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OBJECTIVES:
- Explain why the endocrine system is so closely related to the nervous system.
- Distinguish between an endocrine gland and an exocrine gland.
- Define the term hormone and explain its general characteristics.
- Distinguish between a steroidal and non-steroidal hormone, in terms of composition and action.
- Locate the following endocrine glands (organs) on a diagram: hypothalamus, pituitary, pineal gland, thyroid, parathyroids, thymus, adrenals, pancreas, ovaries, testes.
- Name the three endocrine glands (see above) that are actually divided into two endocrine glands with different functions.
- For each of the glands listed in #5 & #6 above, name the hormone(s) they secrete, identify the target organ of each hormone, and the effect of each hormone.
- Name the "master" of the anterior pituitary gland.
- Define the term gonadotropin , name the two gonadotropins secreted by the anterior pituitary gland, and distinguish between them according to their actions.
- Explain how the posterior pituitary gland does not produce hormones, but does secrete them.
- Name the gland that requires iodine to produce most of its hormones.
- Describe how calcium levels are maintained in the blood.
- Name the two hormones that work together to regulate water and electrolyte levels in the blood and therefore regulate blood pressure.
- Describe how glucose levels are maintained in the blood.
- Explain why the thymus gland decreases in size as we age.
Objectives (continued)
- Name the gland (hormone) whose production is stimulated by sunlight.
- Define the term gonad , list the primary gonads in both sexes, and name the hormones that target those gonads.
- Explain what is meant by "secondary sexual characteristics", name the hormone that causes their development in both sexes, and list target organs.
- Name the hormones secreted by the ovary, distinguish which particular portion of the ovary secretes each, and name target organs and actions of those hormones.
- Distinguish between dwarfism, giantism, and acromegaly.
- Explain why so few cases of cretinism are seen today.
- Compare and contrast cretinism, myxedema, Grave’s Disease, and goiter.
- Distinguish between Addison’s Disease and Cushing’s Syndrome.
- Compare and contrast the two types of the disease Diabetes Mellitus.
- Describe seasonal affective disorder (SAD) in terms of cause, symptoms, and treatment.
V. CONTROL OF HORMONAL SECRETIONS
The overall scheme for the release of most hormones is presented in Figure 13.13, page 491 in the text. First of all, the HYPOTHALAMUS secretes "releasing hormones" that target the anterior pituitary gland.
A. The ANTERIOR PITUITARY GLAND (which hangs from the base of the brain) may then secrete 6 different hormones:
- Human Growth Hormone (HGH) a. controls growth of the body; b. targets the bone, muscle and adipose tissue.
- Thyroid stimulating hormone (TSH)
a. controls the secretion of hormones by the thyroid gland; b. targets thyroid gland.
- Adrenocorticotropic Hormone (ACTH)
a. controls the secretion of hormones by the adrenal cortex; b. targets the outer portion of the adrenal gland (cortex).
- Prolactin (PRL)
a. stimulates the production of milk by the mammary glands; b. targets the mammary glands.
- Follicle Stimulating Hormone (FSH)
a. response depends upon sex: m In females, FSH stimulates maturation of an ovarian follicle and ovum; m In males, FSH stimulates the maturation of sperm in the testes; b. A gonadotropin = targets the primary sex organs (ovary & testis).
- Luteinizing Hormone (LH) a. response depends upon sex: m In females, LH causes ovulation; m In males, LH causes secretion of testosterone. b. A gonadotropin; targets ovaries & testes.
V. Control of Hormonal Secretions (continued):
B. The POSTERIOR PITUITARY GLAND (See Fig 13.10, page 490)
- is located behind the anterior pituitary gland;
- is continuous with nerve fibers (supraopticohypophyseal tract) of the hypothalamus;
- does not actually produce hormones (they are produced by the hypothalamus), but stores them until it is stimulated to release them;
- secretes 2 hormones: See Table 13.5, page 496.
a. Anti-Diuretic Hormone (ADH) :
m targets the kidney tubules (DCT); m causes the kidney tubules to reabsorb water back into the bloodstream, and therefore controls water balance and blood pressure.
b. Oxytocin (OT) :
m targets uterine smooth muscle and breasts; m causes uterine muscle contraction and milk production.
C. The THYROID GLAND : See Fig 13.16 & 13.17, page 506 & 507.
- is located below larynx and around trachea;
- is involved in iodine uptake (in order to produce thyroxine (T (^) 4) & triiodothreonine (T 3 ) below);
- produces 3 hormones when stimulated by TSH:
a. Thyroxine (T (^) 4) & Triiodothreonine (T (^) 3) : m increase basal metabolic rate by stimulating cellular oxygen use to produce ATP; m regulate metabolism.
b. Calcitonin : m release is triggered by an increase in blood calcium levels; m targets bone cells (inhibits osteoclast activity) & kidney tubules (causes secretion of calcium into urine); m Therefore, causes a decrease in blood calcium and phosphate levels to normal.
E. Adrenal Glands (continued)
b. The ADRENAL CORTEX :
m is located in the outer portion of the adrenal glands; m produces many steroid hormones when stimulated by ACTH:
- aldosterone regulates water and electrolyte levels in the blood (regulates blood pressure);
See Fig 13.29, page 504.
- cortisol regulates glucose metabolism;
- sex hormones that supplement those of the ovary and testis.
F. The PANCREAS : See Fig 13.32, page 507.
a. is located behind the stomach on the left side of abdomen; b. functions as both an exocrine gland (digestion) and endocrine gland (see below); c. contains endocrine organs called Islets of Langerhans which produce 2 hormones: See Fig 13.33, page 507.
