Endocrine Study Guide Essay

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Chapter 14: Endocrine System
Lecture Notes
A. Endocrine Glands
1. Functions
a. Communication system (slow compared to the nervous system)
b. Regulates many body functions through its secretion of hormones (metabolism, water balance, growth and reproduction, temperature)
2. Location (Figure 14-1)
3. Difference between endocrine and exocrine glands
a. Exocrine glands: secrete mucus, sweat, digestive enzymes into ducts that empty contents to the exterior of the body
b. Endocrine glands: called “ductless” glands because they secrete hormones directly into the blood (needing no ducts)
B. Hormones
1. Classification of hormones
a. Protein (protein-related)
b. Steroids
2. Target tissues or target organs (Figure 14-2, A): named because hormones are “aimed” at these sites (like an arrow)
3. Hormone receptors
a. Location
i. Membrane receptors (most hormones) ii. Intracellular receptors (steroids, thyroid hormones)
c. Account for specificity (“lock-and-key,” precise fit)
d. Second messenger
i. Intermediate chemical (links hormone stimulation to cellular response) ii. Cyclic AMP, for instance, is activated in response to hormone stimulation
4. Control of hormone secretion
a. Negative feedback control (Figure 14-3)
i. Follow the steps of insulin secretion ii. Increasing blood glucose stimulates insulin release iii. Insulin causes blood glucose to decrease iv. Decreased blood glucose “shuts off” the release of insulin
b. Biorhythms
i. Causes rhythmic alteration in the secretion of hormones ii. Length of rhythms differ (e.g., monthly female cycle, circadian rhythm)
Clinical Correlates Chronopharmacology Jet lag Night shift fatigue/other physiology effects Drug dosing schedule (e.g., prednisone) should mimic biorhythms
c. Control by CNS
i. Influence of the hypothalamus ii. Autonomic nervous system activity
Clinical Correlates Stress responses… sympathetic/“fight-or-flight”/“paradoxical fear”
C. The Pituitary Gland (Hypophysis) (Figure 14-4)
1. Location
a. Immediately inferior to the hypothalamus
b. Sella turcica of sphenoid bone
2. Pituitary gland (hypophysis) and the hypothalamus (Figure 14-4, A)
a. Hypothalamic releasing hormones control the secretion of the hormones by the anterior pituitary
b. Hypothalamic-hypophyseal portal system (Figure 14-4, B)
i. Note connecting capillaries ii. Carry releasing hormones from the hypothalamus to the anterior pituitary
3. Anterior pituitary gland (adenohypophysis) (Figure 14-4, A, Table 14-1)
a. “Master gland”: exerts controlling influence on many other glands
b. Major lobes
i. Anterior pituitary gland (adenohypophysis) ii. Posterior pituitary gland (neurohypophysis)
a. Learn it PRO prolactin ATHletes ACTH Got gonadotropins 
 (FSH, LH) To TSH GROW growth hormone
b. Growth hormone (somatotropic hormone)
1. Target: primarily the musculoskeletal system causing growth
2. Secreted during periods of sleep and fasting
3. Exerts powerful metabolic effects: elevates blood glucose
Clinical Correlates Giantism, dwarfism Dawn phenomenon in diabetes mellitus
c. Prolactin (PRL)
1. Stimulates milk production by the mammary glands (breasts)… see Chapter 27 for lactation
2. Also called lactogenic hormone
3. Role of PRL in males is unknown
d. Tropic hormones: aimed at other glands
1. Thyroid stimulating hormone (TSH): stimulates the thyroid gland
2. Adrenocorticotropic hormone (ACTH): stimulates the adrenal cortex
3. Gonadotropins (FSH and LH)… Chapter 26 (Reproduction)
4. Posterior pituitary gland (Figure 14-4, C)
a. Called the neurohypophysis
b. Hormones are synthesized in the hypothalamus and stored in the posterior pituitary gland
c. Hormones
i. Antidiuretic hormone (ADH)
a. Target: kidney (causes kidney to reabsorb water, thereby decreasing urine production… antidiuresis)
b. Signal for release (symptoms of dehydration… low blood volume and concentrated blood)
c. Also called vasopressin because it constricts blood…