Anatomy

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

Blood Volume

Blood Volume increase

Blood Volume decrease

Aldosterone

Antidiuretic hormone

Atrial natriuretic peptide

Increase

decrease

19. What is auto regulation? Explain how it occurs through physical and chemical changes in blood.

The ability of a tissue to automatically adjust its blood flow to match its metabolic demands. Physical Changes- Warming promotes vasodilation, and cooling causes vasoconstriction. Chemical Changes- Vasodilating chemicals released by metabolically active tissue cells include K+, H+, lactic acid, and adenosine. Vasoconstrictors include thromboxane A2, super oxide radicals, serotonin, and endothelins.

20. Define shock. What are its signs and symptoms?

Shock is a failure of the cardiovascular system to deliver enough O2 and nutrients to meet cellular metabolic needs. Systolic blood pressure is lower than 90 mmHg, resting heart rate is rapid due to sympathetic stimulation and increased blood levels of epi and norepi, pulse is weak and rapid due to reduced cardiac output and fast heart rate, skin is cool and pale, mental state is altered, urine formation is reduced, the person is very thirsty, the pH of blood is low, and the person may have nausea.

21. Describe the three stages of shock.

In Stage I of shock, when low blood flow (perfusion) is first detected, a number of systems are activated in order to maintain/restore perfusion.