Endocrine System
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Cell to cell communication
Nervous versus endocrine system
What it is and does: an overview
Classes of hormones
Mechanisms of action
Cell responses to hormones
Stimulation of secretion
Major endocrine glands and their hormones
Stress response
Other hormone producing tissues
Exocrine Versus Endocrine
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Cell to Cell Communication
Cell to Cell Communication
Chemical messengers
„ e.g., ions between muscle
cells
„ Local regulators
Means of communication
„ Direct cell to cell (gap
junctions)
„ Autocrine-secrete to self
„ Paracrine-secrete nearby
„ Endocrine-secrete into the
blood
„ Neural communicationsecrete into synapses
„ Neurosecretory cell-nerve
cell secretes into the blood
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Hormones
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Neurotransmitters
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Neurohormones
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Nervous System Versus
Endocrine System
Pheromones
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Chemical signals that affect the metabolism and influence
the behavior of other individuals
Women who live in the same household often have
menstrual cycles in synchrony
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Axillary secretions responsible
Male sweat boosts women's hormone levels
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Study provided evidence that humans secrete a scent that affects
the physiology of the opposite sex
20 sniffs from a bottle containing androstadienone
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Fast-acting
Short duration
Target is close
Few targets
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Slow-acting
Long duration
Target at a distance
Can have many targets
Smells musky
Improved mood and significantly higher sexual arousal
Physiological responses
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Increased blood pressure, heart rate and breathing rate
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Overview of What the
Endocrine System Is
Major Endocrine Glands
Consists of ductless glands
Small size
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Widely separated — near midline of body
Purely endocrine, exocrine and endocrine, mixed functions
Rich blood supply
Unique cytology
Acts through chemical signals called hormones
Influences only those cells that have receptors (target cells)
„ Localized in a single gland or organ
„ Target cells diffuse
Hormones are potent substances
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Overview of What the
Endocrine System Does
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Classes of Hormones
Chemical Structure
The major processes controlled by hormones
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Reproduction
Growth
Development
Biological rhythm — ex. sleep cycles
Metabolic rate
H2O, ion, and nutrient balance
Heart rate and blood pressure
Immunity — stimulates or suppresses
Body defense against stress
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Made from cholesterol
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Made of amino acids
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Steroid hormones
Amino acid derivatives
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Epinephrine and norepinephrine
Thyroid hormones
Peptides, proteins, glycoproteins
Solubility
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Lipid versus H2O soluble
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Modified Amino Acid
Tyrosine
Steroid Hormones
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Mechanisms of Action
Lipid-Soluble Hormones
Mechanisms of Action
Lipid-Soluble Hormones
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Steroid hormones enter their target cells where
they bind intracellular receptors
The hormone
- receptor complex almost always
effects gene expression and leads to the
synthesis of new proteins
The new proteins cause the response specific
to the hormone
Slow response
Animation: Mechanism of Steroid Hormone
Action
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Mechanisms of Action
Water-Soluble Hormones
Mechanisms of Action
Water-Soluble Hormones
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Animation:
Action of
Epinephrine
on a Liver
Cell
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Have a membrane
- bound receptor
Trigger response via intracellular 2nd
messengers
2nd messengers activate enzymes that will
cause the cell’s response to the hormone
Signal transduction pathway
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Cascade effect with amplification
Fast response
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Responses at the
Chemical and Cellular Level
Stimulation and Control of
Hormone Secretion
Synthesis of new molecules
„ Alter membrane permeability
„ Inactivate/activate enzymes
„ Stimulate mitosis
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Dependent on hormone and tissue type
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Stimulated/inhibited by
Control of secretion
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Insulin stimulates liver cells to produce
glycogen and fat cells to produce triglycerides
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Hormones—most common
Blood level of chemicals—ions or nutrients
Nervous system
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Mostly negative, some positive feedback
Antagonistic hormone pairs
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Stimulation and Control of
Hormone Secretion
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Hypothalamus and the
Pituitary Gland
