Transcript 1 - Lone Star College

Chapter 10
Lecture Outline
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10.1 Endocrine Glands
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A. Introduction
1.
Endocrine glands are ductless; secrete into
tissue fluids and then into the blood
2. Secrete hormones
a. Chemical signals that influence:
1) Metabolism
2) Growth and development
3) Homeostasis
3
Introduction, cont
b.
Categories of hormones
1) Peptides (proteins, glycoproteins, and
modified amino acids) – most
hormones
2) Steroid hormones
4
5
Principal Endocrine Glands and Hormones
6
B. How hormones function
1.
Second messenger system
a. Peptide hormone binds to a receptor
protein on the plasma membrane
b. Peptide hormone (“first messenger”)
activates a “second messenger” (cyclic
AMP and calcium)
c. Second messenger sets in motion an
enzyme cascade that leads to a large
cellular response
1) Change in cellular behavior
2) Formation of an end product that
leaves the cell
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Action of a Peptide Hormone
8
How hormones function, cont
2.
Intracellular mechanism of hormone
function
a. Steroid hormones (lipids) diffuse across
the plasma membrane
b. Once inside the cell, steroid hormones
bind to receptor proteins
c. Hormone-receptor complex binds to
DNA, activating particular genes
d. Gene activation leads to production of
cellular enzymes that cause cellular
changes
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Action of a Steroid Hormone
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C. Hormone control
1.
Controlling hormone release
a. Humoral – concentration of dissolved
substances or ions in the blood
b. Hormonal – actions of other hormones
that stimulate or inhibit release
c. Neural – brain can make adjustments to
maintain homeostasis
2. Many hormones are influenced by more
than one control mechanism
3. Most use negative feedback mechanisms,
although a few use positive feedback
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10.2
Hypothalamus and the Pituitary
Gland
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A. Hypothalamus
1.
Regulates the internal environment
through the autonomic nervous system
2. Controls secretions of the pituitary gland
a. Neurosecretory cells produce two
hormones that are stored and released
from the posterior pituitary gland
b. Produces releasing and inhibiting
hormones sent to the anterior pituitary
gland through a portal system
connection
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B. Posterior Pituitary Gland
1.
2.
Also called the neurohypophysis
Stores hypothalamic hormones ADH and
oxytocin
3. ADH – antidiuretic hormone or vasopressin
a. Released when neurons in the
hypothalamus detect that the blood is
too concentrated with salt
b. Causes more water to be reabsorbed into
kidney capillaries
c. Raises blood pressure by
vasoconstriction of blood vessels
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ADH, cont
d.
e.
f.
Controlled through negative feedback
mechanisms
Diabetes insipidus results from the
inability to produce ADH
Alcohol suppresses ADH production and
release
15
Posterior Pituitary Gland, cont
4. Oxytocin
a. Causes uterine contraction during
childbirth
b. Causes milk letdown when a baby is
nursing
c. Release of oxytocin is controlled by
positive feedback through a
neuroendocrine reflex
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C. Anterior Pituitary Gland
1.
Controlled by hypothalamic releasing and
inhibiting hormones that travel through a
portal system to the anterior pituitary
2. Hormones that affect other glands (tropic)
a. Thyroid-stimulating hormone (TSH) –
stimulates the thyroid to make and
release its hormones
b. Adrenocorticotropic hormone (ACTH) –
stimulates the adrenal cortex to make
and release its hormones
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Anterior pituitary gland, cont
c.
Gonadotropic hormones – control the
ovaries and testes
1) FSH – follicle-stimulating hormone
2) LH – luteinizing hormone
d. Utilizes a self-regulating negative
feedback
3. Effects of other hormones
a. Prolactin (PRL) – stimulates milk
production
b. Growth hormone (GH) – stimulates
growth
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The hypothalamus & pituitary gland
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Self-regulating negative feedback
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4. Effects of growth hormone
a. Affects the height of an individual
b. Pituitary dwarfism results if too little GH is
produced during childhood
c. If too much GH is produced during
childhood, a person can become a giant
d. Acromegaly results when too much GH is
secreted in adulthood
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Effects of abnormal GH
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10.3 Thyroid and Parathyroid
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A. Thyroid gland
1.
Two forms of thyroid hormone
a. Triiodothyronine (T3) contains 3 iodine
atoms
b. Thyroxine (T4) contains 4 iodine atoms
2. Effects of thyroid hormone
a. Increase the metabolic rate
b. Stimulate all cells of the body
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3. Thyroid abnormalities
a. Simple (endemic)
goiter
1) Caused by a lack
of iodine
2) Thyroid enlarges
in response to
constant
stimulation by the
anterior pituitary
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Thyroid abnormalities, cont
b. Congenital
hypothyroidism
1) Thyroid fails to
develop properly
2) Undersecretion of
thyroid hormone
3) Individuals are
short and stocky
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Thyroid abnormalities, cont
c.
