Chapter 21: Circulation and Respiration

transcript

Transporting fuel, raw materials, and gases into, out of, and around the body

Lecture by Jennifer Lange, Chabot College

Take-home message 21.1

In animals, the circulatory system is the chief distribution system.

It transports gases, nutrients, waste products, hormones, and immune system cells throughout the body.

The circulatory system also helps animals regulate their body temperature and plays a protective role against infection.

Types of Circulatory Systems

No formal system Open circulation Closed circulation

Thin animals have all cells within diffusion distance, so they don’t need a circulatory system.

Open systems have fluid moving inside and outside of containing vessels.

Closed systems always contain circulating fluid in vessels.

Closed Circulatory System Parts

Heart - generates force• Receiving chamber - atrium• Pumping chamber - ventricle

Vessels• Transport blood throughout body

Capillaries Serve as the Exchange Site

for Fluids and Nutrients

Animals that can acquire all the nutrients and oxygen they need by diffusion do not have circulatory systems. Among animals that do have circulatory systems, the system can be open or closed. In closed circulatory systems, tiny blood vessels called capillaries bring blood close enough to tissues that diffusion can move the necessary molecules from the blood into the cells and from the cells into the blood.

Types of Closed Systems:

Two-Chambered Heart

Types of Closed Systems: Four-

Chambered Heart

Types of Closed Systems:

Three-Chambered Heart

Take-home message 21-3

Vertebrate’s circulatory systems vary in structure.

Fishes have a two-chambered heart with one circuit of flow.

Birds and mammals have a four-chambered heart and two circuits.

Amphibians and most reptiles have a three-chambered heart and two circuits of blood flow.

The human circulatory system has two loops: the pulmonary circuit and the systemic circuit.

Heart sounds are created by the closing of the heart valves.

The flow of blood can be directed toward or away from specific body regions.

The human heart is an extremely durable pump.

It sends blood on a figure 8, two-circuit path through the body—first to the lungs for loading up with oxygen and, on its second circuit, to the tissues and organs of the body.

Valves in the heart and veins keep blood flowing in one direction.

The heart has its own internal pacemaker, thus it can contract without external nervous stimulation.

The wave of electricity follows the same pattern with each beat: SA node and across

atria Interventricular septum

then across ventricles beginning at apex

The sinoatrial node initiates regular, rhythmic contractions.

A heart contraction begins with an electrical impulse in the SA node in the right atrium.

The contraction quickly spreads to the left atrium, and passes down the center to the bottom of the heart, then moves upward, pushing blood from both ventricles out through the pulmonary arteries and aorta.

The two major components of blood are water and RBC.

Types of Blood Cells

Blood is a salty, protein-rich mixture of cells and fluid, important in the transport of respiratory gases, vitamins and minerals, nutrients, hormones, components of the immune system, and metabolic wastes.

Blood also helps maintain a constant internal environment, including body temperature.

Blood cells are produced throughout life by stem cells in bone marrow.

There are two types of cells suspended in the plasma: red cells, white cells, as well as cellular fragments, platelets.

Blood pressure measures the strain on the walls of the arteries when the ventricles are contracting (systolic pressure) and when the ventricles are relaxed (diastolic pressure).

Pumping farther distances and against gravity requires more pressure to be generated by the heart.

Blood pressure measurement gives important clues about an individual’s cardiovascular health.

A blood pressure reading consists of two measures—the systolic pressure, when the heart is contracting, and the diastolic pressure, when the heart is relaxing.

With high blood pressure, the heart must work harder at all times, the arteries can lose some of their elasticity, and health risks are increased.

Heart attacks result from narrowing of the coronary arteries that obstructs blood flow the the heart muscle.

Cholesterol is a dietary requirement, but too much causes disease.

The type, or density, of the cholesterol consumed is important.

Cardiovascular disease includes all diseases of the heart and blood vessels, including heart attacks and strokes, and is the leading cause of death in the United States.

It generally begins with the development of fatty deposits on the inner walls of arteries, which increase the risk of blood clots and reduce the flow of blood in coronary arteries that supply oxygen to the heart.

Because plaque formation is usually initiated by circulating cholesterol, it is possible to reduce the risk of cardiovascular disease by reducing cholesterol intake.

The lymphatic system has functions that compliment those of the cardiovascular system.

Failure of the lymphatic system results in fluid accumulation in the lower extremities.

The lymphatic system runs close to the circulatory system throughout the body, and plays a supporting role in the process of circulation by performing three main functions:

1) recycling fluid that leaks out of the capillaries of the circulatory system

2) marshaling white blood cells to help fight dangerous cells and pathogens

3) absorbing nutrients from the digestive system

The stress of lying causes changes in cardiovascular function.

