Psychobiology part 2 unit 9

Question 1

Human brain cannot support its own wight?

Answer 1

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 2

Question: What role does the cranium play in protecting the brain?

Answer 2

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 3

Question: Name the three fossae of the cranial floor and their functions.

Answer 3

Anterior fossa: Holds the frontal part of the brain.
Middle fossa: Supports the middle brain.
Posterior fossa: Cradles the cerebellum and brainstem.

Question 4

Question: What are the meninges, and what are their layers?

Answer 4

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.

Question 5

What is the role of cerebrospinal fluid (CSF) in brain protection?

Answer 5

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.

Question 6

How does an extradural/epidural haematoma occur?

Answer 6

It is caused by tearing of the middle meningeal artery, leading to bleeding in the extradural/epidural space between the dura mater and cranium.

Question 7

What happens as an extradural/epidural haematoma progresses?

Answer 7

Bleeding increases pressure in the epidural space, causing brain compression.
This is followed by a coma a few hours after the trauma.

Question 8

What are the outcomes if an extradural/epidural haematoma is untreated?

Answer 8

Rising intracranial pressure leads to brain displacement and ultimately death without immediate neurosurgery.

Question 9

What flows through the subarachnoid space, and what is its function?

Answer 9

The subarachnoid space contains cerebrospinal fluid (CSF), which cushions the brain and spinal cord, protecting against trauma.

Question 10

Describe the key features of the dura mater.

Answer 10

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.

Question 11

What causes meningitis, and what are its symptoms?

Answer 11

Meningitis is inflammation of the meninges caused by infections (viral, bacterial, fungal).
Symptoms include headache, vomiting, light sensitivity, fever, and neck stiffness.

Question 12

What is an extradural/epidural haematoma, and how does it occur?

Answer 12

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.

Question 13

What is the falx cerebri, and where is it located?

Answer 13

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.

Question 14

What is the tentorium cerebelli, and where is it located?

Answer 14

The tentorium cerebelli is a fold of the dura mater that separates the cerebellum from the posterior part of the cerebral hemispheres.

Question 15

What is the ventricular system, and what is its primary role?

Answer 15

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.

Question 16

What is CSF, and what are its key functions?

Answer 16

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.

Question 17

What structure produces CSF, and how often is it replenished?

Answer 17

The choroid plexus, located in each ventricle, produces CSF.
CSF is replenished every 3 hours.

Question 18

Name the ventricles in the brain and their connections.

Answer 18

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.

Question 19

Describe the pathway of CSF flow.

Answer 19

Lateral ventricles → Foramen of Monro → Third ventricle.
Third ventricle → Cerebral aqueduct → Fourth ventricle.
Fourth ventricle → Subarachnoid space, surrounding the brain and spinal cord.

Question 20

Where is the subarachnoid space, and what is its function?

Answer 20

The subarachnoid space is the area surrounding the brain and spinal cord where CSF circulates.
It provides a protective cushion for the CNS.

Question 21

What structures reabsorb CSF into the bloodstream?

Answer 21

Arachnoid granulations reabsorb CSF into the superior sagittal sinus, a large venous sinus in the dura mater.

Question 22

What is obstructive hydrocephalus, and what causes it?

Answer 22

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.

Question 23

What treatment is used for hydrocephalus?

Answer 23

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.

Question 24

What is the cerebral aqueduct, and why is it important?

Answer 24

The cerebral aqueduct is a narrow passage connecting the third and fourth ventricles.
Blockage here can lead to hydrocephalus.

Question 25

What are arachnoid granulations, and what is their function?

Answer 25

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.

Question 26

What are dural venous sinuses, and what do they do?

Answer 26

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.

Question 27

What are the key roles of CSF in the brain?

Answer 27

Protects the brain by cushioning it.
Delivers nutrients to brain tissue.
Removes waste products.
Regulates pressure within the skull.

Question 28

Why is the brain’s blood supply critical, and what happens during disruptions?

Answer 28

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.

Question 29

What are the primary arteries supplying blood to the brain?

Answer 29

Internal carotid arteries: Supply the front and middle brain.
Vertebral arteries: Supply the back brain, including the brainstem and cerebellum.

Question 30

What are dural venous sinuses, and what is their role?

Answer 30

Found in the dura mater, they:
Drain blood from superficial and deep veins.
Remove venous blood and cerebrospinal fluid (CSF) from the brain.

Question 31

What is the function of deep and superficial veins in brain drainage?

Answer 31

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.

Question 32

What is a cerebrovascular accident (stroke), and what causes a haemorrhagic stroke?

Answer 32

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.

Question 33

What causes an ischemic stroke, and what are its effects?

Answer 33

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).

Question 34

What causes a haemorrhagic stroke, and what are its effects?

Answer 34

Caused by ruptured blood vessels, often due to:
High blood pressure.
Malformed vessels.
Effects: Leaking blood increases pressure on brain tissue, causing damage.

Question 35

How does an ischemic stroke occur, and what are its effects?

Answer 35

Occurs due to blocked blood vessels, caused by:
Thrombus: Stationary blood clot.
Embolus: Traveling blockage.
Effects: Deprives brain tissue of oxygen, leading to infarction.

Question 36

What is infarction, and how does it affect the brain?

Answer 36

Infarction is the death of brain tissue caused by oxygen deprivation due to restricted blood flow.

Question 37

Why does the brain require a constant blood supply?

Answer 37

The brain uses ~20% of the body’s blood flow because it cannot store energy.
It needs continuous oxygen and glucose to function.

Question 38

What is the blood-brain barrier, and what does it do?

Answer 38

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.

Question 39

Why does the brain need the blood-brain barrier (BBB)?

Answer 39

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.

Question 40

Why does the brain need the blood-brain barrier (BBB)?

Answer 40

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.

Question 41

How is the BBB selectively permeable?

Answer 41

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.

Question 42

What did Ehrlich’s experiments reveal about the BBB?

Answer 42

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.

Question 43

What is the area postrema, and why is it an exception to the BBB?

Answer 43

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.

Question 44

Why does the BBB protect neurons in the CNS?

Answer 44

Neurons rely on a stable ionic balance in the extracellular fluid.
Disruption of this balance by toxins or other substances would impair neural function.