Neurophysiology: ANS- Pt 1

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Questions and Answers

Where are the cell bodies of the parasympathetic preganglionic neurons located?

In the sympathetic trunk

In the peripheral ganglion

In the brain stem and sacral spinal cord (S2 and S3) (correct)

In the spinal cord segments T1-L3

What type of axons do the postganglionic neurons usually have?

Fast conducting myelinated axons

No axons

Mixed type of axons

Slow conducting unmyelinated axons (correct)

What is the function of the preganglionic neuron in the ANS?

To connect the CNS with the target organ through a postganglionic neuron (correct)

To connect the CNS with the target organ directly

To inhibit the target tissue only

To connect the spinal cord with the skeletal muscle

What is the characteristic of the sympathetic trunk?

A fusion of sympathetic ganglia Signup and view all the answers

What type of tissue do the postganglionic neurons innervate?

Smooth muscle, cardiac muscle, and glandular tissue Signup and view all the answers

Where are the cell bodies of the sympathetic preganglionic neurons located?

In the spinal cord segments T1-L3 Signup and view all the answers

What is the characteristic of the synaptic buttons of the postganglionic neurons?

They are distributed along the length of the branches Signup and view all the answers

What is the difference between the sympathetic and parasympathetic systems in terms of their effect on target organs?

One must understand all separate functions in each organ to determine the effect of sympathetic or parasympathetic system Signup and view all the answers

What is the primary function of the sympathetic system in regards to physical activity?

To enable vigorous physical activity with rapid production of energy Signup and view all the answers

What is the primary function of the enzyme choline acetyltransferase in the synthesis of acetylcholine?

To convert acetyl-CoA and choline into acetylcholine Signup and view all the answers

Which part of the spinal cord is the anatomical origin of the sympathetic system?

Thoracolumbar spinal cord Signup and view all the answers

What is the effect of the sympathetic system on pupil size?

Dilation Signup and view all the answers

What is the final step in the synthesis of norepinephrine from tyrosine?

Hydroxylation of dopamine to form norepinephrine Signup and view all the answers

Which of the following is NOT a function of the sympathetic system?

Stimulation of stomach activity Signup and view all the answers

What is the function of acetylcholinesterase in the cholinergic system?

To convert acetylcholine into an acetate ion and choline Signup and view all the answers

Where does the conversion of norepinephrine into epinephrine take place?

In the adrenal gland Signup and view all the answers

How do the sympathetic and parasympathetic systems interact?

They work together in an antagonistic fashion Signup and view all the answers

What type of receptor is nicotinic receptor?

Ligand-gated ion channel Signup and view all the answers

What is the primary control center of the autonomic nervous system?

Hypothalamus Signup and view all the answers

Which system is the hypothalamus a part of?

Limbic system Signup and view all the answers

What is the role of the choline in the synthesis of acetylcholine?

To combine with acetyl-CoA to form acetylcholine Signup and view all the answers

What type of input does the hypothalamus receive directly or indirectly?

Both somatic and visceral sensory input Signup and view all the answers

Where is acetylcholine synthesized in the cholinergic nerve fibers?

In the terminal endings of the nerve fibers Signup and view all the answers

What is the result of the binding of acetylcholine to cholinergic receptors?

Activation of the postsynaptic neuron Signup and view all the answers

Which type of receptor binding results in the release of calcium from the ER?

Alfa1 receptors Signup and view all the answers

What is the effect of NE binding to Beta1 receptors in the heart?

Increase heart rate and contraction force Signup and view all the answers

What is the effect of dopamine on renal vascular smooth muscle?

Sympathetic impact Signup and view all the answers

What is the result of NE or EPI binding to Beta receptors?

Activation of adenylate cyclase Signup and view all the answers

What is the effect of Beta2 receptors on respiratory passages?

Relaxation of smooth muscle Signup and view all the answers

What is the effect of dopamine on sweat glands?

Sympathetic impact Signup and view all the answers

What is the result of NE binding to Alfa2 receptors?

Reduce cAMP levels Signup and view all the answers

What is the effect of Beta3 receptors on adipose tissue?

Release of fatty acids Signup and view all the answers

Which type of receptors are found at the neuromuscular junction in skeletal muscles?

NM (Muscle) receptors Signup and view all the answers

What is the result of acetylcholine binding to a nAChR?

Opening of sodium channels Signup and view all the answers

Which type of receptors are GPCRs?

Muscarinic receptors Signup and view all the answers

What is the effect of M2 and M4 muscarinic receptors?

Generation of IPSPs Signup and view all the answers

Which of the following is an example of the effect of M3 muscarinic receptors?

