Internal Systems and Regulation

Internal Systems and Regulation Respiratory System

Why do we breathe? • Aerobic organisms require every cell to obtain oxygen and remove carbon dioxide to survive  Gas Exchange. • All organisms share two characteristics: • Large respiratory surface • Moist environment • 3 factors that determine rate of exchange: • Area of cell membrane - larger area, more exchange. • Concentration difference - more oxygen in air then in lungs, greater rate of diffusion. • Diffusion distance - a very slight increase in diffusion can greatly reduce the rate at which a diffusing substance reaches its goal (2s to travel 10um, 4s to travel 20um, 16s to travel 40um etc.).

Simple Gas Exchange • Single celled organisms rely on diffusion. • To fulfill the moist requirement these organisms must live in wet, aquatic environments. • Either in the environment or in a host organism. • Some simple multicellular organisms also exchange gas in this manner. • The key is that they are aquatic as well • Volvox, hydra and planarian worm

On Land • Unicellular organisms like bacteria and fungi also need to exchange gas. • Water in the soil satisfies the moist requirement. • If the terrestrial organism lives on the surface of the soil then the moisture is derived from the soil below and from the air above. • These organisms are severely limited due to these moisture requirements.

Specialized Breathing • The larger the organism the more difficult it is to get oxygen to every cell in the organism. • Diffusion distance needs to be very small and modified. • As cells become differentiated for other purposes the amount of surface area devoted to gas exchange is reduced. • Adaptations have been developed to allow increased complexity while maintaining gas exchange at significant levels.

Specialized Breathing • Skin Respiration (p.283, fig.3a) • Phylum Annelida  segmented worms • Skin must be kept most to allow diffusion of oxygen to occur. • Skin is lined with capillaries which allow oxygen to enter the circulatory system and carbon dioxide to exit. • This is an advancement due to the fact that it is in this phylum that circulation starts to play a role in ensuring all cells respire properly. • Diffusion would simply not allow enough exchange of gases.

Specialized Breathing • Gills (p.283, fig.3b & 4) • Whole body is not available for gas exchange due to habitat in which these organisms live. • Both as defense and maintaining internal environment. • Surface area to allow exchange of gases is therein decreased however this is combated in two ways: • Where gas exchange does occur the surface area is increased. • A mechanism has evolved to allow the organism to ventilate this surface, that is, to move the oxygen containing medium over the gills to gain fresh oxygen.

Specialized Breathing • Gills • Feathery tissue in many aquatic species that allow gas exchange across thin gill membranes. • In some organisms (ex. tube worm) the gill is moved through the water while in other organisms (ex. fish and clams) water is ventilated over the gills in usually just one direction. • This reduces the amount of energy the animal must expend to move water over the gills. • Typical Movement • Water moves in through the mouth and over the gills. • Tiny capillaries absorb oxygen and release carbon dioxide. • Other functions?

Specialized Breathing • Out of the Water • Moisture retention becomes the main problem. • Breathing is the concept of ventilating a respiratory surface with air and it relies on a simple law of physics: • Air will move from a region of high pressure to a region of lower pressure until equilibrium is acquired. • Two main methods of terrestrial breathing have evolved based on this principle: • Tracheal Respiratory System and Lungs

Specialized Breathing • Tracheal Respiratory System • Insects utilize a series of external pores called spiracles which each lead to an internal series of tubes called tracheae. • All of the spiracles are controlled by valves to monitor water loss by the organism and to facilitate the pressure differential. • Abdomen expands  air pressure drops in tracheae  4 anterior paired spiracles open  air rushes into tracheae • Abdomen contracts  4 anterior paired spiracles stay closed but 6 posterior spiracles open  air pressure inside is now high and air flows out • Insects respiratory system and circulatory system are separate from each other.

Specialized Breathing • The Lung • Characteristic of air-breathing vertebrates is the internal lung. • Internal respiratory surface connected to the air by means of internal passageways. • Main components of lungs: • One or two lungs with a moist respiratory surface. • A means of forcibly bringing air into contact with the lung surface. • A circulatory system to move the gases around the body. • Frog uses a lung system in conjunction with skin respiration.

