The Plan Introduction – general concepts Anatomy Mechanics – moving air into the lungs –Structures, pressure changes Gas Exchange – moving air from the lungs to blood and tissues –Moving O 2 in and CO 2 out of tissues Control mechanisms –Local –CNS 1

Readings - Respiratory McKinley, O’Loughlin, and Bidle, Anatomy and Physiology An integrative Approach, p Control mechanisms: nervous and others

Objectives Describe the general controls of the respiratory system involving skeletal muscles. Understand local controls involving dilation and constriction of blood vessels and bronchioles Explain inputs and controls involving voluntary and involuntary centers in the CNS Describe the functions of the dorsal and ventral respiratory groups 3

4 Controls of Respiration Respiratory Centers and Reflex Controls brain stem spinal cord respiratory system Higher CNS centers body Motor neurons cognition Respiratory control center

5 Control of Respiration How do you control respiration? – what cells directly control inhalation & exhalation? –Control = skeletal muscles involved in inhalation and exhalation These cells control respiratory minute volume. How do you control these cells? –Motor neurons control skeletal muscle. Respiratory minute volume involves the frequency and volume of a respiratory cycle. Is this control voluntary or involuntary? –Both … from several CNS control centers

6 Control of Respiration How does one know when control is needed? Where do the signals originate? –Cognitive input & input from the 5 senses (visual, auditory, olfactory, gustatory, touch) – function through control centers in the brain stem –Sensory inputs from the body also function through control centers in the brain stem Chemoreceptors Baroreceptors others

Mechanisms that control breathing 1. Motor neurons control skeletal muscles (diaphragm, intercostals and accessory muscles for increased breathing) 2. ● Local controls for systemic blood flow in arterioles. ● Local controls in the lung for blood flow and air flow in the lung. 3. Input from (peripheral) sensory receptors: chemo-, baro-, and proprio-receptors 4. Control centers within the CNS 7

8 1. Controls of ‘Respiratory’ muscles

9 Control Mechanisms & Respiration The distribution of gases (O 2 and CO 2 ) associated with blood or the spaces in the lung is carefully coordinated. The movement of gases is influenced by: –Partial pressures, gradients, pH, temperature, gas solubilities –Changes in blood flow –Changes in depth and rate of respiration This involves: –responses to stimuli from a systemic (the body) location & –excellent coordination between the respiratory and cardiovascular systems called - –Ventilation-Perfusion Coupling Air/Gas flow Blood flow

10 Controls: flow of a gas or liquid To increase the amount of a gas or liquid, you open up the tube – you dilate that tube … To slow (restrict) flow of a gas or liquid, you constrict the tube … Remember: O 2 is good and CO 2 is bad so … –you want to remove CO 2 and bring in O 2 Scenerio: muscle cells in interstitium are very active, so … –O 2 is needed for metabolism; O 2 is donated to cells so O 2 in blood decreases … also –CO 2 is produced after metabolism and P CO 2 in blood increases fasterslower = vasodilate & bronchiodilate = vasoconstrict or bronchioconstrict concept

Co ntrol of gas movement in blood or air spaces Constriction & dilation occurs in arterioles and bronchioles –these are the ‘control’ points for the cardiovascular and respiratory systems –because they have smooth muscles oriented around their small lumens and their branches support many cells Constriction or dilation in arterioles or bronchioles results in: –altered blood flow through capillaries. –altered air flow into and out of alveoli. 11

2. Controls: Systemic Gas flow in the organ systems, eg. muscle cells Muscle cells in interstitium are very active. According to the partial pressure gradients: - O 2 is given to muscle cells for metabolism - CO 2 is being produced after metabolism and released 12 Released CO 2 causes smooth muscle cells around systemic BVs to relax = vasodilation Blood flow increases, CO 2 leaves & more O 2 enters via blood Systemic capillary In the systemic capillary: - P O 2 is decreased from 95 to 40mm Hg - P CO 2 is increased from 40 to 45mm Hg The control - Copyright 2009 Pearson Education Inc. publishing as Pearson Benjamin Cummings

13 2.Controls: within the lungs Ventilation-Perfusion Coupling 1.Blood flow through alveolar capillaries is directed toward lung lobules where P O 2 levels are relatively high and (CO 2 levels are low) 2.Smooth muscle cells in walls of bronchioles are sensitive to CO 2 –Increased P CO 2 causes bronchiodilation