Myxedema
1) Hypothyroidism in adults
2) Characterized by
a) Lethargy
b) Weight gain
c) Loss of hair
d) Slower pulse rate
e) Lowered body temperature
f) Thick and puffy skin
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Thyroid abnormalities, cont
d. Hyperthyroidism (Grave’s Disease)
1) Oversecretion of thyroid hormone
2) Exophthalmic goiter forms
a) Edema in eye socket tissues
b) Swelling of the muscles that move
the eyes
3) Symptoms include
a) Hyperactivity
b) Nervousness and irritability
c) Insomnia
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Thyroid gland, cont
4. Calcitonin
a. Helps control blood calcium levels
b. Secreted when the blood calcium
levels rise
c. Brings about the deposit of calcium in
the bones
d. Reduces activity and number of
osteoclasts
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B. Parathyroid glands
1.
2.
On the posterior surface of the thyroid gland
Produces parathyroid hormone (PTH)
a. Causes blood phosphate (HPO42-) level to
decrease
b. Causes blood calcium (Ca2+) level to increase
1) Promotes the release of calcium from the
bones
2) Promotes the reabsorption of calcium by the
kidneys
3) Activates vitamin D in the kidneys, which
stimulates the reabsorption of calcium from
the intestines
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3. Parathyroid abnormalities
a.
b.
Hypocalcemic tetany (continual muscle
spasms) results when there is insufficient
secretion of PTH
Hypercalcemia – causes muscle weakness,
abnormal heart rhythms, renal failure,
coma, and death
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Regulation of blood calcium level
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10.4 Adrenal Glands
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A. Adrenal medulla
1.
2.
3.
4.
5.
Inner portion
Under nervous control
Secretes epinephrine (adrenaline) and
norepinephrine (noradrenaline)
Causes “fight or flight” responses
Provide a short-term response to stress
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B. Adrenal cortex
1.
Outer portion – 3 layers, each produces a
different set of hormones
2.
Under the control of ACTH from the anterior
pituitary
3.
Hormones
a. Glucocorticoids - regulate carbohydrate,
protein, and fat metabolism to increase blood
glucose levels; provide a long-term response to
stress
b. Mineralocorticoids – regulate salt and water
balance for blood volume and pressure
c. Male and female sex hormones – promote
skeletal growth, changes at puberty, libido
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Adrenal Glands
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4. Glucocorticoids (cortisol)
a. Raises the blood glucose level in at least 2 ways:
1) Promotes breakdown of muscle proteins to
amino acids that the liver converts to glucose
2) Spares glucose for the brain by promoting
metabolism of fatty acids in other cells
b. Glucocorticoid therapy
1) Counteracts the inflammatory response and can
relieve swelling and pain
2) Can also make a person susceptible to injury
and infection
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5. Mineralocorticoids (aldosterone)
a. Targets the kidney
b. Promotes renal absorption of sodium and
water
c. Promotes renal excretion of potassium
d. ACTH is not the primary controller for
aldosterone secretion
e. Renin-Angiotensin mechanism stimulates
aldosterone secretion when the blood
sodium level and blood pressure are low
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Mineralocorticoids, cont
f.
Renin-Angiotensin-Aldosterone system
raises blood pressure in two ways:
1) Angiotensin II constricts arterioles
2) Aldosterone causes the kidneys to
reabsorb sodium
g. Atrial natriuretic hormone (ANH) is
antagonistic to aldosterone
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Regulation of blood pressure & volume
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C. Malfunction of the adrenal cortex
1. Addison’s Disease
a. Hyposecretion of adrenal cortex
hormones
b. Excessive (but ineffective) ACTH causes
bronzing of the skin
c. Because glucose cannot be replenished
without cortisol, individuals are
susceptible to infection
d. Lack of aldosterone results in the
development of low blood pressure and
possibly severe dehydration
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Addison’s Disease
42
Malfunction of the adrenal cortex, cont
2.
Cushing’s Syndrome
a. Hypersecretion of adrenal cortex
hormones
b. Tendency towards diabetes mellitus
c. Excess aldosterone leads to
hypertension
d. Fat deposited in the trunk and face
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Cushing’s Syndrome
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10.5 Pancreas
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A. Composed of two types of tissue
1.
2.
Exocrine – secretes digestive juices
Endocrine tissue (pancreatic islets or islets
of Langerhans) produces:
a. Insulin – produced by beta cells
1) Secreted when blood glucose level is
high
2) Stimulates the uptake of glucose by
most body cells
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Two types of tissue, cont
b.
