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Questions and Answers
Pain forces the person to rest or to minimize ______ thus enabling rapid healing of injured part.
Pain forces the person to rest or to minimize ______ thus enabling rapid healing of injured part.
activities
Pain urges the person to take the required ______ to prevent major damage.
Pain urges the person to take the required ______ to prevent major damage.
treatment
When a person feels pain, it may indicate that there is an ______ that needs attention.
When a person feels pain, it may indicate that there is an ______ that needs attention.
injury
Effective management of pain often leads to improved ______ outcomes for the injured area.
Effective management of pain often leads to improved ______ outcomes for the injured area.
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Pain serves as an important ______ system, prompting individuals to take action.
Pain serves as an important ______ system, prompting individuals to take action.
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The neospinothalamic pathway is responsible for fast pain and thermal sensation, especially ______.
The neospinothalamic pathway is responsible for fast pain and thermal sensation, especially ______.
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The first order neuron of the neospinothalamic pathway is located in the ______ root ganglia.
The first order neuron of the neospinothalamic pathway is located in the ______ root ganglia.
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The axons of the second order neurons in the neospinothalamic pathway cross to the opposite side in front of the ______ canal.
The axons of the second order neurons in the neospinothalamic pathway cross to the opposite side in front of the ______ canal.
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The axons of the second order neurons ascend in the lateral column of the spinal cord, forming the ______ lemniscus.
The axons of the second order neurons ascend in the lateral column of the spinal cord, forming the ______ lemniscus.
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The third order neurons of pain pathways are predominantly found in the ______ nuclei.
The third order neurons of pain pathways are predominantly found in the ______ nuclei.
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Study Notes
Sensations
- Sensations are categorized physiologically into somatic and special senses.
- Somatic sensations include pain, temperature, and mechanoreceptive (touch, crude touch, fine touch, tactile localization, tactile discrimination, deep touch, pressure, vibration, tickling, itching, stereognosis).
- Special senses include vision, hearing, smell (olfaction), and taste.
- Organic sensations include thirst, hunger, and sexual desire.
Sensory Fibers of Trigeminal Nerve
- The trigeminal nerve (Cr-V) transmits somatosensory information from the face, teeth, oral cavity, nasal cavity, and scalp to the sensory cortex.
- It also carries proprioceptive input from extrinsic eye muscles.
- Sensory fibers originate from the trigeminal ganglion.
- Three divisions of the trigeminal nerve are ophthalmic, maxillary, and mandibular.
- Sensory fibers terminate in the primary sensory nucleus and spinal nucleus of the trigeminal nerve, as well as the mesencephalic nucleus.
Central Connections
- Fibers from the primary and spinal nuclei of the trigeminal nerve ascend as the trigeminal lemniscus to the ventral posteromedial nucleus of the thalamus (opposite side).
- Some fibers terminate on the thalamic nucleus (same side).
- Thalamic fibers project to somatosensory areas of the cerebral cortex, relaying touch, pressure, pain, and temperature sensations.
- Fibers from the mesencephalic nucleus form the trigeminocerebellar tract, conveying proprioceptive impulses from facial, masticatory, and ocular muscles.
Pain
- Pain is an unpleasant sensory experience associated with actual or potential tissue damage. It serves as a protective mechanism.
- Pain transduction involves nociceptors, opening ion channels, activating enzymes, and releasing chemicals (like bradykinin).
- Pain receptors (nociceptors) are "free nerve endings" of Aδ and C fibers.
- Pain types include cutaneous, deep, visceral, and neuropathic.
Types of Pain Receptors
- Mechanical pain receptors respond to mechanical stimuli.
- Thermal pain receptors respond to temperature extremes.
- Chemical pain receptors respond to chemicals like HCL.
- Polymodal pain receptors respond to all types of stimuli.
Pathways of Pain Sensation
- Two main pathways for pain are the paleospinothalamic pathway (slow pain) and the neospinothalamic pathway (fast pain).
