m1

Question 1

brain’s three major portions

Answer 1

the cerebrum, cerebellum, and brainstem.

Question 2

volume

Answer 2

cerebrum 83%
cerebellum 10% but consist 50% of neurons

Question 3

All nerve fibers connecting the brain to the spinal cord pass through the

Answer 3

medulla

Question 4

contains neural networks involved in a multitude of fundamental sensory and motor functions.

Answer 4

medulla

Question 5

it includes a cardiac center, which regulates the rate and force of the heartbeat; a vasomotor center, which regulates blood pressure and flow by dilating and constricting blood vessels; two respiratory centers, which regulate the rhythm and depth of breathing; and other nuclei involved in the aforementioned motor functions.

Answer 5

medulla

Question 6

appears as a broad anterior bulge rostral to the medulla. Posteriorly, it consists mainly of two pairs of thick stalks called cerebellar peduncles. They connect the cerebellum to the pons and midbrain.

Answer 6

pons

Question 7

the pons exhibits continuations of the previously mentioned reticular formation, medial lemniscus, and tectospinal tract. We also see extensions of the spinal cord’s anterolateral system and anterior spinocerebellar tract.

Answer 7

cross section pons

Question 8

pons is dominated by tracts of white matter, including transverse fascicles that cross between left and right and connect the two hemispheres of the cerebellum, and longitudinal fascicles that carry sensory and motor signals up and down the brainstem.

Answer 8

anterior half pons

Question 9

posterior to the cerebral aqueduct is a rooflike tectum. It exhibits four bulges, the corpora quadrigemina. The upper pair, called the superior colliculi, functions in visual attention, visually tracking moving objects, and such reflexes as blinking, focusing, pupillary dilation and constriction, and turning the eyes and head in response to a visual stimulus (for example, to look at something that you catch sight of in your peripheral vision). The lower pair, called the inferior colliculi, receives signals from the inner ear and relays them to other parts of the brain, especially the thalamus. Among other functions, they mediate the reflexive turning of the head in response to a sound, and one’s tendency to jump when startled by a sudden noise.

Answer 9

midbrain

Question 10

consists mainly of the cerebral peduncles—two stalks that anchor the cerebrum to the brainstem. Each peduncle has three main components: tegmentum, substantia nigra, and cerebral crus. The tegmentum is dominated by the red nucleus, named for a pink color imparted by its high density of blood vessels. Fibers from the red nucleus form the rubrospinal tract in most mammals, but in humans its connections go mainly to and from the cerebellum, with which it collaborates in fine motor control. The substantia nigra is a dark gray to black nucleus pigmented with melanin. It is a motor center that relays inhibitory signals to the thalamus and basal nuclei, preventing unwanted body movement. The cerebral crus is a bundle of nerve fibers that connect the cerebrum to the pons and carry the corticospinal nerve tracts. Surrounding the cerebral aqueduct is an arrowheadshaped body called the central (periaqueductal) gray matter. It is involved with the reticulospinal tracts in controlling awareness of pain.

Answer 10

midbrain

Question 11

highly active when a person explores objects with the fingertips, for example to compare the textures of two objects without looking at them. (Tactile nerve fibers from a rat’s snout and a cat’s forepaws also project strongly to the cerebellum.) Some spatial perception also resides here. The cerebellum is much more active when a person is required to solve a pegboard puzzle than when moving pegs randomly around the same puzzle board. People with cerebellar lesions also have difficulty identifying different views of a threedimensional object as belonging to the same object.

Answer 11

cerebellum

Question 12

consists of the diencephalon and telencephalon. The diencephalon encloses the third ventricle and is the most rostral part of the brainstem. The telencephalon develops chiefly into the cerebrum

Answer 12

forebrain

Question 13

It is the seat of your sensory perception, memory, thought, judgment, and voluntary motor actions. It is the most complex and challenging frontier of neurobiology.

