14. Describe the factors that assist the return of systemic venous blood to the heart.
Veins carry blood back to the heart. In veins are found valves, thin folds of tunica interna that form flap like cusps. The valve cusps project into the lumen, pointing toward the heart. The low blood pressure in veins allows blood returning to the heart to slow and even back up; the valves aid in venous return by preventing the backflow of blood. The skeletal muscle pump and the respiratory pump also assist.
15. What is the cardiovascular center? What are the principal inputs and outputs?
Groups of neurons scattered within the medulla oblongata that regulate heart rate, force of contraction, and blood vessel diameter.
The CV center receives input both from higher brain regions and from sensory receptors. Output from the CV center flows along sympathetic and parasympathetic neurons of the ANS.
16. Describe the operation of the carotid sinus, aortic, and right heart reflexes.
The carotid sinus reflex helps regulate blood pressure in the brain. The aortic reflex regulates systemic blood pressure.
17. Explain the role of chemoreceptor’s in the regulation of blood pressure.
Chemoreceptor’s detect changes in blood level of O2, CO2, and H+. Hypoxia, acidosis, or hypercapnia stimulates the chemoreceptor’s to send impulses to the CV center.
18. Describe the hormonal regulation of blood pressure.
Several hormones help regulate blood pressure and blood flow by altering cardiac output, changing systemic vascular resistance, or adjusting the total blood volume.
Blood Pressure Regulation by Hormones
Factor influencing BP Hormone Effect on BP
Cardiac Output
Increased heart rate and
contractility Norepinephrine
Epinephrine
increase
Systemic Vascular Resistance
Vasoconstriction
Vasodilation Angiotensin ll
Antidiuretic hormone
Norepinephrine
Epinephrine
Atrial natriuretic peptide
Epinephrine
Nitric Oxide
Increase
decrease...