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Hypothalamus produces hormones and controls the
secretions of the pituitary gland
Pituitary is bi-lobed and the size of a pea
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Hypothalamus
and the Posterior Pituitary
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Antidiuretic hormone (ADH)—promotes water
reabsorption by kidneys
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Target cells are in collecting ducts
Controlled by negative feedback
Diabetes insipidus (watery urine) —inability to produce ADH
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Oxytocin—stimulates uterine contractions during
childbirth and milk ejection
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Both hormones are produced in the hypothalamus by
neurosecretory cells
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Controlled by positive feedback
Stored in the posterior lobe of the pituitary gland
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Hypothalamus and the Anterior
Pituitary: Tropic Hormones
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Hypothalamus secretes releasing or inhibiting
hormones
Thyroid-stimulating hormone (TSH)—stimulates
synthesis and secretion of thyroid hormones
Adrenocorticotropic hormone (ACTH)—stimulates
synthesis and secretion of glucocorticoids from
adrenal cortex
Gonadotropic hormones (FSH, LH)—stimulates
gonads to produce gametes and hormones
TSH, ACTH, FSH, LH are tropic hormones
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Prolactin (PRL)—causes mammary glands to
develop and produce milk
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Melanocyte-stimulating hormone (MSH)—
causes skin cells to produce melanin
Growth hormone (GH)—stimulates an increase in
cell size and the rate of cell division in target cells
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Stimulates rate of uptake of amino acids and protein synthesis
Stimulates breakdown of fat
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Can reach heights of 8 to 9 feet
Usually characterized by poor health and shortened lifespan
Acromegaly—abnormally high production during adulthood
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Small stature (~4 ft) and sterile
Can be treated with GH
Giantism—abnormally high production during childhood
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Especially muscle, bone, and cartilage
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Pituitary dwarfism—abnormally low production during childhood
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Interfers with female sex hormone function
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Thickening of bones of hands,face, and feet
Enlargement of tongue
Some athletes take GH to build muscles
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Thyroid Gland
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Thyroid Tissue
Thyroid hormone or thyroxine—stimulates nearly all body cells
„ Regulates the body’s metabolic rate and heat production
„ Regulates blood pressure
„ Promotes normal development and functioning of several organ systems
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Nervous, muscular, skeletal, and reproductive systems
Affects cellular metabolism
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Effects of Abnormal Levels of
Growth Hormone
Hypothalamus and
the Anterior Pituitary
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Act on other endocrine glands
Stimulates protein synthesis, breakdown of lipids and glucose for ATP
production
Calcitonin—decreases blood calcium levels
„ Stimulates absorption of calcium by bone
„ Reduces blood calcium by inhibiting activity of osteoclasts
„ Stimulates excretion by kidney
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Effects of Abnormal Thyroid
Hormone Levels
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Congenital hypothyroidism and cretinism—abnormally low thyroxine
production during childhood
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Short, stocky, mentally retardation if not diagnosed early
Oral doses can prevent cretinism
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Myxedema or hypothyroidism—abnormally low thyroxine production during
adulthood
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Simple goiter—enlarged thyroid gland due to lack of iodine in the diet
Hyperthyroidism—abnormally high thyroxine production
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Lethargy, edema in facial tissue, decreased body temperature and heart rate
Grave’s disease—autoimmune disease where antibodies produced mimic
action of TSH
Increased metabolic rate and heart beat, goiter, exopthalmus, nervousness,
irritability, insomnia, weight loss, sweating
Can be treated with drugs, surgery, or radioactive iodine
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Thyroid and
Parathyroid Glands
Parathyroid (PT) Glands
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Four small glands embedded in the posterior lobes of
the thyroid gland
We cannot live without them—death from tetany
Secretes parathyroid hormone (PTH) which raises
blood calcium levels of the blood
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Bones release calcium through increased osteoclast activity
Promotes reabsoprtion of calcium from kidney tubules
Activates Vitamin D which increases absorption from
intestine
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Antagonistic Hormone Pairs:
Calcitonin and Parathyroid Hormone
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Adrenal Glands
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Adrenal Glands
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Adrenal cortex—secretes 20 different hormones
