13.1 Flashcards
What is homeostasis
Maintenance of relatively constant internal environment in living organism.
Two types of factors of internal requirement needed to be maintained for cells to function at optimum level
Physical factors
Chemical factors
Example of phys and chem factors
Body temp blood pressure osmotic pressure
Salt and sugar levels, partial pressures of oxygen and CO2
What is negative feedback mechanism
A corrective mechanism which reverses the original change and brings system back to normal
Receptors for temperature
Hypothalamus
Thermoreceptors
Physical and chemical methods of regulating body temp
Erector muscles
Skeletal muscles
Arterioles
Sweat glands
Adrenal gland
Thyroid gland
The erector muscle process of regulating body temp
Hot
Less stimulated - do not constrict
Hair lower towards skin
Thin layer of air trapped between fine hair
Heat can be released quickly
Cold
Stimulated - Contract
Fine hair stand erect
Thick layer of air trapped between fine hair
Insulator - prevent loss of heat
Arterioles regulating body temp
Hot
Dilate (vasodilation)
More blood flow to skin surface
More heat loss through radiation
Cold
Constrict (vasoconstriction)
Less blood flow to skin surface
Less heat loss through radiation
Skeletal muscle regulating body temp
Hot
Less contract and relax
No shiver
Cold
Contract and relax
Shiver
Generates heat (constriction of muscles require energy)
Sweat glands regulating body temp
Hot
More sweat
Heat absorbed to evaporate sweat
Cools skin
Cold
Not stimulated
No sweating
Adrenal gland regulating body temp
Hot
Less stimulated to secrete adrenaline
Metabolic rate decrease
Cold
Secretes more adrenaline
Speed up conversion of glycogen to glucose
Metabolic rate increase
Oxidation of glucose release heat
Thyroid gland
Hot
Reduce secretion of thyroxine
Metabolic rate decrease
No excess heat generated
Cold
Secrete more thyroxine
Increase metabolic rate
More heat generated
What happens with high blood sugar level
Pancreas
Beta cells in pancreatic Langerhans cells are stimulated
Insulin secreted into blood
Adipose cells (due to stimulation by insulin)
Use glucose in process of cell respiration
Convert excess glucose to glycogen (stored in liver and muscle cells)
Converts excess glucose to fat
What happens with low blood sugar level
Pancreas
Alpha cells in pancreatic Langerhans cells are stimulated
Glucagon secreted into blood
Liver (due to stimulation by glucogen)
Convert glycogen to glucose
Breakdown fat to fatty acids (metabolized to produce energy)
What happens during vigorous activity (CO2)
Partial pressure of CO2 is higher
In blood plasma,
CO2 + H2O ←> Carbonic acid ←> Hydrogen ions + bicarbonate ions
PH of blood in brain decrease
Changes in PH detected by chemoreceptors in medulla oblongata and in carotid and aortic body (heart and neck)
Send impulse to respiration and cardiovascular control centres in medulla oblongata
Send impulse to intercostal muscles, diaphragm and cardiac muscles
Stimulated to contract and relax faster
Breathing, heart and ventilation rate increase
More CO2 exhaled and partial pressure of CO2 drops
Blood pH goes back to normal level
