Part 1

Question 1

Where are the major parts of the adult brain directly derived from?

Answer 1

The embryonic brain vesicles

Question 2

What are the 5 secondary brain vesicles?

Answer 2

Forebrain:
1. telencephalon
2. diencephalon

Midbrain:
3. mesencephalon

Hindbrain:
4. metencephalon
5. myelencephalon

Question 3

What adult structures are the 5 secondary brain vesicles derived from?

Answer 3

1. telencephalon - cerebrum
2. diencephalon - thalamus, hypothalamus, epithalamus
3. mesencephalon - midbrain
4. metencephalon - pons, cerebellum
5. myelencephalon - medulla oblongata

Question 4

What are the parts of the brain that is already existed at birth?

Answer 4

1) cerebral hemisphere
2) diencephalon
3) cerebellum
4) brain stem:
- midbrain
- pons
- medulla
- oblongata
- spinal cord

At birth, the neonatal brain looks very much like that of an adult and almost all the neurons the brain will ever have are already present

Question 5

How many neurons, connections, and neuroglia cells do you have?

Answer 5

100 billion neurons, 100 trillion connections, supported by 10 trillion neuroglia cells

Question 6

What are the 4 general structure the brain is divided into?

Answer 6

1) cerebrum
- responsible for higher functions; contains a convoluted surface called the Cortex , is divided into left & right hemispheres

2) diencephalon
- consists of the thalamus, hypothalamus, limbic system and pituitary gland

3) cerebellum
- coordinate body movement & helps maintain balance and postural control
- involved in planning and coordinating movement on the fly
- also divided into hemispheres (10% brain volme but 50% of brains’ neurons)

4) brain stem
- consists of the midbrain, the pons, and the medulla oblongata, which are involved in autonomic functions

Question 7

What is the function of the cerebrum?

Answer 7

• Conscious though processes, intellectual functions
• memory storage and processing
• conscious and subconscious regulation of skeletal muscle contraction

Question 8

What is the function of the thalamus?

Answer 8

• Relay and processing centers for sensory and motor information

Question 9

What is the function of the hypothalamus?

Answer 9

Centers controlling emotions, autonomic functions, and hormone production

Question 10

What is the function of the midbrain?

Answer 10

• processing of visual and auditory data
• generation of reflexive somatic motor responses
• maintenance of consciousness

Question 11

What is the function of the pons?

Answer 11

• Relays sensory information to cerebellum and thalamus
• subconscious somatic and visceral motor centers

Question 12

What is the function of medulla oblongata?

Answer 12

• relays sensory information to thalamus and to other portions of the brain stem
• autonomic centers for regulation of visceral function (cardiovascular, respiratory, and digestive system activities)

Question 13

What is the function of the cerebellum?

Answer 13

• coordinates complex somatic motor patterns
• adjusts output of other somatic motor centers in brain and spinal cord

Question 14

What is the cerebrum?

Answer 14

The convoluted surface of the cerebrum consists of gyri and sulci, and deeper sulci called fissures. These structures increase the area of the brain and form anatomical landmarks
= increase the area of the brain and form anatomical landmarks

It is divided into lobes, which are named according to the bone which protects them
2 has layers
the outer = gray matter (neural cell bodies)
the inner = white matter (myelinated axons)
(Basal nuclei are clusters of gray matter that lie in deeper regions of the brain)

Question 15

What are basal nuclei?

Answer 15

are clusters of gray matter that lie in deeper regions of the brain

Question 16

Where is the longitudinal fissure located?

Answer 16

Between frontal lobes (left & right hemispheres)
- precentral gyrus (primary motor cortex) is located laterally from the central sulcus, in left hemisphere

Question 17

Where is the central sulcus?

Answer 17

Between the frontal lobes and parietal lobes
- divides the brain horizontally through the center
- postcentral gyrus (somatosensory cortex) is located in left hemisphere after central sulcus

Question 18

What are the ventricles in the brain?

Answer 18

During embryonic development, large hollow chambers form in the cerebrum
- lateral ventricles (one in each hemisphere)

These ventricles are connected via the interventricular to the third in the diencephalon

The fourth ventricle is located in posterior to the brainstem and is connected to the third ventricle by the cerebral aqueduct
- the fourth ventricle is continuous with the central canal of the spinal cord and contains apertures that connect with the subarachnoid space

The ventricles are filled with CSF and are lined with ependymal cells that circulate and absorb CSF via cillia and microvili

Question 19

Explain the location of the third & fourth ventricles

Answer 19

Lateral ventricles are connected via the interventricular foramen to the third ventricle in the diencephalon

Fourth ventricle is located posterior to the brainstem and is connected to the third ventricle by the cerebral aqueduct

(the fourth ventricle is continuous w/ the central canal of the spinal cord & contains Apertures that connect w/ the subarachnoid space) 12p

Question 20

What are ventricles lined with?

Answer 20

Ependymal cells

Question 21

What are ventricles filled with?

Answer 21

Cerebrospinal fluid

Question 22

What are the 3 ways the brain is physically/mechanically protected?

Answer 22

1. the bony cranium
2. cranial meninges
3. cerebrospinal fluid

Question 23

What are meninges?

Answer 23

Connective tissue covering of the brain and spinal cord
1. pia mater
2. arachnoid mater
3. dura mater

the cranial meninges are continuous with spinal meninges

Question 24

What are the layers of the cranial dura mater?

Answer 24

2 Layers;

1. an external periosteal layer
2. an internal meningeal layer
   
   • the spinal dura mater has only one

Dural sinus: between the layers: tissue fluids, blood vessels, including several large venous sinuses called dural sinuses

the veins of the brain open into these sinuses, which deliver venous blood to internal jugular veins of the neck
- drain old fluid and blood in sinus

Question 25

What is the biochemical protection of the brain?

