somatic sensory cortex to rostrospinocerebellar

• Region of the cerebral cortex that first receives the inputs from the (third-order) neurons in the ventral posterior complex of the thalamus

• Located in posterior bank of central sulcus (postcentral gyrus)

• Includes Brodmann’s Areas 3a, 3b, 1 and 2

Primary somatic sensory cortex (SI)

Region of the cerebral cortex that first receives the inputs from the (third-order) neurons in the ventral posterior complex of the thalamus

Primary somatic sensory cortex (SI)

Located in posterior bank of central sulcus (postcentral gyrus)

Primary somatic sensory cortex (SI)

Includes Brodmann’s Areas 3a, 3b, 1 and 2

Primary somatic sensory cortex (SI)

responds primarily to stimulation of “proper” proprioceptors (e.g., muscle spindles, joint receptors)

Area 3a:

responds primarily to simple cutaneous stimuli applied to localized skin surfaces (e.g., discriminative

touch)

§ Area 3b:

responds to more complex cutaneous stimuli, often involving stimulation of multiple digits in a certain direction

§ Area 1:

responds to both complex tactile and proprioceptive stimuli

§ Area 2:

TRUE OR FALSE: Each subdivision of the primary somatic sensory cortex contains a complete “map” of the contralateral sensory surface

TRUE

TRUE OR FALSE: Each subdivision of the primary somatic sensory cortex contains a complete “map” of the ipsilateral sensory surface

FALSE dapat contralateral

is a distorted representation of the human body, based on a neurological "map" of the areas and proportions of the human brain dedicated to processing motor functions, or sensory functions, for different parts of the body.

Cortical homunculus:

• Lies in the upper bank of the lateral sulcus

• Receives convergent projections from all subdivisions of SI

• Area SII sends projections in turn to limbic structures such as the amygdala and hippocampus to play an important role in tactile learning and memory.

• Neurons in SI also project to parietal areas posterior to area 2, especially areas 5 and 7 which supply inputs to neurons in motor and premotor areas of the frontal lobe.

Secondary somatic sensory cortex (SII)

Lies in the upper bank of the lateral sulcus

Receives convergent projections from all subdivisions of SI

Area SII sends projections in turn to limbic structures such as the amygdala and hippocampus to play an important role in tactile learning and memory.

Neurons in SI also project to parietal areas posterior to area 2, especially areas 5 and 7 which supply inputs to neurons in motor and premotor areas of the frontal lobe.

supply inputs to neurons in motor and premotor areas of the frontal lobe.

areas 5 and 7 which

what are the pathways to the brain?

Conscious relay pathways

divergent pathways

unconscious relay pathways

transmitted with high fidelity, thus providing accurate details regarding the stimulus and its location

a. Conscious relay pathways

information to many locations in the brainstem and

cerebrum and uses pathways with varying numbers of

neurons

b. Divergent pathways

brings unconscious proprioceptive and other

movement-related information to the cerebellum

c. Unconscious relay pathways

Carries signals upward mainly in the dorsal columns of the cord → signals synapse → cross to the opposite side in the medulla → continue upward through the brain stem → thalamus via medial lemniscus

1. Dorsal column – medial lemniscal system pathway

3-neuron relay of DCMLS

DCMLS: Three-neuron relay

• Primary, or first-order à neuron conveys information from the

receptors to the medulla.

• Secondary, or second-order à neuron conveys information

from the medulla to the ventral posterolateral (VPL) nucleus of

the thalamus.

• Tertiary, or third-order à neuron conveys information from the

thalamus to the cerebral cortex.

Enters the spinal cord from the dorsal spinal nerve roots → synapse in the dorsal horns of the spinal gray matter → cross to the opposite side of the spinal cord → ascend through the anterior and lateral white columns of the cord → terminate at all levels of the lower brain stem and in the thalamus

2. Anterolateral system pathway

What are the tracts of the ALS?

Anterior spinothalmic tract

Lateral spinothalmic tract

carries the sensory modalities of crude touch and pressure.

Anterior spinothalamic tract –

carries the sensory modalities of pain and temperature.

2. Lateral spinothalamic tract –

ALS: Three-neuron relay

• Primary, or first-order à neuron conveys information into the

dorsal horn of the spinal cord

• Secondary, or second-order à axon crosses the midline and

projects from the spinal cord to the thalamus.

