Glossary of Physiology Terms
There are
72 glossary search results for:
All or non law
Definition:
All-or-nothing is usually used when describing the
action potential. It refers to the well-known observation that an action potential always occurs in its full size (i.e., full magnitude of voltage change).
Many physiologists use
all-or-nothing and
all-or-none interchangeably.
See also:
Important Features of the Neuronal Action Potential
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:
An agonist is a molecule that binds to a receptor and activates a physiological response similar to that induced by the naturally occurring physiological ligand of the receptor. Therefore, agonist binding to a receptor mimics the action of the natural ligand.
For example, acetylcholine (ACh) is the naturally occurring physiological ligand that activates nicotinic and muscarinic acetylcholine receptors. Nicotine is an agonist of nicotinic ACh receptors (nAChR), and muscarine is an agonist of muscarinic ACh receptors (mAChR).
Related glossary terms/phrases:
Antagonist
Definition:
Absence of menstruation in sexually mature female individuals.
Definition:
An antagonist is a molecule that binds to a receptor, however, it does not activate the physiological response induced by the naturally occurring physiological ligand of the receptor. Moreover, once bound to the receptor, an antagonist prevents the physiological ligand from activating the receptor. Therefore, antagonist binding to a receptor prevents or blocks the action of the natural ligand.
For example, acetylcholine (ACh) is the naturally occurring physiological ligand that activates nicotinic and muscarinic acetylcholine receptors. Tubocurarine and succinylcholine are antagonists of the nicotinic ACh receptor (nAChR), and atropine is an antagonist of the muscarinic ACh receptor (mAChR).
Related glossary terms/phrases:
Agonist
Definition:
The region of the neuron cell body from which the axon originates. The axon hillock is generally the site of action potential initiation. It is also referred to as the initial segment.
Definition:
Concave on both sides of a structure, usually referring to a disc or a lens.
Of particular importance to physiology is the structure of mature red blood cells (erythrocytes), which is a flattened cell that has assume a biconcave shape. It is thought that the biconcave shape of red blood cells helps with the flow property of blood through blood vessels.
Abbreviation:
CO
Definition:
Cardiac output is defined as the volume of blood pumped every minute by each (left or right) ventricle of the heart. It is generally reported in L/min or mL/min.
Cardiac output (CO) is the product of heart rate (HR) and stroke volume (SV). Thus,
CO = HR × SV
Heart rate is defined as the number of heart contractions per minute. Stroke volume is the volume of blood pumped per ventricular contraction.
For a typical resting adult human being at rest, CO is approximately 5 L/min.
CO = 70 contractions/min × 70 mL/contraction = 4,900 mL/min
Definition:
The lowest part of the female uterus facing the vaginal canal. It is cylindrical in shape and 2-3 cm long. A cervical canal runs the entire length of the cervix and connects the lumen of the vaginal canal to the lumen of the uterus. The opening of cervical canal into the uterus is called the internal os, and the opening into the vagina is called the external os.
Definition:
Refers to a conformational change of a channel protein by which the channel goes from the open state to the inactive state. The inactive state refers to a conformational state in which ions are not allowed to permeate the channel pore. Thus, with respect to ion permeability, the inactive state is similar to the close state of the channel. Ions cannot permeate the channel pore either in the closed or inactive state. However, the channel assumes very distinct and different conformations in the inactive state and closed state.
See also:
Neuronal Action Potential - Important Features of the Neuronal Action Potential
Definition:
An integral membrane protein which contains a pore through which ions, water, or polar molecules permeate. For any given channel, the pore is usually very selective for the particular ion or molecule. For example, sodium (Na
+) channels are very selective for Na
+ over other cations.
The channel pore may be constitutively open, or it may be gated to the open state by various stimuli such as chemical ligands, voltage, temperature, or mechanical stimulation of the membrane.
Definition:
Refers to the concentration gradient of an ion or molecule. The concentration gradient may exist across a biological membrane, where the concentration is higher on one side of the membrane compared to the other side. Concentration gradient may also exist in a solution without an apparent barrier separating the area of higher concentration from the area of lower concentration. In both cases, the free energy that results from the concentration difference drives the movement of the ion/molcule from the area of higher concentration to the area of lower concentration. In free solution, the ion/molecule simply diffuses down its gradient. Movement across a biological membrane is more complicated and is a function of lipid solubility of the ion/molecule as well as the presence of channels or transport proteins that can allow the ion/molecule to cross the membrane (see
Lipid Bilayer Permeability and
Summary of Membrane Transport Processes).
