Central Nervous System Flashcards
Layers of the scalp
Skin Connective tissue Aponeurosis Loose areolar tissue Periosteum
Divisions of nervous system
PNS and CNS
PNS
→ Cranial nerves
→ Spinal nerves
CNS
→ Brain
→ Spinal cord
(Processing sensory data and sending motor commands
Higher functions such as intelligence, memory, learning and emotion)
Divisions of PNS
PNS
→ Somatic nervous system
→ Autonomic nervous system
→ Parasympathetic/Enteric/Sympathetic
Parasympathetic vs Sympathetic
What connects the 2 cerebral hemispheres?
Corpus callosum
What increases surface area on the brain surface?
Highly convoluted: to increase surface area
Gyri (gyrus, singular): convolutions
Sulci (sulcus, singular): Creases
Location of grey and white matter in the brain
What are the different lobes of the brain and their function?
Temporal Frontal Parietal Cerebellum Occipital
Longitudinal fissure (between the two cerebral hemispheres)
Cerebellum
The cerebellum is concerned with balance, muscular co-ordination and dexterity
- Outer layer of grey matter
- Inner layer of white matter
- Highly convoluted
Brainstem
The brain stem is critical for normal conscious awareness and basic “life support” functions (e.g. control of breathing and blood pressure).
Contains ascending and descending nerve fibre tracts linking brain to spinal cord
Receives sensory and motor information from trunk and limbs
Spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column.
It terminates approximately at the level of L1, from there a series of spinal nerves branch off to form a structure called “cauda equina”, which means “horse’s tail”
Describe the meninges
The meninges form a protective barrier that safeguards the sensitive organs of the central nervous system. They contain blood vessels that deliver blood to the brain and they produce cerebrospinal fluid. This fluid protects and nourishes the brain tissue by acting as a shock absorber, by circulating nutrients, and by getting rid of waste products.
Dura Mater
The dura mater is the outermost layer. Located between the periosteal and meningeal dura mater are channels called dura venous sinuses. These venous sinuses drain blood from the brain to the internal jugular veins, where it is returned to the heart.
Arachnoid Mater
The arachnoid mater is the layer underneath the dura. The subarachnoid space contains arachnoid trabeculae, which connect the pia with the arachnoid. In between the trabeculae there are blood vessels and nerves that supply the brain. The subarachnoid space also contains cerebrospinal fluid (CSF). Arachnoid granulations are extensions of the arachnoid mater into the dura mater. The CSF flows from the granulations into the dura, to be reabsorbed in the dural sinuses.
Pia mater
The pia mater is the inner layer that cover the brain. The pia mater has a rich supply of blood vessels, which provide nutrients to nervous tissue.
Lumbar puncture
A needle is inserted into the spinal canal, most commonly to collect cerebrospinal fluid (CSF) for diagnostic testing.
A needle is used to collect a sample of cerebrospinal fluid from the subarachnoid space (at the level of iliac crest- between L3 and L4)
MUST AVOID SPINAL CORD
The inner layer of dura expands internally to form a series of partitions that separate portions of the brain.
Dural venous sinuses
The dural venous sinuses arevenous channels found between the endosteal and meningeal layers of dura mater. They receive the venous blood drainage of the brain and transport it into the internal jugular vein.
Ventricular system
The ventricles of the brain are a communicating network of cavities, continuous with the subarachnoid space. The ventricular system is composed of two lateral ventricles, the third ventricle, the cerebral aqueduct, and the fourth ventricle below.
The choroid plexuses are located in the ventricles and produce CSF, which fills the ventricles and subarachnoid space, following a cycle of constant production and reabsorption.
CSF circulation and reabsorption
What causes hydrocephaly?
Hydrocephaly isthe buildup of fluid in the cavities (ventricles) deep within the brain.
It can be caused by a blockage within the ventricular system, i.e. cerebral aqueduct as it is the narrowest opening, or a reduced rate of reabsorption of CSF
Hydrocephaly is a chronic condition. It can be controlled,but usually not cured. With appropriate early treatment, however, many people with hydrocephalus lead normal lives with few limitations. Hydrocephaly can occur at any age, but is most common in infants.
Blood brain barrier
The blood–brain barrier (BBB) is a term used to describe the unique properties of the blood vasculature of the central nervous system (CNS). CNS blood vessels are continuous non-fenestrated vessels held together by tight junctions, that allow them to tightly regulate the movement of molecules, ions, and cells between the blood and the CNS, as well as protect the CNS from toxins, pathogens, inflammation, injury, and disease.
Astrocytes are cells that provide a cellular link between the neuronal circuitry and the blood vessels of the brain. They are connected both to the epithelium of the blood vessels and to the neurons. This neurovascular coupling enables astrocytes to relay signals that regulate blood flow in response to neuronal activity.
Where does all blood in the brain eventually drain into?
Internal jugular vein
Where is CSF formed?
Choroid plexus
by ependymal cells
What is the journey of CSF?
From lateral ventricles to foramen of Monroe and then goes to 3rd ventricle
Then cerebral aqueduct to 4th ventricle
What structure sits posterior to 4th ventricle?
Cerebellum
Divisions of lateral ventricles
What is obstructive hydrocephalus and how does it differ from cerebral oedema?
Obstructive hydrocephalus: blockage of CSF drainage pathway - causes dilation of part of the ventricular system above the occlusion
Cerebral oedema: increase in brain water content - causes generalised brain swelling
BOTH may lead to increased ICP
Patient has dilation of left lateral ventricle only, where is the lesion?
Left interventricular foramen of Monroe
could be due to colloid cyst
jelly like core within epithelial membrane
Where is CSF reabsorbed into venous system?
Arachnoid granulations in dural venous sinuses
Esp superior sagittal sinus
What artery supplies the pink region?
Middle cerebral artery (supplies convexity of brain)
Man has a head injury and craniotomy performed. The sigmoid sinus is bleeding profusely, into which structures does it drain?
Internal jugular vein
Language areas of brain
Broca’s area- main cortical language area in inferior frontal gyrus (motor language so producing speech)
Wernicke’s area- in superior temporal gyrus, sensory aspect so recognition of speech sounds and understanding
What connects Broca’s and Wernicke’s areas?
Arcuate Fasiculus
Lesion in Wernicke’s vs Broca’s area
Lesion in Broca’s: non fluent dysphagia, speech difficult and slow, can’t get words out
Lesion in Wernicke’s: fluent dysphagia, speak fluently but with no sense and neologisms (simlish)
Where does spinal cord end?
L1-L2
Conus Medullaris
Vertebral level for lumbar puncture?
L4-L5
Epidural vs Subdural haematoma
Bleed in the brain
Epidural- outside of dura
Subdural- underneath dura
Where does brain stem exit the skull?
Foramen Magnum