Answer 25

1. blood brain farrier = several mechanisms that isolate CNS from general circulation (e.g. astrocytes) 2. cerebrospinal fluid

Question 26

What are the components of each layer of the cranial meninges?

Answer 26

1. Dura mater: a. dura mater (endosteal layer; outermost) b. dural sinus c. dura mater (meningeal layer) 2. Arachnoid mater: a. arachnoid membrane b. subarachnoid space c. arachnoid trabeculae 3. Pia mater: covers entire surface following folds - is bound to surface of brain by astrocytes Anchored by: processes (branches) from astrocytes

Question 27

What is found between inner and outer dura mater layers?

Answer 27

Tissue fluids and blood vessels including several large venous sinuses the veins of the brain open into these sinuses, which deliver venous blood to internal jugular veins of the neck

Question 28

What are dural folds?

Answer 28

Sheets of dura mater that dip into deep folds of brain and return to surface - located within dural folds: dural sinuses (lined with epithelium, collecting veins) 3 major dural folds: 1. falx cerebri 2. tentorium cerebelli 3. falx cerebelli

Question 29

What is the falx cerebri?

Answer 29

one of the three major dural folds - in the longitudinal fissure between two hemispheres of cerebrum

Question 30

What is the tentorium cerebelli?

Answer 30

one of the three major dural folds - between cerebrum and cerebellum

Question 31

What is the falx cerebelli?

Answer 31

one of the major dural folds - between two hemispheres of cerebellum

Question 32

What do dural sinuses contain?

Answer 32

- Venous blood (deoxygenated) - old CSF

Question 33

What is the protective function meninges?

Answer 33

Dural folds: "seat belts" - hold the brain in position Cerebrospinal Fluid: cushions, supports (floats in brain)

Question 34

Where is the cerebrospinal fluid located?

Answer 34

1. 4 ventricles 2. Subarachnoid space of cranium and spinal cord 3. Central canal of the spinal cord re-enters the blood stream through the arachnoid villi

Question 35

What are the functions of cerebrospinal fluid?

Answer 35

1. Cushioning 2. Supporting (floating brain weighs only 50g when supported by CSF) 3. Transporting nutrients, chemical messengers, waste

Question 36

How is cerebrospinal fluid produced?

Answer 36

Produced by choroid plexus = capillaries surrounded by specialized ependymal cells capillary fluid is allowed to filter out of the bloodstream, but only certain molecules are permitted past the ependymal cells Formed from blood plasma, giving it similar composition location: in each of the ventricles

Question 37

What is the composition of cerebrospinal fluid

Answer 37

Glucose, O2, CO2, vitamins, other ions - low in protein and K+

Question 38

What is the blood brain barrier?

Answer 38

The capillaries supplying the brain are very selective in what they allow to enter the brain and CSF - proteins, amino acids, waste products, most drugs, and K+ are not permitted access - the barrier is ineffective against fat-soluble molecules (alcohol, nicotine, anesthetics) - function is to isolate tissue of CNS from general circulation - tight control over CSF composition

Question 39

What is the volume/how does CSF circulate?

Answer 39

Total volume at any time : 150mL Total volume produced per day : 500 mL Pressure remains constant, because the rate of fluid reabsorption equals the rate of fluid production = 20mL/hr Circulation: - enters subarachnoid space through 2 lateral apertures and a median aperture - flows around brain, spinal cord, and cauda equina and into central canal and ventricles

Question 40

What is meningitis?

Answer 40

Inflammation of the meninges and is life threatening - bacterial/viral meningitis can spread to the brain or spinal cord; if the brain becomes inflamed, it is called encephalitis - meningitis can be diagnosed by examining a sample of cerebral spinal fluid taken from the subarachnoid space in the spinal column

Question 41

How is CSF drained?

Answer 41

Through arachnoid granulations... granulations = extensions of arachnoid mater that project into the superior sagittal sinus (a dural sinus) CSF moves into the superior sagittal sinus, that collects CSF and returns it to the jugular veins for drainage to the heart

Question 42

What is hydrocephalus?

Answer 42

Hydrocephalus is a condition where CSF accumulates. In adults this leads to an increase in intracranial pressure and compression of the brain - can occur as a result of congenital abnormalities, head injury, meningitis - in neonates, the bones of the skull have not yet fused as immoveable sutures, and have spaces between bones = fontanelles - hydrocephalus in the neonate is a serious condition if left untreated; however the skull can expand to compensate for the additional volume and temporarily prevent a rise in ICP. Early signs include bulging at the fontanelles; recording head size in the neonate is common practice 1. Internal hydrocephalus: blockage within ventricles 2. External hydrocephalus: blockage at subarachnoid granulations

Question 43

What is the unusual architecture of the Blood brain barrier?

Answer 43

The vascular endothelium around brain capillaries differs from most other organs of the body in that it forms tight junctions with the end-feet of neraby astrocytes As a result of this unusual architecture, a blood brain barrier (BBB) is formed: - astrocytes - pericytes (contractile) - tight junctions (between endothelial cells)

Question 44

Describe the movement of substances between the brain capillaries and interstitial fluid

Answer 44

a) lipid soluble substances, O2, and CO2 - can diffuse across membrane b) water, alcohol, and ions; Ca++, Na+, K+, Mg++, Cl-, H- - move through protein channels c) larger substances: glucose - moved by protein channels Most drugs are water soluble and cannot cross BBB b and c require transmembrane channels and sometimes ATP (slower rate of transport) covering surface of capillaries in CNS: astrocytes that control permeability of the endothelium (compared to blood, CSF is 7.33 has low protein, few WBCs no RBCs & different ion concentrations (through the same overall osmolarity)