10 - Gross anatomy of the brain II Flashcards
What is the corpus callosum?
Myelinated axons that form a horizontal pathway between the two cerebral hemispheres
What are the corona radiata?
Vertical fibres that run from the cerebral cortex to the inner brain, through the internal capsule
What is the lentiform?
- putamen
- globus paladium
Describe the internal capsule.
- made up of the anterior limb, genu (knee) and posterior limb
- forms V shape around the lentiform
What are the basal nuclei?
- corpus striatum
- substantia nigra
- subthalamic nucleus
Describe the role of basal nuclei.
- primarily involved in motor control
- filter out incorrect responses and pass the best option to the cortex (ie prevent tremor)
What is a pathology that can affect the basal nuclei?
- Parkinsons, tremor, movements are shaky due to responses not being filtered out correctly
- Huntingtons, jerky movements due to a lack of fine tuning by basal nuclei
Describe the hypothalamus.
- neuro-endocrine organ
- sits anterior and inferior to thalamus (hypo = under)
- involved in homeostasis (ie need for food, reproduction, growth etc)
Describe the function of the hypothalamus.
- monitors internal environment (ie blood glucose or temperature)
- controls autonomic systems
- controls release of hormones from pituitary via releasing hormones in the pituitary stalk
Describe the pituitary gland.
- continuous inferiorly with the hypothalamus via the pituitary stalk
- regulates hormone release by releasing or inhibiting hormones
Give examples of hormones released by the pituitary gland.
- growth hormone
- thyroid stimulating hormone
- follicle stimulating hormone
- adrenocorticotrophic hormone
- lutenisng hormone
- prolactin
What is the cause of acromegaly?
- over production of GH
- often caused by a pituitary tumour
What are some signs and symptoms of acromegaly?
- growth of hands and feet
- lips, nose and tongue become larger
- voice becomes deeper
- jaw becomes larger, leads to spacing in teeth
What can acromegaly cause if untreated?
- hypertension
- diabetes
- sleep apnoea
What is the ventricular system?
- ventricles in the brain, filled with CSF that provide protection of the brain
- produce and circulate CSF
- 4 ventricles in total
How is CSF produced?
Chorodial epithelial cells located in each ventricle produce 400-500ml of CSF per day.
What is the role of CSF?
- protect the brain
- prevents the weight of the brain from crushing vessels and nerves in the subarachnoid space
What are the ventricles?
- 2 lateral ventricles (separated by the septum pellucidum)
- 2 midline ventricles (3rd and 4th)
What is the choroid plexus?
Produces CSF
What is the cerebral aqueduct?
Connects 3rd and 4th ventricles
What is the septum pelluicidum?
Separates the lateral ventricles
What is the inter ventricular foramen?
- aka Foramen of Munro
- connects lateral ventricles with 3rd ventricle
What is the cistema magna?
Subarachnoid space found at the base of the cerebellum, caused by differences in the size of the arachnoid and pia.
Describe the circulation of the CSF.
- secreted by chorodial cells
- lateral ventricles to 3rd to 4th
- CSF leaves 4th ventricle via lateral apertures to circulate through the subarachnoid spaces
- reabsorbed into venous sinuses
What makes up the brainstem?
- midbrain
- pons
- medulla
What is the function of the brainstem?
- connection between cerebrum, cerebellum and spinal cord
- contains many nuclei and neuronal tracts
- where the cranial nerves exit the brain
- houses nuclei of CN 3-10 and 12
- reflex centres for respiration, CV and regulates consciousness
What is the decussation of pyramids?
Where the neuronal tracts cross from one side to the other
Describe the spinal cord.
- begins at medulla, ends at L1/L2 vertebrae
- cylindrical except for enlargements
What is the conus medullaris?
Inferior end of the spinal cord
Describe the filum terminale.
- pia mater
- anchors spinal cord
- inferior continuation of conus medullaris
- silver fibre
Describe the cervical enlargement.
- C4-T1
- contributes to the brachial plexus
- supports upper limbs
Describe the lumbosacral enlargement.
- T11- S1
- contributes to lumbosacral plexus
- supports lower limbs
Describe the lumbar cistern.
- subarachnoid space
- extends from L1/L2 to end of dural sheath at S2
Describe the cauda equina.
Long nerve fibres suspended in CSF at the level of L2-S1
Define dorsal.
Posterior
Define ventral.
Anterior
Describe the ventral horn.
Efferent motor
Describe the dorsal horn.
Afferent sensory
Describe the structure of spinal nerves.
- rootlets emerge from the dorsal and ventral horns
- rootlets converge laterally to become roots
- the motor and sensory root converge to form a spinal nerve
- after exiting the vertebral column the spinal nerve splits into anterior and posterior rami
How are spinal nerves named?
- numbered according to the vertebra above
- except for the cervical nerves (due to there being 8 cervical nerves, named as the vertebra below)
What are the layers involved in protection of the spinal cord?
- pia mater
- arachnoid mater
- dura mater
Describe the denticulate ligament.
- formed by pia mater
- travels through arachnoid mater to attach to dura
- provides horizontal stability
Describe the dura mater in the spinal cord.
- epidural space is normal in the spinal cord (unlike brain - this pathology)
- epidural space filled with fat to protect cord from the vertebra
Define a myotome.
Muscle supplied by a specific, spinal nerve
Define a dermatome.
Skin supplied by a specific, spinal nerve
Which spinal nerve does not have a dermatome?
C1 (lacks afferent fibres)
