A&P 1: module 9

endocrine system

endocrine system

complex network of glands and organs that use hormones released into the blood to regulate various functions within the body including growth, metabolism, and reproduction; plays a crucial role in maintaining homeostasis by secreting hormones directly into the bloodstream to act on distant target cells

endocrine system vs endocrine system

NS: considered primary control system of body because of its ability to respond quickly to stimuli - uses electrical impulses to communicate, first line of response in controlling body functions; PS: secondary control system. uses hormones released into the bloodstream to communicate ; overlap in both systems

direct signaling

occurs between cells at gap junctions between two adjacent cells of the same type. allow cells to communicate so closely that they functionally react as one cell. occur to help coordinate the ciliary movement in epithelial cells and allow synchronous contractions of the cardiac muscle tissue

autocrine signaling

takes place within the same cell. An autocrine is a chemical that elicits a response in the same cell that secreted it

paracrine signaling

occurs in cell-to-cell communication of different cells within the same tissue. Cells release local chemical messengers into the extracellular environment for cells close by, allowing cells close to each other to know what each cell is doing to coordinate growth and metabolism rates. Chemicals released by paracrine communication are also called local hormones

synaptic signaling

occurs when chemical messengers are released to a target cell but at very close range to the receptors, not into the bloodstream. These chemical messengers are called neurotransmitters. Signaling for these chemical messengers occurs via electrical propagation along an axon, as studied in the nervous system

endocrine signaling

occurs when a chemical messenger is released by one tissue and enters the bloodstream to change the cellular activities in other tissues. The chemicals in this case are called hormones. Once in the bloodstream, hormones interact with cells throughout the body. Endocrine signaling is the type of signaling that will be discussed in this module. Cells that can react to a hormone have specific receptors, which combine with the hormone in a lock-and-key manner. Therefore, cells can respond to one hormone and not to another, depending on the cell's surface receptors.

2 types of glands

endocrine and exocrine glands

endocrine glands

ductless, secreting their contents directly into the bloodstream for distribution throughout the body

exocrine glands

have ducts that secrete their contents into and epithelial surface (ex: salivary glands)

endocrine organs

secrete hormones that chemically regulate body functions; include hypothalamus, pituitary gland, pineal gland, thyroid gland, parathyroid glands, adrenal glands, and pancreas

gonads

testes and ovaries; release gametes (sperm or oocytes) and also release hormones (testosterone or estrogen/progesterone) into the bloodstream; has endocrine and exocrine functions

pancreas

releases the hormones insulin and glucagon into the bloodstream to control blood glucose levels; long organ that lies transversely in the abdomen between the kidneys and near the duodenum; has exocrine and endocrine functions; its exocrine function involves releasing digestive enzymes into the small intestine to aid in digestion

hormone

defined as a chemical produced by one set of cells that affects a different set of cells called target cells; chemical messengers that influence the metabolism of the recipient cell and sent through the body produced and utilized by the endocrine system; all have a specific organ/gland of origin, a specific target organ/gland or organs/glands, and a specific action; must be synthesized or modified by the endocrine cell to be secreted; most are proteins; 3 main categories based on their chemical structure: amino acid derivatives, peptide hormones, and lipid derivatives

amino acid derivatives

made from a single amino acid; amino acids join together to form proteins; AA derivatives include derivatives of tyrosine and tryptophan

tyrosine

derivatives include thyroid hormones and catecholamines (epinephrine, norepinephrine, and dopamine); can be found in sources such as meat, dairy, and fish

tryptophan

is an amino acid that is converted to melatonin and secreted by the pineal gland; can be found in turkey, chocolate, oats, milk, cottage cheese, and peanuts

peptide hormones

made from long chains of amino acids, not just one amino acid; most are secreted as inactive prohormones which are converted into active hormones before or after they are secreted

glycoproteins

more than 200 amino acids long and have a carbohydrate as part of their structure; include TSH, LH, FSH, EPO, and inhibin

short polypeptides and small proteins

the second group made from chains of amino acids but without a carbohydrate side chain; include a large variety of hormones all of which are secreted by the hypothalamus, pituitary gland, heart, digestive tract, pancreas, parathyroid gland, thyroid (calcitonin), and adipose tissue

lipid derivatives

include two classes of lipids: eicosanoids and steroid hormones

eicosanoids

lipids derived from a 20-carbon fatty acid called arachidonic acid; include hormones like leukotrienes, prostaglandins, and prostacyclins, which are compounds that play critical roles in inflammation and immune responses

leukotrienes

mediate allergic and asthmatic reactions

prostaglandins

involved in pain, fever, and inflammation regulation

prostacyclins

act as strong vasodilators and inhibitors of platelet aggregation

steroid hormones

derived from cholesterol, which is a type of lipid

hormone receptor

receives message a hormone sends; specific protein located either inside the cell or within the cell membrane; will process the message by initiating other signaling events or cellular mechanisms that result in the target cells response; recognize molecules with specific shapes and side chain groups

intracellular hormone receptor

protein complexes located inside the cell, either in the cytoplasm or the nucleus; They bind to lipid-soluble (hydrophobic) hormones, such as steroid hormones and thyroid hormones, that can easily diffuse through the cell membrane

transcription

cellular process or transcribing the DNA code to messenger RNA (mRNA); the mRNA moves to the cytosol and directs protein synthesis by ribosomes called translation

translation

process of turning mRNA into a protein; these hormones directly change the activity and structure of the target cell by influencing the types and quantities of proteins present in the cell

hydrophilic

water soluble; hormones that are generally able to diffuse through the lipid bilayer of the cell membrane and must therefore pass on their message to a receptor located at the surface of the target cell, which is then passed along via intracellular signaling molecules