Transcript Dairy Cattle Breeding & Selection

Dairy Cattle Breeding & Selection
Reproduction
“Endocrinology”
Topic Objectives:
 1. Describe the inter-relationship between
the Endocrine system and the Nervous
system.
 2. Describe the origin and function of the
major hormones involved with reproduction.
I. Introduction
A. Look at the two systems.
 1. Endocrine System
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
a. Causes slower and longer lasting changes
within the body.
b. Examples:
1)
 2)
 3)
 4)

Growth
Reproduction
Lactation
Secondary Sex Characteristics
 2. Nervous System
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a. Causes rapid changes and/or adjustments
within the body.
b. Examples:

1) Immediate reaction to any kind of stress such as:
 a) Pain
 b) Fear
 c) Heat
 d) Exertion
 e) Etc.
B. The two systems work
together as one system.
 1. Called the Neuroendocrine System.

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a. Referred to this way because of the
overlapping effect each system has on the other.
b. Example: Adrenaline will cover up the
effects of oxytocin.
C. Definitions to Know
 1. Hormone: Chemicals synthesized from the
endocrine glands that influence activities of other
organs within the body.

Example: The ovary produces estrogen, progesterone, and
relaxin, all of which affect the body in different ways.
 2. Neurohormone: Chemicals synthesized in the
central nervous system (or in the neuron; nerve cell)
that influence activities of other organs within the
body.

Example: FSH, LH (both produced in the anterior pituitary
gland) and Oxytocin (produced in the posterior pituitary
gland).
 3. Neuroendocrine System: A combination
of the endocrine system and the central
nervous system working harmoniously.
II. Hormone Secretions in the
Female are brought about in
two ways.
 A. External Affects (Conditions occurring
outside the body: i.e.: Environment)

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1. Temperature changes: Extreme heat for
example will cause the blood to circulate faster.
2. Improper handling of cattle causes the system
to speed up due to adrenaline secretions.
 B. Internal Affect (Conditions occurring
inside the body: i.e.: Estrous Cycle)
III. Classifications of Glands
A. Endocrine
 1. Internal ductless glands that discharge
their secretions directly into the blood stream
which then transports them to their place of
action.
 2. Secretion is a hormone that may also be
called a chemical messenger.
 3. Their job is to activate or bring about a
change in the body.
 4. Hormones have two main purposes:
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
a. Excitatory: Activates an organ to do
something.
b. Inhibitory: To inhibit or stop something from
functioning.
 5. There are two major groups of Endocrine
organs based on the type of secretion.

a. Only Hormones and not other enzymes or
substances produced and released in the body:

1) Examples:
 a) Thyroid
 b) Parathyroid
 c) Pituitary
 d) Adrenals
 e) Pineal
 f) Thymus

b. Hormones and other enzymes or substances
produced and released into the body:

1) Example
 a) Pancreas – Insulin
 b) Testes – Spermatozoa – Testosterone
 c) Ovary – Egg – Progesterone, Estrogen
 d) Stomach – Gastric Juice & Enzymes
 e) Intestine – Digestive Enzymes
B. Exocrine Glands
 1. Glands that discharge their secretions by
ducts to various parts of the body or to the
outside of the body.


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a.
b.
c.
d.
Mammary System
Urinary System
Sweat Glands
Etc.
IV. Overview of the Endocrine
and Central Nervous Systems
A. Both coordinate body functions and in many
cases it takes both to perform the functions of
reproduction.
B. In general the secretions (Neurohormones)
from the Central Nervous System stimulate the
Endocrine Glands into actions sot hey will secrete
their hormones…FSH, LH, Etc.
 C. Basic function of the Central Nervous
System is to control rapid adjustments of body
to changes in the
environment…Stress=Adrenalin Release.
 D. Basic function of the Endocrine System is
to regulate body changes more
slowly…Growth, Lactation, Reproduction,
etc.
V. Four Main Parts of the
Nervous System
 A. Brain – Control Center
 B. Spinal Cord – carries messages or
neurohormone to and from various parts of
the body.
 C. Peripheral Nervous System – Voluntary –
All nerve cells outside the brain and spinal
cord…except those nerves controlling the
visceral organs (heart, stomach, etc.)

1. These nerves are routes of communication
between the central nervous system and the internal
and external environment. (Afferent and Efferent
Nerves)
a. Afferent (Sensory) nerves – to the spinal cord.
 b. Efferent (Motor) nerves – to the reactor organ or
muscle.

 D. Autonomic Nervous System –
Involuntary and acts automatically: Controls
the Visceral organs. (Stress the system and
the neurohormone “Epinephrine/Adrenalin”
inhibits milk let down as it blocks oxytocin).
Includes two systems:
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1. Sympathetic: This system tends to decrease
secretion and constrict blood flow.
2. Parasympathetic: Antagonistic System tends
to induce secretion and dilation blood vessels.
VI. Neuron
 A. Basic cell of the Central Nervous System
is the neuron.
 B. Contains the following:

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1. Cell Body: Control center.
2. Axon: Terminals that conduct impulses away
from the cell body.
3. Dendrites: Terminals that conduct impulses
to the cell body.
 C. Nerve Impulses travel over one or more
nerve cells to the spinal cord to the brain and
then back to an effector organ such as a
gland or muscle. The impulse may not
always go to the brain before going to the
effector organ.
VII. Brain
 A. Composed of Four parts:

1. Cerebrum: Includes the Pituitary and
Hypothalamus.
a. This is the largest part of the brain.
 b. Center or reasoning, thinking and voluntary muscle
control.
 c. Registers various sense…sight, smell, hearing.

