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
• 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
• Excitation by Peripheral Sensory Signals
• Increased Activity of the Excitatory Area
Caused by Feedback Signals Returning
From the Cerebral Cortex
• Thalamus is a Distribution Center That Controls
Activity in Specific Regions of the Cortex
• A Reticular Inhibitory Area is Located in the
Lower Brain Stem
Activating—Driving Systems of the Brain
• 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
• Neurohormonal Systems in the Human Brain
a. Same three as in the rat plus
b. The acetylcholine system
Activating—Driving Systems of the Brain
• Neurohormonal Systems in the Human Brain
Fig. 58.2
Fig. 58.3
Activating—Driving Systems of the Brain
• Other Neurotransmitter and Neurohormonal
Substances Secreted in the Brain
Neurotransmitter Or Neurohormone
Enkephalin
ACTH
GABA
MSH
Glutamate
Neuropeptide Y
Vasopressin
Epinephrine
Histamine
Angiotensin II
Endorphins
Neurotensin
Limbic System
• Functional Anatomy of the Limbic System
Fig. 58.5 Limbic system showing the key position of the hypothalamus
Limbic System
• Functional Anatomy of the Limbic System
Fig. 58.4 Anatomy of the limbic system
Limbic System
• 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
• 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
• 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
• 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
• 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
• 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
• Functions of the Hippocampus
a. Role in learning
b. Theoretical function
•
Functions of the Amygdala
•
Functions of the Limbic Cortex