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Mydriasis

This photograph shows a person’s eye with a relatively large pupil.
The sympathetic system causes pupillary dilation when norepinephrine binds to an adrenergic receptor in the radial fibers of the iris smooth muscle. Phenylephrine mimics this action by binding to the same receptor when drops are applied onto the surface of the eye in a doctor’s office. (credit: Corey Theiss)

Other drugs that enhance adrenergic function are not associated with therapeutic uses, but affect the functions of the sympathetic system in a similar fashion. Cocaine primarily interferes with the uptake of dopamine at the synapse and can also increase adrenergic function. Caffeine is an antagonist to a different neurotransmitter receptor, called the adenosine receptor. Adenosine will suppress adrenergic activity, specifically the release of norepinephrine at synapses, so caffeine indirectly increases adrenergic activity. There is some evidence that caffeine can aid in the therapeutic use of drugs, perhaps by potentiating (increasing) sympathetic function, as is suggested by the inclusion of caffeine in over-the-counter analgesics such as Excedrin ® .

Sympatholytic drugs

Drugs that interfere with sympathetic function are referred to as sympatholytic, or sympathoplegic, drugs. They primarily work as an antagonist    to the adrenergic receptors. They block the ability of norepinephrine or epinephrine to bind to the receptors so that the effect is “cut” or “takes a blow,” to refer to the endings “-lytic” and “-plegic,” respectively. The various drugs of this class will be specific to α-adrenergic or β-adrenergic receptors, or to their receptor subtypes.

Possibly the most familiar type of sympatholytic drug are the β-blockers. These drugs are often used to treat cardiovascular disease because they block the β-receptors associated with vasoconstriction and cardioacceleration. By allowing blood vessels to dilate, or keeping heart rate from increasing, these drugs can improve cardiac function in a compromised system, such as for a person with congestive heart failure or who has previously suffered a heart attack. A couple of common versions of β-blockers are metoprolol, which specifically blocks the β 2 -receptor, and propanolol, which nonspecifically blocks β-receptors. There are other drugs that are α-blockers and can affect the sympathetic system in a similar way.

Other uses for sympatholytic drugs are as antianxiety medications. A common example of this is clonidine, which is an α-agonist. The sympathetic system is tied to anxiety to the point that the sympathetic response can be referred to as “fight, flight, or fright.” Clonidine is used for other treatments aside from hypertension and anxiety, including pain conditions and attention deficit hyperactivity disorder.

Parasympathetic effects

Drugs affecting parasympathetic functions can be classified into those that increase or decrease activity at postganglionic terminals. Parasympathetic postganglionic fibers release ACh, and the receptors on the targets are muscarinic receptors. There are several types of muscarinic receptors, M1–M5, but the drugs are not usually specific to the specific types. Parasympathetic drugs can be either muscarinic agonists or antagonists, or have indirect effects on the cholinergic system. Drugs that enhance cholinergic effects are called parasympathomimetic drugs    , whereas those that inhibit cholinergic effects are referred to as anticholinergic drugs    .

