Introduction Homeostasis Flashcards
homeostasis
process of maintaining a relatively constant/stable internal environment (set point) in spite of changing external environments
set point
the level the body is trying to maintain
external environment
outside the body
internal environment
inside body, outside cells
ECF
intracellular environment
inside cells, cytoplasm
ICF
homeostasis is important for
cell function
examples of homeostasis
BP [Na] [Glu] [K] pH body h2o BT
homeostatic processes restore — to the ECF following disturbance
balance
dynamic constancy
levels change over short periods of time but remain relatively constant over long periods of time
homeostasis is a — process
dynamic, not static steady state (requires energy input) vs equilibrium
physiological variables can change dramatically over a 24 hour periods, but
the system is still in overall balance
when homeostasis is maintained, we refer to —, when it is not, awe refer to —
physiology
pathophysiology
levels of homeostasis (2)
cellular
extracellular
cellular homeostasis (4)
functions of each cell
cytoplasm of single cell
necessary for normal cell function
relies on components of extracellular fluid
extracellular fluid homeostasis (3)
environment outside of the cell
necessary for normal cell function
local vs systemic
local (3)
restricted to one tissue space
utilizes paracrine and autocrines
maintain function of tissue
systemic (3)
involves entire body
utilizes nervous system and endocrine system
maintain function of heart and brain
endocrine system sequence (3)
hormone secreting gland cell
hormone in blood vessel
target cells in one or more distant places in the body
nervous system sequence (4)
nerve cell
electrical signal
NT
neuron or effector cell in close proximity to site of NT release
paracrine sequence (3)
local cell
paracrine substance
target cells in close proximity to site of release of paracrine substance
autocrines sequence (3)
local cell
autocrine substance
autocrine substance acts on same cell that secreted the substance
flowchart outlining systemic homeostatic process mediated by NS or ES
stimulus reflex receptor afferent pathway integrating center efferent pathway effector effector response feedback regulation
stimulus (3)
First Domino
Changes in ECF Composition, Body Temperature, BP, etc.
Changes in [substances]ECF
- Na+, K+, Ca++
- H+ (pH)
- Glucose, O2, CO2
- Endocrine (hormones) and neural (neurotransmitters)
reflex receptor (3)
Detects changes in [substance]ECF
Threshold Stimulus (Sensitivity) - Determines
amplitude of normal range
Can be Cluster of cells, individual cells, cell parts or
molecules in membrane or cytoplasm of cell
normal range
as long as value is WNR it is considered a normal value
afferent pathway (3)
Carries information from Reflex Receptors to Integrating Center
NS Reflexes only
Sensory Neurons
why is the afferent pathway NS reflexes only?
not ED bc the reflex receptor is in the integrating pathway (dont need it)
Integrating Center (3)
Receives stimulus, analyzes information and
generates appropriate response
ES = Endocrine Gland
NS = Brain/Spinal Cord
Efferent Pathway (3)
Carries commands from integrating center to effectors
ES = Hormones (travel via blood)
NS = Motor neurons
Effector
Any cell affected by Efferent Pathway (change in function)
two levels of the effector response
local effector response
systemic effector response
Local Effector Response
how cell (effector) function is changed by the Efferent Pathway
Systemic Effector Response
how ECF (whole body) changed by local effector response
Different Efferent Pathways can create the same systemic effector response while having
different local effector responses
Feedback Regulation
How Systemic Effector Response changes the function of the Reflex Receptor
types of feedback regulation (2)
negative
positive
Negative Feedback
decreases activity shutting off pathway (homeostatic); values fluctuate around the set point
Positive Feedback
increases activity further activating pathway (non-homeostatic)
which feedback is more common?
negative
