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65 Cards in this Set
- Front
- Back
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The somatic nervous system (SNS) (functional)
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a. Conveys input from receptors of the special senses, and general somatic receptors (pain, thermal, tactile, proprioception); and are consciously perceived.
b. Motor neurons are excitatory and innervate skeletal muscles and produce conscious voluntary movements. |
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The autonomic nervous system (ANS)(functional)
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a. Conveys input from interoceptors (e.g. blood vessels and organs) and usually it is not consciously perceived.
b. ANS motor neurons excite or inhibit ongoing cardiac or smooth muscle movement or gland activity that is usually involuntary. The motor ANS has two divisions, sympathetic and parasympathetic. |
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The somatic nervous system (SNS) (structural)
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A single somatic motor neuron extends from the CNS to the effector where it releases the neurotransmitter acetylcholine (ACh).
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The autonomic nervous system (ANS)(stuctural)
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2. In the ANS motor pathway, one autonomic motor neuron (the preganglionic neuron) extends from the CNS to an autonomic ganglion (outside of CNS).
Another autonomic motor neuron (postganglionic neuron) extends from the ganglion to an effector. Autonomic motor neurons release ACh or norepinephine (NE). |
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Preganglionic neurons
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1. The cell bodies of those in the sympathetic division are in the lateral gray horn of the 12 thoracic and 1st two lumbar segments of the spinal cord
2. Cell bodies of the parasympathetic division occur in nuclei of four cranial nerves (III, VII, IX and X)in the brain stem, or the lateral gray horns of 2nd-4th sacral segments of the spinal cord. |
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Autonomic ganglia
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divided into three groups:
Sympathetic trunk (paravertebral) ganglia Prevertebral ganglia Terminal (intramural) ganglia |
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Sympathetic trunk (paravertebral) ganglia (Examples, sup-mid-inf cervical ganglia)
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- lie in a vertical row on either side of the vertebral column, are sympathetic and mainly innervate organs above the diaphragm.
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Prevertebral ganglia (Examples, celiac-superior & inferior mesenteric ganglia
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are anterior to the vertebrae and close to large abdominal arteries, are sympathetic and innervate organs below the diaphragm mainly
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Terminal (intramural) ganglia (Examples, ciliary-otic-submandibular ganglia)
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located at the end of the motor pathway close to or within the wall of a visceral organ (long fibers), these are parasympathic.
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Postganglionic neurons
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1. One sympathetic preganglionic fiber may synapse with 20 or more postganglionic fibers which typically innervate several visceral effectors. Therefore, sympathetic responses tend to be widespread in the body.
2. One parasympathetic preganglionic fiber will synapse with 4 or 5 postganglionic fibers all of which innervate only one visceral effector. Therefore, parasympathethetic responses tend to be more localized. |
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Cholinergic neurons
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a. They release acetylcholine (ACh) which is quickly inactivated by the enzyme acetylcholinesterase. Therefore their effect is short lived.
b. Cholinergic neurons include the following (1). All preganglionic neurons (2). All parasympathetic postganglionic neurons (3). A few sympathetic postganglionic neurons, such as those to sweat glands. |
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Cholinergic receptors (two types)
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a. Nicotinic receptors
b. Muscarinic receptors |
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Nicotinic receptors
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(1). Occur on dendrites and cell bodies of postganglionic neurons. Are also at motor end plates of the neuromuscular junction.
(2). These receptors cause depolarization and thus excitation of the postganglionic cell. (3). Smoking enhances the effects of ACh on postganglionic neurons. |
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Muscarinic receptors
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(1). Occur on all effectors innervated by parasympathetic postganglionic axons.
(2). Depending on the cell, activation of these receptors can cause depolarization (excitation)or hyperpolarization (inhibition). (3). They also occur on the relatively few types of sympathetic effectors stimulated by ACh E.g., sweat glands). |
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Adrenergic neurons
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a. Release the neurotransmitter norepinephrine (NE, noradrenalin) which is slowly removed so that its effects tend to be longer lasting.
b. Also sympathetic stimulation causes adrenal medulla glands to release NE and epinephrine into the blood. This makes for longer lasting effects. c. Most sympathetic postganglionic neurons are adrenergic. |
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Adrenergic receptors
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a. These occur on visceral effectors innervated by most sympathetic postganglionic neurons.
b. Are two main types - alpha receptors & beta receptors. Some are excitatory and some are inhibitory. c. NE & epinephrine also stimulate these as hormones. d. NE stimulates alpha-receptors more vigorously than beta-receptors but epinephrine stimulates both equally well. |
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Agonist
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- a drug or natural product that binds to and activates a receptor, thus mimicking the effect of its neurotransmitter or hormone.