Questions & Answers

Card 5 / 12: For whom would an appreciation of the structural characteristics of the human heart come more easily: an alien who lands on Earth, abducts a human, and dissects his heart, or an anatomy and physiology student performing a dissection of the heart on her very first day of class? Why?
Gelowe Reply
what are regular shaped cells with granules in the cytoplasam
Kabita Reply
PMNL
Dinu
I need sylubuss of clinical officers book
Omary Reply
cholesterol normal value is
BISWANATH Reply
less than 200mg/dl
Ashis
100 to159mg/dL
Dinu
Early this wk. I had some "A & P" questions & answers unfortunately didn't save them, Is there any way I can have them back ,so as 2 save them?. Thnx.
Kechi
what are the functions of the female reproductive system
Lister Reply
it produces the female egg necessary for reproduction, called the Ova or Oocytes. The system is designed to transport the Ova to the site of fertilization.
Kechi
Female reproductive system was mainly functioned to produce ova(ovum) (female eggs) Into which will be fertilized by male gamete to produce zygote
Omary
absolutely right
nimco
wa qalad nimco rage iska hubi
Khaliil
waxwalba ka fikirbay ubaahantahay
Ahmed
ha wayo jawabtoda wa qabyo nimco wey ku raacdat
Khaliil
ha wayo jawabtoda wa qabyo nimco wey ku raacday
Khaliil
wxayaabaha qaarkood waaa in aan u feejignaano
Ahmed
asc if I try female reproductive system has two function the first is to produce egg cell and the second is to protact and nourish the offspring until birth
Muriidi
what is stercobilinogen
Hancerich Reply
fecal urobilinogen. Created by bacteria in the gut. a chemical that gives feces brown color.
Blayne
next question pls.
Kechi
The rate of diffusion increases if the
stella
What's the answer?
Kechi
it's a breaking down of haemoglobin and it's a chemical made by bacteria
Dev
Thnx Dev Raj.
Kechi
yup so any more
Dev
yes I sure do need more "Questions" & "Answers". I'm learning whole lot. Thnx.
Kechi
what is the greatest muscle of the body
Lungu Reply
gluteus maximus
ABDULLAH
pls!!! more "A&P" questions & answers. Thnx.
Kechi
Gluteus maximus
THE
Describe anatomy of cardiovascular system?
cardiovascular system is a group of organs coming together to perform the circulation of blood. The organs invoked are the heart and the blood vessels with blood being the tissue. The heart is a pump and it pumps oxygenated blood through the systemic circuit and deoxygenated blood through the pulmon
bernard
pulmonary circuit.
bernard
more A&P questions pls. Thnx.
Kechi
If an ANOVA yields a significant F value, you could rely on ________ to test significant differences between group means.
Dane Reply
what's ANOVA
Cassandra
analysis of variance
Blayne
plz what you mean with "ANOVA" first
Fatima
anova means analysis of variance, a statistical method in which the variation in a set of observations is divided into distinct components.
Blayne
M value ot test
ABDULLAH
What does it mean by M value ot test?
Orpha
formation of red blood cells
Biketi Reply
explain why... lower back pain in ovarian cancer
Srijoni Reply
we says that protoplasm is the living part of us How?
Muzamil Reply
is the leaving part of our cellular structure.
Eric
it is the leaving part of our blood cellular structure also
ABDULLAH
what is receptor?
Preity Reply
an organ or cell able to respond to light, heat, or other external stimulus and transmit a signal to a sensory nerve.
Jessi
Has anyone taken the first exam?
Sandra
yes
yahye
yes
Allan
hey what is the process after your food is swallowed? how long does it take to get to the stomache until it is released as waste?
Fednise Reply
that is such a broad question. as you begin to swallow its various doses down the alimentary canal that brings the food into your stomach.then depending on whether it's a protein carbohydrate fat that dictates what function takes place in your stomach. these are all steps of digestion.
Joseph
typo sorry it's peristalsis , wave-like projections that push food down your alimentary canal etc. digestion starts in your mouth ends in your large intestines (colon anus)
Joseph
some of the many processes of digestion include hydrolysis dehydration synthesis denaturation of proteins etc. you have to be more specific.
Joseph
there's many different contributing factors the how long it takes food to convert into waste. remember fats, triglycerides proteins and carbohydrates all breakdown two different monomers and structures. you should be looking up metabolic processes.
Joseph
depending how much fiber you have in your diet dictates how much water is brought to your intestines that has to do with excretion whether fiber is insoluble or soluble. this is an anatomy and physiology app. to simply say the stomach will empty its contents in 2 to 3 hours would do you a disservice
Joseph
can the study of anatomy relate to medical technologies
Lean Reply
yes
Khh
absolutely
Jessi
yes...
Sherif
how can I understand micro biology and anatomy better.
Cassandra
yes
Kevin
someone to help me understand glycogeneogenesis
abel
what are the major branches of the aorta?
Kevin
look youtube video
Jessi

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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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