Respiratory System Pt. II Thomas Ackerman Juyoung Jang Liezel Riego

Quick Review 6.4.1: Distinguish between ventilation, gas exchange, and cell respiration. 6.4.2: Explain the need for a ventilation system. 6.4.3: Describe the features of the alveoli that adapt them to gas exchange. 6.4.4: Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles, and alveoli.

Functions of respiratory system Providing an area for gas exchange between air and circulating blood Moving air to and from exchange surfaces Protecting respiratory surfaces from environmental variations

Organization of the respiratory system Includes the nose, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli Respiratory tract: carries air to and from alveoli Upper respiratory tract: filters and humidifies incoming air Lower respiratory tract: gas exchange

6.4.5: Mechanisms of Ventilation To inhale, the diaphragm contracts and flattens and the external intercoastal muscles also contract and cause the ribcage to expand and move up. The diaphragm contracts drops downwards. Thoracic volume increases, lungs expand, and the pressure inside the lungs decreases, so that air flows into the lungs in response to the pressure gradient. These movements cause the chest cavity to become larger and the pressure to be smaller, so air rushes in from the atmosphere to the lungs. To exhale, the diaphragm relaxes and moves up. In quiet breathing, the external intercoastal muscles relax causing the elasticity of the lung tissue to recoil. In forced breathing, the internal inercoastal muscles and abdominal muscles also contract to increase the force of the expiration. Thoracic volume decreases and the pressure inside the lungs increases. Air flows passively out of the lungs in response to the pressure gradient. The ribs to move downward and backward causing the chest cavity to become smaller in volume and the pressure increases pushing air out of the lungs into the atmosphere. (From AP Edition Biology)

Gas exchange occurs across specialized respiratory surfaces Respiratory Medium: source of O2 Air or and water Respiratory Surface: where gases are exchanged with the surrounding environment Animals move O2 and CO2 by passive transport (diffusion-higher concentration to lower concentration) Rate of diffusion is proportional to the surface area where diffusion occurs and inversely proportional to the square of the distance of movement Thin and large surface area, maximize gas exchange

Mammalian respiration Negative pressure breathing: pulling air instead of pushing it out into the lungs. Lung volume increases as rib muscles and diaphragm contract Tidal volume: Volume of air inhalation Vital capacity: Max t.v. in forced breathing Residual volume: amount of air remaining after forced breathing

Other Animals (NOT mammals) Fish Gills: outfoldings of body surface extended in water Helps ventilation process: increasing flow of respiratory medium over the respiratory surface Countercurrent exchange: makes it possible to transfer O2 to the blood in water Results in diffusion gradient for O2 over entire length of capillaries in gills As blood moves through gill capillaries, loaded with O2, even through against concentration gradient More than 80% in O2 in water is able to be diffused Insects Tracheal system: air tubes branching through body Folded internal respiratory surface Trachae – opens outside Open circulatory system

Other Animals (NOT mammals) Birds 8 or 9 airsacs and lungs Bellows keeping air flowing Not to be confused with alveolar sacs Amphibians Positive pressure breathing: air is forced through lungs During cycle, muscles lower in oral cavity, drawing air through nostrils Closed nostrils and mouth, floor of oral cavity rises Air is forced down trachea Elastic recoil of lungs and compression of muscular body wall force air back out of the lungs

Marine Mammals What happens when respiratory medium is not accessible continuously? Weddell seal (and other “diving” mammals): Ability to store large amounts of O2 Twice as much per kg of body mass as humans 5% in lungs, 70% in blood Twice as much blood volume per kg of body mass as humans Huge spleen Stores 24L of blood High concentration of myoglobin (oxygen-storing protein) in muscles 25% of O2 in muscle, 13% in humans Swim with little muscular effort, buoyancy Heart rate and O2 consumption rate decrease while diving Blood supply to most muscles either restricted or shut down completely

Breathing ventilates the lungs Control of breathing Breathing control centers: medulla oblongata and pons. Pons sets basic breathing rhythm. Sensors in aorta and carotid arteries monitor O2 and CO2 concentrations Negative-feedback mechanism prevents lungs from over-expanding. Medulla regulates breathing activity in response to pH changes of tissue fluid (cerebrospinal). CO2 diffuses from blood to fluid, reacts with water and carbonic acid, lowering pH Increases depth and rate of breathing Excess CO2 released through exhalation This happens during exercise O2 concentrations have little effect When O2 is extremely depressed (high altitudes), O2 sensors in aorta and carotid arteries in neck send signals to breathing control centers Increases breathing rate Normally, rise in CO2 concentration accompanies fall in O2 concentration

Control of breathing (Cont.) Hyperventilation: tricking the breathing center Excessive, deep, rapid breathing purges blood of too much CO2 Breathing center temporarily stops sending impulses to rib muscles and diaphragm Breathing stops until CO2 levels increase (or O2 levels decrease) enough so that the breathing center turns back on

