BIOL 1051H Chapter Notes - Chapter 17: Zona Glomerulosa, Zona Reticularis, Adrenal Gland
Endocrine System Part 2
The adrenal gland is located in the abdomen just cranial to the kidneys. This gland also
consists of a part that is a typical endocrine gland (cortex) and a part that is neuroendocrine (the
medulla).
The medulla is located in the central part of the adrenal gland. It is controlled by the
sympathetic division of the autonomic nervous system. It synthesizes and secretes epinephrine
and norepinephrine.
The cortex is controlled by ACTH secreted by the pituitary. It has three layers which all
produce and secrete different hormones. The zona glomerulosa produces mineralocorticoids
which are responsible for electrolyte balance. The zona fasciculate produces glucocorticoids
which are important for the stress response. The zona reticularis produces sex steroids
Both the medulla and the cortex are involved in the stress response. Epinephrine and
norepinephrine ready the body by increasing blood flow and the level of alertness while cortisol
from the cortex increases blood glucose and protein levels.
In the short term the stress response helps an individual deal with changes in their
environment. However, if stress is chronic or long term, the result of continually high
epinephrine and cortisol can cause adverse effects on the body. These effects include atrophy
of hippocampus (involved in memory), reduced sensitivity of tissues to insulin (insulin
resistance), inhibition of vagus nerve activity (stomach upset and cardiac problems), and
suppression of growth hormone, thyroid hormone, and gonadotropins.
Both Glucocorticoid hormones and Aldosterone are released from layers of the adrenal
cortex. Make sure to understand which layers they are released from and what their functions
are in the body
The thyroid gland is located just below the larynx. It secretes the thyroid hormones T4
and T3. These hormones are important is setting and maintaining the basal metabolic rate
(BMR) and are needed for normal growth and development.
The thyroid gland consists of multiple thyroid follicles. The outer layer consists of follicle
cells that take up iodine from the blood and synthesize T4 (most abundant form) and T3. These
remain inside the follicle and do not leave until the gland is directed to do so by TSH, which is
secreted from the pituitary gland. They are able to be kept inside the follicle because they
remain bound to a glycoprotein that is too large and hydrophobic to pass through the walls of
the follicle. The bound T4 and T3 glycoprotein complexes are called thyroglobulin. TSH causes
the hydrolysis of thyroglobulin which releases T4 and T3. Once free of the glycoprotein they
Document Summary
The adrenal gland is located in the abdomen just cranial to the kidneys. This gland also consists of a part that is a typical endocrine gland (cortex) and a part that is neuroendocrine (the medulla). The medulla is located in the central part of the adrenal gland. It is controlled by the sympathetic division of the autonomic nervous system. The cortex is controlled by acth secreted by the pituitary. It has three layers which all produce and secrete different hormones. The zona glomerulosa produces mineralocorticoids which are responsible for electrolyte balance. The zona fasciculate produces glucocorticoids which are important for the stress response. Both the medulla and the cortex are involved in the stress response. Epinephrine and norepinephrine ready the body by increasing blood flow and the level of alertness while cortisol from the cortex increases blood glucose and protein levels. In the short term the stress response helps an individual deal with changes in their environment.
