1. Compare the mechanisms of the endocrine and nervous systems.
Endocrine system—signaling molecules release into the bloodstream by endocrine cells reaching all locations in the body
Hormones
Slow acting
Long lasting
Nervous system—neurons transmit information between specific locations
Neurons
Fact acting
Short lasting
2. Explain the general mechanism of how hormones work.
Hormones and other signaling molecules trigger responses by binding to specific receptor proteins in or on target cells
Hormones maintain homeostasis, mediate responses to environmental stimulus, regulate growth, development, and reproduction
3. Distinguish between endocrine glands and exocrine glands.
Endocrine glands secrete hormones directly into the surrounding fluid
(endo= within)
Exocrine glands have ducts that carry secreted substances
(exo= out of) example: salivary glands
4. Distinguish between hormones, local regulators, and neurotransmitters.
Hormone= in multicellular organisms, one of many types of secreted chemical that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the body to change their functioning
Local regulators= a secreted molecule that influences cells near where it is secreted
(short distances by diffusion)
Paracrine: target cells lie near the secreting cells
Autocrine: the secreted molecules act on the secreting cells itself
Neurotransmitters= a molecules that is released from the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft, and binds to the postsynaptic cell, triggering a response
(central to sensetation, memory, cognition, and movement)
5. List the three major classes of hormones.
Polypeptide (protein and peptides)
Insulin: made up of two polypeptide chains
Water soluble: cannot pass through the plasma membrane of cells
Amines
Epinephrine or thyroxine: single amino acid either tyrosine or tryptophan
Water soluble: cannot pass through the plasma membrane of cells
Steroids:
Cortisol: lipids that contain 4 fused carbon rings
Lipid soluble: nonpolar; can pass through plasma membrane
6. Know the difference between a water-soluble hormone and lipid-soluble hormone, and compare the two general mechanisms by which these hormones trigger changes in target cells.
Water soluble hormone—cannot pass through the plasma membrane of cells
Secreted by exocytosis, travel freely in the bloodstream, and bind to the cell-surface signal receptors
Binds to a signal receptor protein on the surface of a target cell
This interaction triggers events that lead to either a change in cytoplasmic function or a change in gene transcription in the nucleus
-Signal Transduction: the series of changes in cellular proteins that converts the extracellular chemical signals to a specific intracellular response
Lipid soluble hormone—can pass through the plasma membrane
Diffuse out across the membranes of endocrine cells and travel in the bloodstream bound to transport proteins
Penetrates the target cell’s plasma membrane and binds to an intracellular signal receptor, either in the cytoplasm or nucleus
The hormone receptor complex acts as a transcription factor, typically activating gene expression
7. Explain why different target cells exposed to the same hormone may respond in different ways. Know an example.
Target cells with the same receptor exhibit different responses if they have different signal transduction pathways and or effector proteins
Responses of target cells may also differ if they have different receptors for the hormone
Lipid soluble hormones often exert different effects on different target cells
Example: Epinephrine, the primary “fight-or-flight” hormone, produces different responses in different target cells. The epinephrine receptor of a liver cell is called a β type receptor to regulate enzymes in glycogen metabolism.
8. Distinguish between alpha and beta cells in the pancreas and explain how their antagonistic hormones
