Exam 1

• A receptor may be temporarily unavailable to respond to stimulation even when neurotransmitters are available. This is referred to as: Receptor desensitization
• Which of the following homeostatic control systems anticipate fluctuations in a variable and speed up the response even before it is altered? Feedforward mechanisms
• As part of signal transduction in the G-protein coupled receptor pathways, adenylyl cyclase is responsible for conversion of ATP molecules to cyclic AMP (cAMP).
• The function of a neuron’s cell body is to: integrate information to generate electrical signals
• Depolarization occurs when the membrane potential becomes less negative than the resting membrane potential.
• In a generic homeostatic reflex arc, what senses changes in either the internal or external environment? Receptor
• Pathophysiology

  The study of how and why normal function goes wrong, i.e. disease.
• Layers of the body:

  Cells -> tissues -> organs -> organ system -> organism
• Types of Differentiated Cells:

  1. Muscle (myocytes)
  2. Neural (neurons)
  3. Epithelial
  4. Connective tissue
• Voluntary Muscle

  Skeletal
• Involuntary muscle

  Cardiac & smooth
• Organ


  A collection of tissues joined in a structural unit to serve a common function
• The organism coordinates the activities of the bodily systems to maintain a stable internal environment
• In mammals with a closed vascular system, the extracellular fluids are compartmentalized to enable exchange of nutrients and waste.
• • Total Body Water (TBW) is 60% of body weight
  • Intracellular fluid is 2/3 of TBW
  • Extracellular fluid (ECF) is 1/3 of TBW
  • Interstitial fluid is 80% of ECF
  • Plasma is 20% of ECF
• Inside the cell, the cell/plasma membrane separates intracellular fluid from extracellular fluid. Outside the cell, the capillary wall separates interstitial fluid from blood plasma.
• The compositions of the plasma and the interstitial fluid are very similar, with a key difference being that the plasma contains proteins while the interstitial fluid contains very few
• A biological system that directly links a stimulus with a response is called a reflex arc
• Negative feedback


  End product of a process reduces the effect of the stimulus
• Feedforward mechanisms


  Anticipate changes
• Positive feedback


  Accelerates a process leading to an "explosive" system; uterine contractions during childbirth
• Example of positive feedback:

  Ovulation; Estrogen leads to more estrogen release
• Example of positive feedback:

  Action potential; Na+ entry leads to Na+ channels opening
• Example of positive feedback:

  Muscle contraction; Ca2+ entry leads to Ca2+ release in the cell
• Hormone

  Secreted by endocrine cells into the blood stream
• Neurotransmitter

  Released by a neuron to affect a muscle, gland or nerve cell. Travels through synaptic cleft (10-20 nm)
• Paracrine agent

  Acts on nearby cells
• Autocrine agent

  Released into the interstitial fluid and acts upon the cell that secreted it
• Amphipathic

  Having polar and nonpolar regions
• Since there are no chemical bonds between the fatty acid chains, there can be a lot of lateral movement within the membrane. This is called membrane fluidity
• Functions of a plasma membrane

  1. Acting as a selective barrier
  2. Playing a role in communication by detecting chemical signals
  3. Linking adjacent cells by membrane junctions
  4. Anchoring cells to the extracellular matrix
• Membrane functions are primarily carried out by membrane proteins
• Integral membrane proteins are amphipathic and span the entire membrane
• Peripheral membrane proteins are polar and do not span the membrane
• Transmembrane proteins fall into which category of protein?

  Integral proteins
• In biological systems ligand binding is typically reversible
• Substances are said to move down hill by diffusion
• Diffusion is driven by the concentration gradient
• A cell membrane is 5 nm thick and a eukaryotic cell diameter is 10-100 um
• Diffusion of oxygen over a few microns happens in < 1 second to move it by diffusion over 10 cm would take months