Neuro week 13 Flashcards
1
Q
Visceral organs are insensitive to ordinary mechanical and thermal stimuli but have
A
- Mechanoreceptors that are sensitive to distensions and
- Chemoreceptors that are sensitive to a variety of chemical substances.
- Both can trigger visceral local or long-loop reflexes.
- Sudden or large magnitude distensions and spasms of muscular walls of viscera or decreased blood supply to the viscera may cause severe pain
2
Q
The forms of pain often distinguished by treatment. Nociceptive pain is commonly treated with
A
Anti-inflammatories, counter-irritants and narcotics if necessary.
3
Q
Hyperalgesia
A
Exaggerated sensitivity to noxious stimuli
4
Q
Pain is a system that
A
Alerts the nervous system to danger.
Perception of pain is not just the cognitive recognition of nociceptive 1° afferent input but it is also a complex blending of various sensory modalities and the affective understanding of the sensory input
5
Q
T / F- The vagus nerve variably innervate atrial muscle so produces only a Variable negative ionotropic effect on atria only. So parasympathetics have only a chronotropic and dromotropic effects with the latter only in the AV node. Therefore only negligible effect of parasympathetic activation on cardiac muscle contractility
A
True
5
Q
Stimulation of parasympathetic innervation originating in spinal cord segments S2-S4 results in .PES
A
- Secretion of vaginal glands,
- Engorgement of the clitoris,
- Penile erection -disruption of parasympathetics can produce erectile dysfunction but there are so many other causes
5
Q
Rate of depolarization of inspiratory neurons in medulla are increased by
A
Central chemoreceptor input (ventral medulla).
Chemoreceptor afferents will further increase the number of neurons activated. The increased rate of depolarization with increased rate of breathing and increased number of neurons activated will increase the depth of ventilation.
Medullary Chemoreceptors are sensitive to elevated H+ in cerebrospinal fluid which was produced by elevated CO2 in blood. Thus increased CO2 in the blood is the trigger for increased ventilatory rate and depth of ventilation.
6
Q
What neurotransmitter is released at preganglionic and post-ganglionic terminals in the parasynpathetic division?
A
ACh
7
Q
In the autonomic ganglion neuron the post-ganglionic axon has varicosities along it that release either of 2 transmitter
A
NE excitatory or ACh inhibitory on the smooth muscle or effector organ upon which it ends.
7
Q
What is Pain?
A
The cognitive recognition of noxious stimuli or injury. .
7
Q
Stimulation of nociceptors produces
A
Acute pain, but can experience both central and peripheral plasticity which can enhance the pain.
8
Q
The Apneustic Center in the caudal pons integrate
A
Afferent & central drives to inspiratory & expiratory UMNs
9
Q
Chronic pain is very different. It has
A
- No clear point of onset and outlasts time expected for tissue healing.
- It may occur with or without tissue damage – so NOT proportional to extent of damage and serves. No protective function.
- It is likely an example of negative neuroplasticity
9
Q
There are two principal proposed mechanisms for pain modulation GD
A
Gate Control theory of pain and
Descending control (formerly called the enkephalinergic modulation of pain)
10
Q
In the Somatic nervous system LMN axon within the CNS produces Acetylcholine and ends directly on skeletal muscle cells in what junction?
A
Neuromuscular junction
10
Q
Sympathetic innervation of the bladder is from
A
Spinal cord segments T11-L2 Via inferior mesenteric & pelvic ganglia.
Sympathetics produces a relaxation of the detrusor and contraction of the internal urethral sphincter, thus preventing the bladder from emptying
11
Q
Sympathetic Prevertebral ganglia comprised of - CSI
A
- Celiac
- Superior mesenteric ganglia
- Inferior mesenteric ganglia
12
Q
Control of ventilation is accomplished by a network of complex circuitry, mostly in the medulla. There are visceral afferents from the
A
Carotid and aortic chemoreceptors via CN IX & X which help in this regulation. Output to somatic lower motor neurons which contact the skeletal muscle of the diaphragm and accessory ventilatory muscles
13
Q
T / F Both somatic and autonomic systems Increase/Decreased activity of their target tissues
A
True
14
Q
What type of effect does the autonomic nervous system neurotransmitter have?
