Psychobiology part 2 unit 9 Flashcards
Human brain cannot support its own wight?
The human brain cannot even support its own
weight: it is difficult to remove and handle a
brain from a recently deceased human without
damaging it
Question: What role does the cranium play in protecting the brain?
Answer: The cranium acts as a protective shell, shielding the brain from external injury. It provides support and houses foramina for cranial nerves and blood vessels.
Question: Name the three fossae of the cranial floor and their functions.
Anterior fossa: Holds the frontal part of the brain.
Middle fossa: Supports the middle brain.
Posterior fossa: Cradles the cerebellum and brainstem.
what is the Foramen Magnum=
The medulla passes through the foramen
magnum, connecting the brain and spinal
cord
Question: What are the meninges, and what are their layers?
Answer: The meninges are three protective membranes between the cranium and brain:
Dura mater: Tough, outermost layer, forms folds (falx cerebri, tentorium cerebelli).
Arachnoid mater: Spiderweb-like middle layer with the subarachnoid space filled with CSF.
Pia mater: Thin, innermost layer that adheres to the brain’s surface.
What is the role of cerebrospinal fluid (CSF) in brain protection?
CSF acts as a shock absorber against trauma.
It reduces the brain’s effective weight from ~1.4 kg to ~80 g, preventing the brain from collapsing under its own weight.
How does an extradural/epidural haematoma occur?
It is caused by tearing of the middle meningeal artery, leading to bleeding in the extradural/epidural space between the dura mater and cranium.
What happens as an extradural/epidural haematoma progresses?
Bleeding increases pressure in the epidural space, causing brain compression.
This is followed by a coma a few hours after the trauma.
What are the outcomes if an extradural/epidural haematoma is untreated?
Rising intracranial pressure leads to brain displacement and ultimately death without immediate neurosurgery.
Without neurosurgery, the rising pressure in
the brain (intracranial pressure) causes brain
displacement and death
What flows through the subarachnoid space, and what is its function?
The subarachnoid space contains cerebrospinal fluid (CSF), which cushions the brain and spinal cord, protecting against trauma.
Describe the key features of the dura mater.
The dura mater is a tough, fibrous, flexible, yet unstretchable outer membrane that adheres tightly to the cranium and forms folds separating parts of the brain.
What causes meningitis, and what are its symptoms?
Meningitis is inflammation of the meninges caused by infections (viral, bacterial, fungal).
Symptoms include headache, vomiting, light sensitivity, fever, and neck stiffness.
What is an extradural/epidural haematoma, and how does it occur?
Types of Bleeding:
Epidural hematoma: Bleeding between the dura mater and the skull.
Subdural hematoma: Bleeding between the dura mater and arachnoid mater.
It is caused by tearing of the middle meningeal artery, leading to brain compression, coma, and death without treatment.
What is the falx cerebri, and where is it located?
The falx cerebri is a fold of the dura mater that lies in the longitudinal fissure of the brain.
It separates the two cerebral hemispheres.
What is the tentorium cerebelli, and where is it located?
The tentorium cerebelli is a fold of the dura mater that separates the cerebellum from the posterior part of the cerebral hemispheres.
What is the ventricular system, and what is its primary role?
The ventricular system is a network of interconnected cavities in the brain filled with cerebrospinal fluid (CSF).
It cushions the brain, reduces its weight, delivers nutrients, and removes waste.
What is CSF, and what are its key functions?
CSF is a clear fluid produced by the choroid plexus that:
Cushions the brain and spinal cord (shock absorption).
Reduces the brain’s effective weight (~1.4 kg to ~80 g).
Removes waste.
Delivers nutrients.
What structure produces CSF, and how often is it replenished?
The choroid plexus, located in each ventricle, produces CSF.
CSF is replenished every 3 hours.
Name the ventricles in the brain and their connections.
Lateral ventricles: Largest ventricles where most CSF is produced.
Third ventricle: Connects to the lateral ventricles via the foramen of Monro.
Cerebral aqueduct: Narrow passage linking the third and fourth ventricles.
Fourth ventricle: Adds more CSF and connects to the subarachnoid space.
Describe the pathway of CSF flow.
Lateral ventricles → Foramen of Monro → Third ventricle.
Third ventricle → Cerebral aqueduct → Fourth ventricle.
Fourth ventricle → Subarachnoid space, surrounding the brain and spinal cord.
Where is the subarachnoid space, and what is its function?
The subarachnoid space is the area surrounding the brain and spinal cord where CSF circulates.
It provides a protective cushion for the CNS.
What structures reabsorb CSF into the bloodstream?
Arachnoid granulations reabsorb CSF into the superior sagittal sinus, a large venous sinus in the dura mater.
What is obstructive hydrocephalus, and what causes it?
Obstructive hydrocephalus occurs when the flow of CSF is blocked, often at the cerebral aqueduct.
Causes include tumors or congenital defects, leading to increased intracranial pressure and brain damage if untreated.
What treatment is used for hydrocephalus?
