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Lecture Outline
The Endocrine System
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Endocrine Glands
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Endocrine glands are ductless
Secrete hormones
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Chemical signals that influence:
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Metabolism
Growth and development
Homeostasis
Categories of hormones
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Peptides (proteins, glycoproteins, and
modified amino acids) – most hormones
Steroid hormones
PEPTIDE Hormones
Endocrine Glands
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How Peptide Hormones Function
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Second messenger system
Peptide hormone binds to a receptor
Peptide hormone “first messenger”
activates a “second messenger” (cyclic
AMP and calcium)
Second messenger sets in motion an
enzyme cascade that leads to:
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Change in cellular behavior
Formation of an end product that leaves the cell
STEROID Hormones
Endocrine Glands
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Intracellular mechanism of steroid
hormone function
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Steroid hormones (lipids) diffuse across
the plasma membrane
Once inside the cell, steroid hormones
bind to receptor proteins
Hormone-receptor complex binds to DNA,
activating particular genes
Gene activation leads to production of
cellular enzymes that cause cellular
changes
Endocrine Glands
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Hormone Control
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Release of hormones controlled by:
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The nervous system
The action of other hormones
Negative feedback mechanisms
Hypothalamus and Pituitary Gland
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Hypothalamus
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Controls secretions of the pituitary
gland
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Produces Neurosecretory cells:
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Antidiuretic hormone (ADH)
Oxytocin
Hypothalamus and Pituitary Gland
Hypothalamus and Pituitary Gland
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Posterior pituitary
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Stores hypothalamic hormones ADH
and oxytocin
ADH
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Released in response to elevated blood
salt concentrations
Causes more water reabsorption into
kidney capillaries
Raises blood pressure
Malfunction-Diabetes insipidus
Hypothalamus and Pituitary Gland
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Posterior pituitary
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Oxytocin
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Causes uterine contraction
Causes milk letdown
controlled by positive feedback
Hypothalamus and Pituitary Gland
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Anterior pituitary
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Controlled by hypothalamic hormones
Contains hormones that:
Affect other glands
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Thyroid-stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
Gonadotropic hormones
Effects of other hormones
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Prolactin (PRL)
Growth hormone (GH)
Hypothalamus and Pituitary Gland
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Effects of growth hormone
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Affects the height of an individual
Pituitary dwarfism- too little GH during
childhood
Gigantism- too much GH produced during
childhood
Acromegaly- too much GH is secreted in
adulthood
Thyroid
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Thyroid Gland
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Two forms of thyroid hormone
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Triiodothyronine (T3)
Thyroxine (T4) contains
Effects of thyroid hormone
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Increase the metabolic rate
Stimulate all cells of the body
Effects of Thyroid Hormones
Simple Goiter- lack of iodine
Effects of Thyroid Hormones
Myxedema
Congenital hypothyroidism
Effects of Thyroid Hormones
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Hyperthyroidism (Grave’s Disease)
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Oversecretion of thyroid hormone
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Symptoms include
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Hyperactivity
Nervousness and irritability
Insomnia
Thyroid
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Thyroid Gland
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Calcitonin
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Helps control blood calcium levels
Secreted when the blood calcium levels
rise
Brings about the deposit of calcium in the
bones
Parathyroid
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Parathyroid Glands
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Posterior surface of the thyroid gland
Produces parathyroid hormone (PTH)
Causes blood phosphate levels to decrease
Causes blood calcium (Ca2+) levels to increase
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Promotes the release of calcium from the bones
Promotes the reabsorption of calcium by the kidneys
Activates vitamin D in the kidneys, which
stimulates the reabsorption of calcium from the
intestines
Adrenal Glands
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Adrenal Medulla
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Inner portion
Under nervous control
Secretes epinephrine (adrenaline) and
norepinephrine (noradrenaline)
Causes “fight or flight” responses
