A momentary stimulus which activates this division can result in a response which lasts for 5 to 15 minutes. What the dog is responding to is the smell of the sweat. If it is highly acidic then you are either afraid or preparing to attack, and the dog will respond by increasing its alertness. If it is neutral then you are relaxed and offer no threat. The sexual response appears to be opposite to what common sense would dictate.
Sexual arousal is a relaxation response.
Anxiety often interferes with arousal, preventing it or diminishing its effects. Since the effects of the ANS are determined not by absolute activation but by balance and change, it is possible for sexual arousal to take place whenever there is an increase in parasympathetic activity compared to its former level. Sexual orgasm is controlled primarily by the sympathetic division. Orgasm can be accompanied by a sudden rush of blood to the internal organs, chilling of the skin dilation of the bronchi, producing a sudden, gasping intake or air a refractory period during which most internal stimuli are ignored and further arousal is difficult. This latter is due to the persistent circulation of adrenaline in the bloodstream.