Lab 9: Neurology- Histology, Brain Anatomy, & Radiology

Figure 1. Anatomy of the human brain in the context of cranial nerves

1. Cerebrum

2. Pons

3. Medulla

4. Cerebellum

5. Spinal Cord

Figure 2. Midsagittal section of the brain illustrating the diencephalon and brain stem

1. Thalamus

2. Occipital lobe

3. Pineal gland

4. 4th Ventricle

5. Cerebellum

6. Spinal cord

7. Parietal Lobe

8. Corpus callosum

9. Septum pellucidum

10. Frontal lobe

11. Hypothalamus

12. Optic chiasm

13. Pituitary gland

14. Pons

15. Medulla oblonganta

Cerebrum 

• The cerebrum is the largest region of the brain and is divided into right and left cerebral hemispheres by the deep groove called the longitudinal fissure 

• Although largely symmetrical in structure, the two hemispheres are not entirely equal in function 

• Instead, there is lateralization (specialization) of some cortical functions

• The hemispheres are covered with a folded cerebral cortex of gray matter where neurons are not myelinated (Figure 3a and 3b) 

• A fold in the cerebral is called gyrus and a shallow groove is called a sulcus

• The cerebral hemispheres are connected by a white matter called the corpus callosum

Cerebrum 2

• Gray matter of the cerebral cortex forms the outer convoluted surface of the cerebral hemispheres and the foliated surface of the cerebellum

• White matter lies deep to the cerebral and cerebellar cortices

• Cortical gray matter is made of multipolar neuron cell bodies and attendant dendrites

• Deep to the gray matter, the bordering white matter is composed of tracts of myelinated axons that project from the overlaying gray matter

• The tracts can connect one cortical region to another, to brain nuclei, and to motor neurons of the spinal cord

• Many of the multipolar neurons of the cortex are classified as pyramidal cells due to the pyramid or triangular shape of their cell bodies

Cerebrum 3

• The cerebral cortex can be divided into five basic layers

1. The molecular layer contains mainly dendrites synapsing with cortical neuron axons

2. The outer granular layer is mostly made up of stellate cells, axons, and dendrites

3. The outer pyramidal cell layer is mostly made up of pyramidal cells that increase in size as you move deeper into the layer

4. The inner granular layer is mostly made of densely packed stellate cells

5. The inner pyramidal and polymorphic layer is mostly composed of larger pyramidal cells in the more superficial portion of the layer and a wide variety of cell morphologies in the deepest parts of the layer

Figure 3a. Cerebral cortex

1. Meninges

2. Molecular layer 

3. Outer granular layer 

4. Pyramidal cells

5. Gray matter

6. Inner granular layer 

7. Inner pyramidal cells 

8. Polymorphic cells 

9. White matter 

Figure 3b. Cerebral cortex

4. Pyramidal cells 

Diencephalon

• The diencephalon consists of three paired structures: the thalamus, hypothalamus, and epithalamus 

• These gray matter areas enclose the third ventricle 

• The thalamus is a relay station for incoming information, such as sensory information or integration information, destined for higher brain areas such as the cerebral cortex 

• The hypothalamus is the autonomic control center, center for emotional response, body temperature regulation, regulation of food intake, regulation of water balance and thirst, regulation of sleep-wake cycles, and control of endocrine system functioning

• Mammillary bodies are relay stations in the olfactory pathways 

• The infundibulum is a stalk of hypothalamic tissue that connects to the pituitary gland 

• The epithalamus contains the pineal gland that secretes the hormone melatonin that helps regulate the sleep-wake cycle 

Diencephalon 2

• The pineal gland (or pineal body) is located in the epithalamus which is the superior-most part of the diencephalon 

• The pineal gland is under the control of a complex feedback loop with the suprachiasmatic nucleus (SCN) of the hypothalamus

• The pineal gland secretes the hormone melatonin (an indoleamine derived from tryptophan) that regulates circadian rhythms

FIgure 4. Pineal gland

1. Neuroglial cells 

2. Pinealocytes