Provide a short-term response to
stress
Adrenal Glands
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Adrenal Cortex
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3 layers
Under the control of ACTH
Hormones
Provide a long-term response to stress
Mineralcorticoids(i.e.aldosterone)promotes renal
absorption of sodium and water
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Atrial natriuretic hormone (ANH)
Glucocorticoids- raises blood glucose
levels
Male and female sex hormones
Adrenal Glands
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Malfunction of the Adrenal Cortex
Addison Disease
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Hyposecretion of adrenal cortex hormones
Excessive (but ineffective) ACTH causes
bronzing of the skin
Adrenal Glands
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Malfunction of the Adrenal Cortex
Cushing Syndrome
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Hypersecretion of adrenal cortex hormones
Tendency towards diabetes mellitus
Excess aldosterone
Pancreas
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Composed of two types of tissue
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Exocrine – secretes digestive juices
Endocrine tissue (pancreatic islets or
islets of Langerhans) produces:
Insulin
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Secreted when blood glucose level is high
Stimulates the uptake of glucose by most body
cells
Glucagon
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Secreted when blood glucose levels are low
Targets liver and adipose tissue
Stimulates liver to break down glycogen to
glucose
Pancreas
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Diabetes Mellitus
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Insulin-sensitive body cells are unable
to take up and/or metabolize glucose
Blood glucose level is elevated
(hyperglycemia)
Symptoms:
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Polyphagia – extreme hunger
Glycosuria – glucose in the urine
Polyuria – excessive water loss through
urine
Polydipsia – extreme thirst
Pancreas
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Two forms of diabetes mellitus
Type I – insulin-dependent diabetes
mellitus
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Pancreas does not produce insulin
Immune cells destroy the pancreatic islets
Type II – non-insulin-dependent diabetes
mellitus
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Normal or elevated amounts of insulin are
present in the blood
Receptors on the cells do not respond to insulin
Other Endocrine Glands
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Testes and ovaries
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Testes produce androgens
(testosterone)
Ovaries produce estrogens and
progesterone
Secretion is controlled by the
hypothalamus and the pituitary
Other Endocrine Glands
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Androgens
Increased testosterone secretion during
puberty stimulates the growth of the
penis and the testes
Brings about and maintains the male
secondary sex characteristics
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Facial, axillary, and pubic hair
Enlargement of larynx and the vocal cords
Muscular strength
Stimulates oil and sweat glands of the
skin
Other Endocrine Glands
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Estrogen and Progesterone
Required for breast development
Regulation of the uterine cycle
Estrogens
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Stimulate the growth of the uterus and the
vagina during puberty
Necessary for egg maturation
Responsible for secondary sex characteristics
Female body hair
Fat distribution
Other Endocrine Glands
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Thymus Gland
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Most active during childhood
Transforms lymphocytes into thymusderived lymphocytes (T-lymphocytes)
Epithelial cells secrete hormones
called thymosins
Pineal Gland
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Located in the brain
Produces the hormone melatonin
Melatonin is involved in daily sleepwake cycle
Other Endocrine Glands
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Hormones from Other Tissues
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Leptin
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Produced by adipose tissue
Signals satiety in hypothalamus
Growth Factors – stimulate cell
division and mitosis
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Granulocyte and macrophage colonystimulating factor
Platelet-derived growth factor
Epidermal growth factor and nerve
growth factor
Tumor angiogenesis factor
Other Endocrine Glands
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Prostaglandins
Potent chemical signals
Act locally
Some effects of prostaglandins include:
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Uterine contractions
Mediate the effects of pyrogens
Reduce gastric secretion
Lower blood pressure
Inhibit platelet aggregation
The Importance of Chemical Signals
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Cells and organs communicate
with one another using chemical
signals
Chemical signals between
individuals
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Called pheromones
Humans produce airborne chemicals
from a variety of areas
Effects of Aging
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Thyroid disorders
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Hypothyroidism
Hyperthyroidism
Diabetes
Homeostasis
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The endocrine system and the
nervous system work together to
maintain homeostasis
The endocrine system helps
regulate the following:
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Digestion
Fuel metabolism
Blood pressure and volume
Calcium balance
Response to the external environment