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241

- Slow pain
- Polymodal nociceptors (high-intensity persisting mechanical, thermal or chemical stimuli)
- C fiber (group IV)
- Peripheral fibers terminate in the spinal cord almost entirely in laminae II and III of the dorsal horns, which together are called the substantia gelatinosa
- Enters mainly lamina V, also in the dorsal horn
- Join the fibers from the fast pain pathway, passing first through the anterior commissure to the opposite side of the cord, then upward to the brain in the anterolateral pathway

Paleospinothalamic tract

242

- Loss of sensation and motor function paralysis and ataxia caused by the lateral hemisection (cutting) of the spinal cord
- Pain, temperature sensations lost on the opposite side of the body(Spinothalamic pathway)
- Kinesthetic, position, vibration, discrete localization and two-point discrimination lost on the side of the transection (Dorsal column)
- Crude touch retained

Brown Sequard syndrome

243

- Chronic disease of the spinal cord characterized by the presence of fluid-filled cavities and leading to spasticity and sensory disturbances
- Generally in the cervical region, with resulting neurologic defects; thoracic scoliosis is often present

Syringomyelia

244

Parenchymatous neurosyphilis marked by degeneration of the posterior columns and posterior roots and ganglion of the spinal cord

Manifestations
- muscular incoordination
- paroxysms of intense pain
- visceral crises
- disturbances of sensation
- Trophic disturbances, especially of bones and joints(tabes-wasting)

Tabes dorsalis

245

- Selective suppression of pain without effects on consciousness or other sensations
- Descending pathways selectively inhibit the transmission of information originating in nociceptors -> release certain endogenous opioids -> inhibit the propagation of input through the higher levels of the pain system e.g. morphine

Analgesia

246

- “Transmission” – turns on gate for pain
- “Inhibitory” cells –shut the gate
- Perception of pain is subject to modulation

Gating Theory of Pain modulation

247

Analgesia system: Pain suppression in the brain and spinal cord

-- Periaqueductal gray and periventricular area of mesencephalon and upper pons
-- Raphe magnus nuclei, nucleus reticullaris pargigantocellular
-- Dorsal horn of SC – pain inhibitory complex
-- Stimulation of higher brain centers that suppress periaqueductal gray area can also suppress pain:
- Periventricular nuclei in the hypothalamus
-Medial forebrain bundle
-- Transmitters involved in the Analgesia system:
- Enkephalin – presynaptic and postsynaptic inhibition of type Adelta and C fibers
- Serotonin

248

- painful site itself or the nerves leading from it are stimulated by electrodes placed on the of the skin
- stimulation of non-pain, low threshold afferent fibers (touch receptor fibers) leads to the inhibition of neurons in the pain pathways

Transcutaneous Electric Nerve Stimulation (TENS)

249

- Needles are introduced into specific parts of the body to stimulate afferent fibers, and this causes analgesia
- Endogenous opioid neurotransmitters are involved in acupuncture analgesia

Acupuncture

250

Analgesic drugs

Aspirin - inhibits the synthesis of prostaglandins and slows the transmission of pain signals from the site of injury

Opiates (endogenous opioids: endorphins & enkephalins) - act directly on opioid receptors in the brain, which activate descending pathways that inhibit incoming pain signals

251

Sensory Pathways for Pain

- Paleospinothalamic tract
- Neospinothalamic tract

252

Most important Opiate-like substances - stimulate inhibitory neuron so that pain will be less
- Met and leu-enkephalin
- β-endorphin
- Dynorphin

Opiate system

253

- portion of anterior end of diencephalon that lies below the hypothalamic sulcus and in front of the interpeduncular nuclei
- divided into a variety of nuclei and nuclear areas
- links the nervous system to the endocrine system via the pituitary gland

Hypothalamus

254

• portion of anterior end of diencephalon that lies below the hypothalamic sulcus and in front of the interpeduncular nuclei
• divided into a variety of nuclei and nuclear areas
• links the nervous system to the endocrine system via the pituitary gland

Hypothalamus

255

Important Functions of the Hypothalamus

• Endocrine Functions
• Autonomic Functions
• Limbic Functions

256

___ hypothalamus increase BP and HR

posterior and lateral

257

part of hypothalamus that decreases BP and HR

preoptic area

258

- hypothalamus controls the set-point of human body temperature
- controlled by neurons in the preoptic area
- signal appropriate cells to activate body temperature-lowering or temper-ature-elevating mechanisms

Body Temperature Regulation

259

thirst center of the hypothalamus is the __

lateral hypothalamus

260

__ release antidiuretic hormone (ADH) into posterior pituitary; controls urinary excretion of water; acts on cortical collecting duct of the kidneys to cause water reabsorption

magnocellular cells in supraoptic nuclei

261

(hypothalamus)
___ release OXYTOCIN causes contraction of the smooth mus-cle of the uterus and milk let down

magnocellular cells in paraventricular nuclei

262

(hypothalamus)
______ is responsible for hunger; lesions result in starvation; inhibited by leptin

lateral hypothalamus

263

(hypothalamus)
___ is the satiety center; activity produces a “stop eating” signal; lesions cause uncontrolled voracious appetite; stimulated by leptin

ventromedial nucleus

264

(hypothalamus)
__ are involved in reflexes related to food intake like lip licking and swallowing

mamillary nuclei

265

- hypothalamus elaborates releasing and inhibitory factors that modulate ante-rior pituitary function
- subserved by periventricular zone, ar-cuate nucleus and ventromedial nucle-us

Anterior Pituitary Gland Regulation

266

Hypothalamus is the __________ of autonomic nervous system; stimulation of the hypothalamus produces autonomic responses

head ganglion

267

Autonomic Functions of the Hypothalamus

sympathetic: posterior hypothalamus - has a warming function

parasympathetic: anterior hypothalamus - has a cooling function

268

• stimulation of hypothalamus affects behavioral control functions

Limbic Functions of the Hypothalamus

269

__ hypothalamus causes increased general level of activity leading to rage and aggression

lateral

270

(hypothalamus)
__ causes sense of tranquility, pleasure and reward

ventromedial nucleus