Endocrine System Flashcards
Homeostasis
Maintaining a constant internal environment, despite changes in the external environment
Carried out by both endocrine and nervous system
Feedback Systems
The body responds to a stimulus, and the response alters the original stimulus
Homeostasis’ impact on fluid environment of cells
- optimum nutrients, ions, gases, and water
- constant temperature
- optimum pressure
Stages in a feedback system
- stimulus
- receptor
- modulator
- effector
- response
- feedback
Endocrine gland
secretes substance into the bloodstream eg. hormones
Exocrine gland
secretes substances onto a surface through a duct
Hormones
secreted from an endocrine gland, transported by blood, affects target cells/organs, specific as they bind to certain receptors
Paracrines
“local hormones”; chemicals secreted by all cells, used to communicate with adjacent cells
Protein and amine hormones
attach to receptors on the cell membrane, causes secondary messengers to activate cellular enzymes
Steroid hormones
attach to internal receptors on organelles, activates genes that control protein production (hormone-receptor complex)
Functions of hormones
activate genes to produce enzymes or proteins, denature enzymes, change rate of enzyme or protein production
Enzyme amplification
one hormone molecule can activate thousands of enzyme molecules - only a small amount of hormones are needed
Removal of hormones
target cells, liver, kidney
Releasing/inhibiting factors
produced by nervous system to trigger hormone production by endocrine glands (anterior pituitary)
Hypothalamus
Regulates body temp, water balance, heart rate
Pituitary gland
joined to the hypothalamus by the infundibulum; secretes hormones that regulate activity of endocrine glands
Anterior pituitary
adenohypophysis
connected to hypothalamus by blood vessels; inhibiting and releasing factors secreted by hypothalamus trigger production of of hormones
Posterior pituitary
neurohypophysis
Hormones pass from the hypothalamus to posterior pituitary through nerve impulses
Hormones secreted by anterior pituitary
gonadotrophins, growth hormone, thyroid stimulating hormone, adrenocorticotrophic hormone, prolactin
Hormones secreted by posterior pituitary
releases oxytocin, antidiuretic hormone
Thyroid gland
produces thyroxine, calcitonin
Effects of thyroxine
regulates metabolic rate by regulating energy production from cell respiration - increases body temperature
Calcitonin
promotes storage of calcium in the bones, reducing blood calcium levels
Pancreas
both exocrine and endocrine; secretes digestive enzymes, insulin, glucagon
Effects of insulin
Reduces blood glucose levels, stimulates cells to take up glucose and store it as glycogen or fat
Effects of glucagon
Increases blood glucose levels by stimulating breakdown of glycogen and fat from cells into glucose
Gonads
antrogens, oestrogen and progesterone
Adrenal medulla
(middle) secretes adrenalin and noradrenaline
Adrenal cortex
produces corticosteroids - mineralocorticoids, glucorticoids, gonadocorticoids
Effects of mineralocorticoids
main mineralocorticoid - aldosterone; retains sodium, removes potassium from body
Effects of glucocorticoids
Required for normal metabolism; increase in ATP production, blood pressure, decreased immune response, depressed inflammatory response, slower healing. Low doses provide resistance to stress, high doses depress the immune system
Parathyroids
produces parathormones
Effects of parathormones
increases blood calcium and phosphate levels
Thymus
decreases in size as child matures, secretes thymosins; maturations of T lymphocytes
