Structure of the nervous system Flashcards
What are the levels of organisation?
- Molecules (1Å)
- Synapses (1μm)
- Neurons (100μm)
- Networks (1mm)
- Maps (1cm)
- Systems (10cm)
- CNS (1m)
The cortex can be divided into four lobes:
- Frontal Lobe
- Parietal Lobe
- Occipital lobe
Temporal lobe
What is the frontal lobe associated with?
Complex cognitive and motor functions
What is the Parietal Lobe associated with?
Sensory information & integration
What is the Occipital lobe associated with?
vision
What is the Temporal lobe associated with?
auditory, higher level vision, speech
The cortex can be subdivided into specialised zones on the basis of:
- Gross anatomy (sulcal & gyral anatomy)
- Variations on cellular properties (Cytoarchitecture)
- Connectional anatomy Functional properties
These often coincide.
Gross anatomy of the frontal lobes?
- The central sulcus divides the frontal lobe from the parietal lobe
The precentral sulcus divides the rest of the frontal lobes from the ‘motor strip’
How does grey matter in the brain change throughout lifespan?
a reduction in grey matter volume across childhood and adolescence.
When do higher order association cortices mature?
Higher order association cortices mature only after lower-order somatosensory and visual cortices (Gogtay et al., 2004
Phylogenetically older regions mature earlier than…
newer regions.
How do networks work in the brain? What’s a simple example?
- The nervous system consists of neural networks which integrate and distribute information.
- The simplest neural networks can be represented as a chain of connected neurons, e.g. cells connecting retinal receptors to the cortex.
- Another example is the knee-jerk reflex arc. - Simple spinal cord networks can convert sensory information directly into a motor response independently of the brain.
What is convergence and divergence?
- Convergence: Information from several neurons is integrated to influence the firing of a few.
- Divergence: Information from a few neurons is distributed to several other neurons.
Convergence and Divergence in the visual system: Convergence from retinal receptors to the optic nerve, divergence from the nerve to the cortex.
What is serial and parallel processing?
- Serial processing - Information is processed in one place and passed to another in turn.
Parallel processing - Information is processed in several brain regions simultaneously.
Serial and Parallel processing in the visual system?
- Networks in the brain are organised
hierarchically – information is passed from once place to the next serially and transformed as it crosses various points in the network.
The brain is also parallel – information from a single source can be processed in many locations simultaneously.
What are cortical layers?
- The cortex forms the outer surface of the forebrain that covers the other forebrain structures.
It is comprised of six distinct layers (‘laminae’).
What is the Molecule layer?
· Top layer of the cortex
· Axons and dendrites
Few neurons
What is the External granular layer?
· Small pyramidal cells
· Dendrites in Layer 1
Axons to deeper layers
What is the External pyramidal layer?
· Medium/Large Pyramidal cells
· Dendrites in Layer 1
Axons to deeper layers or subcortical targets
What is the Internal granular layer?
· Stellate cells
· Small pyramidal cells
Axons stay within the cortex
What is the Internal pyramidal layer?
· Medium/large pyramidal cells
· Betz cells in motor strip
What is the Multiform layer?
· Fusiform and other neurons
Connections to thalamus
Cortical networks – inputs?
- Association Fibers (ipsilateral corticocortical)
- Commissural Fiber (contralateral corticocortical)
- Thalamocortical (specific)
Thalamocortical (non-specific)
Cortical networks – outputs?
- Association Fiber (to other cortical areas)
- Commissural Fiber (to other
contralateral cortex) - Corticostriate Fiber
- Corticorubral Fiber
Cortocopotine Fiber
Corticobulbar Fiber - Corticospinal Fiber (to the spinal cord)
Corticotectal Fiber
Corticothalamic Fiber
- Commissural Fiber (to other