Chapter 22 Pt. 1: Circulation

why do we need a circulatory system?

• Transport nutrients throughout the body

  • Small intestine absorbs nutrients

  
  

• Have to move around oxygen and CO2

  • Gas exchange

• Have to get oxygen to all of our cells so we can make ATP

• Immune system connection

  • Have to move around things like white blood cells and antibodies

  • Controllers and defenders

circulatory system

• organ system that moves substances to and from the cells of the body

• All cells must receive nutrients, exchange gases, and remove wastes

• In most animals, circulatory systems facilitate these exchanges

• Usually comprised of a heart, blood and blood vessels

• Advanced functions: stabilize pH (via buffering), temperature regulation, help fight infections

• exchange with all body tissues

Tips For Interpreting Circulatory Diagrams

• Red: contains oxygenated blood

• Blue: contains deoxygenated blood

• “Right” and “left” labels in heart anatomy are from the perspective of the heart facing out of your body

  • Not looking at it on the screen

  • Opposite of what you would think

Atria

• receive blood from body and transfer to ventricle

ventricles

• pump blood into arteries

pulmonary circuit

• pumps to/from the lungs

systemic circuit

• pumps to/from the body

arteries

• blood vessel

• carry blood away from the heart; pressurized

capillaries

• blood vessel

• exchange materials with tissue cells

veins

• blood vessel

• return blood back to the heart; not pressurized

  
  

valves

• in veins and heart keep blood flowing in one direction, preventing backflow

Path of Blood

• Right atrium receives oxygen poor blood from vena cavae

• Blood is pumped from right atrium to right ventricle

• Right ventricle pumps blood to pulmonary arteries, oxygenated at lungs

• Pulmonary veins return oxygenated blood to left atrium

• Blood flows from left atrium to left ventricle

• Left ventricle pumps blood through aorta, delivered to body tissues

• Veins (ultimately vena cavae) return blood to right atrium

right atrium

• Receives blood From body

  (Deoxygenated)

left atrium

• Receives blood From lungs

  (Oxygenated)

right ventricle

• Pumps blood To lungs

  (Deoxygenated)

left ventricle

• Pumps blood To body

  (Oxygenated)

Sinoatrial (SA) Node

• Located on upper wall of right atrium

• Initiates a heartbeat every 0.85 sec; “pacemaker”

• Emits electrical impulse causing both atria to contract and activate the AV node

Atrioventricular (AV) Node

• Located at the base of the right atrium

• Receives impulse from SA node

• AV node impulse signals the ventricles to contract from the bottom upward

Electrocardiograms (EKGs)

• record heart’s electrical activity

• Rapid (tachycardia): faster than 100 bpm

• Slow (bradycardia): slower than 60 bpm

• Atrial *fibrillation (atrium is quivering)

• Ventricular *fibrillation

• Flatline (no heartbeat)

Fibrillation

• type of arrythmia (irregular heartbeat) characterized by unsynchronized and/or rapid heart contraction due to abnormal electrical activity

Phases of the Cardiac Cycle

• Pulse: the wave of arterial pressure that originates in the aorta and is transmitted throughout the body each time the ventricles contract

• There are two phases in the cardiac cycle:

  • Diastole: the period of low blood pressure when the heart is relaxed

    • Blood flows into all 4 heart chambers

  • Systole: the period of high blood pressure when the heart contracts

    • Atrial contraction fills ventricles with blood

    • Ventricles contract and push blood into arteries

• Blood pressure: reported as 𝑠𝑦𝑠𝑡𝑜𝑙𝑖𝑐 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 / 𝑑𝑖𝑎𝑠𝑡𝑜𝑙𝑖𝑐 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒

• Force with which blood flows through arteries

blood pressure

• Normal blood pressure is 𝟏𝟐𝟎 / 𝟖𝟎

• High blood pressure (hypertension) causes heart to work harder and arteries to lose elasticity

• Blood pressure greater than 120/80

• Low blood pressure (hypotension) can cause dizziness because brain does not get enough blood flow

• Blood pressure less than 90/60

Blood Vessel Structure Fits Function

• Arteries carry blood at high pressure away from the heart

• Thick walls that are strong and elastic to deal with the high pressure of blood pumped by heart

• Pulmonary arteries carry deoxygenated blood to the lungs

• Arteries extending from the left ventricle of the heart carry oxygenated blood to the other tissues

Capillaries

• Diffusion Between Blood and Tissues

• Have very tiny diameters (allow passage of 1 red blood cell at a time)

• Have very thin walls (one cell thick to maximize diffusion)

• Exchanges gases, nutrients and wastes with body’s tissue cells

Mechanism of Blood Flow in Veins (and Return to the Heart)

• How is gravity overcome to return blood to the heart?

• Skeletal muscle contractions

  • Muscles press against veins, pushing blood closer towards heart

  • Valves prevent backflow and ensure blood only moves in one direction

Atherosclerosis

• Negatively Affects Arteries

• The thickening of the artery wall due to the buildup of plaque (fatty deposits including LDL “bad cholesterol”)

• Leads to reduced blood flow and fragile artery walls

• Can also cause complete blockage

• Coronary artery disease: atherosclerosis in coronary arteries

Health Connection: Diet and Cholesterol (1 of 2)

• Cholesterol is vital for health, but too much can lead to artery damage

• Lipoproteins carry cholesterol in the blood to body tissues

• High-density lipoproteins (HDL) carry excess LDL/cholesterol to the liver for degradation "good"

• Low-density lipoproteins (LDL) can accumulate in the blood vessels "bad"

• Saturated fat intake: increases LDL

• Unsaturated fat intake: decreases LDL

• Exercise: increases HDL

heart attack

• Death or damage of heart muscle tissue due to partial or complete coronary arterial blockage; circulation issue

• Blood and oxygen blocked from reaching heart tissue

cardiac arrest

• heart suddenly stops beating; typically an electrical issue

Coronary Bypass Surgery

• Creates a new path to “bypass” blocked area of coronary artery supplying blood to heart muscle

• Arteries or veins are re-routed or transplanted as grafts

• Mammary artery (from chest) often used because it is resistant to atherosclerosis