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Antagonist
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- one that binds to and blocks a receptor, thus preventing the effect. (E.g. Beta blockers used to decrease heart rate, force of contraction, and thus B.P.)
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Sympathetic division
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- stimulates body functions that support vigorous physical activity and rapid ATP production to deal with a stress (fight or flight response).
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Parasympathetic division
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- stimulates body functions that conserve and restore energy (rest and digest response).
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Explain the relationship of the hypothalamus to the autonomic nervous system
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The hypothalamus is the major control and integration center of the ANS. Its output influences autonomic centers in the brain stem and spinal cord
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PNS: Preganglion neurons
Somatic |
Only one neuron
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PNS: Preganglion neurons
Sympathetic |
T1-L2
S2-S4 |
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PNS: Preganglion neurons
Parasympathetic |
Cranial Nerves:III, VII, IX, X
S2 - S4 |
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PNS: Ganglion
Somatic |
none
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PNS: Ganglion
Sympathetic |
Paravertebral & Prevertebral
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PNS: Ganglion
Parasympathetic |
Terminal
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PNS: Postganglion neuron
Somatic |
none
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PNS: Postganglion neuron
Sympathetic |
many connections
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PNS: Postganglion neuron
Parasympathetic |
few connections (localized)
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PNS: Neurotransmitter
Somatic |
Ach (only)
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PNS: Preganglion Neurons
Sympathetic |
Ach
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PNS: Preganglion Neurons
Parasympathetic |
Ach
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PNS: Postganglion Neurons
Sympathetic |
NE some Ach
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PNS: Postganglion Neurons
Parasympathetic |
Ach
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PNS Receptors: Sympathetic
Muscarinic (Ach) |
sweat gland effectors
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PNS Receptors: Parasympathetic
Muscarinic (Ach) |
all effectors
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PNS Receptors: Sympathetic
Nicotinic (Ach) |
Motor EP
All postganglionic neurons |
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PNS Receptors: Parasympathetic
Nicotinic (Ach) |
none
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PNS Receptors: Sympathetic
Adrenergic (NE) |
Most effectors
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PNS Receptors: Parasympathetic
Adrenergic (NE) |
none
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Adrenal Medullae:
Sympathetic Effect |
Epinephrine and norepinephrine secretion
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Adrenal Medullae:
Parasympathetic Effect |
no effect
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Cardiac Muscle:
Sympathetic Effect |
Increase heart rate and force of contraction
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Cardiac Muscle:
Parasympathetic Effect |
Decrease heart rate and force of contration
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Airways:
Sympathetic Effect |
Dialation
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Airways:
Parasympathetic Effect |
Constriction
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Skeletal Muscle:
Sympathetic Effect |
increase blood flow
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Skeletal Muscle:
Parasympathetic Effect |
no effect
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Liver:
Sympathetic Effect |
Glycogenolysis & release of glucose into the blood
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Liver:
Parasympathetic effect |
increase glycogen synthesis
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Adipose Tissue:
Sympathetic Effect |
Lipolysis & release of fatty acids into the blood
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Adipose Tissue:
Parasympathetic effect |
no effect
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GI Tract:
Sympathetic Effect |
decrease blood flow, motility, and secretion
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GI Tract:
Parasympathetic effect |
increase blood flow, motility, and secretion
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Kidneys:
Sympathetic Effect |
decrease blood flow and urine volume
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Kidneys:
Parasympathetic effect |
no effect
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Autonomic nerve neuropathy
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disorder of cranial or spinal nerve that has multiple effects on the autonomic nervous system
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biofeedback
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a technique in which an individual is provided with information regarding an autonomic response such as heart rate, blood pressure, or temperature. Varous electronic monitoring devices provide signals about autonomic responses - by concentrating on positive thoughts individuals learn to alter autonomic responses
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dysautonomia
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inherited disorder in which the autonomic nervous system functions abnormally - reduced tear gland secretions, poor vasomotor control, motor incoordination, skin plotching, absence of pain sensation, difficulty swallowing, hyporeflexia, excessive vomiting, emotional instability
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hyperhydrosis
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excessive or profuse sweating due to increase stimulation of sweat glands
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mass reflex
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in cases of severe spinal cord injury above T6 - stimulation of skin or overfilling of an organ below the level of injury results in intense activation of the autonomic and somatic output from the spinal cord as reflex activity returns
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megacolon
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abnomally large colon - parasympathetic nerves to the distal segment of the colon do not develop properly
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reflex sympathetic dystrophy (RSD)
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syndrome that includes spontaneous pain, painful hypersensitivity to stimuli, excessive coldness and sweating in the involoved body part - due to trauma or surgery - treatment with anesthetics and physical therapy
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Vagotomy
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cutting of the vagus (X) nerve - frequently done to decrease the production of hydrochloric acid in persons with ulcers
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