Class 11 Biology Chemical Coordination ADRENAL GLAND


  • One pair of adrenal glands, one at the anterior part of each kidney.
  • It has two types of tissues – adrenal medulla (centrally located tissue) and adrenal cortex (lies outside).
  • It secretes two hormones called adrenaline or epinephrine and norepinephrine or noradrenaline. These are called as catecholamines.
  • These are secreted in response to stress or emergency situations, that is, why they are called as emergency hormones or hormone of Fight or Flight.
  • Role of these hormones – increase alertness, pupilary dilation, piloerection, sweating, increase heartbeat, strength of heart contraction, rate of respiration.
  • They also stimulate breakdown of glycogen (increased glucose concentration in blood), lipids and proteins.
  • Structure of adrenal glands – They are divided into three layers – zona reticularis (inner layer), zona fasciculate (middle layer) and zona glomerulosa (outer layer).
  • Adrenal cortex secretes many hormones commonly called as corticoids.

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