How are the pre-ganglionic and post-ganglionic motor neurons characterized in the Sympathetic Nervous System (SNS)?
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Pre-ganglionic motor neurons are short, while post-ganglionic motor neurons are long.
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How are the pre-ganglionic and post-ganglionic motor neurons characterized in the Sympathetic Nervous System (SNS)?
Pre-ganglionic motor neurons are short, while post-ganglionic motor neurons are long.
What functions does the Autonomic Nervous System (ANS) control?
It controls the visceral functions of the body by monitoring (sensory) and adjusting (motor) the activity of cardiac muscle, smooth muscle, glands, and adipose tissue.
What does the Autonomic Nervous System innervate?
Smooth muscle, cardiac muscle, glands, and adipose tissue.
What is the mechanism of action of anticholinergic drugs like amitriptyline (Elavil)?
They inhibit the effects of acetylcholine (ACH) systemically via muscarinic receptors.
What are some actions of the parasympathetic nervous system (PNS)?
Digestion, urination, miosis, bronchoconstriction, bradycardia, lacrimation, salivation.
What neurotransmitter is released by the postganglionic neuron in the SNS?
Norepinephrine (NE)
What are examples of the effects of Sympathetic Nervous System (SNS) activity?
Increased heart rate, dilation of pupils, and relaxation of airways.
What is the primary role of the Sympathetic Nervous System (SNS)?
Fight or flight.
Which specific adrenergic receptor is responsible for the effect produced in an organ by the SNS?
The specific adrenergic receptor responsible for the effect produced in an organ by the SNS can be identified using Table 11.3 in Stanfield's Principles of Human Physiology.
What is the function of baroreceptors in the autonomic reflex?
Baroreceptors detect changes in blood pressure and activate afferent nerve fibers to send messages to the CNS.
What is the synapse target of the post-ganglionic neuron in the Parasympathetic Nervous System?
The post-ganglionic neuron synapses with the effector organ (e.g., heart, stomach).
What are some gastrointestinal side effects of anticholinergic drugs?
Xerostomia, constipation, ileus, and nausea and vomiting.
Can the Autonomic Nervous System response be excitatory or inhibitory at the target organ synapse?
It can be either excitatory or inhibitory depending on the specific receptor on the target cell.
On most target organs, norepinephrine binds to which receptors?
Adrenergic receptors (α/β)
What cells in the adrenal medulla contain the enzyme phenylethanolamine-N-methyltransferase (PNMT)?
Chromaffin cells
What is the role of the M3 receptor in the autonomic nervous system?
M3 receptors mediate smooth muscle contraction, glandular secretion, and nitric oxide release.
What are the major effects produced by postganglionic fibers entering the thoracic cavity in sympathetic nerves?
Acceleration of heart rate and increasing the strength of cardiac contractions, dilation of respiratory passageways.
How does the addition of epinephrine affect the systemic absorption of injected local anesthetics?
Epinephrine causes vasoconstriction via alpha 1 receptors at the site of administration, which decreases blood absorption, facilitates neuronal uptake, enhances quality of analgesia, prolongs duration of action, and limits toxic side effects.
Which adrenergic receptors does norepinephrine (NE) activate?
Norepinephrine (NE) activates both α and β receptors, but it activates β1 more than β2, indicating a higher affinity for β1.
Why are the ganglia of the SNS close to the CNS?
Because the pre-ganglionic neurons are short.
Where does the pre-ganglionic neuron of the Parasympathetic Nervous System exit?
The pre-ganglionic neuron exits the brain and sacral region of the spinal cord.
Which divisions of the autonomic nervous system are involved in the reflex response to raise blood pressure?
Both the sympathetic and parasympathetic divisions.
Where does the post-ganglionic neuron synapse in the Autonomic Nervous System?
With the target organ.
Which areas in the brainstem and hypothalamus integrate autonomic functions?
Autonomic integrating areas in the brainstem and hypothalamus.
What role does the adrenal medulla play in the SNS?
It releases epinephrine (80%) and norepinephrine (20%) as neurohormones.
