ch13 endocrine

8/12/2019 Ch13 Endocrine

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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

The Endocrine System

chemical messages (hormones) that are released into

the blood

Hormones control several major processes

Reproduction - gametogenesis, sexual desire

Growth and development

Maintenance of homeostasis - salts, water, blood

pressure, RBCs

Regulation of metabolism - digestion, stress

responses




Endocrine System Characteristics

Access to every cell

Each hormone acts only on specific cells(target cells) that have matching receptors

Endocrine control slower than nervous

system

Endocrine and nervous systems interact




Classification of Hormones: Steroid

Steroid Hormones:

Lipid soluble, derived from cholesterol

Enter target cells

Activate specific genes to produce proteins

Slower acting: minutes to hours




Steroid Hormones:

QuickTime™ and aCinepak decompressor

are needed to see this picture.

How does a steroid hormone cause changes in cells?




Hormones: Nonsteroid

Amino acid-based hormones

proteins, peptides, amines

Water soluble

Bind to receptors on target cell surface Work via second messengers to activate

existing enzymes

Faster action: seconds to minutes




Non-Steroid Hormones:

How does a non-steroid hormone cause changes in cells?

QuickTime™ and aCinepak decompressor

are needed to see this picture.


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Control of Hormone Release

Hormone levels are

maintained by negativefeedback

Low hormone levels or

a stimulus triggers therelease of more hormone

Hormone release stops

once an appropriate levelin the blood is reached



1. Hormonal Stimulus

Endocrine glands are

activated by other

hormones Most common signal-

coordinates response of

several glands

Figure 9.2a



2. Humoral Stimulus

Changing blood

levels of certain ionsstimulate hormone

release

PTH - to raise Ca++

Calcitonin - to

decrease Ca++

Insulin - to decrease

glucose

Figure 9.2b



3. Neural Stimulus

Nerve impulses

stimulate hormonerelease

Usually by sympathetic

nervous system

Figure 9.2c



Location of Major Endocrine Organs

Figure 9.3



Pituitary - Hypothalamus Relationship

Release of anterior pituitary

hormones is controlled by

hormones from hypothalamus

Hypothalamus produces two

hormones that are stored in the

posterior pituitary

posterior pituitary releases

hormones when neurally

stimulated by hypothalamus



Hormones of the Posterior Pituitary

Oxytocin

Stimulates contractions ofthe uterus during labor

Causes milk ejection

Antidiuretic hormone (ADH)

Can inhibit urine production

In large amounts, causes

vasoconstriction




Hormones of the Anterior Pituitary

Six anterior pituitary

hormones; common

characteristics:

Proteins (or peptides)

Act through second-messenger systems

Regulated by

hormonal stimuli,

mostly negative

feedback




Growth Hormone (GH)

General metabolic hormone

Major effects are directed to growth ofskeletal muscles and long bones

Causes amino acids to be built into proteins

Causes fats to be broken down for a source of

energy




Functions of Other Anterior Pituitary

Hormones

Prolactin (PRL) Stimulates milk production following childbirth

Function in males is unknown

Adrenocorticotropic hormone (ACTH)

Regulates the adrenal cortex (affects salt,

glucose levels)

Thyroid-stimulating hormone (TSH)

Influences thyroid gland




Functions of Other Anterior Pituitary

Hormones

Gonadotropic hormones - appear at puberty

Follicle-stimulating hormone (FSH)

Stimulates follicle development (ovaries)

and sperm development (testes)

Luteinizing hormone (LH)

Triggers ovulation

Stimulates testosterone production in males




Thyroid Gland

Found at the base of the

throat

Produces two hormones

Thyroid hormone -

controls metabolism

Calcitonin - affects

Ca++ levels in blood




Calcitonin

Decreases blood

calcium levels bycausing calcium

deposition in bone

(in children)

Antagonistic to PTH,

parathyroid hormone

Figure 9.9




Adrenal Glands

Two glands

Cortex – outerglandular region in

three layers

Medulla – inner

neural tissue region

Sits on top of thekidneys




Hormones of the Adrenal Cortex

Mineralocorticoids (mainly aldosterone)

Regulate mineral content in blood, water,and electrolyte balance via kidney action

Glucocorticoids (cortisone, cortisol)

Promote normal cell metabolism

Help resist long-term stressors

depress inflammatory response

Androgen, estrogen



R l f th H th l d Ad l




Pancreatic Islets

Figure 9.13

Insulin – allows

glucose to cross

plasma membranesinto cells

Glucagon – allows

glucose to enter the blood

Somatostatin

pancreas is a mixed gland

islet cells produce hormones:

Di b




Diabetes

Diabetes mellitus - “sweet siphon”

Type I - lack of insulin

juvenile

Type II - resistant to effects of insulin Adult onset

Oth H S



C i ht © 2006 P Ed ti I bli hi B j i C i

Other Hormone Sources

Thymus: thymosin and thymopoietin, assist

maturation of T lymphocytes Pineal gland: melatonin

Heart: atrial natriuretic hormone (ANH)

Digestive system: gastrin, secretin,

cholecystokinin

Kidney: erythropoietin, renin

ch13 endocrine

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