LAB 2: BRAIN Flashcards
What are the four major parts of the brain and where are they located
1.Brain stem- continuous with the spinal cord
and contains medulla oblongata, pons and midbrain.
2. Cerebellum- posterior to the brain stem
3. Diencephalan (hypothalamus, thalamus and epithalamus) and is superior to the brain stem
4. Cerebrum- largest part supported on the brain stem
What are main 2 the protective coverings of the brain
Cranium (cranial bone) and cranial meninges surround and protect the brain.
Describe the three layers of the cranial meninges; outside to inside, number of layers
Outside to inside: Dura, Arachnoid and Pia as continuous with the spinal cord but Dura mater has 2 layers: periosteal layer (external)and meningeal layer (internal). These two layers are fused together except when they separate to enclose dural venous sinuses that drain venous blood from the brain and take it back t the jugular veins.
Whats the difference between spinal meninges and cranial meninges
Spinal meninges only have one dura mater layer. Cranial meninges don’t have epidural space.
What are the three maters that separate which parts of the brain and which meningeal layer is it made of
Falx cerebri: separates two hemispheres of cerebrum
Falx cerebelli: separates two hemispheres of cerebellum
Tentorium cerebelli: separates the cerebrum from the cerebellum.
All made from extensions of dura mater
What is cerebrospinal fluid mainly made of and what space does it fill
clear colourless fluid made of water with small amounts of glucose and other nutirients such as ions, amino acids and some white blood cells. It fills the sub arachnoid space
What are the CSF filled cavities within the brain and where are they positioned
There are four ventricles. One lateral ventricle in each hemisphere of the cerebrum which are separated anteriorly by the septum pellucidum- thin membrane. The 3rd ventricle is a slit like cavity between the right and left halves of the thalamus along the midline and above the hypothalamus.
The 4th ventricle is between the brainstem and cerebellum
What is the mechanical protection function of CSF
- Mechanical protection: Absorbs shock stopping delicate brain tissue hitting the bony wall of the cavity and also buoys the brain
What is the homeostatic function of CSF
- Homeostatic function: A transport system for hormones secreted by hypothalamic neurons that act at remote sites of the brain. Homeostatic controls for cerebral blood flow and pulmonary ventilation are affected by the pH of CSF
What is the circulation function of CSF
It continually circulates and is a medium for minor exchange of nutrients and waste products between the blood and adjacent nervous tissue.
Where is CSF made from
water and other substances from the blood plasma of the Choroid plexuses blood capillaries in the ventricle walls, which are covered by ependymal cells. Tight junctions between these cells means that a blood- cerebrospinal fluid barrier is set up and any substances have to pass through the ependymal cells, not leak between them.
What is the function of the blood- cerebrospinal fluid barrier and how different to blood brain barrier
It stops harmful substances from getting into CSF so brain and spinal cord are protected. The blood-cerebrospinal fluid barrier is bidirectional, allowing transferrence of metabolites back to the blood. Formed by tight junctions of ependymal cells whereas blood brain barrier is by tight junctions brain capillary endothelial cells.
Describe the path of circulation of CSF through lateral ventricle, third ventricle, fourth ventricle, subarachnoid space + central canal
CSF from lateral ventricles flows through interventrical foramina to third ventricle. Then it flows through aqueduct of midbrain to fourth ventricle. Then goes to the subarachnoid space through the median, and two lateral apertures. There is circulates in the central canal and subarachnoid space around the surface of the brain and spinal cord.
Where is the CSF reabsorbed into the blood and what is the rate of reabsorption
Arachnoid villi- extensions of arachnoid mater that project into the dural venous sinuses. Normally rate of absorption is same as formation so pressure + volume is constant
What are the functions of the left hemisphere
- Somatic sensory information from and controls muscles from the right side of the body.
- Reasoning, numerical and scientific skills.
- Ability to use and understand sign language, spoken and written language.
