AUTONOMIC NERVOUS SYSTEM 1
Autonomic Nervous System Receptors
Liberty University
EDUC 562: Introduction to Higher Education
1 November 2023
AUTONOMIC NERVOUS SYSTEM 2
Autonomic Nervous System Receptors
Autonomic Nervous System Neurotransmitters and Receptors
The visceral functions of one’s internal organs are controlled by their autonomic nervous
system. The ability of the digestive, respiratory, cardiovascular, urinary, and reproductive
systems to operate as they are intended require the autonomic nervous system to work as its
supposed to. There are several medications that are used to treat various medical conditions
associated with the nervous system. As such, it is important to have a full understanding of how
important the physiology of the autonomic nervous system is to determine which medication will
be best to treat the conditions while also taking into consideration the adverse effects that happen
as a result. Knowing the sympathetic and parasympathetic nervous systems and the
communication that takes place between the neurotransmitters and the receptors allows one to
understand the activities that take place and the ways in which one can manipulate how the
medications work on the diseases.
The ANS works on the body internally to maintain homeostasis by modifying the
activities that the body performs. The site by which the functions the ANS carries out
transmissions across the pre and postsynaptic neurons is the effector tissues, beginning with the
release of the neurotransmitters from the preganglionic axon. Once the neurotransmitters are
released, they diffuse across the synaptic cleft with them binding to the receptors on the
postganglionic neuron that are specific to the necessary activities. When the process happens,
there is stimulation of the ligand-receptor which then initiate signaling pathways through the
target bells which, through negative feedback, activates the desired physiological effects.
Specific Receptor - Location, Signaling, and Physiologic Effects of Stimulation
AUTONOMIC NERVOUS SYSTEM 3
There are four major classifications of neurotransmitters include amino acids,
cholinesters, neuropeptides, and biogenic amines. These neurotransmitters are responsible for
stimulating the sympathetic and parasympathetic nervous systems and work as either antagonists
or agonists for certain receptors at very specialized locations. Two distinct subtypes of receptors
can be found within the four classifications: acetylcholine and adrenoreceptors. Acetylcholine
receptors stimulate processes within the parasympathetic nervous system, while the
adrenoreceptors, stimulated by norepinephrine (through synapses) and epinephrine (through
endocrine system), stimulate the sympathetic nervous system.
The acetylcholine receptors are made up of muscarinic and nicotinic receptors while the
adrenoreceptors are made up of α1, α2, β1 and β2 subtypes. Located on plasma membranes in
postsynaptic effector tissue, β1 receptors can be found in cardiac cells that are located in the
muscles of the ventricles as well as the sinoatrial and atrioventricular nodes as well as in other
processes such as secreting renin, glucogenesis, as well as the brain, lipolysis, and the ciliary
body epithelium. Activating the β1 receptor is facilitated and increase in the heart rate due to the
sinoatrial nodes as well as an acceleration in the conduction velocity through the atrioventricular
node, and an increase in the secretion in renin from the renal juxtaglomerular cells.
Pharmacological Agents
The adrenoreceptor agonist norepinephrine is responsible for several processes that
increase many systems in the body including hypertension, urinary retention, tachycardia,
tremors, and piloerection. Whereas the antagonists atenolol and propranolol are responsible for
decreases in body systems, to include hypotension, bradycardia, and bronchospasms. With the
mechanisms of action these antagonists have on the body, they are used to treat many conditions
such as hypertension, heart failure, angina, myocardial infarctions, heart arrhythmias, anxiety
AUTONOMIC NERVOUS SYSTEM 4
disorders, and migraines. Being that these medications cause the cardiac muscle contractility to
be decreased, they are effective at slowing down the heart beat and lowering the blood pressure.
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