 B. Cerebellum
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1. Coordinates such activities as eating, walking.
 C. Pons
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1. Coordinates breathing, swallowing,
rumination.
 D. Medulla Oblongata

1. Works in cooperation with the Pons.
VIII. Spinal Column
 A. A caudal extension of the Medulla
Oblongata.
 B. Delivers messages to and from the brain.
 C. Afferent nerves carry messages from
parts of the body to the spinal cord.
 D. Efferent Nerves carry messages from the
spinal cord of parts of the body.
IX. Miscellaneous: Hormones
may have two or more purposes
to the system.
 A. Oxytocin for example:
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1. Initiates Milk Let-Down and also
2. Causes Uterine contraction during Estrus and
also
3. During Parturition
X. Location and Function of
the Neuroendocrine Glands
 A. Anterior Pituitary
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1. Base of the Brain
2. Secretes Gonadotropins:
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a. F.S.H. (Follicle Stimulating Hormone) to stimulate the ovary
to produce an egg.
b. L.H. (Luteinizing Hormone) to cause the follicle to rupture
and release the egg.
c. I.C.S.H. (in the male…Interstitial Cell Stimulating Hormone)
to stimulate the interstitial cells to produce and release
testosterone.

d. Also produces the following:
 1) Prolactin – Lactogenic Hormone ( Milk).
 2) G.H. – Growth Hormone
 3) T.S.H. – Thyroid Stimulating Hormone – induces the thyroid to
take iodine from the blood for normal thyroid function.
 4) A.C.T.H. – Adrenocorticortropic Hormone (Stress hormone –
causes the system to speed up…also one of the steroid type of
chemicals).
B. Posterior Pituitary
 1. Base of the brain
 2. Secretes the following neurohormones:
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
a. Ocytocin – responsible for milk letdown and
reproductive contractions.
b. A.D.H. – Antidiuretic Hormone: Control
urine collection in the bladder and fluid
concentration in the kidney. (Also water balance
in tissue.)
C. Hypothalamus
 1. Just in front of the Anterior Pituitary and the
Cerebrum.
 2. Regulates secretions of the Anterior Pituitary.
 3. Produces Releasing Hormones (H) or factors (F):
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a.
b.
c.
d.
e.
f.
Gonadotropin Releasing Hormone (GnRH)
GRF – Stimulates GH release.
Somatostatin – Inhibits GH release
TRH – Stimulates TSH (also prolactin and GH) release
CRF – Stimulates ACTH release.
Prolactin Inhibiting Factor (Inhibits Prolactin release).
D. Thyroid
 1. Two lobes located on each side of the Trachea just below
the Larynx.
 2. The Thyroid needs iodine to function properly and if not
the thyroid keeps getting larger (Goiter).
 3. Its secretions affect indirectly almost all of the body
functions:
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a. Carbohydrate and Protein Synthesis
b. Utilization of Oxygen
c. Milk Production
d. Secretes Thyroxine, Triiodothyronine and Calcitonin
e. In general…it affects the metabolism which the system operates; i.e.: a
dry cow compared to a cow milking heavy in her 2nd month of her
lactation.
E. Parathyroid
 1. Located just below the Thyroid
 2. Produces Parathyroid hormone that is
necessary for the synthesis and utilization of
Calcium and Phosphorus.
F. Pancreas
 1. Located on the small intestine.
 2. Secretes Digestive Enzymes
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a. Insulin – Breaks down sugars.
b. Glucagon – breaks down starch to glucose.
G. Adrenal
 1. Located near the kidneys
 2. Two glands:
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a. Adrenal Cortex – 29 known functions: primarily it
maintains mineral balance in the blood and fluids in the
tissue.

1) Produces:
 a) Glucocorticoids
 b) Mineralocorticoids

b. Adrenal Medulla – Secretes
neurohormones…Epinephrine and Norepinephrine: in short
this is Adrenalin. (Without this to help fight stress the
animal would die…necessary to speed up the heartbeat,
etc…(Fight or Flight Hormone)).
I. Ovary (Female)
 1. Reproductive Organ of the Female that:
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a. Produces Estrogen (Estradiol) from its
Graffian Follicles.
b. Produces Progesterone from its Corpus
Luteum.
c. Produces Relaxin.
d. Produces Inhibin – that inhibits FSH.
I. Testes (Male)
 1. Interstitial Cells produce Testosterone.
 2. Seminiferous Tabules produce
spermatozoa.
J. Placenta
 1. The main two hormones produced.
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a. Estrogen
b. Progesterone
 2. Also produces Placental lactogen.
THE END