Process by which oxygen is supplied to cells and carbon dioxide is removed.
Breathing rate, and amplitude are the two measurements we are interested in.
oNormal rate of respiration – 12-16 breaths per minute.
oUsual depth (tidal volume) is about 400-500 ml for healthy adults.
Direct or indirectly measured:
oDirect – also allow one to assess nature and amounts of gases like CO2 that are being expired from
the lungs. Also the inspiratory duty cycle can be measure directly, which is the ratio of inspiratory
duration to the total respiratory cycle duration.
Mean inspiratory flow – another measure that provides important information about the
CNS on respiration. – it appears to reflect central inspiratory drive and it can be
quantified using the ratio of tidal volume to inspiratory duration.
Often used as a check for possible artifacts in other response measures caused either by breathing
irregularities or by changes in breathing due to an experimental manipulation that might confound the
measure of interest, such as HR.
Deep breath – intentional or not, can often bring about a greater change in ANS function than will
manipulation of the independent variable.
oEx – Stern + Anschel – had subjects take 4 different types of breaths and recorded the effects on
finger pulse volume, HR, and skin resistance.
Extent of ANS disturbance varied directly with the depth of the inspiration. Deeper
breaths leading to a decrease in skin resistance and increase followed by a decrease in
HR, and vasoconstriction in the finger.
RSA – respiratory Sinus Arrhythmia – Ludwig (1847) – refers to the rhythmic increases and decreases in HR
produced by normal respiration in many subjects.
oAs a person inhales, the heart rate increases – as the person exhales, the heart rate decreases.
oArises from both afferent connections from the lungs to CNS, and from CNS respiratory rhythm
oProvides a reasonable estimate of the effects of the Parasympathetic nervous system on the heart,
and is particularly useful BC it is measured uninvasively.
Modified by both CNS and ANS – specifically PNS
Medulla and pons contain respiratory areas – contain respiratory generator neurons which spontaneously fire
bursts of action potentials that initiate inspiration.
Connections to the cortex, the hypothalamus, and other brain stem areas. In addition, several autonomic
reflexes arising from the lungs, upper airways, heart, and blood vessels also modify respiration.
Hering-Breuer reflex – inhibits inspiration and prevents further over-inflation of lungs, it does not operate
during normal respiration, but appears to protect against over-inflation.
Highly responsive to changes in Oxygen and CO2
oChemosensitive areas on the brainstem are part of the respiratory center and are directly stimulated
by an increase of hydrogen ions in the cerebrospinal fluid, which is highly dependent on levels of
oCO2 is much more important in the regulation of respiration than oxygen
Mechanical changes in thorax
oAccompany inspiration and expiration are particularly important for psychophysiology BC they are
noninvasively measurable aspects of breathing.
oJust before inspiration begins, the diaphragm is relaxed, and in this state it forms a dome-shaped
structure that juts up into the area below the ribcage. Also some muscles that attach to adjacent ribs
are relaxed therefore ribs slant downward and forward from their attachments to the spine.
oWhen inspiration is initiated, the diaphragm contracts and flattens, which creates a negative
pressure in the thorax which forces the lungs open. Intercostal muscles contract which raises the
ribs so they are more nearly perpendicular with the spine and also puts the sternum forward.