BIO 202 Endocrine System (chapter 17)

1. Gap Junctions
2. Neurotransmitters
3. Paracrines
4. Hormones

1. join single-unit smooth muscle, cardiac muscle, epithelial, and other cells to each other
2. enable cells to pass nutrients, electrolytes, and signaling molecules directly from the cytoplasm of one cell to the cytoplasm of the next through pores in their plasma membranes

1. released by neurons
2. diffuse across a narrow synaptic cleft and bind to receptors on the surface of the next cell

1. secreted by one cell, diffuse to nearby cells in the same tissue, and stimulate their physiology
2. a.k.a. local hormones

1. chemical messengers that are transported by the bloodstream
2. stimulate physiological responses in cells of another tissue or organ, often a considerable distance away
3. hormones produced by the pituitary gland in the head act on organs as far away as the pelvic cavity

Glands, tissues, and cells that secrete hormones

Endocrinology

The brain, heart, small intestine, bones, and adipose tissue

1. exocrine glands secrete their products by a duct onto an epithelial surface while endocrine glands are ductless and release their secretions into the bloodstream
2. exocrine secretions have extracellular effects such as the digestion of food while endocrine secretions have intracellular effects (they alter cell metabolism)

1. Endocrine glands, serve to pick up and carry away their hormones.
2. These vessels are very permeable type called fenestrated capillaries which have large pores to easily uptake matter fromt he gland tissue

1. Liver cells
2. they do not fit exocrine secretions because they are not released by way of ducts or onto epithelial surfaces and they do not fit endocrine secretions because they are not hormones
3. they secrete bile into ducts that lead ultimately to the small intestine, they secrete hormones into the blood, and secrete albumin and blood-clotting factors directly into the blood as well

1. nervous system communicates by electrical impulses and neurotransmitters, but the endocrine system communicates by means of hormones
2. nervous system uses electrical and chemical communication, but the endocrine system uses only chemical communication
3. nervous system releases neurotransmitters at synapses at specific target cells, but endocrine system releases hormones into the bloodstream for general distribution throughout the body
4. nervous system usually has relatively local, specific effects, but the endocrine system sometimes has very general, widespread effects
5. nervous system reacts quickly to stimuli (ms), but endocrine system reacts more slowly (seconds to days)
6. nervous system stops quickly when the stimulus stops, but the endocrine system may continue responding long after the stimulus stops
7. nervous system adapts relatively quickly to continual stimulation, but the endocrine system adapts relatively slowly, may respond for days to weeks

Its long fiber

Secrete hormone into the bloodstream and at a point often remote from its origin, the hormone leaves the bloodstream and enters or bind to its target cells

Growth hormone, epinephrine, and thyroid hormone