- Insulin :
m is produced by Beta cells FHOOV LQ,VOHWVRILangerhans; m decreases blood glucose levels (i.e. moves glucose from bloodstream into cells and promotes glycogen formation [liver/muscle]).
- glucagon :
m is produced by Alpha cells FHOOV LQ,VOHWVRILangerhans; m increases blood glucose levels (i.e. causes breakdown of glycogen and release of glucose into bloodstream).
d. See Fig 13.34, page 508 to review how these two hormones regulate glucose homeostasis in the blood.
V. Control of hormonal secretions (continued)
G. The THYMUS GLAND :(See Fig 13.2, page 481.)
- is located in the mediastinum region behind sternum;
- produces a hormone called thymosin that affects the maturation of lymphocytes (T-cells);
- plays an important role in lymphatic system and immunity;
- decreases in size as we age.
H. The PINEAL GLAND :(See Fig 13.2, page 481)
- is attached to the thalamus of the brain stem;
- secretes a hormone called melatonin : a. production is stimulated by daylight (circadian rhythm); b. affects moods, emotions, etc.
I. The OVARIES:
- An ovarian follicle (and ovum) start to mature each month following puberty under the influence of FSH.
a. The developing follicle secretes estrogen : m develops and maintains female secondary sexual characteristics; targets:
- hair follicles;
- mammary glands/ breasts;
- adipose tissue.
- LH causes the follicle to rupture and release the ovum (ovulation); the follicle becomes the corpus luteum. a. The corpus luteum secretes progesterone: m prepares the uterus for implantation of the zygote.
J. The TESTES:
- FSH causes the production of sperm.
- LH causes the production of testosterone: a. develops and maintains male secondary sexual characteristics; targets: m hair follicles; m muscle, bone; m larynx.
CHAPTER 13: ENDOCRINE SYSTEM
VII. ABNORMAL HORMONAL LEVELS:
A. Growth Hormone
- Pituitary Dwarfism = hyposecretion of GH during growth years. a. slow bone growth & closing of epiphyseal plates before normal height is reached; b. Treatment = oral GH therapy.
- Pituitary giantism = hypersecretion of GH during growth years. a. abnormal increase in the length of long bones.
- Acromegaly = hypersecretion of GH during adulthood. a. Bones of hands, feet, cheeks, and jaw thicken; b. Soft tissues also grow. c. See CA 13.2, page 493.
B. ADH
- Diabetes insipidus = hyposecretion of ADH. a. diuresis, dehydration, thirst; b. ADH in nasal spray.
C. Thyroid Hormones
- Cretinism = hyposecretion of T3/T4 during fetal life and infancy. See Fig 13.9, page 498. a. dwarfism & mental retardation; b. prevention = newborn testing; c. treatment = oral thyroid therapy.
- Myxedema = hyposecretion during adulthood. a. edema, slow heart rate, low body temp, dry hair & skin, muscular weakness, lethargy, weight gain; b. Oral thyroid hormones reduce symptoms.
- Grave’s Disease = an autoimmune disorder that causes growth of thyroid and hypersecretion of thyroid hormones, with no negative feedback. a. enlarged thyroid (2-3x larger); b. peculiar edema of the eyes (bulging); c. increased metabolic rate, heat intolerance, increased sweating, weight loss, insomnia, tremor, nervousness. d. treatment = surgical removal, use of radioisotopes to destroy some of the thyroid. and anti-thyroid drugs to block synthesis of the hormones. e. See Fig 13.20, pg 498.
VI. ABNORMAL HORMONAL LEVELS:
E. Pancreatic (Islet) Hormones (See CA 13.4, pg 509)
- Diabetes Mellitus
b. Type II /NIDDM (90%)
m patients > 40 years, m overweight, m hypertensive, m (smokers); m Problem is usually with receptors on target cells; m Controlled by diet, exercise, and weight loss; m Drug Diabeta(glyburide) may help stimulate insulin secretion RI FHOOV LIORZOHYHOVRILQVXOLQLVWKHFDXVH
- Hyperinsulemia
F. Melatonin
- Seasonal Affective Disorder & Jet Lag
CH 13: ENDOCRINE SYSTEM : HORMONE SUMMARY TABLE (outline page 272)
HORMONE SECRETED BY
WHAT GLAND?
TARGET(S)? EFFECT(S) AT
TARGET SITE
Growth Hormone (GH) anterior pituitary bone, muscle, fat
growth of tissues
Thyroid Stimulating Hormone (TSH)
anterior pituitary thyroid secrete hormones
Prolactin (PRL) anterior pituitary mammary glands
produce milk
Adrenocorticotropic hormone (ACTH)
anterior pituitary adrenal cortex secrete hormones
Latinizing Hormone (LH) anterior pituitary In males: interstitial cells in testes; in females: mature ovarian follicle
males: testosterone secretion
females: ovulation
Follicle stimulating hormone (FSH)
anterior pituitary males: semi- iferous tubules of testes; females: ovarian follicle
males: sperm production females: follicle/ovum maturation
Triiodothreonine (T (^) 3) & Thyroxine (T 4 )
thyroid all cells regulates metabolism
ALDOSTERONE adrenal cortex kidney tubules reabsorption of water and Na (blood pressure)
CORTISOL adrenal cortex all cells glucose metabolism
ESTROGEN ovarian follicle secondary sex organs
development and maintenance
PROGESTERONE corpus luteum uterine endometrium
preparation for implantation (thickens, glandular, vascular)