Related glossary terms/phrases:
Electrical gradientElectrochemical gradient
Definition:
The semi-solid, partially-digested contents of the stomach that exit via the pyloric valve to enter the
duodenum (initial region) of the small intestine.
Definition:
Specifically, thyroid colloid. Refers to the protein-rich fluid within the lumen of thyroid follicles. The major protein component of the thyroid colloid is
thyroglobulin.
Definition:
A type of
secondary active transport across a biological membrane in which a transport protein couples the movement of an ion (usually 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.
In cotransport, the direction of transport is the same for both the driving ion and driven ion/molecule (into the cell or out of the cell).
An example is the Na
+/glucose cotransporter (SGLT), which couples the movement of Na
+ into the cell down its electrochemical gradient to the movement of glucose into the cell against its concentration gradient.
Cotransport is also commonly referred to as
symport.
Transport proteins that are involved in this type of transport are referred to as cotransporters or symporters.
See:
SymportRelated glossary terms/phrases:
Secondary active transportExchangeSee also:
Lecture notes on
Secondary Active Transport
Definition:
A potent blocker of nicotinic cholinergic receptors (nicotinic acetylcholine receptor, nAChR) found at the neuromuscular junction. At small doses, curare can lead to muscle weakness. At high doses, curare can lead to paralysis of skeletal muscles, which would also result in asphyxiation (and ultimately death) due to paralysis of the diaphragm. Curare was commonly the active agent of poison arrow.
Other resources:
See Wikipedia
Definition:
The enzyme found in target tissues of the thyroid hormones that converts thyroxine (also known as tetraiodothyronine or T
4) to triiodothyronine (T
3).
Specifically, 5'-deiodinase converts T
4 to the active form of the thyroid hormone, T
3.
5-Deiodinase converts T
4 to the inactive form of the thyroid hormone, reverse T
3 (rT
3).
Definition:
The first region (i.e., most proximal region) of the small intestine.
Chyme leaving the stomach (through the pyloric valve) first enters the duodenum. The contents of the duodenum empty into the
jejunum (middle region of the small intestine). In adult humans, the duodenum is about 25-38 cm (10-15 inches) long.
Related glossary terms/phrases:
JejunumIleum
Definition:
Accumulation of fluid in the interstitial compartment, which usually leads to a visible swelling of the affected tissue.
Definition:
An electrogenic transport process is one that leads to the translocation of net charge across the membrane. For example, ion channels such as Na
+, K
+, Ca
2+, and Cl
− channels are electrogenic.
The Na
+/K
+ ATPase is electrogenic because for every ATP molecule hydrolyzed, 3 Na
+ ions are transported out of the cell and 2 K
+ ions are transported into the cell (leading to the translocation of one net positive charge out of the cell).
Many
secondary active transporters are also electrogenic. For example, the Na
+/glucose cotransporter (found in the small intestine and kidney proximal tubules), transports 2 Na
+ ions and 1 glucose molecule into the cell across the plasma membrane (leading to the translocation of two net positive charges into the cell per transport cycle).
Definition:
Electrophysiology is the study of the electrical properties of biological macromolecules, cells, tissues, and organs. Electrical signals such as voltage and/or current are generally measured. Examples include measuring changes in the membrane voltage of excitable cells (e.g., neurons, muscle cells, and some endocrine cells) during an
action potential. The current carrried by ions as they permeate the pore of ion channels can also be measured - both at the single-channel level (single-channel current), as well as the macroscopic current resulting from the activity of a population of channels. As another example, electrical measurements may involve recording voltage changes at the surface of the skin that result from the activity of skeletal muscles (electromyogram, EMG), cardiac myocytes (electrocardiogram, ECG), or neurons in the brain (electroencephalogram, EEG).
Definition:
Endocrine cells are responsible for producing and releasing
hormone molecules into the bloodstream. Endocrine cells are typically grouped together in organs referred to as
endocrine glands.
Related glossary terms/phrases:
Endocrine glandHormone
Definition:
A type of
secondary active transport across a biological membrane in which a transport protein couples the movement of an ion (usually 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.
