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By the end of this section, you will be able to:
  • List the classes of pharmaceuticals that interact with the autonomic nervous system
  • Differentiate between cholinergic and adrenergic compounds
  • Differentiate between sympathomimetic and sympatholytic drugs
  • Relate the consequences of nicotine abuse with respect to autonomic control of the cardiovascular system

An important way to understand the effects of native neurochemicals in the autonomic system is in considering the effects of pharmaceutical drugs. This can be considered in terms of how drugs change autonomic function. These effects will primarily be based on how drugs act at the receptors of the autonomic system neurochemistry. The signaling molecules of the nervous system interact with proteins in the cell membranes of various target cells. In fact, no effect can be attributed to just the signaling molecules themselves without considering the receptors. A chemical that the body produces to interact with those receptors is called an endogenous chemical    , whereas a chemical introduced to the system from outside is an exogenous chemical    . Exogenous chemicals may be of a natural origin, such as a plant extract, or they may be synthetically produced in a pharmaceutical laboratory.

Broad autonomic effects

One important drug that affects the autonomic system broadly is not a pharmaceutical therapeutic agent associated with the system. This drug is nicotine. The effects of nicotine on the autonomic nervous system are important in considering the role smoking can play in health.

All ganglionic neurons of the autonomic system, in both sympathetic and parasympathetic ganglia, are activated by ACh released from preganglionic fibers. The ACh receptors on these neurons are of the nicotinic type, meaning that they are ligand-gated ion channels. When the neurotransmitter released from the preganglionic fiber binds to the receptor protein, a channel opens to allow positive ions to cross the cell membrane. The result is depolarization of the ganglia. Nicotine acts as an ACh analog at these synapses, so when someone takes in the drug, it binds to these ACh receptors and activates the ganglionic neurons, causing them to depolarize.

Ganglia of both divisions are activated equally by the drug. For many target organs in the body, this results in no net change. The competing inputs to the system cancel each other out and nothing significant happens. For example, the sympathetic system will cause sphincters in the digestive tract to contract, limiting digestive propulsion, but the parasympathetic system will cause the contraction of other muscles in the digestive tract, which will try to push the contents of the digestive system along. The end result is that the food does not really move along and the digestive system has not appreciably changed.

The system in which this can be problematic is in the cardiovascular system, which is why smoking is a risk factor for cardiovascular disease. First, there is no significant parasympathetic regulation of blood pressure. Only a limited number of blood vessels are affected by parasympathetic input, so nicotine will preferentially cause the vascular tone to become more sympathetic, which means blood pressure will be increased. Second, the autonomic control of the heart is special. Unlike skeletal or smooth muscles, cardiac muscle is intrinsically active, meaning that it generates its own action potentials. The autonomic system does not cause the heart to beat, it just speeds it up (sympathetic) or slows it down (parasympathetic). The mechanisms for this are not mutually exclusive, so the heart receives conflicting signals, and the rhythm of the heart can be affected ( [link] ).

