Endocrine System Flashcards
What are the ways in which substances are secreted from endocrine and exocrine glands?
Endocrine: ductless, into the bloodstream
Exocrine: onto epithelial surfaces of ducts
What are the consequences of Sympathetic innervation?
Constriction of vessels (except capillaries - instead pre-capillary sphincters are controlled)
Dilation of airways
Vasoconstriction of the skin vessels
Venoconstriction (returns blood to the heart)
Prioritise blood to the brain, heart and skeletal muscle
What are the consequences of parasympathetic innervation?
Overpowers sympathetic innervation (reversing/reducing effects of sympathetic innervation)
Stimulates digestive activity in the intestines
Relaxation of rectum
Contraction of bladder
What organs are involved in neurocrine communication?
Hypothalamus
Posterior pituitary
Adrenal (medulla) glands
What is the difference between peptide hormones and steroid hormones?
PEPTIDE binds to peptide receptor, initiates secondary messengers and physiological response
STEROID binds to carrier protein which releases steroid intracellularly to bind to a receptor in the nucleus, affecting mRNA and formation of new proteins
What is the endocrine function of the thymus?
Secrete thymosin - promotes T-cell maturation
How does the hypothalamus communicate with the pituitary?
Posterior pituitary: Hormones are secreted into capillaries in the posterior pituitary via neurones in the pituitary stalk (travels from the hypothalamus to the posterior pituitary)
Anterior pituitary: Hormones are secreted into the capillaries in the hypothalo-hypophyseal portal system (travels from the hypothalamus to the anterior pituitary)
How is the thyroid hormone produced and activated?
TRH released by the hypothalamus causes the release of TSH from the anterior pituitary
TSH stimulates the pituitary to release T4 (Thyroxine)
T4 is activated by removal of an Iodine to T3 (Triidothreonine)
How are the concentrations of T3/T4 controlled?
Concentrations of T4/T3 control the release of TRH and therefore TSH and therefore T4/T3 (forming negative feedback loop)
What are the hormones secreted by the adrenal glands and their specific function?
Glucocorticoids: control glucose levels in the blood
Mineralocorticoids: control salt and water levels in the blood
Adrenaline (Nor-adrenaline): innervate adrenoreceptors
How are the long-term adrenal Hormones secreted?
CRH released by the hypothalamus causes the release of ACTH from the anterior pituitary
ACTH stimulates the pituitary to release glucocorticoids and mineralocorticoids
How are the short-term adrenal Hormones secreted?
Preganglionic sympathetic neurones synapse to chromaffin cells in the adrenal medulla
Impulses cause the release of the catecholamines (adrenaline and nor-adrenaline) from chromaffin cells
(chromaffin cells = postganglionic sympathetic neurones)
How are the hormones from the pineal gland secreted?
Light exposure inhibits the release of melatonin
Melatonin inhibits the gonatropins - LH, FSH
