Chapter 5- The Endocrine System Flashcards
Insulin
Favors the transport of glucose into organs as well as the storage of excess glucose when blood glucose concentrations are high
Glucagon
Triggers the release of sugar stored and raises blood glucose concentration
Organs of endocrine system
Glands (they release hormones)
Hormones
Signaling molecules that are secreted directly into the bloodstream to travel to a distant target tissue
Hormone classifications
- Peptides
- Steroids
- Amino acid derivatives
Peptide hormones
Bind to membrane-bound receptors to initiate a signal cascade, using secondary messengers (cAMP, IP3, and calcium). Effects are usually rapid and short-lived. Peptides are water soluble so they can just flow through the blood stream
Adenylate Cyclase
Raising or lowering the levels of cAMP accordingly
Protein kinase A
Phosphorylates transcription factors like cAMP, it can modify other enzymes as well
Steroid hormone production
Derived from cholesterol (nonpolar, so can cross cell membrane) and are produced primarily by the gonads and adrenal cortex
Mechanism of steroid hormones
Bind to intracellular (in cytosol) receptors and function by binding to DNA to alter gene transcription. Slower and longer lasting change (ex: estrogen and testosterone)
Albumin
Nonspecific protein carrying steroid hormones (need to be taken cause not water soluble)
Amino acid derivative hormones
Derived from one or two amino acids with some modifications and include epinephrine norepinephrine and thyroxine
Catecholamines
Find 2G protein coupled receptors well Fairoyal hormones bind intracellularly examples are epinephrine and norepinephrine
Mechanism of epinephrine and norepinephrine
Extremely fast onset but are short-lived like peptide hormones think of an adrenaline rush
Mechanism of Thyroxine and triiodothyronine
Slower on set but longer duration like steroid hormones they regulate metabolic rate over a long period of time
Direct hormones
Secreted then asked directly on the target tissue for example insulin
Tropic hormones
Require intermediary to act, do not cause direct changes and physiology. stimulate the production of another hormone buy another endocrine gland that acts on these target tissues they typically originate in the brain and anterior pituitary gland
List of endocrine organs
H-TAG 4P (#4P)
Hypothalamus, thyroid, adrenal glands, gonads, pituitary, parathyroid, pancreas, pineal gland
Hypothalamus
Bridge between nervous and endocrine systems. regulates the pituitary gland through tropic hormones and paracrine release of hormones into a portal system that directly connects the two organs
interactions between hypothalamus and anterior pituitary gland
hypothalamus secretes hormones into the hypophyseal portal system (blood vessel system that directly connects the two) then stimulates release of other hormones from anterior pituitary
hypophysis
alternative term for pituitary
4 hormones released by hypothalamus to anterior pituitary
- Gonadotropin-releasing hormone (GnRH)
- Growth hormone-releasing hormone (GHRH)
- Thyroid-releasing hormone (TRH)
- Corticotropin-releasing factor (CRF)
if the hypothalamus releases Gonadotropin-releasing hormone (GnRH)… what does the anterior pituitary release?
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)– act on the gonads (testes and ovaries)
if the hypothalamus releases Growth hormone-releasing hormone (GHRH)… what does the anterior pituitary release?
growth hormone (GH)
if the hypothalamus releases Thyroid-releasing hormone (TRH)… what does the anterior pituitary release?
thyroid-stimulating hormone (TSH) which promotes the release of T3 and T4
if the hypothalamus releases Corticotropin-releasing factor (CRF)… what does the anterior pituitary release?
adrenocorticotropic hormone (ACTH) which then causes the adrenal cortex to increase cortisol levels in the blood. cortisol acts through negative feedback to prevent hypothalamus from releasing CRF and anterior pituitary from releasing ACTH.
Prolactin-Inhibiting factor (PIF)
it is dopamine. released by the hypothalamus and causes a decrease in prolactin secretion. it is the absence of PIF that allows for prolactin to be released.
interactions between hypothalamus and posterior pituitary
No tropic hormones through hypophyseal portal system. neurons in hypothalamus send axons down pituitary stalk directly into posterior pituitary. this can release oxytocin and antidiuretic hormone.