There are 8 major endocrine glands1. Pituitary gland2. Thyroid gland3. Thymus4. Pancreas5. Gonads (testis/ovaries)6. Adrenal gland7. Parathyroid gland8. Pineal gland
Critical Thinking
The nervous and endocrine systems are responsible for maintaining what?
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a. Nervous system: acts through electrical impulses and neurotransmitters To cause muscle
contraction and glandular secretion
Effect: short duration, measured in seconds, localized
b. Endocrine system: acts through chemical messengers (hormones) Hormones influence
growth, development, and metabolic activities
Action is measured in minutes, hours, or weeks and is more generalized
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Comparison of the
Endocrine and Nervous Systems
Critical ThinkingWhat is the difference in an exocrine
gland and an endocrine
gland?4
Comparison of Exocrine andEndocrine Glands
1. Exocrine glands: have ducts that carry their secretory product to a surface Examples: sweat, sebaceous, and mammary
glands and glands that secrete digestive enzymes
2. Endocrine glands: secrete hormones directly into the into blood which carries them throughout body, they have no ducts
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Critical Thinking
What are hormones
made up of?
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Characteristics of Hormones Chemical classification
a. Proteins: make up most of the hormones in the body Difficult to administer orally
Inactivated by acid and pepsin in stomach Must be given by injection
(example: insulin)
b. Steroids: make up sex hormones and hormones secreted by the adrenal cortex May be given orally
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Characteristics of Hormones
The specific cells that respond to a given hormone have receptor sites for that hormone “Lock and key” mechanism If a hormone fits the
receptor site: there will be an effect
If a hormone and a receptor site do not match: there is no reaction
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Characteristics of Hormones Target tissue: a tissue
(cells) that responds to a particular hormone because it has receptor sites for that hormone May be localized in a
single gland or organ May be diffuse and
scattered throughout body Many areas are affected
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Endocrine Glands
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The Pituitary Gland The “Master Gland” Small-size of a pea Connected to
hypothalamus by a slender stalk: infundibulum
Two regionsa. Adenohypophysis:
anterior portion b. Neurohypophysis:
posterior portion
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Growth hormone (GH) Thyroid stimulating hormone (TSH) Adrenocorticotrophic hormone
(ATCH) Gonatrophic hormone Follicle stimulating hormone (FSH) Leutinizing hormone (LH) Prolactin hormone (PRH)
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Hormones of the Anterior Lobe (Adenohypophysis)
1. Growth hormone (GH) Stimulates growth of bones, muscles, and other organs Influences height Too little GH in a child: pituitary dwarf of normal proportions
but small stature Excess of GH in a child: individual becomes exceptionally tall After ossification is complete (bone length no longer possible) Excess GH in adult causes enlargement in the diameter of the
bones: acromegaly bones of the hands and face become abnormally large
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Hormones of the Anterior Lobe (Adenohypophysis)
2. Thyroid-stimulating hormone (TSH) Causes glandular cells of
thyroid to secrete thyroid hormone
Hypersecretion of TSH: thyroid gland enlarges and secretes too much thyroid hormone
Hyposecretion of TSH: results in atrophy of thyroid gland and too little thyroid hormone
HINT: this is not the same hormone that is produced by the thyroid gland!
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Hormones of the Anterior Lobe (Adenohypophysis)
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Thyroid Gland
Vascular organ: located in neck Consists of two lobes: one on each
side of tracheaThyroxine and Triiodothyronine Thyroid hormone consists of:
Thyroxine: 95% Triiodothyronine: 5%
Requires iodine for synthesis
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Thyroid Gland
Iodine and the Thyroid Gland Iodine is required for synthesis of thyroid
hormone Iodine deficiency: thyroid cannot make
sufficient hormone and the thyroid gland increases in size in an attempt to produce more thyroid hormone.
