Chapter 15: Autonomic Nervous System Flashcards
Somatic Nervous System
Consists of:
Somatic motor neurons that innervate (or excitation) the skeletal muscles of the body.
Autonomic Nervous System
Part of the nervous system that regulates cardiac muscle, smooth muscle and glands.
Motor neurons excite and inhibit ongoing activities in the cardiac muscle, smooth muscle and gland tissue.
Visceral Effectors
Tissue: Cardiac muscle, smooth muscle and glands that is associated with visceral of the body.
Biofeedback
Monitoring device that displays information about the bodies function such as: HR, BP and enchants the ability to learn conscious control.
The ANS is somewhat dependent on higher centers.
Interoceptors
Sensory receptors located in blood vessels, visceral organs, muscle and nervous system that monitors conditions in the internal environment.
2 Main Branches of ANS
- Sympathetic nervous system: promotes fight or flight
- Parasympathetic nervous system: promotes rest and digest
Duel Innervation
Arrangement of the ANS branches where most organs receive nerves from both divisions.
3rd Division of ANS
Enteric Nervous System.
Operates involuntary but can be regulated by other divisions of ANS.
Contains: sensory neurons, interneurons, motor neurons that extend most of the length of the GI tract.
Can integrate information from sensory neurons while providing uncut to motor neurons .
Autonomic Ganglion
Collection of neuronal cell bodies in the CNS.
2 major groups:
1. Sympathetic ganglia
2. Parasympathetic ganglia
Chromaffin Cells
Specialized cells in adrenal medulla. In some autonomic pathways, the first motor neuron will extend to this type of cell.
With stimulation by sympathetic Preganglionic neurons, these cell release a mixture of catecholamines hormones: about 80% epinephrine, 20% norepinephrine and a trace of dopamine. These hormones circulate throughout the body.
Sensory Input SNS
From somatic senses and special senses
Sensory Input ANS
Mainly from interoceptors, some from somatic senses and special senses.
Control of Motor Input SNS
Voluntary control from cerebral cortex
contributions from basal ganglia, cerebellum, brain stem and spinal cord.
Control of Motor Output ANS
Involuntary control from hypothalamus, limbic system, brain stem and spinal cord.
Motor Neuron Pathway
One neuron pathway: somatic motor neuron extending from CNS synapse directly with effector,
Motor Neuron Pathway ANS
Usually 2 pathways
1. Preganglionic neurons extending from CNS synapse with in autonomic ganglion and extending from ganglion synapse with visceral effector.
2. Preganglionic neurons may extend from CNS to synapse with chromaffin cells of adrenal medulla.
Neurotransmitter and Hormones SNS
All somatic motor neurons release only ACh.
Neurotransmitters and Hormones ANS
All sympathetic and parasympathetic Preganglionic neurons release ACh.
Effectors SNS
Skeletal Muscle
Effectors ANS
Smooth muscle, cardiac muscle and glands
Responses SNS
Contraction of skeletal muscle
Responses ANS
Contraction or relaxation of smooth muscle.
Increased or decreased rate and force of contraction of cardiac muslce
Increased or decreased secretions of glands.
Preganglionic Neurons of Sympathetic Division
Axons are known as : thoracolumbar outflow
Neurons have their cell bodies in the lateral horns of the gray matter in the 12 thoracic segments and the first 2 lumbar segments of the spinal cord.
An axon may synapse with ganglion it reaches first.
An axon may travel to a higher or lower ganglion before synapsing with postganglionic neurons.
The axons of incoming neurons pass up or down from ganglion to ganglion in the sympathetic trunk.
Preganglionic Neurons Parasympathetic Division
Axons here are known as : craniosacral outflow
There are no autonomic nerve cell bodies in the cervical segment of spinal cord.
Neurons are located in the nuclei of 4 cranial nerves in brainstem III, VII, IX, X and in gray matter of the 2nd to 4th sacral segments of the spinal cord.
Axons of parasympathetic Divison pass to terminal ganglia near or within a visceral effector.
Parasympathetic Divison of ANS
Also known as craniosacral division
Distributed is limited mainly to head and viscera of thorax, abd, pelvis and some blood vessels.
White and gray rami are not present.
Consists of 2 motor neurons.
Neurotransmitter Preganglionic neurons releases ACh
Rest and digest effects
Muscarinic ACh receptors result in decreased HR and force of contractions.
