Brain + associated structures

• clinical relevance:

  
  

  describe a CSF Rhinorrhea


  - A fracture of the sinuses or cribriform plate may result in a condition termed CSF rhinorrhea

  - The result of a disruption to the skull, subarachnoid and dura can lead to the the CSF- containing subarachnoid space coming into direct contact with the nasal mucosae
• clinical relevance:

  
  

  describe a Subarachnoid haemorrhage

  - Any haemorrhage that occurs in the space between the arachnoid and the pia mater is termed subarachnoid

  - Most likely the result of an aneurysm

  - Likely symptoms are sight problems, pain (face) or headaches. But it can also be fatal

  
• clinical relevance:

  
  

  describe a Extradural or Epidural haemorrhage


  - Trauma to the skull can in turn lead to an epidural haemorrhage, i.e. between the dura and the skull

  - The bleed is often the result of rupture to the middle meningeal artery

  
• clinical relevance:

  
  

  describe a subdural haemorrhage


  - Rupture to the veins located in the subdural space can lead to a build up of

  blood between the dura mater and the arachnoid

  - This is referred to as subdural ('under the dura') haemorrhage and if it compresses the brain then it can be life- threatening

  - Other symptoms are loss of consciousness or paralysis

  - Also, it can be either acute or chronic

  
• cranial venous sinuses

  
  

  what is the clinical significance of the cranial venous sinuses in terms of the spread if infection?

  Because of a lack of valves along the veins of face, the cavernous sinus infections can easily spread from teeth,

  eye or nose, leading to cavernous sinus thrombosis. This was often fatal prior to the use of penicillin
• cranial venous sinuses: cavernous sinus

  
  

  what does the cavernous sinus contain?

  The contents of the cavernous sinus can be easily remembered with the mnemonic Oh, COAT, that stands for:

  
  

  Oculmotor nerve (III)

  (internal) Carotid artery

  Ophthalmic nerve (V1)

  Abducens nerve (VI)

  Trochlear nerve (IV).

  
• cranial venous sinuses: cavernous sinus

  
  

  what is the cavernous sinus?


  The cavernous sinus is part of the brain's dural venous sinus and contains multiple neuro-vasculatures

  
  

  - The cavernous sinus gets blood from the eye region, among others, and drain into the petrosal sinuses (superior and inferior) which in turn drain into the internal jugular

  
• cranial venous sinuses

  
  

  Where does blood in the venous sinuses originate and where does it drain?

  Originates mostly from the brain & cranial cavity and drains via the internal jugular vein

  
• cranial venous sinuses

  
  

  Are there valves in the cranial venous sinuses?

  no
• cranial venous sinuses

  
  

  what are the cranial venous sinuses?

  also known as the dural venous sinuses

  -> Spaces between periosteal & meningeal layers of dura mater containing venous blood

  
  

  (the dura mater is one of the layers of connective tissue that make up the meninges of the brain)

  
• Meninges

  
  

  what are examples of meningeal partitions?

  ---------Falx cerebri

  - The partition between the two cerebral hemispheres, i.e. in the longitudinal fissure.

  - The term 'Falx' (Latin for sickle) is derived from the fact that this partition is narrow at the front where it attaches to the crista galli of the ethmoid and broad behind, where it

  connects to the upper surface of the tentorium cerebelli

  - The upper margin of the falx cerebri is attached to the inner surface of the skull, leaving a gap that forms the superior sagittal sinus

  - The lower margin has a free edge and encloses the inferior sagittal sinus

  
  

  ---------Falx cerebelli

  - The partition between the cerebellar hemispheres, whereby a short process of dura mater projects from the internal occipital crest below the tentorium and bifurcates into two, passing on either side of foramen magnum

  
  

  ---------Tentorium cerebelli

  - as the name translates to, sits as the roof of the cerebellum

  - this partition sits between the occipital lobes and cerebellar

  hemispheres, with an opening surrounding the brainstem
• Meninges

  
  

  what is the function of the meningeal partitions?

  These projections serve the purpose of ensuring that the brain moves alongside the skull, since the brain is not otherwise anchored to the bony skull, being essentially surrounded by CSF
• Meninges

  
  

  what are the meningeal partitions?

  when the meningeal layers project from under the surface into the intracranial region.

  
• Meninges

  
  

  what are the 3 meningeal layers from superficial to deep?

  - dura

  (tough) mater lies immediately below the skull and acts as a

  mechanically protective covering

  
  

  - arachnoid

  (web-like) mater is considerably more delicate and made of

  non-vascular connective tissue

  
  

  - pia

  (intimate) mater is continuous with the surface of brain/spinal cord. It supports the vessels that supply the brain as well as forming the choroid plexus (CSF production), alongside the ependymal cells

  
• Meninges

  
  

  what is the Meninges?


  Three meningeal layers of membranes that protect the brain and spinal cord.

  - formed by collagen

  
• CNS- brain

  white matter: basal ganglia

  
  

  what are the anatomical features of the basal ganglia?

