Exam 1 Study Guide

• Teleological vs. Mechanistic reasoning:

  • Teleological approach: thinking about a physiological event in terms of its adaptive significance
  • Explains the "why"
  • Example: Why do red blood cells transport oxygen? Because cells need oxygen and red blood cells bring it to them
  • Mechanistic approach: examines physiological processes
  • Explains the "how"
  • Example: How do red blood cells transport oxygen? Oxygen binds to hemoglobin in the red blood cells
• Homeostasis:

  • Does not necessarily mean equilibrium
  • Dynamic steady state: materials are constantly moving back and forth between compartments, but there is no net movement between compartments
  • Equilibrium implies identical composition
• Control systems in homeostasis:

  • All local control systems have three parts and are isolated to local tissues and cells
  • Long-distance reflex controls are more complex (systemic control)
  • Negative feedback loops are homeostatic
  • Positive feedback loops are not homeostatic
  • Feedforward control: some reflexes in the body can predict a change about to occur and start a response loop in anticipation
• Functional Compartments of the Body:

  • On top of body cavities, there are many fluid-filled anatomical compartments
  • Hollow organs make their own compartment
  • Lumen of an organ is the hollow interior
  • 3 fluid compartments: Extracellular fluid, Intracellular fluid
• Biological Membranes:

  • Main functions: Physical isolation, Regulation of exchange with the environment, Communication between the cell and its environment, Structural support
  • Makeup of the cell membrane varies widely
  • Categories of proteins: Integral proteins, Peripheral proteins
• Osmosis and Tonicity:

  • ICF and ECF will always be in osmotic equilibrium
  • Chemical disequilibrium and electrical disequilibrium
  • Osmolarity: the number of osmotically active particles per liter of solution
  • Tonicity: describes a solution and how it would affect cell volume if a cell were placed in it
  • Comparing tonicity: Hypotonic, Hypertonic, Isotonic
• Diffusion:

  • Diffusion is a passive process
  • Net movement of molecules occurs until concentration is equal everywhere
  • Diffusion is rapid over short distances but slower over long distances
• Protein Mediated Transport:

  • Structural proteins, Enzymes, Receptors, Transport Proteins
  • Channel proteins and Carrier proteins
  • Facilitated diffusion
  • Primary Active Transport: energy from ATP
  • Secondary Active Transport: uses potential energy stored in gradient of one molecule to push the other molecule against their concentration gradient
• Cell to Cell Communication:

  • Signal Pathways
  • Novel signal molecules
  • Modulation of Signal Pathways
  • Homeostatic reflex pathways
• Sensory neuron transmits electrical and chemical information
• Endocrine reflex: stimulus acts directly on endocrine cell, which is the sensor and integrating center
• Integrating center receives information about the regulated variable and can initiate the appropriate response
• In endocrine reflex, the integrating center is the endocrine cell
• In neural reflex, the integrating center is in the central nervous system
• Output signals in the nervous system are electrical and chemical signals transmitted by efferent neuron
• Output signals in the endocrine system are hormones
• Targets are the cells or tissues that carry out the response
• In neural pathway, targets can be muscle, endocrine or exocrine gland, adipose tissue
• In endocrine pathway, targets are cells that have the proper receptor
• There are many levels of response, including cellular response, tissue or organ response, and general systemic response
• Neural reflex specificity: neuron terminates on a single target cell or a limited number of adjacent cells
• Endocrine reflex specificity: most of the body's cells are exposed to the hormone, but the response depends on which cells have a receptor
• Nature of the signal in neural reflex: electrical signal passes through the neuron, then neurotransmitters carry the signal from cell to cell
• Nature of the signal in endocrine reflex: chemical signals are secreted in the blood for distribution throughout the entire body
• Speed of neural reflex: very rapid
• Speed of endocrine reflex: much slower
• Duration of neural reflex: short
• Duration of endocrine reflex: longer than neural
• Stimulus intensity in neural reflex: each signal is identical in strength, frequency of signaling must be increased for increased strength
• Stimulus intensity in endocrine reflex: correlated with the amount of hormone secreted
• Simple Endocrine reflex example: High plasma glucose → Insulin is released from beta cell → insulin facilitates glucose uptake in adipose tissue/muscle cells
• Simple neural reflex example: A tap to the knee activates mechanoreceptors → quadriceps muscles in legs contract and kick
• Hormones are secreted by a cell or group of cells, can be endocrine gland, neurons, or even the immune system
• Hormones are secreted into the blood or into the external environment (pheromones)
• Hormones are transported to distance targets and exert effect at low concentrations
• Categories of hormones based on connection to the hypothalamus: controlled by the hypothalamus/anterior pituitary, synthesized in hypothalamus and released from the posterior pituitary, independent of the hypothalamus
• Cellular mechanism of action of a hormone: all hormones bind to cell receptors and initiate biochemical response, but this may look different with different hormones and tissues
• Hormones are degraded into inactive products by enzymes, mainly in the liver and kidneys, with varying half-lives
• Main effects of hormones include controlling rates of enzymatic reactions, controlling transport of ions or molecules across membranes, and controlling gene expression and protein synthesis
• Main functions of hormones: metabolism, regulation of internal environment (temperature, water balance, ions), reproduction, growth and development