FINALS: ENDOCRINE SYSTEM Flashcards
▪ Second messenger system of the body
▪ Uses chemical messages (hormones) that are released into the blood
▪ Consists of ductless glands that secrete
hormones into the interstitial blood
Endocrine System
Hormones control several major processes:
o Reproduction
o Growth and development
o Mobilization of much of homeostasis
o Regulation of metabolism
▪ Comes from a Greek word meaning “to arouse”
▪ Produced by specialized cells (secrete hormones
into extracellular fluids)
▪ Blood transfers them to target sites
▪ They regulate the activity of other cells
HORMONES
Chemical classification of hormones:
(proteins, peptides, amines)
Amino acid-based hormones
Chemical classification of hormones:
(cholesterol)
Steroids
Chemical classification of hormones:
(highly active lipids)
Prostaglandins
TYPES OF HORMONE ACTION:
- is secreted in one location (ducts)
and released into BLOOD circulation.
Endocrine
TYPES OF HORMONE ACTION:
- is secreted in endocrine cells and
released into INTERSTITIAL SPACE.
Paracrine
TYPES OF HORMONE ACTION:
- is secreted in endocrine cells and
sometimes released into interstitial space; binds to specific receptor on cell of origin resulting to SELF-REGULATION of its function.
Autocrine
TYPES OF HORMONE ACTION:
- is secreted in endocrine cells and
remains in relation to the plasma membrane; acts on immediately adjacent cells by direct cell-to-cell contact.
Juxtacrine
TYPES OF HORMONE ACTION:
- is secreted in endocrine cells and
released into the LUMEN OF GUT
Exocrine
TYPES OF HORMONE ACTION:
- is secreted in the NEURONS and released from nerve endings; interacts with receptors of cells at distant site.
Neuroendocrine
MECHANISM OF HORMONE ACTION
▪ Effects caused by hormones:
o Changes in plasma membrane permeability/electrical state
o Synthesis of proteins, such as enzymes
o Activation/inactivation of enzymes
o Stimulation of mitosis
o Promotion of secretory activity
a. Direct Gene Activation: Steroid Hormone
Mechanism
- DIFFUSE THROUGH THE PLASMA MEMBRANE of
target cells - ENTER THE NUCLEUS
- BIND TO A SPECIFIC PROTEIN within the nucleus
- BIND TO A SPECIFIC SITES on the cell’s DNA
- ACTIVATE GENES that result in synthesis of newproteins
Second-Messenger System: Nonsteroid
Hormone Mechanism
- Hormone binds to a membrane receptor & it
does not enter the cell - Sets off a series of reactions that activates an enzyme catalyzing a reaction that produces a
second messenger molecule - Oversees additional intracellular changes to
promote a specific response
WHAT TYPE OF STIMULUS?
- endocrine glands are activated by other hormones
HORMONAL STIMULUS
WHAT TYPE OF STIMULUS?
- changing blood levels of certain ions stimulate hormone release
HUMORAL STIMULUS
WHAT TYPE OF STIMULUS?
