Lecture 2 objectives - Respiration II.doc

Lecture 2 objectives - Respiration II.doc - Lecture 2...

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Lecture 2 objectives 1. Describe the two actions of breathing in connection with gas exchange 2. Describe the effector muscles involved in quiet and in forced inspiration. Diaphragm o Main inspiratory muscle o Attached to lower ribs, sternum, and vertebral column o Separates abdominal and thoracic cavities o Innervated by one of the two phrenic nerves (originates in cervical plexuses) Each phrenic nerve passes along each side of the trachea o Quiet breathing Diaphragm moves about 1 – 2 cm o Forced breathing Diaphragm moves up to 10 cm o When contracting, diaphragm moves downward increases volume of thoracic cavity External intercostal muscles o Even if they are paralyzed, breathing will still occur unimpaired o Contraction of these muscles pulls the ribs upwards, forwards, and outwards Results in increase of front-to-back diameter of chest Accessory muscles o Do not contribute to quiet breathing o Used during exercise they contract vigorously o Includes scalene muscles of neck and sterneidomastoid 3. What would happen if you cut the phrenic nerve? Diaphragm paralysis Disability occurs in which one would not be able to breathe on their own 1
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4. Describe the effector muscles involved in quiet and in forced expiration . Expiration occurs by elastic recoil of the lungs and rib cage Abdominal wall muscles o Includes rectus abdominis, internal and external obliques, and the transversus abdominis o When contraction occurs, pressure increases in abdominal cavity which pushes the diaphragm into thoracic cavity o Contraction also occurs during coughing, vomiting, and defecation Internal intercostals o When contraction occurs, the ribs are pulled downwards, backwards, and inwards 5. What is the relation between airway resistance and airway diameter? List the diseases that can increase airway resistance Airway diameter affects airway resistance by regulating how much air can be inspired (breathed in). Airway diameter is controlled by autonomic nervous system Airway diameter is reduced in patients with chronic obstructive pulmonary disease o Asthma o Bronchitis o Emphysema As airway diameter increases, airway resistance decreases As airway diameter decreases, airway resistance increases Inversely proportional 6. Describe the actions of epinephrine and acetylcholine on airway diameter. What adrenergic receptors and what cholinergic receptors are involved? Epinephrine causes an increase in airway diameter o 2 Adrenergic receptors involved Acetylcholine causes a decreases in airway diameter (increases formation of mucus) o Muscarinic receptors involved o Cholinergic activity important cause of asthma Asthma relieved by muscarinic antagonist atropine 7. List the locations and functions of the nerve centers that make up the “central controller” of respiration central controller in the brain stem o mainly medulla 2
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