BIOL 1306: Gas Exchange and Respiration

Explain the connection between the respiratory system and circulatory system in gas exchange

1. Ventilation- movement of air and water in and out of specialized gas exchange organ

2. Diffusion at respiratory surface- oxygen moves into blood and carbon dioxide moves out

3. Circulation- dissolved carbon dioxide and oxygen transport throughout the body via circulatory system

4. Diffusion at tissues- Oxygen moves from the blood to the tissues and carbon dioxide moves from tissues to the blood

Countercurrent flow

Blood and water/air move in opposite directions creating gradient where O₂ is always diffusing from water into the blood, making O₂ concentration higher in the water than the blood

Concurrent flow

Blood and water/air move in the same direction, they eventually reach a point where concentrations equalize and O₂ will stop diffusing

Why is contercurrent flow more efficient than concurrent flow?

More oxygen can be extracted from water due to concentration gradient; concurrent flow uptake limited at ~50% or less

Diaphragm

Separates abdominal and thoracic cavities

The diaphragm _____________ during inhalation and becomes ______________

contracts; convex

Describe what is occuring during inhalation

Diaphragm is contracted (convex shape) and moves downward. Pressure in cavity decreases. Lungs expand and air moves in.

Describe what is occuring during exhalation

DIaphragm relaxes (concave shape). Chest cavity decreases and air is exhaled.

The site of gas exchange where oxygen enters and carbon dioxide exits is called the…

Alveoli

Alveoli are small, thin-walled sacs surrounded by _______________

Capillaries

________________ conduct air to the alveoli

Bronchioles

From the nasal cavity, describe the flow of air throughout the respiratory system

Nasal cavity → Pharynx → Larynx → Trachea → Primary Bronchi → Secondary Bronchi → Tertiary Bronchi → Bronchioles → Alveoli 

What is negative pressure?

Pressure that is lower than the atmospheric pressure which creates a pressure gradient to facilitate air flow

Describe the pressure in the thoracic cavity during inhalation

The contraction and downward movement of the diaphragm increases the volume of the thoracic cavity and decreases its pressure

When there is a higher volume in the thoracic cavity, there is _________ negative pressure

More

What is the result of the negative pressure generated in the lungs?

Air flows from an area of high pressure to an area of low pressure

What is the role of the water-based plasma?

Maintains pH of 7.4 and osmotic balance; transits nutrients, O₂, CO₂, waste products, and hormones

What is the function of the cell fragments known as platelets?

Minimizing blood loss by facilitating the clotting process

Describe the process of clotting and scab formation

Platelets adhere to exposed CT and release chemicals that make nearby platelets sticky. This forms a plug (cluster of platelets). Platelets secrete clotting factors promote scab formation. Fibrinogen → fibrin reinforces plug and forms clot. Platelets contract, pull torn edges together, and stimulate smooth muscle division 

What is the main function of leukocytes or white blood cells?

Immune function

What is the main function of red blood cells?

Transport oxygen from lungs to body tissues and participate in transporting CO₂ from tissues to lungs

Red blood cells are best described as…

Bags of hemoglobin used for O₂ and CO₂ transport 

What is the structure of arteries?

Tough and thick-walled; connective tissue layer with elastic fibers

Arteries carry blood _________ from the heart

Away

Which blood vessel generates the highest pressure?

Arteries

Describe the structure of capillaries

One cell thick walls; extremely thin to facilitate diffusion

What is the function of capillaries?

Allow gas exchange in their beds 

Which blood vessel has the lowest pressure?

Capillaries

Describe the structure of veins?

Thin-walled vessel; larger diameter than arteries; one-way valves

Narrate the path blood takes through the heart, pulmonary system, and systemic system

Oxygen poor blood from body returns to heart via superior vena cava and inferior vena cava. The blood flows into the right atrium until it contracts and moves into the right ventricle. The right ventricle contracts and pumps oxygen poor blood to the pulmonary arteries whcih carry the blood to the lungs. Gas exchange occurs in the lungs and the oxygen poor blood becomes oxygen rich. The pulmonary veins carry the oxygen rich blood to the left atrium. The left atrium contracts and the blood flows into the left ventricle. The aorta distributes the oxygen rich blood to the rest of the body. Once the blood delivers oxygen and collects carbon dioxide and waste, it returns to the heart through smaller veins, converging into the superior and inferior vena cavae, completing the cycle. 

What is partial pressure?

pressure of a particular gas in a mixture of gases

How does gas move?

Areas of high partial pressure to areas of low partial pressure

Oxygen concentrations are ________ in the environment and ________ in the tissues

High; low

Carbon dioxide concentrations are ________ in the environment and ________ in the tissues

Low; high

Why must the partial pressure gradient of a gas across a surface be large?

Maximum absorption

Partial pressure of O₂ in alveoli is _______ than in the deoxygenated blood returning from the body 

Higher

What is the result of the pressure differences the alveoli and the dexoygentated blood returning from the body tissues?

O₂ diffusion from alveoli into blood where it binds to hemoglobin in erythrocytes

Higher pO₂ in the blood drives oxygen into the _________

tissues

What is a typical PO₂ at rest?

40 mm Hg

What is a typical PO₂ during exercise?

