Sensory Tracts (Oct 8)

What is the general pathway for signals to reach your brain?

Sense in periphery. Ascending tract. Thalamus - 1o sensory.

Diagram of sensory pathway [Image]?

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What are 1st order sensory afferents from and what types of information? Where do they end?

From: spinal nerves and cranial nerves. Touch, pressure, proprioception, pain, temperature. Dorsal root ganglia.

Diagram of the spinal cord [Image]?

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Compare the ventral rami and dorsal rami?

Ventral rami is responsible for most of the signals.

Sensory pathway in the spinal cord [Image]?

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Motor pathway in the spinal cord [Image]?

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Pathway of PNS + CNS integration @ spinal cord [Image]?

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What are dermatomes?

Spinal levels supplying areas of skin (sensory)

Diagram of dermatomes [Image]?

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Diagram of 2nd order sensory afferents [Image]?

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What is the responsibility of the thalamus?

Selective attention + Sensory integration/relay

What is the 3rd sensory afferent?

Thalamus to somatosensory cortex via internal capsule.

What is within the internal capsule?

White matter tract between thalamus/lateral ventricles + basal nuclei (projection fiber). Sensory + motor information. Becomes “corona radiata” superiorly.

Diagram of 3rd order sensory afferent [Image]?

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Where is the somatosensory cortex?

Post-central gyrus.

Diagram of the somatosensory cortex [Image]?

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What are the 2 systems for ascending pathways?

Two systems: Dorsal column - medial lemniscus (for touch, pressure + proprioception - quantitative sensations). Spinothalamic (for pain + temperature - qualitative sensations)

Which types of receptors do DCML and spinothalamic pathways use?

DCML: Mechanoreceptors. Spinothalamic: Thermoreceptors. Nociceptors (temp, mech, pain).

Diagram of ascending pathways [Image]?

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What is the pathway for spinothalamic tracts?

Synapse 1: Spinal cord. Fibres decussate and ascend contralaterally to stimulus. Synapse 2: thalamus. Terminates: somatosensory cortex, also temporal lobe for memory + emotional response.

Collaterals to reticular formation carries what type of information?

Pain modulation. Alertness.

What is reticular formation?

Grey matter within brainstem.

Diagram of spinothalamic tracts [Image]?

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Describe the pathway of dorsal column - medial lemniscus?

Fibres ascend ipsilaterally (to stimulus) in dorsal column. Synapse 1: Medulla - Gracile Nucleus (legs <T6), Cuneate Nucleus (arms, >T6). Fibres decussate and become “medial lemniscus" on their way to thalamus. Synapse 2: Thalamus. Terminate: Somatosensory cortex.

Diagram of dorsal column - medial lemniscus [Image]?

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What is the purpose of spinocerebellar + DCML?

Carries proprioceptive information to ipsilateral cerebellum. Cerebellum is key for movement modulation. Used to modify movement patterns.

Diagram of spinal cerebellar + DCML [Image]?

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Diagram of dorsal column-medial lemniscus and spinothalamic [Image]?

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What are the sensory receptors for the autonomic nervous system?

Interoceptors (within organs). Fibers run with somatic sensory fibers..

What is referred pain?

Dull aching pain, hard to localize and often not at the site of damage.

Why is referred pain possible?

Autonomic sensory nerves (from organs) enter dorsal horn of spinal cord and synapse on second order neuron. Because of this signal convergence (somatic + autonomic), 3rd order neurons in thalamus can’t differentiate between the sources.

Diagram of referred pain [Image]?

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Diagram of autonomic sensory fibers and somatic sensory fibers [Image]?

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Diagram of areas of referred pain [Image]?

Heart

Liver and gallbladder

Lung and diaphragm

Small intestine

Pancreas

Stomach

Ovary

Kidney

Urinary bladder

Ureter

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