Lecture 3 - Sensory Systems of the Brain Flashcards
What are some examples of diseases affecting the spinal pathways?
multiple sclerosis
tertiary siphilous
How long is the neuron from your foot to the top of the spinal cord?
1 metre
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
What does Nucleus mean?
A group of similar brain cells which have a similar function
What does the Dorsal Column Nuclei consist of?
Gracile + Cuneate
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
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
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
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
What isn’t controlled by the Thalamus?
Smell
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
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
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
What is the Dorsal part of the Spinal Chord involved with?
Reflexes
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
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
