Homeostasis Flashcards
Homeostasis definition
maintenance of a constant and normal internal environment
Homeostatis principles
variables operate within a narrow range
balance between demands on body and body’s response
Dynamic constancy
MAP remains constant
due to baroreflex response/kidney function
Changes in body core temp during submaximal exercise
reaches a plateau
steady state = variable unchanging
Intracellular control systems
protein breakdown and synthesis
energy production
maintenance of stored nutrients
Organ systems
pulmonary and circulatory systems
replenish oxygen and remove carbon dioxide
Biological control system definition
series of interconnected components that maintain a physical or chemical parameter at a near constant value
Sensor/receptor
detects changes in variable
data to control centre
Control centre
assess input and initiates response
Effector
changes internal environment back to normal
negative feedback –> homeostatis
Stimulus
change of internal conditions
Cell signaling definition
communication between cells using chemical messengers
coordinates cellular activities
important for maintaining homeostasis
5 cell signaling pathways in cells:
- intracrine signaling
- juxtracrine
- autocrine
- paracrine
- endocrine
Intracrine signalling
CM inside cell triggers response
Juxtracrine signaling
CM passed between 2 connected cells
Autocrine signaling
CM acts on that same cell
Paracrine signaling
CM act on nearby cells
Endocrine signaling
CM (hormones) released into blood (affects cells with specific receptor to the hormone)
Negative feedback definition
response reverses the initial disturbance in homeostatsis
reduce effect
back to normal
Example - control of CO2 conc in extraceullar fluid
- increase in extracellular CO2 triggers a receptor
- sends info to respiratory control centre
- respiratory muscle activated to increase breathing
- CO2 conc returns to normal
Positive feedback definition
biological response increases the original stimulus
Example - childbirth
- initiation of childbirth stimulates receptors in cervix and sends message to brain to release oxytocin from pituitary gland
- oxytocin promotes increased uterine contractions
Gain (or sensitivity of the response) definition
degree to which control system maintains homeostasis
example - pulmonary and cardiovascular systems
= more capable of maintaining homeostasis
Regulation of body temp
thermal receptors send message to brain
response by skin blood vessels and sweat glands regulates temp
Exercise disrupts homeostatsis
changes in pH, PO2, PCO2 and temp in cells
inability to maintain steady state = fatigue/end exercise
Set point
37 degree celsius
Adaptation
change in structure and function of cell or organ system
= improved ability to maintain homeostasis
Acclimation
adaptation to environ stresses (heat)
= improved function of existing homeostatic system
Hormesis definition
process in which a low-to-moderate dose of potentially harmful stress resuslts in a beneficial adaptive response on the cell or organ system
Exercise-induced hormesis
optimal training
Positive feedback loop
acts to increase an effect
when a change occurs in a system, that change becomes amplified
example - menstrual cycle
Feedforward loop
results in physiological responses in anticipation of a change in a variable
example - increase HR before race
Submax exercise
exercise generate heat from working muscles
= increase body temp
detected by thermoreceptors
relayed to hypothalamus
increase vasodilation/sweating
negative feedback loop = limit increase
heat loss/gain = balanced = temp constant = steady state
When does HR reach steady state at submax exercise?
5 mins
Hormesis applied to exercise
training adaptations initiated
after exercise - cessation, recovery, repair = return to baseline/trigger adaptive mechanism
load/recovery period suboptimal = overtraining/undertraining