A
- Both excitatory & inhibitory effects on their target tissues depending upon the type of transmitter and receptor.
15
Q
Signs of ectopic pain
A
- Positive Tinel’s sign over an unusual area of nerve.
- Positive Tinel’s sign from only light tapping over an area of inflammation can produce severe pain
16
Q
Similarity of Somatic & Autonomic system
A
Both have conscious and unconscious components but they differ in the magnitude of conscious and unconscious control over them
Both systems function in volitional activities – activity requires changes in both somatic and autonomic system .
17
Q
Differences in the somatic and autonomic systems- Major brain structures that receives afferent information-
A
- Thalamus & cerebral cortex -somatic afferents
- Hypothalamus- autonomic afferents
- Key upper regulatory centers
18
Q
Control of ventilation is a function of which system?
A
Automatic (non-voluntary) function but NOT autonomic
18
Pain has a very important role in preparing the body for response to injury including both
somatic & autonomic responses. In addition we can modulate the pain with descending modulation of this input
18
Paleospinothalamic component
Sometimes referred to as the (Paramedial ascending system-PAS) involves neurons actived by the unmyelinated C primary afferent fibers. These ascending pathways initially rising in the lateral spinothalamic pathway, projects to brainstem, hypothalamus, midline thalamus & cingulate cortex.
This Paleospinothalamic component Mediates affective slow pain which is the poorly localized, emotional content of pain
19
Autonomic innervation of the heart is both sympathetic and parasympathetic
Sympathetic stimulation
Increases rate & force of contraction from activity in efferent fibers from the upper thoracic segments (T1-T6) Via cervical & upper thoracic ganglia
20
Higher level control of the autonomic nervous system comes from the
Hypothalamus.
Hypothalamic descending supra-spinal projections to:
* Preganglionic sympathetic neurons in T1-L2 via hypo-thalamospinal tract
* Preganglionic parasympathetic neurons in S2-S4
21
Both Noradrenergic & serotonergic pathways inhibit tract cells using primarily _________ Inhibition; Enkephlinergic pathways produce _______ inhibition and GABA inhibitory interneurons which produces\_\_\_\_\_\_\_\_\_ inhibition
Post-synaptic inhibition.
Pre-synaptic inhibition.
Both pre & post-synaptic inhibition
22
Primary afferent released Glutamate (glut) binds to AMPA/KA receptors and produce the
Fast EPSPs seen in post-synaptic neurons.
Primary afferent released Substance P (SP) produces slow EPSPs and also activates 2nd messenger systems in the post-synaptic cells
CFRP & ATP also appear to activate 2nd messenger intracellular systems
24
Common causes of Neuropathic (neurogenic) pain are
Peripheral nerve pathologies – metabolic polyneuropathies or infectious mononeuropathies and Thalamic syndrome, which is abnormal firing of thalamic neurons producing pain as perceived by the cerebral cortex
25
Myofascial Trigger Points
Localized pain point generally in fascial covering of muscle or within muscle and have been related to localized peripheral sensitization and axon reflexes
26
What neurotransmitter is released by the Sympathetic Division CNS preganglionic and postganglionic neurons
* ACh @ preganglionic terminals
* NE @ postganglionic terminal on the target tissue.
* In a sense the Adrenal medulla is a specialized sympathetic ganglion that instead of releasing NE as a transmitter it releases Epinephrine and NE as hormones
27
Neuropathic pain is most commonly treated using
Na+ channel blocking agents such as Gabapentin (NeurontinTM) & Pregabalin (LyricaTM), Carbamazepine & other anti-seizure medications and Lidocaine & other local anesthetics.
28
Inspiratory neurons in medulla stimulate LMNs in spinal segments C3, C4 & C5 and project to the
Diaphragm via the phrenic nerve.
