Biological Psychology Practical Class 5: Respiration PDF

5. Respiration The respiratory system has three major functions: it provides the body with oxygen (O2), provides an outlet for carbon dioxide (CO2), and contributes to the regulation of the pH level (acidity) of the blood. These functions are closely tied to each other. Also, the respiratory...

5. Respiration The respiratory system has three major functions: it provides the body with oxygen (O2), provides an outlet for carbon dioxide (CO2), and contributes to the regulation of the pH level (acidity) of the blood. These functions are closely tied to each other. Also, the respiratory system works in tight conjunction with the circulatory system. Fig 5.1. Normal, regular breathing pattern. Upper part: changes in the temperature of air near to the nostrils. Lower part: changes in the circumference of the chest The respiratory system is characterized by cyclic activity, i.e., the continuous alternation of inspiration and expiration (Fig 5.1). The upper part of the respiratory system is responsible for the preparation of the air that reaches the lungs, including filtering, warming up and increasing its relative humidity. The lower part (trachea, bronchial tubes) forms the pathway through which the air can reach various parts of the lungs. Inspiration is caused by the synchronized activity of external intercostal muscles and the diaphragm. Their coordinated movement increases the overall volume of the thoracic cavity, including the lungs (Fig 5.2, left-hand figure). This leads to the decrease of air pressure within the lungs compared to the external air pressure, which will be equalized by the flow of air into the lungs. During expiration, the aforementioned respiratory muscles come in a relaxed state (forced respiration is also possible dominantly via the internal intercostal muscles and the abdominal muscles), which leads to the decrease of the volume of the thoracic cavity (Fig 5.2, right-hand figure). This generates a relative overpressure in the lungs, that will be reduced by the flow of air in the external direction. Fig 5.2. The anatomical basis of inhalation and exhalation. Source: https://www.medicalnewstoday.com/articles/319924 As its partial pressure in the air is higher than that in the blood, a proportion of O 2 in the air diffuses into the blood in the pulmonary capillaries, enters the red blood cells, binds to haemoglobin and becomes transported to almost all parts of the body in order to maintain key energy producing metabolic processes (so-called aerobic processes). The very same processes produce CO 2, which is transported partly by the red blood cells (bound to haemoglobin, just like O2), partly by the blood plasma dissolved in solution, and partly buffered with water (in form of H + and bicarbonate; this plays a role in the maintenance of pH level of the blood). As the partial pressure of CO 2 is higher in the blood that reaches the lungs than in the air in the lungs, it diffuses from the former to the latter. Fig 5.3. Irregular breathing pattern during speaking (lower part) 2  Under normal circumstances, the frequency and depth of respiration is controlled by the spontaneous activity of respiratory generator neurons of respiratory centers located in the medulla and the pons. This regulation is based on input from chemoreceptors in the arteries and the medulla (the most important source of information are the actual concentration of CO 2 and H+ in the blood, not that of O2), from stretch receptors in the lungs and also from additional sensory receptors located in various parts of the body. Autonomic reflexes, relying on visceroceptive input, also play a role. The average resting respiratory rate is 12-14 cycles/minute, the average amount of air moved in and out, called tidal volume, is 400-500 ml for healthy adults. The ratio of time required for inspiration to the total time of a full respiratory cycle (Tinsp/Ttotal, called respiratory or inspiratory duty cycle) is about 0.4. This basic pattern is influenced by higher level voluntary and involuntary factors (e.g. it is controlled during speech and fine movements or high demand cognition that require attention, respectively; see Fig 5.3). Fig 5.4. Pattern of hyperventilation If the depth and rate of breathing is increased due to automatic regulatory processes or intentional changes, we speak of hyperventilation (Fig 5.4). In the long run, it leads to the loss of H + in the body, which shifts the pH level to the alkaline direction (i.e. above the normal range of 7.35- 7.45). Reduced depth and rate of breathing, called hypoventilation (Fig 5.5), is characterized by the increase of the concentration of CO2 (including H+) in the blood, i.e., a shift to the acidic direction. 3 Fig 5.5. Pattern of hypoventilation The simplest way to track respiration is measuring the expansions and contractions of the chest using a pneumograph transducer (strain gauge), that converts changes in strain caused by change of the circumference of the thorax to changes in voltage (Fig 5.6). This method enables us to calculate respiratory rate but it is insufficient for the measurement of the exact amount of air inhaled (e.g. tidal volume) or the composition of the exhaled air (i.e. concentration of O2 and CO2). For the latter purposes, spirometry and breath gas analysis are used, respectively. Fig 5.6. Measurement of respiratory activity with the Biopac system. Source: Biopac Student Lab v4.1.3 software, BIOPAC Systems, Inc. Respiration is related to a number of psychological phenomena, such as speech, attention, laughing, sighing, smelling, and emotion (including anxiety disorders and stress). Mirroring the breathing pattern of the partner during social interaction indicates affiliation with the other person. 4 Beyond these mostly automatic processes, the feature that ventilation can be voluntarily controlled has been utilized in various various ways since thousands of years. For example, voluntary hyperventilation can lead to altered states of consciousness, such as in holotropic breathing, but also to panic attack. Also, meditation and relaxation techniques, typically aiming at a regular, calm breathing and passive observation of breathing, can effectively reduce stress and anxiety. Fig 5.7. The POWERBreathe 5 device, used to measure perception of respiratory resistance. Source: https://www.powerbreathe.com/product/k5/ The increase of the concentration of CO 2 in the blood and difficulty of breathing due to increased respiratory resistance lead to hunger for air (aka breathlessness), a particularly unpleasant body sensation indicating a possibly dangerous condition that should be eliminated. From a measurement point of view, altered respiratory patterns are able to change other measures, most importantly heart rate (Chapter 6) and electrodermal activity (Chapter 8). This can lead to artefacts (the impact of respiration might be comparable to that of experimental manipulation), as well as interesting phenomena that are worthy if investigation on their own, such as respiratory sinus arrhythmia (RSA), i.e., the cyclic changes of heart rate caused by normal respiration (heart rate increases during inhalation and decreases during exhalation) (Chapter 6). Goal of the class: Demonstration of the basics of respiratory recording (Biopac Student Lab Lesson L08 – Respiratory cycle) and the measurement of respiratory resistance (Powerbreathe5 device) 5