Accelerans nerve forms a part of the sympathetic branch of the

autonomic nervous system The autonomic nervous system (ANS), sometimes called the visceral nervous system and formerly the vegetative nervous system, is a division of the nervous system that operates viscera, internal organs, smooth muscle and glands. The autonomic nervo ...

, and its function is to release noradrenaline at its endings on the heart. The heart beats according to a rhythm set up by the sinus-atrial node or pacemaker, which is located on the right atrium of the heart. It is acted on by the

nervous system In biology, the nervous system is the complex system, highly complex part of an animal that coordinates its behavior, actions and sense, sensory information by transmitting action potential, signals to and from different parts of its body. Th ...

, as well as

hormones A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs or tissues by complex biological processes to regulate physiology and behavior. Hormones a ...

in the

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood is com ...

, and venous return: the amount of blood being returned to the heart. The two nerves acting on the heart are the

vagus nerve The vagus nerve, also known as the tenth cranial nerve (CN X), plays a crucial role in the autonomic nervous system, which is responsible for regulating involuntary functions within the human body. This nerve carries both sensory and motor fibe ...

, which slows heart rate down by emitting

acetylcholine Acetylcholine (ACh) is an organic compound that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Par ...

, and the accelerans nerve which speeds it up by emitting noradrenaline. This results in an increased

blood flow Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamics, dynamics of blood flow. The circulatory system is controlled by homeostasis, homeostatic mechanisms of autoregulation, just as hydrau ...

, preparing the body for a sudden increase in activity.In Search of Memory: The Emergence of a New Science of Mind - Eric R. Kandel Google Books
/ref> These nerve fibres are part of the

, part of the 'fight or flight' system. Right where the sinus-atrial node is, the negative charge of the interior of the fibres of heart muscles breaks down spontaneously the cells in the pacemaker about 70 minutes each time. As a result of this, a small current sweeps over the atria, which then reaches the insulating connective tissue between the atria and ventricles. When the current reaches this part, the atrio-ventricular node picks it up, thus creating the rhythm of the heartbeats through the rate and strength of each palpitation which is controlled by the accelerans nerve.

History and etymology

The accelerans nerve was first discovered on April 23, 1883 by German medical students L.C. Wooldridge, D.S and George Henry Lewes, M.B. Both medical students conducted their investigation in th
Physiological Institute of Leipzig
The purpose of the investigation which yielded the finding of the accelerans nerve was to learn more about the function of the

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons). Nerves have historically been considered the basic units of the peripheral nervous system. A nerve provides a common pathway for the Electrochemistry, electrochemical nerv ...

s which can be observed in the surface of the ventricles of

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

ian hearts. In their findings, both researches saw that there was an increase in cardiovascular acceleration due to stimulation of the accelerans nerve found in the ventricles of the mammals they studied. In Aug 1950, medical researcher O. Krayer confirmed that through electrical stimulations of the accelerans nerve, the force of heart palpitations could be increased which increases

throughout the body, rightly solidifying the importance of this nerve as well as what its manipulation could lead to. More recently, on 24 Feb 2000, the

New England Journal of Medicine ''The New England Journal of Medicine'' (''NEJM'') is a weekly medical journal published by the Massachusetts Medical Society. Founded in 1812, the journal is among the most prestigious peer-reviewed medical journals. Its 2023 impact factor was ...

released a study which revealed the existence of a mutant gene that leads to the development of a transporter that is in charge of the reuptake of noradrenaline back to the accelerans nerve. The term accelerans comes from the latin word ''accelerrō'' which means "quickening" or "to hasten". The term

comes from the latin words ''nervus'' which meant sinew or

tendon A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...

in an animal body.

Measurements in mammals

The majority of research regarding the accelerans nerve has been centered around other mammals part from humans. The first study ever conducted on accelerans nerve on April 23, 1883 necessitated other mammals apart from humans, not only due to ethical concerns, but in order to visualize the difference in their stimulation depending on the mammal. The following is a list of mammals who have been used for research into the accelerans nerve and what results were found from the studies:

Dogs

In the case of dogs, the first case ever mentioned regarding the accelerans nerve and its function in 1883 yielded that the investigation in dogs was done almost exclusively on the right side of the nerves. The reason for this was that researches saw that any sort of stimulation on the left side showed no significant impact to the rhythm of the heart. Also, the researchers observed that even after death, any manipulation of the accelerans nerve, or any other neighbouring nerves, caused a reflex movement from the dogs, underlying the significance of its function in the heart. Furthermore, one study conducted in January 1988 found that even through chronic administration of betaxolol (1 mg kg-1 daily, s.c.) for 7 days, which is a drug used to relax blood vessels and slowing down heart rate,

in vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, an ...

stimulation of the accelerans nerve demonstrated a significant increase in the production of noradrenaline. These results indicated that in medical situations in which the rate and strength of a patient's heartbeats reaches critically low levels, stimulation of the accelerans nerve allows for a more expeditious way to gain the heart's vitality back, analogous to the function of artificial pacemakers.

Cats

In the case of cats, stimulation of the accelerans nerve was found to produce a much more significant effect on their heart rates compared to the hormones secreted by the adrenals glands in the autonomic-nervous system for the fight-or-flight response. Moreover, the vigorous heart palpitations induced by the accelerans nerve in the hearts of cats seem to disappear quickly after a low-frequency stimulation is applied to the nerves. This quick shift in the heart rate resulted in the idea that decreases of stroke volume in humans requires direct

vagal The vagus nerve, also known as the tenth cranial nerve (CN X), plays a crucial role in the autonomic nervous system, which is responsible for regulating involuntary functions within the human body. This nerve carries both sensory and motor fibe ...

control of the heart ventricles.

Rabbit

In the case of rabbits, a study conducted in December 1973 directly administered certain substances to slow down the heart rate ranging from

fentanyl Fentanyl is a highly potent synthetic piperidine opioid primarily used as an analgesic (pain medication). It is 30 to 50 times more Potency (pharmacology), potent than heroin and 50 to 100 times more potent than morphine. Its primary Medici ...

morphine Morphine, formerly also called morphia, is an opiate that is found naturally in opium, a dark brown resin produced by drying the latex of opium poppies (''Papaver somniferum''). It is mainly used as an analgesic (pain medication). There are ...

(at concentrations of 10-100μM) in order to observe the heart's natural secretion of noradrenaline in the case of critically low heart rates. Every single drug given to the rabbits, except for naloxone, led to a diminished amount of

neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

al uptake of noradrenaline. However, researchers observed that all the substances administered directly into the rabbits' hearts led to an increase in the secretion of noradrenaline due to the stimulation of the accelerans nerve by 5

hertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in ter ...

. In another case, it was observed that acidic substances, specifically

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main compone ...

, when exposed to the accelerans nerve in rabbit hearts led to an increase in

blood pressure Blood pressure (BP) is the pressure of Circulatory system, circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term ...

due to the nerve's reaction with the acid which made it send out stronger signals.

References