What are examples of the effects of Parasympathetic Nervous System (PNS) activity?
Decreased heart rate, constriction of pupils, and stimulation of digestive activities.
What is the role of the β2 receptor in the autonomic nervous system?
β2 receptors cause relaxation of smooth muscles in the airways, blood vessels, and certain other tissues.
When does the Sympathetic Nervous System dominate?
When the body is stressed, physically or emotionally.
Why is an EpiPen used for allergic reactions?
Epinephrine (EPI) has a greater affinity for β2 receptors than norepinephrine (NE), making it more effective for treating allergic reactions.
What type of receptors are all muscarinic receptors?
GPCRs (G-protein-coupled receptors)
Where are M2 receptors primarily located?
Myocardium, cardiac autorhythmic cells, smooth muscle (GI sphincters)
What is the relative affinity of epinephrine (EPI) for β2 receptors compared to norepinephrine (NE)?
Epinephrine (EPI) has a higher affinity for β2 receptors compared to norepinephrine (NE).
What regions of the spinal cord do the SNS pre-ganglionic nerves leave from?
The thoracic and upper lumbar regions.
What is the baroreceptor reflex?
An autonomic reflex that regulates blood pressure.
Which components are involved in autonomic reflexes?
Receptors in peripheral tissue, afferent (sensory) fibers, stimulus, integrating center in spinal cord (or brain), pre-ganglionic neuron, autonomic ganglion (sympathetic or parasympathetic), post-ganglionic neuron, peripheral effector, and response.
What condition can occur in patients taking anti-cholinesterases for Alzheimer’s Disease?
Sialorrhea (drooling).
What neurotransmitter is released by the preganglionic neuron in the SNS?
Acetylcholine (ACH)
How do epinephrine and norepinephrine function when released by the adrenal medulla?
They are released into the blood as hormones and circulate throughout the body, binding to adrenergic receptors.
What is the primary role of the Parasympathetic Nervous System (PNS)?
Rest and digest.
What are the major effects produced by sympathetic postganglionic fibers in spinal nerves?
Constriction of cutaneous blood vessels, acceleration of blood flow to skeletal muscles and brain, stimulation of energy production and use by skeletal muscle tissue, release of stored lipids from subcutaneous adipose tissue, stimulation of secretion by sweat glands, stimulation of arrector pili, dilation of the pupils and focusing for distant objects.
What is the function of varicosities in the Autonomic Nervous System?
They are used at the synapse between the postganglionic neuron and the effector cell.
What neurotransmitter is released by the preganglionic neuron in the PNS?
Acetylcholine
Which type of receptor does acetylcholine bind to on the target organ in the PNS?
Muscarinic cholinergic receptors
Where are M3 receptors primarily located?
Exocrine glands, smooth muscle (bladder, airways), endothelium; sweat glands (sympathetic function)
Where are the ganglia of the SNS located in relation to the CNS?
The ganglia are located close to the CNS.
Which adrenergic receptor does epinephrine (EPI) have a higher affinity for when compared to norepinephrine (NE)?
Epinephrine (EPI) has a higher affinity for β2 receptors compared to norepinephrine (NE), as seen in the use of EPI Pens.
What are the characteristics of the pre-ganglionic and post-ganglionic motor neurons in the Parasympathetic Nervous System (PNS)?
The PNS has long pre-ganglionic motor neurons and short post-ganglionic motor neurons.
Where are the ganglia of the Parasympathetic Nervous System located?
The ganglia are located close to or on the target organ.
How many neurons are involved in the pathway between the CNS and target organs in the Autonomic Nervous System?
Two neurons (pre-ganglionic and post-ganglionic) that synapse in ganglia.
What type of response can the Somatic Nervous System cause at the Neuromuscular Junction (NMJ)?
It can only cause excitation because ACH binds to Nicotinic ACH Receptors on skeletal muscle cells.
What receptors do acetylcholine bind to on the postganglionic neuron in the SNS?
Nicotinic cholinergic receptors (Nn)
What is dual innervation in the context of the Autonomic Nervous System?
Both divisions (SNS and PNS) innervate most effector organs.
