General Senses Flashcards
are widely distributed across various parts of the body and are categorized as either Somatic or Visceral.
General Senses
B. Visceral Senses contain:
- Pain
- Pressure
I. Somatosensory System
General Senses:
- Light touch or tactile discrimination
- Pressure
- Touch
- Pain
- Temperature
- Limb position
A. Somatic Senses contains:
- Touch
- Pressure
- Proprioception (sense of body position)
- Temperature
- Pain
I. Somatosensory System
Receptors:
- Meissner’s corpuscles
- Hair follicle nerve ending
- Merkel’s tactile disc
- Pacinian corpuscle
- Krause end
- Ruffini’s nerve ending
- Free nerve
- Muscle spindle
- Golgi tendon organ (Tendon spindle)
receptor for Light touch
- Meissner’s corpuscles
- Hair follicle nerve ending
receptors for Touch
Merkel’s tactile disc
receptors for Pressure
Pacinian corpuscle
receptors for Heat/warmth
Ruffini’s nerve ending
receptors for Cold
Krause end
receptors for Pain
Free nerve
receptors for Proprioception
- Muscle spindle
- Golgi tendon organ (Tendon spindle)
General Sense Pathways:
- First-order neuron (N1)
- Second-order neuron (N2)
- Third-order neuron (N3)
Sensory neuron that receives the initial
stimulus.
First-order neuron (N1)
Association neuron.
Second-order neuron (N2)
Transmits sensory information to the cortex.
Third-order neuron (N3)
Ascending Fiber Tracts :
- Anterolateral System
- Pathways to the Cerebellum
- Cuneocerebellar Tract
- Posterior Column
Anterolateral System :
➢ Lateral Spinothalamic Tract
➢ Anterior Spinothalamic Tract
For pain and temperature (except head).
Lateral Spinothalamic Tract
Crude touch or light touch (except head).
Anterior Spinothalamic Tract
Pathways to the Cerebellum :
➢ Posterior Spinocerebellar Tract
➢ Anterior Spinocerebellar Tract
Unconscious proprioception from lower limbs.
Posterior Spinocerebellar Tract
Unconscious proprioception from lower limbs.
Anterior Spinocerebellar Tract
Unconscious proprioception from the upper body.
Cuneocerebellar Tract
For conscious proprioception, deep pressure, and discriminative touch.
- Gracile fasciculus – Lower extremities.
- Cuneate fasciculus – Upper extremities.
Posterior Column (Dorsal Column)
Pain and Temperature Pathway
Pathway: ?
Receptors: ?
Pathway: Lateral Spinothalamic Tract
Receptors: Free nerve endings, Krause end bulb, Ruffini’s corpuscle
Pain and Temperature Pathway
N1 - ?
N2 - ?
N3 - ?
o N1 - Dorsal Root Ganglion
o N2 - Dorsal horn cells (spinal cord), axons cross to the opposite side and ascend.
o N3 - Ventroposterolateral nucleus (thalamus), terminating in Brodmann’s area 3,1,2 in the post-central gyrus (opposite side of
the receptor).
Discriminative Touch, Deep Pressure, and Proprioception Pathway
N1 - ?
N2 - ?
N3 - ?
o N1 - Dorsal Root Ganglion; fibers ascend as fasciculus gracilis or fasciculus cuneatus.
o N2 - Synapse in nucleus gracilis or cuneatus, cross at the medial lemniscus.
o N3 - Ventroposterolateral nucleus of the thalamus, ending in Brodmann’s area 3,1,2.
Crude Touch Pathway (Light Touch, Pressure)
N1 - ?
N2 - ?
N3 - ?
o N1 - Dorsal Root Ganglion
o N2 - Laminae VI, VII, VIII; fibers cross to the opposite side.
o N3 - Ventroposterolateral nucleus of the thalamus, ending in Brodmann’s area 3,1,2.
Crude Touch Pathway (Light Touch, Pressure)
Pathway: ?
Receptors: ?
- Pathway: Ventral/Anterior Spinothalamic Tract
- Receptors: Meissner’s corpuscle, Merkel’s disc, Hair follicle nerve ending
Discriminative Touch, Deep Pressure, and Proprioception Pathway
Pathway: ?
Receptors: ?
- Pathway: Dorsal Column/Medial Lemniscal System
- Receptors: Pacinian corpuscle, Meissner’s corpuscle, Muscle spindles, Tendon spindles
Clinical Signs of Injury to the Lemniscal Pathway :
- Inability to recognize limb position
- Astereognosia
- Loss of vibration sense
- Loss of two-point discrimination
- Positive Romberg’s Sign
– Inability to identify objects by touch
Astereognosia
– Increased body sway with eyes closed
Positive Romberg’s Sign
Lower extremity group proprioception
Anterior Spinocerebellar Tract
Unconscious Proprioception Pathways :
- Anterior Spinocerebellar Tract
- Posterior Spinocerebellar Tract
- Cuneocerebellar Tract
Individual muscle proprioception in lower extremities
Posterior Spinocerebellar Tract
Upper extremity muscle proprioception
Cuneocerebellar Tract
Controls skilled voluntary movements.
Pyramidal System
Pyramidal System Pathways:
- Corticospinal Tract
- Corticobulbar Tract
➢ Origin: Primary motor cortex (Brodmann’s areas 4, 6).
➢ 90% of fibers cross in the medulla to form the Lateral Corticospinal Tract.
Corticospinal Tract
Clinical Correlations :
- Upper Motor Neuron Lesions
- Lower Motor Neuron Lesions
➢ Origin: Brodmann’s areas 4 and 8.
➢ Terminates at motor nuclei in the brainstem, supplying cranial nerves.
Corticobulbar Tract
➢ Spastic paralysis, hyperreflexia, positive Babinski sign.
Upper Motor Neuron Lesions
➢ Flaccid paralysis, hyporeflexia, muscle atrophy, and positive fasciculations.
Lower Motor Neuron Lesions
- Coordinates movements and postural adjustments.
Functions:
* Smooth movement coordination with the pyramidal system.
* Control of automatic actions (e.g., smiling).
* Postural and muscle tone adjustments.
Extrapyramidal System
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