homeostasis Flashcards
what is the def of homeostasis
a system in which variables are regulated so that internal conditions remain stable
what are 7 key components of homeostasis circuits
- controlled variable
- regulated variable
- sensor
- set point
- error detector
- controller
- effector
controlled variable def
physiological variable that’s manipulated in order to maintain the regulated variable within normal values
regulated variable def
physiological variable for which sensors are present in the homeostatic circuit + is maintained at a stable level by a negative feedback system
sensor def
a “device” that measures the magnitude of a physiological variable by generating an output signal that is proportional to the magnitude of the stimulus
set point def
the range of values of the regulated variable that the homeostatic circuit attempts to maintain
error detector def
determines the difference between the set point value and the actual value of the regulated variable
controller def
it receives information from the error detector + sends output signals to increase or decrease the activity of effectors
effector def
a component of the homeostatic circuit that is activated by the controller to change the value of the regulated variable (physical entity)
what is external disturbance
any change in the conditions of the external environment that result in a change in the internal environment
what is an internal disturbance
any chance in the structure / function of the organism that results in a change to the magnitude of the regulated variable
is homeostasis regulation constant
yes, it continuous process
what is the fundamental mechanism used to maintain a regulated variable within its set point
negative feedback
give an example of a negative feedback system
blood glucose regulation
what is positive feedback
a self-amplifying cycle in which a physiological change leads to a greater change in the same direction, rather than corrective effects of negative feedback
what is an example of positive feedback
blood clotting
what are cell membranes composed of, and what is their function
- double layer of phospholipids and proteins
-determines what enters + leaves the cell
what is the def of simple diffusion
movement of particles from a place of high concentration to a place of lower concentration
what is the def of osmosis
passive transport referring exclusively to the movement of water across the cell membrane via channel proteins
what is the def of filtration
process in which water + solutes are driven through the cell membrane by hydrostatic pressure (high pressure areas to low pressure areas) via passive mechanism
what is the def of facilitated diffusion
carrier-mediated transport of solute through the cell membrane down its concentration gradient in a passive mechanism
what is the def of active transport
carrier-mediated transport of a solute through the cell membrane up its concentration gradient using energy provided by ATP
describe the process of the sodium potassium pump
- Na+ binding induces ATP-mediated phosphorylation of protein
- phosphorylation triggers a conformational change in protein
- conformational change induces the expulsion of Na+ to outside and allows extracellular K+ to bind
- K+ binding triggers release of phosphate
- phosphate loss restores original conformation
- release of K+ restores Na+ site receptivity, allowing cycle to repeat
what is vesicular transport
movement of large particles, droplets of fluid or numerous molecules at once through the cell membrane, contained in bubble-like vesicles of membrane
what does endocytosis mean
bringing material into the cell
what does exocytosis mean
the release of material from the cell
name 3 types of endocytosis
- phagocytosis
- pinocytosis
- receptor-mediated endocytosis
what is phagocytosis
process of engulfing particles such as bacteria, dust and cellular debris
what is pinocytosis
process of taking in droplets of extracellular fluid containing molecules of some use to the cell
what is receptor-mediated endocytosis
phagocytosis / pinocytosis in which specific molecules bind to specific receptors on the cell membrane, and are then taken into the cell in clathrin-coated vesicles with a minimal amount of extracellular fluid
what is nervous signalling
rapid transmission of action potentials, often over long distances + the release of neurotransmitter at a synapse
what is neuroendocrine signalling
release of hormone from a nerve cell + transport of the hormone by the blood to a distant target cell
what do ion channels allow for
for specific charged particles to cross the membrane in response to an existing concentration gradient
name 4 types of ion channels
- chemically-gated channels
- voltage-gated channels
- mechanically-gated channels
- leak channels
what are chemically-gated channels
they open in response to specific chemical messengers (signals) that binds to the extracellular region of the channel
what are voltage-gated channels
they open in response to changes in the membrane potential
what are mechanically-gated channels
they open in response to physical distortion of the membrane surface
what are leak channels
they open and close at random, no actual event opens them and they have an intrinsic rate of switching between open and closed states
what is an action potential
the rapid rise and subsequent fall in membrane potential across a cellular membrane with a characteristic pattern
what is depolarisation
voltage-gated Na+ channels open and positively charged Na+ ions flood into the cell following their concentration gradient
inside membrane becomes less negative