- nerve impulse stimulate hormone release
NEURAL STIMULUS
▪ “Master endocrine gland”, stimulating
hormones
▪ Approximately the size of a pea
- Hangs by a stalk from the hypothalamus
▪ Protected by the sphenoid bone
PITUITARY GLAND (HYPOPHYSIS)
PITUITARY GLAND 2 FUNCTIONAL LOBES:
- AKA adenohypophysis, 3 parts are derived
embryonically from the hypophyseal pouch
Anterior pituitary (glandular tissue)
Anterior pituitary (glandular tissue)
❖ Accounts for 75% of the adenohypophysis and has a thin fibrous capsule
❖ Main components are cords of well-stained endocrine cells interspersed with fenestrated capillaries and supporting reticular connective tissue
A Pars tuberalis
B Pars intermedia
C Pars distalis
Pars distalis
Anterior pituitary (glandular tissue)
❖ A smaller FUNNEL-SHAPED region surrounding the infundibulum of the neurohypophysis
❖ Most of the cells are
gonadotrophs (synthesize &
secrete luteinizing hormone [LH] & follicle-stimulating hormone
[FSH])
A Pars tuberalis
B Pars intermedia
C Pars distalis
Pars tuberalis
Anterior pituitary (glandular tissue)
❖ A NARROW ZONE lying between the pars distalis and the pars nervosa
❖ Contains basophils
(corticotrophs: releases
adrenocorticotropic hormone [ACTH]), chromophobes, and small, colloid-filled cysts
A Pars tuberalis
B Pars intermedia
C Pars distalis
Pars intermedia
PITUITARY GLAND 2 FUNCTIONAL LOBES:
- AKA neurohypophysis
o Not an endocrine gland, acts only as a
STORAGE area for hormones made by
hypothalamic neurons
o Retains many histologic features of brain tissue and consists of a large part, the pars nervosa, and the smaller infundibulum stalk attached to the hypothalamus
Posterior pituitary (nervous tissue)
▪ Neuroendocrine organ because aside from
neural functions, it also produces and releases hormones
▪ Hormonal release of the anterior pituitary is
controlled by releasing hormone & inhibiting
hormones produced by hypothalamus
HYPOTHALAMUS
▪ Thyroid hormone secretion is regulated by
hormones from the hypothalamus & pituitary gland:
o Hypothalamus secretes TSH-releasing
hormones or TRH (travels to the anterior pituitary & stimulates the secretion of thyroid stimulating hormone)
o TSH: stimulates the secretion of thyroid hormones from the thyroid gland.
▪ Thyroid hormones have negative feedback
effect on the hypothalamus & pituitary.
o Loss of negative feedback results in excess TSH to be secreted, which causes
the thyroid gland to enlarge resulting in a
condition (goiter)
▪ Thyroid gland requires iodine to synthesize
thyroid hormones, which will be taken up by the thyroid follicles.
THYROID GLAND
thyroid hormone with 4 iodine atoms
Thyroxine
thyroid hormone that contains 3 iodine atoms
Triiodothyronine
▪ Tiny masses on the posterior of the thyroid
▪ Chief cells secrete parathyroid hormone
(chemical class: peptide)
o Stimulate osteoclasts to remove calcium
from bone
o Stimulate the kidneys & intestine to
absorb more calcium
o Raise calcium levels in the blood
PARATHYROID GLANDS
ADRENAL GLAND:
- outer glandular region; produces 3 major groups of steroid hormones (corticosteroids)
- has 3 concentric zones
- ❖ Zona glomerulosa:
mineralocorticoids (ALDOSTERONE)
- ❖ Zona fasciculata:
glucocorticoids (CORTISOL)
- ❖ Zona reticularis: androgens
CORTEX
ADRENAL GLAND:
- inner neural tissue region; produces catecholamines→ EPINEPHRINE (AKA adrenaline, principal hormone) & NOREPINEPHRINE (AKA noradrenaline, released in small amounts)
➢ Both hormones are released in response to stimulation by the sympathetic nervous system (fight-or-flight hormones)
Medulla:
a mixed gland & flattened organ that measures about 12.5–15 cm (5–6 in.) in
length, located in the curve of the duodenum
Pancreas
o Chemical class: protein
o Little masses of hormone-producing tissue scattered among the enzyme- producing acinar tissue of the pancreas
CELL TYPES:
o Alpha (A) cells
o Beta (B) cells
o Delta (D) cells
o F cells
Pancreatic islets (islet of Langerhans)
Pancreatic islets (islet of Langerhans) CELL TYPES:
- 17% of pancreatic islet
cells & secrete GLUCAGON
Alpha (A) cells
Pancreatic islets (islet of Langerhans) CELL TYPES:
- 70% of pancreatic islet
cells & secrete INSULIN
Beta (B) cells
Pancreatic islets (islet of Langerhans) CELL TYPES:
- 7% of pancreatic islet
cells & secrete SOMATOSTATIN
Delta (D) cells
Pancreatic islets (islet of Langerhans) CELL TYPES:
- 6% of pancreatic islet cells & secrete PANCREATIC POLYPEPTIDE
F cells
