The Brain & Cranial Nerves

Front 1

1. List 3 major portions of the brain?

Back 1

the cerebrum, cerebellum, and brainstem.

Front 2

List subdivisons of the brain stem?

Back 2

The brainstem is that which remains of the brain if the cerebrum and cerebellum are removed.
i. Its major components, rostral to caudal, are the diencephalon, midbrain, pons, and medulla oblongata. (Figs. 14.1b, 14.2)
ii. It is oriented like a vertical stalk with the cerebrum perched on top in a living person; postmortem changes give it an oblique angle.
iii. The brainstem ends at the foramen magnum, and the CNS continues below this as the spinal cord.

Front 3

2. T or F. In the spinal cord, the gray matter is deep to the white matter & in the brain, white matter is deep to the gray matter.

Back 3

The brain, like the spinal cord, is composed of gray matter and white matter. (p. 518) (Figs. 14.5, 14.6c)
1. White matter has a bright pearly white color due to myelin around its nerve fibers.
2. Gray matter has little myelin and a duller white color.
a. Gray matter forms a surface layer called the cortex over the cerebrum and cerebellum.
b. Deeper masses called nuclei are surrounded by white matter.
c. In most of the brain, the white matter lies deep to the cortical gray matter, opposite from their relation in the spinal cord.

Front 4

3. List the meninges from superficial to deep. Describe distinquishing characteristics of ea layer

Back 4

A. The brain is enveloped in three connective tissue membranes, the meninges, which lie between the nervous tissue and bone. (pp. 520–521)
1. The three membranes of the meninges are the dura mater, arachnoid mater, and pia mater.

Front 5

dura mater

Back 5

2. In the cranial cavity, the dura mater consists of two layers, the outer periosteal layer and the inner meningeal layer.
a. Only the meningeal layer continues into the vertebral canal, where it forms the dural sac.
b. The dura mater is pressed closely against the cranial bone, but is not attached except in limited places (foramen magnum, sella turcica, crista galli, and sutures).

Front 6

arachnoid mater

Back 6

Neural crest cells give rise to the arachnoid mater and pia mater; most of the PNS including sensory and autonomic nerves, ganglia, and Schwann cells; and some other structures of the skeletal, integumentary, and endocrine systems.

Front 7

pia mater

Back 7

The pia mater is a very thin, delicate membrane that follows all contours of the brain and sulci.

Front 8

4. Name the 4 ventricles of the brain. What is their purpose?

Back 8

The brain has four internal chambers called ventricles that are filled with cerebrospinal fluid.

Front 9

lateral ventricles

Back 9

The largest and most rostral are the lateral ventricles, which form an arc in each cerebral hemisphere.

Front 10

3rd ventricle

Back 10

The lateral ventricles connect to the third ventricle, a median space inferior to the corpus callosum, via the interventricular foramina.

Front 11

4th ventricle

Back 11

A canal called the cerebral aqueduct leads from the third ventricle to the fourth ventricle, a triangular chamber between the pons and cerebellum.
4. The fourth ventricle narrows caudally to form the central canal that extends through the medulla oblongata into the spinal cord.
5. Each ventricle has a mass of blood capillaries on the floor or wall called a choroids plexus.
a. Ependyma is a type of neuroglia that resembles cuboidal epithelium.
b. It lines the ventricles and canals, covers the choroids plexuses, and produces cerebrospinal fluid.

Front 12

5. What are the 3 purposes of cerebral spinal fluid?

Back 12

a. Buoyancy. The brain and CSF are similar in density; this buoyancy allows the brain to attain considerable size without being impaired by its own weight.
b. Protection. CSF helps prevent the brain from striking the cranium when the head is jolted; however, severe jolts may still be damaging, as in shaken baby syndrome and concussions from car accidents, boxing, etc.
c. Chemical stability. The flow of CSF rinses metabolic wastes away and homeostatically regulates the brain’s chemical environment.

Front 13

6. By what structure does cerebrospinal fluid return to the blood stream?

Back 13

Cerebrospinal fluid (CSF) is a clear, colorless liquid that fills the ventricles and canals of the CNS and bathes its external surface. A small amount of CSF fills the central canal of the spinal cord, but all of it escapes through three pores in the walls of the fourth ventricle: a median aperture and two lateral apertures.
i. These apertures lead into the subarachnoid space.
ii. CSF is reabsorbed in this space by the arachnoid villi.

