<< Chapter < Page Chapter >> Page >

Autonomic connections to heart and blood vessels

This figure shows the spinal cord and the different nerves that connect to the heart, which is the target organ shown on the right.
The nicotinic receptor is found on all autonomic ganglia, but the cardiovascular connections are particular, and do not conform to the usual competitive projections that would just cancel each other out when stimulated by nicotine. The opposing signals to the heart would both depolarize and hyperpolarize the heart cells that establish the rhythm of the heartbeat, likely causing arrhythmia. Only the sympathetic system governs systemic blood pressure so nicotine would cause an increase.

Sympathetic effect

The neurochemistry of the sympathetic system is based on the adrenergic system. Norepinephrine and epinephrine influence target effectors by binding to the α-adrenergic or β-adrenergic receptors. Drugs that affect the sympathetic system affect these chemical systems. The drugs can be classified by whether they enhance the functions of the sympathetic system or interrupt those functions. A drug that enhances adrenergic function is known as a sympathomimetic drug    , whereas a drug that interrupts adrenergic function is a sympatholytic drug    .

Sympathomimetic drugs

When the sympathetic system is not functioning correctly or the body is in a state of homeostatic imbalance, these drugs act at postganglionic terminals and synapses in the sympathetic efferent pathway. These drugs either bind to particular adrenergic receptors and mimic norepinephrine at the synapses between sympathetic postganglionic fibers and their targets, or they increase the production and release of norepinephrine from postganglionic fibers. Also, to increase the effectiveness of adrenergic chemicals released from the fibers, some of these drugs may block the removal or reuptake of the neurotransmitter from the synapse.

A common sympathomimetic drug is phenylephrine, which is a common component of decongestants. It can also be used to dilate the pupil and to raise blood pressure. Phenylephrine is known as an α 1 -adrenergic agonist    , meaning that it binds to a specific adrenergic receptor, stimulating a response. In this role, phenylephrine will bind to the adrenergic receptors in bronchioles of the lungs and cause them to dilate. By opening these structures, accumulated mucus can be cleared out of the lower respiratory tract. Phenylephrine is often paired with other pharmaceuticals, such as analgesics, as in the “sinus” version of many over-the-counter drugs, such as Tylenol Sinus ® or Excedrin Sinus ® , or in expectorants for chest congestion such as in Robitussin CF ® .

A related molecule, called pseudoephedrine, was much more commonly used in these applications than was phenylephrine, until the molecule became useful in the illicit production of amphetamines. Phenylephrine is not as effective as a drug because it can be partially broken down in the digestive tract before it is ever absorbed. Like the adrenergic agents, phenylephrine is effective in dilating the pupil, known as mydriasis    ( [link] ). Phenylephrine is used during an eye exam in an ophthalmologist’s or optometrist’s office for this purpose. It can also be used to increase blood pressure in situations in which cardiac function is compromised, such as under anesthesia or during septic shock.

Questions & Answers

what's is reganal anatomy
Sose Reply
it is the study of interrelationships between different organs in a certain region of the body e.g abdomen
Taurai
this helps understand how these different organs work together to serve a particular body region
Taurai
hesi Tau
Precious
what is important of anatomy
Musah Reply
it's very important in any field of study or work the nurse who know anatomy well he will do good job
Abdelaziz
Can u please tell me how can I get Vanders mcqs bank
haseeb Reply
Is it possible to code a gene from two different species to come up with a specific trait?
Purityhalo
tissue,organ, system, cell
Amadi Reply
list carpal bones from proximal to distal
Meshack Reply
scaphoid, lunate, triquetrum, pisiform, trepizium, trepizoid, capitate, hamate
Bhuvana
You are right
David
gr8 bro
Daniel
anyone explain lungs valium?
Sajid
when did the roman rule Britain
Rita Reply
what is function of the male respiratory system ?
poonam Reply
need to join this conversation
Collins
It's the same as the female respiratory system. Did you mean reproductive system. If you didn't, its for breathing.
Grace
what does increased glomerular filtration results from
Nancy Reply
what is the difference between cardiovascular and respiratory system
Bokenana Reply
cardiovascular deals with blood,blood vessels and heart while respiratory system deal with gas exchange
Erick
send me your app line
Erick
just make a class group and have online classes take turns in teaching
maz
send yo app lines so I make a group
Erick
ok
Erick
you're simply saying no to teaching one another
maz
what's an epithelial tissue
Romantic Reply
epithelial tissue are thin tissues that covers all the exposed surfaces of the body
Ireen
is anyone from high school?
Sahil
yes
Sulaiman
Final year
Royleen
med student
brian
South Africa
brian
final year too
brian
INDIA
Sahil
describe the structure of the human body in terms of six levels of organisation
Chulufya Reply
list the muscles of abdomen and their functions
HANNAH Reply
list the neck muscles and their functions
HANNAH
list the thy muscles and their functions
HANNAH
four muscles in facial expression
nah
internal obliques external obliques
Diana
describe flow of blood
osoma Reply
are arteries do pumping action to get are blood flow
isaiah
causes of occasional female muscle weakness and body pain
sammy
hey Venus ulcers description
patrick
what is conduction in the heart occur
Daud Reply
what is anatomy
Prin Reply
anatomy is the study of human body.?
Sittie
anatomy is the study of scientific human body's structure.
Sittie
Anatomy is the study of the structure of the human body and the physical relationship between its constituent parts.
Maina
Anatomy is the study of the structures of body parts
Nepi
what are the principles of public health nursing?
tribel
Anatomy is the scientific study of human body parts .
Shakinah
Anatomy is the study of structure and relationship of the body structure
Stephen
Anatomy is the study of the structure and movement of the human body
renukha
energy generation molecular transport reproduction.
Sarah
Anatomy is the study of budy structures and their relationship.
Denis
Anatomy is the scientific study of human structure
jacinta
Anatomy ie the study of the human body and its functions.
Samuel
anatomy is the study of human body
Nadiiro
is the study of the structure of the body
Nqobile
I thank you guys for your studying.
Gibson
what is the biological meaning of come?
Gibson
anatomy is the study of human structure.
Diana
I need help!!! what are toxic wastes being removed from human urinary system apart from urine?
DAVINA
urea, amonia
Orsine

Get the best Anatomy & Physiology course in your pocket!





Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Anatomy & Physiology' conversation and receive update notifications?

Ask