Mammalian Respiration • Respiration is made up of 4 parts: • Breathing – inspiration and expiration • External Respiration – gas exchange between air and blood • Internal Respiration – gas exchange blood and cells of the surrounding tissue • Cellular Respiration – chemical reactions • Respiratory Tract • Upper and Lower

Upper Respiratory Tract • Nostrils • Air is passed into the nasal passages where a few things happen to preserve delicate lung cells: • Turbinates, thin bones in nasal passage, secrete mucous to moisten the air. • Many capillaries warm incoming air • Pharynx – connects mouth and nasal cavity to larynx and esophagus • Glottis – opening of the trachea • Epiglottis – protects the glottis as it is a flap like structure and prevents food from entering trachea

Upper Respiratory Tract • Larynx – voice box • Holds the vocal cords using a cartilaginous material • When breathing muscles attached to the folds are relaxed and when we prepare to speak the muscles contract bringing the folds closer together and they vibrate. (p.286, fig. 2) • Long cords produce low sound • Trachea – windpipe • Supported by semi-circular cartilage rings • Most structures in upper respiratory tract are covered in mucous. When you have a cold more mucous is secreted so sneeze and cough more

Lower Respiratory Tract • Trachea branches into bronchi • Each bronchus subdivides into bronchioles • Each bronchiole ends in a cluster of tiny sacs known as alveoli • This is where gas exchange (external respiration) takes place • 70% simple diffusion, 30% facilitated diffusion, by the use of a special protein-based molecule in the alveolar cell membrane.

Lower Respiratory Tract • Each lung is divided into lobes • Right has 3, left has 2 (one less to accommodate the heart) • A bronchiole enters each lobe • Lungs are enveloped in tissue called pleura which contains the lungs but allows them to expand and contract

Mechanics of Breathing • Two muscular structures allow ventilation: • Intercostal muscles – muscles associated with ventral surface of rib cage • Diaphragm – muscle that separates thoracic cavity from abdominal cavity • Both work in unison to move air in and out of the lungs to allow ventilation. • p. 288, fig. 3

Lung Capacity • Different volumes of air can be drawn into the lungs. • Tidal volume – volume inhaled and exhaled in a normal breathing movement. • Inspiratory reserve volume – additional volume that can be taken in beyond tidal volume. • Expiratory reserve volume – additional volume that can be forced out beyond tidal volume. • Vital capacity – total volume of gas that can be moved in or out of lungs. • Tidal volume + inspiratory reserve volume + expiratory reserve volume • Residual volume – amount of gas that remains in lungs after a full exhalation  ensures collapse does not occur.

Counter-current flow • Water flow over gills in one direction • Saves energy since fish does not have to correct flow of water • As water flows over the gills the most oxygen depleted blood draws oxygen from the oxygen depleted water. • Oxygen will diffuse into the blood • As blood flows out of the gill it becomes increasingly oxygen rich due to the fact that it continues to meet water that is increasingly oxygen rich. • Mammalian lung – gas is exchanged in a constant medium. • Gills – blood is passed by a medium that is increasingly oxygen rich.

Birds • Migratory birds have developed a respiratory advantage to give them enough energy to migrate. • Utilize air sacs that ensure that residual air is never in contact with the lungs. • Air sacs do not allow gas exchange, simply a method of holding air to allow maximum efficiency. • Always an oxygen rich medium in contact with lungs • Birds also have a countercurrent exchange system with respect to their circulatory system so they are even more advanced.

Gas Exchange and Transport • Dalton’s Law of Partial Pressure • Each gas in a mixture exerts its own partial pressure • Atmospheric O2 is 21% x 101kPa = 21.21kPa • Gases diffuse from an area of higher partial pressure to lower partial pressure • Atmosphere O2 is 21.21, alveoli O2 is 13.3kPa so O2 rushes in and diffuses • Essentially the same thing is happening at different cells throughout the body as well • Arteries 12.6kPa of O2 to capillaries 5.3kPa of O2 • P. 291, fig 1 and p. 292, fig. 2

Control and Regulation of Breathing • Hypoxia – sickness due to high altitude conditions • Due to lower air pressure meaning less air at higher altitudes. • Less oxygen available to our bodies • Red blood cell numbers increase – training advantage • Breathing rates – controlled by medulla oblongata • Under normal conditions a regular signal is sent. • Carbon dioxide left in blood after ventilation travels to medulla oblongata and if levels too high nerve pulses are sent out to initiate faster breathing  more oxygen in. • The amount of oxygen also plays a role as chemoreceptors in aorta and cartotid arteries track oxygen pressure levels in the blood. If too low a message is sent to the medulla oblongata. • Also, breathing in too far stretches alveoli, message is sent to medulla oblongata and signal is sent to stop inhalation.

