Biology 1012:   Chapter 44 - Gas Exchange and Circulation (Part II)

 

Human Lungs

 

Negative Pressure Breathing

 

A Bell Jar Model

 

What makes the lungs so elastic?

 

•High surface tension among H2O molecules in the surface film.

 

•How do we know that?

 

 

•Tests with cadavers

 

•We use a surfactant to moderate pull of surface tension.

 

How Much Air Do You Respire?

 

•Tidal Volume - Amount of Air inhaled and exhaled at rest

 

•Vital Capacity - Maximum air volume that can be inhaled and exhaled

 

•Residual Volume - amount of air remaining in lungs that cannot be forced out

(unless a lung is collapsed)

 

Collapsed Lung

 

Pneumothorax

•Pleural cavity fills with air

 

Hemothorax

•Pleural cavity fills with blood

 

Lungs of Other Vertebrates

 

•Reptiles

•Rib Muscles

•Locomotion

 

•Respiration

 

 

•Can’t move and breathe simultaneously

 

 

 

 

•Bird Lungs

•Highly efficient

•Fly great distances or to great heights

•Parabranchi (tubules) – no alveoli

•One-way flow

 

Bird Lung Animation :  http://www.sci.sdsu.edu/multimedia/birdlungs/

 

 

Control of Human Breathing

 

CO2 + H2O « H2CO3 « H+ + HCO3- 

 

•          Increase in CO2 results in increased H+ (lower pH)

 

•          pH monitored by nerves in neck

 

What is Blood?

 

Plasma (55%)

Mainly water

+ electrolytes - inorganic salts +

proteins

clotting factors (fibrinogens)

immunglobins

buffers

osmoregulators

lipid escorts

 

Cellular Components (45%)

•Erythrocytes - Red Blood Cells

•Gas Transport

•Hemoglobin

•Lack Nucleii and Mitochondria

• 

•Leucocytes - White Blood Cells

•Defense

•often OUTSIDE the circulatory system

•interstitial fluid; lymph nodes

• 

•Platelets

 

•Cell fragments - clotting

 

 

Structure of Hemoglobin

 

 

 

 

 

 

Cooperative Binding

 

As each O2 molecule is bound it reconfigures hemoglobin to make it more receptive to O2

 

As each O2 molecule is released it reconfigures hemoglobin to make it less receptive to O2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bohr shift

 

•Lower pH (and warmer temperatures) cause hemoglobin to release more O2.

·        What would Non-Cooperative Binding Look Like?

 

 

 

 

 

 

 

 

 

 

 

CO2 transport

 

•Dissolved in plasma  - 7%

•Bound to amino groups of hemoglobin - 23%

•As Bicarbonate (HCO3-) ions in blood - 70%

 

 

Carbon Dioxide Transport

Fig 44.18

 

 

 

 

 

 

 

 

 

 

 

 

 

Circulatory Systems

•Open

 

•Hemolymph

 

•Not always confined to blood vessels

 

 

•Closed

 

•Blood

 

•Confined to blood vessels

 

 

•High pressure

 

 

 

Components

Heart

Arteries

Arterioles

Capillaries

Veins

 

 

Interstitial Fluids

 

•Even in closed systems, fluids leak out

 

•Some reabsorbed, some absorbed by lymph vessels

Movement to and from Capillaries

 

•Blood pressure forces fluid out

 

•As pressure is reduced osmotic pressure forces fluid back in.

 

 

Heart Structure Among the Vertebrates

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Human Heart

 

What makes the heart beat?

 

 

 

 

Regulating the Heart Beat

 

Rate controlled by:

•SA node

•AV node

•Specialized Muscle Fibers

 

 

•Impulses produce electrical current

 

 

•Detectable by Electrocardiogram (EKG)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cardiac Cycle

 

 

 

 

 

 

 

 

 

 

Patterns in Blood Pressure and Blood Flow

 

•Why pressure so low in veins?

 

 

 

Why is High Blood Pressure Bad?

 

 

 

 

Blood pressure factors

 

 

 

 

 

 

 

 

Regulating Blood Pressure

 

•Baroreceptors

•Pressure sensing nerve cells

•Heart and major arteries

•Responses to low pressure

•Increase cardiac output  (=  heart rate x stroke volume)

•Constrict arterioles serving capillaries of skin and intestines

•Constriction of Veins