Chapter 14 - Brain

Question 1

Rostral

Answer 1

toward the nose/forehead

Question 2

Caudal

Answer 2

toward the “tail” / spinal cord

Question 3

Neural tube

Answer 3

becomes your brain & SC

Question 4

Notochord

Answer 4

• stays in your body central axis
• helps cue up development of left and right sides of body
• extends from head to tail of the embryo
• eventually becomes the nucleus pulposa in the pads of tissue between the vertebrae

Question 5

Major portions of brain

Answer 5

Cerebrum, Cerebellum, and Brainstem

Question 6

Corpus callosum

Answer 6

thick myelinated nerve bundle at bottom of longitudinal fissure that connects hemispheres

Question 7

Falx cerebri

Answer 7

separates R & L cerebral hemispheres

Question 8

Tentorium cerebelli

Answer 8

seperates cerebrum from cerebellum

Question 9

Falx cerebelli

Answer 9

separates R & L halves of cerebellum

Question 10

Gray Matter

Answer 10

• not shiny, dull, corresponds to unmyelinated parts of neurons, mainly cell bodies of neurons where synapses occur between axon terminals of one neuron with the dendrites and somas of other neurons

Question 11

White matter

Answer 11

-myelinated axons
- coordinates with myelinated axons, shiny, glossy
- tracts, bundles of axons traveling together

Question 12

Meninges

Answer 12

• protect the brain
  -sandwiched between the brain and skull
• provide structural framework for the CNS arteries and veins

Question 13

Flow of CSF

Answer 13

S: secretes choroid plexus into lateral ventricles
F: flows through inter ventricular foramina into third ventricle
A: Choroid plexus adds more CSF into third ventricle
D: Flows down cerebral aqueduct to fourth ventricle
A: Choroid plexus adds more CSF in fourth ventricle
T: Flows out two lateral apertures and one median aperture
B: fills subarachnoid space and bathes external surfaces of brain and spinal cord
R: reabsorbes into venous blood of dural venous sinuses

Question 14

CSF

Answer 14

Clear, colorless liquid that fills
– the ventricles & canals of CNS
– subarachnoid space (meninges, external surface of brain)
* Brain produces and absorbs 500 mL/day.
– 100 to 160 mL normally present at one time

Question 15

Functions of CSF

Answer 15

Buoyancy, Protection, Chemical stability

Question 16

Buoyancy

Answer 16

• Brains weigh approx 1.5 kg (3 lb).
• If it rested on floor of cranium, the pressure would kill the nervous tissue.

Question 17

Protection

Answer 17

• Protects the brain from striking the cranium when the head is jolted.
• Shaken child syndrome and concussions do occur from severe jolting.

Question 18

Chemical Stability

Answer 18

• Flow of CSF rinses away metabolic wastes.
• Homeostatically regulates: electrolytes, pH, osmolarity, etc.

Question 19

Blood supply

Answer 19

Brain is only 2% of adult body weight, but receives 15% of the blood.
– 750 mL/min.
* Neurons have a high demand for ATP, and therefore, oxygen and glucose, so a constant supply of blood is critical!!!
– A 10-sec interruption of blood flow may cause loss of consciousness.
– A 1 to 2 min interruption can cause significant impairment of neural function.
– Going 4 min without blood causes irreversible brain damage.

Question 20

What are the benefits and obstacles of having a BBB?

Answer 20

• Benefit - protects us from pathogens and hydrophilic toxins.
• Obstacle for delivering medications such as antibiotics and cancer drugs.
• Also, trauma and inflammation can damage BBB and allow pathogens to enter brain tissue

Question 21

Astrocyte foot processes

Answer 21

secrete paracrines that promote tight junction formation

Question 22

Tight Junction

Answer 22

prevents solute movement between endothelial cells

Question 23

BBB-

Answer 23

Blood Brain Barrier
- Key components: Astrocytes, Endothelial cells and Tight junctions

Question 24

BCB - Blood CSF Barrier

Answer 24

Protects brain at the choroid plexus.
○ Forms tight junctions between the ependymal cells.
○ Tight junctions are absent from ependymal cells elsewhere.
■ Important to allow exchange between brain tissue & CSF. What does get in the brain easily?….
● Highly permeable to: water, glucose, and lipid-soluble substances such as oxygen, carbon dioxide, alcohol, caffeine, nicotine, and anesthetics.
● Slightly permeable to: Na+, K+, Cl-, and the waste products urea and creatinine.

Question 25

CVOS - Circumventricular Organs

Answer 25

Are places in the third and fourth ventricles where the barrier is absent. * Blood has direct access to the brain. * Enables the brain to “sample blood” in order to monitor and respond to fluctuations in blood glucose, pH, osmolarity, and other variables. Ex. at the hypothalamus * CVOs afford a route for invasion by the human immunodeficiency virus (HIV).

Question 26

Functions of Medulla Oblongata

Answer 26

Sensory: Hearing Equilibrium Taste Touch Pressure Temperature Pain Motor: Chewing Salivation Swallowing Speech Head movement Neck movement Shoulder movement More Motor... Keeping you alive: Gagging Vomiting Respiration Coughing Sneezing Sweating Cardiovascular control Gastrointestinal control

Question 27

Hippocampus

Answer 27

Deep in temporal lobe * Consolidation (where short-term memory becomes long-term memory) * Damaged hippocampus → anterograde amnesia (no new long-term memories will be made)

Question 28

Optic sensory (II)

Answer 28

eye

Question 29

Olfactory (I)

Answer 29

nose

Question 30

Oculomotor (III)

Answer 30

all eye muscles

Question 31

Trochlear (IV)

Answer 31

superior oblique

Question 32

Abducent motor (VI)

Answer 32

external rectus muscle

Question 33

Trigeminal (V)

Answer 33

face, teeth, sinuses muscles of mastication

Question 34

Intermediate

Answer 34

Submaxillary and sublingual gland, anterir part of tongue and soft palate

Question 35

Glossopharyngeal (IX)

Answer 35

posterior part of tonge, tonsil, pharynx

Question 36

Vestibulocochlear (VIII)

Answer 36

inner ear

Question 37

Vagus (X)

Answer 37

heart, lungs, bronchi, trachea, larynx, pharynx, gastrointestinal tract, external ear

Question 38

Accessory (XI)

Answer 38

sternocleidomastoid and trapezius muscles

Question 39

Hypoglossal (XII)

Answer 39

muscles of the tongue

Question 40

Facial motor (VII)

Answer 40

muscles of the face

Question 41

Cranial dura mater

Answer 41

Has two layers – Outer periosteal = periosteum of cranial bones. – Inner meningeal continues into vertebral canal and forms dural sheath around spinal cord. – Layers separated by dural sinuses (#5 in fig) which collect blood & CSF circulating through brain. 2. Dura mater is pressed closely against cranial bones. * No epidural space (like spinal cord).

Question 42

Cranial Arachnoid mater

Answer 42

Similar to arachnoid mater in SC. 2. Transparent membrane with “fibers”. 3. Subarachnoid space separates it from pia mater below. 4. Subdural space separates it from dura mater above in some places. 5. Arachnoid villi/granulations discussed later with CSF flow (CSF enters dural sinuses/venous blood).

Question 43

Cranial Pia Mater

Answer 43

Similar to Pia mater in the SC. Very thin mb that follows contours of brain, dipping into sulci. Not usually visible without a microscope.