Nervous system: Sensory Systems of the Brain Flashcards
Label the diagram
What is the central part of the spinal cord made of?
Grey matter
What is the surrounding parts of the grey matter in the spinal cord made of?
White matter
What is the grey matter made of?
Cell bodies
What is white matter made of?
Nerve fibers
What do the cell bodies do?
Decide on the neural response to signals
What does the dorsal column do?
It transmits the neural information up the spinal cord into the brain
What do funiculi, fasciculus and columns in neural material have in common?
They are all bundles of white matter which transmit neural information
What is a gracile and cuneate fasciculus on one side of the spinal segment called? What are both fragile and cuneate fasciculus called?
Funiculi
Dorsal column
What information does the gracile fasciculus carry? Relatively how large would the gracile fasciculus be at the bottom of the spinal cord vs the top?
Information from the hips down
Would be relatively large (more nerves coming from lower part of body into spinal cord)
What information does the cuneate fasciculus carry? Relatively how large would the cuneate fasciculus be at the bottom of the spinal cord vs the top?
From the hip up to the neck
Would be relatively small (no nerves coming from upper part of body into spinal cord here, but further up the spinal cord it would be larger)
What is the representation on the fasciculus called?
A homunculus respresentation
Where do most encapsulated nerves connect to in the spinal cord?
Directly into the dorsal column
Where some of the encapsulated nerves connect to? What process occurs here with these nerves?
They connect into the grey matter
Convergence
What is the purpose of convergence?
It causes the signals from many nerves to become integrate into a single nerve which is then linked into the dorsal column reducing the space needed for info transfer (therefore reducing size of spinal cord)
Where do the free nerve endings go?
They go into the grey matter then into the spinothalamic tract
What does the lateral corticospinal tract do?
Carries information from brain to lower motor neurons
What happens to lower motor neurons?
Nerves go out to muscles via the ventral root
What is a very generalised principle about where information goes into/out of the spinal cord?
Information generally (though there are exceptions) goes to the brain through the dorsal side of the spinal cord, information goes out of the spinal cord through the ventral root
Label the diagram, what kind of pathway is this describing?
Discriminative sensation (touch and pressure)
Label the diagram, what kind of pathway is this describing?
Discriminative sensation (touch and pressure) I
What is the function of the gracile and cuneate nuclei?
It is to receive all the nerve fibres from the gracile and cuneate fasciculus respectively
What is the nerve fibre called once it has passed through the cuneate/gracile nuclei?
It is called the medial lemniscus
How does the position of the medial lemniscus change as it moves up the brain?
It moves further back in the brain as it moves up
How does the lateral spinothalamic tract move through the brain?
It moves back as it goes up the brain
When the lateral spinothalamic tract is going to the medial lemniscus, how does it join with it? Where does it go?
It becomes a nerve that is NEXT TO the medial lemmiscus, goes to the thalamus
Do the non-discriminatory and discriminatory pathways both go to the same place?
Not quite, they go to the same region of the cortex but are in different levels of the brain tissue
What do the different pathways innervate?
Different synapses
Label the diagram, what kind of pathway is this describing?
Non-discriminative
What is decussation?
When the nerves cross over onto the other side of the body
Where do the discriminative and non-discriminative neurons decussate?
Discriminative: Internal articulate fibres
Non-discriminative: spinal cord
If there was damage on the medial lemniscus and the lateral spionthalamic tract in the right hand side of the brain, what would be the impact?
There would be an associative sensory loss on the left hand side of the body for both pain/temperature and pressure/touch
If there was damage on the medial lemniscus and the lateral spionthalamic tract in the right hand side of the spinal cord, what would be the impact?
There would be a dissociative sensory loss for pain/temperature on the left hand side and pressure/touch on the right hand side
Why are the associative sensory losses for pain/temp and pressure/touch different depending on where there is damage?
The Dorsal funicular (pressure/touch nerve) decussates (swaps over) in the gracile/cuneate nuclei (due to internal arcuate fibres FYI) which is at the lower medulla while the lateral spinothalamic tract (pain/temp) decussates in the spinal cord. This means that the two sensation systems are not aligned with each other for part of the nervous system therefore can have different response in to the same location damage
Where does the 1st neuron of discriminative and non-discriminative neurons terminate?
Discriminative: Cuneate/Gracile nuclei
Non-discriminative: grey matter of spinal cord
How does the free nerve ending get into the spinal segmental level? What does it do once in here?
Gets into the spinal segmental level via the dorsal root
Once in the spinal level it synapses in the posterior part of the grey matter and then connects to the spinothalmaic tract
When the free nere ending connects to the spinothalamic tract, what process is occuring?
Decussation (crosses over onto other side of the body)
