E

Figure

The chemical composition of Lewy bodies, which are characteristic of the brains of people with Parkinson disease, may provide clues to the cause of the condition.

Basal — ganglia

Caudate nucleus

Putamen

Globus pallidus

Caudate nucleus

Putamen

Globus pallidus

Longitudinal fissure

Right cerebral hemisphere

Cerebellum

Spinal cord

Figure 11.19

A coronal section of the left cerebral hemisphere reveals some of the basal nuclei.

Thalamus Hypothalamus Brain stem

Figure 11.19

A coronal section of the left cerebral hemisphere reveals some of the basal nuclei.

Longitudinal fissure

Right cerebral hemisphere

Cerebellum

Spinal cord

Optic nerve Optic tract

Optic chiasma

Optic nerve Optic tract

Mammillary body."'

Pituitary gland

Pons

Optic chiasma

Pituitary gland

Mammillary body."'

Pons

Dorsalview Spinal Cord

Spinal cord

Pyramidal tract

Figure 11.20

(a) Ventral view of the brain stem. (b) Dorsal view of the brain stem with the cerebellum removed, exposing the fourth ventricle.

Thalamus

Pineal gland

Third ventricle Hypothalamus

Superior colliculus Inferior colliculus

Pyramidal tract

Spinal cord

Thalamus

Pineal gland

Third ventricle Hypothalamus

Superior colliculus Inferior colliculus

Cerebellar peduncles

Medulla oblongata

Cerebellar peduncles

Medulla oblongata

Figure 11.20

(a) Ventral view of the brain stem. (b) Dorsal view of the brain stem with the cerebellum removed, exposing the fourth ventricle.

synchronicity of action potentials, therefore, may be a way that the thalamus selects which stimuli to relay to higher brain structures. Therefore, the thalamus is not only a messenger but also an editor.

Nerve fibers connect the hypothalamus to the cerebral cortex, thalamus, and parts of the brain stem so that it can receive impulses from them and send impulses to them. The hypothalamus maintains homeostasis by regulating a variety of visceral activities and by linking the nervous and endocrine systems. The hypothalamus regulates

1. Heart rate and arterial blood pressure.

2. Body temperature.

3. Water and electrolyte balance.

4. Control of hunger and body weight.

5. Control of movements and glandular secretions of the stomach and intestines.

6. Production of neurosecretory substances that stimulate the pituitary gland to release hormones that help regulate growth, control various glands, and influence reproductive physiology.

7. Sleep and wakefulness.

Structures in the region of the diencephalon also are important in controlling emotional responses. For example, portions of the cerebral cortex in the medial parts of the frontal and temporal lobes connect with the hypothalamus, thalamus, basal nuclei, and other deep nuclei. Together, these structures comprise a complex called the limbic system.

The limbic system controls emotional experience and expression and can modify the way a person acts. It produces such feelings as fear, anger, pleasure, and sorrow. The limbic system seems to recognize upsets in a person's physical or psychological condition that might threaten life. By causing pleasant or unpleasant feelings about experiences, the limbic system guides a person into behavior that may increase the chance of survival. In addition, portions of the limbic system interpret sensory impulses from the receptors associated with the sense of smell (olfactory receptors).

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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