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BIOL 131 - Brain and Cranial Nerves > Part 1 > Flashcards

Part 1 Flashcards

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1
Q

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

A

The embryonic brain vesicles

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2
Q

What are the 5 secondary brain vesicles?

A

Forebrain:
1. telencephalon
2. diencephalon

Midbrain:
3. mesencephalon

Hindbrain:
4. metencephalon
5. myelencephalon

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3
Q

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

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

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

A

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

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5
Q

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

A

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

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6
Q

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

A

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

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7
Q

What is the function of the cerebrum?

A
  • Conscious though processes, intellectual functions
  • memory storage and processing
  • conscious and subconscious regulation of skeletal muscle contraction
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8
Q

What is the function of the thalamus?

A
  • Relay and processing centers for sensory and motor information
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9
Q

What is the function of the hypothalamus?

A

Centers controlling emotions, autonomic functions, and hormone production

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10
Q

What is the function of the midbrain?

A
  • processing of visual and auditory data
  • generation of reflexive somatic motor responses
  • maintenance of consciousness
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11
Q

What is the function of the pons?

A
  • Relays sensory information to cerebellum and thalamus
  • subconscious somatic and visceral motor centers
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12
Q

What is the function of medulla oblongata?

A
  • 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)
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13
Q

What is the function of the cerebellum?

A
  • coordinates complex somatic motor patterns
  • adjusts output of other somatic motor centers in brain and spinal cord
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14
Q

What is the cerebrum?

A

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)

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15
Q

What are basal nuclei?

A

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

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16
Q

Where is the longitudinal fissure located?

A

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

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17
Q

Where is the central sulcus?

A

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

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18
Q

What are the ventricles in the brain?

A

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

19
Q

Explain the location of the third & fourth ventricles

A

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

20
Q

What are ventricles lined with?

A

Ependymal cells

21
Q

What are ventricles filled with?

A

Cerebrospinal fluid

22
Q

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

A
  1. the bony cranium
  2. cranial meninges
  3. cerebrospinal fluid
23
Q

What are meninges?

A

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

24
Q

What are the layers of the cranial dura mater?

A

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

25
Q

What is the biochemical protection of the brain?

A
  1. blood brain farrier
    = several mechanisms that isolate CNS from general circulation (e.g. astrocytes)
  2. cerebrospinal fluid
26
Q

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

A
  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

27
Q

What is found between inner and outer dura mater layers?

A

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

28
Q

What are dural folds?

A

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

29
Q

What is the falx cerebri?

A

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

30
Q

What is the tentorium cerebelli?

A

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

31
Q

What is the falx cerebelli?

A

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

32
Q

What do dural sinuses contain?

A
  • Venous blood (deoxygenated)
  • old CSF
33
Q

What is the protective function meninges?

A

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

34
Q

Where is the cerebrospinal fluid located?

A
  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

35
Q

What are the functions of cerebrospinal fluid?

A
  1. Cushioning
  2. Supporting (floating brain weighs only 50g when supported by CSF)
  3. Transporting nutrients, chemical messengers, waste
36
Q

How is cerebrospinal fluid produced?

A

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

37
Q

What is the composition of cerebrospinal fluid

A

Glucose, O2, CO2, vitamins, other ions

  • low in protein and K+
38
Q

What is the blood brain barrier?

A

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
39
Q

What is the volume/how does CSF circulate?

A

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

40
Q

What is meningitis?

A

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
41
Q

How is CSF drained?

A

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

42
Q

What is hydrocephalus?

A

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
43
Q

What is the unusual architecture of the Blood brain barrier?

A

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)

44
Q

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

A

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)

BIOL 131 - Brain and Cranial Nerves (2 decks)

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