Ch 14 h Flashcards
(32 cards)
What is an Endocrine gland?
a group of cells specialised to secrete chemicals (hormones) directly into the bloodstream.
e.g. Pancreas and Adrenal glands
Pituitary gland
Endocrine gland at the base of brain
Makes Several Hormones; for Growth, balancing w.p. of blood (ADH), and Gonadotrophins (control development of ovaries and testies/reproduction)
controls functions of many other endocrine gland
What is an Exocrine gland?
a group of cells specialised to secrete chemicals/hormones through DUCTS into organs/ surface of the body.
e.g. Salivary or Sweat glands
What are hormones?
Chemical Messengers - carry info from one part of the body to another.
Hormones can be steroids, proteins, glycoproteins, polypeptides, amines, or tryosine derivatives.
What causes hormones to be Secreted?
Hormones are secreted when a gland is stimulated; e.g. as result of Change in Concentration of a particular Substance, or as a result of another Hormone or a Nerve Impulse.
Transport and initial Action of (endocrine) hormones?
Endocrine Hormones travel in the blood plasma all around the body. They Diffuse out the blood upon reaching their target organ, and bind to a specific receptor on their target cell’s membrane or cytoplam.
Once bound to receptor they stimulate the target cell to produce a response.
The Type of hormone determines its effect on a target cell:
Action of Steroid Hormones?
Steroid Hormones: lipid-soluble so pass through cell-surface membrane and binds to receptor in cytoplasm or nucleus, forming a hormone-receptor complex (acts as transcription factor which facilitates or inhibits transcription of specific gene). E.g. Oestrogen
The Type of hormone determines its effect on a target cell:
Action of Non-Steroid Hormones?
Non-Steroid hormones: Hydrophilic so bind to receptor on cell-surface membrane of target cell, triggering a cascade reaction, mediated by second-messengers. E.g. Adrenaline
Hormonal Vs Neuronal communication
Hormonal : Slower, less specific communication. Not broken down as quickly as neurotransmitters, so have longer lasting and widespread effect.
Adrenal glands:
Located on top of each kidney
Made of 2 parts; adrenal cortex + adrenal medulla, surrounded by a capsule.
What is the Adrenal Cortex?
Outer region of the glands.
Produces hormones vital to life, e.g. Cortisol & Aldosterone
What is the Adrenal Medulla?
Inner region of the glands
Produces Non-Essential hormones, e.g. Adrenaline
Types of Hormones produced by the Adrenal Cortex:
Glucocorticoids: release is controlled by the hypothalamus
e.g. Cortisol (helps regulate metabolism and blood pressure in response to stress) & Cortecosterone.
Mineralocorticoids: e.g. Aldosterone (control blood pressure by maintaining salt/water balance in blood) Its relase is triggered by the Kidney
Androgens: Small amounts of sex hormones, small impact yet important after the menopause.
Types of Hormones produced by the Adrenal Medulla:
released when sympathetic nervous system is stimulated (stress)
Adrenaline (increase HR & blood glucose conc)
Noradrenaline (increase HR & blood pressure)
Pancreas; Role as Exocrine Gland
Pancretic Acini Produces digestive enzymes and an alkaline fluid; Pancreatic Juice, secreted into ducts, then the duodenum
Amylases - break down starch
Proteases - breakdown protein (trypsin)
Lipases - break down lipids
Pancreas; Role as Endocrine Gland
Islets of langerhans = small regions of endocrine tissue responsible for producing Insulin and Glucagon, and secreting them dircetly into the bloodstream
Increase Blood Glucose by :
Eating foods high in Starch or Sucrose
Glyogenolysis
Gluconeogenesis (liver makes glucose from glycerol & amino acids)
Decrease Blood Glucose by:
Respiration
Glycogenesis (produce glycogen)
Role & Action of Insulin
produced by Beta cells of Islets of Langerhans if blood glucose concentration is too High.
binds to glycoprotein receptor on cell-surface membrane, causing glucose transport protein channels to open (change in tertiary structure) and allow glucose to enter (for respiration or storage as glycogen or fat)
Insulin Lowers blood glucose concentration by:
increasing rate of absorbtion of glucose by cells
increasing cellular respiration rate (increasing need)
Increasing rate of glycogenesis
increasing rate of glucose conversion to fat
Inhibit release of glucagon by a-cells
Role & Action of Glucagon
produced by Alpha cells of Islets of Langerhans if blood glucose levels are too Low.
Binds to glucagon receptors on liver and fat cells, causing glycagon to be broken down into glucose to be released into the blood
Glucagon Raises blood glucose concentration by:
Glycogenolysis
Reducing glucose uptake by liver cells
Increasing Gluconeogenesis - conversion of amino acids and glycerol into glucose in the liver
Control of Insulin Secretion :
by Beta Cells
at normal blood glucose levels, K+ channels in plasma membrane of B cells are open, so K+ ions diffuse out the cell. the inside of the cell is at a potential of -70mV
When glucose levels rise:
Glucose enters cell by glucose transporter and is metabolised in the mitochondria = ATP is produced.
ATP binds to ATP sensitive K+ channels, causing them to close.
K+ cant diffuse out the cell = p.d reduces to -30mV and Depolarisation occurs.
Depolarisation causes the Voltage-Gated Ca2+ ion channels to open = Ca2+ ions enter the cell, causing secretory vesicles containing Insulin to fuse with the cell-surface membrane and release Insulin by Exocytosis.
Type 1 Diabetes
(B cells) unable to produce Insulin Unknown Cause (autoimmune?), no prevention or cure Treatment with regular Insulin Injections after measuring blood glucose concentrations and calculating dosage required.
