Chapter 17 - The Endocrine System Flashcards
Endocrinology
The study of hormones and endocrine glands
Endocrine System Overview
Series of ductless glands that secrete hormones
Hormones travel to regions of the body and signal physiological responses
Cooperates with nervous system
-nervous = faster activity
-endocrine = slower response but effect usually lasts longer
Endocrine organs and hormones = system
Exocrine
Have ducts Secrete onto body surface or into cavity Secretions travel directly onto target Secretions are usually fluids, lubricants, enzymes ex. sweat, salivary, mucous
Endocrine Glands
DUCTLESS
Secrete hormones
Function is regulation, homeostasis
Hormones dumped right into bloodstream, act on target cells
Endocrine Organs Classifications
Pure Endocrine organs
Endocrine organs belonging to other body systems
Other
Pure endocrine organs
Pituitary gland Pineal gland Thyroid gland Parathyroid glands Adrenal gland
Endocrine organs belonging to other body systems
Pancreas
Thymus
Gonads
Hypothalamus
Other Endocrine organs
Organs that can also secrete hormones
Heart
Digestive Tract
Hormone classes
Amino acid (protein) Steroid (lipid)
Hormone Action
Circulate through bloodstream and affect only the target cells (have receptors)
Hormones themselves are just triggers
How hormones control secretion
Humoral stimuli
Neural stimuli
Hormonal stimuli
Feedback loops (Negative and Positive)
Humoral Stimuli
Respond to changing levels of ions/nutrients in blood
ex. parathyroid gland
Neural stimuli
Respond to nervous system
ex. adrenal medlla
Hormonal stimuli
Respond to hormones from other glands
ex. hypothalamus
Negative Feedback loop
More hormone secreted if levels drop
Positive Feedback loop
More hormone secreted if levels increase
Pituitary Gland (hypophysis)
9 major hormones, from 2 different portions all are protein hormones
Small, round structure
Hangs on stalk below hypothalamus; stalk is called infundibulum
2 separate glands, anterior (adenohypophysis) and posterior (neurohypophysis)
-Adnohypophysis is controlled by hypothalamus, which secretes peptide hormones (releasing factors) that signal the hormone release (inhibiting factors can also be released).
The hypothalamus controls the adenohypophysis, which controls the thyroid gland, adrenal cortex, and gonads
Adenohypophysis
Anterior pituitary gland, ventral portion under hypothalamus
Secrete: hormones that regulate growth and secretion of other glands, tissues (called TROPIC hormones/stimulating hormones)
ex. GH, MSH, FSH, LH, TSH, ACTH, Prolactin
Target: other endocrine glands (thyroid, adrenal, gonads)
The hypothalamus controls the adenohypophysis, which controls the thyroid gland, adrenal cortex, and gonads
Effect: Generally stimulates tissue growth and gland secretion, essential for growth, development, maturation
Growth Hormone (GH)
Regulates growth of all body cells, promotes cell division
Melanocyte stimulating hormone (MSH)
Causes darkening of skin by stimulating melanin
Follicle Stimulating Hormone (FSH)
In females, it regulates monthly development of follicle and egg and secretion of estrogen
In males, it stimulates testes to create sperm
Luteinizing hormone (LH)
Works together with FSH
In females, helps bring about ovulation, formation of progesterone
In males, it stimulates testosterone development and secretion
Thyroid stimulating hormone (TSH; thyrotropin)
Regulates thyroid gland, but hypothalamus also partially controls
Adrenocorticotropic hormone (ACTH)
Promotes functioning of adrenal cortex
Prolactin
Secreted in both males and females, but functions more in females after birth-responsible for milk production
Neurohypophysis
Posterior pituitary gland; dorsal, is considered part of the brain - has nervous tissue
Secretes: ADH & Oxytocin
ADH
Antidiuretic hormone, or vasopressin
Kidney = helps to retain water (decrease urine flow)
Blood vessels = constricts (increases BP)
Oxytocin
Uterus = contractions, delivery Breasts = lactation
Thyroid Gland
Locations: In the anterior neck, inferior to the larynx - just below Adam’s apple; wraps around front of trachea, has 2 lobes connected by the isthmus - many blood vessels around it
Secretions: TH (T4 & T3), & Calcitonin
Targets: almost all body tissues
Effects: Increase metabolic rate, stimulate protein synthesis
Thyroid Hormone
T3 = Thyroxine
T4 = Triiodothyronine
Peptide hormone which contains iodine, needed for function
NOTE: Pituitary gland releases TSH, which signals release of TH
Calcitonin
Targets bones
Retains calcium, inhibits osteoclasts (decreases blood calcium, keeps calcium in bones)
Parathyroid glands
Location: 4 tiny glands at top and bottom of posterior surface of each lobe of the thyroid gland (superior and inferior pair on each lateral lobe of thyroid)
Secretion: parathyroid hormone (PTH)
Targets:
bone: increase calcium release & increase osteoclast activity - opposite the effect of calcitonin
