Mammalian Endocrine System
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- Region of lower brain that receives information from peripheral nerves and other brain regions. It controls much of the endocrine system. It contains two types of neurosecretory cells that release hormones into blood.
Two types of neurosecretory cells
1) Those that produce hormones that are stored in posterior pituitary. 2) Those that produce releasing hormones that regulate the anterior pituitary.
An appendage at the base of the hypothalamus consisting of 2 lobes:
Explain the pituitary gland components
Posterior pituitary (neurohypophysis).Anterior pituitary (adenohypophysis).
Arises from floor of hypothalamus during embryonic development.Stores and secretes 2 hormones:1) Oxytocin2) Vasopressin or Antidiuretic hormone (ADH)
Induces uterine muscle contraction during child birth.Stimulates milk ejection by breasts.- Necessary for human bonding.
Vasopressin o rantidiuretic hormone
-Stimulates water reabsorption by collecting ducts of the kidneys.
-Stimulates vasoconstriction and increased blood pressure.
-Increases paternal behavior and other bonding behaviors.
Anterior pituitary arises from where?
roof of the throat as an invagination of the pharynx, called Rathke's pouch
Anterior pituitary is regulated by what?
releasing hormones/ factors from the hypothalamus
- Releasing hormones from the __(i.e., GHRH, PRH, TRH, GnRH and CRH) are secreted into a __ leading to the __. They stimulate release of __ (i.e., GH, PR, TSH, FSH/LH and ACTH).
- capillary network
- anterior pituitary
- anterior pituitary hormones
Growth Hormone (GH)
- - Affects wide variety of tissue.
- -Stimulates entire body growth and organ enlargement.
- -Directly promotes growth of some tissue.
- - Indirectly promotes growth of other tissue by stimulating production of growth factors (e.g., somatomedins).
- - Structurally similar to GH although roles different.
- -Stimulates mammary gland development and milk synthesis in mammals.
- - Suppresses menstrual cycle and ovulation
Follicle-stimulating hormone (FSH)
- - A gonadotropic hormone, i.e., stimulates gonads.
- - In females, stimulates ovarian follicle growth and maturation and their production of estrogen.
- - In males, necessary for spermatogenesis, because stimulates Sertoli cells to nurture maturing sperm
- -A gonadotropic hormone.
- -In females, stimulates ovulation and corpus luteum to produce progesterone.
- - In males, necessary for spermatogenesis, because stimulates Leydig cells to produce testosterone
thyroid stimulating hormone (TSH)
- -Tropic hormone that stimulates the thyroid gland to produce its thyroxine (T4 and T3).
6) Adrenocorticotropic hormone (ACTH):
- Stimulates adrenal cortex to produce and secrete glucocorticoids (e.g., cortisol and cortisone).
Melanocyte-stimulating hormone (MSH)
- When present, simulates melanin synthesis by malanocytes causing darkening of the skin within 24 hours.
- However, MSH not secreted in adult humans and function unknown.
- -Peptide hormone
- -Opiate (opioid)
- -Body’s natural morphine…pain killer.
- -Produces euphoria
- Produces T3 (triiodothyronine) and T4 (thyroxine) derived from tyrosine.
- - T3 more active.
- - Thyroid hormones critical for regulating metabolism in mammals.
- - Hyperthyroidism causes high body temperature, sweating, weight loss, irritability and high blood pressure.
- - Hypothyroidism causes cretinism in infants, and weight gain, lethargy and cold-intolerance in adults.
Thyroid Gland Pt 2
- Goiter (enlarged thyroid) from dietary iodine deficiency.
- - Thyroxine controls metamorphosis in amphibians.
- - TSH from anterior pituitary ... cAMP...T4 and T3.
- - TSH regulated by TRH from hypothalamus.
- - High levels of T4 and T3 inhibit TSH.
- - Also produces hormone called calcitonin.
- Polypeptide hormone that lowers blood calcium levels.
- On surface of thyroid gland.
- - Produce parathyroid hormone (PTH).
- - PTH stimulates Ca2+ uptake by kidneys and bone resorption by osteoclasts to release Ca2+ into blood.
- - PTH antagonizes effect of calcitonin and needs vitamin D to function.
- Islets of Langerhans:
- - Each islet has alpha cells and beta cells.
- - Alpha cells produces glucagon (peptide hormone)
- - Beta cells produce insulin (protein hormone).
- - Insulin and Glucagon work antagonistically to maintain blood glucose levels near 90 mg/ml.
- - Glucose is the major energy source for cellular respiration and a key source of carbon.
- Lowers blood sugar by stimulating glucose uptake by most cells of the
- 2) Slows glycogen breakdown and Inhibits conversion amino acids into sugar by
- 1) Increases blood sugar concentrations by stimulating the hydrolysis of glycogen and conversion of amino acids into sugar, in liver.
- Caused by insulin deficiency or loss of response to insulin in target tissues.
- - occurs in childhood
- - insulin dependent
- - insulin injections several times/day
- Adults over 40
- - insulin deficiency and/or decreased responsiveness
- - non-insulin dependent
- - exercise and diet
The adrenal gland is made of __
adrenal cortex and medulla
- Medulla contains cells that produce catecholamine hormones (i.e., epinephrine and norepinephrine) from tyrosine.
- - under control of acetylcholine
Epinephrine: stimulates release of blood sugar by liver and skeletal muscle, and fatty acids from fat.
Epinephrine and norephinephrine together
Epinephrine and Norepinephrine together: increase heart rate, stroke volume, shunt blood away from skin, gut and kidneys to skeletal muscle and heart and brain.
__ types of __ hormones
- glucocorticoids (cortisol)
- 2) mineralocorticoids
- release regulated by ACTH
- - promote glucose synthesis form proteins.
- - immunosuppressive
- promotes salt and water retention by kidneys.
- - release not under ACTH control
Glucocorticoids are really __
immunosuppresants. They will suppress your immune system.
If there’s a physiological marker, its __
cortisol. If your cortisol levels are higher, you ARE more stressed
What will the outer layer of the cortex do?
- -Outer layer makes aldosterone (steroid)
- Will stimulate sodium and indirectly water reabsorption by distal tubules
EFFECT OF MINERALOCORTICOIDS
- 1) retention of soidium ions and water by kidneys
- 2) increases blood volume and blood pressure
Effects of glucocorticoids
- 1) proteins and fats broken down and converted to glucose, leading too increased blood glucose
- 2) possible suppression of immune system
Effects of epinephrine and norepinephrine
- 1) glycogen broken down to glucose; increased blood glucose
- 2) increased bp
- 3) increased breathing rate
- 4) increased metabolic rate
- 5) change in blood flow patterns, leading to increased alertness and decreased digestive, excretory, and reproductive system activity
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