Adrenal medulla, Biology

ADRENAL MEDULLA

The adrenal medulla develops from the neuroectoderm of the embryo.

Medulla consists of chromaffin cells or phaeochromocytes. These cells are connected with the preganglionic motor fibres of the sympathetic nervous system.

Hormones : The medulla of the adrenal glands secretes two hormones: norepinephrine (noradrenaline) and epinephrine

(adrenaline). Norepinephrine and epinephrine are derived from the aminoacid tyrosine.

(i) Norepinephrine (Noradrenaline). It regulates the blood pressure under normal condition. It causes constriction of essentially all the blood vessels of the body. It causes increased activity of the heart, inhibition of gastrointestinal tract, dilation of the pupils of the eyes and so furth.

(ii) Epinephrine (Adrenaline). It is secreted at the time of emergency. Hence it is also called emergency hormone. It causes almost the same effects as those caused by norepinephrine, but the effects differ in the following respects.

  • First, epinephrine has a greater effect on cardiac activity than norepinephrine.
  • Second, epinephrine causes only weak constriction of the blood vessels of the muscles in comparison with a much stronger constriction that results from norepinephrine.
  • A third difference between the action of epinephrine and norepinephrine relates to their effects on tissue metabolism.
  • Epinephrine probably has several times as great a metabolic effect as norepinephrine.

Target Cells. Both adrenaline and noradrenaline acts on the cells of skeletal, cardiac and smooth muscles and blood vessels and fat cells.

Because of the role of their hormones, the adrenal glands are also called 'glands of emergency'.

Posted Date: 10/2/2012 6:58:24 AM | Location : United States







Related Discussions:- Adrenal medulla, Assignment Help, Ask Question on Adrenal medulla, Get Answer, Expert's Help, Adrenal medulla Discussions

Write discussion on Adrenal medulla
Your posts are moderated
Related Questions
In many countries of Asia biomass contributes l argely as a source of primary energy. People in rural areas at the peripheries of forests, continue to collect fuel wood from adjace

Flighting adaptations in birds

Explain the Advantages of Double Beam Method? The double beam method has advantage over single beam as it automatically corrects, for the change in light transmission, through

D-glucose differs from D-galactose only in the arrangement around carbon 4. Therefore D-glucose and D-galactose are- Select one: a. enantiomers b. epimers c. mirror ima

Two-Kingdom Classification The history of taxonomy is as old as man himself. It may be traced back to prehistoric times because man had learnt to designate living organisms by

It is made up of three cusps, anterior, posterior and septal. The septal cusp is attached to the medial margin. The anterior cusp is attached to the superior-lateral part of the ma

Question 1) What is megalobastic anemia? Discuss briefly its lab diagnosis. How would you differentiate megaloblastic anemia from other anemias? Question 2) What is hem

Determine How to Calculate the Amount of Nitrogen? The amount of nitrogen can be calculated for this value using the equation: 1000 ml of 1N H 2 SO 4 = 1000 ml of 1N NH 3

Ethylene - Plant Growth Substances This hydrocarbon C 2 H 2 is a gas and is unbelievably a small and simple molecule to be accepted as a hormone. Ethylene is not produced by

What is the life cycle of Trypanosoma cruzi? Trypanosoma cruzi is a heteroxenous parasite, i.e., it has an intermediate host, the triatomine bug, and an ultimate host, the hum