Unit 1 Flashcards
Define Homeostasis
the tendency of a living body to maintain relatively stable conditions
negative feedback loop
a mechanism that keeps a variable close to set point; the body senses a change and reverses it
receptor
a structure that detects a change in the body
integrating center
what processes the information and makes a decision and directs the response (typically the brain)
effector
a cell or organ that carries out the final corrective action
what is an example of a negative feedback loop?
a thermostat
positive feedback loop
a mechanism that detects a change and increases the change rather than bringing it pack to set point
function of lipids
contribute to membrane tension, rigidity, and overall shape
structure of the plasma membrane
the boundaries of a cell that is made of lipids and proteins
function of proteins
bind chemical signals to trigger internal changes and catalyze reactions
saturation
as solute concentration rises, rate of transport rises, but only to the transport maximum
glycocalyx and it’s function
“fuzzy” outer layer of the cell membrane and functions as the cell “fingerprint.” It protects, gives immunity to infection
Transport material through a cellular membrane
plasma membranes and organelle membranes have selectively permeable membranes which allow some, but not all things from passing through
Diffusion
the net movement of particles from a place of high concentration to a lower concentration. (passive mechanism, no ATP)
filtration
where particles are driven through the membrane by physical pressure. (Passive, no ATP)
osmosis
the net flow of water through a selectively permeable membrane. (passive, no ATP)
primary active transport
when a carrier moves solute through a membrane up its concentration gradient (Active, uses ATP)
aquaporins
special channels for water that increase the rate of osmosis
Secondary Active transport
where a carrier moves solute through the membrane but only uses ATP indirectly.
endocytosis
brings material into cell
exocytosis
releases material from cell
osmolarity
osmotic concentration; the quantity of nonpermeating solutes per liter of solution
tonicity
the ability of a surrounding solution to affect fluid volume and pressure in a cell
hypertonic solution
all water leaves the cell toward the higher concentration of soutes, causing the cell to shrivel/shrink
isotonic solution
the cell would remain the same, with no movement of water
hypotonic solution
all water would go into the cell toward the higher concentration of solutes, causing the cell to grow
passive transport
requires no ATP; things move down the concentration gradient from high to low concentration
active transport
requires ATP; things move up the concentration gradient
uniport
a carrier that moves one type of solute (ex: calcium pump)
symport
a carrier that moves two or more solutes simultaneously in the same direction (ex: sodium-glucose transporters)
antiport
a carrier that moves two or more solutes in opposite directions (ex: sodium-potassium pump)
Types of endocytosis: phagocytosis
engulfing and destroying large particles; “cell-eating”
Types of endocytosis: pinocytosis
taking droplets of ECF containing molecules useful in the cell; “cell-drinking”
Types of endocytosis: Receptor-mediated endocytosis
particles bind to specific receptors on the plasma membrane
How many types of RNA are there? and list them
3: messenger RNA (mRNA), ribosomal RNA (rRNA), transfer RNA (tRNA)
DNA (deoxyribonucleic acid)
a long thread-like molecule with a uniform diameter in a double helix shape
RNA
single nucleotide chain that functions mainly in the cytoplasm of the cell and build proteins
5 universal properties of muscle:
Excitability, conductivity, contractility, extensibility, elasticity
Excitability
responsiveness to chemical signals, stretch, and electrical changes across the plasma membrane
conductivity
local electrical excitation sets off a wave of excitation that travels along the muscle fiber
contractility
shortens when stimulated
extensibility
capable of being stretched between contractions
elasticity
returns to its original rest length after being stretched
myofibril
long protein cords occupying most of the sarcoplasm
thick filaments
made of several hundred myosin molecules and responsible for contraction and regulating contraction
thin filaments
composed of 3 protein types: fibrous actin, tropomyosin, and troponin
fibrous actin
2 intertwined strands of globular actin subunits, each with an active site that can bind to a head of a myosin molecule
tropomyosin
each block 6 or 7 active sites on G actin subunits
troponin
small calcium binding protein on each tropomyosin molecule
elastic filament
made of huge springy protein called titin. runs through the thin filament. helps stabilize and position the thick filament. prevents overstretching.
sarcomere
the functional contractile unit of a muscle fiber. Composed of: I bands, A bands, H bands, M line, and z disc
I band
Light band; include actin (thin filament) only
A band
dark band where thick and thin filaments overlap; include actin and myosin
H band
not as dark; middle of A band; includes myosin (thick filament) only
M line
dark, transverse protein in the middle of the H band
Z disc
protein complex that provides anchorage for thin and elastic filaments
Phases of Muscle Contraction
- Excitation
- Excitation/Contraction Coupling
- Contraction
- Relaxation
Phase 1: Excitation
- Nerve signal arrives and calcium ions enter the terminal
- ACh is released into the synaptic cleft
- ACh binds to receptors on the sarcolemma
- Ligand-gated channels open and calcium flows into the cell while potassium flows out, creating end plate potential
- Action potential is created
Phase 2: Excitation/Contraction Coupling
- Action potential spreads through T tubules
- Calcium released from terminal cisterns of SR
- Calcium binds to troponin
- Tropomyosin moves out of the way for myosin heads to bind to actin
Phase 3: Contraction
- ATP is hydrolyzed into ADP and Pi
- The myosin-actin cross-bridge forms
- The power stroke slides the thin filament over the thick filament
- Binding of new ATP breaks cross-bridge
Phase 4: Relaxation
- Cessation of nervous stimulation and ACh release
- ACh breakdown by acetylcholinesterase (AChE)
- Reabsorption of calcium ions by SR
- Calcium no longer binds to troponin
- Tropomyosin moves back to block binding sites
Sliding filament theory
the mechanism of skeletal muscle contraction where myofilaments do not shorten, but the sarcomere does
sarcoplasmic reticulum
the smooth endoplasmic reticulum that forms a network around each myofibril
length-tension relationship
the amount of tension generated by a muscle depends on how stretched or shortened it was before it was stimulated
three phases of a muscle twitch
latent period
contraction phase
relaxation phase
muscle twitch
a quick cycle of contraction and relaxation when a muscle is directly stimulated with an electrode
latent period
delay just after stimulation of a muscle
contraction phase
external tension is generated and a load is moved as the muscle fiber shortens
relaxation phase
sarcoplasmic calcium levels fall as calcium is reabsorbed into SR, tension declines
temporal (wave) summation
where each new twitch piggybacks on the previous one, generating higher tension
Recruitment (multiple motor unit summation)
the process of bringing more motor units into play with stronger stimuli
size principle
weak stimuli recruit small units and strong stimuli recruit large units
complete tetanus
when unnaturally high stimulus frequencies (in lab experiments) cause a steady contraction
incomplete tetanus
when only partial relaxation between stimuli results in fluttering
concentric contraction
muscle shortens as it maintains tension (ex: lifting weight)
isometric contraction
contraction without change in length
eccentric contraction
muscle lengthens as it maintains tension (ex: slowly lowering weight)
