Nervous System Flashcards
Frontal lobe identification
Central sulcus to start of lateral fissure
Parietal lobe identification
Central sulcus to parieto-occipital sulcus
Temporal lobe identification
Lateral fissure down
Occipital lobe identification
Posterior of parieto-occipital sulcus and pre-occipital notch
Arcuate fasciculus
Arch of fibres connecting Brocas area to Wernickes area
Motor planning area
Anterior to precentral sulcus near the top of the gyrus
Brocas area
Anterior to precentral sulcus near the middle of the gyrus
Speech formulation
Wernickes area
In the superior temporal gyrus of the temporal lobe
Interprets tones
Primary motor cortex
Anterior to central sulcus but posterior to precentral sulcus near the top of the gyrus
Primary somatosensory cortex
Posterior to central sulcus in the parietal lobe
Primary auditory cortex
Smaller area near Wernickes area in the superior temporal gyrus of the temporal lobe
Recognises tones
Tonotopic representation
Primary visual cortex
Right at the back of the occipital lobe
Supramarginal and angular gyri
M shape near the bottom of the parietal lobe responsible for reading and writing
Exners area
Plans writing movement
Above Brocas area and frontal eye fields in the frontal lobe
Frontal eye fields
Underneath Exners area and above Brocas area int he frontal lobe
Responsible for eyeball movement associated with reading
Supplementary visual cortices
Found in occipital and temporal lobes around the primary visual cortex
Responsible for a lot of peripheral vision
Calcarine sulcus
Sulcus along the middle of the occipital lobe. Primary visual cortex is right at the back and is responsible for central vision with peripheral vision areas located further along towards the temporal lobe
Supplementary motor area
Anterior to the precentral sulcus and primary motor cortex and above Exners area
Fluent aphasia
Wernickes aphasia
Can speak but not understand
Non-fluent aphasia
Brocas aphasia
Can understand but not form coherent words
Connectional aphasia
Problem with the arcuate fasciculus
Can understand and form coherent words but not connect the two or have a fluent conversation
Frontal lobe responsibilities
Intelligence Personality Mood Behaviour Cognitive function
Parietal lobe responsibilities
Spatial skills 3D recognition Shapes Faces Concepts Abstract perception
Temporal lobe responsibilities
Memory
Mood
Aggression
Intelligence
Right hemisphere responsibilities
Non-verbal language Emotional expression Spatial skills Conceptual understanding Creative skills
Number of nerve pairs
31
Number of cervical nerves
8
Number of thoracic nerves
12
Number of lumbar nerves
5
Number of sacral nerves
5
Number of coccygeal nerves
1
Dorsal root ganglion
Where cell bodies for afferent nerves are located
Ventral root ganglion
Where cell bodies for efferent nerves are located
Properties of discriminative neurons
Myelinated Pseudounipolar Encapsulated 50 m/s Cell body in the dorsal root ganglion Can end in the grey dorsal horn or the white matter dorsal columns
Properties of non-discriminative neurons
Unmyelinated Pseudounipolar Free nerve ending 1 m/s Cell body in the dorsal root ganglion End in the top of the grey dorsal horn
Pacinian corpuscle
Encapsulated receptor for pressure
Meissner corpuscle
Encapsulated receptor for touch
Convergence
Nerves come together and are processed by spinal cord as one to save space
Gracile fasciculus
Inner white matter tract of the dorsal columns
Hip to toe
Cuneate fasciculus
Outer white matter tract of the dorsal columns
Hip to head
Funiculus
Cuneate fasciculus + gracile fasciculus
Describe the route of discriminative sensation to the cortex
1st order neuron: starts in the encapsulated receptor with cell body in the dorsal root ganglion. Enters spinal cord and ends at the cuneate or gracile nuclei
2nd order neuron: starts at cuneate or gracile nuclei and decussates immediately via internal arcuate fibres then goes up the brainstem where it joins the medial lemniscus then enters the brain and terminates in the ventro-posterior thalamus
3rd order neuron: starts at the ventro-posterior thalamus and moves up the brain towards the primary sensory cortex
Cuneate nuclei
Where first order neuron ends in discriminative sensation for upper body
Gracile nuclei
Where first order neuron ends in discriminative sensation for lower body
Name of discriminative sensation pathway
Dorsal column medial lemniscus pathway
Name of non-discriminative sensation pathway
Lateral spinothalamic tract pathway
Describe the route of non-discriminative sensation to the cortex
