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