There are also slightly higher threshold inspiratory neurons that when activated will send descending excitatory activation to the LMNs in the cervical and thoracic LMNs that innervate the accessory muscles of inhalation (sternocleidomastoid, traps, intercostals)
0%'\>Bladder to empty
28
Pain can be defined as
nociceptive or neuropathic pain.
28
Several descending systems which have an effect on pain modulation.
Cerebral cortex and hypothalamic projections to midbrain & brainstem activate several nuclei within the brainstem.
* Periaqueductal gray has enkephalinergic neurons which descend either directly to the spinal cord or Descend to control Raphe neurons.
* Locus coeruleus has adrenergic neurons which descend to the spinal cord to release NE
* Raphe nuclei have serotonergic neurons which descend to the spinal cord to release serotonin (5-HT)
29
Peripheral chemoreceptor input via\_\_\_\_\_\_\_\_\_\_\_\_ from ____ and via \_\_\_\_\_\_\_\_\_\_\_\_from\_\_\_\_\_\_\_
CN IX, carotid chemoreceptors, & CN X, from aortic chemo-receptors.
These chemoreceptors are also sensitive to increases in blood levels of H+/CO2 which is the result of increased metabolic activity as in exercise. Peripheral chemoreceptors are responsive to the minute by minute changes in blood levels of H+/CO2 while central chemoreceptors are responsive to long-term resting levels of H+/CO2
29
Nociceptive signals
* Relayed rostrally by the spinothalamic system – specifically by the lateral spinal thalamic tract
* Pain pathway divided into two subdivisions: the neospinothalamic component and the paleospinothalamic component.
30
Pneumotaxic center
Located in rostral pons
Functions as “off-switch” for inspiration- When the Pneumotaxic center is active, it shortens inspiratory duration which aids in the increased inspiratory rate
31
Pain is divided into
Acute and chronic pain.
32
Myelinated afferents (Aδ-fibres) from the bladder are connected to the tension receptors in the bladder wall. These afferents are relayed by neurons in dorsal horn of spinal cord to ascend in the
Dorsolateral funciculus, Relay in thalamus to end in insular cortex to give sensation of bladder “fullness”
33
Gate-control theory states that
Moderate pain stimulation of tactile receptors can block the pain but very severe pain can override this effect
34
Autonomic afferents from the abdominal viscera afferents travel to the sympathetic trunk in the
splanchnic nerves
34
The Gate-control theory involves
Segmental Modulation at level of 1° afferent & relay cell. It begins by realizing that small caliber afferents C-fibers activate 2° neuron (tract cell) to signal pain
34
Following injury, allodynia may develop in an area where there is no apparent peripheral inflammation
Ordinarily painless stimuli are now experienced as painful- result of altered processing of non-nociceptive input to wide, dynamic-range neurons (WDRN)
36
Micturation is controlled by the
Pontine micturation center which is excited by periaqueductal gray which was activated by afferents from bladder.
This Stimulates parasympathetics producing detrusor contraction and Inhibits sympathetics relaxing internal urinary sphincter
37
Thermal nociceptors Respond to i
Intense cold (45°C) and have myelinated (Ad) or unmyelinated (C ) afferent axons
38
In the autonomic nervous system there is a preganglionic neuron in CNS whose “preganglionic” axon ends and innervates cells in the
Peripheral ganglia. The Ganglionic neuron of the peripheral ganglia has a “post-ganglionic” axon which innervates the target tissue
39
Sympathetic Innervation of sinoatrial (SA) & atrioventricular (AV) nodes produce
Positive chronotropic & dromotropic effects-
* Chronotropic effect- increases heart rate
* Dromotropic- Increases rate of conduction through the atria & specialized conduction system of the ventricles
40
Larger Ab fiber activates an inhibitory interneuron to
**B**lock signal of pain by inhibiting the 2° neuron (tract cell). So by stimulating touch or pressure receptors in an area you can block pain from that area. However it is also proposed that Very active C-fibers can use another inhibitory interneuron to block the inhibitory effect of the large caliber afferents
41
More ways to deal with pain
Cold
* Decrease metabolism so decrease release of local inflammatory chemicals
* Counter-irritation to blockage of nerves
Trancutaneous electrical nerve stimulation (TENS) proabably has two effects
* High-frequency, low intensity, electrodes over area of pain – has a counter irritation effect, activating low-threshold Ab fibers that inhibit nociceptive input to spinal cord – the Gate control mechanism
* Low-frequency, high-intensity, electrodes over acupuncture points may elicit release of segmental and descending enkephalins and hormonal endorphins
42
Afferents that originate mostly from unencapsulated and encapsulated receptors in the viscera and walls of blood vessels.