In exchange, the driving ion and the driven ion/molecule are transported across the biological membrane in opposite directions.
An example is the Na
+/Ca
2+ exchanger (NCX), which couples the movement of 3 Na
+ ions into the cell down its electrochemical gradient to the movement of 1 Ca
2+ ion out of the cell against its electrochemical gradient.
Exchange is also commonly referred to as
antiport.
Transport proteins that are involved in this type of transport are referred to as exchangers or antiporters.
See:
AntiportRelated glossary terms/phrases:
Secondary active transportCotransportSee also:
Lecture notes on
Secondary Active Transport
Definition:
Refers to the ability of some cells to be electrically excited resulting in the generation of
action potentials. Neurons, muscle cells (skeletal, cardiac, and smooth), and some endocrine cells (e.g., insulin-releasing pancreatic
β cells) are excitable cells.
See also:
Resting Membrane Potential - Introduction
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:
Glycine (Gly, G) is one of the standard twenty (20) amino acids. At a molecular weight of 75.07 g/mol, it is the smallest of the 20 amino acids used by cells to synthesize peptides, polypeptides, and proteins.
In the nervous system, glycine is also an inhibitory amino acid neurotransmitter. Glycinergic synapses are most commonly found in brain stem and spinal cord circuits. Glycine is a classical neurotransmitter. Its action is exerted via the activation of ionotropic glycine receptors (GlyR), which are ligand-gated chloride channels. At glycinergic synapses, the action of glycine is terminated by glycine transporters (GlyT), which transport glycine from the extracellular space in synaptic and extrasynaptic regions into neurons and glia.
Definition:
Goiter is an enlargement of the thyroid gland caused most commonly by iodine deficiency in the diet. Iodine deficiency leads to low levels of thyroid hormone production, and a reduction in thyroid hormone negative feedback on the hypothalamus and the anterior pituitary leads to a compensatory rise in the thyroid stimulating hormone (TSH). Enlargement of the thyroid gland is, therefore, caused by abnormally high circulating levels of TSH, which has a strong trophic effect on the thyroid gland.
Definition:
The H zone is in the center of the
A band where there is no overlap between the thick and the thin filaments. Therefore, in the H zone, the filaments consist only of the thick filament. The H zone becomes smaller as the muscle contracts and the sarcomere shortens. The center of the H zone is at the
M line, which is also at the center of the sarcomere.
Related glossary terms/phrases:
A bandI bandM lineZ disk
Definition:
Condition in which the plasma glucose concentration is abnormally high. In general, a fasting plasma glucose concentration higher than 110 mg/dL, or a
postprandial plasma glucose concentration higher than 180 mg/dL is considered abnormally high.
Normal, fasting glucose concentrations range from 70 to 110 mg/dL.
Related glossary terms/phrases:
Hyperglycemic HypoglycemiaHypoglycemic
Definition:
An increase in the number of cells in a tissue. It is generally brought about through mitotic cell division of cells within a tissue.
It also refers to an enlargement of an organ or body part due to an
increase in the number of cells within the organ or body part.
Related glossary terms/phrases:
Hypertrophy
Definition:
Hyperthyroidism refers to a pathophysiological condition in which the thyroid gland produces and releases abnormally high levels of the thyroid hormones (T
3 and T
4).
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:
HypothyroidismEuthyroidism
Definition:
An increase in the size of a cell such as muscle. It is generally brought about through the addition of cellular components.
It also refers to an enlargement of an organ or body part due to an
increase in the size of the cells within the organ or body part.
Related glossary terms/phrases:
Hyperplasia
Definition:
Condition in which the plasma glucose concentration is abnormally low. In general, a plasma glucose concentration lower than 70 mg/dL is considered abnormally low.
Normal, fasting glucose concentrations range from 70 to 110 mg/dL.
Related glossary terms/phrases:
HypoglycemicHyperglycemiaHyperglycemic
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 (T
3 and T
4).
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 hypothyroidismSecondary hypothyroidismTertiary hypothyroidismHyperthyroidismEuthyroidism
Definition:
The last region (i.e., most distal region) of the small intestine. Ileum receives the contents of the
jejunum and, in turn, the contents of ileum leave the small intestine by emptying into the cecum. In adult humans, the ileum is about 2-4 meters (about 6.5-13 feet) long.
