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Inquiry into Life
Twelfth Edition
Sylvia S. Mader
Chapter 20
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
20.1 Endocrine Glands and Hormones
• The endocrine system consists of glands and
tissues that secrete hormones
• Hormones are chemicals that affect other glands
or tissues, many times far away from the site of
hormone production
20.1 Endocrine Glands and Hormones
• Hormones Influence:
– Metabolism of cells
– Growth and development of body parts
– Homeostasis
• Endocrine Glands
– Are ductless
– Secrete hormones into tissues, the hormones then
diffuse into the bloodstream
20.1 Endocrine Glands and Hormones
• Hormones and Homeostasis
– Homeostasis requires cooperation between the
endocrine and nervous systems.
Endocrine System
Nervous System
Secretes hormones into
the blood
Transmits nerve impulses
Slower response
Faster response
More prolonged response
Less prolonged response
The Endocrine System
20.1 Endocrine Glands and Hormones
• Control of the
Production of
Hormones
– Negative Feedback
– Action of other
hormones
20.1 Endocrine Glands and Hormones
• Control of the Production of Hormones
– Action of other hormones
– Example:
The anterior pituitary gland produces
thyroid-stimulating hormone
» The thyroid then produces hormones
– Example:
Antagonistic hormones
» Insulin and glucagon
20.1 Endocrine Glands and Hormones
• The Action of Hormones
– Two Classes of Hormones
• Peptide Hormones
• Steroid Hormones
Peptide Hormone Action
Steroid Hormone Action
20.2 Hypothalamus and
Pituitary Gland
• Two Ways the Hypothalamus Regulates the
Internal Environment
– Through the Autonomic Nervous System
• Heartbeat, blood pressure, appetite, body temperature, water
balance
– By Controlling the Pituitary Gland
• Posterior Pituitary
• Anterior Pituitary
20.2 Hypothalamus and
Pituitary Gland
• Posterior Pituitary
• Physically connected to the hypothalamus by a
stalk
• Hormones travel down axons and stored in axon
terminals in posterior pituitary
• Neurosecretory cells produce ADH and Oxytocin
20.2 Hypothalamus and
Pituitary Gland
• Posterior Pituitary
• ADH- Antidiuretic Hormone
– Released from posterior pituitary in response to
increased concentration of blood (not enough water)
– ADH causes increased reabsorption of water in the
kidneys
» As water reabsorption occurs, the blood
concentration becomes normal and ADH is shut off
20.2 Hypothalamus and
Pituitary Gland
• Posterior Pituitary
– Oxytocin
• Causes uterine contractions and milk letdown in lactation
• Neurological impulses from pressure and irritation of uterus
causes oxytocin release
– Oxytocin causes contractions which causes more pressure and
irritation more oxytocin more contractions
» An example of positive feedback
• Neurological stimulus of suckling causes oxytocin release
20.2 Hypothalamus and
Pituitary Gland
• Anterior Pituitary
– Functionally connected to the hypothalamus by the
bloodstream
– Hypothalamus controls the anterior pituitary by
producing:
• Hypothalamic-releasing hormones
• Hypothalamic-inhibiting hormones
20.2 Hypothalamus and
Pituitary Gland
• Anterior Pituitary
– Three anterior pituitary hormones have target effect
on other glands
– Thyroid stimulating hormone (TSH) stimulates thyroid
gland to produce thyroid hormone
– Adrenocorticotropic hormone (ACTH) stimulates the
adrenal cortex to produce glucocorticoids
– Gonadotrophic hormones (FSH & LH) stimulate the
gonads to produce estrogen and testosterone
20.2 Hypothalamus and
Pituitary Gland
• Anterior Pituitary
– Three anterior pituitary hormones do not affect other
glands
• Prolactin (PRL) stimulates the mammary glands to
synthesize milk
• Melanocyte stimulating hormone (MSH) stimulates the
pigment producing melanocytes of the skin
• Growth hormone (GH) stimulates bone and muscle growth,
increases protein synthesis and fat metabolism
Hypothalamus and the Pituitary
20.3 Thyroid and Parathyroid Glands
• Thyroid Gland
– Produces:
• Triiodothyronine (T3) (four iodine atoms)
• Thyroxin (T4)
(three iodine atoms)
– Thyroid requires iodine to produce these hormones
• Iodine deficiency causes simple goiter
– T3 and T4 increase metabolic rate
• Stimulate most body cells to metabolize glucose
20.3 Thyroid and Parathyroid Glands
• Thyroid Gland
– Also Produces Calcitonin
• Calcium-regulating hormone
• Produced in response to increased blood calcium levels
• Causes uptake of calcium by bone
• Calcium is important in muscle contraction, nerve conduction,
and blood clotting
Regulation of Blood Calcium Level
20.3 Thyroid and Parathyroid Glands
• Parathyroid Glands
– Produce Parathyroid hormone (PTH)
• Causes an increase in blood calcium and a decrease in
blood phosphate
• Increases osteoclast activity and the reabsorption of calcium
by the kidneys
– Also stimulates activation of vitamin D needed for calcium
absorption in the digestive tract
• When blood calcium levels increase, PTH is shut off
20.4 Adrenal Glands
• The Adrenal Glands sit atop of the kidneys.
