General structure of the nervous system Flashcards
What is the PNS made up of?
Nerves and ganglia
What is the brainstem composed of?
Midbrain, pons and medulla
Where is the white matter located in the cortex?
Inner
What is white matter composed of in the cortex?
Myelinated axons and glia
Where is the grey matter located in the cortex?
Outer
What is the grey matter composed of in the cortex?
Neuron cell bodies and glia
What cell type is found in both they grey and white matter of the cortex?
Glial cells
What technique can be used to visualise only white matter tracts in the brain?
Diffusion weighted MRI
What can diffusion weighted MRI be utilised for?
Viewing white matter tracts in the brain
Where does the kink/change in direction of the brain occur?
Between midbrain and diencephalon
What is the consequence of the kink/change in direction of the brain?
Twist in brain axis
Dorsal shifts from being ‘upwards’ to ‘backwards’
What separates the two cerebral hemispheres?
Longitudinal fissure
What does the longitudinal fissure separate?
Left and right cerebral hemispheres
What are the ridges in the cerebrum called?
Gyri
What are gyri?
Ridges in the cerebrum
What are the grooves in the cerebrum called?
Sulci
What are sulci?
Grooves in the cerebrum
What is the surface of the cerebrum?
Cerebral cortex
What is the functional significance of the four lobes of the cortex?
Very limited functional significance
They are arbitrary boundaries
Why are Brodmann areas significant?
Functional mapping of the brain, with defined boundaries that are functionally significant
What are Brodmann areas based on?
Cellular differences
How are the left and right cerebral hemispheres joined?
Corpus callosum
Describe the structure of the cortex?
1 cm thick
Outer grey matter, inner white matter
Layered structure (6 layers)
What types of neurons are found in the cortex?
Pyramidal neurons and interneurons
What are the major roles of the cerebellum?
Motor control
Comparing what you want to do with what you are doing
Refines execution of motor program
Where are most of the brain’s neurons located?
Cerebellum (half of all neurons)
Where are basal ganglia found in the brain?
Diencephalon
Deep within brain, beneath white matter
What are the roles of basal ganglia?
Motor control
Selects and initiates voluntary movements
What is the consequence of damage to the basal ganglia?
Parkinson’s Disease
Huntington’s Disease
Within which brain structure is the thalamus found?
Diencephalon
What is the major role of the thalamus?
Major sensory relay to cortex
Describe the structure of the thalamus?
Pair of nuclei
Distributed bilaterally
Describe the three ways in which thalamic nuclei project?
- Relays sensory info to cortex
- Relays non-sensory info from cortex and basal ganglia to specific areas of cortex
- Projects globally to cortex
What are the major roles of the hypothalamus?
Regulates homeostasis
Controls pituitary
Where is the pituitary gland located relative to the hypothalamus?
Located beneath it
What are the major functions of the brainstem?
Facial muscle control
Control of sensation from face and head
Cardiorespiratory control
Sleep/wake cycle
Which brain structure does the spinal cord connect to?
Medulla
Describe the arrangement of grey and white matter in the spinal cord?
Grey matter inner
White matter outer
What are the three major regions in the grey matter of the spinal cord?
Dorsal horn
Intermediate zone
Ventral horn
What information do the dorsal and ventral horns deal with?
Dorsal horns deal with incoming sensory information
Ventral horns deal with outgoing motor information
What are the divisions of the spinal cord?
Cervical
Thoracic
Lumbar
Sacral
How does the spinal cord change along its length?
Changes shape, but maintains overall ‘H’ shape
Enlarged at lower cervical and lumbar regions
Where does the spinal cord terminate?
L1/L2
What do the spinal segments correspond with?
Each vertebra has a corresponding spinal segment
What do spinal segments give rise to?
Pair of spinal nerves
What are spinal nerves formed from?
Dorsal and ventral roots
What is the DRG?
Dorsal root ganglia
Contains sensory nerve cell bodies
Where are DRG found?
Hidden between vertebrae
What is the character of most peripheral nerves?
Mixed (both sensory and motor)
What is a dermatome?
Region of the body innervated by a bilateral pair of dorsal root ganglia
What are ventricles?
Hollow sections of brain that contain CSF
List the ventricles found in the human brain?
2 x lateral ventricles
1 third ventricle
1 fourth ventricle
Cerebral aqueduct
Where is CSF formed?
Formed by vascular choroid plexus in ventricles
Describe the flow of CSF?
Formed in ventricles > flows out at fourth ventricle > bathes brain
What is the function of CSF?
Bathes brain and acts as shock absorber
List the meninges of the brain?
Dura mater
Arachnoid mater
Pia mater
Describe the morphology of the three layers of meninges?
Dura - thick
Arachnoid - fibrous
Pia - thin
Where does the CSF lie as it bathes the brain?
Sub-arachnoid space
What does the sub-arachnoid space contain?
CSF
How is CSF resorbed?
Resorbed by major veins in sub-arachnoid space
What is the falx?
Extension of meninges that divides cerebral hemispheres
What is the tentorium?
Extension of meninges that separates cerebellum and occipital lobe
What is the function of the blood brain barrier?
Limits free access of material in the blood to the brain
So, protects ECF of brain
What is the blood brain barrier formed by?
Endothelial cells of capillaries with very tight junctions
What type of transport is required for substances to access the brain?
Active transport