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Gonadocorticoids—androgens and estrogen
Mineralocorticoids—affect mineral homeostasis and water balance
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Glucocorticoids—affects bloods glucose levels
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Conserves carbohydrates and promotes breakdown of protein and fat
Inhibits inflammatory response
Cushing syndrome—oversecretion of glucocorticoids resulting in fluid
accumulation, body fat redistribution, high blood pressure, fatigue
Addison’s disease—autoimmune disease that results in destruction
of cells of adrenal cortex
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Aldosterone—promotes absorption of Na+ and water and excretion of K+
Weight loss, fatigue, electrolyte imbalance, poor appetite and
resistance to stress, bronzing of skin
Adrenal medulla
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Epinephrine and norepinephrine prepares the body for quick action
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Stress Response
Pancreas
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Antagonistic Hormone Pairs:
Insulin and Glucagon
Pancreas
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Has both endocrine and exocrine functions
Hormones are secreted by the pancreatic islets
Glucagon increases blood glucose level
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Stimulates conversion of glucagon to glucose in the liver
Stimulates formation of glucose from lactic acid and amino acids
Insulin decreases blood glucose levels
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Stimulates uptake of glucose into muscle cells, white blood cells,
and connective tissue cells
Inhibits the breakdown of glycogen and prevents conversion of
amino and fatty acids to glucose
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Promotes protein synthesis, fat storage, and use of glucose for
energy
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Effects of
Abnormal Insulin Secretion
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Diabetes mellitus—caused by the lack of insulin or by the
inability of cells to take up glucose
Type 1 diabetes mellitus—an autoimmune disease
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Ovaries produce estrogen and progesterone
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Pineal Gland
Lies just behind sternum upon the heart
Reaches largest size and most active during
childhood with aging gets smaller
Secretes thymosins and thymopoietin
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Prompts larynx and vocal cords to enlarge
Hair growth
Responsible for muscular strength of males
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Thymus
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Breast development and body contours
Sperm production
Development and maintenance of male reproductive structures
Responsible for secondary sex characteristics
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Heredity and obesity are major risk factors
Dietary restrictions, weight loss, exercise, and possibly insulin
Increased risk of blindness, kidney and heart disease, high
blood pressure, atherosclerosis, gum disease, impotence,
neuropathy, poor circulation
Regulates uterine and ovarian cycles
Testes produce testosterone
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Cells do not have enough insulin receptors
Most common type—90 to 95% of diabetes cases
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Immune system attacks the pancreatic islet cells responsible for
insulin production
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Necessary for egg maturation
Development and maintenance of female reproductive structures
Responsible for secondary sex characteristics
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Type 2 diabetes mellitus—inability of cells to respond to insulin
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Gonads
Aid in maturation and differentiation of Tlymphocytes
May be used in the future for AIDS or cancer
patients to enhance T
- lymphocyte function
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Pineal Gland and Melatonin
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Other Hormone Producing Tissues
Melatonin levels increase at night and are low during the day
Affect circadian (daily rhythms) and can reset body’s internal
clock
„ Supplements help with jet lag, night-shift workers, maybe
insomnia and immunity
Signals hibernation
Inactivates reproduction in seasonally reproducing animals
May slow aging process by destruction of free radicals
High melatonin can cause sleepiness, lethargy, low spirits,
carvings for carbs
May play role in seasonal affective disorder (SAD)
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Depression associated with winter and high melatonin levels
Most affected are female
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Adipose
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Placenta
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Growth factors—peptides or proteins that stimulate cell division
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Leptin—signals satiety (had enough to eat)
hCG
Vascular endothelial growth factor
Platelet derived growth factor
Prostaglandins—not distributed in blood and act locally
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Cause muscles to contract and are implicated in the pain and discomfort
of menstruation
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Used to treat gastric reflux, hypertension, and to prevent thrombosis
Endothelial cells
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Nitric oxide—dilation of blood vessels and is a neurotransmitter
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