homeostasis

• Things that receptors exhibit

  specificity, saturation, and competition; subject to allosteric modulation
• Signals can be

  chemical or electrical

  short or long distance

  lipophobic or lipophilic

  have intracellular or membrane receptors
• Intracellular receptors can either be in the cytosol or the nucleus
• Lipophilic and lipophobic signal molecules can bind to membrane receptors, but only lipophilic cells can diffuse into the cell to bind to cytosolic or nuclear receptors
• Membrane receptors are integral membrane proteins that bind peptide hormones and lipophobic signals.
• Cell membrane receptors usually activate a secondary messenger
• Intracellular receptors bind steroid or thyroid hormones
• Intracellular receptors can act like transcription factors
• G proteins are turned on when bound to GTP and is off when bound to GDP
• Examples of secondary messengers are cAMP, cGMP, IP3/DAG, and calcium
• Cannon's Postulates are role of the automated nervous system in homeostasis, tonic activity, antagonistic control, and effects of chemical signals based on receptors
• Systemic homeostatic control can be from the nervous system or endocrine system
• the hammer knee kick is an example of a simple neural reflex
• Insulin being released from beta cells in the pancreas is an example of a simple endocrine reflex, decreasing blood sugar level
• Glucagon is released from alpha cells when blood sugar levels are low, which leads to an increase in glucose levels
• Systemic control is also known as long distance control
• Negative feedback is when the output can also work as an input
• Insulin and glucagon are antagonists that help maintain blood sugar
• Negative feedback controls homeostasis, blood sugar, temperature, and blood pressure
• Positive feedback loops include breast feeding, the blood clotting cascade, and uterine labor contractions
• Hormones are signals released by the endocrine system
• Gap junctions allow cells to be glued together and ions pass through the gap junctions
• activity is either upregulated and downregulated
• upregulation occurs when cell response increases as more receptors are put on the surface
• downregulation is when cell response is blocked and it stops. receptors are pulled down into the cytosol
• Chemical signals are either lipophilic or lipophobic
• Ligand gated ion channels are an example of a membrane receptor