Acts on several tissues to cause entry of glucose into cells and promotes DECREASE of BLOOD GLUCOSE content
INSULIN
Acts on several tissues to make energy stored in glycogen and fat available through glycogenolysis and lipolysis; INCREASES BLOOD GLUCOSE content
GLUCAGON
Inhibits release of other
islet cell hormones through local paracrine action; inhibits release of GH and TSH in anterior pituitary and HCl secretion by gastric parietal cells
SOMATOSTATIN
Stimulates activity of gastric chief cells; inhibits bile secretion, pancreatic enzyme and
bicarbonate secretion, and intestinal motility
PANCREATIC POLYPEPTIDE
▪ A small, cone-shaped gland found hanging
from the roof of the 3rd ventricle of the brain;
located superior & posterior to the thalamus of the brain
▪ Secretes MELATONIN
o Chemical class: AMINE
o Contribute to the setting of the body’s
biological clock
o Peak levels is at night & lowest levels is
during daylight (noon)
o May have other as-yet-unsubstantiated
functions
PINEAL GLAND
▪ Located posterior to the sternum, between the lungs
▪ Largest in infants & children
▪ Produces THYMOSIN
o Chemical class: PEPTIDE
o Promotes maturation of some types of WBCs
o May retard aging process
o Important in developing the immune system
THYMUS GLAND
Produce sex cells and sex hormones that are identical to those produced by adrenal cortex cells: ovaries &
testes
GONADS
Stimulates corpus luteum in ovary to continue production of estrogens & progesterone to
maintain pregnancy
Human chorionic
gonadotropin (hCG)
Maintain pregnancy; help prepare mammary glands to secrete milk
Estrogen & progesterone
Works cooperatively with estrogen & progesterone in preparing the breasts for lactation
Human placental
lactogen (hPL)
Causes the mother’s pelvic ligaments & the pubic symphysis to relax & become more flexible, which eases birth passage
Relaxin
DISORDERS OF THE ENDOCRINE SYSTEM:
▪ Most common abnormality associated with dysfunction of the posterior pituitary
▪ Excessive urine output due to HYPOSECRETION
OF ADH
▪ Person is continually thirsty & drink huge amounts of water
Diabetes insipidus (DI)
hyposecretion of ADH, usually caused by a BRAIN TUMOR, head trauma, or brain surgery that damages the posterior pituitary or the hypothalamus
Neurogenic DI
the KIDNEYS DO NOT RESPOND to ADH & the ADH receptors may be
nonfunctional, or the kidneys may be
damaged
Nephrogenic DI
▪ Hyposecretion of GH during childhood slows
bone growth, & the epiphyseal plates close
before normal height is reached
Pituitary dwarfism
▪ Hypersecretion of GH during childhood, an
abnormal increase in the length of long bones
Gigantism
hypersecretion of GH occurs after long-bone growth has ended
Acromegaly
▪ Hyposecretion of FSH or LH in both males and
females
Sterility
▪ Enlargement of thyroid gland that results when
the diet is deficient in iodine
Goiter
▪ Congenital hypothyroidism
▪ Hyposecretion of thyroid hormones that is present at birth, causes severe mental
retardation & stunted bone growth
▪ Screening Test: low T4
▪ Confirmatory Test: high TSH
Cretinism
▪ SEVERE FORM of primary hypothyroidism
occurring in adults
▪ Occurs 5x more often in females
▪ Hallmark: EDEMA
▪ Other symptoms: low metabolic rate; feeling
chilled; constipation; thick, dry skin and puffy
eyes; lethargy; and mental sluggishness
▪ A goiter occurs if myxedema results from lack of iodine
Myxedema (mucous swelling)
▪ Most common form of hyperthyroidism
▪ Primary hyperthyroidism
▪ Autoimmune disorder in which the person produces antibodies that mimic the action of
TSH
▪ Enlarged thyroid & exophthalmos (protruding eyes)
▪ Most common cause of thyrotoxicosis (an
excess of thyroid hormone in the body, having this condition simply means you have a LOW LEVEL of TSH)
▪ Antibody present: Anti-TSH receptor
▪ Symptoms: elevated metabolic rate, sweating, rapid and irregular heartbeat, nervousness, goiter (sometimes), and exophthalmos (bulging of the eyes)
▪ Treatment: surgically removing thyroid gland
or ingesting radioactive iodine (131-I) which
destroys the most active thyroid cells
Graves’ disease
▪TOO LITTLE parathyroid hormone (PTH)—leads to
a deficiency of blood Ca2+ (hypocalcemia),
leading to twitches, spasms, & tetany of
skeletal muscle
Hypoparathyroidism
▪ EXCESS PTH; 3rd most common endocrine
disorder
▪ Often caused by a parathyroid gland tumor
Hyperparathyroidism
a skeletal disorder
caused by an overproduction of parathyroid hormone from the overactive parathyroid glands.