  - Lentiform nucleus gets its name because it is lens-shaped,

  located within the internal and external capsules

  - Caudate nucleus is C-shaped and sits in the wall of lateral

  ventricle

  
• CNS- brain

  white matter: basal ganglia

  
  

  what does the basal ganglia consist of?

  The name given to the collective group of interconnected nuclei located within the subcortical region at the base of forebrain

  
  

  ---> This group consists of the corpus striatum plus the subthalamic nucleus and substantia nigra

  
  

  - The basal ganglia is functionally linked to the motor cortex and thalamus

  
• CNS- brain

  white matter: limbic system

  
  

  describe the limbic system

  occasionally labelled as the 'emotional brain' on account of its recognized role in mediating several processes that lead to an emotional response (e.g. pleasure, pain, anger and associated memories) as well as behaviour, drive and memory

  
• CNS- brain

  white matter: limbic system

  
  

  what is the hippocampus?

  - The hippocampus gets its name from a resemblance to a sea horse

  - This nucleus sits on the floor of the lateral ventricle

  
• CNS- brain

  white matter: limbic system

  
  

  what is the fornix?

  The fornix is a semi-circular white matter tract connecting the

  hippocampus (learning and memory) to the mammillary bodies

  (recollective memory)

  
• CNS- brain

  white matter: limbic system

  
  

  where is the limbic system?


  This network of nuclei extends from the upper portion of the corpus callosum to the floor of the forebrain (diencephalon), that include some of the thalamic subdivisions, mammillary bodies of the hypothalamus, olfactory bulbs, as well as the hippocampus, amygdala and cingulate gyrus

  
• CNS- brain

  white matter: basal ganglia

  
  

  describe the basal ganglia


  It is involved in the control of posture and voluntary movement but also reported to mediate higher cognitive processes such as attention, memory and planning

  
• CNS- brain

  white matter:

  
  

  how are the several nuclei and white matter tracts that are deep within the cerebral hemispheres interconnected?

  via neural networks or systems.

  the two most well-known examples are:

  1- limbic system

  2- basal ganglia
• CNS

  white matter example:

  
  

  what are the capsules?

  - white matter tracts

  - They carry axons that travel vertically or anterior-posterior

  - They are associated with information travelling between the cortex and spinal cord/internal nuclei

  
• CNS

  white matter example:

  
  

  what is the corpus callosum?

  - white matter

  - links the two cerebral hemispheres

  - This tract carries axons that relay information from one hemisphere to the other

  
• CNS

  
  

  what is white matter?


  mainly myelinated axons

  
• CNS

  
  

  what is gray matter?

  mainly neuronal cell bodies

  
• cerebellum

  
  

  functions of cerebellum

  Main functions are of motor control:

  - Control of posture

  - Coordinating and planning limb movements

  - Control of eye movements
• cerebellum

  
  

  where is the cerebellum?

  Located posterior to brainstem its featured are:

  - Outer gray matter

  - Underlying white matter

  - Outer surface reveals two cerebellar hemispheresand three lobes

  - Inner mass also contains nuclei

  
• brain stem

  
  

  what does the brain stem include?

  - Cranial nerves nuclei, within all three regions

  - Vital respiratory and cardiovascular centres

  - Vomiting centre

  - Nuclei involved with motor control, or sleep

  
  

  This includes all the relevant white matter tracts that interlink these nuclei to the rest of the CNS
• brain stem

  
  

  what are the 3 sections of the brain stem?

  - midbrain

  - pons

  - medulla

  
• brain stem

  
  

  what is the brain stem?

  the structure that connects the cerebrum of the brain to the spinal cord and cerebellum.

  
• brain

  
  

  diencephalon: describe the hypothalamus


  - As the name suggests, it is located inferiorly to thalamus

  - Its primary role is the maintenance of homeostasis

  - Specifically, it coordinates ANS and endocrine responses;

  eg: thermoregulation, hunger, thirst, sexual and emotional behaviour

  - Receives inputs from the limbic system

  - Viewing the brain from below, the hypothalamus sits

  between the optic chiasm and mammillary bodies

  
• brain

  
  

  diencephalon: describe the thalamus


  A paired structure, one on each hemisphere

  - Its role is as a relay of sensory information to the cortex

  - Information regarding voluntary movement, personality,

  consciousness or alertness

  
• brain

  
  

  where is the diencephalon?


  - The region of the brain that sits around the third ventricle

  - Its two most prominent constituents are the thalamus and hypothalamus

  - This central location equates to a 'central' role within neuronal networks

  
• brain

  
  

  cerebral cortex: how are motor and sensory functions brought together?


  information is not purely motor or sensory but it is several joined together to produce association/cognition

  
• brain

  
  

  cerebral cortex: what is the occipital lobe associated mostly with?

  visual processing

  
• brain

  
  

  cerebral cortex: what is the temporal lobe associated mostly with?

  auditory processing but also speech, vision and memory

  
• brain

  
  

  cerebral cortex: what is the parietal lobe associated mostly with?

  somatosensory processing

  
• brain

  
  

  cerebral cortex: what is the frontal lobe associated mostly with?

  motor function