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Glossary of Physiology Terms
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There are 9 glossary search results for:   Primary




Definition:
Primary hypothyroidism is characterized by abnormally low levels of thyroid hormone (T3 and T4) production, where the defect is at the level of the thyroid gland itself.

In primary hypothyroidism, the circulating levels of the thyroid hormones are low, however, the levels of the thyroid stimulating hormone (TSH) are high due a lack of thyroid hormone negative feedback on the anterior pituitary.

Common causes of primary hypothyroidism include iodine deficiency (which leads to goiter), and Hashimoto's disease, in which autoimmune antibodies destroy the ability of the thyroid gland to produce the thyroid hormones.

Related glossary terms/phrases:
Hypothyroidism
Secondary hypothyroidism
Tertiary hypothyroidism



Abbreviation:
ACh

Definition:
Acetylcholine (ACh) is a chemical neurotransmitter used by the central nervous system (CNS) as well as the peripheral nervous system (PNS). Acetylcholine is a classical neurotransmitter and, in fact, it was the first of the classic neurotransmitters to be discovered. It was discovered in 1914 by Henry Hallett Dale while conducting experiments on the heart.

Acetylcholine is the neurotransmitter used by the somatic division of the nervous system at the neuromuscular junction (where a somatic motor neuron makes synaptic contact with a skeletal muscle cell). Acetylcholine is also used extensively by both branches of the autonomic nervous system; sympathetic and parasympathetic. It is the primary neurotransmitter released in autonomic ganglia by preganglionic autonomic neurons. It is also the primary neurotransmitter released by parasympathetic postganglionic neurons. A few sympathetic postganglionic neurons also release acetylcholine. The diverse actions of acetylcholine are exerted via the activation of nicotinic and muscarinic ACh receptors.

Other resources:
Acetylcholine (Wikipedia)



Definition:
Electrogenic pumps are primary active transporters that hydrolyze ATP and use the energy released from ATP hydrolysis to transport ions across biological membranes leading to the translocation of net charge across the membrane.

For example, the Na+/K+ ATPase (sodium pump) is an electrogenic pump because during every transport cycle, it transports 3 Na+ ions out of the cell and 2 K+ ions into the cell. This leads to the movement of one net positive charge out of the cell making this process electrogenic.

Related glossary terms/phrases:
Electrogenic



Definition:
Protrusion or bulging of one or both eyeballs out of the orbit. It may be caused by swelling of orbital tissue in response to trauma, or by hyperthyroidism (especially primary hyperthyroidism).

It is also referred to as exophthalmus, exophthalmia, proptosis, or exorbitism.

Other resources:
Exophthalmos (Wikipedia)



Definition:
A type of primary hypothyroidism, Hashimoto's disease is an autoimmune disorder, in which anti-thyroid antibodies destroy the ability of the thyroid gland to produce the thyroid hormones. Antibodies against thyroid peroxidase (TPO) and thyroglobulin (Tg) are often seen in this disorder.

Hashimoto's disease is also known as Hashimoto's thyroiditis.

Related glossary terms/phrases:
Hypothyroidism
Primary hypothyroidism



Definition:
Hyperthyroidism refers to a pathophysiological condition in which the thyroid gland produces and releases abnormally high levels of the thyroid hormones (T3 and T4).

The symptoms of hyperthyroidism may include high metabolic rate, weight loss, nervousness, excess heat production, tachycardia, and tremor.

Two main forms of hyperthyroidism exist: (1) Primary hyperthyroidism, and (2) Secondary hyperthyroidism.

In primary hyperthyroidism, the thyroid gland produces high levels of the thyroid hormones, either as a result of a secretory tumor of the thyroid gland, or under the control of thyroid stimulating immunoglobulins (such as in Graves' disease).

Secondary hypothyroidism is caused by high levels of thyroid stimulating hormone (TSH) produced by the anterior pituitary gland. TSH then stimulates the thyroid gland to produce excessive amounts of the thyroid hormones.

Related glossary terms/phrases:
Hypothyroidism
Euthyroidism



Definition:
Hypothyroidism refers to a pathophysiological condition in which the thyroid gland does not produce sufficient amounts of the thyroid hormones (underactive thyroid), leading to abnormally low levels of the thyroid hormones (T3 and T4).

The symptoms of hypothyroidism may include reduced metabolic rate, chronic fatigue, weight gain, myxedema, and depression.

Three main forms of hypothyroidism exist: (1) Primary hypothyroidism, (2) Secondary hypothyroidism, and (3) Tertiary hypothyroidism.

In primary hypothyroidism, the thyroid gland itself is incapable of producing normal levels of the thyroid hormones.

Secondary hypothyroidism is caused by low levels of thyroid stimulating hormone (TSH). TSH, produced by the anterior pituitary gland, is required to stimulate the thyroid gland to produce the thyroid hormones.

Tertiary hypothyroidism is caused by low levels of thyrotropin releasing hormone (TRH). TRH, produced by the hypothalamus, is required to stimulate the anterior pituitary gland to produce TSH which, in turn, is required to stimulate the thyroid gland to produce the thyroid hormones.

Related glossary terms/phrases:
Primary hypothyroidism
Secondary hypothyroidism
Tertiary hypothyroidism

Hyperthyroidism
Euthyroidism



Definition:
A condition associated with hypothyroidism (especially primary hypothyroidism) in adults. It is characterized by thick, course skin, skin swelling (edema), and decreased metabolic rate and mental activity.



Definition:
Secondary active transport is a type of active transport across a biological membrane in which a transport protein couples the movement of an ion (typically Na+ or H+) down its electrochemical gradient to the movement of another ion or molecule against a concentration or electrochemical gradient. The ion moving down its electrochemical gradient is referred to as the driving ion. The ion/molecule being transported against a chemical or electrochemical gradient is referred to as the driven ion/molecule.

This transport process is referred to as active transport because the driven ion/molecule is transported against a concentration or electrochemical gradient. It is referred to as secondary active transport because no ATP hydrolysis is involved in this process (as opposed to primary active transport). The energy required to drive transport resides in the transmembrane electrochemical gradient of the driving ion.

Secondary active transport is also referred to as ion-coupled transport. Those utilizing Na+ as the driving ion are called Na+-coupled transporters. Those utilizing H+ as the driving ion are called H+-coupled transporters.

Two types of secondary active transport exist: cotransport (also known as symport) and exchange (also known as antiport). Na+/glucose cotransporter and H+/dipeptide cotransporter are examples of cotransporters. Na+/Ca2+ exchanger and Na+/H+ exchanger are examples of exchangers.

Related glossary terms/phrases:
Cotransport
Symport
Exchange
Antiport

See also:
Lecture notes on Secondary Active Transport









Posted: Sunday, March 31, 2013
Last updated: Friday, August 28, 2015