[nemoisemo14]

Blood flow is an involuntary action, how would the nervous system affect it if I were scared or nervous?

[herman m]

The brain controls the heartrate, therefore controlling the bloodflow.

[mr.answerman]

If you were scared then you would be under the influence of an active sympathetic nervous system. This branch of the autonomic N/S is responsible for the flight or fight response to stressors like being face to face with a giant grizzly bear and you are not at the zoo. This would release copious amounts of adrenalin from the adrenal medulla, it would both speed up the heart rate and cause a stronger contraction of the the heart. This would have the effect of increasing blood flow and blood pressure. Next it would divert blood flow to the muscles from the core of the body. Thus it would slow down digestion, urine production. Because of the adrenalin it would dump a bunch of glucose in your blood for increased energy. All of this to help you fight off that bear. Oh by the way you would lose in a fight with a grizzly and become bear food.