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# Phys2 Lect 2

Question | Answer |
---|---|

Pressure | Force per unit area |

Flow | volume transferred per unit time (5L/min) |

Resistance | Opposition to flow |

Velocity | Flow per cross-sectional area per unit time |

How is BL FLOW related to pressure difference and resistance? | PROPORTIONAL to pressure difference. INVERSELY PROPORTIONAL to resistance. Q = (P1-P2)/R |

How can the pressure difference be increased? how will it affect flow? | Activating B1 receptors in the ventricular myocytes will generate a greater initial pressure which will increase the pressure difference. **This will Increase flow. |

How can the resistance be increased? how will it affect flow? | Resistance in a BL vessel occurs via alpha1 receptors and vasoconstriction. **this will decrease flow |

Cardiac Output equation | CO = Paorta/TPR **TPR: total peripheral resistance (from the body) |

Resistances relationship to radius and length? | INVERSELY proportional to r^4. PROPORTIONAL to L. **This is energetically beneficial b/c we do not need massive ANS symp output to generate change (small change in r = large inc in Resistance). |

Effect on Flow: Increased r | INCREASES flow. (decreases Resistance) |

Effect on Flow: Decreased r | DECREASES flow. (increases Resistance) |

Effect on Flow: Increased L | DECREASES flow. (increases Resistance) |

Effect on Flow: Decreased L | INCREASES flow. (decreased Resistance). |

TPR (Total Peripheral Resistance) is the sum of all resistances. How do organs being in series and parallel affect this? | Series: all the resistances are added (Rt=R1+R2+R3). Parallel: (1/Rt = 1/R1 + 1/R2 + 1/R3) this greatly decreases the TPR which makes it much easier on the heart. otherwise the heart would have to be much larger. |

Vasodilation's effect on flow | Increasing the radius, thus increasing flow by decreasing resistance. |

Vasoconstriction's effect on flow | Decreasing the radius, thus decreasing flow by increasing the resistance. |

Where does the main resistance to flow occur? | Arterioles. **they have high ratio of smooth muscle and contain precapillary sphincters. This creates the greatest resistance and causes a large drop in pressue (100mmHg to 40mmHg) |

What is the flow in the capillaries? | Almost 0 |

At constant flow, what is the relationship between velocity and radius? | Velocity is INVERSELY proportional. **Therefore velocity is at its lowest in the capillaries (<1cm/sec) b/c combined, they have the LARGEST total cross-sectional area (csa). The aorta has the lowest totatl csa and the HIGHEST velocity (23cm/sec) |

Increasing cross sectional area for a given BL flow will do what to the veloctiy? | DECREASE it |

decreasing cross sectional area for a given BL flow will do what to the veloctiy? | INCREASE it |

Bernoulli Principle | Total energy is conserved between potential energy and kinetic energy. *Kinetic energy: velocity. *Potential energy: BP |

How will viscosity affect flow? | Increasing the viscosity (via increased hematocrit) will increase the reistance and decrease flow. **Blood dopping can be dangerous for this reason. |

Three different types of flow? | 1.Laminar (arteries, arterioles, venules, veins). 2.Turbulent (ventricles, stenosed arteries). 3.Single-file (capillaries). |

Plasma skimming and Laminar flow. | In laminar flow, the middle is where the fastest flow occurs b/c there is more endothelial resistance closer to the vessel walls. **Plasma skimming occurs b/c most hematocrit will remain in the middle. |

Turbulent flow | Promoted by high BL flows. Fluid and cells tumble. **If heard in arteries: BRUITS (usually due to atherosclerosis) |

Can high flow rates affect laminar flow? | YES. if flow gets very high, laminar flow will change to turbulent flow (Bruits). **Stenosis will narrow the vessel (cross sectional area and radius) which will increase the velocity leading to turbulent flow. |

Classic location of Bruits in Carotids? | At the bifrication of the Carotid Artery. |