chapter 9 - science with mrs. cooper -...

Lecture Presentation by Patty Bostwick-Taylor

Florence-Darlington Technical College

Chapter 9

The Endocrine System

© 2015 Pearson Education, Inc.


Intro to the Endocrine System

§ Chief Complaint:8-year-old girl with excessive thirst, frequent urination, and weight loss.

§ History: Cindy Mallon, an 8-year-old girl in previously good health, has noticed that, in the past month, she is increasingly thirsty. She gets up several times a night to urinate, and finds herself gulping down glass-fulls of water. At the dinner table, she seems to be eating twice as much as she used to, yet she has lost 5 pounds in the past month. In the past three days, she has become nauseated, vomiting on three occasions, prompting a visit to her pediatrician.


Lab Results

At the doctor's office, blood and urine samples are taken. The following lab results are noted: § blood glucose level = 545 mg/dl (normal = 50 - 170 mg/dl) § blood pH level = 7.23 (normal = 7.35 - 7.45) § urine = tested positive for glucose and for acetone /

acetoacetate (i.e. ketone bodies) (normally urine is free of glucose and ketone bodies)

Why is her blood-glucose level elevated? Why is she always thirsty?

The Endocrine System

§ Second controlling system of the body after N.S. § Uses chemical messengers (hormones) that are

released into the blood § Hormones control several major processes:

§ Reproduction § Growth and development § Mobilization of body defenses § Maintenance of much of homeostasis § Regulation of metabolism


Hormone Overview § Hormones are produced by specialized cells § Cells secrete hormones into extracellular fluids § Blood transfers hormones to target sites § These hormones regulate the activity of other cells


Control of Hormone Release

§ Hormone levels in the blood are maintained mostly by negative feedback

§ A stimulus or low hormone levels in the blood triggers the release of more hormone

§ Hormone release stops once an appropriate level in the blood is reached



Feedback System – Blood Glucose

§  https://www.fastday.com/wp-content/uploads/2014/04/insulin1.jpg

Hormone Action

§ Hormones affect only certain tissues or organs (target cells or target organs)

§ Target cells must have specific protein receptors

§ Hormone binding alters cellular activity


The Chemistry of Hormones § Hormones are classified

chemically as § Amino acid–based, which

includes: § Proteins § Peptides § Amines

§ Steroids—made from cholesterol (lipid) § Prostaglandins—made from

highly active lipids that act as local hormones


Concept Link


Hormone Action

Hormones arouse cells, or alter cellular activity. Typically, one or more of the following occurs: 1.  Changes in plasma membrane permeability or

electrical state 2.  Synthesis of proteins, such as enzymes 3.  Activation or inactivation of enzymes 4.  Stimulation of mitosis 5.  Promotion of secretory activity


The Chemistry of Hormones

§ Hormones act by two mechanisms: 1.  Direct gene activation 2.  Second-messenger system


Direct Gene Activation (Steroid Hormone Action) 1.  Steroid hormones diffuse through the plasma

membrane of target cells 2.  Steroid hormones enter the nucleus 3.  Steroid hormones bind to a specific protein within

the nucleus 4.  Hormone-receptor complex binds to specific sites

on the cell’s DNA 5.  Certain genes are activated that result in… 6.  Synthesis of new proteins



Figure 9.1a Mechanisms of hormone action.

Steroid hormone Cytoplasm Nucleus

Receptor protein

Hormone-receptor complex

DNA

mRNA

New protein

Plasma membrane of target cell

1

(a) Steroid hormone action

2 3

4

5

6

Slide 1




1


Slide 2




Receptor protein 1


2

Slide 3




Receptor protein


1


2 3

Slide 4




Receptor protein


DNA

1


2 3

4

Slide 5




Receptor protein


DNA

mRNA

1


2 3

4

5

Slide 6




Receptor protein


DNA

mRNA

New protein


1


2 3

4

5

6

Slide 7

Second-Messenger System (Nonsteroid Hormone Action) 1.  Hormone (first messenger) binds to a membrane

receptor 2.  Activated receptor sets off a series of reactions

that activates an enzyme 3.  Enzyme catalyzes a reaction that produces a

second-messenger molecule (such as cyclic AMP, or cAMP)

4.  Oversees additional intracellular changes to promote a specific response in the target cell



Figure 9.1b Mechanisms of hormone action.

(b) Nonsteroid hormone action


Receptor protein

Nonsteroid hormone (first messenger)

Cytoplasm

Enzyme

ATP

cAMP Second messenger

Effect on cellular function, such as glycogen breakdown

1 2

3

4

Slide 1




Receptor protein


Cytoplasm

1

Slide 2




Receptor protein


Cytoplasm

Enzyme

1 2

Slide 3




Receptor protein


Cytoplasm

Enzyme

ATP


1 2

3

Slide 4





Receptor protein


Cytoplasm

Enzyme

ATP


Effect on cellular function, such as glycogen breakdown

1 2

3

4

Slide 5

Endocrine Gland Stimuli

§ The stimuli that activate endocrine glands fall into three major categories:

1.  Hormonal 2.  Humoral 3.  Neural


Hormonal Stimuli of Endocrine Glands

§ Most common stimulus § Endocrine organs are activated by other hormones § Example:

§ Anterior pituitary hormones travel to target glands, such as the thyroid gland, to prompt the release of a particular hormone, such as thyroid hormone



Figure 9.2a Endocrine gland stimuli.

(a) Hormonal stimulus

The hypothalamus secretes hormones that…

Hypothalamus

1

…stimulate the anterior pituitary gland to secrete hormones that…

Anterior pituitary gland

Thyroid gland

Adrenal cortex

Gonad (testis)

…stimulate other endocrine glands to secrete hormones

2

3

Humoral Stimuli of Endocrine Glands

§ Changing blood levels of certain ions and nutrients stimulate hormone release § Humoral indicates various body fluids, such as blood

and bile § Examples:

§ Parathyroid hormone and calcitonin are produced in response to changing levels of blood calcium levels

§  Insulin is produced in response to changing levels of blood glucose levels



Figure 9.2b Endocrine gland stimuli.

(b) Humoral stimulus

Capillary blood contains low concentration of Ca2+, which stimulates…

Capillary (low Ca2+

in blood)

Thyroid gland (posterior view)

Parathyroid glands

Parathyroid glands

PTH

…secretion of parathyroid hormone (PTH) by parathyroid glands)

1

2

Neural Stimuli of Endocrine Glands

§ Nerve impulses stimulate hormone release § Most are under the control of the sympathetic

nervous system § Examples:

§ The release of norepinephrine and epinephrine by the adrenal medulla



Figure 9.2c Endocrine gland stimuli.

(c) Neural stimulus

Preganglionic sympathetic fiber stimulates adrenal medulla cells…

CNS (spinal cord)

Preganglionic sympathetic fibers

Medulla of adrenal gland

Capillary

…to secrete catecholamines (epinephrine and norepinephrine)

1

2

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