endocrine system Flashcards
what are the 2 types of endocrine glands
exocrine: secrete into a duct that carries secretion to body surface/cavity e.g. sweat glands, salivary glands
endocrine: secretes hormones into extracellular fluid surrounding cell which make up the gland. secretion passes into capillaries and transported by blood
e.g. hypothalamus, pituitary gland, adrenal glands
explain what hormones are
secretion of endocrine glands
travel through blood
affect either all cells, target cells or target organs
only able to influence a cell if cell has a specific receptor
saturation can occur
hormones may:
- activate certain genes in the nucleus
- change the rate of production of enzyme/protein
- change shape or structure of an enzyme
what is enzyme amplification
when one hormones activates thousands of enzymes through a chain reaction that amplifies at each stage
list the 3 types of hormones
protein and amine hormones
steroid hormones
hormone receptor complex
what is a protein and amine hormone
Attach to receptor molecules in the cell membrane
This starts a chain resulting in a secondary messenger substance
This diffuse through the cell and activates particular enzymes
what is a steroid hormone
Fat soluble
Diffuse through bi-lipid membrane and combine with a receptor inside the cell
what is a hormone receptor complex
Activates the genes controlling the formation of particular proteins
explain the structure and function of the pituitary gland
lies under hypothalamus, joined to it by a stalk - infundibulum
has anterior and posterior lobes
anterior lobe has a network of capillaries and no nerves connecting it to hypothalamus
connected to hypothalamus by nerve fibres
hormones produced in hypothalamus are carried by blood to anterior lobe - this stimulates release of hormones made in anterior
other hormones pass along nerve fibres to posterior lobe where they’re then secreted
what hormones are released in the anterior lobe of the pituitary
thyroid stimulating hormone (TSH): stimulates production and release of hormones from the thyroid gland
adrenocorticotropic hormone (ACTH): controls production and release of some hormones from the cortex of the adrenal glands
what hormones are secreted from the posterior lobe of the pituitary
Antidiuretic hormone: causes nephrons to remove water from filtrate and return it to the bloodstream, therefore retains fluid in the body
At higher concentration AHD can cause vasoconstriction of arterioles.
explain the structure and function of the thyroid gland
Located in the neck below the larynx
Consists of two lobes
Secretes thyroxine, constantly manufactures in the thyroid from iodine and an amino acid
• Thyroxine controls body metabolism
• Overall effect of thyroxine is to release of energy and
maintain body temperature
• Thyroxine is secreted as a response to TSH
explain the structure and function of the parathyroid gland
4 parathyroid glands each the size of a small pea
Embedded behind the thyroid gland
Secrete parathyroid hormone (PTH)
This increases calcium levels and decrease phosphate levels in the blood
explain the structure and function of the thymus
Secretes a group of hormones called thymosins
These influence the maturation of disease-fighting cells T lymphocytes
what are the adrenal glands
2 above each kidney
Each gland has an adrenal medulla and an outer adrenal cortex
what hormones does the adrenal medulla release
adrenaline: prepares body for reactions in threatening situations
noradrenaline: similar to adrenaline, increases rate and force of heartbeat
