Biology

• Cardiovascular system


  The primary function is to supply body cells with O2 and nutrients and carry away CO2 and waste products
• Cardiovascular system


  • Closed circuit system
  • Composed of heart, arteries, capillaries, veins, blood

  
• Pulmonary circulation


  1. Carries blood to the lungs

  2. Eliminates CO2 via the lungs

  3. Returns blood to the heart
• Systemic circulation


  1. Supplies blood to the rest of the body

  2. Delivers O2 to all the body

  3. Carries away wastes
• Heart


  • Cone-shaped, hollow, muscular pump
  • Adult heart has a mass of 250-350 grams
  • About the size of a clenched fist, 14 cm long and 9 cm wide
  • Lies in the mediastinal area of thoracic cavity between the lungs

  
• Heart location


  • Posterior to sternum
  • Medial to lungs
  • Anterior to vertebral column
  • On the top of diaphragm
  • About 2/3 of heart lies left to midline

  
• Heart base, apex, and surfaces


  • Base formed by left and right atria
  • Apex formed by left ventricle
  • Inferior/diaphragmatic formed by left and right ventricles
  • Anterior/sternocostal formed mostly by right ventricle
  • Left/pulmonary formed mostly by left ventricle

  
• Pericardium


  • Layer of connective tissue that protects and anchors the heart
  • Composed of fibrous pericardium and serous pericardium
  • Serous pericardium has parietal layer and visceral layer (epicardium)
  • Pericardial cavity between parietal and visceral layers contains serous fluid to reduce friction

  
• Heart wall structure


  • Epicardium (outer layer)
  • Myocardium (middle layer, cardiac muscle)
  • Endocardium (inner layer)

  
• Heart chambers


  • 2 superior atria (right and left)
  • 2 inferior ventricles (right and left)
  • Interatrial septum between right and left atria
  • Interventricular septum between right and left ventricles

  
• Right atrium


  • Receives deoxygenated blood
  • Opens to superior vena cava, inferior vena cava, coronary sinus, right atrioventricular opening

  
• Right ventricle


  • Deoxygenated blood flows in from right atrium
  • Opens to pulmonary trunk

  
• Left atrium


  • Oxygenated blood enters from pulmonary veins
  • Opens to left atrioventricular opening
• Left ventricle


  • Oxygenated blood flows in from left atrium
  • Wall 2-3 times thicker than right ventricle
  • Opens to aortic artery

  
• Heart valves


  • Connective tissue flaps lined by epithelial tissue
  • Function to permit one-way blood flow and prevent backflow
  • 4 valves: 2 atrioventricular and 2 semilunar

  
• Coronary arteries


  • Left and right coronary arteries originate from ascending aorta
  • Right coronary artery has right marginal artery and posterior interventricular artery
  • Left coronary artery has anterior interventricular artery and circumflex artery
• Cardiac cycle


  1. Alternating contraction (systole) and relaxation (diastole) of all chambers

  2. Atrial systole moves 20% of blood to ventricles

  3. Ventricular systole forces blood into blood vessels through semilunar valves

  4. Ventricular diastole allows 80% of blood to flow passively from atria to ventricles

  
• Heart sounds


  • Lubb sound from ventricular contraction and closure of atrioventricular valves
  • Dupp sound from closure of semilunar valves during ventricular relaxation

  
• Electrocardiogram (ECG)


  • Records potential fluctuations during cardiac cycle
  • Shows P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave (ventricular repolarization)
  • P-R interval measures AV conduction time
  • QT interval measures total systolic time of ventricles
• Cardiac output


  • Amount of blood ejected by each ventricle per minute
  • Calculated as stroke volume x heart rate

  
• Homeostasis


  The relatively stable state inside the body of an animal
• Animal organs and organ systems constantly adjust to internal and external changes in order to maintain this steady state
• Examples of internal conditions maintained homeostatically

  • Level of blood glucose
  • Body temperature
  • Blood calcium level
• These conditions remain stable because of physiologic processes that result in negative feedback relationships
• Set point


  The goal of homeostasis is the maintenance of equilibrium around a specific value of some aspect of the body or its cells
• While there are normal fluctuations from the set point, the body's systems will usually attempt to go back to this point
• Stimulus


  A change in the internal or external environment that is detected by a receptor
• Response


  The adjustment of the system's activities so the value moves back toward the set point
• For instance


  • If the body becomes too warm, adjustments are made to cool the animal
  • If glucose levels in the blood rise after a meal, adjustments are made to lower them and to get the nutrient into tissues that need it or to store it for later use
• Ectotherms


  • Animals that have a body temperature that is the same as their environment and thus varies with the environmental temperature
• Endotherms


  • Animals that maintain a constant body temperature in the face of environmental changes
• Ectotherms have been called cold-blooded
• Endotherms have been called warm-blooded animals
• Vasodilation


  The opening up of arteries to the skin by relaxation of their smooth muscles, bringing more blood and heat to the body surface, facilitating radiation and evaporative heat loss, cooling the body
• Vasoconstriction


  The narrowing of blood vessels to the skin by contraction of their smooth muscles, reducing blood flow in peripheral blood vessels, forcing blood toward the core and vital organs, conserving heat
• Some animals have adaptions to their circulatory system that enable them to transfer heat from arteries to veins that are flowing next to each other, warming blood returning to the heart
• Countercurrent heat exchange


  This prevents the cold venous blood from cooling the heart and other internal organs
• The countercurrent adaptation is found in


  • Dolphins
  • Sharks
  • Bony fish
  • Bees
  • Hummingbirds
• Some ectothermic animals use changes in their behavior to help regulate body temperature
• For example


  • They simply seek cooler areas during the hottest part of the day in the desert to keep from getting too warm
  • They may climb onto rocks in the evening to capture heat on a cold desert night before entering their burrows