Week 8- Breathing Flashcards
Muscles of Respiration
- Intercostal muscles
- Internal
- External
- Diaphragm
- Accessory muscles
- sternocleidomastoid
- scalenes
- abdominal
- pectoralis minor
Inspiration
Based on pressure changes
- Happens when the atmospheric pressure is higher than the intrathoracic pressure. Pressures naturally will move from high to low
- Active
Expiration
- Based on pressure changes
- Happens when the atmospheric pressure is lower than the intrathoracic pressure
- Passive
Control of Breathing
- Respiratory centre in the brain stem
- Groups of neurons in the pons and medulla
Inspiratory Center:
- Thought to be the “pacemaker” of the respiratory control centre
- Rhythmically depolarize and send impulses via: the phrenic nerve to the diaphragm and intercostal nerves to the external intercostal muscles
- Muscles contract - inspiration
- When they stope sending impulses - relaxation and expiration occurs
Expiratory Center:
- When deeper and more forceful expiration is required - frequency of impulses is increased
- Impulses to the internal intercostal and abdominal muscles - forceful expiration
- Not involved during normal breathing, only active when the expiratory muscles are needed during forced expiration
Pons Respiratory Centre
- Coordinates actions of the Medullary Centre to produce a smooth breathing process
- 2 types of neurons: stimulating neurons, inhibitory
- Either increase or decrease the depth and length of inspiration
- Homeostatic balance of rate and depth respirations
What are some factors that influence the Respiratory Center?
- Direct stimulation
- Stimulation through sensors
- Cause adjustments to the rate and depth of respirations
Factors that Influence Breathing
- Feedback to the medulla comes from sensors throughout the nervous system (eg. changes in PO2, PCO2 & PH (hydrogen ions))
PCO2 acts on chemoreceptors located in the medulla
- sensitive to the changes in CO2 and H+ (pH) in arterial blood
- Normal range of PCO2 is 38-40 mmHg
- Stimulation of these chemoreceptors by increased PCO2 results in faster breathing and greater volumes of air moving in and out of the lungs per minute
- Decreased PCO2 results in inhibition of the medulla rhythmicity and slows the respiration
Arterial Blood Pressure
- Arterial BP helps control breathing by acting on carotid and aortic baroreceptors
- Rise in arterial BP creates a slowing of the RR
- Sudden drop increases the rate and depth of respirations
Cerebral Cortex
- Impulses from the motor area of the brain to the respiratory centre may increase or decrease respirations voluntarily (have the ability to control it)
- While you may have the ability to control it to a certain extent- the automaticity of the system will eventually pick up
Inflation/ Deflation Reflex
- Stretch receptors in the visceral pleura are sensitive to the degree of stretching of the lungs
- During inspiration impulses are sent directly to the respiRatory centre via the vagus - inhibits impulses - promotes expiration and deep inspiration
- Hering-Breur reflex regulates the depth and rhythmicity of respiration and thus the Tidal Volume and prevents over inflation
How does Hering-Breur work?
- When the tidal volume of air has been inspired, the lungs are expanded enough to stimulate the stretch receptors located within them
- The stretcher receptors then send inhibitory impulses to the inspiratory centre and relaxation of the inspiratory muscles occur and expiration begins
- One expiration is done, the reflex is stimulated again and inspiration occurs again
Higher-brain centres
- Involuntary during periods of anxiety, fear, pain, excitement, or temperature, via the hypothalamus
- Voluntary alteration of respiratory patterns (provided by cerebral cortex and can be overridden by the chemoreceptors)
Body Temperature
Increases in temperature increases the rate of breathing
- Increase in temperature causes O2 to be released from hemoglobin
- Exercise or fever
Decrease in temperature decreases the rate
- Hypothermia
- Decrease in temperature causes metabolism to slow doen- decreased need for O2