– The two parts of the adrenal gland function
independently
– Adrenal Medulla (outer portion)
• Under the control of the nervous system
– Adrenal Cortex (inner portion)
• Under the control of adrenocorticotropic hormone (ACTH)
– An anterior pituitary hormone
20.4 Adrenal Glands
• Adrenal Medulla
– Receives nerve impulses from the hypothalamus
– The adrenal medulla secretes two hormones:
• Epinephrine (adrenaline)
• Norepinephrine (NE)
– Epinephrine and norepinephrine bring about a shortterm response to stress (fight or flight response)
20.4 Adrenal Glands
• Adrenal Cortex
– Under the control of ACTH
– Two types of hormones
• Glucocorticoids
– Regulate carbohydrate, protein, and fat metabolism
leading to an increase in blood glucose level
• Mineralocorticoids
– Regulate salt and water balance leading to an increases
in blood volume and blood pressure
20.4 Adrenal Glands
• Adrenal Cortex
– Glucocorticoids
• Cortisol is the principal glucocorticoid hormone
• Actions
– Promotes breakdown of muscle proteins to amino acids
» Liver uses amino acids to make glucose
– Promotes metabolism of fatty acids, spares glucose
– Overall:
Promotes a rise in blood glucose
Beneficial under stress
• Cortisol is also anti-inflammatory
– Can also suppress the immune system
20.4 Adrenal Glands
• Adrenal Cortex
– Mineralocorticoids
– Aldosterone is the principal mineralocorticoid
hormone that targets the kidney
• Increases absorption of sodium, excretion of potassium
• Increases blood volume and pressure
• Controlled through the release of renin from the kidney
20.4 Adrenal Glands
• Adrenal Cortex
– Mineralocorticoids continued
• Renin is released when blood sodium levels and blood
pressure is low
• Activates angiotensinogen (a plasma protein) to angiotensin I
• Angiotensin I is converted to angiotensin II by enzyme in lung
capillaries
• Angiotensin II stimulates the adrenal cortex to release
aldosterone
• Effect: Angiotensin II constricts arterioles
Aldosterone causes the kidneys to reabsorb sodium
Blood pressure rises
Regulation of Blood Pressure
and Volume
20.4 Adrenal Glands
• Adrenal Cortex
– Mineralocorticoids continued
– Atrial Natriuretic Hormone (ANH)
• Produced by the right atrium (heart) as a result of stretch
– Represents an increase in blood volume
• Inhibits the release of aldosterone
• Results in natriuresis: excretion of sodium in the urine
• Water follows passively so blood volume and therefore
pressure decreases
Pancreas
• Pancreas is composed of two types of tissue
– Exocrine portion releases digestive enzymes
– Pancreatic islets are the endocrine portion of the
gland. The islets produce and secrete:
• Insulin
• Glucagon
Pancreas
• Insulin
– Released after eating
– Stimulates uptake of glucose by cells
• Especially muscle, liver, and adipose cells
• Decreases blood glucose
• Glucagon
– Released before eating when glucose is low
– Targets liver and adipose tissue
– Increases blood glucose
Regulation of Blood Glucose Level
20.6 Other Endocrine Glands
• Testes
– Under the influence of the gonadotropic hormones
– Produce androgens (e.g., testosterone)
– Responsible for male secondary sex characteristics
• Growth of penis and testes, beard growth, enlargement of
vocal folds and larynx
• Stimulates oil production by oil glands
• Involved in pattern baldness
• Increased muscle development
The Side Effects of
Anabolic Steroid Use
20.6 Other Endocrine Glands
• Ovaries
– Under the influence of the gonadotropic hormones
– Estrogen
• Stimulates growth of uterus and vagina
• Egg maturation
• Female secondary sex characteristics
– Breast development along with progesterone
– Fat deposition
– Progesterone
– Regulation of uterine cycle along with estrogen
20.6 Other Endocrine Glands
• Thymus Gland
– Secretes hormones involved with the maturation of Tlymphocytes hormones
• Pineal Gland
– Produces melatonin
• Involved with sleep/wake cycles and circadian rhythms
• Likely has a role in sexual development
20.6 Other Endocrine Glands
• Hormones from Other Tissues
– Leptin
• Produced by adipose tissue
• Stimulates satiety center in hypothalamus
– Prostaglandins
• Produced from arachidonic acid
• Act locally
• Many different prostaglandins-many effects
–
–
–
–
Muscle contraction in uterus
Mediate effects of pyrogens
Reduce gastric secretions
Inhibit platelet aggregation
20.6 Other Endocrine Glands
• Hormones from Other Tissues
– Growth factors
– Stimulate mitosis in tissues
– Some released in blood, others act locally
