Chapter 9 Endocrine System

The Endocrine System
Chapter 9
1. Overview
a. Second control system (nervous system is first)
b. Chemical messengers (hormones)- released into the blood; usually long term control
c. Hormones control several major processes
i. Reproduction
ii. Growth and development
iii. Mobilization of body defenses
iv. Maintenance of much of homeostasis
v. Regulation of metabolism
2. Hormones
a. Overview
i. Hormones are produced by specialized cells
ii. Cells secrete hormones into extracellular fluids
iii. Blood transfers hormones to target site
iv. These hormones have specific effects on these cells
b. Chemistry – hormones classified as:
i. Amino acid/protein based
ii. Steroids- made from cholesterol
iii. Prostaglandins- made from highly active lipids
c. Mechanism of action
i. Hormones affect only certain tissues or organs (target cells, tissues, or organs)
ii. Hormone binding alters cellular activity
iii. Direct gene action- indirectly be a second messenger system
1. Diffuse through the plasma membrane of target cells
2. Enter the nucleus
3. Bind to specific protein within the nucleus
4. Bind to specific sites on the cell’s DNA
5. Activate genes that result in synthesis of new proteins
iv. Second messenger system; the hormone:
1. Hormone binds to a membrane receptor
2. Does not enter the cell
3. Sets off a series of reactions that activates an enzyme
4. Catalyzes a reaction that produces a second-messenger molecule
5. Oversees additional intracellular changes to promote a specific response
v. How hormone release is controlled
1. Hormone levels in the blood are mostly maintained by negative feedback
2. A stimulus or low hormone levels in the blood triggers the release of more hormone
3. Hormone release stops once an appropriate level in the blood is reached
4. Release triggered by
a. Levels of other hormones
b. Levels of certain ions in the blood
c. Nerve impulses, usually sympathetic nervous system
3. Overview of the system
a. Spread throughout the body
b. Sometimes part of other systems
c. List of major organs
i. Pituitary gland
ii. Thyroid gland
iii. Parathyroid glands
iv. Adrenal glands
v. Pineal gland
vi. Thymus gland
vii. Pancreas
viii. Gonads (ovaries and testes)
4. Pituitary gland
a. Size
b. Hangs from
c. Protected by
d. Two functional lobes
e. Referred to as
f. Anterior pituitary hormones
i. Targets are non-endocrine
1. GH =
2. PRL =
ii. Tropic hormones: affect other endocrine glands
1. TSH =
2. ACTH =
3. Gonadotropins
a. FSH =
b. LH =
5. Hormones of the anterior pituitary
a. Growth hormone
i. General
ii. Major effects
iii. Plays a role
iv. Causes
v. Disorders
1. Pituitary dwarfism
2. Gigantism
3. Acromegaly
b. Prolactin
i. In women
ii. In men
c. Adrenocorticotropic hormone
i. Regulates
d. Thyroid-stimulating hormone
i. Influences
e. Gonadotropins
i. Follicle-stimulating hormone
1. In ovaries
2. In testes
ii. Luteinizing hormone
1. In females
2. In males
6. Pituitary/hypothalamus relationship
a. Releasing and inhibiting hormones
b. Hypothalamus hormones
i. Oxytosin
1. Stimulates
2. Causes
ii. Antidiuretic hormone
1. Inhibits
2. Causes
3. AKA
iii. Transported to posterior pituitary via
Anatomy & Physiology – Chapter 9 Part B
Endocrine System
1. Pituitary Gland
a. Size of a pea
b. Hangs by a stalk from the hypothalamus in the brain
c. Protected by the sphenoid bone
d. Has two functional lobes:
i. Anterior pituitary- glandular tissue
ii. Posterior pituitary- nervous tissue
e. Often called the “master endocrine gland”
Anterior pituitary
2. Six anterior pituitary hormones
3. Two affect non-endocrine targets- growth hormone (GH), prolactin
4. Four stimulate other endocrine glands (tropic hormones): thyroid-stimulating horomone (thyrotropic), adrenocorticotropic hormones, two gonadotropic hormones
5. Growth hormone:
a. General metabolic hormone
b. Major effects are directed to growth of skeletal muscles and long bones
c. Plays a role in determining final body size
d. Causes amino acids to be built into proteins
e. Causes fats to be broken down for a source of energy
f. GH disorders
i. Pituitary dwarfism results from hyposecretion of GH during childhood
ii. Gigantism results from hypersecretion of GH during childhood
iii. Acromegaly results from hypersecretion of GH during adulthood (bones get thicker because epiphyseal plates already fused)
g. Prolactin (PRL):
i. Stimulates and maintains milk production following childbirth
ii. Function in males is unknown
iii.