Respiratory Impairment • Drowning • Laryngospasm – larynx closes resulting in asphyxiation not water entering lungs • Freshwater – lipoprotein film on alveoli washed away, it collapses • Saltwater – fluid is drawn out of capillaries and into lungs. Results in more fluid for oxygen to try and diffuse through. • Carbon Monoxide Poisoning • Binds to oxygen receptors (hemoglobin) 200 times more tightly then oxygen does. • Symptoms similar to hypoxia • Toxic in low levels.

Respiratory Impairment • Bronchitis • Inflammation of bronchial tubes resulting in a narrowing of air passages. • More serious in the bronchioles as they are not supported by cartilage as trachea and bronchi are. • Asthma and emphysema • Less air is able to enter and leave the lungs due to the decreased air flow in the bronchioles. • Can lead to heart being affected • Emphysema is even more insidious as pulmonary cells can be destroyed due the constant pressure and scar tissue replaces cells in the lungs and loss of elasticity results.

Respiratory Impairment • Smoking • Cilia paralyzation so particles not swept out • Carbon monoxide • 40 chemicals which are known to cause cancer • Tar – coats lungs and key to lung cancer and also can cause alveoli to become brittle leading to emphysema (inhalation and exhalation is difficult due to lose of elasticity of lungs) • The Benefits of Smoking • Air Pollution • CO, NOx, Cl and CH4 • Problems similar to smoking • If suffering from respiratory problems, pollution can make breathing almost impossible.

Respiratory Impairment • Sneeze: to make a sudden violent spasmodic audible expiration of breath through the nose and mouth, especially as a reflex act. • The nose provides the main route through which inhaled air enters and leaves the lower airways. • Sneezing is a physiologic response to the irritation of the respiratory epithelium lining of the nose. • Chemical release is caused by viral respiratory infections, filtered particles, allergens (substances that trigger allergic reactions) or physical irritants such as smoke, pollution, perfumes and cold air. • This leads to fluid leakage from vessels in the nose, causing symptoms of congestion and nasal drip. Additionally, nerve endings are stimulated, leading to the sensation of itching. • Nerve stimulation and brain reaction • The nervous impulse travels up the sensory nerves and down the nerves controlling muscles in the head and neck, and that leads to the rapid expulsion of air. The high velocity of the airflow is achieved by the buildup of pressure inside the chest with the vocal chords closed. Sudden opening of the cords allows the pressurized air to flow back up the respiratory tract to expel the irritants. This helps to remove offending particles in the nose. • Antihistamines act principally by blocking the action of histamine at receptors located on the blood vessels in the nose. Decongestants stimulate receptors located on the same vessels to cause constriction and lessen the congestion. Topical nasal steroids are used in allergic patients to reduce the number of inflammatory cells and ultimately inhibit the release of histamine.

Respiratory Impairment • Continuous Positive Airway Pressure • Pneumothorax (Collapsed Lung) • Oral vs. Nasal Breathing • THE MODE OF BREATHING, ORAL vs. nasal, is an important determinant of deposited dose of inhaled particles and gases to the lungs (1). The nose can act as an effective filter to prevent penetration of particles and gases to the lower respiratory tract. Gases that are very water soluble or reactive, e.g., SO2, aldehydes, organic esters, and ozone, can be extracted in the nose by up to 95% during resting breathing (18, 32). Very large (>5-µm aerodynamic diameter) and very small (<0.01 µm) particles are deposited very efficiently in the nose by inertial impaction and diffusion, respectively, during nasal breathing (8, 33). In addition, the nose effectively conditions inspired air to near body temperature and 98–100% relative humidity before it enters the lungs (9). The ability of the nose to condition ambient air in these ways serves as a protective mechanism against toxicity to the lower respiratory tract. • Hiccupping

Internal Systems and Regulation