Related glossary terms/phrases:
DuodenumJejunum
Definition:
Not permeable. Not allowing the passage of substances. Impermeable refers to a property of a membrane or channel pore in preventing or restricting the passage of substances. For example, the lipid bilayer portion of biological membranes is highly impermeable to ions and large polar molecules.
See also
permeable.
Related glossary terms/phrases:
PermeablePermeabilityPermeantImpermeantSee also:
Lipid Bilayer Permeability
Definition:
A glycoprotein released by
parietal cells (also know as oxyntic cells) located in the fundus region of the stomach. Intrinsic factor is required for vitamin B
12 absorption in the small intestine.
Definition:
Refers to the ability of the thyroid gland to accumulate iodide (I
−) against a steep electrochemical gradient. While the iodide concentration in plasma and interstitial fluid is approximately 300 nL, iodide concentration in the cytoplasm of thyroid follicular cells, as well as the lumen of thyroid follicles can be many folds higher. The protein that enables iodide transport into the thyroid gland against an electrochemical gradient is the Na
+/iodide symporter (NIS), which is located in the basolateral membrane of thyroid follicular cells. Within the lumen of thyroid follicles, iodide is incorporated into the tyrosine residues of thyroglobulin during thyroid hormone biosynthesis, hence, allowing very high iodide concentrations in the colloid.
Definition:
The middle region of the small intestine between the
duodenum and the
ileum. The jejunum receives the contents of the duodenum and, in turn, its contents empty into the ileum. In adult humans, the jejunum is about 2.5 meters (about 8 feet) long.
Related glossary terms/phrases:
DuodenumIleum
Definition:
The tapping sounds heard through a stethoscope placed over a partially compressed peripheral artery.
For the purpose of non-invasive blood pressure measurements, the stethoscope is usually placed on the skin overlying the brachial artery just distal to an inflated pressure cuff wrapped around the upper arm. As the pressure cuff is gradually deflated, the Korotkoff sounds result from the pulsations of the blood through the partially constricted brachial artery. With each ventricular systole, blood is forced to flow through the partially constricted brachial artery, and the turbulence in blood flow leads to the generation of the Korotkoff sounds. When the pressure cuff is fully deflated, flow through the artery resumes its normal laminar flow and, at that time, the Korotkoff sounds disappear.
Definition:
Lidocaine is a local anesthetic and an antiarrhythmic drug. It is a commonly used local anesthetic for minor surgery and in dental procedures. Lidocaine is also used topically to relieve itching, burning, and pain from skin inflammations.
Lidocaine's mechanism of action is to block fast voltage-gated Na
+ channels of neurons and cardiac myocytes.
Other names used for lidocaine are xylocaine and lignocaine.
See also:
Pharmacological Inhibition of Na+ and K+ ChannelsOther resources:
Lidocaine (Wikipedia)
Definition:
The voltage difference across a cell plasma membrane.
The membrane potential is generally inside negative with respect to the outside, where the outside potential is generally set as the reference value. In electrically excitable cells, the value of the membrane potential can be positive (inside with respect to the outside) during electrical activity (i.e., during action potentials).
Related glossary terms/phrases:
Resting membrane potentialSee also:
Resting membrane potential
Definition:
A motor unit is composed of a motor neuron and all of the muscle fibers (i.e., muscle cells) it innervates.
Alternatively, a motor unit is a group of muscle fibers innervated by a single motor neuron.
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:
Neurotoxins are chemical molecules that have an adverse effect on neuron function and, thus, disrupt the normal function of the nervous system. Neurotoxins could be small molecules or peptides and can be derived from a variety of invertebrate and vertebrate animals, as well as plant species.
The following is a short list of some examples of neurotoxins:
α-Bungarotoxin: A peptide neurotoxin that inhibits the nicotinic acetylcholine receptor.
Chlorotoxin: A peptide neurotoxin that inhibits chloride channels.
α-Conotoxin: A peptide neurotoxin that inhibits the nicotinic acetylcholine receptor.
δ-Conotoxin: A peptide neurotoxin that inhibits voltage-gated sodium channels.
w-Conotoxin: A peptide neurotoxin that inhibits N-type voltage-gated calcium channels.
Picrotoxin: Inhibits GABA
A receptor chloride channels.
