Ch 11 Flashcards
Exocrine Glands
- secrete hormones into blood
- hormones carried to target cells, help regulate body metabolism, growth, and reproduction
- -> many organs secrete hormones
Neurohormones
secreted by specialized cells of hypothalamus
What are the chemical classifications of hormones?
amines
polypeptides/proteins
glycoproteins
steroids
Amines
*hormones
derived from tyrosine and tryptophan
–>ex. hormones from adrenal medulla, thyroid, and pineal glands
Polypeptides and Proteins
- hormones
- ->ex. antidiuretic hormone, insulin, and growth hormone
Glycoproteins
*hormones
long polypeptides bound to a carbohydrate
–>ex. follicle-stimulating and luteinizing hormones
Steroids
*hormones
lipids derived from cholesterol
-secreted by adrenal cortex and gonads
–>ex. testosterone, estradiol, progesterone, cortisol
Synergistic Effects
Occur when two or more hormones work together to produce a particular effect
- may be additive (ex. epinephrine and norepinephrine each affect part in same way_
- may be complementary: when each hormone contributes a different piece of an overall outcome (ex. producing milk requires estrogen, prolactin, and oxytocin)
Permissive Effects
Occur when one hormone makes the target cell more responsive to a second hormone
- ->exposure to estrogen makes the uterus more responsive to progesterone
- ->increase secretion of PTH makes the intestines more responsive to Vit D3 in calcium absorption
Antagonistic Effects
Occur when hormones work in OPPOSITE directions
- insuilin and glucagon both affect adipose tissue
- ->insulin stimulates fat storage
- ->glucagon stimulates fat breakdown
Hormone Action
Hormones bind to receptors on or in target cells
- binding is highly specific
- hormones bind to receptors with high affinity
- hormones bind to receptors with low capacity, saturating the receptors with hormone molecules
- Lipophilic hormone receptors are int he cytoplasm or nucleus
- water soluble hormone receptors are not he outer surface of the plasma membrane
Nuclear Receptors
Lipophilic steroid hormones and thyroid hormone:
- travel to target cells attached to carrier proteins
- at target cell, dissociate from carrier protein and diffuse across plasma membrane
- ->receptors are found within the nucleus and are called nuclear hormone receptors because they activate genetic transcription
- hormone receptors = transcription factors
- activated by bind of the hormone
- effect of these hormones therefore to produce new proteins, usually enzymes that change metabolism inside the cell
Hormones: 2nd Messengers
- hormones that can NOT cross the plasma membrane bind to receptors on cell surface
- activate an intracellular mediator called 2nd messenger
- three major 2nd messenger mechanisms
1. Adenylate Cyclase (activates a protein kinase)
2. Phospholipase C (controls intracellular Ca)
3. Tyrosine kinases
Pituitary Gland
- attached to hypothalamus by infundibulum
- divided into anterior lobe (adenohypophysis) and posterior lobe (neurohypophysis)
Anterior Pituitary
glandular epithelium with two parts - pars distills and pars tuberalis
Posterior Pituitary
nervous tissue and also called pars nervosa
Anterior Pituitary Hormones
Trophic hormones stimulate hormone secretion other glands:
- growth hormone (GH)
- Thyroid-stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH): in the male, it is interstitial cell stimulating hormone (ICSH)
- Prolactin (PRL)
Growth Hormone (GH)
*in most tissues
promotes protein synthesis and growth
Thyroid-Stimulating Hormone (TSH)
*in thyroid gland
stimulates secretion of thyroid hormone
Adrenocorticotrophic Hormone (ACTH)
*in adrenal cortex
stimulates secretion of glucocorticoids
Follicle-Stimulating Hormone (FSH)
*in gonads
promotes gamete production and stimulates estrogen production in females
Prolactin (PRL)
*in mammary glands
promotes milk production in lactating females
Luteinizing Hormone (LH)
*in gonads
stimulates sex hormone secretion, ovulation and corpus lute formation in female and testosterone secretion in males
Feedback Control of Anterior Pituitary
- final product regulates secretion of pituitary hormones (neg feedback inhibition)
- axis
- inhibition can occur at pituitary gland level: inhibiting response to hypothalamic hormones
- inhibition can occur at the hypothalamus level: inhibition secretion of releasing hormones
Axis
relationship between hypothalamus, anterior pituitary, and the target tissue
Posterior Pituitary Hormones
stores and releases two hormones mad win the hypothalamus
- Antidiuretic Hormone (ADH)
- Oxytocin
Antidiuretic Hormone (ADH)
*posterior pituitary hormone
promotes retention of water in kidneys (also called arginine vasopressin, AVP)
Oxytocin
*posterior pituitary hormone
stimulates contractions in childbirth and milk let-down in lactation
Adrenal Glands
- found atop the kidneys
- consist of an outer adrenal cortex + inner adrenal medulla that function as separate glands
Adrenal Medulla
neural tissue and secretes epinephrine and norepinephrine in response to sympathetic neural stimulation
Adrenal Cortex
glandular epithelium and secretes steroid hormones in response to ACTH
- three layers
- secretes hormones made from cholesterol, called corticosteroids or corticoids
- three categories
Three layers of adrenal cortex
- zona glomerulosa
- zona fasciculata
- zona reticularis
What are the three categories of the adrenal cortex?
