BIO II Ch 42: Circulation and Gas Exchange

Example of specialized exchange system in animals

Gills in fish, lungs in mammals

-O2 diffuses from water into blood vessels

-CO2 diffuses from blood into water

How are structure and function related in the exchange and circulation of oxygen and carbon dioxide?

1. Specialized structures (lungs/gills) mediate gas exchange with the environment.

2. Networks of highly branched, thin-walled vessels maximize exchange surface area.

3. A pump (heart) drives the flow of fluid.

4. Wide, thick-walled vessels enable circulation throughout the body. 

Gastrovascular cavities

-Some cnidarians (like jellyfish) have these very elaborate structures that function in both digestion and the distribution of substances throughout the body

-The body wall that encloses this structure is only two cells thick

EX: Flatworms have this, and a flat body that minimizes diffusion distances

Hemolymph

A circulatory fluid used by some invertebrates, such as arthropods, that functions similarly to blood, bathing the organs directly in an open circulatory system

EX: In insects, some arthropods, and molluscs

Closed Circulatory System

-In this system, blood is confined to vessels and is distinct from the interstitial fluid

-Has a dorsal vessel (main heart) and auxillary hearts

EX: Annelids, cephalopods, and vertebrates have this

Cardiovascular system

-A closed circulatory system that humans and other vertebrates have

-Blood vessels

Open Circulatory System

-Insects, arthropods, and some molluscs have this. 

-Tubular heart

3 Main Types of Blood Vessels

1. Arteries

2. Veins

3. Capillaries

****Blood flow is ONE WAY in these vessels

Arteries

-Branch into arterioles and carry blood away from the heart to capillaries (slows it down by branching, pressure is decreased)

-Oxygen-rich blood

Arterioles 

-Branched from the arteries that carry blood away from heart to capillaries

Capillary beds

-Networks of capillaries

-Sites of chemical exchange between blood and interstital fluid

Venules

-Converge into veins and return blood from capillaries to the heart

-On the backside of the capillary bed

Are arteries and veins distinguished by the direction of blood flow or by O2 content?

-Direction of blood flow!!!!

How does blood flow through the heart (enter and exit sites)

Blood enters through the atria and is pumped out through the ventricles

Why can fish have such simple circulatory systems compared to amphibians (frogs) and mammals (pandas)?

-GRAVITY!!!!

-Fish are in water, and they don’t need as much energy

-They don’t need a huge heart and can get away with a single circulatory system because they are in water and floating

-

Why can frogs (amphibians) suffice with a Pulmocutaneous Circuit?

-They are in land AND water

-Have a “purple” section where oxygenated and deoxygenated blood mix

-Need LUNG AND SKIN CAPILLARIES because they rely on both methods for gas exchange.

Why do pandas (mammals) have a Pulmonary circuit?

-ONLY LAND animals

-Have fully developed lungs

-Require oxygen from the air through respiration and have a more complex circulatory system to efficiently transport oxygenated blood.

Cardiac Cycle

The heart contracting and relaxing in a rhythmic cycle

Systole

The contraction or pumping phase

Diastole

The relaxation or filling phase

Cardiac Output

The volume of blood pumped into the system circulation per minute and depends on both the heart rate and stroke volume

Heart rate

Number of beats per minute

Stroke volume

Amount of blood pumped in a single contraction

“Lub-Dup” sound of a heart beat correlation

-Recoil of blood against AV valves (lub)

-Recoils of blood against the semilunar valves (dup) 

Heart murmur

Backflow of blood through a defective valve

The Sinoatrial (SA) node

-” Pacemaker” 

-Sets the rate and timing at which cardiac muscles contract

-Sends signals to spread through the atria (first hump in EKG)

-Is regulated by two portions of the nervous system: the sympathetic and parasympathetic divisions

• Sympathetic: speeds up the pacemaker

• Parasympathetic: slows down the pacemaker

**Regulated by hormones and temperature

Electrocardiogram (EKG/ECG)

-Test that shows the impulses that travel during the cardiac cycle by measuring electrical activity of the heart.

Atrioventricular (AV) node

-Impulses from the SA node travel to this node

-Here, the impulses are delayed and then travel to the Purkinje fibers that make the ventricles contract (big hump in EKG)

Systolic pressure

The pressure in the arteries during ventricular systole; it is the highest pressure in the arteries 

***Animals with long necks require a very high systolic pressure to pump blood a great distance against gravity

Pulse

The rhythmic bulging of artery walls with each heartbeat

Diastolic pressure

-Pressure in the arteries during diastole; it is lower than systolic pressure

Vasoconstriction

The contraction of smooth muscle in arteriole walls; it increases blood pressure

Vasodilation

The relaxation of smooth muscles in the arterioles; it causes blood pressure to decrease

**** Blood pressure is low in veins b/c one-way valves in veins prevent back flow of blood

What is an example of a major inducer of vasodilation?

