Lecture 8 NS - Organisation of CNS 2 Flashcards
What is the structure of the brain?
What are the functions of the brainstem?
Controls vital functions -> cardio and resp, cranial nerves provide sensory and motor innervation to the head, ascending and descending pathways connect the spinal cord with the forebrain (as conduit)
Where do the cranial nerves innervate?
Facial area
What is the reticular activating system?
Controls level of consciousness -> ^ levels = ^ conciousness
What are the functions of the cerebellum?
Coordinates movement -> monitors immediate area and modifies movement; and is involved in learning motor skills
What are the functions of the diencephalon?
Contains several nuclei with different functions -> Thalamus: acts as relay station for the cerebral cortex; hypothalamus: coordinates homeostatic mechanisms
What are the functions of the cerebral hemispheres?
Basal ganglia [core] -> involved in control of movement; cerebral cortex [outside] -> involved in all functions; corpus callosum -> interconnects corresponding parts of 2 hemispheres across midline
What are sulci?
Crevices between folds in cortex
How are the cortical lobes separated?
By the sulci:
What does each sulci separate?
Central sulci -> frontal/parietal. Parieto-occipital -> parietal/occipital Lateral sulcus -> Frontal/temporal
What are the different functional cortical areas?
MOTOR: Top -> lower limb; bottom -> head so little man lying up and down. SENSORY: Top -> lower limb, bottom -> head, so another little man. Primary auditory cortex -> for hearing, visual cortex for seeing. White areas are for learning, decision making -> association
What are Wernicke’s and Broca’s areas used for?
Wernicke’s understanding language and comprehension; Broca’s for forming speech (tend to be dominant in left hemisphere)
What is contained in the ventricular system?
CSF
What is the lateral ventrical associated with?
The middle of the lobes -> communicate with the 3rd ventricle
What is the third ventricle associated with?
Bisects the diencephalon
What does the aqueduct go through?
Goes through the midbrain
What does the 4th ventricle go through?
Through the pons
What does the central canal go through?
Goes through the medulla, which then continues into the spinal cord
What does the choroid plexus do and where is it located?
Inside the ventricles -> vascular gland which filters blood and changes the ionic content of blood and produces CSF
What does the CSF in the meninges do?
Protects the brain from bumping into the skull
Where does the CSF flow from?
Circulates through ventricular system and subarachnoid space between meninges
How is CSF reabsorbed from the brain?
Reabsorbed via arachnoid villi into venous sinuses
What is CSF?
Secreted by choroid plexus in ventricles, differs from blood in cellular and ionic content
What are the three membranes from outer to inner present in between the skull and the brain?
Dura mater - very tough connective tissue membrane, stuck onto inside of bone; Arachnoid mater - much finer membrane; Pia membrane - attached to surface of cortex, very thin
What structure lies in the anterior cranial fossa?
Frontal lobe of cerebral hemisphere
What structure lies in the middle cranial fossa?
Temporal lobe of cerebral hemisphere
What structure lies in the posterior cranial fossa?
Cerebellum
What structure lies directly above the body of the sphenoid bone?
Hypothalamus
What structure passes through the foramen magnum?
Medulla
What part of the ventricular system relates to the cerebral hemisphere?
Lateral ventricle
What part of the ventricular system relates to the diencephalon?
Third ventricle
What part of the ventricular system relates to the midbrain?
Aqueduct
What part of the ventricular system relates to the pons and medulla?
Fourth ventricle
What is the function of the dorsal and ventral horn?
Ventral: contains motoneurone cell bodies. Dorsal: contains interneurones which receive sensory information from the body
How does the flow of information work in the dorsal and ventral horn?
Towards the spinal cord in dorsal root and away from spinal cord in ventral root and both ways in the spinal nerve
How does the composition of CSF differ from blood?
Normally contains few cells, much less protein, reduced concentration of K+ and Ca2+, higher concentration of Mg2+ and Cl-
What are the 2 main types of hydrocephalus and their causes?
Communicating (4 ventricles) and non-communicating (not all ventricles)
What are the causes of communicating hydrocephalus?
Block in CSF absorption/flow over brain surface caused by: meningitis, head injury, congenital, haemorrhage (sub-arachnoid)
What are the causes of non-communicating hydrocephalus?
Block in ventricular system caused by: aqueduct stenosis, ventricular tumours, paraventricular tumours
What are main signs and symptoms of hydrocephalus?
Headache, Drowsiness, Blackouts, Raised intracranial pressure, Increased head circumference (in child)
What are epidural/extradural haemorrhages?
Usually due to damaged meningeal artery between skull and the dura after head trauma
What are subdural haemorrhages?
Usually due to a damaged vein between the dura and arachnoid membrane
How can you distinguish between an epidural and subdural haemorrhage?
The first symptoms (headache, drowsiness, vomiting or seizure) are likely to arise promptly after arterial bleeding in an epidural haemorrhage whereas symptoms may be delayed by hours or days after venous bleeding in a subdural haemorrhage. -> confirm with imaging
What are the structures usually infected in meningitis?
Pia mater and subarachnoid space, with some spread to the upper layers of the cortex in severe cases.
What is the structure of the meninges?
