Neuro 6 - Organisation of the CNS Flashcards
How many paris of nerves emerge from the CNS?
31 pairs
Equal number of nuerves for each vertebra except extra nerve above C1 so 8 cervical nerves, 7 verterbrae
C1 is above C1 so C8 above T1 and under C7
T1 under T1
Thoracic - 12
Lumbar - 5
How is the spinal cord protected, where does it lie?
Protected by vertebrae
Lies in vertebral canal
Series of holes alongside vertebrae –> intervertebral foramina –> where nerves come out
What is the structure called cauda equina?
cauda is a “tail”
It is when the spinal cord is shorter than the vertebral column so the nerves emerge from it and form a nerve tail
Where can CSF fluid be sampled?
L3/L4
or L4/L5
What is the name of the area inside the vertebral canal beneath the point at which the spinal cord ends?
Lumbar cistern ("tank")
Where you find the cauda equinaWhat is the difference between the dorsal horns and the ventral horns?
Dorsal -> sensory (has dorsal ganglion) - in from dorsal route
Ventral -> motor - out from ventral route
What is the difference between the white and grey matter?
White matter -> myelinated fibres - go up and down
Grey matter -> neuronal cell bodies, glial cells, unmyelinated fibres
Myelin is WHITE
What are the functions of the spinal cord?
- connects PNS and ANS to the brain
- carries sensory signal to the brain
- carries motor signals to the muscles
- coordinates reflexes - information processed at the spinal cord level
What structure connects the right and left hemispheres?
Corpus callosum
What lies beneath the corpus callosum?
Diaencephalon ie. thalamus + hypothalamus
What are the two parts of the diencephalon and what is their function?
Thalamus - relay station for information going between the cerebral cortex and other areas of the CNS. Somatic and special senses, emotional, consciousness
Hypothalamus - integration hub - important in coordinating homeostasis (hypothalamo-hypophysial axis)
Thalamus is above hypothalamus
–> know everything that is going on in body, however, to make sense of it needs cortex
What are the two classifications of the brain?
—>Based on embryonic development:
It initially developed as the forebrain, midbrain and hindbrain.
The forebrain became the cerebral cortex and diencephalon
The midbrain remained as the midbrain (part in between diencephalon and pons)
The hindbrain became the pons, medulla and cerebellum
—>Other classification:
Brainstem -> Midbrain + pons + medulla
Cerebrum -> hemispheres + diencephalon
Cerebellum
What composes the brainstem?
Midbrain
Pons
Medulla
All sensory and motor fibres that connect the cerebrum, cerebellum and spinal cord run through it
Continuation of spinal cord (medulla still has its structure but enlarged)
What makes the pons recognisable?
It bulges anteriorly
What is the function of the brainstem?
Control of many vital functions such as breathing, HR, BP, swallowing, balance, etc.
Defensive reflexes, sleep-wake cycles, alertness, consciousness
NOTE
Lesion of the brainstem can lead to locked-in syndrome
Midbrain includes substantia nigra which degenerates in Parkinson’s
What composes the cerebral hemispheres?
Cortex + basal ganglia
It is on right and left lateral sides of diencephalon.
Looks like a funny structure
What composes the basal ganglia?
Caudate Putamen Globus pallidus Subthalamic nucleus Substantia nigra
Caudate + putamen = corpus striatum (because of ‘stripy’ connection)
Globus Pallidus + putamen = Lentiform nucleus
What is the function of the basal ganglia?
Control of movement - “fine tuning” - facilitating voluntary movement, inhibiting unwanted or inappropriate movements
What are the two types of cortex?
Primary Cortical Area (primary cortex) - main part
Association Cortex - where info of primary cortex is made sense of
Usually like primary motor cortex then motor association area
What is gyri and sucli?
How the cortex is organised
Gyri - top of the invagination
Sulci - invagination
Describe the arrangement of the primary motor cortex and the primary somatosensory cortex.
They both have somatotopic arrangement - like a little man standing upside down
What is the function of the association cortex?
The association cortex is involved in higher functions e.g. learning, perception, thinking
What is the role of Wernicke’s Area and Broca’s Area?
Wenicke’s Area - understanding language
Broca’s Area – speech
How many layers does the cortex have?
Usually 6
What is the limbic system? what one structure is important?
Hippocampus - cortex rolled up on itself - memory, learning, alzheimer’s
Consists of amygdala, olfactory bulbs..
Function - motivation, instinctive behaviour, emotion, memory
What is the role of the cerebellum?
Coordinates complex somatic motor patterns
Adjust output of other somatic motor centers in brain and spinal cord
–> fine tuning motor function
What are the three types of fibres in the brain?
- Commisural (corpus callosum) - crosses
- Association fibers - in between cortical areas, within hemisphere
- Projection fibers - from the cortex down to spinal cord
Corona radiata is a structure seen pf fibers that spread out of cortex from the base and form a sort of fan
How many bones compose the cranium?
6 bones - frontal, sphenoid, temporal, parietal, occipital, ethmoid
Holes for vessels
Foramen magnum for spinal cord
Lots of fossa like sella turcica
What are the layers of the meninges?
Dura mater (periostal + meningeal)
Arachnoid mater
Pia mater
between the brain and the bone = meninges
Between arachnoid and pia CSF can circulate in sub arachnoid space
Describe the ventricular system of the brain.
There are two large C shaped ventricles called lateral ventricles. There is one lateral ventricle for each cerebral hemisphere.
The lateral ventricles narrow and form the 3rd ventricle, which is in the diencephalon (looks like bird head).
The 3rd ventricle narrows to form the cerebral aqueduct, which passes down through the midbrain and becomes a tent-shaped structure called the 4th ventricle.
The 4th ventricle is behind the pons and medulla and in front of the cerebellum.
The 4th ventricle then narrows to form the central canal, which runs down the spinal cord.
Where is cerebrospinal fluid produced?
By the choroid plexus, which is a special type of ependymal cell found in the ventricles.
Where does CSF leave the ventricles and enter the subarachnoid space?
CSF leaves the ventricles in the 4th ventricle, which has small holes in it
How is CSF reabsorbed into the venous system?
CSF is reabsorbed into the venous system by arachnoid villi = membrane invagination of the arachnoid mater
What separates the temporal lobe from the other lobes?
Lateral Sulcus
What is the role of CSF?
Metabolic function - remove waste
Cushioning
Nutrition
Immune cells
Composition similar to plasma but much lower protein, lower glucose, lower Ca2+, higher Cl-
Define hydrocephalus and explain treatment
= increase in CSF volume
Communicating hydrocephalus (all 4 ventricles affected) is caused by block in CSF absorption: Meningitis Head injury Congenital Sub-arachnoid haemorrhage
Non communicating hydrocephalus (not all affected) is caused by block in ventricular system:
Aqueduct stenosis
Ventricular tumour
Compare the clinical presentation of epidural (extradural) and subdural haemorrhage
Epidural haemorrhage:
Arterial bleeding
Symptoms of headache, drowsiness, vomiting or seizure arise promptly after injury
Subdural haemorrhage:
Venous bleeding
Symptoms delayed by days or weeks