1st order neuron: starts in a free nerve ending with a cell body in the dorsal root ganglion, moves into the spinal cord and ends at A-C fibres in dorsolateral tract of Lissauer
2nd order neuron: starts in the spinal cord at A-C fibres in dorsolateral tract of Lissauer and decussates immediately at the anterior white commissure where it moves up the spinal cord into the brainstem via the lateral spinothalamic tract and up to where it joins the medial lemniscus eventually terminating in the ventro-posterior thalamus
3rd order neuron: starts in the ventro-posterior thalamus and tracks up to terminate in the primary somatosensory cortex
Medical lemniscus
Ascending bundle of fibres formed by crossings of internal arcuate fibres
Raffini corpuscle
Encapsulated receptor for stretch
Associative sensory loss
Discriminative and non-discriminative loss on the same side
Occurs when there is a lesion in the brain or brainstem so the loss of both sensations is on the opposite side of the lesion
Dissociative sensory loss
Discriminative and non-discriminative loss on different sides
Occurs when there is a lesion in the spinal cord so discriminative sensation is lost on the same side of the lesion and non-discriminative sensation is lost on the opposite side
Pyramidal cells
Large pyramid shaped cells that project from brain through spinal cord to complete motor movement
Describe the route of motor movement to muscles
Starts in the motor cortex and moves down the brain through the internal capsule to the pons where the pyramidal tract is located. In the pons, neurons often spread out for more space, hence the bulge at this level. The neuron continues down past the medulla where it either decussates at the pyramidal cells (85%, lateral corticospinal tract) or at the spinal segmental level (15%, ventral corticospinal tract). Both pathways terminate in the spinal cord - this is all the upper motor neuron. The lower motor neuron then moves to the muscle to complete the movement.
5 basal ganglia nuclei
Caudate nucleus Putamen Globus pallidus Subthalamic nucleus Substantia nigra
Striatum
Caudate nucleus + putamen
Internal capsule
White matter tract between the caudate nucleus/thalamus and the putamen/globus pallidus
3 types of white matter tract
Commissural - between hemispheres
Association - within hemisphere
Projection - ascending and descending
Claustrum
Thin, irregular sheet of neurons peripheral to the putamen
Role of basal ganglia
Learned, practiced movements
Takes over from cerebellum when a certain movement is practiced a lot
Movement initiation
Dopamine reward pathway
Role of cerebellum
Termination of, repetitive and ballistic movement
Unlearned and coarse movement
Describe what happens when the dopamine pathway is reduced
Loss of movement
Loss of some mood and impulse
Describe how a healthy dopamine pathway would normally function
Dopamine positive fibres extend from the substantia nigra (caudal side) to the bottom of the putamen in the striatum. A threshold of striatal cells must be kept activated for the normal GABA pathway to be set off. Neurons in the striatum fire to inhibit GABA so it doesn’t inhibit glutamate too much. Dopamine keeps these cells in the striatum activated above a threshold so GABA can travel to the external globus pallidus and then the internal globus pallidus where the neuron terminates in the ventral-anterior thalamus. With GABA inhibition, glutamate travels to the cerebral cortex initiating normal movement.
Describe how the dopamine pathway works in Parkinsons
The substantia nigra is damaged meaning reduced dopamine is travelling to the striatum. The striatal cells, which would normally inhibit GABA when needed, now can’t fire because they are not active enough. GABA is free to inhibit glutamate in the thalamus which prevents the glutamate from travelling to the cerebral cortex and initiating normal movement.
Four treatments for Parkinsons
ECT
Pallidotomy
Thalalotomy
Levo-Dopa
Levo-Dopa
Parkinsons drug
Precursor to dopamine
Alleviates symptoms but not a cure - stops working after about 8 years
Pallidotomy
Lesion introduced in the globus pallidus, inhibiting GABA and reinstating the rest of the normal glutamate pathway
Thalalotomy
Lesion introduced in the thalamus, inhibiting the inhibitory effects of GABA and allowing the glutamate to travel to the cerebral cortex
Very good for tremor, not great for other symptoms
Spastic paralysis
Persistent spasms and exaggerated tendon reflexes, increased rigidity
Lesion in upper motor neuron leads to increased activity in lower motor neuron
Flaccid paralysis
Less activity, no control
Lesion in lower motor neuron
Nigrostriatal pathway
From substantia nigra to striatum