• Granulocyte and Macrophage Colony-Stimulating Factor
– Produced by many different tissues
– Causes bone marrow stem cells to produce granulocytes and
macrophages
• Platelet-Derived Growth Factor
– Wound healing
• Epidermal Growth Factor and Nerve Growth Factor
– Wound healing
• Tumor Angiogenesis Factor
– Formation of capillary networks to tumor cells
20.7 Pheromones
• Pheromones are chemical signals that act
between individuals
– Effects are better known in animals other than
humans
• Female moths release an attractant that acts on male moths
– In humans:
• Possible role in mate attraction
• Axillary secretions can affect the menstrual cycle
20.8 Disorders of the Endocrine
System
• Disorders of the Pituitary Gland
– Diabetes insipidus (DI)
• Posterior pituitary secretes too little ADH (antidiuretic
hormone)
– Large amounts of urine are produced resulting in dehydration
– Pituitary Dwarfism
• Too little growth hormone is secreted by the anterior pituitary
• Characterized by small stature but normal proportions
20.8 Disorders of the Endocrine
System
• Disorders of the
Pituitary Gland
– Gigantism
• Excess growth
hormone is produced
during childhood
• Gigantism also
promotes the
development of
diabetes mellitus
20.8 Disorders of the Endocrine
System
• Disorders of the Pituitary Gland
– Acromegaly
• Excess growth hormone in adulthood
• Long bones cannot grow, so the effect is noticeable in the
hands, feet, and facial bones
20.8 Disorders of the Endocrine
System
• Disorders of the Pituitary Gland
– Cushing Syndrome
• Excess production of ACTH (usually due to a tumor)
• Adrenal cortex then produces excess cortisol
– Protein is metabolized, fat is deposited in the midsection
20.8 Disorders of the Endocrine
System
• Disorders of the Thyroid
– Hypothyroidism
• Not enough thyroid hormone is produced
• In children, cretinism results if left untreated
– Individuals are short and stocky, mental retardation
results if treatment does not begin within the first two
months of life
• Myxedema can occur in adults
– Symptoms include lethargy, weight gain, hair loss, slow
heart rate, and puffy skin
• Treatment for both conditions in the administration
of thyroid hormones
20.8 Disorders of the Endocrine
System
• Disorders of the
Thyroid
– Goiter
• Caused by an enlarged
thyroid gland
• The thyroid gland is
being constantly
stimulated by TSH
• A lack of dietary iodine
makes the thyroid
unable to produce
sufficient T3 and T4
20.8 Disorders of the Endocrine
System
• Disorders of the
Thyroid
– Hyperthyroidism
• Oversecretion of thyroid
hormones
• Symptoms include
protruding eyes,
nervousness,
hyperactivity, and
abnormal heart rhythms
• Treatment may include
destruction of the
thyroid
20.8 Disorders of the Endocrine
System
• Disorders of the Parathyroid
– Insufficient parathyroid production results in a drop in
blood calcium levels.
– The body shakes from continuous muscle contraction
(tetany)
20.8 Disorders of the Endocrine
System
• Disorders of the Adrenal Glands
– Addison Disease
• Destruction of the adrenal cortex by the immune system
• Symptoms include weakness, weight loss, abdominal pain,
and a bronzing of the skin.
• The decreased production of mineral corticoids can affect
sodium and potassium levels, which can adversely affect the
heart.
20.8 Disorders of the Endocrine
System
• Diabetes Mellitus
– Cells cannot take up glucose
• As blood glucose rises, glucose and water are lost in the
urine
• Causes increased thirst, increased hunger
– A glucose tolerance test is used many times for
diagnosis
Glucose Tolerance Test
20.8 Disorders of the Endocrine
System
• Diabetes Mellitus
– Two types of Diabetes Mellitus
• Type 1- Insulin Dependent
– Lack of insulin- may be due to exposure to environmental agent
such as a virus
– May also be an autoimmune condition
– As cells break down fats for energy, ketones build up in blood
» Ketoacidosiscoma, death
– Insulin overdose- causes hypoglycemia, unconsciousness
» Immediate ingestion of glucose to counteract
20.8 Disorders of the Endocrine
System
• Diabetes Mellitus
– Two types of Diabetes Mellitus
• Type 2 Diabetes Mellitus
– Insulin-resistant
– Obesity- adipose tissue produces a substance that
impairs insulin receptor function
– Insulin levels are often low, and cells may not have
sufficient insulin receptors
– Controlled by diet, exercise, medications
– Long term complications of diabetes mellitus
• Blindness, kidney disease, cardiovascular disorders