Page 323 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

12 Central Nervous System and Senses

basal ganglia, i.e. caudate nucleus (! C5), puta-
Central Nervous System
men (! C7), globus pallidus (! C8), and parts
The brain and spinal cord make up the central of the amygdala (! C10). The amygdaloid nu-
nervous system (CNS) (! A). The spinal cord is cleus and cingulate gyrus (! D2) belong to the
divided into similar segments, but is 30% limbic system (! p. 330). The cerebral cortex
shorter than the spinal column. The spinal consists of four lobes divided by fissures (sulci),
nerves exit the spinal canal at the level of their e.g., the central sulcus (! D1, E) and lateral sul-
respective vertebrae and contains the afferent cus (! C3, E). According to Brodmann’s map,
somatic and visceral fibers of the dorsal root, the cerebral cortex is divided into histologi-
which project to the spinal cord, and the effer- cally distinct regions (! E, italic letters) that
ent somatic (and partly autonomic) fibers of generally have different functions (! E). The
the anterior root, which project to the periph- hemispheres of the brain are closely connected
ery. Thus, a nerve is a bundle of nerve fibers by nerve fibers of the corpus callosum (! C1,
that has different functions and conducts im- D3).
pulses in different directions (! p. 42).
Spinal cord (! A). Viewed in cross-section, Cerebrospinal Fluid
the spinal cord has a dark, butterfly-shaped
inner area (gray matter) surrounded by a The brain is surrounded by external and inter-
lighter outer area (white matter). The four nal cerebrospinal fluid (CSF) spaces (! B). The
wings of the gray matter are called horns internal CSF spaces are called ventricles. The
(cross-section) or columns (longitudinal sec- two lateral ventricles, I and II, (! B, C2) are
tion). The anterior horn contains motoneurons connected to the IIIrd and IVth ventricle and to
(projecting to the muscles), the posterior horn the central canal of the spinal cord (! B). Ap-
contains interneurons. The cell bodies of most proximately 650 mL of CSF forms in the choroid
afferent fibers lie within the spinal ganglion plexus (! B, C4) and drains through the
outside the spinal cord. The white matter con- arachnoid villi each day (! B). Lesions that ob-
tains the axons of ascending and descending struct the drainage of CSF (e.g., brain tumors)
tracts. result in cerebral compression; in children,
Brain (! D). The main parts of the brain are they lead to fluid accumulation (hydro-
the medulla oblongata (! D7) pons (! D6), cephalus). The blood–brain barrier and the
mesencephalon (! D5), cerebellum (! E), di- blood–CSF barrier prevents the passage of most
encephalon and telencephalon (! E). The substances except CO 2, O 2, water and lipophilic
medulla, pons and mesencephalon are collec- substances. (As an exception, the circum-
tively called the brain stem. It is structurally ventricular organs of the brain such as the or-
similar to the spinal cord but also contains cell ganum vasculosum laminae terminalis (OVLT;
bodies (nuclei) of cranial nerves, neurons con- ! p. 280) and the area postrema (! p. 238)
trolling respiration and circulation (! pp. 132 have a less tight blood–brain barrier.) Certain
and 212ff.) etc. The cerebellum is an important substances like glucose and amino acids can
control center for motor function (! p. 326ff.). cross the blood–brain barrier with the aid of
Diencephalon. The thalamus (! C6) of the carriers, whereas proteins cannot. The ability
diencephalon functions as a relay station for or inability of a drug to cross the blood–brain
most afferents, e.g., from the eyes, ears and barrier is an important factor in pharma-
skin as well as from other parts of the brain. cotherapeutics.
The hypothalamus (! C9) is a higher auto-
nomic center (! p. 330), but it also plays a
dominant role in endocrine function
(! p. 266ff.) as it controls the release of hor-
mones from the adjacent hypophysis (! D4).
The telencephalon consists of the cortex
310
and nuclei important for motor function, the
Despopoulos, Color Atlas of Physiology © 2003 Thieme
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