Respiratory pigments bind and transport gases Oxygen has low solubility in water and in blood Respiratory pigments: transport gases and help buffer the blood Greatly increase the amount of O2 the blood can carry Hemoglobin - An iron containing protein in red-blood cell that reversibly binds oxygen (“reversibly” just means loading oxygen in the lungs and unloading it in the rest of the body) Four protein subunits with iron in the middle of each subunit Each hemoglobin can bind to four molecules of O2 Binding of O2 to once subunit causes the other three to change their shape slightly

The Bohr Shift An effect that releases oxygen by hemoglobin Lowers the affinity for oxygen because of drop in pH and an increase in partial pressure This causes the hemoglobin to release more oxygen which can be used for cellular respiration

Carbon Dioxide Transport Other Functions for Hemoglobin Helps transport CO2 Assists in buffering- prevents harmful changes in blood pH Process of Transportation CO2 diffuses into red blood cells (90%) and plasma(7%) Some CO2 is picked up by hemoglobin but most react in water forming carbonic acid (H2CO3) Carbonic acid dissociates into a Hydrogen ion (H+) and bicarbonate ion (HCO3-) Hemoglobin binds most of the H+ preventing it from acidifying the blood and starting the Bohr Shift

Carbon Dioxide Transport (Cont.) The carbonic acid (H2CO3) diffuses into the plasma Blood flows through the lungs so the whole process is rapidly reversed Diffusion of CO2 out of the blood shifts the chemical equilibrium in favor of the conversion of bicarbonate ion (HCO3-) to CO2 Bicarbonate ion (HCO3-) diffuses from plasma into the red blood cells This then combines with a hydrogen ion (H+) to form (H2CO3) , a carbonic acid Carbonic acid is converted back to CO2 and water CO2 is then unloaded into the alveolar space which then will be expelled during exhalation

Pressure and Ventilation The direction of airflow is determined by the relation of atmospheric pressure and intrapulmonary pressure Intrapulmonary pressure is the pressure inside the alveoli Respiratory pressure Low when you are relaxed and breathing quietly Drops when you inhale Increases when you exhale Atmospheric pressure decreases with increasing altitude and so do the partial pressure of gases including oxygen Partial pressure: measure of the concentration of one gas in a mixture of gases; pressure exerted by particular gas in a mixture of gases (pressure exerted by oxygen in air)

Gas exchange at High Altitude (HL) Partial air pressure of oxygen at high altitude is lower than at sea level Effects Hemoglobin may not become fully saturated as it passes through the lungs tissues of the body may not be adequately supplied with oxygen Mountain Sickness with muscular weakness, rapid pulse, nausea and headaches can be avoided by ascending gradually to allow the body to acclimatize to high altitude

Gas exchange at High Altitude (Cont.) During acclimatization the ventilation rate increases Extra red blood cells are produced, increasing the hemoglobin content of the blood Muscles produce more myoglobin and develop a denser capillary network These changes help to supply the body with enough oxygen Some people who are native to high altitude show other adaptations: a high lung capacity with a large surface area for gas exchange larger tidal volumes and hemoglobin with an increased affinity for oxygen

Changes in the respiratory system At birth Before delivery, fetal lungs are fluid-filled and collapsed. At first breath, lungs inflate and never collapse completely thereafter. Aging: Less efficient in elderly Elastic tissue deteriorates, lowering the vital capacity of the lungs. Movements of the chest are restricted by arthritic changes and decreased flexibility of costal cartilages. Some degree of emphysema is generally present.

Asthma Chronic long term lung disease that inflames and narrows airways The muscles around the bronchi tighten which causes less air to flow to your lungs Causes-pollen, pets, dust mites, fungi etc. Being “too clean” causes the immune system to react against harmless substances

Study Questions Why is the position of lung tissues within the body an advantage for terrestrial animals? Explain how countercurrent exchange maximizes the ability of fish gills to extract dissolved O2 from water How does an increase in the CO2 concentration in the blood affect the pH of cerebrospinal fluid? A slight decrease in blood pH causes the heart’s pacemaker to speed up. What is the function of this control mechanism? How does breathing differ in mammals and birds? What determines whether O2 or CO2 diffuse into or out of the capillaries in the tissues and near the alveolar spaces? Explain. How does the Bohr shift help deliver O2 to very active tissues? Carbon dioxide within red blood cells in the tissue capillaries combines with water, forming carbonic acid. What causes the reverse of this reaction in red blood cells in capillaries near the alveolar spaces? Describe three (3) adaptations that enable Weddell seals to stay underwater much longer than humans can.

Suggested Answers If lungs extended into environment, dry out, diffusion would stop Results in diffusion gradient for O2 over entire length of capillaries in gills, opposite flow allows for O2 loading, despite against concent. grad. > CO2 = < pH Increases heart rate increases rate at which CO2 is delivered to lungs, where CO2 is removed. Air passes through lungs in one direction in birds; direction reverses in mammals between inhalation and exhalation. Differences in partial pressure; gases diffuse higher>lower partial press. Causes hemoglobin to release more O2 at lower pH, in vicinity of tissues w/ high resp. rates and CO2 release. Decrease in CO2 concent. in plasma as it diffuses into alveolar spaces causes carbonic acid within RBC to break down, yielding CO2, diffuses into plasma Blood volume relative to body mass; larger spleen; more myoglobin in muscles; heart rate and metabolic rate decrease during dives