Unit 1 - Homeostasis Flashcards
(30 cards)
definition of homeostasis:
the mechanisms used to maintain the parameters of internal environment under conditions of dynamic equilibrium
def of internal changes
are changes that we can control so you need water → trigger you to become more thirsty so you drink water
def of external changes:
you go outside and it is cold → triggers arm hairs to go up to try and keep you warm
ways of measuring homeostasis:
Establish values and use homeostatic ranges
Ex. glucose in blood → normal range is 75-96. This is because a normal value will never been accurate but a range is more accurate
purpose of regulatory mechanisms:
How our body compensates the changes of homeostasis
types of regulatory mechanisms:
Local mechanisms: responses mediated by the cells at the site of the dysregulation
Long distance mechanisms: responses mediated by control centers that involves a general response
Components of a long distance reflex pathway: - 9
- input singal: needs to be received by a receptor. They are changes in a parameter (temperature, pressure, pH) that initiate the mechanism
- Sensor or receptor: is the sensing components and monitors and responds to the changes
- Threshold: the amount of stimulus change necessary to initiate the mechanism. If a stimulus is below the threshold, no response loop is initiated
- Afferent pathway: connects the receptor with the control center
- Nervous system: afferent neurons
- Endocrine system: the endocrine cell acts as both receptor and control center - Integrating center: processes the input signal, compares it with the homeostatic range and provides a response
- Efferent pathway: connects the control center to the effector through a chemical messenger (hormone) or a motor nerve
- Target: cell or tissue responsible for bringing about the normal state
- Response:
- Cell response: specific responses on target cells
- Systemic response: consequences for the body derived from the cell response - Feedback loops: going back to normal
positive feedback loops: - 4
- Not many examples
- Physiological but not homeostatic
- The response magnifies or reinforces the initial stimulus, and an outside factor is required to shut off the cycle
- Example: giving birth
negative feedback loops: - 3
- They are homeostatic, thus they are present most reflex pathways
- The response opposes the initial stimulus, shutting off the response loop
- They stabilize the variable and maintain it within the homeostatic range
Nervous system vs endocrine system:
types of fluid in the body: - 3
- Intracellular (ICF)
* Fluid inside each cell (cytoplasm) - Extracellular ECF
* Fluid surrounding the cells
* Subdivisions:- Interstitial fluid (IF), non circulating
- Plasma and lymph (circulation)
- Transcellular
* Synovial fluid in joints, fluid, pericardial fluid, intraocular fluid and CFS
* Always filled with fluid either intracellular and extracellular
extracellular and intracellular fluid main component
Extracellular fluid main component: Sodium: Na+
Intracellular fluid main component: potassium: K+
Although the molecules are different the final concentracion should be the same so that extracellular and intracellular compartments are isosmotic → having the same or equal osmotic pressure
electrical neutrality:
Neutral net charge within each compartment (same amount of positive and negative charge in outside and inside of cells) but electrical disequilibrium among them
three mechanisms that cooperate to keep a normal pH range of plasma:
Normal pH range of plasma is 7.38-7.42
- Buffers (bicarbonate)
- Ventilation (lungs)
- Kidneys
when does pH changes occur
under physiological circumstances (exercise) or pathological states (alkalosis, acidosis)
loss vs gain water fluid
- To maintain a constant volume of water in the body, there has to be a balance between water intake and excretion
- Pathological water loss disrupts homeostasis affecting blood pressure and osmolarity
loss vs gain water fluid between ICF and ECF - osmosis:
If both compartments are isosmotic (same concentration, same number of particles) the net movement of water is balanced; the same amount of water moves in and out of the cell
If osmolality is altered (ex by excessive sweat or too much salt intake) there is net movement of water in or out of the cells, producing changes in cell volume and disrupting cell function
what happens when both compartments are isosmotic
isosmotic = same concentration, same number of particles
the net movement of water is balanced: same amount of water moves in and out of cell
what happens if osmosis is altered in cell + ex of altering osmosis
there is a net movment of water in or out of the cells producing changes in cell volume and disrupting cell function
ex of altering osmosis: excessive swear or high salt intake
bulk flow:
movement of fluid between capillaries (blood vessels) and surrounding interstital space
oncotic pressure def+purpose
caused by proteins in plasma
proteins pull water back into the capilaries
IF has fewer proteins so water tends to move toward the plasma
mediate fluid balance between plasma and IF
hydrostatic pressure def+purpose
pressure from the blood pushing outward on the capilary walls it tends to push fluid out of the capillaries into the IF
mediates fluid balance between plasma and IF
fluid between plasma and IF
bulk flow during capillary exchange
mediated by starling forces: oncotic pressure (comes from the different amount of proteins in both compartments) and hydrostatic pressure (a component of blood flow)
a balance between filtration and absorption is needed
% of body weight is water in most adults
50-60%
