L1 (Neuroscience) General Structure of the CNS Flashcards
What are the CNS and PNS made up of?
CNS = brain + spinal cord, PNS = nerves + ganglia
What structures make up the brain stem?
Midbrain, pons and medulla
What does white & grey matter consist of?
White = axons + glia, grey = cell bodies (neural somata) + glia
What is the basic gross structure of the cerebrum?
Two hemisphere split by a longitudinal fissure, surface is the cortex. Cortex has ridges (gyri/gyrus) and grooves (sulci/sulcus)
What are the lobes of the cerebral cortex and what is there functional significance?
4 lobes; Frontal, parietal, temporal and occipital. Boundaries between lobes are not generally functionally significant. Boundaries between frontal & parietal lobes (central sulcus) and temporal and occipital lobes do respect function
What is Brodmann’s Map (Areas) and what is its significance?
Mapping of cortex based on minute cellular differences - 52 areas. Areas often overlap with function (functionally significant) but not always
Describe the cellular structure of the cerebral cortex
Superficial layer of grey matter (~1cm thick) covers the core white matter, wrapping around gyri and sulci. There are many neurons and they are in a layered structure (6 layers), with each layer containing different types of neurons (includes pyramidal and interneurons). The left and right cortices/hemispheres are linked at the corpus callosum
What is the basic function of the cerebellum?
Key element in motor control, compares what you want to do with what you are doing - refines execution of motor program. Contains more than half the neurons of the brain
What parts of the brain develop from the forebrain, midbrain & hindbrain?
The hindbrain = lower brainstem and cerebellum
The midbrain = the most rostral part of the brainstem
The forebrain = (region just rostral to the midbrain) forms the diencephalon which is surrounded by the telencephalon. Diencephalon + telencephalon = the cerebrum (All cerebral cortex is telencephalic)
What makes up the diencephalon?
Thalamus & hypothalamus
What is the telencephalon?
Cortex of the cerebrum
What is the Basal Ganglia?
Group of interconnected sub-cortical nuclei (predominately found in the telencephalon but some between midbrain & hypothalamus) that are arranged around the thalamus.
- Corpus striatum (caudate & putamen)
- Globus pallidus
- Substantia Nigra
- Subthalamic nucleus
What is the function of the basal ganglia?
Important in motor control - selects & initiates voluntary movements –> sends information to the cortex
What are diseases of the basal ganglia?
Sends information to the motor cortex - therefore motor disorders. Parkinson’s & Huntington’s Disease
What is the function of the thalamus?
Major sensory relay to cortex –> allows you to perceive
Where is the thalamus found?
Part of the diencephalon with the hypothalamus. Sits in the middle of the brain
What are the 3 pathways of thalamic sub-nuceli?
- Sensory information –> specific areas of cortex
- Non-sensory info from cortex & basal ganglia –> areas of cortex
- Project globally to cortex –> arousal & sleep
What is the function of the hypothalamus?
Central command centre for regulating homeostatic functions (i.e. temperature, blood volume, pH…)
Controls the pituitary gland (sits below it)
What does the brainstem control?
- Facial muscles
- Sensation from head and face
- Cardiorespiratory control
- Arousal, sleep/wake cycle
Describe the anatomy of the spinal cord?
Core of grey matter, surrounded by white matter (opposite to cortex)
Grey matter has ventral (anterior) and dorsal (posterior) horns that are separated by an intermediate zone.
What are the functions of the dorsal and ventral horns of the spinal cord?
Dorsal (posterior) - sensory input
Ventral (anterior) - motor output
What are the divisions of the spinal cord?
Cervical, thoracic, lumbar and sacral
The amount of white matter varies depending on the region
At what spinal level does the spinal cord end?
L1/L2
The vertebral column continues and the lower spinal nerves continue through the column, exiting at their respective intervertebral foramen
What is the typical organisation of a spinal nerve?
- Each spinal nerve formed by ventral and dorsal roots
- Sensory axons form dorsal root, motor axons from the ventral horn
- Ventral root motor neuron cell bodies are in the ventral horn
- Dorsal root ganglia contains sensory neuron cell bodies and axons project into dorsal horn
What is the dorsal root ganglion & its structure?
- Sensory neurone cell bodies, located between vertebra, before dorsal root
- Part of the PNS
- DRG neurons have branching axons
- One axon in peripheral nerve - detects stimulus (afferent fibre)
- One axon runs in dorsal root to the dorsal horn
What are the ventricles of the brain?
2 x lateral and a 3rd 4th ventricle and cerebral aquaduct
What is the purpose of the ventricular system?
- Contains CSF fluid and circulates it through the brain (flows out at 4th ventricle into the central canal of the spinal cord)
- CSF fluid important for buoyancy of the brain and shock absorption
What produces the CSF?
- Choroid plexus which is present within the ventricles
- Constantly being produced
What are the layers of the meninges?
- Dura (thickest, outer)
- Arachnoid (fibrous, middle)
- Pia (thinnest, innermost)
What is an important pharmacological property affecting the ability of drugs to cross the blood brain barrier?
Lipid solubility - increased lipid solubility allows drugs to cross the BBB