- Mineralocorticoids: from the zone glomerulosa regulate Na+ and K+ balance.
- ->Ex. aldosterone - Glucocorticoids: from the zone fasciculate regulate glucose metabolism.
- ->Ex. cortisol - Adrenal androgens: from the zone reticular are weak sex hormones that supplement those made in the gonads.
Cortisol (Hydrocortisone)
- stimulates protein degradation
- stimulates gluconeogenesis and inhibits glucose utilization to raise blood glucose levels
- stimulates liplysis
Thyroid Gland
- located just below larynx
- has two lobes on either side of trachea, connected by isthmus
Thyroid Gland Structure
- thyroid follicles: hollow spaces, lines w/simple cuboidal epithelium composed of follicular cells that produce thyroglobulin
- interior of follicles is filled w/fluid called colloid
- outside of the follicles are parafollicular cells that secrete calcitonin
Production of Thyroid Hormone
-thyroglobulin is made by follicular cells
-thyroid follicles actively accumulate iodide and secrete into the colloid
• The iodine is attached to tyrosines within the thyroglobulin molecule.
• One iodine produces monoiodotyrosine (MIT).
• Two iodines produce diiodotyrosine (DIT).
• Enzymes within the colloid attach MIT and DIT together:
• DIT + DIT = T4 (tetraiodothyronine or thyroxine)
• DIT + MIT = T3 (triiodothyronine)
• These are still bound to thyroglobulin.
• They dissociate from thyroglobulin when the thyroid gland is
stimulated by TSH.
• Secreted into the blood
Thyroid Hormone
- T3 = active form, T4 can be converted to T23 by iodinates in cells
- stimulates protein synthesis
- promotes maturation of nervous system
- increases rates of cellular respiration
- elevates BMR
Hypothyroid
impaired growth lethargy dry skin slow pulse constipation depression etc
Hyperthyroid
accelerated growth increased activity excessive perspiration freq bowel movements rapid reflexes nervousness etc
Parathyroid Glands
- generally four glands embedded in back of thyroid gland
- secrete PTH
- hormone promotes a rise in blood Ca b acting on bones, kidneys, and intestine
Pancreas
both an endocrine and exocrine gland
- endocrine cells are located in pancreatic islets (islets of langerhans)
1. alpha cells: glucagon
2. beta cells: insulin
Insulin
- primary hormone regulation plasma glucose concentration
- secreted by beta cells when blood glucose levels rise after sugary/carbohydrate meal
- purpose to lower blood glucose to normal range
- binds to receptors on target cells
- indirectly stimulates the enzyme glycogen synthase in liver and skeletal muscles to promote sugar storage
- stimulates adipose tissue to store fat
Glucagon
- antagonistic to insulin
- secreted by alpha cells when blood glucose levels are low
- purpose is to raise blood glucose levels to normal range
- stimulates liver to hydrolyze glucagon into glucose (glycogenolysis) and release it into the blood
- stimulates gluconeogenesis: conversation of noncarbohydrate into glucose
- stimulates lipolysis: in adipose tissue so fat is released and used as fuel source instead of glucose
