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Homeostasis and Hormonal Control - Coggle Diagram
Homeostasis and Hormonal Control
Homeostasis
is the maintenance of a constant internal environment
Negative feedback where your body reacts to bring about an opposite effect to changes detected
Normal -> stimulus (increase or decrease) -> receptor (detects change) -> control centre -> corrective mechanism (brings reverse effect) -> stimulus reverses -> back to normal
Regulating the water potential of blood and tissue fluid
To ensure they are kept at a constant water potential, hence the blood plasma and tissue fluid must be kept within very narrow limits. If not, they can cause cells to swell and burst or crenate.
Water potential is normal
Water potential increase due to large intake of water (stimulus)
Hypothalamus stimulated (receptor)
(corrective mechanism)
• Less ADH released by pituitary gland into blood
• Less ADH transported to kidneys
• Cells in walls of collecting duct less permeable to water
• Less water absorbed, more water excreted (hence more diluted and more urine produced)
Water level decreases back to normal
Water potential decrease due to loss of water through sweating (stimulus)
Hypothalamus stimulated (receptor)
(corrective mechanism)
• More ADH released by pituitary gland into blood
• More ADH transported to kidneys
• Cells in walls of collecting duct more permeable to water
• More water absorbed, less water excreted (hence more concentrated and less urine produced)
Water level increases back to normal
Regulating blood glucose concentration
Body cells need glucose for cellular respiration. Hence, Islets of Langerhans in pancreas secrete hormones insulin and glucagon. Normal is around 70-90 mg/100 cm3 of blood
Blood glucose conc is normal
Blood glucose concentration rises above normal (stimulus)
Islets of Langerhans in pancreas stimulated (receptor/ control centre)
(corrective mechanism)
• Islets of Langerhans secrete more insulin into blood
• Insulin to blood and muscle
• Insulin increases permeability of cell membrane to glucose. Glucose absorbed more quickly into cells
• Insulin increases rate of respiration (so glucose is used)
• Insulin causes liver and muscles to convert excess glucose to glycogen to be stored in liver and muscles
Blood glucose dec to normal. This provides feedback to pancreas to reduce insulin production
Blood glucose concentration falls below normal (stimulus)
Islets of Langerhans in pancreas stimulated (receptor/ control centre)
(corrective mechanism)
• Islets of Langerhans secrete more glucagon into blood
• Glucagon to blood and muscle
• Glucagon causes conversion of stored glycogen back to glucose
• Glucagon stimulates conversion of fats and amino acids into glucose
• From liver, glucose enters blood
Blood glucose inc to normal. This provides feedback to pancreas to reduce glucagon production
Regulating blood temperature
To ensure Enzymes can work as they only can work in a certain range of temperatures
Arteriole
dilate so more blood is sent to
blood capillaries
in the skin (
vasodilation
). Arteriole constrict to reduce amt of blood flowing through capillaries in skin (
vasoconstriction
).
Secreted sweat from
sweat glands
(mainly water, dissolved salts and some urea) flows through a
sweat duct
to a
sweat pore
that opens at
skin (excretory organ) surface.
Hair
stands up right when
hair erector
muscles contracts during cold conditions, which helps trap air which is a poor conduction of heat, raising the temperature back to normal temp.
Nerve ending (thermoreceptor)
lets you sense temp changes.
Heat gained by the body
is released within the body as a result of metabolic activities (eg. cellular respiration, vigorous muscular exercise, consumption of hot food, being in warm environments like a hot day outside). High levels of cellular respiration takes place in liver and muscles, hence a lot of heat is released in these organs. Heat is distributed to the rest of the body via the blood stream.
Heat lost by the body
is affected by amt of blood flowing through skin capillaries through skin surface.
When skin arteriole dilates, blood flow to skin increase. More heat is carried to skin surface to be lost at skin surface. Blood flows away from skin though venule.
When skin arteriole contricts, blood flow to skin decrease. Less heat is carried to skin surface to be lost at skin surface. Blood flows away from skin though venule.
Homeostatic control of body temp when body temp inc
Normal body temp
Body temp rises above normal
Thermoreceptors in skin and hypothalamus are stimulated
Skin arteriole dilates
, blood flow to skin increase. More heat is carried to skin surface to be lost at skin surface. Blood flows away from skin though venule.
Sweat glands become more active
and produce more sweat to be evaporated at skin surface and lose more heat.
Metabolic rate (speed at which body uses energy) is decreased
to decrease amount of heat released within body.
Body temp decreases to normal temp
Homeostatic control of body temp when body temp dec
Normal body temp
Body temp falls below normal
Thermoreceptors in skin are stimulated. Impulses are transmitted from thermoreceptors to hypothalamus in brain.
Skin arteriole constricts
, blood flow to skin decrease. Less heat is carried to skin surface to be lost at skin surface. Blood flows away from skin though venule.
Sweat glands become less active
and produce less sweat to be evaporated at skin surface and lose less heat.
Metabolic rate (speed at which body uses energy) is increased
to increase amount of heat released within body. When all these responses aren't sufficient,
shivering
(reflex contraction of body muscles) occurs. Rapid contraction and relaxation of skeletal muscles increase amt of heat released.
Body temp increases to normal temp
A
Hormone
is a chemical substance produced in minute quantities by an endocrine gland. It is transported into the bloodstream to target organ(s) where it exerts its effect(s).
Hormone can influence growth, development and activity of a hormone. They help to control and coordinate body activities
Exocrine glands (exo: outwards) are glands that have ducts/tubes to carry away their secretion.
Examples: Salivary glands has salivary duct to carry saliva to mouth. Sweat gland has a duct to carry sweat out the body.
Endocrine glands (endo: within) are ductless glands that don't have ducts to carry away its secretions. Secretions are secreted directly into bloodstream.
Examples: Pituitary gland secretes ADH.
Pituitary gland secretes a number of hormones, which control the secretion of several other endocrine glands. It is called the 'controller' or 'master gland'.
Hypothalamus regulates secretion of some hormones.
Islets of Langerhans in pancreas secrete insulin and glucagon
Ovary secretes oestrogen and progesterone
Testis secrete testosterone
Lack of secretion of insulin increases blood glucose conc as glucose cannot be stored or utilised by tissue cells. Some blood glucose is subsequently lost in urine (
diabetes mellitus
). Muscles have no reserves of glycogen, body grows weak and continuously loses weight.
Oversecretion of insulin decreases blood glucose conc which leads to a condition called shock, seizures/fits or collapsing/passing out
Diabetes mellitus/ diabetes is a disease in which the body is unable to control its blood glucose concentration in order for it to remain within normal limits.
Type 1 diabetes (Juvenile/early-onset diabetes): Develops early in life & inherited. Islets of Langerhans are able to produce or secrete sufficient insulin.
Type 2 diabetes (late-onset diabetes): Occurs later in life & more likely in overweight people. When target cells (such as muscle cells) don't respond well to insulin.
Signs & Symptoms:
Persistently high blood glucose level
Presence of glucose in urine
Frequent urination
Slow/difficult healing of wounds
Weight loss
Thirst
Treatment:
Diabetics must measure their blood glucose conc and test urine regularly.
Must watch their diet carefully, making sure they don't take in too much carbohydrates.
Type 1 diabetics have to inject insulin into fat tissue under skin. Also take medication that increases uptake of glucose from blood into cells
1 more item...
Both endocrine and exocrine gland: Pancreas produces pancreatic juice, carried by pancreatic duct to duodenum. Pancreas also has Islets of Langerhans which secrete insulin and glucagon into bloodstream.