small intestine: increases Ca absorp
kidneys: decreases Ca excretion
NET EFFECT: Increases calcium in bloodstream, decreases amount in bones
Parathyroid hormone (PTH)
Protein hormone made by chief cells
Net effect of parathyroid glands
Increase Ca in bloodstream
Decrease Ca in bones
Adrenal glands (2 parts)
Adrenal cortex
Adrenal medulla
Adrenal cortex
bulk of adrenal gland, controlled by ACTH from anterior aituitary
Secretes over 30 hormones called corticosteroids
Location: cortex (outer portion)
Secretes: mineralocorticoids & glucocorticoids (steroid hormones)
Targets: cortisol targets liver, muscles (inc glucose metabolism), aldosterone targets kidney (inc Na retention, water follows - thus inc blood volume)
Mineralocorticoids
aldosterone
Glucocorticoids
cortisol
Adrenal medulla
Controlled by sympathetic nervous system
Location: inside portion of gland
Secrete: epinephrine and NE (catecholamines)
Target: all sympathetic mass activation, hormonal effect lasts longer (10X longer) - fight or flight response
Pineal Gland
Shaped like a pine cone
Function not well understood in humans
Location: roof of 3rd ventricle, dorsal to thalamus, dorsal/superior to midbrain (basically is straight back from the eyes)
Secrete: melatonin (NOT MELANIN)
Target: hypothalamus
Effect: Helps regulate circadian rhythms, sleep (inc secretion in dark)
Pancreas
Is BOTH an endocrine and exocrine gland
Location: posterior abdominal wall, middle-left side (stomach is superior to it, transverse colon is inferior to it, kidneys are dorsal to it)
Secrete (protein hormones): Pancreatic islets, glucagon, insulin
Target: glucagon signals liver to release glucose from stored glycogen; insulin signals liver to store glucose as glycogen
Pancreatic islets
Islets of Langerhans
Responsible for endocrine function
-2 types: alpha and beta
Glucagon
Helps to release fuel into bloodstream
Comes from alpha islet cells
Insulin
Helps to store glucose/fuel (decreases the amount in bloodstream)
Comes from beta islet cells
THUS insulin is released in a HYPERglycemic state and has a HYPOglycemic effect
Thymus
Location: farther down trachea from thyroid, rests on top of pericardial sac in the mediastinum (base of neck) - in front of aorta, behind sternum
Secrete: Thymic hormone
Target: lymphoid tissues (especially nodes)
Effect: Increase lymphocyte production, especially T cells - helps maintain immunity - gland is much larger in children, regresses in size after puberty
Thymic hormone
Thymosin & Thymopoietin
Peptide hormone
Gonads (male and female)
testes & ovaries
BOTH sex steroid groups are produced in BOTH sexes
Ovaries
Location: upper pelvic cavity, one on each side of the uterus, oval-shaped
Secrete: not purely endocrine gland - also produces eggs cells ,estrogen, progesterone (steroids)
Estrogen
steroid
Targets: most body tissues
Effects: growth & development, sex drive
Progesterone
Steroid
Target: uterus
Effect: endometrial proliferation in pregnancy (prep uterus for implantation)
Testes
Location: scrotum
Secrete: androgens (steroids; primarily testosterone)
Not purely endocrine - produces sperm
Target: Most body tissue
Effect: growth and development, sex drive
Heart
ANP (atrial natriuretic peptide)
decreases excess blood volume, high BP, and high Na concentration
Stimulates kidney to increase salt secretion
GI Tract
Stomach and Intestines
Gastrin, Secretin, CCK, GIP
Target/effect: secretions and activity of GI Tract
Gastrin
Release by stomach
Stimulates HCl
Secretin
Released by small intestine
Stimulates water and bicarbonate secretion in pancreatic juice
CCK
cholecystokinin
Released by small intestine
Stimulates gallbladder, pancreatic juices
GIP
Gastroinhibitory peptide
Released by small intestine
Inhibits gastric emptying, acid secretion
Placenta
Influences pregnancy
Kidneys
Secrete erythropoietin
Target/effect: red bone marrow, stimulates RBC production
Skin
Precursor to vitamin D is produced by modified cholesterol molecules after exposure to UV light (Vitamin D is fully activated by liver), signals calcium absorption from small intestine (needed for bones)
Pituitary Endocrine System Disorders
Gigantism
Acromegaly
Gigantism
Tumor causes hypersecretion of GH in children (extreme tallness)
Acromegaly
Excessive GH secretion after epiphyseal growth plates fuse
Enlargement of hands, feet, face
pancreas endocrine system disorders
Diabetes mellitus
Diabetes mellitus
Insufficient insulin OR inability of cells to react to insulin (blood sugar is high)
Type 1: need insulin injected
Type 2: “adult onset” reduced insulin sensitivity
Thyroid Endocrine System Disorders
Graves’ disease
Hypothyroidism
Goiter
Graves’ disease
Oversecretion of thyroid hormone (elevated metabolic rate, rapid HR, sweating, etc)
Hypothyroidism
Hyposecretion of thyroid hormone (low metabolic rate, weight gain, lethargy, etc)
Goiter
Enlarged thyroid gland due to lack of iodine.
