Understanding the Endocrine System: Hormones, Functions, and Classification, Slides of Biology

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The Endocrine System

Human Biology

 Hormones:

 Come from endocrine glands

 Circulate in the blood stream

 Act on specific cells in the body

Endocrine Functions: Hormones

 Access to every cell

 Each hormone acts only on specific cells

(target cells)

 Only specific cells have receptors for specific

hormones

 Endocrine control slower than nervous

system

 Endocrine and nervous systems interact

Endocrine System Characteristics

Steroid Hormone Action on a

Target Cell

Figure 13.

 Steroid Hormones:

 Lipid soluble, chemically derived from cholesterol  Enter target cells  Activate specific genes to produce specific proteins  Slower acting than nonsteroid hormones, minutes to hours

Classification of Hormones:

Steroid

Nonsteroid Hormone Action on a

Target Cell

Figure 13.

 Nonsteroid hormones:

 Water soluble  Bind to receptors on target cell membranes  Work through intermediate mechanisms to activate existing enzymes  Faster action than steroid hormones, seconds to minutes

Classification of Hormones:

Nonsteroid

Example of a Negative Feedback Loop:

Homeostasis

Location of Major Endrocrine Organs

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.

Figure 9.

Hormones of the Pituitary Gland

Table 13.

Hypothalamus and the Anterior

Pituitary Gland

Figure 13.

 Anterior pituitary

 Connection to hypothalamus: releasing and inhibiting hormones from hypothalamus travel to pituitary through pituitary portal system  Hormones  ACTH: stimulates adrenal cortex  TSH: acts on thyroid gland  FSH, LH, Prolactin: related to control of reproductive cycles and lactation  Growth Hormone: widespread effects on body

Hypothalamus and the Anterior

Pituitary Gland

 Posterior pituitary

 Connection to hypothalamus: hormones made in hypothalamus, stored in posterior pituitary  Hormones: nonsteroidal  Antidiuretic hormone (ADH): conserves water in kidneys, regulates water balance in body  Oxytocin: causes uterine contractions during labor and milk ejection through neuroendocrine reflex

Hypothalamus and the Posterior

Pituitary Gland

 Gigantism: hypersecretion of growth

hormone

 Pituitary Dwarfism: hyposecretion of growth

hormone

Pituitary Disorders

Pituitary Gigantism

 Structures: islets of Langerhans

 Hormones: nonsteroidal

 Glucagon: made by alpha cells, raises blood sugar  Insulin: made by beta cells, lowers blood sugar

Pancreas: Endocrine Functions

Location of Major Endrocrine Organs

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.

Figure 9.

Roles of Insulin and Glucagon in

Regulating Blood Glucose

Figure 13.

Location of Major Endrocrine Organs

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 9.

Figure 9.

 Adrenal cortex

 Secretion: mediated through hypothalamus- pituitary secretions  Hormones: steroidal  Glucocorticoids: cortisol – blood glucose regulation  Mineralocorticoids: aldosterone – sodium/fluid/urine

Adrenal Glands: Cortex

Secretion of Cortisol

Figure 13.10

 Adrenal medulla: neuroendocrine organ

 Secretion: sympathetic nervous system  Hormones: nonsteroidal  Epinephrine and Norepinephrine: enhance function of sympathetic nervous system (Fight or flight)

Adrenal Glands: Medulla

Roles of the Hypothalamus and Adrenal Glands in the Stress Response

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings^ Slide 9.31

Figure 9.12

 Secretion: mediated through hypothalamus-

pituitary secretions

 Steroidal hormones:

 Thyroxine (T 4 ) and Triiodothyronine (T 3 ): both regulate production of ATP from glucose, affects metabolic rate  Calcitonin: lowers blood calcium levels

Thyroid Gland

Negative Feedback Control of

Thyroxine Secretion

Figure 13.13