Chapter 15 - The Autonomic Nervous System Flashcards
What is Somatic Nervous System?
Somatic Nervous System:
Includes both sensory and motor neurons
Sensory neurons are related to:
Touch
Pain
Temperature
Proprioception (sense of self position
Sight
Hearing
Smell
Equilibrium
Motor neurons:
Innervate skeletal muscles
Axon of single myelinated Somatic motor neuron extends from CNS to skeletal muscle fiber it innervates
What is Autonomic Nervous System?
Autonomic Nervous System:
Receives input from sensory receptors located in:
Organs
Blood vessels
Muscles
Nervous System
What is Autonomic Motor Pathway?
Most Autonomic Motor Pathways consist of 2 motor neurons in series:
1- Preganglionic Neuron
2- Postganglionic Neuron
What is Preganglionic Neuron?
Preganglionic Neuron:
Cell body in CNS
Axon extends to an Autonomic Ganglion
Uses ACh
What is Postganglionic Neuron?
Postganglionic Neuron:
Has its unmyelinated axon extending from the Ganglion to the Effector
Sympathetic:
pre- ACh in ganglion
post- Norepinephrine at Effectors (Glands, Cardiac muscle, Smooth muscle)
Sympathetic:
pre- ACh in Adrenal Gland
post- Epinephrine and Norepinephrine at Effector (Blood vessels)
Parasympathetic:
pre- ACh at ganglion
post- ACh at Effector (Glands, Cardiac muscle, Smooth muscle)
What are the 2 Divisions of the Autonomic Nervous System?
Autonomic Nervous System divided into 2 Divisions:
1- Sympathetic Nervous System:
Fight-or-flight Division
Stimulation leads to increased alertness and metabolism to be ready for an emergency
(fast, tachycardia)
2- Parasympathetic Nervous System:
Rest-and-digest Division
Stimulation slows down most body activity
(slow, bradycardia)
What is Sensory Input?
1- SNS:
From somatic senses and special senses
2- ANS:
Mainly from Interoceptors
Some from somatic senses and special senses
What is Control of Motor Output?
1- SNS:
Voluntary control from Cerebral Cortex
With contributions from:
Basal Ganglia
Cerebellum
Brainstem
Spinal Cord
2- ANS:
Involuntary control from:
Hypothalamus
Limbic System
Brainstem
Spinal Cord
Limited control from Cerebral Cortex
What is Motor Neuron Pathway?
1- SNS:
One-neuron pathway:
Somatic motor neurons extending from CNS synapse directly with effector
2- ANS:
Usually 2-neuron pathway:
Preganglionic neurons extending from CNS synapse to Postganglionic neuron in Autonomic Ganglion
Postganglionic neuron extending from Ganglion synapse to Visceral Effector
Alternatively, Preganglionic neuron may extend from CNS synapse to Chromaffin Cells of Adrenal Medulla
What is Neurotransmitters and Hormones?
1- SNS:
All somatic motor neurons release only ACh
2- ANS:
All Sympathetic and Parasympathetic Preganglionic neurons release ACh
Most Sympathetic Postganglionic neurons release Norepinephrine
Those of most Sweat Glands release ACh
All Parasympathetic Postganglionic neurons release ACh
Chromaffin Cells of Adrenal Medulla of Adrenal Gland release Epinephrine and Norepinephrine
What is Effectors?
1- SNS:
Skeletal muscles
2- ANS:
Smooth muscle
Cardiac muscle
Glands
What is Responses?
1- SNS:
Contraction of skeletal muscle
2- ANS:
Contraction or relaxation of Smooth muscle
Increased or decreased rate and force of contraction of Cardiac muscle
Increased or decreased secretions of Glands
How are Motor Neurons of the ANS connected?
Each division of the ANS has 2 motor neurons:
1- Preganglionic Neuron:
Cell body in CNS
2- Postganglionic Neuron
Cell body and Dendrites in Autonomic Ganglion
Synapse with Preganglionic Axons in Autonomic Ganglion
Where are Cell Bodies of Preganglionic Neurons of Sympathetic Division?
Sympathetic Division:
Cell Bodies of Preganglionic Neurons are located in Lateral Horns of Gray Matter in the 12 Thoracic and first 2 or 3 Lumbar segments of Spinal Cord
(Thoracolumbar region)
The paired Sympathetic Trunk Ganglia are anterior and lateral to the vertebral column
Usually:
2 Cervical Ganglia
11 or 12 Thoracic Ganglia
4 or 5 Lumbar Ganglia
4 or 5 Sacral Ganglia
1 Coccygeal Ganglion
Where are Cell Bodies of Preganglionic Neurons of Parasympathetic Division?
Parasympathetic Division:
Cell Bodies of Preganglionic Neurons are in:
1- Nuclei of 4 Cranial Nerves:
CN III (Oculomotor)
CN VII (Facial)
CN IX (Glossopharyngeal)
CN X (Vagus)
2- Brainstem
3- Lateral Gray Matter of Sacral segments 2-4 of Spinal Cord
What are the 2 Types of Autonomic Ganglia?
