Homeostasis,body Fluids,and Transport Mech Flashcards
What is homeostasis following that what is ECF?
The body maintains a relatively stable internal conditions even though the external environment changes continuously.
A constant internal milieu is required for good health
Homeostatically regulated variables
Homeostatic mechanisms operate continuously maintain all the time It has to have a sensor that initiate a response the variable are maintain to homeostatic.Blood glucose levels increase after eating, the levels change over short periods of time but remain constant over long period of time.
regulated(sensed) variable is _ and the non regulated (controlled) variable is_
- blood pressure because a sensor exist for this variable
- heart rate there is no sensor for these variables
The_ is the normal range for regulated vairable while the _ detects value of regulated variable and transduce stimulus into a physiological signal
- Setpoint
- Sensor
They are part of the control center in homeostatic . This one_ compare value of new frequency and the second one interprets error signal and determines the output of effectors_
- Error detector
- Integrator exemple of this one is the neuron, circuit or brain region
It change value of regulated variable like in muscle tone exemple of this one is cells, tissues, smooth muscles and glands
Effectors
change that turn variable to the set point
Effectors from homeostatic regulatory system
homeostatic imbalance
- Depend on external resources
- Sensors respond within a limited range of stimulus values
Homeostatic imbalance exemple
certain disease or illnesses characterized as a loss of homeostasis in one or more systems. Dramatic changes in just one variable can have life threatening consequences. When homeostasis is lost for one varaible, it may trigger a series of changes in other variables leading to a cascade of problem . One exemple if an individual keeps running he might pass out eventualy.
Negative feedback
returns variable to set point
Positive feedback
pushes variable away from set point
feed-forward control
anticipatory;minimizes changes to variables
Fluid in the blood (plasma) there is 7 % of water in this compartiment
extracellular fluid (ECF)
Between cells and contain 26 % of water
Interstitial fluid (ISF)
It contains 67% of water
Intracellular fluid (ICF)
transport of substances across the Peripheral membrane
- Passive transport: no energy input is required
- Active transport: energy ATP is required to move substance against their concentration gradient (uphill)
It is going downhill and involves diffusion-movement of molecules from high to low; referred to as moving down a concentration gradient; differnet kind exist: simple diffusion, facilitated diffusion and osmosis
Passive transport
how does diffusion works?
all molecules have random , high speed movement due to their intrinsic kinetic energy. The movement results in collision between molecules. When the dye is evenly distributed there is no more net movement because there is no more concentration gradient
Factors that affect diffusion rate
- Molecular size
- Temperature
- Concentration
- Surface area
- Medium (viscosity)
It is reached when there is no net movement of molecules in either direction. This one happens naturally and doesnt require energy
Equilibrium
Simple diffusion through memebranes
Non polar, lipid-soluble (hydrophobic) substance diffuse directly through phospholipid bilayer.
oxygen, carbon dioxide, steroid hormones, fatty acids and small amounts of very small polar substance like water can pass
Facilitated diffusion
Larger, non-lipid soluble, or polar molecules can cross membrane but only with assistance of carrier molecules
1. Carrier-mediated
2. Channel-mediated
use different types of integral membrane proteins
it imprat differnt properties to the transport process
Carrier-mediated facilitated diffusion
certain hydrophilic molecules (glucose, amino acids and ions) are transported passively down their concentration gradient by carriers (transmembrane proteins)
- each of the carrier transports specific substance
- binding of molecule causes carrier to change shape and results in molecule being moved across membrane
Channel-mediated facilitated diffusion
some integral membrane protein form channels that allows ions to diffuse across the membrane
- ion channels show selectivity for a particular type of ion (Na and K) based on chanel diameter, charged residues lining pore, water of hydration
regulation of diffusion through ion channels
ion channel-open or closed state. Opening and closing channels is known as gating
- for a given electrochemical gradient the number of ions that are conducted by the channel depends on :
1. how often the channel opens
2. How long it stays open
gated channels: 1. Ligand-gated; 2. Voltage-gated; 3. Mechanically-gated
a given ion may pass through several types of channels
Three factors determine the magnitude of solute flux through a mediated transport system
- The extent to which the binding sites are saturated
- The number of transporters in the membrane
- The rate at which the conformational change occurs
there are two type of carrier mediated transport
- Facilitated diffusion
- Active transport
Primary active transport
the hydrolysis of ATP provides the energy for primary active transport
Transporters are ATPases-enzymes that hydrolyze (breaks down using water ) ATP.
