Neuroscience Anat (Sensory pathways) Flashcards
State the sensory neurons and processes invovled in the somatosensory pathway
1 - PNS - first order sensory neuron
2 - CNS - second order sensory neuron
- axons decussate across midline
3 - CNS (thalamus)
4 - CNS - third order neuron for DCML/spinothalamic
- axons send neuronal information to the postcentral gyrus (primary sensory cortex0
Recap:
State the functions of each of the somatosensory pathways
(1) SPINOTHALAMIC
- crude touch and pressure
- pain and temperature
(2) DORSAL COLUMN MEDIAL LEMNISCUS
- fine touch
- conscious proprioception
- vibrations
- pressure
(3) SPINOCEREBELLAR
- unconscious proprioception
State the 4 cutaneous mechanoreceptors and their functions
- meissner’s corpuscle - changes in texture, slow vibrations
- merkel’s disc - sustained touch and pressure
- ruffini nerve endings - sustained pressure
- pacinian corpuscle - deep pressure, fast vibrations
State the 4 common free nerve endings and their functions
- thermoceptor - temperature
- nociceptor - pain
- bulboid corpuscles - cold
- chemoreceptor - chemical substances
SUMMARISE!
State the 4 common cutaneous mechanoceptors and the 4 common free nerve endings and their functions.
CUTANEOUS MECHANOCEPTORS
1. meissner’s corpuscle - slow vibrations, changes in texture
2. merkel’s disc - sustained pressure and touch
3. ruffini nerve endings - sustained pressure
4. pacinian corpuscle - fast vibrations, deep pressure
FREE NERVE ENDINGS
1. thermoceptors - temperature
2. nociceptor - pain
3. bulboid corpuscles - cold
4. chemoreceptors - chemical substances
State the pathway for the spinothalamic tract
SPINOTHALAMIC TRACT
1. receptor
2. 1st order neuron - dorsal root through DRG
3. synapse onto 2nd order neuron in spinal cord
4. 2nd order neuron decussates to anterior or lateral horn
5. ascends up the spinal cord to synapse with 3rd order neuron at thalamus
6. 3rd order neuron sends information to postcentral gyrus (primary sensory cortex) for
lateral spinothalamic - pain and temperature
anterior spinothalamic - crude touch and pressure
State the pathway for the dorsal column medial lemniscus tract
DORSAL COLUMN MEDIAL LEMNISCUS TRACT
1. receptor
2. 1st order neuron - dorsal root through DRG
3. 1st order neuron ascends up spinal cord into medulla oblongata
4. synapse onto 2nd order neuron at MO
5. 2nd order neuron decussates at MO
6. 2nd order neuron ascends up to synapse with 3rd order neuron at thalamus
7. 3rd order neuron sends information to postcentral gyrus (primary sensory cortex)
DCML = fine touch, pressure, vibrations, conscious proprioception
- nucleus gracilis - for lower body
- nucleus cuneatus - for upper body
State the pathway for the spinocerebellar tract
SPINOCEREBELLAR TRACT
1. receptor
2. 1st order neuron - dorsal root through DRG
3. synapse onto 2nd order neuron (dorsal horn neuron) at level of spinal cord
4. most 2nd order neurons do not decussate, some decussate
5. (for those that do not decussate) posterior cerebellar pathway –> inferior cerebral peduncle
6. (for those that decussate) anterior cerebellar pathway –> superior cerebral peduncle then decussates again at cerebrum
State the pathway for the trigemino-thalamic tract
State the functions of the trigemino-thalamic tract.
TRIGEMINO-THALAMIC TRACT
1. receptor
2. 1st order neuron at trigeminal ganglion
3. synapse at brainstem to 2nd order neuron (trigeminal sensory nuclei) which enters brainstem
4. 2nd order neuron decussates and ascends to thalamus
5. synapse at thalamus to 3rd order neuron (ventral posterior medial nucleus)
6. 3rd order neuron brings information to the postcentral gyrus (primary sensory cortex)
FUNCTIONS
- crude touch and pressure
- pain and temperature
- fine touch
- conscious proprioception
State the functions of CN I - IV.
