Dairy Cattle Breeding and Selection Part 3

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:    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   1. Base of the Brain 2. Secretes Gonadotropins:    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:   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):       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:      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   a. Insulin – Breaks down sugars. b. Glucagon – breaks down starch to glucose. G. Adrenal  1. Located near the kidneys  2. Two glands:  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:     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.   a. Estrogen b. Progesterone  2. Also produces Placental lactogen.