Homeostasis and Thermoregulation Flashcards
Homeostasis
Maintenance of internal environment
Feedback system consists of a
Stimulus Receptor Modulator Effector Feedback
Negative Feedback Loops
Where the response causes the stimulus to change in a direction opposite to that of the original stimulus
Positive Feedback
The response to stimulus reinforces and intensifies the stimulus
Thermoregulation
Human body Temperature
Heat Gain
- Internal
- Metabolic rate - External
- Radiation or conduction
Heat Loss
- Internal
- Evaporation of water from skin and lungs
- Warm air breathed out
- Warm urine and faeces - External
- Radiation, conduction and convection
Conduction
Transfer of heat via direct contact with another object
Convection
Transfer to heat to air around the body
Radiation
Transfer to heat without contact
Evaporation
Transfer of heat through evaporation of liquid to gas
Temperature Tolerance
- Heat stroke (body temp rises by regulatory mechanisms not working)
- Heat Exhaustion (result of extreme sweating and vasodilation)
- Hypothermia (cored body temp falls below 33 degrees)
Temperature Receptors
- Peripheral thermoreceptors in skin and mucous membranes
2. Central Thermoreceptors in hypothalamus
Thermoregulation Short term Keeping Cool
Stimulus
Increase in body temp
Receptor
Thermoreceptors (central and peripheral)
Modulator
Hypothalamus
Effector
Sweat Glands
Blood Vessels
Cerebrum
Response
Increase sweating
Vasodilation
Behavioural
Thermoregulation Long Term Keeping Cool
Stimulus
Increase body temp
Receptor
Thermoreceptors
Modulator
Hypothalamus
Effector
Thyroid
Response
Decrease metabolic rate, which decreases heat production
Thermoregulation Long Term Keeping Warm
Stimulus
Decrease in body temperature
Receptor
Thermoreceptors (central only)
Modulator
Hypothalamus
Effector
Thyroid
Response
Increase Metabolic rate which increases heat production
Thermoregulation Short Term Keeping Warm
Stimulus
Decrease in body temperature
Receptor
Thermoreceptors (central and peripheral)
Modulator
Hypothalamus
Effector Skeletal muscle Blood vessels of skin Cerebrum Adrenal Medulla
Response Shivering Vasoconstriction of BV Behavioural Adrenaline, Noradrenaline
Osmoregulation in blood
- Water is lost from the blood resulting in blood having a higher osmotic pressure
- High osmotic pressure is detected by osmoreceptors in the hypothalamus
- Water then moves from the intracellular fluid into the plasma via osmosis
- Resulting in lowering the concentration of water in the intracellular fluid which then causes water to leave the cells resulting in the cells to shrivel and shrink
Antidiuretic Hormone
ADH is produced by the hypothalamus and released by the posterior lobe of the pituitary
ADH controls the permeability of the walls of the distal convoluted tubule and the collecting duct
ADH concentration is high this results in the tubules being more permeable to water
This results in water enabled to be reabsorbed
Water leaving the tubule decreases volume of filtrate and increases the concentration of contents
Aldosterone
The Adrenal cortex also secretes aldosterone to increase amount of sodium reabsorbed into blood and increase the amount of potassium excreted into urine
Water is reabsorbed along with sodium so aldosterone can also regulated water content
ADH and Aldosterone work together to regulate water