets it
efferent nerve
effectors
- receives signals from control centre and causes response that returns physiological variable to set point
What are the 3 stages of signal transduction?
reception
- signalling molecule and receptor fit like lock and key, cause transduction
transduction
- molecules/proteins expressed cause a signal transduction pathway leading to a response
response
- activation of cellular responses
What are tight junctions?
found in epithelium
line surface of organs
form a nearly impermeable barrier that keeps cells very tight together
have occludins
What are occludins?
integral proteins that fuse adjacent cells
What are desmosomes?
in cardiac muscle, bladder, and GI muscosa (muscle tissues that are subject to significant mechanical stress)
filamentous junctions that keep cells tight together for strength
What are gap junctions?
made of membrane proteins
link cytosol of 2 adjacent cells for direct, rapid communication
- ions and molecules travel between cells
have connexins
What are connexins?
gap junction proteins that span membranes open to create a channel
How do cells communicate over long distances?
combo of electrical (nerve cells) and chemical (hormones) signals
What are the 2 types of short distance intracellular communication?
direct
- gap junctions
indirect
- chemical messengers released by one cell act on specific receptors of another
What are autocrine signals?
signals that act on the same cell that secreted them
used by immune system
What are paracrine signals?
signals secreted by one cell that diffuse to and act on an adjacent cell
What is the difference between neurotransmitters and neurohormones?
neurotransmitters diffuse across a small gap to the target cell
neurohormones are released into blood for action at distant targets
What is the role of membranes?
separate material and allow exchange of material between cellular and intracellular fluid
What is selective permeability?
allow certain molecules (small, non-polar) to pass through but restrict others (large, polar, ionic) from entering
What is the difference between passive and active transport?
passive:
- spontaneous, downhill, doesn’t require energy
- high to low concentration
active
- non-spontaneous, uphill, requires energy
- against a concentration gradient
What is the chemical driving force?
concentration gradient pushes particles from higher to lower concentration areas
What are the 2 types of ions?
cations - positively charged particle
anions - negatively charged particles
What is membrane potential?
force caused by unequal distribution of charges across the cell membrane
charge separation acts as a source of energy
measured in millivolts
at rest, inside is more negative than the outside
What principles guide the electrical driving force?
opposite charges attract, like charges repel
What does the direction of the electrical driving force depend on?
polarity of the cell
charge on the particle
What does the magnitude of the electrical driving force depend on?
strength of membrane potential
amount of charge on the particle
What is the electrochemical driving force?
sum of electrical and chemical forces
if they act in the same direction:
magnitude is the sum of both
direction is same as both forces
if they act in different directions?
magnitude is the difference between them
direction is that of the stronger force
When will equilibrium potential equal membrane potential? (force = 0)
when electrical and chemical force are equal and in opposite directions
What does the Nernst equation find?
the equilibrium potential of an ion
What is the lumen?
interior cavity of a hollow organ/vessel
What are glands?
organs specialized in the synthesis and secretion of a product
formed by epithelial cells
What are the 2 types of glands?
exocrine
- secrete a product into a duct leading to the external environment
- ex. sweat glands
endocrine
- secrete hormones into the bloodstream
- ex. pituitary gland
What are hormones?
chemicals that communicate a message to the cells of the body
What is the most diverse tissue type?
connective
primary function is to provide support for structures or link them together
ex. bone, blood, fat
What is the extracellular matrix?
mass of non-cellular material containing a dense meshwork of proteins and other large molecules
What is the intracellular fluid? What are its contents?
water present in the fluid within cells
2/3 of total body water
many proteins, rich in potassium
What is extracellular fluid? What are its contents?
water present in fluid outside the cells
1/3 of total body water
sparse proteins, rich in sodium
What are the components of the extracellular fluid?
plasma
the liquid, non-cellular part of blood
rich in proteins
20% of ECF
interstitial fluid
bathes most cells in the body
proteins are scarce
80% of ECF
What are the types of feedback?
negative
when the system and regulated variable have an inverse relationship
positive
when the system and regulated variable have a positive relationship
- less common
What features determine a molecules permeability in a selectively permeable membrane?
size
molecular charge
electrical charge
lipid solubility
What is bulk flow?
movement of gases/liquids according to pressure gradients
What is diffusional equilibrium?
when there is an equal concentration of a molecule on both sides of a membrane
no net transfer of molecules
What is flux?
rate of movement of a given particle over time
as concentration gradient increases, so does net flux
What is simple diffusion?
doesn’t require either energy or a membrane protein
What factors affect simple diffusion?