Nitric oxide

Two Mechanisms that Regulate the Distribution of Blood in Capillary Beds

1. Constriction or dilation of arterioles that supply capillary beds

2. Precapillary sphincters that control flow of blood between arterioles and venules.

   1. - Sphincters relaxed: walls of capillaries are exchanging with liquid around it; oxygenated and deoxygenated blood mix- purple capillary

   2. -Sprincters contracted: arteriole flows straight to venule, two bloods don’t mix

Lymphatic system

-Returns fluid that leaks out from the capillary beds 

-Drains into veins in the neck

Lymph

Fluid lost by capillaries

Lymph nodes

-Organs that filter lymph and play an important role in the body’s defense

-When the body is fighting an infection, these become swollen and tender

What is edema?

Swelling caused by disruptions in the flow of lymph

Stem cells

-Found in the red marrow of bones, especially ribs, vertebrae, sternum, and pelvis

-Are the source of development for erythrocytes, leukocytes, and platelets

Erythropoietin (EPO) 

-Stimulates erythrocyte production when O2 delivery is low

-Physicians use this to treat anemia

Coagulation

-The formation of a solid clot from liquid blood

Thrombus

A blood clot formed within a blood vessel; can block blood flow

Atherosclerosis

-One type of cardiovascular disease

-Caused by the buildup of fatty deposits (plaque) within the arteries

-Cholesterol is a key player in the development of this disease

Heart Attack

-AKA myocardial infarction

-The damage or death of cardiac muscle tissue resulting from blockage of one or more coronary arteries

Stroke

The death or nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head

What is the chest pain caused by partial blockage of the coronary arteries called during a heart attack/stroke?

Angina pectoris

Hypertension

-AKA high blood pressure

-Contributes to heart attack or stroke

-Can be controlled by dietary changes, exercise, medication

Gas exchange across specialized respiratory surfaces

The uptake of O2 from the environment and the discharge of CO2 to the environment

How does LDL/HDL affect the risk of cardiovascular disease?

-A high LDL/HDL ratio increases the risk of cardiovascular disease

-The proportion of LDL to HDL can be decreased with exercise, smoking cessation, and cutting trans fat

What kinds of drugs reduce LDL levels and risk of heart attacks

Statins

How can aspirin play a role in atherosclerosis and thrombus formation?

-Aspirin inhibits inflammation and reduces the risk of heart attacks and stroke

-Inflammation plays a role in atherosclerosis and thrombus formation

Partial Pressure in Gas Exchange

-The pressure exerted by a particular gas in a mixture of gases 

-Also applies to gases dissolved in liquids such as water

-O2 is much less soluble in water than in air

How do marine worms ventilate and create a large surface area for gas exchange?

They have parapodiums that function as gills and increase the surface area for gas exchange.

How do crayfish ventilate and create a large surface area for gas exchange?

They have gills that are highly branched

How do sea stars ventilate and create a large surface area for gas exchange?

They use tube feet equipped with gills to facilitate gas exchange. Also have coelom

How do fish facilitate gas exchange?

-Use a countercurrent exchange system

• Blood flows in the opposite direction to water passing over the gills

• Blood is always less saturated with O2 than the water it meets 

• In fish gills, more than 80% of the O2 dissolved in the water is removed as water passes over the respiratory surface 

What is the main role of the circulatory system (open or closed)?

-Transports gases between the lungs and the rest of the body

-The size and complexity of lungs correlate with an animal’s metabolic rate

Surfactancts

-Secretions that coat the surface of the alveoli in the lungs

-Alveoli lack cilia and are susceptible to contamination

Tidal volume

The volume of air inhaled with each breath

Vital capacity

The maximum tidal volume

Residual exhalation

The air remaining in the lungs after exhalation

Diaphragm direction when inhaling and exhaling:

1. Inhalation- the diaphragm contracts and moves downwards

2. Exhalation- the diaphragm relaxes and moves upwards.

What is normal blood pH?

About 7.4

How do CO2 levels affect blood pH?

-If CO2 increases, blood pH falls (ex: exercise)

-If CO2 decreases, blood pH rises

Gas exchange in the alveoli

-O2 diffuses into the blood and CO2 diffuses into the air

-By the time blood leaves the lungs, the pressures of O2 and CO2 match the values for air in alveoli

Bohr shift

CO2 produced during cellular respiration lowers blood pH and decreases the affinity of hemoglobin for O2