Sympathetic Ganglia
Sites of synapses between the sympathetic Preganglionic and postganglionic neurons.
Two major types:
1. Sympathetic trunk: lie in vertical row on either side of the vertebral column. Extend from base of the skull to coccyx.
2. Prevertebral ganglia: lies anterior to the vertebral column and close to the large abd arteries. Innervate organs below the diaphragm.
Parasympathetic Ganglia
Preganglionic axons synapse with postganglioic neurons in terminal ganglia. Most of these ganglia are located close to or within the wall of a visceral organ.
Autonomic Plexuses
Found in thorax, abd and pelvis axons of both sympathetic and parasympathetic neurons in tangled networks.
Many lie along major arteries.
Cardiac Plexus
Major plexuses in thorax. Supplies the heart.
Pulmonary Plexus
Major plexuses in the thorax, supplies the bronchial tree.
Celiac Plexus
Largest autonomic plexus, surrounds the celiac trunk.
Contains 2 large celiac ganglion and 2 aorticorenal ganglion
Axons are distributed to the stomach, spleen, pancreas, liver, gallbladder, kidneys, adrenal medulla, testes and ovaries.
Superior Mesenteric Plexus
Contains the superior mesenteric ganglion and supplies the small and large intestines.
Inferior Mesenteric Plexus
Contains the inferior mesenteric ganglion, which innervate the large intestine.
Hypogastric Plexus
anterior to 5th lumbar vertebra, supplies the pelvic viscera.
Renal Plexus
Contains the renal ganglion, supplies the renal arteries within the kidneys and ureters.
White Ramus
Short pathway
White Rami Communications
White rami structures containing sympathietic Preganglionic axons that connect the anterior ramus of the spinal nerve with the ganglia of the sympathetic trunk.
The “white” indicates they contain myelinated axons.
Pathway from Spinal Cord to Sympathetic Trunk
Preganglionic axons leave spinal cord along the somatic motor neurons at the same segmental level.
Exit through the intervertebral foramina.
Myelinated Preganglionic sympathetic axons pass into the anterior root of a spinal nerve.
Enter spinal pathway, white rami before passing to the nearest sympathetic trunk ganglion on the same side.
Sympathetic Trunk Ganglia
Arranged anterior and lateral to the vertebral column, one on either side.
There are 3 cervical, 11 or 12 thoracic, 4 or 5 lumbar, 4 or 5 sacral and 1 coccygeal ganglion.
These ganglia extend inferiorly from the neck, chest and abdomen to the coccyx, they receive Preganglionic axons only from he thoracic and lumbar segments of the spinal cord.
Superior Cervical Ganglion
Serve the head and heart.
Disturbed to sweat glands, smooth muscle of the eye, blood vessels of the faces, lacrimal glands, pineal glands, nasal mucosa, salivary glands and heart.
Middle Cervical Ganglion and Inferior Cervical Ganlion
Both innervate the heart and blood vessels of the neck, shoulder and upper limb.
4 Pathways from Sympathetic Trunk Ganglia to Visceral Effectos
Axons leave the sympathetic truncated in 4 possible ways:
1: they can enter spinal nerves
2: They can form cephalic periarterial nerves
3: they can form sympathetic nerves
4: they can form splanchnic nerves
Gray Rami Comminmications
Structures contains sympathetic postganglionic axons that connect the ganglia of the sympathetic trunk to spinal nerved.
The “gray” indicates that they contain unmyelinated axons.
Cephalic Pariarterial Nerves
Formed by axons of postganglionic neurons that leave the sympathetic trunk.
These nerves extend to the head by wrapping around and following the course of various arteries that pass from the neck to the head.
Provide Innervation to visceral effectors in the skin of the face.
Cranial Outflow
Has 4 pairs of ganglia and the ganglia associated with the vagus X nerve.
1. Ciliary ganglia: lateral to each optic II nerve near posterior aspect of the orbit.
2. Pterygopalatine ganglia: lateral to the sphenopalatine foramen, between the sphenoid and palatine bones. Receives axons from facial VII nerve.
3. Submandibular Ganglia: found near the ducts of the submandibular salivary glands. Recieved axons from facial VII nerve.
4. Otic Ganglia: inferior to each foramen ovale. Recieve axons from the Glossopharyngeal IX nerve.
Preganglionic Outflow
Preganglionic axons that leave the brain as part of the vagus X nerves carry nearly 80% of the total crainosacral outflow.
