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THE BRAIN


COLLECTION: GOAT HANDBOOK
ORIGIN: United States
DATE INCLUDED: June 1992

Extension Goat Handbook

This material was contributed from collections at the National Agricultural Library. However, users should direct all inquires about the contents to authors or originating agencies.



DOCN 000000052
NO F-9
THE BRAIN
G. F. W. Haenlein R. Caccese; U. of Delaware, Newark
P. H. Sammelwitz; U. of Delaware, Newark
Anatomy and Physiology


1 The brain is composed almost entirely of nervous tissues and is the most highly specialized organ in the body of goats. It is partially a hollow structure consisting of a central system of ducts and cavities, surrounded by myelinated nerve fibers (white matter). It is enclosed by a three-layered mass of fibrous tissues known as the meninges or membranes, that provide protection to the brain. The outer layer, or dura mater, consists of a tough resilient material that adheres to the inner cranial walls. The middle layer covers the sulci and fissures of the brain, is very delicate and transparent and is called the arachnoidea. The inner layer or pia mater, is a vascular membrane processed tightly into the substance of the brain and spinal cord.

2 Hindbrain The rhombencephalon (hindbrain) consists of the medulla oblongata (the upper end of the spinal cord), the pons, cerebellum and the fourth ventricle. In this hindbrain are the glossopharyngeal, vagus, spinal accessory and hypoglossal nerves located; besides the respiratory and cardiac control centers, and areas that are essential for balance and sensations of touch.

3 More anterior originate the trochlear, trigeminal, abducens and facial nerves. It is also the area of entrance of the acustic nerve and the nucleus for the pneumotaxic center.

4 The cerebellum is located at the posterior end of the cranium, anterior to the medulla oblongata and dorsal to the pons. In cross section, the cerebellum has a tree-like appearance. It serves to maintain tonus, posture and equilibrium reflexes.

5 Midbrain To the mesencephalon (midbrain) belong the tectum, colliculi and the pineal (epiphysis), which is an endocrine gland, and has important regulatory functions in reproduction, behavior and circadian rhythms of goats; i.e. the biorhythms related to day and night light changes. Also found in the midbrain is the RAS or reticular activating system, anterior to the medulla oblongata, which is the sleep and waking center among other functions.

6 The corpora quadrigemina are four grayish hemispherical bodies that lie under the posterior part of the cerebral hemisphere. They consist of two pairs that are separated by a groove. In this region are situated the trochlear and oculomotor nerves and the neural paths connected with ocular reflexes.

7 Forebrain There are two main parts to the forebrain, the telencephalon and the diencephalon.

8 The inner-brain region (diencephalon) comprises the thalamus, hypothalamus, pituitary, mammillary bodies, optic tract and other structures grouped around the third ventricle, making up the central cavity of this division of the brain.

9 The thalamus is the largest structure of the diencephalon and is composed of two masses that are fused at right angles to one another. The thalamus contains the major link for the acustic nerves and is part of the behavior control system.

10 The hypothalamus is ventral to the thalamus and just above the pituitary gland. The division between the two structures is more of a physiological nature; the hypothalamus secreting hormones and many control substances, which the thalamus is not.

11 The hypothalamus only recently has been recognized as the master ''switchboard'' of body functions since sophisticated microtechniques became available for its research. To illustrate the problems involved, the isolation of 0.4 mg of the thyrotropic hormone-releasing factor from 120 lb of hypothalamuses represents the chemical extraction of 80,000 sheep brains. The hypothalamus is the main integrator of most antonomous activities of the goat, constituting the link between the two major control systems, the nervous and the endocrine systems. Neural fibers are received from the cerebral cortex and the hindbrain; efferent fibers go to the neurohypophysis, the thalamus, the vagus, parasymathetic and sympathetic centers; two hormones, oxytocin and vasopressin are secreted in the anterior parts of the hypothalamus; six hormone-releasing factors are liberated from nuclei of the hypothalamus into the adenohypophysis. Hence, the regulation of glandular secretion, the cardiovascular system, body temperature, respiration, heartbeat, metabolism of lipids, carbohydrates, proteins, minerals, water, regulation of sexual functions, hunger, thirst, obesity, lactation, milk let-down, sleep, wakefulness, emotional behavior, excitement, motivation, rage, appetite, satiety, blood pressure, curiosity, fear, aggression, sweating, salivation, stomach contraction, uterine contraction, kidney function, pupil dilation -- all are dependent on degrees of activities of specific parts of the hypothalamus of goats.

12 Below the hypothalamus is the pituitary (hypophysis), attached by a slender narrow stalk of nervous tissue, the infundibulum. The pituitary is recessed into a bony pocket surrounded by a network of small blood vessels and capillaries and is the master endocrine gland of the goat.

13 The telencephalon (end-brain) comprises the two cerebral hemispheres, the olfactory lobe and the ''old'' brain or subcortex containing among others the septum, amygdala, and hippocampus, which are very much involved in aspects of the behavior of goats.

14 The two cerebral hemispheres consist of an egg shaped mass with the broad end posteriorly situated and are divided by a deep fissure that runs medially through the cerebrum. White tissue, the corp ++++MISSING DATA++++

THE BRAIN
COLLECTION;GOAT HANDBOOK
ORIGIN;United States
DATE_INCLUDED;June 1992


 
 


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