There are 2 types of Autonomic Ganglia?
1- Sympathetic
2- Parasympathetic
There are 2 major types of Sympathetic Ganglia:
1- Sympathetic Trunk Ganglia:
Two of them, lie in vertebral row on either side of vertebral column
2- Prevertebral Ganglia:
Lie anterior to the vertebral column and close to the large abdominal arteries
How does Axon of Sympathetic Preganglionic Neuron connect with Postganglionic Neuron?
After Axons of Sympathetic Preganglionic Neurons enter Sympathetic Trunk Ganglia, the may connect with Postganglionic Neurons in one of 4 ways:
1- An Axon may synapse with Postganglionic Neuron in the 1st Ganglion it reaches
2- An Axon may ascend or descend to a higher or lower ganglion before synapsing with Postganglionic Neuron
3- An Axon may continue, without synapsing, through the Sympathetic Trunk Ganglion to end at a Prevertebral Ganglion and synapse with Postganglionic Neurons
4- An Axon may also pass, without synapsing, through the Sympathetic Trunk Ganglion and a Prevertebral Ganglion and then extend to the Adrenal Medullae
What is the Abdomen and Pelvis Major Autonomic Plexuses?
The abdomen and pelvis contain major Autonomic Plexuses which are often named after the artery along which they are distributed
These include:
Celiac (Solar) Plexus
Superior Mesenteric Plexus
Inferior Mesenteric Plexus
Renal Plexus
Hypogastric Plexus
What is Cranial Parasympathetic Outflow?
Cranial Parasympathetic Outflow:
Extends from Brainstem in 4 Cranial Nerves:
CN III (Oculomotor)
CN VII (Facial)
CN IX (Glossopharyngeal)
CN X (Vagus)
What is Sacral Parasympathetic Outflow?
Sacral Parasympathetic Outflow:
Extends from 2nd through 4th Sacral Spinal Nerve
What are ANS Neurotransmitters and Receptors?
Based on neurotransmitters they produce and release, Autonomic neurons are considered:
1- Cholinergic:
All Preganglionic neurons
Release ACh
Cholinergic Receptors include:
Nicotinic Receptors
Muscarinic Receptors
2- Adrenergic:
Sympathetic Postganglionic neurons
Release Norepinephrine (Noradrenalin)
What is Cholinergic Receptor?
Location:
Integral proteins in Postsynaptic plasma membranes
Activated by ACh
What is Nicotinic Receptor?
Type of Cholinergic Receptor
Location and Effect of Activation:
1- Plasma membrane of Postganglionic Sympathetic and Parasympathetic neurons
Excitation - impulses in Postganglionic neurons
2- Chromaffin Cells of Adrenal Medullae
Epinephrine and Norepinephrine secretion
3- Sarcolemma of skeletal muscle
Excitation - Contraction
What is Muscarinic Receptor?
Type of Cholinergic Receptor
Location and Effect of Activation:
1- Effectors innervated by Parasympathetic Postganglionic neurons
In some receptors, excitation
In others, inhibition
2- Sweat Glands innervated by Cholinergic Sympathetic Postganglionic neurons
Increased sweating
3- Skeletal muscle blood vessels innervated by Cholinergic Sympathetic Postganglionic neurons
Inhibition - Relaxation - Vasodilation
What is Adrenergic Receptor?
Location:
Integral proteins in Postsynaptic plasma membranes
Activated by Norepinephrine neurotransmitter
And the hormones Norepinephrine and Epinephrine
What is Alpha-1 Receptor?
Type of Adrenergic receptor
Location:
Smooth muscle fibers in blood vessels that serve salivary glands, skin, mucosal membranes, kidneys, and abdominal viscera
Radial muscle in Iris of eye
Sphincter muscles of stomach and urinary bladder
Effects of Activation:
Excitation - contraction
Which causes vasoconstriction, dilation of pupil, closing of sphincters
What is Alpha-2 receptor?
Type of Adrenergic Receptor
Location and Effect of Activation:
1- Salivary gland cells
Secretion of K+ and water
2- Sweat glands on palms and soles
Increase sweating
3- Smooth muscle fibers in some blood vessels
Inhibition - Relaxation - Vasodilation
4- Cells of Pancreatic Islets that secrete Insulin (Beta Cells)
Decreased Insulin secretion
5- Pancreatic Acinar Cells
Inhibition of digestive enzyme secretion
6- Platelets in blood
Aggregation to form platelet plug
What is Beta-1 Receptor?
Type of Adrenergic Receptor
Locations and Effect of Activation:
1- Cardiac muscle fibers
Excitation - Increased force and rate of contraction
2- Juxtaglomerular Cells of kidneys
Renin secretion
3- Posterior Pituitary
ADH secretion
4- Adipose Cells
Breakdown of triglycerides - release of fatty acids into blood
What is Beta-2 Receptor?