Contraction of bronchioles Signup and view all the answers

What is the effect of the activation of muscarinic receptors?

Results in EPSPs or IPSPs, depending on the receptor subtype Signup and view all the answers

Which type of receptors are located at the synapses between peripheral target tissues and sympathetic postganglionic neurons?

Adrenergic receptors Signup and view all the answers

What is the subtype of alfa receptors that signals through Gq?

Alfa1 Signup and view all the answers

Study Notes

Sympathetic System

Enables vigorous physical activity with rapid production of energy (ATP)
Increases heart rate, respiration, and blood flow to active muscles
Causes pupil dilation for increased vision
Anatomically arises from the thoracolumbar spinal cord, known as the thoracolumbar system

Functions of Sympathetic System

Dilates pupils
Inhibits salivation, stomach activity, gallbladder, and intestinal activity
Increases heartbeat
Relaxes airways and bladder
Stimulates release of glucose
Secretes epinephrine and norepinephrine
Promotes ejaculation and vaginal contraction

Autonomic Nervous System (ANS)

Under the control of the hypothalamus, which acts as an integrator
Afferent and efferent fibers of the ANS travel via the spinal cord and cranial nerves to connect between the CNS and target organs
Hypothalamic control is made by the brainstem (reticular formation) with some influence by the cerebral cortex
The hypothalamus is part of the limbic system, which generates autonomic emotional response

Preganglionic Neurons

In the ANS, a preganglionic and postganglionic neuron, in series, connects the CNS with the target organ
The somatic motor system has only one lower motor neuron (LMN) connecting the skeletal muscle and the spinal cord
The ANS preganglionic neuron has its cell body within the CNS, while its synapse is with the postganglionic neuron in the peripheral ganglion
Both sympathetic and parasympathetic system cells bodies of the preganglionic neurons are located in the CNS

Sympathetic Preganglionic Neurons

Cell bodies are located in the intermediolateral nucleus of the spinal cord segments T1-L3

Parasympathetic Preganglionic Neurons

Cell bodies are located in the brain stem and sacral spinal cord (S2 and S3)

Postganglionic Neurons

Cell body is in the peripheral ganglion in the PNS
The sympathetic system forms the sympathetic trunk, which is a fusion of several sympathetic ganglia in a chain-like form, on each side of the vertebral column
Postganglionic neurons usually have slow conducting unmyelinated axons
They innervate smooth muscle, cardiac muscle, and glandular tissue
They can excite or inhibit the target tissue

ANS Neurotransmitters

Acetylcholine Mechanism

Synthesized in the terminal endings and varicosities of the cholinergic nerve fibers
Steps: choline acetyltransferase converts acetyl-CoA and choline into acetylcholine, stored in a vesicle, released, and then converted into an acetate ion and choline by acetylcholinesterase, and recycled

Norepinephrine Mechanism

Synthesized in the axoplasm of the varicosities and stored at secretory vessels
Steps: tyrosine is converted into Dopa, then dopamine, then stored in vesicles, and then converted into norepinephrine, and finally converted into epinephrine in the adrenal gland

Postsynaptic Receptors

Cholinergic Receptors

Bind to acetylcholine and are classified into two types: nicotinic and muscarinic
Nicotinic receptors are ligand-gated ion channels found in the autonomic ganglia of both sympathetic and parasympathetic systems
Muscarinic receptors are GPCRs found on all effector cells that are stimulated by postganglionic cholinergic neurons
There are five subtypes of muscarinic receptors: M1, M2, M3, M4, M5, which signal through Gi or Gq (family of G proteins)

Postsynaptic Receptors: Adrenergic

Located at the synapses between the peripheral target tissues and sympathetic postganglionic neurons that release norepinephrine
Adrenergic receptors are also stimulated by the release of catecholamines from the adrenal glands
Adrenergic receptors are GPCRs, and can be further divided into alpha and beta receptors
Alpha receptors have the subtypes: alpha1 (Gq) and alpha2 (Gi), which induce vasoconstriction of most blood vessels, raising blood pressure
Beta receptors have the subtypes: beta1, beta2, beta3 (Gs), which increase heart rate and contraction force, relax smooth muscle, and release fatty acids

Postsynaptic Receptors: Dopamine

Mediates numerous physiological effects in the CNS and at the peripheral target organs
Dopamine is released by some postganglionic sympathetic neurons synapsing with specific organs, like renal vessels
Dopamine binds to dopaminergic receptors (which are GPCRs), and this binding will activate different cellular processes, resulting in EPSPs or IPSPs

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Description

Learn about the functions of the sympathetic nervous system, including its role in physical activity, heart rate, and other bodily functions. Understand how it stimulates and inhibits various bodily responses.