By David F. Dean, Department of Biology, Spring Hill College
© 2004 by the National Center for Case Study Teaching in Science. Modified by Camille Freeman and used with permission.
Melanie Johnson is a 32-year-old accountant who moved to Green Bay, Wisconsin two years ago, from her hometown of Sarasota, Florida. Beginning this past November, for the first time in her life, Melanie began experiencing periods of depression, lethargy, and excessive sleeping. In addition, she noted that she was eating more than she had previously, and as a result had gained 10 lbs.
Melanie made an appointment with her physician, who ruled out all potential medical causes of the symptoms she displayed. She was also examined by a psychiatrist to rule out other causes of depression and was diagnosed as having seasonal affective disorder (SAD).
- Describe the exact anatomic location and the structure of the pineal gland, and describe the effect of light on the production of melatonin. (5 points)
ANS:The pineal gland is a secretive gland located at the roof of the third ventricle of the brain, constituting the epithalamus. It lies above the posterior commissure near the level of the habenular complex and the sylvian aqueduct. It is made up of two major cell types, the pineolocytes and interstitial (glial-like cells) that make them secretive in function. The presence of light stimulates their primordial photoreceptive cells by noradrenergic sympathetic nerve terminals causing the gland to stop melatonin production. Melatonin is also by negative feedback inhibition regulated by the suprachiasmic nucleus of the hypothalamus which holds the circadian clock (Williams Textbook of endocrinology, 2011).
- Describe the pathway connecting the photoreceptors of the eyes to the pineal gland. (5 points)
ANS:Photoreceptors of the eye are made up of retinal ganglionic cells which directly innervates the suprachiasmic nucleus (SCN) of the hypothalamus via the retinohypothalamic tract. The SCN in turn stimulates the dorsal parvicellular paraventricular hypothalamic nucleus (PVH). With direct and indirect intrahypothalamic projections, the PVH in turn sends the electrical signal directly to the sympathetic preganglionic neurons in the intermediolateral cell column of the thoracic region of the spinal cord. Sympathetic preganglionic neurons from the spinal cord then transfer electrical signals to the postganglionic neurons in the superior cervical ganglion which ultimately sends the signal to the noradrenergic nerve terminals on the pineal gland (Williams Textbook of endocrinology, 2011).
- How is the pineal gland functionally related to the adrenal medulla? (3 points)
ANS:Both organs are endocrine and are stimulated by sympathetic neurons whose signals are converted to hormone production. The hormones produced by both organs are also produced during a short term physiological need; as catecholamines by the adrenal medulla in response to short term stresses, melatonin by pineal gland to regulate circadian clock in absence of light.
- Describe the condition known as SAD and briefly explain the rationale behind the common medical treatment(s) for this condition. (10 points)
ANS: SAD is a specific type of major depressive disorder characterized by seasonal signs of depression occurring around the season of winter every time of the year. It is a severe form of ‘winter blues’ when the day is shorter in duration than the nights. The body therefore responds to the reduced day light by the symptoms seen in the condition. The common treatment is by Light therapy which exposes the affected person to very bright light simulating sunlight.
- Why do some practitioners recommend supplemental melatonin for “jet lag” and insomnia associated with aging? (5 points)
ANS: The basic function of melatonin is to regulate the circadian rhythm of sleep and wake. Jet lag occurs when the body is unable to make immediate adjustment to our circadian clock due to changes in light cues we receive as a result of rapidly crossing time zones. This problem could be solved by supplemental melatonin to help the body re-entrain the circadian rhythm to the new time zone.
Insomnia associated with aging is caused by the decreased resilience aging causes to the body in order to recover from an initial acrophase period of HPA activation which eventually leads to sleep ultradian rhythm. Aging therefore causes sleep problems which means melatonin production during sleep is affected with consequent disruption in circadian rhythm. It therefore theoretically makes sense for supplemental melatonin to keep circadian rhythm regulated which will promote sleep (Balbo et al,2010).
- Are any serious side effects known to occur as a result of the administration of melatonin? (5 points)
ANS:Although side effects of melatonin supplementation are unknown, it reasons that excessive intake could potentially have a grave effect on circadian rhythm.
- List some environmental stresses that can affect pineal function. (3 points)
ANS:a. Light exposure
b. Temperature variations
c. Noise variations (NIH, n.d)
- Are there any nutrition-based or lifestyle interventions that may affect development or progression of SAD (aside from the obvious one – exposure to sunlight/UV rays)? Select one and explain why it may be helpful. (5 points)
ANS:a. Morning exercise: Exercise helps with natural production of endorphin (feel good hormone) which helps to induce sleep afterwards and hence promote phase advance melatonin secretion. Studies have also suggested a much better treatment of SAD if exercise is done outdoor in the morning or under light (Roecklein et al, 2005).
b. Antidepressant medications
- Does the structure of the pineal gland change as we age? How do we know? (5 points)
ANS:Yes it does, changes occur in the size of the pineal gland as we grow becoming smaller with increasing age. This is evident by the increasing sleep disturbance associated with aging. Aging has also been studied to be associated with increasing crystallization of the pineal gland which has been referred to as corpora arenacea (brain sand). These deposits have been linked to aging; its true function is yet to be discovered (Adams, 2010).
- How did the pineal gland get its name? (3 points)
ANS: The pineal gland had its name from the resemblance to the cone of the pine tree.
Adams, A. (2010). The natural recovery plan: Pineal gland. Retrieved fromhttp://www.thenaturalrecoveryplan.com/articles/pineal-gland.html
Balbo, M., Leproult, R. & Cauter, E. V. (2010). Impact of sleep and its disturbance on hypothalamo-pituitary-adrenal axis activity. Int J Endocrinol 2010; 2010:759234. Doi 10.1155/2010/759234
Lam, R. W. & Levitan, R. D. (2000). Pathophysiology of seasonal affective disorder: a review. J Psychiatry Neurosci; 25(5): 469-480.
Melmed, S., Polousky, K.S., Larsen, R. & Kronenberg, H. M. (2011). Williams Textbook of endocrinology (12th ed)[free eBook chapter version]. Accessed from https://www.inkling.com/read/williams-textbook-of-endocrinology-melmed-polonsky-larsen-kronenberg-12th/chapter-7/pineal-gland
National Institute of Health (n.d). Teachers Guide: Information about sleep. Retrieved from http://science.education.nih.gov/supplements/nih3/sleep/guide/info-sleep.htm
Partonen, T., & Lönnqvist, J. (1998). Seasonal affective disorder.Lancet,352(9137), 1369-1374.
Roecklein, K.A. & Rohen, K. J. (2005). Seasonal affective disorder: An overview and update. Psychiatry (Edgmont); 2(1):20-26. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3004726/#
webMD (n.d). Depression health center: exercise and depression. Retrieved from http://www.webmd.com/depression/guide/exercise-depression
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