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Flashcards in endocrine Deck (25):


chemical signals that travel in blood or lymph and act at a distance


hormone action

can include:
- altering plasma membrane permeability of membrane potential by opening or closing ion channels
- stimulating synthesis of proteins or regulatory molecules
- activating or deactivate enzyme systems
- inducing secretory activity
- stimulating mitosis


hormone release (humoral stimuli)

- changing blood levels of ions and nutrients directly stimulates secretion of hormones


hormone release (neural stimuli)

- nerve fibres stimulate hormone release, such as when sympathetic fibres stimulate the adrenal gland to release adrenaline


hormone release (hormonal stimuli)

- hormones stimulate other endocrine organs to release their hormones
0 for example, hormones form the hypothalamus stimulate further release of other hormones from many endocrine glands


anterior pituitary gland

- receives signals from the hypothalamus by a series of blood vessels known as hypophyseal portal system
- these vessels carry releasing and inhibitory hormones down from the hypothalamus to the anterior pituitary to regulate its action
- anterior pituitary then produces and releases the hormones required


posterior pituitary gland

- directly receives hormones from the hypothalamus
- stores and releases hormones


anterior pituitary hormones

- Adrenocorticotropic hormone (ACTH) which acts on the cortex of the adrenal gland, prompts release of many hormones that play a role in stress, and glucose, water and salt balance
- Prolactin (PRL) stimulates milk production in the mammary glands
- Follicle-stimulating hormone (FSH) prompts the gonads to mature and release ova and sperm
- Lutenizing hormone (LH) prompts gonads to secrete sex hormones like oestrogen and testosterone


posterior pituitary hormones

- they are released in response to hypothalamic input
- Anti-diuretic hormone (ADH) conserves water and affects electrolyte balance, targets the kidney to decrease production and release of urine
- Oxytocin, targets smooth muscles (stimulates uterine contractions during childbirth, also triggers milk ejection in women producing milk


thyroid gland

- thyroid lies around the windpipe below the larynx
- composed with follicles of colloid thyroglobin and iodine
- colloid is the precursor of thyroid hormone


thyroid hormone

- 2 related hormones (T3 and T4)
- thyroid hormone release is regulated by negative feedback
- major metabolic hormone that increases metabolic rate and heat production
- also plays a role in maintenance of blood pressure, regulation of tissue growth, development of skeletal/nervous systems and reproductive capabilities



- triangular gland located inferior and posterior to the stomach in the abdominal cavity
- 99% exocrine in function
- important endocrine gland, referring to blood glucose levels, pancreatic islets



- major target is the liver, where it promotes
- glycogenolysis - breakdown of glycogen to glucose
- the release is stimulated by falling blood glucose and sympathetic stimulation, rising blood amino acid levels



- lowers blood glucose levels by the acceleration of glucose uptake and glucose metabolism
- stimulation of glycogen synthesis and conversiom of glucose to fat
- participates in neuronal development and leanring and memory
- release is stimulated by rising blood glucose


adrenal glands

- paired, pyrimid-shaped organs atop the kidneys


parathyroid and pineal glands

parathyroid - tiny glands embedded in posterior thyroid - produce the most important Ca balance hormone parathyroid hormone (PTH). it stimulates osteoclasts to digest bone matrix, enhances reabsorption of Ca2+ and secretion of phosphate by kidneys
pineal - small gland hanging from roof of third ventricle



- produce steroid sex hormones
- ovaries produce oestrogen and progesterone responsible for maturation of female reproductive organs, appearance of secondary sexual characteristics, breast development and cyclic changes
- testes produce testosterone responsible for maturation of male reproductive organs, sex drive, sperm production


other hormone producing structures

- heart, ANP (blood pressure, volume and Na+)
- gastrointestinal tract (hormones that locally effect digestive activity)
- skin, cholecalciferol (precursor of Vit D)
- adipose tissue, leptin (involved in appetite control and energy expenditure
- kidneys (erythropoiten signals production of red blood cells and Renin is involved in blood pressure
- thymus, organ in thorax (involved in development of immune cells and system)


growth hormone imbalances

- excessive secretion during childbirth (gigantism)
- excessive secretion during adulthood (acromegaly)
- reduced/inhibited secretion during development (pituitary dwarfism)


antidiuretic hormon ADH imbalances

- deficiency (Diabetes insipidus; huge output of urine and intense thirst)
- Hypersection (syndrome of inappropriate ADH secretion)


thyroid hormone imbalances

- hyposecretion in adults (myxoedema; endemic goiter if due to lack of iodine)
- hyposecretion in infants (cretinism)
- hypersecretion (Grave's Disease)


adrenal cortex glucocorticoids imbalances

- Hypersecretion (Cushing's syndrome) depression of inflammation, immunity, skeletal tissue
- Hyposecretion (Addison's disease) decrease in glucose and Na+ levels


insulin imbalances

- Diabetes
- type 1 = insulin dependant (hyposecretion or absence of insulin - problem with pancreas, potential genetic or immune deficiency)
- type 2 = non-insulin dependent (dificient effects or activity of insulin - often lifestyle related - insulin resistance)
- glucose concentrations exceed renal absorption due to inability to reduce blood sugar levels
- hyperinsulinism is excessive insulin secretion, results in hypoglycemia, disorientation or unconsciousness


parathyroid hormone (pth) imbalances

- hyperparathyroidism due to tumor (excessive Ca2+ resorbed - bones soften and deform, Elevated blood Ca2+ depresses nervous system and contributes to formation of kidney stones)
- Hypoparathyroidism following gland trauma or removal (results in tetany, respiratory paralysis and death)


neurons vs hormone

- transmit electrically
- use chemicals to pass on to next cell causing stimulation/inhibition
- immediate response time
- impulses sent quickly
- highly branched and connected
- blood-borne and can affect cells near and far
- response time can take seconds to years
- hughly regulated by negative feedback
- multiple modes of affecting cell metabolism