Chapter 58: Behavioral and Motivational Mechanisms of the Brain—The Limbic System and the Hypothalamus

Guyton and Hall, Textbook of Medical Physiology, 12 edition

Activating—Driving Systems of the Brain

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Control of Cerebral Activity by Continuous Excitatory Signals from the Brain Stem

a. Reticular excitatory area of the brain stem-sends signals upward and downward b. Downward-to spinal cord reflexes and to maintain tone in the antigravity muscles c. Upward through the thalamus (two signals) 1. Rapid transmission to excite the cerebrum 2. Build up progressively for seconds to minutes

Activating—Driving Systems of the Brain

Fig. 58.1 Excitatory-activating system of the brain

Activating—Driving Systems of the Brain

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Excitation by Peripheral Sensory Signals

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Increased Activity of the Excitatory Area Caused by Feedback Signals Returning From the Cerebral Cortex

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Thalamus is a Distribution Center That Controls Activity in Specific Regions of the Cortex

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A Reticular Inhibitory Area is Located in the Lower Brain Stem

Activating—Driving Systems of the Brain

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Neurohormonal Control of Brain Activity-Three Systems Studied in the Rat

a. Norepinephrine system-excitatory and can go to every area of the brain b. Dopamine system-can be both excitatory and inhibitory; goes to specific brain regions c. Serotonin system-inhibitory; goes to specific brain regions

Activating—Driving Systems of the Brain

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Neurohormonal Systems in the Human Brain

a. Same three as in the rat plus b. The acetylcholine system

Activating—Driving Systems of the Brain

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Neurohormonal Systems in the Human Brain

Fig. 58.2

Fig. 58.3

Activating—Driving Systems of the Brain

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Other Neurotransmitter and Neurohormonal Substances Secreted in the Brain Neurotransmitter Or Neurohormone

Enkephalin ACTH GABA Glutamate MSH Neuropeptide Y Vasopressin Histamine Endorphins Epinephrine Angiotensin II Neurotensin

Limbic System

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Functional Anatomy of the Limbic System

Fig. 58.5 Limbic system showing the key position of the hypothalamus

Limbic System

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Functional Anatomy of the Limbic System

Fig. 58.4 Anatomy of the limbic system

Limbic System

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Hypothalamus, a Major Control Center for the Limbic System

a. Has two-way communicating pathways with all levels of the limbic system; sends output signals in three directions: 1. To the brain stem (mesencephalon, medulla, and pons) and then to the ANS 2. To higher areas of the diencephalon and cerebrum 3. To the infundibulum to control secretions of the anterior and posterior pituitary

Limbic System

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Hypothalamus, a Major Control Center for the Limbic System

b. Vegetative and endocrine control functions of the hypothalamus c. Areas that cause specific activities are not as accurately localized as suggested in the following figures

Limbic System

Fig. 58.6 Control centers of the hypothalamus

Limbic System

Fig. 58.7 Coronal view of the hypothalamus

Limbic System

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Behavioral Functions of the Hypothalamus and Associated Limbic Structures

a. Effects caused by stimulation of the hypothalamus 1. Lateral-thirst and eating; increases the general level of activity (possibly rage and fighting) 2. Ventromedial nucleus-satiety, decreased eating, and tranquility 3. Periventricular nuclei-fear and punishment reactions 4. Anterior and posterior hypothalamus-sex drive

Limbic System

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Behavioral Functions of the Hypothalamus and Associated Limbic Structures

b. Effects caused by hypothalamic lesions 1. Bilateral lesions-decrease eating and drinking to zero; extreme passivity 2. Ventromedial areas-excessive eating and drinking; hyperactivity; continuous rage and savagery

Limbic System

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Reward and Punishment Function of the Limbic System

a. Reward centers b. Punishment centers c. Rage-association with punishment centers d. Placidity and tameness

Limbic System

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Importance of Reward and Punishment on Behavior

a. Effect of tranquilizers on reward and punishment b. Importance in learning and memory

Specific Functions of Other Parts of the Limbic System

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Functions of the Hippocampus

a. Role in learning b. Theoretical function •

Functions of the Amygdala

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Functions of the Limbic Cortex