Answer
If one is being chased by a mugger the body will utilize the physiological flight (fight or flight) response to facilitate escape from the threat. The amygdala will first rechnizete theat and inform the hypothalamus. The hypothalamus will then initiate the sympathetic nervous defences to protect the subject of the threat, To prepare the body for vigorous action the skeletal muscles, heart and brain are favores. he preganglionic neurons of the sympathetic chain are stimulated to secrete acetylcholine which is bound by the nicotinic receptors of the post-ganglionic neurons.,The post ganglionic neurons secrete norepinephrine which affects the target organs, Regarding effects on blood vessels; this varies with the nature f the receptor( alpha or beta adrenergic) on the target cells. In this acute stress reaction skeletal muscle blood vessels dilate and blood flows to that tissue is increased. .Cardiac blood supply muscle is increased. Heart rate, force of contraction and blood pressure increase, . At the same time, blood vessels that supply the digestive tract, kidneys and skin constrict to make available more blood for heart and skeletal muscles. Preganglionic neurons to the adrenals also contribute to the sympathetic response. These neurons secrete acetylcholine which stimulates the postganglionic axons on the adrenal medulla to release norepinephrine and epinephrine into the blood stream . These hormones affect blood vessels variously, constricting some and dilating some, dependent on the kind of adrenergic receptors on the target cells.
Work Step by Step
When a person perceives a threat and is in a fight or flight mode , the sympathetic system affects different organ systems in different ways . But the responses are geared to facilitate the escape of the threatened subject from danger, There are several effects of stress hormone and neurotransmitters on the cardiovascular system: Norepinephrine released from postganglionic sympathetic neurons cause blood vessels in skeletal muscles to dilate. Blood vessels in digestive tract and in other tissues constrict to ensure that the skeletal muscles which are needed for flight or fight has an adequate supply of blood. These effects of the adrenergic neurotransmitter is buttressed and magnified by a cholinergic stimulated release of catecholamines from the adrenal medulla. Late in the stress reaction the hypothalamus causes the the pituitary to release ACTH which stimulates the release of cortisol from the adrenal cortex. One effect of cortisol is to make blood vessel more sensitive to catecholamines.