The polygraph can be an effective tool for evaluating whether or not an individual is telling the truth.

A polygraph measures manifestations of the fight-or-flight response: • chest and abdominal movement during

respiration • changes in skin conductance • heart rate and amplitude and blood pressure

Methods of Gas Exchange—

Respiratory Systems

Methods of Gas Exchange—Respiratory Systems

In single-celled and very small multicellular organisms, gas exchange can occur by direct diffusion.

In larger multicellular organisms, gas exchange is a two-stage process: 1) exchange between the external environment

and the organism’s circulatory system, which usually takes place in lungs, tracheae, or gills, and

2) exchange between the circulatory system and the cells involved in cellular respiration.

Maximizing Gas Exchange— Counter Current

Mechanism

In aquatic vertebrates, respiration begins when an organism opens its mouth, takes in water, and moves the water out through its gills. Gas exchange takes place in the gills, which extract as much oxygen as possible from the water by maintaining an oxygen concentration gradient between the water and the blood flowing through the gills.

Maximizing Gas Exchange—

Enlarging Surface Area

Humans have tidal flow, which decreases net oxygen concentration.

Maximizing Gas Exchange— Enlarging Surface AreaThe alveoli have a large surface area and a short diffusion distance, both of which increase the rate of gas exchange.

Effects of Smoking—Not Just Respiratory

In terrestrial vertebrates, respiration begins as air is sucked in through the mouth or nose. The air moves down the trachea into the lungs, where oxygen diffuses from the air into capillaries and thus into the bloodstream, while carbon dioxide diffuses from blood to air. Finally, the oxygen-depleted air is exhaled and the process begins again.

Exchanging Gas When the Pressure is Low

Exchanging Gas When the Pressure is LowBirds have one-way flow through the lungs via the incorporation of a pair of air sacs.

Birds often spend time in high-altitude, low-oxygen habitats and may fly for long periods of time, both of which require a great deal of oxygen. These extreme needs are met by a circular system of air flow and cross-current blood flow in the lungs, which make it possible for birds to exchange gases more efficiently than other terrestrial vertebrates.

Ventilation—Moving Air In and Out

Inhalation requires active contraction of muscles to lift the ribs.

Expiration, at rest, is passive due to lung elasticity.

In reptiles, birds, and mammals, breathing occurs in two steps: inhalation and exhalation. During inhalation muscles contract, pulling the diaphragm down, expanding the rib cage, and increasing the volume of the chest cavity and lungs, which causes air to be sucked into the lungs. When the muscles relax, the chest cavity returns to its original size and air is forced out of the lungs.

The diffusion of gases between the outside and inside of an animal depends on several physical factors, including temperature, viscosity, and pressure, leading to variations among animals in

their respiratory efficiency. The rate of gas exchange is higher in cold

temperatures, in air, and at low altitudes.

Oxygen Transport Requires a Carrier Protein

Factors Affecting Hemoglobin SaturationPartial Pressure of

Oxygen

Factors Affecting Hemoglobin SaturationPartial Pressure of Oxygen

Oxygen

Red blood cells are filled with hemoglobin, a molecule that picks up oxygen in the lungs and transports it around the body, releasing it in organs and tissues, such as muscles, where it is needed for cellular respiration.

Myoglobin is protein similar to hemoglobin that stores oxygen in hard working muscles.

Myoglobin is an oxygen-binding protein embedded in muscle cells that can

release one molecule of oxygen under conditions of extremely low PO2.

Adaptations to Low Partial Pressureof Oxygen

At high altitudes, the PO2 is lower, making breathing and activity difficult. Animals living at high altitudes solve this problem by producing a form of hemoglobin that has a higher affinity for

oxygen, becoming saturated with four molecules of oxygen even when

breathing in air with a low PO2.

Adaptations to Low Partial Pressure of Oxygen DPG alters the stickiness of

hemoglobin.

Humans living at high altitudes become acclimated to low-oxygen conditions over the course of three to five weeks. This acclimation includes increasing the production of diphospholglyceric acid (DPG) in red blood cells and thereby reducing hemoglobins affinity for oxygen, leading to release of higher

levels of oxygen to muscles during exertion.

Adaptations to Low Partial Pressure of Oxygen

Seals have higher blood volume that is stored it in the spleen.

Deep-diving mammals can hold their breath for an hour or more:

• by having double the volume of blood (per kilogram body weight) and double the muscle myoglobin concentration relative to

humans,• by lowering their heart rate

dramatically,• and by constricting the blood vessels

in most tissues, sending blood only where it is needed most.

Chapter 21: Circulation and Respiration

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