University:
Glendale Community College
Course:
BIO160 | Introduction to Human Anatomy and Physiology
Academic year:

2022
Views:

470

Pages:

8
Author:

Mia Li

Control of Ventilation • Neural pathways – Conscious: Voluntary motor cortex of frontal lobe of cerebrum sends impulses down to respiratory neurons in spinal cord to respiratory muscles – Unconscious: Neurons in medulla oblongata and pons of brain stem control unconscious breathing • Limitations on voluntary control – Holding breath can lead to loss of consciousness, but breathing will involuntarily resume. Chemoreceptors and Respiratory Rhythm • Chemoreceptors monitor body fluids • Peripheral Chemoreceptors in aortic bodies and carotid bodies monitor blood • Central Chemoreceptors (medulla oblongata) monitor pH of cerebrospinal fluid (CSF) – CO2 easily crosses blood-brain barrier into CSF. The CO2 reacts with water and releases H+ that stimulate central chemoreceptors that strongly stimulate inspiratory center – corrected by hyperventilation, pushes reaction to the left by “blowing off ” CO2 CO2 + H2O  H2CO3  HCO3- + H+ H2CO3 = carbonic acid HCO3- = bicarbonate ion Peripheral Chemoreceptor Pathways Effects of Hydrogen Ions • Respiratory acidosis (pH below 7.35) – caused by hypercapnia (high PCO2) – corrected by hyperventillation • Respiratory alkalosis (pH above 7.35) – hypocapnia (low PCO2) – Can be caused by hyperventillation and can be corrected by hypoventilation or breathing into a bag to increase PCO2 – pushes reaction to the right and lowers pH to normal CO2 + H2O  H2CO3  HCO3- + H+ Oxygen Transport • Concentration in arterial blood – 20 ml/dL – 98.5% bound to hemoglobin, 1.5% dissolved in plasma • Binding to hemoglobin – each hemoglobin molecule contains 4 heme groups – each heme group can bind to one O2 – oxyhemoglobin (HbO2 ), deoxyhemoglobin (HHb) • Oxyhemoglobin dissociation curve – affinity of Hb for O2 is high when PO2 is high – affinity of Hb for O2 is low when PO2 is low Oxyhemoglobin Dissociation Curve Oxygen Dissociation & Temperature Hb has lower affinity for oxygen as temperature increases, therefore, more oxygen is released in active tissues as they heat up. This occurs in the TISSUES, not in the lungs. Active tissues heat up and more oxygen is released PO2 (mmHg) Oxygen Dissociation & pH Hb has lower affinity for oxygen as tissues become acidic, therefore, more oxygen is released in active tissues as they produce lactic acid and carbonic acid. This occurs in the TISSUES, not in the lungs.