Autonomic afferents
43
How does Parasympathetic activation decrease heart?
Efferent Fibers of Vagus nerve (CN X) innervate SA & AV nodes to produce a decrease in heart rate and speed of conduction through the AV node (Negative chronotropic & dromotropic effects)
43
Polymodal Nociceptors Respond to
* Mechanical
* Thermal or chemical stimuli and have Small unmyelinated (C) afferent axons
44
Strong Relationship between pain to affect & motivation.
What is Affect
What is motivation
Affect- emotional feeling, tone, or mood attached to a thought elicited by conditions and circumstances of internal and external environments and nociceptive sensory input has a large impact on these emotional feeings.
Motivation is the State of need within us that arouses, maintains, and directs behavior toward a goal. And there is nothing more motivating than pain
45
Sympathetic efferents to vasculature produce
Vasocontriction -increase blood pressure.
However the Baroreceptor reflex affferents decreases sympathetic outflow so produces vasodilation. This Vasodilation & decreased heart rate & contractility decreases blood pressure.
46
Peripheral sensitization
Enhanced responsiveness of nociceptors - results when there is an increased sensitivity of nociceptors and primary afferents to noxious stimuli or a responsiveness of these receptors to non-noxious stimuli such as touch.
47
Autonomic afferents from the thoracic viscera afferents travel to the sympathetic trunk in the
Cardiac and pulmonary nerves
48
The basic rhythm of breathing is produced by
Pacemaker like cells within inspiratory center in the Dorsal respiratory group in medulla.
These inspiratory neurons produce Spontaneous depolarization @ about 15/min which is the basic respiratory rate.
The axons from these neurons follow a descending tract to C3-C5 motor neurons. The axons from these lower motor neurons form the phrenic nerve which innervates the diaphragm.
49
Major 1° afferent excitatory transmitters on to central nervous system neurons.
Glutamate (glut) & substance P (SP)
Calcitonin gene related peptide (CFRP) and adenosine triphosphate (ATP) have also been discovered to modulate 1° afferent input
51
Neurotransmitter that produces excitatory end-plate potentials in the skeletal muscle cells, every muscle cell is innervated
Acetylcholine
51
Pre-ganglionic axons are ver\_\_\_\_\_\_ and post-ganglionic axons are very\_\_\_\_\_\_\_\_\_
very short, very long
53
Sympathetic Paravertebral ganglia comprised of
Sympathetic trunk and include the 3 cervical ganglia
54
Acute pain occurs as a result of
Tissue damage.
It has a well-defined onset and duration and is proportional to the magnitude of the injury.
It is Protective in nature
56
T / F-There is also limited Voluntary control of ventilation. Activity from cerebral motor cortex can produce voluntary increase or decrease of ventilatory rate & volumes by stimulating or inhibiting both the inspiratory and expiratory centers of the medulla. In this way you can voluntarily take a deep breath and slowly let it out as in talking or use expiratory neurons to quickly exhale as in blowing out birthday candles or yelling at a high volume.
True
57
Hypothalamic descending supra-spinal projections to Preganglionic parasympathetic brainstem neurons such as: **SED**
* Salivatory nuclei
* Edinger-Westphal nucleus
* Dorsal motor nucleus of X
58
Preganglionic axons of the parasympathetic division end in which ganglion (s)?