20 mm Hg

Why is the PO₂ lower during exercise than at rest?

more unloading is happening 

What causes the S-shape of the saturation curve?

Cooperative binding

Cooperative binding is the…

Binding of one oxygen molecule increases affinity of hemoglobin for additional oxygen molecules 

What does the bohr shift mean?

Hb more likely to release O₂ during exercise in which pO₂ is high, pH lower, and tissues under oxygen stress 

A lower oxygen affinity would result in a ________ shift on a saturation curve

Right

A higher oxygen affinity would result in a ________ shift on a saturation curve

Left

Left bohr shift

Less CO₂, higher pH, pO₂ is lower

Right bohr shift

More CO₂, lower pH, pO₂ is higher 

Conduction

Direct heat transfer between two bodies that are in contact with each other

Convection

Heat exchanged between a solid and a liquid/gas 

Radiation

Heat transfer between two bodies that are not in direct contact

Evaporation

Phase exchange that occurs when gas becomes liquid 

What kind of organisms are able to warm their own tissues?

Endotherms

What kind of organisms gain heat by radiation or conduction?

Ectotherms

_________________ maintain a constant body temperature?

Homeotherms

____________________ allow their body temperature to change depending on the environment that they are in

Poikilotherms

Heat flows from warm arteries to cool veins in…

Countercurrent heat exchangers

Sense changes in carbon dioxide concetration

Chemoreceptors

Where are the respiratory centers located?

Medulla oblongata and pons in the brainstem

Hyperventilation

rapid and deep breathing; reduces CO₂ levels 

Hypoventilation

slow and shallow breathing; increases CO₂ levels

How are gases transported?

Simple diffusion

Why is it difficult to breathe at high altitudes?

Decreased driving pressure for oxygen from alveolar gas into arterial blood is insufficient to fully oxygenate the blood as it passes through the pulmonary capillaries.

Aquatic animals live in an environment that contains much
less…

Oxygen

Why do water breathers need to expend more energy to ventilate than non water breathers?

Water is much more dense and viscous than air

Why is hemoglobin needed to assit with oxygen transport in the blood?

O₂ does not dissolve well in water

How does temperature affect the rate of diffusion of a gas?

Warmer media leads to less gas dissolved

How does surface area affect the rate of diffusion of a gas?

It increases absorption

What conditions must be met by diffusion barriers for maximum diffusion to occur?

Thin and moist

How do animals with small volumes perform gas exchange?

They use their entire body surface

Gills are…

extensions of the pharynx

Water flows in ______ direction(s) in gil filaments

One

Fish gils utilize _____________________ flow for gas exchange

Countercurrent

O₂ diffuses into the _________ and CO₂ diffuses into the ___________

blood; lung

What is the result of increased carbon dioxide in the blood stream?

pH decreases and blood becomes more acidic

Increased acidity in the blood would trigger the medullary center to…

Increase breathing pace to lower CO₂ levels

Open circulatory systems

Hemolymph is not confined exclusively to vessels but comes in direct contact with body tissues

What is the result of open circulatory systems?

Molecules do not have to diffuse across the wall of a vessel

Closed circulatory system

Blood flows in a continuous circuit

Where is carbon dioxide waste get picked up?

Capillary beds

Which side of the heart handles only oxygen-poor blood?

Right side

Which side of the heart pumps only oxygen-rich blood?

Left side

The velocity at which blood travels through the blood vessels is highest in…

Arteries

Atria

Recieve blood returning from the circulation

Ventricles

Generate force to propel the blood out of the heart and through the circulatory system

Right atria

Recieves O₂ poor blood from body

Right ventricle

Receives O₂ poor blood from right atria and pumps blood to lungs

Left atria

Receives O₂ rich blood from lungs

Left ventricle

Receives O₂ rich blood from left atria anf pumps O₂ rich blood to body

What are the steps of the cardiac cycle?

1. Atrial and ventricular diastole

2. Atrial systole and ventricular diastole

3. Ventricular systole and atrial diastole

What causes the “lub” sound?

Atrial systole and ventricular diastole

What causes the “dub” sound?

Ventricular systole and atrial diastole

Cardiac muscle cells ________ _________ need signals from the nervous system

Do not

Sinoatrial node

Spreads signal through cardiac muscle cells; generates electrical impulses in the atria; sets rate od heart contractions (pacemaker)

Atrioventricular node

Between right atrium and right ventricle; brief delay allows atria to empty; relays signals to ventricles via apex; triggers ventricular contraction

Explain the process of electrical activation of the heart

1. Signal originates at SA node

2. Signal spreads to atria and they contract

3. Signal delayed at AV node

4. Signal spreads along conducting fibers to bottom and then top of the ventricles; ventricles contract

5. Ventricles relax

Oxygen is loaded from the __________ and onto the __________________________ in the blood

Lung; hemoglobin

Carbon dioxide is released from the ________________ into the ____________

Blood; lung

Once air is inhaled into the lungs, the partial pressure of oxygen is ______________ than that of blood coming from the body

Higher

Why does oxygen end up in the blood?

The higher partial pressure in the lungs than in the blood causes oxygen to passively diffuse high to low partial pressure, ending up in the blood