Page 1: Arteries

• Arteries measure blood pressure only in this part of the circulatory system.

• Tunica Interna:

  • Internal layer of arteries.

• Tunica Media:

  • Middle layer; thicker smooth muscle layer.

  • Smooth muscle can contract to decrease lumen diameter, leading to increased blood pressure without stretching the artery walls.

• Tunica Externa:

  • Outermost layer of the artery walls, providing additional support.

Page 2: Veins

• Veins have a thinner tunica media with less smooth muscle.

• Lumen:

  • Extremely stretchy; can collapse and then refill like a water balloon when blood is added.

• Veins do not significantly change blood pressure because they are too stretchy.

Page 3: Capillaries

• Capillaries have a single layer of endothelial cells (one cell thick).

• Function: Main site for gas exchange (O2 and CO2) as well as the transport of nutrients, hormones, and chemicals.

Page 4: Blood Pressure

• Definition: The force of blood against arterial walls.

• Relationship with blood volume:

  • Less blood results in decreased pressure against walls.

  • More blood increases pressure.

• Control Mechanisms:

  • Influenced by heart rate and peripheral resistance.

• Increased peripheral resistance also leads to increased stroke volume, which relates back to blood pressure.

Page 5: Blood Pressure Control

• Baroreceptors: Located in carotid arteries, aortic arch, kidneys; detect changes in blood pressure.

• Stimulation of cardiac center in the medulla oblongata will release epinephrine/norepinephrine to:

  • Increase heart rate

  • Increase peripheral resistance and stroke volume.

Page 6: Cardiac Output

• Definition: Volume of blood ejected from the ventricles per minute.

• Formula:

  • CO = HR x SV (where HR is heart rate and SV is stroke volume).

• Increased cardiac output leads to increased blood pressure.

Page 7: Funny Leak Gates

• Funny Leak Gates: Channels that regulate cardiac function.

• When epinephrine/norepinephrine bind to beta-receptors on these gates, heart contractions increase heart rate.

Page 8: Baroreceptor Function

• Monitoring Changes:

  • Baroreceptors respond to changes in blood pressure and alert the cardiac center in the medulla oblongata.

  • They monitor blood pressure in the head, thoracic cage, and abdominal regions.

Page 9: Blood Flow Dynamics

• Blood flows from the left ventricle into the aorta (highest blood pressure point in the body).

• As blood travels through arteries to arterioles, the pressure decreases until reaching capillaries and veins (lowest pressure at right atrium).

• Capillaries can use sphincters to regulate blood flow and prevent excess pressure.

Page 10: Venous System

• The venous system relies on pressure from surrounding muscles to push blood back to the heart.

• Increased physical activity enhances venous return due to muscle contractions.

Page 11: Peripheral Resistance

• Definition: Resistance caused by blood flowing against arterial walls.

• Blood moves fastest in the center of arteries and slowest along the edges, creating friction.

Page 12: Stroke Volume

• Stroke Volume Definition: The volume of blood ejected by the ventricles with each heart beat.

• Stroke volume affects cardiac output directly.

• The amount of blood remaining in the ventricles post-contraction influences the amount available for the next contraction.

Page 13: Increasing Stroke Volume

• Strategies to increase stroke volume include increasing end diastolic or decreasing end systolic volume.

• More blood in the ventricles (increased end diastolic volume) can lead to improved contraction force when the ventricle squeezes.

Page 14: Frank-Starling Law

• This law states that greater stretch of the heart muscles results in stronger contractions.

• Key to increasing stroke volume through enhanced venous return.

Page 15: Increasing Blood Volume

• Kidney Function:

  • Juxtaglomerular cells in the kidneys secrete renin when they detect low blood volume.

  • This stimulates a cascade that ultimately leads to increased blood volume through hormonal changes.

Page 16: Aldosterone

• Role of Aldosterone:

  • Increases sodium reabsorption in the kidneys.

  • This in turn draws water into the bloodstream, increasing blood volume and blood pressure.

Page 17: Erythropoiesis

• Process: Triggered by low oxygen saturation detected by chemoreceptors in the kidneys.

• Leads to secretion of erythropoietin, which stimulates red blood cell production and subsequently increases blood viscosity and pressure.

Page 18: Effects of High Altitude

• At high altitudes, lower oxygen prompts increased erythropoietin release, thickening the blood to improve oxygen transport.

• This adaptation can strain the heart under normal atmospheric pressure due to increased blood viscosity.

Page 19: Blood Volume and Fluid Balance

• Monitoring fluid intake and urine output can indicate kidney function.

• If no urine is produced despite fluid intake, kidneys may be failing.

Page 20: Conclusion

• Understanding the relationship between cardiovascular factors is crucial for diagnosing and treating conditions related to blood pressure and volume.