Known as simple goiter or iodine deficiency goiter
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Thyroid Gland
Help to regulate the metabolism of carbohydrates, proteins, and lipids Increases rate at which cells release energy
from carbohydrates Enhances protein synthesis Necessary for normal growth and
development Stimulates nervous system
Do not have a single target organ Affect most of the cells in the body
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Hypothyroidism Deficiency of thyroid
hormonea. Cretinism: in a child
Mentally retarded dwarf with abnormal skeletal features
Tx: thyroid hormone therapyb. Myxedema: in an adult
Lethargy, weight gain, loss of hair, low metabolic rate
Thyroid hormone therapy: usually alleviates symptoms
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Hyperthyroidism Enlarged thyroid gland that
produces too much hormone Symptoms: High metabolic
rate, hyperactivity, insomnia, nervousness, irritability, chronic fatigue Exophthalmos: protruding eyes due to swelling in tissues behind the eyes
Treatment: removal or destruction of a portion of the thyroid gland
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Grave’s Disease
Thyroid Gland
Calcitonin Secreted by thyroid gland Reduces the calcium level in the blood by:
Reducing rate at which calcium is released from bone
Increasing rate of calcium excretion by kidneys
Reducing calcium absorption in intestines
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Parathyroid Glands
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1. Four small masses of epithelial tissue located on the posterior surface of the thyroid glands
2. Secrete parathyroid hormone (PTH)
3. When blood calcium levels become low the PTH is released to increase levels
4. Vitamin D is necessary for dietary calcium to be absorbed in intestines
Parathyroid PTH has opposite effect of calcitonin from
the thyroid gland Hypoparathyroidism: insufficient
secretion of PTH can cause increased nerve excitability due to low blood calcium levels
Hyperparathyroidism: excessive secretion of PTH Excess calcium in the blood:
May precipitate in abnormal locations Causes kidney stones
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3. Adrenocorticotropic hormone (ACTH) Reacts with receptor sites in
the cortex of adrenal gland To stimulate secretion of
cortical hormones (cortisol) Affects melanocytes in the
skin: increases pigmentation
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Hormones of the Anterior Lobe (Adenohypophysis)
Adrenal Glands (Suprarenal)
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1. Paired glands: one located near upper portion of each kidney
2. Divided into 2 regions:a. Adrenal cortex:
outer regionb. Adrenal medulla:
inner region
Hormones of the Adrenal Cortex
1. Mineralocorticoids: Regulate the concentration of mineral electrolytes in the blood (Aldosterone)
2. Glucorticoids: Produce cortisol which helps to maintain glucose levels and counteract inflammation
3. Gonadocorticoids: Sex hormones Androgens: Males Estorgens: Females
4. Addison’s disease: hyposecretion5. Cushing’s syndrome: hypersecretion
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Hormones of the Adrenal Medulla
1. Epinephrine and Norepinephrine 2. Prepares body for strenuous activity
Sometimes called fight-or-flight hormones3. Effect on body: increased heart rate,
increased respiratory rate, increased blood supply to skeletal muscles
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4. Gonadotropic hormones React with receptor sites in the gonads
(ovaries and testes) To regulate development, growth, and function
of these organs Follicle-stimulating hormone (FSH)
Stimulates development of eggs in the ovaries and sperm in testes
Stimulates estrogen production in female
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Hormones of the Anterior Lobe (Adenohypophysis)
Luteinizing hormone (LH) Female: causes ovulation, production and
secretion of female sex hormones1) Progesterone2) Estrogen Male: sometimes called interstitial cell-
stimulating hormone (ICSH) Stimulates interstitial cells of testes
1) To produce and secrete testosterone (male sex hormone)
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Hormones of the Anterior Lobe (Adenohypophysis)
Without gonadotropins: Ovaries and testes decrease in size Ova and sperm are not produced Sex hormones are not secreted
Prolactin (PRL) Promotes development of glandular tissue in
female breast during pregnancy Stimulates milk production after birth of
infant
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Hormones of the Anterior Lobe (Adenohypophysis)
Hormones of the Posterior Lobe (Neurohypophysis)
1. Antidiuretic hormone (ADH) Promotes reabsorption of water by the
kidney tubules Less water is lost as urine Conserves water for the body
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Hormones of the Posterior Lobe (Neurohypophysis)
b. When not enough ADH is produced there is excessive water loss in urine Large amounts of dilute urine: known as
diabetes insipidusc. Large amounts of ADH: cause blood vessels
to constrict Increases blood pressure ADH sometimes called vasopressin
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Hormones of the Posterior Lobe (Neurohypophysis)
2. Oxytocin Causes contraction of smooth muscle in wall
of uterus Stimulates ejection of milk from lactating
breast Pitocin: commercial preparation of this
hormone Used to induce labor
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Endocrine Glands andTheir Hormones
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Pancreas Islets of
Langerhans Long, soft organ Located posterior
to stomach Exocrine portion:
secretes digestive enzymes Carried through a
duct to duodenum
Endocrine portion: secretes hormones into blood
Alpha cells: secrete glucagon
Beta cells: secrete insulin
Glucagon & insulin regulate blood glucose levels
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Glucose GlucosePrimary energy source for nervous systemIf glucose levels too low nervous system does
not function properlyIf glucose levels too high kidneys produce
large volumes of urine that can lead to dehydration
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Pancreas
Glucagon Secreted by alpha cells in pancreatic islets
In response to low concentration of glucose in blood
Action: raises blood glucose levels Stimulates liver to break down glycogen into
glucose Prevents hypoglycemia from occurring
Between meals When glucose is being used rapidly
Given in response to severe hypoglycemic episodes in injection form
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Insulin
Insulin Secreted by beta cells in pancreatic islets
In response to a high concentration of glucose in blood
Action of insulin: decreases blood glucose level (opposite or antagonistic to glucagon) Promotes cellular uptake and use of glucose
for energy Stimulates liver and muscle to remove
glucose from blood Stores it as glycogen
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Pancreas When the liver has stored all the glycogen
possible: Glucose is converted to fat
Hypoactivity of insulin Insufficient insulin secretion Insufficient receptor sites on target cell
membranes Defective receptor sites that do not
recognize insulin Leads to diabetes mellitus (abnormally high
blood glucose)
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Gonads
Primary reproductive organs Testes: male secrete androgens Ovaries: female secrete estrogen and
progesterone
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Gonads (Testes and Ovaries)
Pineal Gland Extends from third ventricle of brain Synthesize melatonin
Secrete it directly into cerebrospinal fluid: takes it into blood
High levels: secreted at night Low levels: secreted during day Regulation of circadian rhythms Example: sleepiness/wakefulness cycle
Increased plasma melatonin levels (night): associated with sleepiness
Plays a role in hunger/satiety cycles, mood changes, and jet lag
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