Answer 13

cerebrum

Question 14

is chiefly concerned with voluntary motor functions, motivation, foresight, planning, memory, mood, emotion, social judgment, and aggression.

Answer 14

frontal lobe cerebellum

Question 15

is the primary site for receiving and interpreting signals of the general senses described later in this chapter; for taste (one of the special senses); and for some visual processing.

Answer 15

parietal lobe cerebrum

Question 16

is the principal visual center of the brain.

Answer 16

occipital lobe cerebrum

Question 17

concerned with hearing, smell, learning, memory, and some aspects of vision and emotion.

Answer 17

temporal lobe cerebrum

Question 18

less understood than the other lobes because it is less accessible to testing in living subjects, but it apparently plays roles in understanding spoken language, in the sense of taste, and in integrating sensory information from visceral receptors.

Answer 18

insula cerebrum

Question 19

are masses of cerebral gray matter buried deep in the white matter,
lateral to the thalamus. They are often called basal ganglia, but the word ganglion is best
restricted to clusters of neurons outside the CNS. Neuroanatomists disagree on how many brain
centers to classify as basal nuclei, but agree on at least three: the caudate nucleus, putamen ,
and globus pallidus. The putamen and globus pallidus are also collectively called the lentiform
nucleus, because together they form a lensshaped body. The putamen and caudate nucleus are
also collectively called the corpus striatum after their striped appearance. The basal nuclei
receive input from the substantia nigra of the midbrain and motor areas of the cerebral cortex,
and send signals back to both of these locations. They are involved in motor control and are
further discussed in a later section on that topic.

Answer 19

basal nuclei

Question 20

receives fibers from the anterior rami of nerves C1 to C5 and gives rise to the nerves listed below, in order from superior to inferior

Answer 20

cervical plexus

Question 21

, which travel down each side of the mediastinum, innervate the diaphragm, and play an essential role in breathing. In addition to the major nerves listed here, there are several motor branches that innervate the geniohyoid, thyrohyoid, scalene, levator scapulae, trapezius, and sternocleidomastoid muscles.

Answer 21

phrenic nerves

Question 22

is formed predominantly by the anterior rami of nerves C5 to T1 (C4 and T2 make smaller contributions). It passes over the first rib into the axilla and innervates the upper limb and some muscles of the neck and shoulder. The subdivisions of this plexus are called roots, trunks, divisions, and cords. The five roots are the anterior rami of C5 through T1. Roots C5 and C6 converge to form the upper trunk; C7 continues as the middle trunk; and C8 and T1 converge to form the lower trunk. Each trunk divides into an anterior and posterior division; as the body is dissected from the anterior surface of the shoulder inward, the posterior divisions are found behind the anterior ones. Finally, the six divisions merge to form three large fiber bundles—the lateral, posterior, and medial cords. From these cords arise the following major nerves, listed in order of the illustration from superior to inferior.

Answer 22

branchial plexus

Question 23

formed from the anterior rami of nerves L1 to L4 and some fibers from T12. With only five roots and two divisions, it is less complex than the brachial plexus. It gives rise to the following nerves.

Answer 23

lumbar plexus

Question 24

formed from the anterior rami of nerves L1 to L4 and some fibers from T12. With only five roots and two divisions, it is less complex than the brachial plexus. It gives rise to the following nerves.

Answer 24

sacral plexus

Question 25

is a tiny plexus formed from the anterior rami of S4, S5, and Co. The tibial and common fibular nerves travel together through a connective tissue sheath; they are referred to collectively as the sciatic nerve. The sciatic nerve passes through the greater sciatic notch of the pelvis, extends for the length of the thigh, and ends at the popliteal fossa. Here, the tibial and common fibular nerves diverge and follow their separate paths into the leg. The tibial nerve descends through the leg and then gives rise to the medial and plantar nerves in the foot. The common fibular nerve divides into deep and superficial fibular nerves. The sciatic nerve is a common focus of injury and pain.

Answer 25

coccygeal plexus