The Cardiovascular System: Blood Vessels and Circulation

Question 1

Functions of the Circulatory System

Answer 1

• Carry blood
• Exchange nutrients, waste products, and gases
• Transport of hormones, components of the immune system, molecules required for coagulation, enzymes, nutrients, gases, waste products, etc.
• Regulate blood pressure
• Controls blood flow

Question 2

Structural Features of Blood Vessels

Answer 2

Arteries:
- Elastic or conducting arteries
- Muscular or medium arteries
- Arterioles

Capillaries:
- Site of exchange within tissues

Veins:
- Thinner walls than arteries, contain less elastic tissue and fewer smooth muscle cells:
1) Venules
2) Small veins
3) Medium or large veins

Question 3

Blood Vessels: Wall of an Artery and a Vein

Answer 3

Artery + Vein:
- Lumen (both)
- Valve (Vein only)
- Endothelium of tunica interna (both)
- Connective tissue (both)
- Tunica media (both)
- Tunica externa (both)

Question 4

Capillary and Capillary Network

Answer 4

Capillary:
- Tissue fluid
- Endothelial cell
- Slit

• During exercise, an increased blood flow of red blood cells

Question 5

Arterioles

Answer 5

• Transport blood from small arteries to capillaries
• Like small arteries, capable of vasoconstriction

Question 6

Venules and Small Veins

Answer 6

• Venules drain capillary network
• Small veins transport blood back to the heart

Question 7

Pulmonary Circulation

Answer 7

• From right ventricle into pulmonary trunk
• Pulmonary trunk divides into left and right pulmonary arteries
• Two pulmonary veins exit each lung and enter left atrium

Question 8

Systemic Circulation

Answer 8

Aorta exits left ventricle and divided in three parts:
1) Ascending aorta (right and left branch from here)
2) Aortic arch (Brachiocephalic, left common carotid, left subclavian artery)
3) Descending aorta (Thoracic aorta, Abdominal aorta)

Question 9

Systemic Circulation – Veins

Answer 9

• Returns blood from body to right atrium

Major veins:
- Coronary sinus (heart)
- Superior vena cava (head, neck, thorax, upper limbs)
- Inferior vena cava, abdomen, pelvis, lower body)

Question 10

Blood Circulation – Darcy’s Law of Flow

Answer 10

Flow = Conductance* x Pressure:
- CO = SVC x MAP
- Cardiac Output = Systemic Vascular Conductance* x Mean Arterial Pressure

Question 11

Capillary Exchange of Gases, Nutrients, Waste

Answer 11

Capillary exchange:
- movement of substances in and out of capillaries

Most important way of exchange = diffusion:
- Lipid soluble cross capillary walls diffusing through plasma membrane
- Water soluble diffuse through intercellular spaces or through fenestrations of capillaries

Question 12

Control of Blood Flow in Tissues

Answer 12

Local control:
- In most tissues, blood flow is
proportional to aerobic metabolic needs of tissues

Neural control:
- Sympathetic nervous system is
responsible for routing blood flow and maintaining blood pressure

Hormonal control:
- Sympathetic action potentials stimulate epinephrine and norepinephrine

Question 13

Local Control of Blood Flow in Tissues

Answer 13

• Vasodilation (+ diameter) vs Vasoconstriction (-diameter)
• Control of small vessel diameter (those in the regulatory area) primarily responds to changes in the metabolic needs of tissues

Question 14

Neural Control of Blood Flow in Tissues

Answer 14

• Important in minute-to-minute control of local circulation
• Sympathetic division most important
• Vasomotor center in medulla oblongata

Question 15

Regulation of Mean Arterial Pressure (MAP)

Answer 15

• MAP: slightly less than the average of systolic and diastolic pressures because diastole lasts longer than systole
• MAP = [(2 x DBP) + SBP]/3
• MAP = 70 mmHg at birth, 100 mmHg from adolescence to middle age, 110 mmHg in healthy older individuals

Two systems to regulate arterial blood pressure within a normal range of values:
- Short-term mechanisms (minutes)
- Long-term mechanisms (hours-days)

Question 16

Short-Term Regulation of Blood Pressure

Answer 16

• Baroreceptor reflexes: change peripheral
  resistance (TPR), heart rate (HR), and stroke volume (SV) in response to changes in mean arterial blood pressure (MAP)
• Chemoreceptor reflexes: sensory receptors
  sensitive to oxygen (O2), carbon dioxide (CO2), and pH levels of blood

Question 17

Baroreceptor Reflex Control of Blood Pressure

Answer 17

• Acute hypertension high blood pressure
• Heart rate, HR Stroke volume, SV Cardiac output, CO (all decreases)
• TPR Resistance (decreases)
• Pressure = flow x resistance
  MAP = CO x TPR (decreases)
• MAP (increases)

Question 18

Chemoreceptor Reflex Control of Blood Pressure

Answer 18

PO2 (decreases)
PCO2 (increases)
pH (decreases)

• HR, SV, CO (all increases)
• TPR (increases)
• Pressure = flow x resistance
  MAP = CO x TPR (increases)
• Altitude exposure

Question 19

Long-Term Control of Blood Pressure: Mechanisms

Answer 19

1. Renin-angiotensin-aldosterone mechanism
2. Anti-Diuretic Hormone (ADH, Vasopressin)
   mechanism

Question 20

Renin-Angiotensin-Aldosterone Mechanism

Answer 20

• MAP (decreases)
• TPR (increases)
• MAP (increases)
• Pressure = Flow x Resistance
  MAP = CO x TPR (increases)

Question 21

Antidiuretic Hormone (ADH, Vasopressin)
Mechanism

Answer 21

• Pressure = flow x resistance
  MAP = CO x TPR (increases)
• TPR (increases)
• CO (increases)