Homeostasis Flashcards
What is Homeostasis?
The maintenance of a constant internal environment. Any self-regulating process where biological systems maintain stability whilst adjusting to conditions that are optimal for survival
What are the 4 elements that make up the homeostasis process?
Imbalance
Receptor
Control Centre
Effector
What are the 4 categories of chemical signaling in multi-cellular organisms?
1) Autocrine
2) Signalling across gap junctions
3) Paracrine
4) Endocrine
What is the autocrine system of chemical signalling?
Part of the human immune response where molecules act on the same cells that produce them
What is the ‘signalling across gap junctions’ system of chemical signalling?
A cell that targets cells connected via a junction like with muscles
What is the paracrine system of chemical signalling?
A cell that signals to a nearby cell like tissues and nerve cells do
What is the endocrine system of chemical signalling?
When a cell targets a distant cell via the bloodstream such as the thyroid
What system does glucose control fall in?
Endocrine - negative
Where is glucose stored?
The liver
What is glucose stored as in the liver?
As Glycogen
What is Glycogenesis?
The formation of glycogen from glucose. It occurs depending on glucose and ATP (adenosine triphosphate) demand. When blood sugar is high, insulin promotes the glucose conversion into glycogen for storage in the liver and muscle cells
What is Glycogen?
What glucose is stored as in the liver
What pancreatic hormone will cause an increase in blood sugar?
Glucagon
What is glucagon?
A pancreatic hormone that increases blood sugar levels
What is glucose converted into to be used by cells?
ATP
What is Glycogenlysis?
Glucose-6-phosphate converted to glucose for distribution in blood to various cells e.g. the brain. It breaks down glycogen into glucose when blood sugar levels are low.
What hormones control glycogenlysis?
Glucagon and epinephrine
What is glyconeogensis?
The synthesis of glucose from non-carb sources
Where does glyconeogensis occur?
Mainly in the liver but some occurs in the kidney
When does glyconeogensis occur?
When blood glucose is low
When does glycogenesis occur?
When blood sugar is too high
When does glycogenlysis occur?
When blood sugar levels are too low
Alpha, Beta and Delta cells in the pancreas make up the what?
Islet of Langerhan
What is another name for alpha, beta and delta cells?
Glucagon, Insulin, Somatostatin
What does glucagon/alpha cells do?
Releases the hormone glucagon that converts glycogen back into glucose
What does Insulin/Beta cells do?
Detect the excess of glucose and release insulin to reduce blood sugar levels
What do delta/Somatostatin cells do?
Release somatostatin to inhibit insulin and glucagon
What is an example of a negative endocrine feedback loop?
Blood calcium levels
How does the blood calcium level cycle work?
1) Circulating blood decreases which is sensed by the parathyroid glands
2) Parathyroid glands express calcium which increases secretion of parathyroid hormone.
3) The parathyroid hormone enters the blood and goes to 3 distant cells.
4) Calcium absorption is increased in the bones and is decreased by the bones reservoir
Why is calcium needed?
Essential for nerve and muscle functioning.
What is a symptom of low calcium in the heart?
Dysrhythmias
What is an example of a positive endocrine system?
Childbirth and blood clotting. In positive systems the release of a hormone initiates additional release of the same hormone. This only is a good thing when there is a natural end-point.
What is the baroreceptor reflex?
The process of keeping blood pressure within the normal range
What are baroreceptors and where are they?
They’re blood pressure receptors in the aortic arch and internal carotid artery.