Ventilation-Perfusion Coupling  For gas exchange to be optimal in the lung, perfusion through blood vessels has to match air compositions in the alveoli - if alveoli are well ventilated = high O 2 and low CO 2 – pulmonary arterioles dilate and blood flow is directed to that area to pick up O 2. - if alveoli are poorly ventilated = low O 2 and high CO 2 – pulmonary arterioles constrict and blood flow to that area is decreased.  Bronchiole diameter parallels CO 2 levels a. if CO 2 bronchioles dilate -- CO 2 and O 2 enters b. if CO 2 bronchioles constrict 14

Ventilation-Perfusion Coupling 15 Increased O 2 in lungs correlates with increased blood flow = vasodilation lung BVs = CO 2 increased

Controls: bronchioles and arterioles in the lung 16 Increase CO 2 causes bronchioles to dilate and arterioles to constrict (a) Changes in bronchioles (b) Changes in arterioles

17 3.Controls: (peripheral) sensory information into the CNS Sensory Modifiers of Respiratory Center Activities –Chemoreceptors are sensitive to P CO 2, P O 2, or pH of blood or cerebrospinal fluid –Baroreceptors in aortic or carotid sinuses are sensitive to changes in blood pressure Stretch receptors respond to changes in lung volume –Proprioceptors from the periphery – signals indicating position in space of limbs –Irritating physical or chemical stimuli in nasal cavity, larynx, or bronchial tree - COUGHING AND SNEEZING –Other sensations including pain, changes in body temperature, abnormal visceral sensations

18 Controls of Respiration Chemoreceptors –monitors changes pH either induced by P CO 2 or independent of P CO 2 (kidney failure) –in carotid or aortic bodies (in carotid & aortic blood vessels) –leads to increased rate and depth of respiration when pH goes down Chemoreceptors –monitors changes in pH due to changes in blood P CO 2 in the CSF – sensitive to 5mm Hg change –on ventrolateral surface of medulla oblongata –increased blood P CO 2 causes a decrease in CSF pH –causes increased rate and depth of breathing Peripheral Central

19 Controls of Respiration Baroreceptors 1. monitor blood pressure; located in carotid sinuses and aortic arch –when blood pressure falls - respiration rate increases 2. baroreceptors in bronchioles and visceral pleura also monitor pressure and inhibit over stretching of lungs (Hering-Breuer reflex) Proprioreceptors –monitor limb position is space –Increase breathing when body movements increase Irritant receptors –coughing and sneezing – require elevated intake of breath

20 3.Controls of the Respiratory System Internal Chemoreceptors Receptors of other Reflexes Baroreceptors Proprioceptors Irritant receptors

21 4. Controls of the Respiratory System Dorsal Respiratory Group (DRG) Ventral Respiratory Group(VRG) Pontine respiratory center

22 4. CNS Control of Respiration The Respiratory Center = brain stem nuclei Pontine respiratory system –modifies information into the medullary center and regulates transition from inspiration to expiration Medullary respiratory system –Dorsal respiratory system (DRG) Receives sensory information and relays information to the VRG –**Ventral respiratory group (VRG) Initiates neural impulses for quiet breathing via the the spinal cord and the diaphragm and internal intercostal muscles

23 Controls: from the CNS Voluntary Controls – input from higher brain centers –Cognition into cortex; emotions from frontal cortex; limbic system; hypothaIamus. into medullary respiratory system then to motor neurons in spinal cord OR directly to motor neurons that control skeletal muscles associated with respiration Involuntary Controls – input into brain stem nuclei –Input from receptors (chemo-, baro-, proprio,etc.) in the body into DRG of the medullary respiratory system. Output to VRG –VRG signals the motor neurons controlling skeletal muscles associated with respiration

24 Control of Respiration Ventral Respiratory Group (VRG) - Inspiratory center – controls diaphragm and external intercostals - Functions in quiet and forced breathing Dorsal Respiratory Group (DRG) - relays information to VRG Copyright 2009 Pearson Education Inc. publishing as Pearson Benjamin Cummings

25 Respiratory Rhythmicity Quiet Breathing –VRG (ventral respiratory group: inspiratory neurons) activated for 2 sec. Stimulates motor neurons and inspiratory muscles (diaphragm and ext. intercostals) –VRG inspiratory neurons inactivated by VRG expiratory neurons for 3 sec. Allowing passive exhalation Altered Breathing Rate and Depth –Sensory inputs (chemo, baro, proprio, etc.) into DRG –Rate varies by altering inspiration vs expiration times –Depth varied by engaging accessory muscles

26 Control of Respiration SIDS (sudden infant death syndrome) marked by the sudden death of an infant that is not predicted by medical history (wikipedia) –Some evidence of a disruption of the normal respiratory reflex pattern –May result from connection problems between pacemaker complex and respiratory centers –

27 Controls of the Respiratory System