**STOP C**
* Submandibular ganglion
* Terminal ganglia within the walls of the gastrointestinal tract, urinary bladder and erectile tissues
* Otic ganglion
* Ptergopalatine ganglion
* Ciliary ganglion
59
Parasympathetic innervation of the bladder originates from
Spinal intermediate gray of S2-S4 which causes contraction of the detrusor and emptying of the bladder
60
Which dominates in the sympathetic division, convergance or divergence?
Divergence - with ratio of preganglionic to postganglionic fibers 1:10–1:196 so with between 10 and 200 ganglion cells innervated by a single pre-ganglionic neuron
61
1° nociceptive afferents synapse on neurons in the dorsal horn of the spinal cord, specifically in:
* Posteriomarginal nucleus
* Substantia gelatinosa
* Base of dorsal horn (lamina V)
* Some in ventral horn
63
Two pontine centers that help regulate ventilation. The PA
* Pneumotaxic center
* Apneustic center
64
Visceral sensations are described as
Vague, poorly localized, and affective visceral sensations such as Hunger, heartburn, nausea.
65
Autonomic afferents from the pelvic viscera afferents travel to the sympathetic trunk in the
Lower thoracic and upper lumbar spinal nerves
66
Mechanical nociceptors respond to
Intense mechanical stimuli and have small myelinated (Ad) afferent axons
67
Neospinothalamic component
Composed of neurons innervated by Ad afferent fibers.
Signals travel to VPL of the thalamus via anterolateral pathway (spinothalamic) & to 1° somatosensory cortex
This Mediates fast pain – sharp, well-localized, rapidly perceived pain
69
Enduring, aching, intense pain
Mediated by C-fibers.
Paleospinothalamic component of pain pathways and is associated with the affective & emotional nature of pain
70
Most severe forms of nerve pain
Ectopic pain- activity along nociceptive afferents from site of damage not nerve terminal. Results from a denuded axon which can lead to an accumulation of Na+ channels in that denuded area. This gives rise to an excitable area of axon.
71
Types of nocioceptive receptors
* Mechanical
* Thermal
* Chemical or
* all of these (polymodal)
73
sympathetic Innervation of atrial & ventricular cardiac muscle produces
Positive ionotropic effect to both atria and ventricles (increased force of contraction)
75
Cortical areas also active during micturation include: **SPAIn**
* Supplemental motor area
* Prefrontal cortex
* Anterior cingulate gyrus
* Insula
76
Chemically sensitive Nociceptors Respond to
* Ions (K+ & H+)
* local inflammation mediators (histamine) &
* Other chemicals (capsaicin) and have Small unmyelinated (C) afferent axons
77
There is also autonomic innervation of the sex organs.
Stimulation of sympathetic innervation arising from spinal cord segments T10-L2 results in
Vaginal contraction and Penile ejaculation. Contraction of the internal urinary sphincter prevents retrograde emission of semen into bladder.
78
Complex Regional Pain Syndrome results from
Peripheral sensitization
79
One difference is the CNS effector neuron connection to target tissue.
* In the Somatic nervous system– LMN directly connected to skeletal muscle cells but in
* Autonomic Nervous system– CNS effector neurons connected to ganglia which connect to target tissue
81
Allodynia
Normally innocuous stimuli evokes the perception of pain
82
There are expiratory UMNs in the medulla which are normally unexcited. When Inspiratory neurons in medulla are activated they inhibit expiratory UMNs in the medulla. When relatively few inspiratory neurons are activated there is relatively little inhibition of these expiratory interneurons.
So under these circumstances the expiratory neurons membrane potential returns to resting following the release from inhibiiton. However with very high levels of inspiratory UMN activity, there is a dramatic inhibition of these expiratory UMNs. Once that inhibition ends there is a large Disinhibitatory rebound that produces excitation of these expiratory UMNs and they produce active exhalation by exciting LMNs in the thoracic spinal cord which innervate the muscles of exhalation (abdominals & intercostals). Remember during restful inhalation, there is not much inhibition of these expiratory UMNs so they do not become active and that is why there is normally passive exhalation during restful inhalation.
