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Parafollicular cells (also called C cells) are cells in the thyroid that produce and secrete calcitonin.
Cuboidal follicular cells (also called principal cells) are cells in the thyroid gland that produce and secrete thyroxine (T4) and triiodothyronine (T3).
A goiter (or goitre or bronchocele) is a swelling in the thyroid gland which can lead to pronounced swelling in the neck region.
Worldwide, the most common cause for goitre is iodine deficiency. In countries that use iodized salt, Hashimoto's Thyroiditis (HT) is the most common cause.
HT is an autoimmune disease in which the thyroid gland is gradually destroyed by a variety of cell and antibody mediated immune processes. It was the first disease to be recognized as an autoimmune disease.
Conditions of hyperthyroidism and hypothyroidism in their various forms can also contribute to development of goiter. Here we see a few of the many thyroid-pituitary interactions that can result in hyperthyoid or hypothyroidism.
Catecholamines – various hormones that are released by the adrenal glands (and other sites) in response to stress. They are part of the sympathetic nervous system.
These hormones are collectively referred to as catecholamines because they contain a catechol group, and are derived from the amino acid tyrosine.
The two primary forms we know are:
Epinephrine (E) [be careful in using this abbreviation because it is also used for estrogen]
Norepinephrine (NE)
However, the neurotransmitter dopamine is also a catecholamine:
Dopamine (DA) - dopamine oxidation is suspected as being responsible for symptoms of schizophrenia and may be involved in producing Parkinsonism.
(a) (b)
• Cortex
Kidney
• Medulla
Adrenal gland
CapsuleZona
glomerulosa
Zonafasciculata
Zonareticularis
Adrenalmedulla
Short term More prolongedStress
Hypothalamus
Nerve impulses
Adrenalcortex
CRH (corticotropin-releasing hormone)
Corticotrophcells ofanteriorpituitary
To target in blood
ACTH
Mineralocorticoids Glucocorticoids
1. Retention of sodium and water by kidneys2. Increased blood volume and blood pressure
1. Proteins and fats converted to glucose or broken down for energy2. Increased blood glucose3. Suppression of immune system
Long-term stress response
Short-termstress response
Spinal cord
Adrenalmedulla
Preganglionicsympatheticfibers
Catecholamines(epinephrineand norepinephrine)
1. Increased heart rate2. Increased blood pressure3. Liver converts glycogen to glucose and releases glucose to blood4. Dilation of bronchioles5. Changes in blood flow patterns leading to decreased digestive system activity and reduced urine output6. Increased metabolic rate
Adrenergic – having or pertaining to adrenalin (E) or (NE)
Cholinergic – having or pertaining to acetylcholine (the most common neurotransmitter)
Exogenous substances that stimulate cholinergic receptors include nicotine and muscarine (these substances are called cholinomimetic agents)
Muscarine is a chemical compound found in some mushrooms, particularly a number of inocybe and clitocybe species. It is known to be toxic.
Taxi Driver in India visiting the Coffee Shop He is stimulating his nicotinic receptors via the hookah.
13.4 Cortisol secretion and depression (Part 2)
Dexamethasone is a potent synthetic member of the glucocorticoid class of steroid hormones. It acts as an anti-inflammatory and immunosuppressant. Its potency is about 20-30 times that of hydrocortisone and 4-5 times of prednisone.
13.6 Phototherapy may ameliorate seasonal affective disorder (SAD)
Individuals with SAD received therapies on AM and PM intervals.
13.8 Light exposure affects both onset time and level of melatonin secretion (Part 1)
N = normal subjects… melatonin secretion occurs earlier
SAD individuals and melatonin secretion occurs later prior to treatment and becomes similar to N after treatment
13.8 Light exposure affects both onset time and level of melatonin secretion (Part 2)
Higher melatonin levels are associated with less light exposure (open circles)