Control of respiration

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  • Created by: Alex
  • Created on: 03-06-13 11:12
what can be adjusted in respiration
frequency of ventilation, depth of ventilation, amount of gas carried in the blood, rate at which blood circulates and perfusion of individual tissues
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what controls the frequency, depth and regularity of ventilation?
the brain - medullary respiratory centre
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what are the main regulating factors?
Blooc PCO2 and [H+] and bloog PO2
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what mainly controls respiration in the brain - central pattern generator
Pons and medulla
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where do the pons and medulla recieve information from?
chemo-receptors in aorta and carotid, stretch receptors in intercostal muscles and cerebral cortex
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two medullary respiratory centres in the pons
apneustic and pneumotaxic
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Stages of control of basic rhythm in medulla
1. input from areas including PONS. Cause medulla to send message to spinal cord, spinal cord phrenic nerve sends message to diaphragm.
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what happens if vagus nerve is cut above pons
Lowers frequency and causes deeper inspiration
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what happens if vagus nerve is cut mid-pons
Apenusis- abnormal pattern of breathing characterized by deep, gasping inspiration with a pause at full inspiration followed by a brief, insufficient release
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what happens if vagus nerve is cut between pons and medulla
gasping inspiration, irregular respiration
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what happens if vagus nerve is cut below medullla
no change - no voluntary resp
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What does the cortex control
voluntary respiration - not involved in involuntary
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Pneumotaxic centre control
Terminates inspiration; switches between inspiration and expiration (‘brakes inspiration”)
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Apneustic centre control
prevents inspiratory neurons from being ‘turned off
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Ventral respiratory group
Inactive during normal breathing; regulates amplitude and frequency; expiratory and inspiratory signals
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Dorsal respiratory group
mainly inspiratory signals via phrenic nerve to diaphragm
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overview of what pons and medulla do
Pons = Switching; Medulla = Amplitude and frequency
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3 factors that influence magnitude of ventilation
PCO2, H+ and PO2
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Peripheral chemoreceptors
principally to detect variation of the oxygen concentration in the arterial blood, whilst also monitoring arterial carbon dioxide and pH - aortic bodies and carotid bodies
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central chemoreceptors
detect the changes in pH of nearby cerebral spinal fluid (CSF) that are indicative of altered oxygen or carbon dioxide concentrations available to brain tissues
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Carotid bodies function
Monitor [H+] and [O2]. afferent nerves go to medulla
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Aortic bodies function
monitor [O2]. afferent nerves go to medulla and pons via vagus nerve
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what medulla and pons do with information from carotid and aortic bodies
integrate this information with - information on blood pH monitored by the medulla - voluntary control from the higher centres of the brain
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how do central chemoreceptors monitor cerebral arterial PCO2
PCO2 by monitoring pH (H+ ions) in ECF
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what does raising the inspired CO2 do?
Increases respiratory minute volume - increases rate an depth of ventilation
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What is acidosis?
when the pH falls below 7.35
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causes of respiratory acidosis
Respiratory depression (drugs, alcohol) Asthmatic airway constriction Fibrosis, pneumonia Emphysema (Chronic Obstructive Pulmonary Disease). Alveolar hyperventilation = CO2 retention
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cause of metabolic acidosis
Raised H+ intake - Lactic acidosis (anaerobic metabolism) Ketosis (elevated fat/protein catabolism) Diarrhoea (excess HCO3- excretion) Poisons (methanol, ethylene glycol) Medicines (aspirin)
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What is alkalosis
When the pH rises about 7.42/5
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causes of respiratory alkalosis
Anxiety [can be partially adjusted by re-breathing a bag of air] Incorrectly adjusted artificial ventilator, Hypperventilation - excess CO2 loss
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causes of metabolic alkalosis
Excessive vomiting (loss of stomach acid) Excess bicarbonate ingestion (antacids)
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Hypoxia
Low PO2 - oxygen deficiency in tissues
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Effects of Hypoxia
Shortness of breath - Headache - Dizziness - Nausea - Fatigue Confusion High-altitude pulmonary oedema (fluid accumulation in lungs)
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What is Hypoxic hypoxia
when PO2 of arterial blood is reduced - causes by altitude without pressurisation and gaseous suffocation
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Anaemic hypoxia
PO2 of arterial blood is normal but carrying capacity is reduced due to low Hb. May be symptomless, except during stress or exercise -Severe haemorrhage - Iron-deficiency anaemia - Blood cell diseases
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What is Ischaemic (circulatory) hypoxia
PO2 and Hb of blood are normal but blood flow to a particular tissue is compromised. -Mechanical injury/trauma - Circulatory damage (e.g. Frost bite) - Thrombosis (e.g. coronary thrombosis
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what is histotoxic hypoxia
PO2 and Hb of blood are normal, and circulation is normal but cells cannot use the supplied oxygen -e.g. cellular poisoninc e.g. cyanide
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effect of H2S (hydrogen sulphide
inhibits cellular respiration >1000 ppm (parts per million) causes collapse withl loss of breathing
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Card 2

Front

what controls the frequency, depth and regularity of ventilation?

Back

the brain - medullary respiratory centre

Card 3

Front

what are the main regulating factors?

Back

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Card 4

Front

what mainly controls respiration in the brain - central pattern generator

Back

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Card 5

Front

where do the pons and medulla recieve information from?

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