Endocrine System Flashcards
Exocrine glands
- secrete into a duct that carries the secretion to the body surface or to one of the body’s cavities
- eg. sweat glands, mucous glands, salivary glands, glands of the alimentary canal
Endocrine glands
- secrete hormones ino the extracellular fluid that surrounds the cells that make up the gland; usually carried by the blood
- ductless
- eg. pineal gland, thyroid gland, pancreas, testes, ovaries, adrenal gland, thymus, pituitary gland, hypothalamus
Hormones
- proteins, steriods, amines
- only able to influence cells that have the correct receptor
- can change the functioning of the cells by changin type, activities or quantities of proteins being produced
Protein and amine hormones
- attach to receptor proteins in the membrane of the target cell
- hormone and receptor cause a secondary messenger substance to diffuse through the cell and activate enzyme
- limited number of receptor proteins in each cell - can be no further increase in the rate of a cell’s reaction
Steroid hormones
- work by entering target cells and combining with a receptor inside the cell
- receptor MAY be in the mitochondria, on other organelles or nucleus
Hormones may…
- activate certain genes in the nucleus so that a particular enzyme or structural protein is produced
- change the shape or structure of an enzyme so that it is turned ‘on’ or ‘off’
- change the rate of production of an enzyme or structural protein by changing the rate of transcription or translation during protein production
Enzyme amplification
- a single hormone activates thousands of enzymes
- hormone triggers cascading effect
Hormone clearance
- breaking down ot the hormone molecules once it has produced the required effect
- occurs mostly in the liver and kidneys but also in target cells
- excreted in bile or urine
Control of hormone secretions
- negative feedback systems secrete the hormone that is the opposite of the stimulus that caused the secretion
Hypthalamus
- located at the base of the brain
- regulates basic functions of the body eg. Temperature, water balance and heart rate
- many functions are carried out through the pituitary gland
Pituitary gland
- lies just under hypothalamus (connected by a stalk; infundibulum)
- anterior and posterior love
- makes hormones that instruct other glands to produce hormones (regulate activity)
Anterior lobe of pituitary
- No nerves connecting it to hypothalamus but is connected by a network of blood cells
- releases a number of hormones that regulate a range of bodily activities
Hormones released by anterior lobe
- gonadotropins
• follicle stimulating hormone (FHS)
• luteinising hormone (LH) - growth hormone
- thyroid-stimulating hormone (TSH) or thyrotrophin
- adrenocorticotrophin (ACTH)
- prolactin (PRL) or lactogenic hormone
Gonadotropins
- hormones that affect the gonads, the ovaries and testes
Follicle Stimulating Hormone (FSH)
Female; stimulates development of the follicles that contain the egg
Male; production and maturation of sperm in testes
Luteinising hormone
Female; brings about ovulation and to form corpus luteum after ovulation
Male; stimulated interstitial cells in the testes to secrete male sex hormones
Growth hormone
- stimulates body growth (in particular the skeleton)
- increases the rate at which amino acids are taken up by the cells and built into proteins
Thyroid-stimulating hormone
Stimulate production and release of hormones from the thyroid gland
Adrenocorticotropic hormone
- controls production and release of some hormones from the cortex of the adrenal glands
Prolactin
- works with other hormones to initiate and maintain milk secretion in females
Posterior lobe of the pituitary gland
- not a true gland as it doesn’t secrete substances
- joined to the hypothalamus by nerve fibres
- releases the hormones oxytocin and antidiuretic hormone but neither are secreted here
- produced in nerve cells of the hypothalamus
Oxytocin
- stimulates contraction of the muscles of the uterus
- stimulates mammary glands (release of milk when breastfeeding)
Antidiuretic hormone
- because the kidneys to remove water from urine that is forming
- water returned to the bloodstream
- helps retain fluid within the body
Pineal gland
- secreted hormone melatonin; involves in regulation of sleep
- deep inside the brain
- decreases in size after puberty
Thyroid gland
- located in the neck
- two lobes that lie on either side of the trachea (joined by narrow piece of tissue)
- secreted thyroxine
Thyroxine
- made from iodine and an amino acid
- continually manufactured
- controls body metabolism by regulating reactions in the which complex molecules are synthesised from simple ones
- BRING ABOUT RELEASE OF ENERGY AND MAINTAIN BODY TEMPERATURE
- secreted in response to thyroid- stimulating hormone
Parathyroid glands
- rear surface of the lobes of the thyroid gland
- secrete parathyroid hormone; calcium and phosphate levels in the blood