Osteitis fibrosa cystica
▪ Hyposecretion of glucocorticoids & aldosterone
▪ Majority of cases are autoimmune disorders,
characterized by a peculiar bronze tone of skin
Addison’s disease
▪ Overproduction of the hormone aldosterone
by adrenal glands, typically result from
adrenal tumors
Hyperalderosteronism
▪ Hypersecretion of cortisol by the adrenal
cortex
▪ Causes include a tumor of the adrenal gland that secretes cortisol, or a tumor elsewhere that secretes ACTH, which in turn stimulates excessive secretion of cortisol
▪ Most often as a result of corticosteroids drugs
▪ “Cushingoid signs”: SWOLLEN “MOON” FACE, redistribution of fat to the abdomen and the posterior neck (causing a “buffalo hump”), easy bruising, and poor wound healing.
▪ May cause hyperglycemia, hypertension, and
hypercholesterolemia
▪ Decrease lymphocytes
Cushing’s Syndrome
▪ Hypersecretion of the sex hormones,
regardless of sex
▪ In females: beard develops & masculine
pattern of body hair distribution occurs
Masculinization
▪ Inability to produce/use insulin
▪ Blood glucose level is high & glucose “spills”
into the urine (glucosuria)
▪ Hallmarks: POLYURIA (huge urine output that
decreases blood volume & causes dehydration), polydipsia (excessive thirst), & polyphagia (excessive hunger/food
consumption)
Diabetes mellitus
insulin is absent
Type I Diabetes Mellitus
insulin is deficient
Type II Diabetes Mellitus
fatty acid metabolites or
ketones or ketone bodies are organic acids
that when they accumulate in the blood
Ketoacidosis:
▪ Often results when a diabetic injects TOO MUCH INSULIN
▪ Main symptom: hypoglycemia
Hyperinsulinism
▪ Autoimmune disease; primary hypothyroidism
▪ Chronic Autoimmune Thyroiditis
▪ INCREASE TSH
▪ Antibody present: Anti-TPO (thyroid peroxidase)
▪ Symptoms: a more common cause of goiter
Hashimoto’s disease
Primary Hypothyroidism
Decrease T3 and
T4; Increase TSH
Primary Hyperthyroidism
Increase T3 and
T4; Decrease TSH
▪ Presence of EXCESSIVE BODY & FACIAL HAIR in a male pattern, especially in women.
▪ May be due to EXCESS ANDROGEN production
due to tumors/drugs.
Hirsutism
is brought about by lack of efficiency of the ovaries
Menopause
AFTER ____
Thymus size begins to DECREASE , & thymic
tissue is replaced by adipose & areolar
connective tissue
PUBERTY
DEVELOPMENTAL ASPECTS OF THE ENDOCRINE
SYSTEM
- pituitary gland, adrenal medulla, pineal gland
Ectoderm
adrenal cortex
Mesoderm
thyroid gland, parathyroid gland,
pancreas, thymus
Endoderm
