Lecture 3 - Sensory Systems of the Brain Flashcards by sita clark

What are some examples of diseases affecting the spinal pathways?

multiple sclerosis

tertiary siphilous

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How long is the neuron from your foot to the top of the spinal cord?

1 metre

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What is a feature of the placement of fibres as they are added?

first ones, close to the midline, are from lower levels of the body, smaller cable
those from successively higher levels lye more lateral, thicker cable
top=millions of fibres=thick=terminate on second neuron=junction with the brain

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What does Nucleus mean?

A group of similar brain cells which have a similar function

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What does the Dorsal Column Nuclei consist of?

Gracile + Cuneate

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What happens when the fibres reach the brain?

Decussation
Continuos Medial Ribbon/Lemniscus
They cross the midline and go to opposite side of the brain
Goes through the medulla, pons and the midbrain to get to the thalamus

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What is a Medial Lemniscus?

Medial Ribbon
Continuous
Passes up as a compact bundle containing all sensory information form skin on the opposite side
Medial=close to the midline

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Where is the highest level of organisation in the brain?

Cerebral Cortex

Every input going up to the cortex has to go through the thalamus

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What is the function of the Thalamus?

Controls every input/information going to the large Cerebral Cortex
Except Smell
“relays impulses from sensory systems and terminates at various regions of the cerebral cortex”
Lots of compartments/nuclei

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What isn’t controlled by the Thalamus?

Smell

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What is the Ventral Posterior(VP) Nucleus?

Ventral part of thalamus
Posterior=back
Area where the fibres end/terminate on Neuron #3
processes sensory information
passes information up into Cerebral Cortex
information on opposite side of the brain

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What are the 3x types of Neurons in the Discriminative pathway?

Neuron1:Primary Root Afferents, Dorsal column of spinal cord
Neuron2:Gracile and Cuneate nuclei/Decussation/Medial Lemnicus
Neuron3:Ventral Posterior Thalamus to Sensory Cortex

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What do the three Neurons add up to?

a Relays
at each point there is further PROCESSING of the information
only consciously aware of touch and pressure information
Sensory information is given to the appropriate part of your body at a particular point in time
Modulate what you want to feel at any point in time

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What is the Dorsal part of the Spinal Chord involved with?

Reflexes

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What is the Posterior Dorsal Column?

In 2 bundles

Gracile Nucleus/Fasiculus
Thin and slender
Closer to Midline
Termination of all the fibres from the Lower parts of the thorax
anus,toes,foot,leg,thigh
Layered

Middle thorax t-5/6
division

Cunneate Nucleus/Fasiculus
(moon shape)
Thicker-lots of fibres
Termination of all the fibres from the Upper parts of the thorax
nipple,arm,fingers,neck

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What do the Gracile Fasiculus and Cunneate Fasiculus form?

Posterior/Dorsal column

What is the Posterior Dorsal Column?

Combination of the Gracile Fasciculus and Cunneate Fasiculus
on the dorsal side of the spinal cord
critical
central pathway of discriminative sensation- touch and pressure

What would happen if the posterior dorsal column was affected by a lesion?

Lose touch and pressure from the dermatome on the same side of the body

What is the C8 dermatome?

Cervical

ARM

What is the Medial Lemniscus?

large fibres (myelinated)
cross over in bundles + arch
form a huge bundle
Individual fibres clear
"Internal arching Fibres"

What does Decussation?

Brain and spinal cord junction
Crossing of arching fibres from one side of the medulla to the other
Clear bundle

What are some features of the thalamus?

Critical
42mm long
size of #8 egg
15 major offices dealing with individual different things
2x parts- medial + lateral part
medial= sensation from face only
lateral=sensation from skin of body below knee

What does the third order neuron do?

Processes information, takes to Sensory cortex via the Internal Capsule(motorway)
goes all the way to the cortex on the opposite side
highly organised according to body region

What is the central pathway of discriminative information?

3x relay pathway
highly organised
skin–>spinal cord–>dorsal posterior column–> 2nd-order-neuron=gracile+cunneate nuclei–> thalamus–>sensory cortex

at each level there is a processing of the information, to make you either a. more attentive to the information, or b. suppress from your consciousness

What is the dorsal horn?

Grey matter Sensory part Where non-discriminative somatosensory pathways terminate

What is another name for Discriminative Somatosensory pathway?

Posterior Column-Medial Lemniscus Pathway

What is another name for the Non-Discriminative Somatosensory Pathway?

Anterolateral/Lateral Spinothalamic Pathway

Where is the second order neuron in the non-discriminative pathway?

Dorsal horn | Neurotransmitters are released and neurons cross through white matter to other side of the spinal cord

Where does the decussation occur in the non-discriminative somatosensory pathway?

in the spinal cord Ant White Commissure At the same level

What is the non-discriminative second order neuron's lower pathway called?

Lateral Spinothalamic Tract pathway extends through the whole length of the spinal cord travels up opposite side

What is the non-discriminative second order neuron's upper pathway called?

Joins Medial Lemniscus going to the same area in the Thalamus= Ventral Posterior Nucleus Third order neuron goes to Sensory Cortex

What would happen if there was a Lesion in the Spinal Cord?

Lesion LEFT side of SPINAL CORD: discriminative pathway=loss of d.sensation in the LEFT(as decussation occurred at Gracile/Cunneate Nucleus (medulla))=same side of the body non-discriminative pathway=loss of n.d.sensation in the RIGHT(as decussation occurred at Anterior White Commissure)=opposite side + where abouts on the spinal cord DIS-associative Sensory Loss

What would happen if there was a Lesion in the Brain or Brainstem?

Lesion in the LEFT side of the Medulla, Pons, Midbrain or Cortex: discriminative pathway=loss of d.sensation in the RIGHT side of the body Non-discriminative pathway=loss of n.d.sensation in the RIGHT side of the body ASSOCIATIVE Sensory Loss BOTH sensory loss are on OPPOSITE sides BOTH pathways have Decussated prior to the Brain&Brainstem