Glucagon – produced by alpha cells
1) Secreted when blood glucose levels
are low
2) Targets liver and adipose tissue
3) Stimulates liver to break down
glycogen to glucose
c. Somatostatin
1) Produced by delta cells
2) Prevents release of insulin and
glucagon
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Regulation of blood glucose levels
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B. Diabetes Mellitus
1.
Insulin-sensitive body cells are unable to
take up and/or metabolize glucose
2. Symptoms:
a. Hyperglycemia – high blood glucose
b. Polyphagia – extreme hunger
c. Glycosuria – glucose in the urine
d. Polyuria – excessive water loss through
urine
e. Polydipsia – extreme thirst
f. Ketonuria – ketones in urine; causes
acidosis
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Diabetes mellitus, cont
3. Two forms of diabetes mellitus
a. Type I – insulin-dependent diabetes
mellitus (IDDM)
1) Pancreas does not produce insulin
2) Immune cells destroy the pancreatic
islets
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Diabetes mellitus, cont
b.
Type II – non-insulin-dependent
diabetes mellitus (NIDDM)
1) Normal or elevated amounts of insulin
are present in the blood
2) Receptors on the cells do not respond
to insulin
3) Tends to occur in obese individuals
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Diabetes mellitus, cont
4.
Prediabetes – blood glucose chronically
elevated
5. Long-term complications of both types of
diabetes mellitus
a. Blindness
b. Kidney disease
c. Circulatory disorders
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10.6 Additional Endocrine Glands
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A. Testes and ovaries
1.
2.
3.
Testes produce androgens (testosterone)
Ovaries produce estrogens and
progesterone
Secretion is controlled by the
hypothalamus and the anterior pituitary
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4. Androgens
a. Increased testosterone secretion during
puberty stimulates the growth of the penis
and the testes
b. Brings about and maintains the male
secondary sex characteristics
1) Facial, axillary, and pubic hair
2) Enlargement of larynx and the vocal
cords
3) Muscular strength
c. Stimulates oil and sweat glands of the skin
d. Baldness
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5. Estrogen and progesterone
a. Required for breast development
b. Regulation of the uterine cycle
c. Estrogens
1) Stimulate the growth of the uterus and
the vagina during puberty
2) Necessary for egg maturation
3) Responsible for secondary sex
characteristics
a) Female body hair
b) Fat distribution
c) Wider pelvic girdle
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B. Thymus Gland
1.
2.
3.
Most active during childhood
Transforms lymphocytes into thymusderived lymphocytes (T-lymphocytes) –
responsible for specific defenses
Epithelial cells secrete hormones called
thymosins
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C. Pineal Gland
1.
2.
3.
4.
Located in the brain
Produces the hormone melatonin that is
released at night
Melatonin is involved in daily sleep-wake
cycle (circadian rhythms)
Also helps regulate sexual development
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Melatonin Productions
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D. Hormones from other tissues
1.
Atrial natriuretic hormone
a. Produced by the atria of the heart when
blood pressure and/or volume increases
b. Targets the kidneys to increase urine
volume
2. Erythropoietin
a. Produced by the kidneys
b. Targets red bone marrow to increase
production of red blood cells
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Hormones from other tissues, cont
3.
Leptin
a. Produced by adipose tissue
b. Signals satiety in hypothalamus
4. Ghrelin
a. Produced by the stomach
b. Signals hunger
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Hormones from other tissues, cont
5.
Growth Factors – stimulate cell division
and mitosis
a. Granulocyte and macrophage colonystimulating factor – stimulates bone
marrow stem cells
b. Platelet-derived growth factor – woundhealing
c. Epidermal growth factor and nerve
growth factor – wound healing
d. Tumor angiogenesis factor – formation
of capillary networks to tumors
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6. Prostaglandins
a. Potent chemical signals
b. Act locally – not distributed by the blood
c. Some effects of prostaglandins include:
1) Uterine contractions
2) Mediate the effects of pyrogens
3) Reduce gastric secretion
4) Lower blood pressure
5) Inhibit platelet aggregation
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10.7 The Importance of Chemical
Signals
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The Importance of Chemical Signals
A.
Cells and organs communicate with one
another using chemical signals
1. Hormones
2. Prostaglandins
3. Neurotransmitters
4. Growth factors
B. Chemical signals between individuals
1. Called pheromones
2. Humans produce airborne chemicals from
a variety of body areas
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10.8 Effects of Aging
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Effects of Aging
A.
Thyroid disorders
1. Hypothyroidism
2. Hyperthyroidism
B. Diabetes mellitus
C. Thymus and pineal glands decreases in
size
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10.9 Homeostasis
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Homeostasis
A.
The endocrine system and the nervous
system work together to maintain
homeostasis
B. The endocrine system helps regulate
the following:
1. Digestion
2. Fuel metabolism
3. Blood pressure and volume
4. Calcium balance
5. Response to the external environment
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Human Systems Work Together
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