8 - Breathlelssness and control of breathing (awake) Flashcards
What is the main functions of the respiratory muscles?
- maintenance of arterial PO2, PCO2 and pH (pH is probably the most important)
- defence of airways and lungs (coughing, sneezing)
- exercise: fight and flight
- speech
- control of intrathoracic and infra-abdominal pressures e.g. for defection, belching and vomiting
What is TTOT?
duration of a single reparatory cycle (breath)
at rest —–> 4 seconds
(frequency = 60/TTOT, therefore frequency=4)
What is VE?
Minute ventilation OR expired volume
What do TI and TE stand for?
TI = inspiratory duration TE = expiratory duration
TTOT = TI + TE
What area of the brain is the voluntary centre of the control of breathing?
motor area of the cerebral cortex
What nerves are involved in reflexes of breathing?
cranial nerves (fromt he brainstem not the spinal chord)
Which nerve is involved in the sneeze reflex?
trigeminal nerve (V) afferents detect irritants int he nerves and face
Which nerve is involved in the gag reflex?
glossopharyngeal nerve (IX) afferents detect irritants from the pharynx and larynx
Which nerve is involved in the cough reflex?
vagus nerve (X) afferents detect irritants from the bronchi and bronchioles
Which nerve is involved in the Hering Breuer reflex?
vagus nerve (X)
(stops lungs overexpanding/signal to stop inspiration)
afferents detect stretch from the lungs
NOTE: there is also a detection of expansion from he chest wall and stretch or respiratory muscles via thoracic spinal chord
How is breathing centrally controlled?
Name the specific complex that generates the respiratory rhythm
centrally controlled by a group of neurones in the medulla
- Pre-Botzinger complex is essential for generating the respiratory rhythm
Describe the CNS control of breathing - what are the 2 centres that are used to control the amount that we breath?
- involuntary (metabolic) centre in the medulla
- voluntary/behavioural centre in the motor cortex
Where does the behavioral/voluntary control lie in the motor homunculus?
between the hip and the trunk
What 2 inputs into the metabolic centre allow it to keep parameters in the normal range?
- detection of H+ in nearby ECF
- chemoreceptors in carotid body detect H+, PCO2, PO2 in blood
How can the lungs feedback on the metabolic centre?
- if they are being overworked (can become damaged)
- there is feedback from muscles and stretch of lungs to metabolic centre to stop inspiration
Where do the following 5 systems/actions fit into the system?
- limbic system (survival responses)
- emotion (frontal cortex)
- sensory inputs (pain)
- the voluntary centre
- sneeze and cough reflexes
- limbic system, frontal cortex and sensory inputs act directly on the metabolic centre
- behavioural controller and sneeze/cough receptors act on the respiratory spinal motorneurones
Where are the carotid bodies and what do they detect?
at the bifurcation of the common carotid artery in the neck
- detect H+, PCO2, PO2 in blood
Are the chemoreceptors in the carotid bodies described as having a slow or rapid response?
rapid response
because changes occur rapidly in the carotid body as H+, CO2 and O2 can easily diffuse from the blood into it
Is the detection of H+ in the ECF (by the metabolic centre) described as having a slow or rapid response?
Slow response
because it takes time for ECF acidity to change
What are the factors that affect the response/sensitivity to CO2?
- Hypoxia (potentiates the response)
- Acidosis (potentiates the response)
(since usually, blood acidity correlates with CO2 levels)
What are the principle ions/molecules involved in acid bar balance and where are they controlled from?
Which of thee is a slow reaction and which a quick one?
- bicarbonate —–> kidneys (slow)
- CO2 —–> lungs (fast)
