CH16: ENDOCRINE SYSTEM

What are the major functions of the endocrine system system?

• Communication

• Control

• Maintaining homeostasis

Compare & contrast how the nervous and endocrine system control bodily functions

• Effects of endocrine system can take hours/days

• Effects of nervous system can be immediate

What is a hormone?

Small chemicals secreted by endocrine glands into the bloodstream.

Are Amino acid/peptide hormones hydrophilic or hydrophobic?

Hydrophilic

Are Steroid (lipid) hormones hydrophilic or hydrophobic?

Hydrophobic

What hormone is amino acid-based but is not hydrophilic?

Thyroid hormones (they are hydrophobic)

What is a free hormone?

Freely associate with water, typiclaly amino acid-based

What is a bound hormone?

Hormones that do not associate with water.

Where are receptors for hydrophilic hormones located?

Within the target cell membrane

Where are the receptors for hydrophobic hormones located?

Within the cytosol of the target cell

What are receptors?

Proteins that hormones bind to

What are the endocrine organs?

• Anterior pituitary gland

• Thyroid gland

• Parathyroid gland

• Adrenal cortices

• Endocrine pancreas

• Thymus

• Ovaries

• Testes

What is a neuroendocrine organ, and examples?

An organ that has nervous tissue, but secretes hormones (neurohormones)

• Hypothalmus

• Pineal Gland

What is a secondary organ?

An organ that produces hormones but is not a part of the endocrine system

What occurs during cAMP? (List steps in order)

• The hydrophilic hormone binds to the plasma membrane receptor, G-protein splits.

• G-protein activates adenyl cyclase

• Adenyl cyclase catalyzes the formation of cAMP, 2nd messenger

• cAMP activates protein kinase A

• Protein kinase A then changes the activity or shape of a protein to have a wider range of effects in the cell.

What kind of hormones utilize cAMP? Hydrophilic or Hydrophobic?

Hydrophilic

What is the main purpose of cAMP?

Acts as an intracellular second messenger to relay signals from outside the cell to inside the cell to trigger cellular responses.

How do hydrophobic hormones bind to intracellular receptors? (List steps)

• Hormone diffuses into the cell

• Hormone binds to the intracellular receptor, then enters the nucleus

• Hormone receptor interacts with DNA to initiate cellular change

What are the effects of hormone actions?

• Stimulating secretion

• Activating or inhibiting enzymes

• Stimulating or inhibiting mitosis

• Opening or closing ion channels

• Activating or inhibiting gene transcription

Hormonal Stimuli

Endocrine cells increase or decrease their secretion in response to other hormones

Humoral stimulu

Endocrine cells responding to concentration of a certain compound or ion in the blood or extracellular fluid

Neural Stimuli

Endocrine cells responding to signals from the nervous system

Where is the hypothalamus located?

Within the brain, connected to pituitary gland by the infundibulum

What is the anterior pituitary made of?

Glandular epithelium (hormone-secreting)

What is the posterior pituitary made of?

Nervous tissue

What kind of hormones does the hypothalamus produce?

Neurohormones

Does the posterior pituitary produce hormones?

No, just stores then releases.

What hormones are produced by the hypothalamus?

Antidiuretic hormone (ADH) and Oxytocin

Whats the function of ADH?

• Increases amount of water retained by kidneys

• Decreases urine production

What’s the function of Oxytocin?

• Milk production

What is the primary target for ADH?

The kidneys

What is the primary target for Oxytocin?

Mammary glands and uterus

What hormones are secreted by the anterior pituitary?

TSH, ACTH, Prolactin, LH, and FSH

What are the effects, targets, and control pathways for TSH?

• Effects: Stimulates the development of the thyroid gland

• Target: Thyroid gland

• Control Pathway: Secretion triggered by TRH, Inhibited by Somatostatin

What are the effects, targets, and control pathways for ACTH?

• Effects: Stimulates the development of the adrenal glands

• Target: Adrenal Cortex

• Control Pathway: Secretion stimulated by CRH

What are the effects, targets, and control pathways for Prolactin?

• Effects: Stimulates the growth of mammary glands, lactation, and maintenance of lactation

• Target: Mammary glands

• Control Pathway: Stimulated by infant suckling, inhibited by dopamine

What are the effects, targets, and control pathways for LH?

• Effects: Stimulates production of testosterone, estrogens, and progesterone

• Targets: Male and female gonads

• Control Pathway: Secretion stimulated by GnRH

What are the effects, targets, and control pathways for FSH?

• Effects: Stimulates the testes to produce chemicals that bind to testosterone/In females, it triggers estrogen production

• Targets: Gonads

• Control Pathway: Secretion stimulated by GnRH

What are the effects, targets, and control pathways for GH?

• Effects: Regulates and controls growth

• Targets: Skeletal/cardiac muscle, adipose, liver, cartilage, bone

• Control Pathway: Stimulated by GHIH

Where is the thyroid gland located?

In the anterior neck

What hormones are secreted by the Thyroid gland?

Thyroid hormones and Calcitonin

Where are the parathyroid glands located?

On the posterior thyroid gland

What are the effects of thyroid hormones (T3/T4)

• Regulation of metabolic rate and thermoregulation

• Promotion of growth and development

• Synergy with the sympathetic nervous system