Q.Explain how the adrenal medulla and sympathetic nervous system function as a closely integrated system.
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Start your 14-day free trial to unlock the full solution →Sympathetic preganglionic fibres directly innervate the adrenal medulla, which then releases adrenaline/noradrenaline into the blood to extend and prolong the sympathetic 'fight or flight' response.
The adrenal medulla and the sympathetic nervous system are closely linked both developmentally and functionally.
Step 1. Developmentally, the adrenal medulla arises from the same ectodermal tissue as sympathetic ganglia, and functions almost like a specialised, enlarged sympathetic ganglion.
Step 2. During an emergency, sympathetic preganglionic fibres directly stimulate the adrenal medulla (bypassing the usual postganglionic-neuron step), causing it to secrete adrenaline (the '3F'/emergency hormone -- fight, flight, fright) and noradrenaline directly into the bloodstream.
Step 3. These circulating hormones then reinforce and prolong the same effects the sympathetic nervous system produces directly at its own target organs -- increased heart rate, raised blood pressure, redirected blood flow -- but delivered hormonally to every tissue in the body, and lasting longer than direct nerve stimulation alone. …
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