• Tertiary, or third-order à neuron conveys information from the

thalamus to the cerebral cortex.

Lesions along ALS

• Peripheral region below the lesion

Ipsilateral loss of body

Lesions along ALS

• One or two levels below the lesion

Contralateral loss of body

Lesions along ALS

• Before lower pons, medulla if interrupted

Ipsi/L of face, Contra/L of body

Lesions along ALS

• Lesions above the lower pons and medulla

Entire Contralateral loss

• Central pathways conveying tactile information from the face

• Cutaneous mechanoreceptor information from the face is conveyed centrally by a separate set of first-order neurons that are located in the trigeminal (cranial nerve V) ganglion

Trigeminothalamic System

Central pathways conveying tactile information from the face

Trigeminothalamic System

Cutaneous mechanoreceptor information from the face is conveyed centrally by a separate set of first-order neurons that are located in the trigeminal (cranial nerve V) ganglion

Trigeminothalamic System

Cutaneous mechanoreceptor information from the face is conveyed centrally by a separate set of first-order neurons that are located in the _______

trigeminal (cranial nerve V) ganglion

Trigeminothalmic System: Three-neuron relay

• Primary, or first-order → neuron conveys information from

trigeminal ganglion cells to trigeminal brainstem complex.

• Secondary, or second-order → axon crosses the midline and

projects from the trigeminal brainstem nuclei and ascend to

ventral posteromedial (VPM) nucleus of the thalamus.

• Tertiary, or third-order → neuron conveys information from the

thalamus to the cerebral cortex.

Not somatotopically organized, so slow pain cannot

be precisely localized.

Medial Pain System

What are the tracts of the medial system?

Spinomesencephalic tract

Spinoreticular tract

Spinolimbic tract

involved in turning the eyes and head toward the source of noxious input and in activating descending tracts that control pain.

Spinomesencephalic tract

synapse in the brainstem reticular formation and severe pain commands attention and interferes with sleep.

2. Spinoreticular tract

transmit slow pain information to the medial and intralaminar nuclei in the thalamus

Responsible for affective responses to pain

3. Spinolimbic tract

transmit slow pain information to the medial and intralaminar nuclei in the thalamus

3. Spinolimbic tract

Responsible for affective responses to pain

3. Spinolimbic tract

• Information from proprioceptors and information about activity in spinal interneurons are transmitted to the cerebellum via → Spinocerebellar tracts

• This information, which does not reach conscious awareness, contributes to automatic movements and postural adjustments.

Unconscious Pathways

Information from proprioceptors and information about activity in spinal interneurons are transmitted to the cerebellum via → Spinocerebellar tracts

Unconscious Pathways

UNCONSCIOUS PATHWAY

Information from proprioceptors and information about activity in spinal interneurons are transmitted to the cerebellum via →

Spinocerebellar tracts

This information, which does not reach conscious awareness, contributes to automatic movements and postural adjustments.

Unconscious Pathways

Deliver information from receptors in muscles, tendons, and joints from peripheral neurons to the cerebellum

High-fidelity pathways

What are the 2 under high-fidelity pathways?

Posterior spinocerebellar tract

Cuneocerebellar tract

transmits information from the legs and the lower half of the body

1. Posterior spinocerebellar tract

primary afferents from the arm and upper half of the body

2. Cuneocerebellar tract

Specialized to provide feedback to the cerebellum about the activity in spinal interneurons and in the descending motor tracts.

Internal feedback tracks

What are the 2 under internal feedback tracks?

Anterior spinocerebellar tract

Rostrocerebellar tract

• transmits information from the thoracolumbar spinal cord.

• Carries proprioceptive information from the lower limbs. The fibers decussate twice – and so terminate in the ipsilateral cerebellum.

Anterior spinocerebellar tract

• transmits information from the cervical spinal cord.

• Carries proprioceptive information from the upper limbs to the ipsilateral cerebellum.

2. Rostrospinocerebellar tract

transmits information from the thoracolumbar spinal cord.

Anterior spinocerebellar tract

Carries proprioceptive information from the lower limbs. The fibers decussate twice – and so terminate in the ipsilateral cerebellum.

Anterior spinocerebellar tract

transmits information from the cervical spinal cord

2. Rostrospinocerebellar tract

Carries proprioceptive information from the upper limbs to the ipsilateral cerebellum.

2. Rostrospinocerebellar tract