ch 10

• Circulatory system


  Also called the cardiovascular system or the vascular system, is an organ system that permits blood to circulate and transport nutrients, oxygen, carbon dioxide, hormones, and blood cells to and from the cells in the body to provide nourishment and help in fighting diseases, stabilize temperature and pH, and maintain homeostasis
• Lymphatic system


  Part of the circulatory system, circulates lymph, passage of lymph takes much longer than that of blood
• Circulatory system


  • Includes a complex network of vessels that are filled with blood pumped by the heart
• Blood vessels


  • Arteries which carry blood away from heart
  • Capillaries which are the site of exchange of gasses, nutrients, and wastes
  • Veins which carry blood towards the heart
• Circulatory system includes two systems

  • Pulmonary - Heart & Lungs
  • Systemic - Heart and body tissues
• Arteries


  • Thick and elastic
  • Able to constrict and dilate
  • Absorb blood pressure
• Veins


  • Thin and non-elastic
  • Not able to constrict and dilate
  • Do not absorb blood pressure
  • Contain valves
• Movement of blood through veins and venules

  1. Blood pressure lowers as blood moves further from the heart

  2. Blood must travel back towards the heart with the help of skeletal muscles and special one way valves found only in veins and venules

  3. Skeletal muscles squeeze the veins and cause blood to be pushed towards the heart, one way valves prevent blood moving away from the heart
• Vasodilation & Vasoconstriction in arteries

  Arteries are able to expand or contract in order to control the flow of blood throughout the body to control the exchange of heat, move blood to digestive system and away from the muscles after a meal, move blood to muscles and skin during activity and away from the digestive system
• Vasoconstriction


  Narrowing of arteries
• Vasodilation


  Widening of arteries
• Arteriosclerosis


  Healthy arteries become flexible and stiff, restricting blood flow to organs and tissues
• Atherosclerosis


  Buildup of fats and cholesterol in and on artery walls (plaques), restricting blood flow
• Cardiac muscle


  • Myogenic - capable of generating a contraction from within the muscle itself, no nerves from brain signal heart to contract, nervous system influences rhythm but does not generate electrical activity that causes heart to beat, sinaotrial (SA) node sends signal to heart in rhythmic fashion setting pace of heart contraction
• Conducting system of the heart

  • SA Node
  • AV Node
  • Bundle of His
  • Purkinje Fibres
• Electrocardiogram (ECG or EKG)


  Simple, painless test that detects and records the heart's electrical activity, can show heart rate, rhythm, and strength and timing of electrical impulses passing through each part of the heart
• Systole and diastole


  • Ventricular systole - contraction, ventricular diastole - relaxation
  • Atrial systole - contraction, atrial diastole - relaxation
• Cardiac output


  Amount of blood pumped by the heart each minute, calculated as stroke volume x heart rate
• Stroke volume


  Quantity of blood pumped with each heartbeat
• Heart rate


  Number of beats per minute
• Strong hearts can pump more blood with fewer beats, weak hearts need to increase rate to meet body's demands
• Blood pressure


  Force of the blood on the artery walls, depends on cardiac output and arteriolar resistance
• Systolic blood pressure


  Pressure of blood in arteries during and right after ventricular contraction
• Diastolic blood pressure


  Pressure of blood in arteries during ventricular relaxation
• Many factors can affect blood pressure, including water/salt levels, condition of kidneys/nervous system/blood vessels, and hormone levels
• Blood pressure regulation is essential for healthy functioning of the circulatory system
• Low blood pressure (hypotension) results in decreased transport of materials and can cause fatigue
• High blood pressure (hypertension) weakens artery walls and increases risk of rupture and heart attack
• vasodilation = BP reduced
• Vasocontriction = BP elevated
• Pathway of blood from AORTA

  1. Aorta

  2. Artery

  3. Arteriole

  4. Capillary

  5. Veinule

  6. Vein

  7. Vena Cava
• Blood pressure regulation due to temperature (low BP)

  1. Stimulus - hypothermia

  2. Receptor - thermoreceptors in the skin

  3. Control center - medulla oblongata in brain

  4. Effector - skeletal muscles shiver, vasoconstriction of blood vessels

  5. Reaction - temperature goes up
• Blood pressure regulation due to temperature (high BP)

  1. Stimulus - fever

  2. Receptor - thermoreceptors in the skin

  3. Control center - medulla oblongata in brain

  4. Effector - vasodilation of blood vessels, sweating

  5. Reaction - temperature goes down
• Lymphatic system


  A network of tissues and organs that transport lymph, a fluid that has infection fighting white blood cells
• The lymphatic system helps get rid of body toxins and waste
• Lymph is filtered in lymph nodes
• Functions of lymph


  • Transport clean fluids back to the blood
  • Drain excess fluid from tissue via the veins
  • Remove debris from the cells
  • Transports fats from the digestive system
• If the solute of blood increases

  Water is taken from lymph into the blood to maintain osmotic pressure
• Capillary fluid exchange


  1. When blood passes from arteries to veins through capillaries water is exchanged by diffusion

  2. The exchange relies on two forces: Hydrostatic pressure (pressure of water against blood vessels) and Osmotic pressure (the pressure of proteins in blood plasma that pulls water into the circulatory system)