Front 14

8. Name the glial cell involved in formation of the cerebrospinal fluid?

Back 14

i. Ependymal cells modify this filtrate so that CSF has more sodium and chloride, but less potassium, calcium, and glucose and very little protein.

Front 15

8. Name the glial cell involved in formation of the blood brain barrier?

Back 15

i. During development, astrocytes induce development of the tight junctions in these endothelial cells.
ii. Anything leaving the blood must therefore pass through the cells and not between them.
b. The choriod plexuses are another point of entry, and this is protected by the blood–CSF barrier formed by tight junctions between ependymal cells.

Front 16

9. Which area of the brain stem regulates heart beat, blood pressure and respiration?

Back 16

Medulla-b. Motor functions include chewing, salivation, swallowing, gagging, vomiting, respiration, speech, coughing, sneezing, sweating, cardiovascular and gastrointestinal control, and head, neck, and shoulder movements.

Front 17

10. Which major portion of the brain has the primary function of motor coordination?

Back 17

cerebellum

Front 18

11. The thalamus, hypothalamus & epithalamus are components of which part of the brain stem?

Back 18

Forebrain: The diencephalon, which encloses the third ventricle, has three major derivatives; the thalamus, hypothalamus, and epithalamus.

Front 19

12. List 3 functions controlled by the hypothalamus?

Back 19

The hypothalamus is the major control center of the autonomic nervous system and endocrine system and is concerned with a variety of visceral functions. (Fig. 14.12b)
i. Hormone secretion. Hormones secreted by the hypothalamus control the anterior pituitary gland to regulate growth, metabolism, reproduction, and stress response; the hypothalamus also produces hormones that are stored in the posterior pituitary that have to do with labor contraction, lactation, and water balance.
ii. Autonomic effects. The hypothalamus is an integrating center for the autonomic nervous system and influences heart rate, blood pressure, and other visceral functions.
iii. Thermoregulation. The hypothalamic thermostat, a collection of neurons mainly in the preoptic nucleus, monitor body temperature and adjust it.
iv. Food and water intake. The hunger and satiety centers of the hypothalamus monitor blood glucose levels, and osmoreceptors monitor the salt concentration of the blood; these stimulate behavioral and hormonal changes.

Front 20

13. Which part of brain stem allows us to screen out insignificant stimuli, but permits important sensory signals to pass?

Back 20

The reticular formation : e. Habituation. This process allows the brain to ignore repetitive, inconsequential stimuli via the reticular activating system or extrathalamiccortical modulatory system.

Front 21

14. Which part of the brain is known as the "gateway to the cerebral cortex?"

Back 21

The thalamus is the “gateway to the cerebral cortex” in that nearly all input passes through synapses in the thalamic nuclei.
e. The thalamus plays a key role in motor control by relaying signals from the cerebellum to the cerebrum.
f. It provides feedback loops between the cerebral cortex and the deep cerebral motor centers (the basal nuclei).
g. The thalamus is involved in the memory and emotional functions of the limbic system.

Front 22

15. What is the white matter in the cerebellum called? Why is it called this?

Back 22

a. The white matter exhibits a fernlike pattern called the arbor vitae.

Front 23

16. Define:

Back 23

below

Front 24

gyri

Back 24

. The conspicuous gyri of each hemisphere are separated by grooves called sulci; the folding into gyri allows a greater amount of cortex to fit into the cranial cavity.

Front 25

sulci

Back 25

conspicuous gyri of each hemisphere are separated by grooves called sulci;

Front 26

longitudinal fissure

Back 26

a. The cerebrum is about 83% of the brain volume and consists of two cerebral hemispheres. (Fig. 14.1a)
i. Each hemisphere has thick folds called gyri separated by shallow grooves called sulci.
ii. The deep longitudinal fissure separates the right and left hemispheres.

Front 27

corpus callosum

Back 27

In cerebrum. Most pass through the corpus callosum, which forms the floor of the longitudinal fissure.

Front 28

17. Name the lobes of the cerebral cortex?

Back 28

parietal lobe, frontal lobe, temporal lobe, occipital lobe