Questions & Answers

list down all the hormones secreted by adrenal gland
Odong Reply
The amount of blood pumped by the left ventricle of the heart in one contraction.
Javid Reply
how we can calculate the cardiac output
khater
and how do we calculate the strock valume
khater
stroke volume is not all the blood contained in the left ventricle; normally, only about two-thirds of the blood in the ventricle is expelled with each beat.
Javid
Cardiac output 5.5 l S. V 68.75 ml H. R 80bpm
Javid
If we consider SV 70, end systolic vol is about 15% of total(approx always) out of a total of 80-85 ml only 70ml is pumped per systole
Kartik
what is macrophages?and its function
Sajjad Reply
macrophages they are white blood cells that engulf dead cells in the body
patience
what is power stroke?
muravha
no idea
patience
what is the stroke volume of heart?
up
If an autoimmune disorder targets the alpha cells, production of which hormone would be directly affected?
Samantha Reply
what is a muscle?
Gideon Reply
A band or bundle of fibrous tissue in a human or animal body that has the ability to contract, producing movement in or maintaining the position of parts of the body
Mody
ok
Gideon
what's endolphthamities and panophthalmities?
Gideon
fluid around the brain
louise Reply
what ?
Asif
cerebro spinal fluid
Bhupender
The brain and spinal cord are surrounded by a clear fluid called cerebrospinal fluid (CSF). This fluid is produced and stored in cavities in the brain called ventricles. It circulatesaround the brain, moving from ventricle to ventricle. ... Hydrocephalus is a condition in which there is too much CSF
Archie
what is hydrocphalus
aminul Reply
Google krlena na madarchod yha maa chudwa rha ha sabko notification bhjke
Bhupender
when cerebrospinal fluid produce în the brain, i.e. brain ventricles, is to abundent in the brain and is not trăind out of the brain. as a consequence this lichid pute mechanical pressure oñ the brain and it pushes the cerebrum tissue. as a consequence this pressure on the neuronscan cause neurologi
Centerkinet
cal disfunctions, for example clinical headache
Centerkinet
. It is posible to drainout the fluid through a device dalles shunt,as i remember.
Centerkinet
but where are also home medicinsfor decreasing the production of cerebrospin.fluid etc
Centerkinet
there are some medicines that can decrease the production of csf
Centerkinet
a neurologist advice is needed
Centerkinet
i wrote some medicines NOT home medicines. it is a serious condition and specialized medical advice is needed. of course also general medical knowledge may be helpful, but not enough, a specialist is neede
Centerkinet
if anyone help me in physiology
Radika Reply
i am BSN student of first year which book is best for physiology
Radika
i am BSN student of first year which book is best for physiology
Radika
ross and wilson anotomy and physiology
Sajjad
it's 1 book for anotomy and physiology it's best for bs nursing
Sajjad
yes Ross and wilson physiology is better for study
Nasir
I'm also the student of bs nursing
Sajjad
I study guiton and hall &ganong
Gentle
I'm also midwif help me be the best book for midwif
nimco
what ia the function of indocrine system
sheraz
salam all friend
sheraz
help me with this question; explain at least five emergency acute pain found in fundamental emergency medicine
Christon
Fascial compartment of forearm
Hidayatullah
what's a tissue?
Mwape Reply
a group of cells with the same function
Dee
tissue is a group of cells that perform the same functions.
Rashid
explain a bit about a tissue
Mwape
A tissue is made up of cells that are similar in shape and perform the same function, for instance brain cells form up a brain tissue. Whereas a group of tissues that perform the same function form an organ... so in this case the brain which is the organ is formed as a result of brain tissues.
Isaac
what is gross anatomy
Joseph
the branch of anatomy that deals with the structure of organs and tissues that are visible to the naked eye.
Archie
1.To know how the structures functions. 2.To easily identify the micro structures and the macro structures. 3.To be able to explain that anatomy is the study of the structures and physiology is the study of how the structures functions
Abban Reply
Describe the two classes of hormones (3 with subclasses) and how they affect their target cells.
Shalaeha Reply
what is control centre
Gohil Reply
Angie The larger air passage of the lung is
Angie Reply
guys help to make me understand the structure of the skin
Olokojo Reply
the skin has three layers epidermis,dermis,and subcutaneous tissue
Antony
guys what is esrf
Antony
End Stage of Renal Failure
sheraz
what's the meaning of OPD
Sintung
Out Patient Department
Shahab
the skin has the assesory structures.that is, sebaceous glands, sweat glands, hairs, nails,blood vessels and lymph vessels.
Mutebe
yh
Gideon
define cell and give it's brief description of the orgenelles
Manish Reply
a cell is a basic unit of life
emmanuella
what about philosophy
Smart
the organelle is a membrane bound structure in the cell that performs a particular function
emmanuella
Cell.Is a basic functional unit of life. it has the organelles, Golgi apparatus, smooth endoplasmic membrane, rough endoplasmic reticular,Lysosomes, mitochondrial and others.
Mutebe

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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