Na+/K+ ATPase pump
Na+/K+ ATPase pump
- The transporter(with bound ATP) binds 3 Na+ on inside of cell (low affinity for K+)
- ATPase activated. Auto-phosphorylation
- Conformational change and release of Na+ to outside
- Increased affinity for K+ allows two K+ to binds
- Dephosphorylation and return to original conformation. Release of K+ to inside.
Na+/K+ ATPase establishes electrochemical gradient
The pumping activity of the Na+/K+ ATPase establishes and maintains the characteristic distribution of high K+i and low Na+ inside and high Na+ and low K+ outside
The Na+/K+ ATPase estacblishe chemical gradient that can be used to do work
Between 10 to 40 % of the ATP a cell produces under resting condition is used by the Na+/K+ ATPase pump to maintain the sodium gradient
Role of electrical force in ION movements
The unequal distribution of ions induces a seperation of electrical charges across the plasma membrane - called the membrane potential (electrical force)
The direction and magnitude of ion fluxes across membrane depend on both the concentration and the mmebrane potential. The two driven forces are known as electrochemical gradient
secondary active transport
the energy stored in an electrochemical gradient can be used to drive the transport of other solutes.
The movment of an ion down its electrochemical gradient is coupled to the transport of another molecule (ex. glucose, amino acids)
These transporters have binding sites for ion (usually Na+) and the cotransported molecule.
It uses the stored energy of an electrochemical gradient to move both an ion and a second solute across a membrane
cotransport (symport)
The ion and the second solute cross the membrane in the same direction
the movement of Na+ is always downhill, from high to low
countertransport (antiport)
the ion and the second solute move in opposite directions
downhill from high to low
osmosis
water diffuses across plasma membrane
- some through lipid balayer
- mostly through specific water channels called aquaporines
The flow occurs when the water concentration is different on the two sides of a membrane
= movement of solvent across a selectively permeable membrane
a semi permeable membrane is called_
osmosis
osmolarity
total number of solute particles in a solution
1M glucose is 1 osmol/L
1M NaCl ionizes to Na+ and Cl- (2 particles) is 2 Osm (osmolar)
1M solution of MgCl2 is 3 Osm
A 3 Osm solution may have 1 M glucose and 1 M NaCl
- ICF and ECF is 300 mOsm
membrane permeable to both solutes and water
both solute and water molecules move down their concentrstion gradients
memebrane permeable to water, impermeable to solutes
water moves by osmosis from an area of higher to lower water concentration (lower to higher solute concentration )
hydrostatic pressure
outward pressure exerted on cell side of membrane caused by increases in volume of cell due to osmosis
osmotic pressure
inward pressure due to tendency of water to be pulled into a cell with higher osmolarities
the more solutes inside the cell, the bigger the pull on water to enter, resulting in higher osmotic pressures inside the cell
when hydrostatic pressure equals osmotic pressure there is_
no further net movement of water occurs
where the water trying to get out= water trying to get in
Refers to the concentration of ALL solutes, peetrting (p) and non-penetrating (np)
Hyper-osmotic, iso-osmotic and hypo-osmotic
refer to the concentration of non-penetrating solutes
Hypertonic, isotonic and hypotonic
Na+, Cl- and K+
hypotonic solutions
cells take on water by osmosis until the become bloated and burst (lyse)
It contains a lower concentration of non penetrating solutes than are present inside cells
hypertonic solutions
cells lose water by osmosis and shrink
contains a higher concentration of nonpenetrating solutes than are present inside the cells
Isotonic solutions
Cells retain their normal size and shape
same solute/water concentration as inside cells; water moves in and out