magnitude of concentration gradient molecule size/shape temperature electrical forces lipid solubility thickness of membrane
What is facilitated diffusion?
passive transport through a carrier
still does not require energy
What are the characteristics of a carrier for facilitated diffusion?
transmembrane protein
has specific binding sites
binding occurs on one side at a time
What factors affect the rate of transport for facilitated diffusion?
rate of transport for each carrier
concentration gradient
number of carriers in the membrane
Describe the role of the GLUT4 transporter in diabetes.
transporter insertion is stimulated by insulin
lack of insulin means less GLUT4 inserted into membrane, less glucose uptake, more glucose in the blood
What are the characteristics of channels?
transmembrane protein
functions like a pore/passageway
substance specific
What are the types of channels?
ion channels:
leak
gated
bidirectional
aquaporins
What factors affect the rate of transport through channels?
transport rate of each channel
number of channels in the membrane
state (open or closed)
What are the 3 types of gated channels?
ligand
- open time depends on binding of ligands
voltage
- open time depends on voltage difference across the membrane
mechanical
- open time depends on stretch level of a membrane
What are carrier proteins?
proteins that bind to substrates and carry them between intracellular and extracellular compartments
open only to one side of the membrane at once (different than a channel)
transport molecules too big to travel through channel proteins (ex. glucose)
What are the 3 types of carrier proteins?
uniport
- transport only one kind of substrate
symport
- move 2+ substrates in the same direction
antiport
- move 2+ substrates in opposite direction
What is active transport?
requires cell energy to move a molecule against its concentration gradient
What is primary active transport?
needs ATP directly
ion pumps
What is secondary active transport?
does not need ATP directly
kinecitc energy from another ion travelling down its gradient drive pump
What is the difference between cotransport and countertransport?
cotransport = same direction
countertransport = opposite directions
What are pumps?
membrane protein
functions as a transporter and an enzyme
has specific binding sites
demonstrates saturation
Describe the sequence of the Na+/K+ pump.
open to inside with affinity for Na+
once 3 Na+ have bound, hydrolysis of ATP releases phosphate group that binds to pump
P-group causes conformational change that flips direction of pump opening to ECF, releases 3 Na+
pump now has affinity for 2 K+, once 2 K+ have bonded, phosphate group dissociates
loss of P-group reverses conformational change, opening back towards ICF
releases 2 K+ into ICF, restarting cycle
What is sodium-linked glucose transport?
an example of cotransport
when Na+ is bound to transporter, affinity for glucose increases and can bind, causing conformational change, releasing once Na+ dissociates on the inside
Na+ moving down its gradient drives glucose against its gradients
What is osmosis?
diffusion of water through a membrane in response to solute concentration
water moves to dilute more solute-concentrated side until equilibrium is reached
through aquaporins
What is osmolarity?
total solute concentration of a solution
solute particles displace water
for molecules that don’t dissociate (ex.Na+):
1 mole solute = 1 osmole in 1L of water
for molecules that do dissociate (ex. NaCl):
1 mole solute = 2 osmole in 1L of water
osmolarity of ICF/ECF is about 300mOsm
accounts for permeating and non-permeating solutes
What is the difference between iso-osmotic, hypo-osmotic, and hyperosmotic?
iso = same concentration
hypo = solution has lower concentration
hyper = solution has higher concentration
What is osmotic pressure?
the ability to pull water
directly proportional to solute concentration
more concentration of solute = less concentration of water = more osmotic pressure
What is tonicity?
water gradient across a membrane caused by impermeable solutes
outside relative to inside
What are the 3 modes of tonicity?
isotonic = doesn’t alter volume
hypertonic solution = cell shrinks, water leaves
hypotonic solution = cell swells, water enters
What are the types of endocytosis?
phagocytosis
- cell extends membrane around matter, once surrounding it forms phagosome in cytosol, fuses with lysosome to breakdown particle, usable components are taken
- cell eating
pinocytosis
- plasma membrane develops an indentation, outer edges pinch together to form endosome
- cell drinking
receptor-mediated transport
- endosome formed, receptor proteins recognize and bind to specific ECF particles, vesicle coated in clathrin forms, clathrin and protein coat are recycled, uncoated vesicle forms with lysosome for breakdown
What is exocytosis?
different vesicles bud up against cell membrane and release contents into ECF
What are the 2 membrane layers?
apical
- faces lumen of body cavity
basolateral
- faces internal environment (interstitial fluid)
What is transcytosis?
for moving even larger molecules (macromolecules)
involves endocytosis and exocytosis
Why must exocytosis and endocytosis of a cell be balanced?
so the size of the plasma membrane does not change