Tetrodotoxin: Inhibitor of neuronal voltage-gated sodium channels.
Definition:
Chemical messenger molecules released by neurons into the synaptic cleft.
Neurotransmitter molecules may be small molecules such as glutamate,
γ-aminobutyric acid (GABA), acetylcholine, dopamine, norepinephrine, serotonin (5-hydroxytryptamine), and glycine. These are referred to as classic neurotransmitters. A neuron generally releases only one type of small classic neurotransmitter.
Neurotransmitters may also be peptide molecules, such as substance P, opioids, and somatostatin. These are referred to as neuropeptides.
Gas molecules, such as nitric oxide (NO), may also act as neurotransmitters.
Definition:
Refers to an abnormally low volume of urine production. Generally, a urine production rate of less than 400 mL/day is referred to as oliguria.
Related glossary terms/phrases:
PolyuriaOther resources:
Oliguria (Wikipedia)
Abbreviation:
OAEs
Definition:
Otoacoustic emissions (OAE) are sounds that arise from the organ of Corti within the cochlea of the inner ear in response to sound stimulation. They are thought to result from vibrations of cochlear outer hair cells (OHC) in response to stimulation by sound. Otoacoustic emissions are inaudible to the human ear, but can be recorded by placing a small recording device in the external auditory meatus (ear canal).
Otoacoustic emissions have clinical diagnostic value and are measured as part of hearing exams. In the newborn, otoacoustic emissions are recorded in order to detect blockage in the middle ear cavity (e.g., as a result of fluid accumulation) or external ear canal.
Definition:
Ouabain binds to and inhibits the transport activity of the Na
+/K
+/ATPase (i.e., sodium pump).
Ouabain is plant derived and belongs to the class of drugs referred to as cardiac glycosides. Similar to other cardiac glycosides, ouabain increase heart muscle contractility. However, ouabain is used only experimentally and not in humans (as for example digoxin is for the treatment of congestive heart failure).
There is some evidence that ouabain may be produced endogenously in humans.
Related glossary terms/phrases:
VanadateOther resources:
Ouabain (Wikipedia)
Definition:
Body weight that exceeds the normal or standard weight range. The standard range is generally determined based on height and frame size.
Related glossary terms/phrases:
Body Mass IndexSee also:
Body Mass Index Calculator
Definition:
Permeable refers to a property of a membrane or channel pore in allowing substances to pass through. For example, the lipid bilayer portion of biological membranes is highly permeable to fat-soluble molecules, but is not permeable to ions and large polar molecules.
See also
impermeable.
Related glossary terms/phrases:
ImpermeablePermeabilityPermeantImpermeantSee also:
Lipid Bilayer Permeability
Definition:
Physiology is the study of how living systems function. The scope of physiological studies ranges from the subcellular level (molecules and organelles) all the way to the level of the whole organism and how organisms adapt to vastly different environmental conditions such as hot, cold, dry, humid, or high altitude.
See also:
What is Physiology?
Definition:
Plasma is the fluid portion of whole blood, which makes up about 40% to 60% of the total volume of whole blood. Plasma has a light yellow color and is generally obtained by separating the fluid portion from the blood formed elements through sedimentation or centrifugation. Plasma contains mostly water and, in addition, minerals, nutrients, proteins, hormones, and gases (oxygen and carbon dioxide). Unlike serum, in which fibrinogen and other clotting factors have been removed by coagulation, fibrinogen and other clotting factors remain present in plasma.
Plasma is one the main fluid compartments of the human body, making up nearly 10% of the total volume of body fluids. Plasma makes up the intravascular fluid compartment; itself a subcompartment of the extracellular fluid compartment.
Definition:
Refers to an abnormally large volume of urine production. Generally, a urine production rate of higher than 2.5 L/day is referred to as polyuria.
