Ganong's Review of Medical Physiology, 23rd Edition

CHAPTER 16Control of Posture & Movement 255

afferent inputs, the mossy and climbing fibers, send collaterals
to the deep nuclei and pass to the cortex. There are four deep
nuclei: the dentate, the globose, the emboliform, and the fas-
tigial nuclei. The globose and the emboliform nuclei are
sometimes lumped together as the interpositus nucleus. The
cerebellar cortex contains five types of neurons: Purkinje,
granule, basket, stellate, and Golgi cells. It has three layers
(Figure 16–14): an external molecular layer, a Purkinje cell
layer that is only one cell thick, and an internal granular layer.
The Purkinje cells are among the biggest neurons in the body.
They have very extensive dendritic arbors that extend
throughout the molecular layer. Their axons, which are the
only output from the cerebellar cortex, generally pass to the
deep nuclei. The cerebellar cortex also contains granule cells,
which receive input from the mossy fibers and innervate the

Purkinje cells. The granule cells have their cell bodies in the

granular layer. Each sends an axon to the molecular layer,

where the axon bifurcates to form a T. The branches of the T

are straight and run long distances. Consequently, they are

called parallel fibers. The dendritic trees of the Purkinje cells

are markedly flattened (Figure 16–14) and oriented at right

angles to the parallel fibers. The parallel fibers thus make syn-

aptic contact with the dendrites of many Purkinje cells, and

the parallel fibers and Purkinje dendritic trees form a grid of

remarkably regular proportions.

The other three types of neurons in the cerebellar cortex are

in effect inhibitory interneurons. Basket cells (Figure 16–14)

are located in the molecular layer. They receive input from the

parallel fibers and each projects to many Purkinje cells (Fig-

ure 16–15). Their axons form a basket around the cell body

FIGURE 16–13 Superior and inferior views and sagittal section of the human cerebellum. The 10 principal lobules are identified by
name and by number (I–X).

Superior surface

Inferior surface

MIDSAGITTAL SECTION

Centralis Culmen

Culmen

Primary fissure

Declive

Superior cerebellar Fourth ventricle

peduncle

Middle cerebellar

peduncle

Nodulus of

vermis Uvula

Flocculus

Anterior medullary velum

Inferior cerebellar peduncle

II III IV V Primary fissure

Lobulus simplex VI

Folium

Tuber

VII

Pyramis VIII

Prepyramidal sulcus

Uvula IX

Posterolateral fissure

Nodulus X

Fourth ventricle

Pons

Lingula I