Homeostasis Flashcards
(27 cards)
Homeostasis
The process whereby the body’s internal environment is maintained in a steady state
Why is homeostasis important
- Homeostasis maintains conditions under cells perform most efficiently
- Under normal circumstances the properties and composition of tissue fluid DO NOT change very much, regardless of the external environment or what we are doing.
Properties of tissue fluid which must be maintained in homeostatic balance
- Body temperature
- Blood pressure
- Fluid concentrations (osmotic, diffusion and electrochemical gradients)
- Acidity (pH)
- Concentration of nutrients, wastes and gases
Tolerance limits
The range of physiological ‘levels’ in which the body can function normally are referred to as its tolerance limits. The upper and lower limits between these levels
Dynamic equilibrium
Fluctuations around the ‘set point’ is called dynamic equilibrium
Steady state control mechanisms
The body processes responsible for maintaining homeostatic balance.
Feedback systems
Homeostasis is essentially achieved through the nervous and hormonal systems in a mechanism known as a ‘feedback loop’ or ‘feedback system’, ‘biofeedback mechanisms’
Feedback system
SRMERF
- Stimulus
- Receptor
- Modulator
- Effector
- Response
- Feedback
Stimulus
The factor that changes and causes a homeostatic mechanism to operate.
E.g increase temperature , increase CO2, decrease blood glucose
Receptor
The structure/cells which are sensitive to stimuli and detect the change
Modulator
Control center of the system which process the receptor and sends information to the effector.
E.g medulla oblongata - control center for breathing, heart rate and vasomotor
Effector
The structure which brings about a response to counteract the stimulus
E.g the diaphragm and intercostals for breathing, thyroid gland for temperature regulation
Response
Change in the effector to maintain homeostasis - the effect on the body to correct the change
- E.g. increase contractions of diaphragm and intercostals to increase breathing rate and depth
Feedback
The monitoring of the new environment and how the original stimulus has been altered.
- E.g. more CO2 removed from lungs
Negative feedback
Homeostasis is maintained by means of negative feedback i.e. the response neutralizes or reverses the original stimulus.
Positive feedback and homeostasis
Positive feedback has no role in homeostasis. Positive feedback reinforces or strengthens the stimulus.
How does the body detect change
Receptors - Structures that are able to detect change in the body’s internal or external environment.
Types of receptors
- Thermoreceptors
- Osmoreceptors
- Chemoreceptors
- Touch receptors
Thermoreceptors
Respond to heat and cold
External thermoreceptors
Skin thermoreceptors - hot or cold (these can’t detect both)
Internal thermoreceptors
Thermoreceptors in hypothalamus
Osmoreceptors
Responds to osmotic pressure, found in hypothalamus
Chemoreceptors
Respond to particular chemicals
External chemoreceptors
Located in nose (odor), mouth (taste)
