Chapters 12 + 13 - homeostasis Flashcards
What is homeostasis?
The maintenance of constant internal conditions.
What is vasoconstriction?
The narrowing of blood vessels, to prevent blood flow to the skin surface, therefore reducing heat loss.
What is vasodilation?
The dilation of blood vessels to increase blood flow to the skin surface, increasing heat loss.
Which area of the brain is the coordinator for temperature control?
The hypothalamus.
what is the autonomic nervous system?
The part of the nervous system which supplies the muscles and glands that aren’t under our conscious control.
What is a hormone?
A molecule which is transported in the blood and acts as a chemical messenger. They are produced by various cells and glands that make up the endocrine system. Most of hormones found in a mammal are either proteins that bind to receptors (insulin) or steroids that penetrate the plasma membrane and activate genes (oestrogen and progesterone).
What is a second messenger?
A molecule found inside a cell which responds to the presence of a hormone outside the cell by activating a particular enzyme.
What are islets of Langerhans?
Small groups of cells found in the pancreas which are responsible for the secretion of hormones involved in the control of blood glucose.
What do alpha cells secrete?
Glucagon.
What do beta cells secrete?
Insulin.
What is insulin?
A hormone that is stimulated by a rise in blood glucose concentration. It increases absorption of glucose into cells and increases glycogenesis.
What is glucagon?
A hormone stimulated by a fall in blood glucose concentration, it increases glycogenolysis and gluconeogenesis.
What is glycogenolysis?
The conversion of glycogen to glucose.
What is glycogenesis?
The conversion of glucose to glycogen, mostly in the muscles and liver.
What is gluconeogenesis?
A biochemical process in which glucose is made from non-carbohydrates (amino acids and glycerol).
What is diabetes?
A condition in which the level of glucose in the blood cannot be properly controlled.
What is type I diabetes?
Insulin dependent - pancreas fails to secrete enough insulin to control the blood glucose level.
What is type II diabetes?
Insulin independent - usually affects older people where they continue to produce insulin but it is no longer effective, so cells fail to take up glucose.
What is negative feedback?
A series of changes that result in a substance being restored to its normal level.
What is positive feedback?
Process which results in a substance that departs from its normal level becoming further from the norm.
What is FSH?
Follicle stimulating hormone - hormone produced by the pituitary gland, which stimulates immature follicles to develop.
What is LH?
Luteinising hormone - a hormone produced by the pituitary gland, which stimulates ovulation and causes follicle cells which remain in the ovary to develop into a corpus luteum, these then secrete progesterone.
What is oestrogen?
A female sex hormone produced by cells in the ovary. It brings about the lining of the uterus which becomes thicker and has a negative feedback on FSH.
What is progesterone?
A female sex hormone secreted by the corpus luteum. It maintains the lining of the uterus and has negative feedback on FSH and LH.