Cholinergic Neurons
Release neurotransmitter ACh.
Include:
1: all sympathetic and parasympathetic Preganglionic nerurons
2: sympathetic postganglionic neurons that innervate most sweat glands
3: all parasympathetic postganglionic neurons .
Cholingeric Receptor
Integral proteins in Postsynaptic PM. Activated but neurotransmitter acetylcholine.
2 types of receptors:
1: nicotinic
2: muscarinic
Nicotinic Receptor
Present in plasma membrane of dendrites and cell bodies of both sympathetic and parasympathetic postganglionic neurons, PM of chromaffin cells and in motor end plate at the neuromuscular junction.
Named because nicotine mimics the action of ACh by binding to these receptors.
Muscarinic Receptors
Present in the plasma membrane of all effectors innervate by parasympathetic postganglionic axons.
Named because a mushroom poison called muscadine mimics the actions of ACh by binding them.
Adrenergic Receptor
Integral proteins in Postsynaptic plasm membrane
Activated by the neurotransmitter norepinephrine and the hormones norepinephrine and epinephrine.
2 main types:
1. Alpha (a) receptors
2. Beta (B) receptors
These 2 receptors are found on visceral effectors innervate by most sympathetic postganglionic axons.
Adrenergic Neurons
Release norepinephrine (NE) or Noradrenaline.
Norepinephrine (NE)
Stored in synaptic vesicles and released by exocytosis. NE diffuse across the synaptic cleft and bind to specific Adrenergic receptors in the Postsynaptic membrane.
Inactivated by: monoamine oxidase (MAO).
Agonist
Is a substance that binds to and activates a receptor, in the process of mimicking the effect of a natural neurotransmitter or hormone.
Antagonist
Is a substance that binds to and blocks a receptor, thereby preventing a natural neurotransmitter or hormone from exerting its effect.
Sympathetic Division of ANS
Also known as thoracolumbar
Distributed to wide regions in body: skin, sweat glands, arrector pili, adipose tissue, smooth muscle in blood vessel.
Consists of 2 motor neurons.
White and gray rami are both present.
Neurotransmitters: Preganglionic neurons release ACh and NE
Fight or flight responses
Adrenergic beta 1 receptors stimulate increased HR and force of contractions.
Autonomic Tone
The balance between sympathetic and parasympathetic activity.
Fight or Flight Responses
Happen when the sympathetic division is activated. Release of hormones by adrenal medulla.
Set in option a series of physiological responses:
Pupils of the eyes dilate
HR, force of heart contraction, and blood pressure increase.
Airway dilates
Blood flow decreased to kidneys and GI tract
Increased blood flow to skeletal and cardiac muscles, liver, adipose tissue.
Liver performs glycogenolysis, increases blood glucose levels
Processes that are not essential for meeting the stressful situation are inhibited.
Rest and Digest Responses
Activity of parasympathetic division enchant the rest and digest. Supports body functions that conserve and restore body energy during times of rest and recovery.
SLUDD:
S: salivation
L: lacrimation
U: Urination
D: Digestion
D: Defecation
`Autonomic (Visceral) Reflexes
Consists of a receptors, a sensory neuron, integrating center, 2 autonomic motor neurons and visceral effectors.
In an autonomic reflex arc, two motor nervousness connect the CNS to an effector.
Play a role in regulating controlled conditions in the body, such as blood pressure, etc.
Components of Autonomic Reflex Arc
Sensory Receptor: the distal end of a sensory neuron, responds to stimulus and produces a change that will trigger a nerve impulse
Sensory Neuron: Conducts nerve impulses form the receptor to the CNS.
Integrating Center: interneurons in the CNS, signals from sensory neurons to motor neurons
Motor Neurons: triggered by integrating center propagate out of the CNS along motor neurons to an effector.
Effector: are smooth and cardiac muscle, and glands.
Hypothalamus in the ANS
Is the major control and integration center of the ANS.
Recited sensory input related to visceral functions, olfaction, gestation as well as changes in temp, osmolarity and level of substances in the blood.
Somatic Reflexes
Are involuntary. Controlled by integrating centers in the brainstem and spinal cord.
Saltatory Conduction
Needs a myelinated Preganglionic neuron.
Postganglionic neurons are unmyelinated so they cannot conduct a Saltatory conduction.
