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Circulation and Respiration (General properties of circulatory systems…
Circulation and Respiration
Overview
Exchanges ultimately occur at the cellular level by crossing the plasma membrane
Unicellular organisms
exchanges occur directly with the environment
Every organism must exchange materials with its environment
Multicellular organisms
e.g. Gills:
O2 diffuses from the water into blood vessels
CO2 diffuses from blood into the water
Circulatory systems link exchange surfaces with cells throughout body
Most animals: Cells exchange materials with the environment via a fluid-filled circulatory system
A circulatory system minimizes the diffusion distance in animals with many cell layers
Diffusion
only efficient over small distances
spontaneous movement of molecules from an area of higher concentration to an area of lower concentration
General properties of circulatory systems
Circulatory system
connects the fluid that surrounds cells with the organs that exchange gases, absorb nutrients, and dispose of wastes
open or closed system
An open circulatory system
no distinction between blood
and interstitial fluid
A closed circulatory system
Blood is confined to vessels and is distinct from the interstitial fluid
Cardiovascular system
Humans and other vertebrates have a closed circulatory system called cardiovascular system
Heart
Atrium (心房) receives blood
Ventricle (心室) pumps blood away from the heart
Blood vessels
Arteries carry blood away from the heart
Epithelium 內皮
Smooth muscle
Connective tissue
Veins return blood back to the heart
Valve
Epithelium
Smooth muscle
Connective tissue
Capillaries (微血管)
–sites of chemical exchange between the blood and interstitial fluid (組織間液)
Epithelium
Double circulation system
Pulmonary circuit (肺循環) between the heart and lungs
Systemic circuit (體循環) between the heart and the rest of the body
Oxygen-poor and oxygen-rich blood are pumped separately from the right and left sides of the heart
Mammals and birds
have a four-chambered heart with two atria and two ventricles
Left side of the heart pumps and receives only oxygen-rich blood
Right side receives and pumps only oxygen-poor blood
The path of blood flow through the human heart functions as two pumps moving blood between
Heart and lungs
Heart and the rest of the body
The Cardiac Cycle (心跳週期)
0.8 second
One heart beat is one complete cardiac cycle (正常人每分鐘心跳60 ~ 80下 = heart rate)
heart rate (心跳速率): also called the pulse (脈搏: 動脈交替擴張彈回), is the number of beats per minute
The heart relaxes (舒張) and contracts (收縮) throughout our lives
Diastole (心舒期)：relaxation phase of the heart cycle (心肌放鬆，血液進入心臟 4 房室)
Heart is relaxed
Blood flows in (0.4 sec)
Systole (心縮期)：contraction phase(心肌收縮將血液擠出心房室)
Atria contract. Blood is
forced into ventricles (0.1 sec)
Ventricles contract.
Blood is pumped out (0.3 sec)
Pacemaker and the Control of Heart Rate
Pacemaker (節律點), or SA (sinoatrial) node (竇房節)
Sets the tempo of the heartbeat (設定心臟的收縮速率)
composed of specialized (特化) muscle tissue in the wall of the right atrium (右心房)
Pacemaker generates electrical impulses to AV node
AV node impulses spread through atria
Impulses reach ventricles
Blood pressure
Optimal blood pressure for adults is below 120 systolic and below 80 diastolic
High blood pressure, or hypertension
High blood pressure, or hypertension
Persistent systolic blood pressure higher than 140 and/or
Diastolic blood pressure higher than 90
Blood moves back towards the heart
Surrounding skeletal muscles that compress (壓縮) the veins
One-way valves that permit blood flow only toward the heart
Blood components
By volume
45% cells
Platelets 血小板
WBC
RBC
55% plasma
90% water
10% dissolved salts, proteins, and other molecules
Gas exchange supplies O2 for cellular respiration and disposes of CO2
Respiratory surfaces
e.g. gills (鰓) and lungs (肺)
Circulatory system (循環系統)
transports gases between the lungs and the rest of the body
Gas exchange is by diffusion (擴散)
Mammalian respiratory system
Larynx (喉)
Pharynx (咽)
Trachea (氣管)
Bronchus (支氣管)
Bronchiole(小支氣管)
Alveoli (肺泡)
Animals require large, moist respiratory surfaces for exchange of gases between their cells and air or water
Negative pressure breathing
Inhalation
Diaphragm(橫膈) contravts (moves down)
Inhalation (Air pressure is higher in atmosphere than in lungs)
Rib cage expands as rib muscles contract
Exhalation
Rib cage gets smaller as rib muscles relax
Diaphragm relaxes (moves up)
Exhalation (Air pressure is lower in atmosphere than in lungs)