PCP Human Panting

Question 1

What is the hypothesis for the point and the counterpoint?

Answer 1

Point: when humans become hyperthermic, they use panting as a thermoregulatory response

Counter Point: when humans become hyperthermic, they do not use panting as a thermoregulatory response

Question 2

When hyperthermic, humans display an increased ventilatory response; what are two
possible patterns of breathing that can be associated with this?

Answer 2

1. Thermal tachypnea

2. Thermal hyperpnea

Question 3

Compare and contrast thermal tachypnea and thermal hyperpnea

Answer 3

Thermal tachypnea involves an “elevated functional residual capacity, a high frequency of breathing often exceeding 200–300 breaths/min, a reduced tidal volume” and preferential ventilation of the upper airways and nasal turbinates. On the other hand, thermal hyperpnea only occurs with an increase in Tcore. Relative to thermal tachypnea, tidal volume during thermal hyperpnea increases while breathing frequency is decreased, thus resulting in hyperventilation of alveoli

Question 4

a

Answer 4

a

Question 5

What is the proposed mechanism for hyperpnea?

Answer 5

this heat induced hyperventilation is due to either an alteration in the sensitivity of the central chemoreceptor response, or a change in the threshold of which PCO2 increases pulmonary ventilation

Question 6

Evidence for point (when humans become hyperthermic, they use panting as a thermoregulatory response)

Answer 6

Hyperventilation for HEAT LOSS.

1. Rebreathing mixtures, change in response sensivity and threshold was due to rebreahting mixtures. They rebreathed to get certain blood conc. Subjects showed an increase in the sensitivity of their chemoreceptor response; one of the proposed mechanisms of the hyperthermia induced hyperventilation. And change in threshold of PCO2, increasing pulmonary ventilation.
2. They found large reduction of MCA blood velocity due to PaCO2. More than 50% of the reduction in BF was due to hyperpnea.

Question 7

Evidence for counterpoint (when humans become hyperthermic, they do not use panting as a thermoregulatory response)

Answer 7

1. In humans, a change in respiration will only occur once a threshold Tcore has been exceeded. During immersion of hand in hot water bath, concluded that ventilation did not change until a specific Tcore was reached, thus establishing a threshold for hyperpnea. This threshold was far higher than that for sweating and cutaneous vasodilation, and thus cannot be categorized as a thermoregulatory response.
2. Rasch found that when exercising in mild hyperthermia, the skin of the head provides enough heat loss in order to dissipate the heat produced by the brain (when compared to the respiratory system). Found that heat loss via the respiratory system contributed minimally to brain cooling, and that heat loss thru the skin of the head could compensate for an inc in temp alone. Aka panting is not a prerequisite for brain cooling, heat loss through the skin of the head is more than suffice