A/P 2 chapter 17

Endocrine glands, lack ducts, and product is released directly into the blood

synthesis and release of hormones.  Controls many activities of the body: homeostasis, controlling reproductive activities, regulating development, growth, metabolism and digestion

They both release ligands in response to stimuli that bind to target cells

Cells with a specific receptor for a hormone

a ligand is a chemical substance (hormone or neurotransmitter) that is released by the endocrine or nervous system

it affects two specific locations by means of neurons and neurotransmitters

The endocrine system has widespread effect and uses blood for distribution of hormones

It has a rapid effect, but it is short lasting

Slow effect but longer lasting

Neurons release neurotransmitters into a synaptic cleft to stimulate their target cells

hormones are secreted by endocrine cells.  The hormones enter the blood and travel throughout the body to reach the target cells

• Maintaining homeostasis of blood composition and volume
• Controlling reproductive activities
• Regulating development, growth, and metabolism
• controlling digestive processes

• epithelium-derived endocrine cells and connective tissue
• organization of cells differ between glands, but they have an extensive blood supply

• Pineal gland
• Pituitary gland
• thyroid gland
• Parathyroid gland
• Adrenal gland

• hypothalamus
• skin
• thymus
• heart
• stomach
• liver
• pancreas
• small intestine
• kidneys
• gonads

• Hormones produced: melatonin
• Function: helps regulate the body's circadian rhythm

• Hormones produced: Oxytocin (OT), Antidieuretic Hormone (ADH)
• Functions: Uterine contractions; breast milk release (OT)
• Fluid balance (ADH)

• Thyroid-stimulating hormone (TSH)
• Prolactin (PRL)
• Follicle-stimulating hormone (FSH)
• Luteinizing hormone (LH)
• Adrenocorticotropic hormone (ACTH)
• Growth Hormone (GH)

stimulates thyroid gland to release thyroid hormone

Breast milk production

Development of gametes (and follicle in female)

Development of gametes (and ovulation in female)

stimulates adrenal cortex to release corticosteroids

stimulates cell growth and division

• Anterior pituitary release thyroid stimulating hormone.
• TSH stimulates thyroid gland to release Thyroid hormone (TH)

• Blood glucose levels increase
• increased blood glucose stimulates pancreas to release insulin

• Sympathetic nervous system increases in activity
• Sympathetic preganglionic axons stimulate adrenal medulla to release epinephrine and norepinephrine

• Steroid hormones
• Protein hormones
• Biogenic amines

• from cholesterol, therefore lipid soluble
• hormones from gonads and adrenal cortex

• from amino acids, therefore water-soluble
• consists of 3 groups: polypeptides, oligopeptides, and glycopeptides

• monoamines, modified amino acids
• hormones of adrenal medulla and thyroid hormone

• Large group of signaling molecules that do not circulate within the blood. They have a local effect
• may either affect the cell that produced the hormone (autocrine stimulation) or neighboring cells (paracrine stimulation

eicosanoids

• do not dissolve in blood plasma
• require carrier proteins that ferry the hormone through the blood (also offer protection from degradation)
• hormone must detach to be able to exit the blood and affect the target cell
• most lipid-soluble hormone is in bound state (90-99.9%)

• dissolves in blood plasma, and are transported easily
• many bind to protein carriers for protection

Effect of hormones is directly related to the amount of hormone presented in blood, this is to prevent potential clinical consequences

• hormone synthesis
• hormone elimination

• occurs in endocrine gland
• if rate of synthesis and release increase than the concentration of hormone w/in the blood is greater and vice versa

• degradation by enzymes usually in liver
• elimination by kidneys
• uptake of hormone by target cells

• depends on composition of hormone
• a specific hormone generally has different types of target cells

• hormone slips easily inside the cell through the cell membrane
• forms hormone-receptor complex (either in cytosol or in nucleus)
• binds to hormone-response element (in nucleus)
• initiates transcription of mRNA
• translation of mRNA results in a protection that may alter the cell activity of cell structure

Cannot cross the cell membrane, interacts with receptors on the outside