What is the role of the M2 receptor in the autonomic nervous system?
M2 receptors are involved in decreasing heart rate and inhibiting acetylcholine release in the heart.
What is the role of the α1 receptor in the autonomic nervous system?
α1 receptors cause vasoconstriction and increase peripheral resistance, leading to an increase in blood pressure.
What is the nature of the effects produced by the Sympathetic Nervous System?
Primarily catabolic in nature.
Which type of receptor does acetylcholine bind to on the postganglionic neuron?
Nicotinic cholinergic receptors (Nn)
Where are M4 receptors primarily located?
CNS, Vagus nerve
What is a key function of the SNS during a stress response?
The SNS can selectively activate effectors or elicit a mass discharge.
What happens to blood pressure after blood loss due to hemorrhage?
Blood pressure initially decreases.
How do the effects of the Parasympathetic Nervous System differ from those of the Sympathetic Nervous System?
The PNS tends to have more localized effects in the body, such as urination, versus the mass activation of many tissues at once that occurs in the SNS.
What are the types of autonomic reflexes?
Short reflex and long reflex.
Are the effects of the parasympathetic nervous system primarily anabolic or catabolic?
Anabolic.
What are the exceptions to norepinephrine binding to adrenergic receptors in the SNS?
Acetylcholine binds to muscarinic receptors on sweat glands and dopamine on renal vascular smooth muscle.
How do the activities of the PNS and SNS tend to interact?
PNS and SNS activities tend to be antagonistic.
Which system is usually predominant at rest?
The Parasympathetic Nervous System (PNS).
What is the role of the β1 receptor in the autonomic nervous system?
β1 receptors increase heart rate and force of myocardial contraction.
Why is albuterol used for the treatment of asthma?
Albuterol is a Beta 2 selective agonist that causes bronchodilation by relaxing smooth muscle.
Where are M1 receptors primarily located?
Stomach (secretions), salivary glands
Where do the pre-ganglionic neurons of the SNS exit the spinal cord?
They exit the thoracic and lumbar regions of the spinal cord.
What does the Somatic Nervous System innervate?
Skeletal muscle.
How many neurons are involved in the pathway between the CNS and skeletal muscle in the Somatic Nervous System?
A single neuron.
What happens to blood pressure when baroreceptors detect a decrease in BP?
Afferent nerve fibers send a message to the CNS to initiate a reflex response to regulate and raise BP.
Which branch of the autonomic nervous system dominates at rest?
The parasympathetic nervous system.
What are the two divisions of the Autonomic Nervous System?
Sympathetic (SNS) and Parasympathetic (PNS)
What is the function of the enzyme phenylethanolamine-N-methyltransferase (PNMT) in the adrenal medulla?
It catalyzes the conversion of norepinephrine (NE) to epinephrine (EPI), requiring cortisol.
What happens to SNS activity when PNS activity increases?
SNS activity decreases.
What are the names of the two neurons that run from the CNS to the effector organs?
Preganglionic Neuron and Postganglionic Neuron.
Which receptors do epinephrine (EPI) and norepinephrine (NE) bind to?
α1, α2, β1, β2, β3 receptors.
Which muscarinic receptors activate Gq-PLC receptors causing an increase in intracellular Ca2+?
M1, M3, and M5
Where are M5 receptors primarily located?
CNS
How many neurons run from the CNS to the effector organs in the Autonomic Nervous System, and where do they synapse?
Two neurons; they synapse in structures called ganglia.
What is ganglia in the context of the peripheral nervous system?
Gray matter in the peripheral nervous system and sites of synaptic communication.
What neurotransmitter is released by the postganglionic neuron in the PNS?
Acetylcholine
Which muscarinic receptors inhibit adenylyl cyclase and regulate specific ion channels via coupling with Gi?
M2 and M4
What happens when ACh binds to NM receptors?
It elicits contraction.
What is the function of nicotinic receptors?
They are non-specific cation channels that allow Na+ influx and K+ efflux, causing depolarization.
What causes relaxation after ACh-induced contraction?
Relaxation occurs when the nerve stops releasing ACh.