Type of Adrenergic Receptor
(resembles Alpha-2 Receptor)
Locations and Effects of Activation
1- Smooth muscle in walls of airways
In blood vessels that serve heart, skeletal muscle, adipose tissue, and liver
In walls of visceral organs, such as urinary bladder
Inhibition - Relaxation, which causes dilation of airways, vasodilation, and relaxation of organ walls
2- Ciliary muscle in eye
Inhibition - Relaxation
3- Hepatocytes in liver
Glycogenolysis (breakdown of Glycogen into Glucose)
What is Beta-3 Receptor?
Type of Adrenergic Receptor
Location:
Brown Adipose Tissue
Effects of Activation:
Thermogenesis
What are the Effects of ANS on Adrenal Medullae?
1- Sympathetic Stimulation (Alpha or Beta Adrenergic Receptors):
Secretion of Epinephrine and Norepinephrine (Nicotinic ACh Receptors)
2- Parasympathetic Stimulation (Muscarinic ACh Receptors)
No know effects
What are the Effects of ANS on Sweat Glands?
1- Sympathetic Stimulation (Alpha or Beta Adrenergic Receptors):
Increases sweating in most body regions (Muscarinic ACh receptors)
Sweating on palms and soles (Alpha-1)
2- Parasympathetic Stimulation (Muscarinic ACh Receptors)
No know effects
What are the Effects of ANS on Cardiac Muscle?
1- Sympathetic Stimulation (Alpha or Beta Adrenergic Receptors):
Increased HR and force of Atrial and Ventricular contractions (Beta-1)
2- Parasympathetic Stimulation (Muscarinic ACh Receptors)
Decreased HR
Decreased force of Atrial contraction
What are the Effects of ANS on Iris Radial Muscle?
1- Sympathetic Stimulation (Alpha or Beta Adrenergic Receptors):
Contraction - Dilation of pupil (Alpha-1)
2- Parasympathetic Stimulation (Muscarinic ACh Receptors)
No know effects
What are the Effects of ANS on Iris Circular Muscle?
1- Sympathetic Stimulation (Alpha or Beta Adrenergic Receptors):
No know effects
2- Parasympathetic Stimulation (Muscarinic ACh Receptors)
Contraction - Constriction of pupil
What are the Effects of ANS on Ciliary Muscle of Eye?
1- Sympathetic Stimulation (Alpha or Beta Adrenergic Receptors):
Relaxation to adjust shape of Lens for distant vision (Beta-2)
2- Parasympathetic Stimulation (Muscarinic ACh Receptors)
Contraction for close vision
What are the Effects of ANS on Urinary Bladder?
1- Sympathetic Stimulation (Alpha or Beta Adrenergic Receptors):
Relaxation of muscular wall (Beta-2)
Contraction of internal urethral sphincter (Alpha-1)
2- Parasympathetic Stimulation (Muscarinic ACh Receptors)
Contraction of muscular wall
Relaxation of internal urethral sphincter
What are the Effects of ANS on Lung Bronchial Muscle?
1- Sympathetic Stimulation (Alpha or Beta Adrenergic Receptors):
Relaxation - Airway dilation (Beta-2)
2- Parasympathetic Stimulation (Muscarinic ACh Receptors)
Contraction - airway constriction
What are the Effects of ANS on Uterus?
1- Sympathetic Stimulation (Alpha or Beta Adrenergic Receptors):
Inhibits contraction in nonpregnant women (Beta-2)
Promotes contraction in pregnant women (Alpha-1)
2- Parasympathetic Stimulation (Muscarinic ACh Receptors)
Minimal effect
What are the Effects of ANS on Hair Follicles, Arrector Pili Muscle?
1- Sympathetic Stimulation (Alpha or Beta Adrenergic Receptors):
Contraction - erection of hairs resulting in goose bumps (Alpha-1)
2- Parasympathetic Stimulation (Muscarinic ACh Receptors)
No known effects
What are the Effects of ANS on Coronary (Heart) Arterioles?
1- Sympathetic Stimulation (Alpha or Beta Adrenergic Receptors):
Relaxation - Vasodilation (Beta-2)
Contraction - Vasoconstriction (Alpha-1 and Alpha-2)
Contraction - Vasoconstriction (Muscarinic ACh receptors)
2- Parasympathetic Stimulation (Muscarinic ACh Receptors)
Contraction - Vasoconstriction
What is Integration and Control in ANS?
Some functions are controlled by Autonomic Reflexes that occur when nerve impulses pass through an Autonomic Reflex Arc:
HR and force of ventricular contraction
BP and blood vessel diameter
The Reflex Arc is composed of:
Receptor
Sensory Neuron
Integrating Center
Motor Neuron
Effector
What are some ANS Disorders?
1- Autonomic Dysreflexia
2- Raynaud Phenomenon