CN I - ophthalmic N
- special sensory = smell
CN II - optic N
- special sensory = vision
CN III - oculomotor N
- somatomotor = EOM (SR, IR, MR, IO), LPS
- visceromotor = IOM (ciliary muscles, sphincter pupillae)
CN IV - trochlear N
- somatomotor = EOM (SO)
State the functions of CN V-VIII
CN V - trigeminal N
- somatosensory - V1,V2,V3
- (general) sensory = V3 gives rise to lingual N which provides general sensory to anterior 2/3 of tongue
- somatomotor - V3 - muscles of mastication / 1st pharyngeal arch muscles (masseter, temporalis, lateral and medial pterygoid + tensor tympani, tensor veli palitini, mylohyoid, anterior belly of digastric)
CN VI - abducens N
- somatomotor - EOM (LR)
CN VII - facial N
- somatosensory - part of external acoustic meatus and deeper parts of auricle
- special sensory = chorda tympani - taste for anterior 2/3 of tongue
- somatomotor - 2nd pharyngeal arch (muscles of facial expression + stapedius + stylohyoid + posterior belly of digastric)
- visceromotor = all glands in face except parotid gland
CN VIII - vestibulocochlear N
- special sensory = hearing and balance
State the functions of CN IX-XII
CN IX - glossopharyngeal N
- somatosensory = posterior 1/3 of tongue, external ear and pharynx
- special sensory = taste of posterior 1/3 of tongue
- somatomotor = stylopharyngeus
- viscerosensory = from carotid body and sinus
- visceromotor = parotid gland
CN X - vagus N
- somatosensory = external ear and larynx
- special sensory = taste in epiglottis
- somatomotor = all muscles of pharynx (except stylopharyngeus), all muscles of soft palate (except tensor veli palitini), all intrinsic muscles of larynx
- viscerosensory = heart, lungs, digestive system
- visceromotor = distant organs
CN XI - spinal accessory N
- somatomotor = trapezius and SCM
CN XII - hypoglossal N
- somatomotor = all muscles of tongue (except palatoglossus)
State the cranial nerves with
(1) special sensory function
(2) somato-motor funciton
(3) mixed functions
(4) parasympathetic funcitons
(1) PURE SPECIAL SENSORY FUNCTION = 1,2,8
- CN I - olfactory N - smell
- CN II - optic N - vision
- CN VIII - vestibulocochlear N - hearing
(2) SOMATO-MOTOR FUNCTION = 3,4,6,11,12
- CN III - oculomotor N - EOM (SR,IR,MR,IO,LPS)
- CN IV - trochlearr N - EOM (SO)
- CN VI - abducens N - EOM (LR)
- CN XI - spinal accessory N - trapezius and SCM
- CN XII - hypoglossal N - all muscles of tongue except palatoglossus
(3) MIXED FUNCTION = 5,7,9,10
- CN V - trigeminal N
- CN VII - facial N
- CN IX - glossopharyngeal N
- CN X - vagus N
(4) PARASYMPATHETIC (viscero-motor) FUNCTION = 3,7,9,10
- CN III - oculomotor N - ciliary muscles and sphincter pupillae (ciliary G)
- CN VII - facial N - all glands in face except parotid gland (pterygopalatine and submandibular G)
- CN IX - glossopharyngeal N - parotid gland (otic G)
- CN X - vagus N
State everything you know about trigeminal neuralgia (presentation, exacerbating factors, cause)
TRIGEMINAL NEURALGIA
- presentation = excruciating pain on one side of face
- exacerbating factors = chewing, brushing teeth, washing face
- cause = trigeminal N irritation at base of brain by compression from anomalous blood vessel
State the 3 types of trigeminal sensory nuclei complexes.
- principal (chief) sensory nucleus
- spinal nucleus
- mesencephalic nucleus
SPINAL NUCLEUS OF TRIGEMINAL NERVE
- Recap: The other nucleus are ____ and ____
- Located in the ____ and ____ cervical spinal cord
- Receives sensation of ____ and ____ from the central processes of ____ neurons located in ____ ____ and sensory ganglia of CN ___, ____, ____
State the pathway of spinal nucleus of trigeminal nerve
SPINAL NUCLEUS OF TRIGEMINAL NERVE
- Recap: The other nucleus are CHIEF SENSORY NUCLEUS and MESENCEPHALIC NUCLEUS
- Located in the MEDULLA and UPPER cervical spinal cord
- Receives sensation of PAIN and TEMPERATURE from the central processes of SENSORY neurons located in TRIGEMINAL GANGLION and sensory ganglia of CN VII, IX, X
PATHWAY:
trigeminal ganglion and sensory ganglion of CN VII, IX and X –> spinal nucleus of trigeminal N –> decussate –> thalamus –> sensory cortex
PRINCIPAL (CHIEF) SENSORY NUCLEUS
- Recap: The other nucleus are ____ and ____
- Located in ____
- Received sensation of ____ and ____ from the ____ processes of ____ neurons located in ____ ____
State the pathway of principal (chief) sensory nucleus.
PRINCIPAL (CHIEF) SENSORY NUCLEUS
- Recap: The other nucleus are SPINAL NUCLEUS and MESENCEPHALIC NUCLEUS
- Located in PONS
- Received sensation of TOUCH and PRESSURE from the CENTRAL processes of SENSORY neurons located in TRIGEMINAL GANGLION
PATHWAY:
trigeminal ganglion –> principal sensory nucleus –> decussate–> thalamus –> sensory cortex
MESENCEPHALIC NUCLEUS
- Recap: The other nucleus are ____ and ____
- Located in the ____
- Contains ____ sensory neurons ( ____ order sensory neurons)
- Receives ____ impulses from muscles of ____ and ____
State the pathway of mesencephalic nucleus.
MESENCEPHALIC NUCLEUS
- Recap: The other nucleus are PRINCIPAL (CHIEF) SENSORY NUCLEUS and SPINAL NUCLEUS
- Located in the MIDBRAIN
- Contains UNIPOLAR sensory neurons ( 1ST order sensory neurons)
- Receives PROPRIOCEPTIVE impulses from muscles of MASTICATION and TMJ
PATHWAY:
through trigeminal ganglion to mesencephalic Nc of V –> brainstem –> decussate –> thalamus –> sensory cortex
State the modalities of each trigeminal somatosensory nuclei complex and state the pathways taken by each nuclei
(1) SPINAL NUCLEUS
- receives sensation for pain and temperature
- trigeminal ganglion/ sensory ganglion for CN VII,IX,X –> spinal nucleus of trigeminal N –> decussate –> thalamus –> sensory cortex
(2) PRINCIPAL (CHIEF) SENSORY NUCLEUS
- receives sensation for touch and pressure
- trigeminal ganglion –> principal sensory nucleus –> decussate –> thalamus –> sensory cortex
(3) MESENCEPHALIC NUCLEUS
- receives sensation for proprioceptive impulses (muscles of mastication and TMJ)
- mesencephalic nucleus –> brainstem –> decussate –> thalamus –> sensory cortex