- The paleospinothalamic pathway transmits information to the medial (non-specific) part of the thalamus and limbic cortex (e.g., cingulate gyrus).
- The neospinothalamic pathway transmits information to the lateral part of the thalamus and somatic sensory area I.
Referred Pain
- It's a painful sensation perceived at a site other than the injured tissue.
- Pain arises from viscera, often spreading to a specific area of skin associated with that same dermatome.
- The convergence-projection theory suggests that afferent fibers from the affected viscus and skin converge on the same neuron in the posterior horn and then project pain to the same cortical area as the skin.
Deep reflexes
- Deep reflexes are based on the dynamic stretch reflex.
- Stimulus results in a sudden stretch of a muscle.
- Sensory receptors (nuclear bag fibers) send afferent signals.
- Motor response leads to muscle contraction.
- Reflexes can be tested using a reflex hammer on specific tendon sites (e.g., biceps, triceps, knee, ankle).
- The tested reflex is graded based on the result.
- Jendrassik's maneuver and clenching strengthen weak reflexes to examine muscle tone.
Important Tendon Jerks
- Biceps reflex: Elbow flexed 120 degrees, examiner's thumb on biceps tendon.
- Triceps reflex: Elbow flexed 90 degrees, hammer striking triceps tendon above olecranon.
- Knee jerk: Subject's knees semiflexed, hammer striking patellar tendon below patella.
- Ankle jerk: Foot slightly dorsiflexed, striking Achilles tendon.
- Jaw jerk: Examiner's finger on relaxed jaw, tapping finger.
Pupillary Light Reflex (LR)
- Direct reflex: Pupil constriction when light shines on the eye.
- Indirect (consensual) reflex: Pupil constriction in the other eye.
- Dissociation (LND): Pupils don't constrict in response to light but do constrict during accommodation.
- Adie's tonic pupil: Large pupil, unresponsive to light, but reactive to accommodation.
Cornea Reflex
- Steps involve touching the cornea and observing the blink response for assessment of corneal response and involvement of the facial or trigeminal nerves.
Color Vision
- Color vision is based on cone cells that respond to different wavelengths of light.
- Three main types of cones (red, green, blue) combine to create a wide spectrum of colors.
- Color blindness is a condition with varying degrees of dysfunction that affects the ability to distinguish between different colors.
- Ishihara plates are used as a simple test for color blindness.
Visual Acuity
- Visual acuity is the ability to discern details of objects measured in relation to the visual angle and stimulated cones.
- Factors affecting visual acuity include illumination, contrast, pupil constriction, the density of cones in the fovea, and refractive errors.
- Visual acuity is measured using charting (e.g., Snellen chart).
Visual Field
- Visual field is the area visible to an eye, determined by testing ranges.
- Examination method and findings guide diagnosis of lesions like retinal detachment or retinitis pigmentosa.
- The visual field is tested under different conditions (e.g., with colors) to assess the function of specific parts of the visual pathways.
Deafness
- Deafness is the impaired ability to receive auditory signals from the external environment to the central auditory pathways.
- Types include conductive deafness (impaired sound conduction through the outer and middle ear) and sensorineural deafness (damage to the inner ear or auditory nerve).
- Common causes of conductive deafness include excess earwax, otitis media, otosclerosis, and perforated eardrums.
- Sensorineural deafness causes include noise exposure, lesions of the organ of Corti, and tumors compressing the cochlear nerve.
- Tuning fork tests (Weber and Rinne) differentiate between conductive and sensorineural hearing loss.
- Audiometry is a comprehensive test to measure hearing sensitivity across different frequencies.
Additional notes
- A detailed description of the different types of senses and reflexes is available.
- The provided material covers many biological systems and their functionality.
- This should assist students with study notes for their biology lectures and tests.
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Description
Explore the fascinating world of sensations, distinguishing between somatic and special senses. Learn about the trigeminal nerve, its divisions, and its role in transmitting sensory information from the face and head to the brain. This quiz will test your understanding of how our body perceives pain, temperature, and more.