A shunt is inserted into the ventricles to drain excess CSF into the abdomen or another body area.
A valve regulates the flow to relieve pressure.
What is the cerebral aqueduct, and why is it important?
The cerebral aqueduct is a narrow passage connecting the third and fourth ventricles.
Blockage here can lead to hydrocephalus.
What are arachnoid granulations, and what is their function?
Arachnoid granulations are small projections of the arachnoid mater that drain CSF into the superior sagittal sinus.
They remove old CSF to make room for new fluid.
What are dural venous sinuses, and what do they do?
Dural venous sinuses are blood vessels in the dura mater that carry away old CSF and venous blood from the brain.
The superior sagittal sinus is the largest sinus.
What are dural venous sinuses, and why are they important?
Definition: Large veins in the dura mater that drain cerebrospinal fluid (CSF) and venous blood from the brain.
Key Structures:
Superior Sagittal Sinus: Drains CSF into the bloodstream.
Transverse Sinus: Helps remove venous blood and connects with other sinuses.
Function: Maintains brain health by removing waste and regulating pressure.
What are the key roles of CSF in the brain?
Protects the brain by cushioning it.
Delivers nutrients to brain tissue.
Removes waste products.
Regulates pressure within the skull.
Why is the brain’s blood supply critical, and what happens during disruptions?
The brain relies on a constant supply of oxygen and glucose due to its inability to store energy.
Disruptions lead to:
1-second: Depletes oxygen.
6-seconds: Causes unconsciousness.
Minutes: Results in permanent brain damage.
What are the primary arteries supplying blood to the brain?
Internal carotid arteries: Supply the front and middle brain.
Vertebral arteries: Supply the back brain, including the brainstem and cerebellum.
What are dural venous sinuses, and what is their role?
Found in the dura mater, they:
Drain blood from superficial and deep veins.
Remove venous blood and cerebrospinal fluid (CSF) from the brain.
What is the function of deep and superficial veins in brain drainage?
Deep veins: Drain internal brain areas like the thalamus and hypothalamus.
Superficial veins: Is within the subarachnoid space. Drain blood from the brain’s surface into the dural venous sinuses.
What is a cerebrovascular accident (stroke), and what causes a haemorrhagic stroke?
A stroke occurs when blood flow to the brain is disrupted.
Haemorrhagic stroke:
Caused by bleeding in the brain due to vessel rupture.
Increases pressure on brain tissue, causing damage.
What causes an ischemic stroke, and what are its effects?
Ischemic stroke:
Caused by a blocked blood vessel.
Blockages include:
Thrombus: A stationary blood clot.
Embolus: A traveling blockage.
Leads to infarction (death of brain tissue).
What causes a haemorrhagic stroke, and what are its effects?
Caused by ruptured blood vessels, often due to:
High blood pressure.
Malformed vessels.
Effects: Leaking blood increases pressure on brain tissue, causing damage.
How does an ischemic stroke occur, and what are its effects?
Occurs due to blocked blood vessels, caused by:
Thrombus: Stationary blood clot.
Embolus: Traveling blockage.
Effects: Deprives brain tissue of oxygen, leading to infarction.
What is infarction, and how does it affect the brain?
Infarction is the death of brain tissue caused by oxygen deprivation due to restricted blood flow.
Why does the brain require a constant blood supply?
The brain uses ~20% of the body’s blood flow because it cannot store energy.
It needs continuous oxygen and glucose to function.
What is the blood-brain barrier, and what does it do?
The blood-brain barrier (BBB) is a protective barrier that prevents harmful substances in the blood from entering the brain while allowing essential nutrients to pass. It maintains the brain’s delicate balance of ions and chemicals.
Why does the brain need the blood-brain barrier (BBB)?
The BBB:
Protects the extracellular fluid around neurons.
Prevents toxins and harmful substances from disrupting neural communication.
Maintains the chemical balance necessary for proper brain function.
Why does the brain need the blood-brain barrier (BBB)?
The BBB:
Protects the extracellular fluid around neurons.
Prevents toxins and harmful substances from disrupting neural communication.
Maintains the chemical balance necessary for proper brain function.
How is the BBB selectively permeable?
Brain capillaries have tight junctions with no gaps between endothelial cells.
Substances must be actively transported by transporter proteins:
Glucose transporters bring fuel to the brain.
Waste transporters remove toxins from the brain.
What did Ehrlich’s experiments reveal about the BBB?
When dye was injected into the bloodstream, it stained all body tissues except the CNS.
When injected into the brain ventricles, the dye spread throughout the CNS.
These findings demonstrated the existence of the blood-brain barrier.
What is the area postrema, and why is it an exception to the BBB?
The area postrema has a weaker BBB, allowing it to detect toxins in the blood.
It triggers vomiting to expel harmful substances.
This prevents further harm by removing toxins before they reach the brain.
Why does the BBB protect neurons in the CNS?
Neurons rely on a stable ionic balance in the extracellular fluid.
Disruption of this balance by toxins or other substances would impair neural function.
