Lecture 4 Sensory Systems Flashcards
(29 cards)
What are the three types of neurons involved in the sensory pathway?
- Primary Sensory Neuron (cell body outside of CNS, somatic sensory receptor)
- Secondary Sensory Neuron (Cell body in Dorsal Horn of Spinal cord or brainstem nucleus. ALWAYS DECUSSATES. Projects to controlateral thalamus)
- Tertiatry Sensory Neuron (in the thalamus that projects to the Primary Sensory Cortex via internal capsule)
What does dermatome mean?
A region of skin innervated by the sensory component of a mixed spinal nerve
What are primary sensory neurons responsible for?
Sensory Reception (somatic sensation)
Where are the cell bodies of primary sensory neurons? Where do they project to?
Dorsal Root Ganglia (outside of the CNS)
- project to the Dorsal roots in the dorsal horns of the grey matter
Which sensory receptor is responsible for Fine Touch?
Merkel’s Disk
Meissner’s corpuscle
Which sensory receptor is responsible for Pain and temperature?
Free nerve endings
What sensory receptor is responsible for Crude touch?
Pacinian Corpuscles
What sensory receptor is responsible for joint positioning?
Ruffini’s endings
What is two point discrimination
Test to discern two closely placed sharp stimulus points on the skin
Which area of the skin has the greatest sensory acuity to touch?
Fingers tips and lips
What is unique about the areas of the body with the greatest sensory acuity for touch?
- High densities of fine touch receptors
- Receptors have smaller receptive fields
- Larger areas of sensory cortex for processing
What two pathways can the ascending sensory tracts be divided into?
- Antero-Lateral System
- Dorsal Column system
What two tracts make up the Antero-Lateral System?
- Spinothalamic Tracts (Pain, Temp, Crude touch) (travels from the spine to the thalamus)
- Spinocerebellar Tracts (Unconscious Proprioception) (travels from the spine to the cerebellum)
What two tracts make up the dorsal column system? What is the purpose of the dorsal column?
- Fasciculus Gracilis (Lowerback) (Gracilis = lean)
- Fasciculus Cuneatus (upper back) (Cuneatus = wedge like)
(Dorsal columns transmit fine touch, conscious proprioception)
In the spinothalamic tracts, how are they divided?
Anterior Spinothalamic tract = crude touch
Lateral Spinothalamic tract = pain and temperature
What is the anterior spinothalamic tract responsible for?
- Crude touch
What is the lateral spinothalamic tract responsible for?
- Pain and temperature sensation
For the anterior and lateral spinothalamic tracts, where do the secondary sensory neurons decussate?
- Decussation in the Anterior white commissure of the spinal cord near the level of entry
- Travel up the contralateral spinothalamic tract
Where do the primary sensory neurons synapse to the secondary sensory neurons in the Lateral Spinothalamic tract?
- Substantia Gelatinosa (Dorsal Horn)
Decussation through the grey matter
When the spinothalamic tract reaches the brain stem, what is the new name for it?
- Spinal Lemniscus
Where does conscious proprioception input originate from?
- Muscle Spindles (Muscle stretch)
- Golgi Tendon Organs (Muscle tension)
- Joint Receptors (Position of Joints)
How do axons of the dorsal column travel up the spinal cord?
Ipsilaterally
Which type of neurons travel ispilaterally up the dorsal column?
Primary sensory neurons
From the Dorsal Column, where do axons synapse with secondary sensory neurons?
- Travel ipsilaterally up the dorsal spinal column,
- Synapse in the Medulla at the nucleus Cuneatus/gracilis
