control of breathing Flashcards
where is the respiratory centre of the brain?
the medulla and pons in the brainstem
what is the function of the respiratory centre of the brain?
produces uninterupted rhythmic breathing activity
Describe the dorsal respiratory group
- located in the dorsal region of the medulla
- recieves afferent signals from glossopharyngeal & vagus nerve
- dorsal respiratory group (DRG) primarily fire
during inspiration and have input to the spinal motor neurons
that activate respiratory muscles involved in inspiration—the
diaphragm and inspiratory intercostal muscles
Describe the ventral respiratory group
- located on the ventral region of the medulla
- control expiration
- expiratory neurons appear to be important during exercise/strenous physical activity
what is the pre-botzinger complex in the upper part of VRG?
it is the respiratory rhythm generator
where do the repetitive bursts of action potentials travel to?
the diaphragm and inspiratory muscles
what are the 3 key areas in the medullary respiratory centre?
- dorsal respiratory group
- ventral respiratory group
- pre-botzinger complex upper part of ventral respiatory group
Describe the neural generation of rhythmical breathing
- the groups of neurons have the properties of periodic firing & are responsible for the basic rhythm of ventilation
- they generate repetitve bursts of AP’s going to the respiratory muscles
- during inspiration, the AP’s increase creating a ‘ramp-like’ pattern and increasing the inspiratory muscle activity
- expiration occurs as the elastic lung recoils
what is the diaphragm innervated by?
the phrenic nerve
where is the apneustic centre located?
the pons
what is the effect of the apneustic centre?
- the impulses of this centre have an excitatory effect on the inspiratory area of medulla
- they prolong the ramp action of AP’s
what is the function of the pneumotaxic centre in the pons?
- inhibits inspiration
- modulates the apneustic centre in the pons
- finetunes the transition from inspiration to expiration
what is inspiration initiated by?
Inspiration is initiated by a burst of action potentials in the
spinal motor neurons to inspiratory muscles like the diaphragm.
what is the primary inspiratory muscle at rest?
the diaphragm
what type of cells is the respiratory rhythm generator (pre-botzinger complex) made up of?
pacemaker cells and a complex network of neurons that act together to set the basal respiratory rate
what occurs when the inspiratory neurons stop firing?
the inspiratory muscles relax which allows passive expiration
Describe is an example of a cut off signal for inspiration?
hint - its a reflex
- the pulmonary stretch receptors which are ativated by a large inflation during inspiration
- AP’s in the afferent nerve fibres in the stretch receptors travel to the brain & inhibit the activity of the medullary inspiratory neurons
- called the hering-breuer reflex
how do chemoreceptors alter the rate of breathing?
- they have important inputs to the respiratory centre eg the rate of inspiration / expiration can be increased or decreased when the** levels of arterial oxygen decrease** or when the** levels of arterial CO2 increase**
what are the peripheral chemoreceptors and where are they located?
- peripheral receptors - ie below the CNS
- they are located high in the neck
- eg carotid bodies and aortic bodies
where is the central chemoreceptors located and what does it respond to?
- located in the medulla
- responds to increased H+ concentration in the brain ECF
what is hyperventilation?
breathig in excess of the metabolic needs
what is hyperpnoea?
increased breathing that matches the metabolic needs
what is tachypnoea?
increased brathing above normal (more than 20 per minute), often rapid and shallow breathing
what is hypoventilation?
breathing that is **insufficient to meet the metabolic needs **
what is apnoea?
an absence of airflow due to a lack of respiratory effort or airway obstruction
