FINALS: ENDOCRINE SYSTEM Flashcards by Sunwoo's Berry

▪ 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

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Hormones control several major processes:

o Reproduction
o Growth and development
o Mobilization of much of homeostasis
o Regulation of metabolism

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▪ 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

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Chemical classification of hormones:
(proteins, peptides, amines)

Amino acid-based hormones

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Chemical classification of hormones:
(cholesterol)

Steroids

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Chemical classification of hormones:
(highly active lipids)

Prostaglandins

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TYPES OF HORMONE ACTION:
- is secreted in one location (ducts)
and released into BLOOD circulation.

Endocrine

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TYPES OF HORMONE ACTION:
- is secreted in endocrine cells and
released into INTERSTITIAL SPACE.

Paracrine

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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

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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

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TYPES OF HORMONE ACTION:
- is secreted in endocrine cells and
released into the LUMEN OF GUT

Exocrine

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TYPES OF HORMONE ACTION:
- is secreted in the NEURONS and released from nerve endings; interacts with receptors of cells at distant site.

Neuroendocrine

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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

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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

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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

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WHAT TYPE OF STIMULUS?
- endocrine glands are activated by other hormones

HORMONAL STIMULUS

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WHAT TYPE OF STIMULUS?
- changing blood levels of certain ions stimulate hormone release

HUMORAL STIMULUS

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WHAT TYPE OF STIMULUS?
- nerve impulse stimulate hormone release

NEURAL STIMULUS

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▪ “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)

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PITUITARY GLAND 2 FUNCTIONAL LOBES:
- AKA adenohypophysis, 3 parts are derived
embryonically from the hypophyseal pouch

Anterior pituitary (glandular tissue)

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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

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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

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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

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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)

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▪ 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