Homeostasis Flashcards
Homeostasis
The maintenance of a constant internal environment.
Feedback loop
The body responds to a stimulus and the response alters the original response
Negative feedback loop
The response reduces the original stimulus
E.g. Blood glucose, temperature
Positive feedback loop
The response increases the original stimulus
E.g. childbirth
stimulation of pituitary gland to produce more oxytocin for the contractions of the cervix.
Dynamic Equilibrium
state when rates of forward and reverse changes are equal.
E.gThe body makes responses that ensure the BG levels only deviate a little from set point regardless of the body’s activities.
Set Point
Level at which a variable is to be maintained in a feedback system.
E.g. BG is at optimal concentration required by cells in the body
Thermoregulation
maintenance of the balance between heat production and heat loss
HEAT INPUT = HEAT OUTPUT
HEAT INPUT = HEAT OUTPUT
constancy is important because the chemical reactions occurring in cells are very heat-sensitive.
Metabolic Rate
The rate at which cell respiration occurs. OR The rate at which energy is releases into the body by the breakdown of food
Factors change MR
stress and exercise increase metabolic rate
Thermoreceptors
Receptors that detect temperature change.
Central Thermoreceptors
receptors located in the hypothalamus, spinal cord and abdominal organs. Nerve impulses are sent out by the hypothalamus which control activities to maintain body temperature.
Peripheral Thermoreceptors
receptors located in the skin and in some mucous membranes. These provide the hypothalamus with information about the EXTERNAL environment
Heat lost from skin
- sweating (vasodilation)
- environment (peripheral blood vessels carry warm blood to the surface of the skin, and heat from the blood is lost to the environment)
Components of sweat
water containing dissolved substances- sodium chloride, urea, lactic acid and potassium ions.
Decrease Heat Loss
- peripheral vasoconstriction of blood vessels
- reduce surface area to volume ratio
- reduction in sweating
- conscious behaviour (jumper, shelter)
Increase Heat Production
- increase adrenalin production
- increase thyroxine production
- increase muscle voluntary activity (shivering)
Components in Thermoregulation Feedback
Stimulus: change in body temperature
Receptor: thermoreceptors
Modulator: hypothalamus
Effectors: blood vessels and sweat glands
Response: vasodilation, vasoconstriction and perspiration rate
Feedback: change in body temperature
Heat Exhaustion
dehydration and vasodilation cause low BP
person may collapse but temperature is still normal
Heat Stroke
dehydration, high environmental temperatures and high humidity make it difficult for the body to lose heat.
Heat retained = thermoregulation cease = body temperature rises
Hypothermia
falls below 33, metabolic rate is too slow to maintain body temperature
heat lost is greater then heat produced
Increase heat loss
- vasodilation of blood vessels
- sweating
- conscious behaviour (remove clothing)
- increase surface area
Decrease heat production
- Decrease in voluntary activity
2. decreased metabolic rate
6 important factors that must be regulated
- body temperature
- blood sugar levels
- gas concentrations
- body fluid levels
- Ph Levels
- Blood Pressure
Homeostasis Ensures the fluid environment of the cells:
- contains optimum nutrients, ions, gases and water
- stays at a constant temperature
- stays at a constant pressure