Related glossary terms/phrases:
OliguriaHypouresisOther resources:
Polyuria (Wikipedia)
Definition:
Primary hypothyroidism is characterized by abnormally low levels of thyroid hormone (T
3 and T
4) 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:
HypothyroidismSecondary hypothyroidismTertiary hypothyroidism
Definition:
Pulse pressure is defined as the arithmetic difference between the systolic pressure (the highest blood pressure) and the diastolic pressure (the lowest blood pressure) recorded at any point along the vascular bed. Therefore:
Pulse pressure = Systolic pressure - Diastolic pressure
Pulse pressure values can be reported at any point along the vasculature starting from the left ventricle and aorta all the way to the vena cava and the right atrium. As with systolic and diastolic pressure values, pulse pressure is typically reported in mm Hg (millimeters of mercury). A typical arterial pulse pressure is 40 mm Hg (120 - 80 = 40 mm Hg). This value decreases as one proceeds along the vascular bed from arteries to arterioles, capillaries, venules, and veins. The most significant drop occurs along the arterioles.
See also:
Mean Arterial Pressure Calculator
Definition:
Surgical removal of the fallopian tube.
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
+/Ca
2+ exchanger and Na
+/H
+ exchanger are examples of exchangers.
Related glossary terms/phrases:
CotransportSymportExchangeAntiportSee also:
Lecture notes on
Secondary Active Transport
Definition:
Secondary hypothyroidism is characterized by abnormally low levels of thyroid hormone (T
3 and T
4) production, where the defect is at the level of the anterior pituitary gland.
In secondary hypothyroidism, the anterior pituitary gland is unable to produce sufficient levels of the thyroid stimulating hormone (TSH) which, in turn, leads to insufficient stimulation of the thyroid gland to produce the thyroid hormones (T
3 and T
4).
Thus, in secondary hypothyroidism, the circulating levels of both TSH and the thyroid hormones (T
3, and T
4) are abnormally low
Related glossary terms/phrases:
HypothyroidismPrimary hypothyroidismTertiary hypothyroidism
Definition:
Secretion refers to cellular release of substances (ions and small and large molecules) to the external environment of the cell. Secretion may be accomplished by exocytosis (fusion of transport vesicles with the plasma membrane and release of vesicle contents to the external environment), by transport of molecules across the plasma membrane (via the activity of transport proteins such as pumps, transporters, and channels), or by simple diffusion of fat-soluble molecules through the plasma membrane out of the cell.
For example, endocrine cells secrete
hormone molecules that then enter the bloodstream. Neurons release (i.e., secrete)
neurotransmitter molecules into the synaptic cleft. Some neurons secrete
neurohormones; which similar to hormones, travel in the bloodstream to reach distant target cells. Epithelial cells secrete molecules in luminal spaces, such as digestive enzymes secreted into the digestive tract by various cell types.
See also:
Excretion
Definition:
A rectangular signal waveform used in physiological studies to perturb (i.e., challenge) the system under study. The response of the system to the pulse is then studied carefully to learn about how the system responds to challenges.
Examples include pulses of voltage or current in electrophysiological experiments. Other examples include pulses of light, pressure, temperature, ligand, etc.
A square-wave pulse is defined by the amplitude and duration of the pulse, as well as by the frequency at which the pulse is applied to the system under study.
See also:
Neuronal Action Potential - IntroductionOther resources:
Square wave (Wikipedia)
Definition:
Tertiary hypothyroidism is characterized by abnormally low levels of thyroid hormone (T
3 and T
4) production, where the defect is at the level of the hypothalamus.
In tertiary hypothyroidism, the hypothalamus is unable to produce sufficient levels of thyrotropin release hormone (TRH). Low TRH levels lead to low production of the thyroid stimulating hormone (TSH) by the anterior pituitary gland which, in turn, leads to insufficient stimulation of the thyroid gland to produce the thyroid hormones (T
3 and T
4).
Thus, in tertiary hypothyroidism, the circulating levels of TRH, TSH, T
3, and T
4 are all abnormally low.
Related glossary terms/phrases:
HypothyroidismPrimary hypothyroidismSecondary hypothyroidism
Definition:
Removal of approximately a pint of blood in a manner similar to that for donating blood. The procedure is generally used as a simple measure to reduce the number of circulating red blood cells (e.g., to treat polycythemia) or to reduce the amount of circulating iron (e.g., to treat hemochromatosis). The procedure may be repeated as needed.
It falls under procedures referred to as phlebotomy (removing blood for therapeutic or diagnostic purposes) or bloodletting (removing blood for therapeutic purposes).
Definition:
Dry mouth. Dryness in the mouth resulting from abnormally low levels of saliva production.
Posted: Sunday, March 31, 2013
Last updated: Friday, August 28, 2015