84
Autonomic afferents from High pressure baroreceptors in carotid sinus & aorta come to the brainstem via
CN IX (glossopharyngeal) & CN X (vagus) from the baroreceptors in carotid sinus & aorta respectively
85
The neurons in lamina V that receive both nociceptive and low-threshold touch (Ab) input are referred to as
Wide Dynamic-range neurons (WDRNs)
86
Autonomic afferents from thoracic and abdominal viscera reach spinal cord via the
sympathetic trunks and brainstem via the glossopharyngeal (CN IX) and vagus (CN X) nerves
88
Most visceral afferents are (type of fiber)
“C” fiber afferents so burning & pressure sensations are the most common symptoms.
89
The Parasympathetic Division is the
Craniosacral division with its CNS preganglionic neurons in cranial nerve nuclei (Edinger-Westphal nucleus, superior & Inferior salivatory nuclei, Dorsal Motor Nucleus of X) and sacral spinal cord segments (S2-S4) intermediate cell column. The ganglia are located close to the target organ they innervate so there are very long pre-ganglionic fibers and short post-ganglionic fibers. There is very little divergence & convergence. Ratio of preganglionic to postganglionic fibers 1:3 – very little divergence.
90
In addition to the descending neural pathways and the gate control mechanism, there are two other pain modulation systems.
* The Hormonal system
* Additional system
91
General functions of the autonomic nervous system include:
* Regulation and control of visceral activities that maintain a stable internal environment in response to changing internal conditions and external stresses
* Sympathetic system is generally catabolic, prepares for “fight or flight”
* Parasympathetic is anabolic, conserves energy, and promotes the maintenance, and restoration of bodily reserves and is nicknamed either “feed and breed” or “rest and digest”
92
Pontine micturation center also Inhibits motor neurons causing
relaxation of the external urinary sphincter which allows the bladder to empty
93
Nociceptors
Unencapsulated endings categorized by the environmental stimulus to which they respond:
94
Local release of sensitizing agents may produce axon reflexes where
Antidromic impulses from 1° afferent will cause the release of substance P at distal ending producing inflammation
95
GABA produces both
pre-synaptic and post-synaptic inhibition at primary afferent terminals and Serotonin (5-HT) & enkephalins (ENK) also can produce post-synaptic inhibition
96
Hormone system involves the release of
b-endorphin -released as part of the pro-hormone proopiomelanocortin (POMC) from the pituitary during ***stress and injury.***
Endorphins also act on spinal & other opioid receptors to block pain.
Adrenocorticotropic hormone (ACTH) the anti-inflammatory associated hormone is also released as part of POMC.
endogenous morphine like substance that relieves pain.
97
Afferents from baroreceptors relay in solitary nucleus to
Inhibit cardiac acceleratory center & excite cardiac inhibitory center. In this way these afferents Inhibit sympathetics & stimulate parasympathetics
99
Somatic innervation of external urinary sphincter originates from
S2-S3 (Onuf’s nucleus – S2) and travels to the pelvic floor muscles Via pudendal nerve. These lower motor neuronal axons Innervate the external urinary sphincter (part of pelvic floor muscles) to voluntarily prevent micturation until convenient to urinate
100
Other pain modulating system- the Endogenous cannabinoids.
Brainstem neurons release a polypeptide that mimics the action of tetrahydrocannabinoid (THC) the active ingredient in marijuana.
This system appears to separate emotional component from discriminative component of pain so when you smoke marijuana you can feel and localize the pain but it does not have the same emotional impact.