h. Adrenocorticotropic hormone (ACTH)
i. Regulates endocrine activity of the adrenal cortex
i. Thyroid-stimulating hormone
i. Influences growth and activity of the thyroid gland
ii.
j. Gonadotropic hormones regulate hormonal activity of the gonads:
k. Follicle-stimulating hormone (FSH):
i. Stimulates follicle development in ovaries
ii. Stimulates sperm development in testes
l. Luteinizing hormone (LH):
i. Triggers ovulation of an egg in females
ii. Stimulates testosterone production in males
m. Hormone releasing is regulated by releasing and inhibiting hormones produce by the hypothalamus
n. Hypothalamus produces two hormones transported to the posterior pituitary:
o. Oxytocin:
i. Stimulates contractions of the uterus during labor, sexual relations, and breastfeeding
ii. Causes milk ejection in nursing woman
p. Antidiuretic hormone (ADH):
i. Inhibits urine production by promoting water reabsorption by the kidneys
ii. In large amounts, causing vasoconstriction leading to increased blood pressure
iii. Also known as vasopressin
Pituitary
6. Thyroid gland
a. Found
b. Consists of
c. Produces two hormones
i. Thyroid hormone (TH)
1. Major metabolic hormone
a. Thyroxine (T4)
b. Triiodothyronine (T3)
ii. Calcitonin
1. Decreases by
2. Antagonistic to
7. Parathyroid gland
a. What and where:
b. Secretes parathyroid hormone (PTH) which:
i. Stimulates
ii. Stimulates
iii. Raises
iv. See Figure 9.10
8. Adrenal glands
a. Location:
b. Each has two anatomical & physiological regions:
i. Adrenal cortex:
1. Mineralocorticoids (aldosterone)
a. Produced
b. Regulate
c. Regulate
d. Target organ
e. Stimulated by
f. Inhibited by
2. Glucocorticoids
a. Produced
b. Promote
c. Help resist
d. Released
3. Sex hormones
a. Produced in
b. Small amounts
c. Mostly androgens but some estrogens
4. Disorders
a. Addison’s disease
b. Hyperaldosteronism
c. Cushing’s syndrome
d. Masculinization
ii. Adrenal medulla
1. Produce two similar hormones (catecholamines)
a. Epinephrine (adrenaline)
b. Norepinephrine (noradrenaline)
c. Fight or flight
9. Pancreatic islets (islands of endocrine cells; pancreas is also exocrine)
a. The pancreas is a mixed gland and has both endocrine and exocrine functions
b. Insulin- allows glucose to cross plasma membranes into cells from beta cells
c. Glucagon- allows glucose to enter the blood from alpha cells
d. The hormones are antagonists that maintain blood sugar homeostasis
e. Disorders: diabetes
i. Type 1 – juvenile diabetes (probably born with), can’t produce insulin, needs insulin their whole life, seen a few years after birth
ii. Type 2 – onset diabetes, from overuse of pancreas, obesity, may be able to cure with diet and excersize
10. Pineal gland
a. Found on the third ventricle of the brain
b. Secretes melatonin:
i. Helps establish the body’s wake and sleep cycles
ii. Believed to coordinate the hormones of sexual maturation and fertility in human
11. Thymus gland
a. Located posterior to the sternum
b. Largest in infants and children
c. Produces thymosin:
i. Matures some types of white blood cells
ii. Important in developing the immune system
12. Gonads
a. Ovaries
i. Produce eggs
ii. Produce two groups of steroid hormones:
1. Estrogen
a. Stimulate the development of secondary female characteristics
b. Mature female reproductive organs
c. Along with progesterone:
i. Promote breast development
ii. Regulate menstrual cycle
2. Progesterone
a. Acts with estrogen to bring about the menstrual cycle
b. Helps in the implantation of an embryo in the uterus
c. Helps prepare breasts for lactation
b. Testes
i. Produce sperm
ii. Produce androgens, such as testosterone
1. Responsible for adult make secondary sex characteristics
2. Promotes growth and maturation of male reproduction system
3. Required for sperm cell production
13. Other hormone-producing organs/tissues
14. Placenta – nurturing structure for developing fetus; attached to umbilical cord
a. Produces
b. Some hormones
c. Produces human chorionic gonadotropin (hCG)
15. Developmental aspects of the endocrine system
a. Most organs
b. Menopause
c. Problems
d. Growth hormone
e. Endocrine glands