L11 Flashcards
Normal gas exchange requires both that alveoli are …. and …. with …. at the appropriate rate
adequately ventilated
perfused
pulmonary blood
alveolar ventilation : perfusion ratio:
V delta/Q = Alveolar ventilation rate / Pulmonary blood flow
alveolar ventilation : perfusion ratio:
the mean value under normal conditions is aprox…..
0.8
Where does this rhythmical activity (breathing) originate?
Breathing is controlled in the brain stem (Medulla and Pons)
How is the rate and depth of respiration controlled?
.
Wymień Components necessary for rhytmical activity of breathing
- Chemoreceptors for PO2 or PCO2
- Mechanoreceptors in the lungs and joints
- Control centres for breathing
- Respiratory muscles
How is the respiratory rhythm generated?
Dorsal and ventral respiratory neuronal groups in the medulla elicit reciprocal activation of the inspiratory muscles (diaphragm and
external intercostal muscles) causing the muscles to shorten and
expanding the volume of the chest
During active expiration there is activity of the….
intercostal muscles
Opisz the Hering-Breuer reflex
The smooth muscles of the upper airways (trachea, bronchi and bronchioles) have stretch receptors which during inflation send impluses to the dorsal respiratory group via the vagus to inhibit respiration. This is not normally active in quiet respiration but may play a role during exercise.
Wymień i opisz factors affecting regulation of respiration apart from the main neurogenic drive (2):
1) Chemical factors
A rise in Pco2
A rise in [H+] Chemoreceptors
Fall in Po2
2)Other neural factorsExplain what happens When the O2 in the inspired air falls below 14% (normal 21%) (carotid body)
The resultant hypoxia reduces the synthesis and release of dopamine and the sensory nerve endings
then generate impulses which stimulate the
respiratory centre.
Explain what happens While PO2 is within the normal range (carotid body)
dopamine is released, hyperpolarising
the nerve endings and inhibiting their discharge.
Carotid body contains…
Contains unmyelinated sensory nerve endings and dopamine containing cells and both are closely
associated with capillaries.
Central chemoreceptors adaptations to:
• High altitude
• Chronic respiratory
disease
Central chemoreceptors detect …
it detects only hydrogen ion concentration
Chemoreceptors (podział i opis)
1. Central
CSF H+ (minute-minute)
2. Peripheral
Increased arterial PCO2 (seconds)
Decreased arterial PO2
Decreased arterial pH (carotid only not aortic bodies). Longer term metabolic compensation.Respiration is mainly stimulated by: (3)
An increase in PCO2 (hypercapnia)
A change in arterial pH
A lack of oxygen, low PO2 (hypoxia)
Respiration actions when increased (Pco2, H+ and acidity)
Fall in CO2
Decrease in plasma [H+]
Respiratory Alkalosis
Respiration actions when decreased (Pco2, H+ and acidity)
Rise in CO2
Increase in plasma [H+]
Respiratory Acidosis
Wymień REFLEX CONTROL OF RESPIRATION (6):
- Hering-Breuer lung inflation reflex
- Cough and sneeze
- Swallowing
- Pulmonary chemoreflex
- Other neural factors
- Voluntary control e.g. “Ondine’s curse”
Wymień Pulmonary chemoreflex causes (3):
Smoking or inhalation of noxious gases
Increase mucus production
Bronchial constriction
Wymień Other neural factors (3):
Exercise
Pain
Cold
Przypomnienie: Cough and sneeze
Antitussive medications often include the opiate Codine which depresses the “cough centre”. It has side effects such as decreasing bronchiole secretions which thicken the mucus in the lungs and inhibits ciliary activity, reducing clearance from the lungs.
New factors in dark chocolate found to be much more effective but are not yet available clinically.
Przypomnienie: Pulmonary chemoreflex
Chemical stimuli acting on irritant receptors on myelinated fibres in the upper airways and/or C-fibre receptors in the lower airways, cause:
coughing
increase mucus production
bronchial constriction
The factors that cause pulmonary chemoreflex reactions include;
ammonia, sulphur dioxide, cigarette smoke, and
endogenous inflammatory mediators.
Przypomnienie: Voluntary control e.g. “Ondine’s curse”
Bulbar poliomyelitis and certain brainstem lesions result in loss of the automatic regulation of respiration without loss of voluntary control.
Ondine’s curse is a rare and severe form of central sleep
apnea syndrome caused by lack of automatic respiration
control during sleep.
WHAT DO THE LUNGS DO? (5 i opisz):
GAS EXCHANGE
Exchange of O2 and CO2 in the lungs
ACID-BASE BALANCE
Acts because lungs regulate the level of CO2 in the blood bicarbonate is an important blood buffer
SPEECH
Due to ability to voluntary control activity of respiratory skeletal muscles and therefore change airflow through the vocal cords
DEFENCE MECHANISMS
Airway warms and humidifies air
Intrinsic cells and some reflexes protect the lungs from pollutants
METABOLISM
Some pulmonary cells modify bioactive materials