101
Complex Regional Pain Syndrome (CRPS)
Severe chronic musculoskeletal pain syndrome commonly seen in the extremities where non-nociceptive stimulation causes pain. CRPS comes in 2 forms:
* Type 1 – not associated with demonstrable nerve lesions – formerly called reflex sympathetic dystrophy (RSD)
* Type 2 – associated with nerve lesions formerly called causalgia
102
Neuropathic (neurogenic) pain signals the presence of
Nervous system pathology in the absence of peripheral receptor activation – most commonly damage to peripheral nerves or the central nociceptive pathways
103
Sympathetic Division
* Thoracolumbar division with its CNS effector “pre-ganglionic” neurons located in lateral horn (intermediolateral cell column) of thoracic & upper lumbar spinal cord.
* Ganglia located either immediatedly lateral to the spinal cord and vertebral column paravertebral ganglia or some distance from the spinal cord prevertebral ganglia.
105
Motor neurons in the Somatic nervous system are
Excitatory only - decreased excitation (inhibition) of the skeletal muscle is causes by decreased motor neuronal activity
106
Nociceptive pain
* Due to activation of peripheral receptors in response to tissue injury and inflammation.
107
Double pain phenomenon
Because of the two calibers of nociceptive afferent fibers- studied it by dropping hot metal on each other.
Characterized by sharp, stabbing pain followed by burning & aching sensation.
Sharp stabbing pain or Fast (1st) pain arises from Ad fiber 1° afferent, small myelinated fibers.
Achy burning pain or Slow (2nd) pain arises from the C fiber 1° afferent, the unmyelinated fibers.
108
What is fast pain?
Sharp, stabbing, knife-like sensation that is initially felt and mediated by Ad fibers of the Neospinothalamic component of the pain pathways.
These fibers also mediate temperature, and non-discriminatie touch and gives us the quick reflexes from segmental action and the ascending Localized discriminative nature of pain sensation.
110
Pain is generally conceptualized as one somatosensory modality. In this conceptualization we have the Classifications of n
“fast” & “slow” pain.
111
Spinal cord connections
* Axon ending on neurons in the Postero-marginal nucleus & lamina V are Ad afferents
* Neurons in all areas receive input from C fibers
112
Pontine storage center excites
Onuf’s nucleus producing closure of external urinary sphincter so decreased urination
113
Peripheral sensitization can be produced by the local release of sensitization agents from mast cells such as:
* Prostaglandins
* Bradykinin
* Histamine
* Serotonin (5-HT)
114
Both Autonomic and Somatic nervous systems have
* Specialized afferent and efferent fibers
* Lower regulatory nuclei that receive afferent input
* Efferent output Peripheral systems which they control or regulate
* Connections with higher centers of the CNS by ascending and descending pathways
115
Ways to deal with pain.
* Touch and massage may Increase local blood circulation to decrease local inflammatory agents and may activate low-threshold Ab fibers that inhibit nociceptive input to spinal cord– the Gate control mechanism
* Heat may increase local circulation to decrease local inflammatory agents but may also be a counter-irritation and also activate low-threshold Ab fibers that inhibit nociceptive input to spinal cord – the Gate control mechanism
116
Suggested mechanism involves inputs to
involves inputs to wide, dynamic-range neurons. Normally input to WDR neurons through AMPA receptors from Ab afferents is minimal. And Normally NMDA receptors for glutamate are blocked by the action of Mg++ ion
When activity of nociceptors is elevated and/or prolonged the Mg++ ion blockage is removed
With the activation of both AMPA & NMDA receptors, the non-nociceptive Ab fibers now activate pain
Ordinarily painless stimuli are experienced as painful. You can see that this is a negative from of synaptic plasticity that has resulted in the altered processing of non-nociceptive input to wide, dynamic-range neurons (WDRN) with the result of pain now arising from non-nociceptive stimuli
117
The sympathetic division has a Great deal of convergence & divergence between
pre-ganglionic & postganglionic neurons.
118
Visceral and somatic afferents converge on common spinal cord neurons with referral of visceral pain to the
somatic region
There are a variety of referral zones for input from visceral organs for visceral sensations
