Endocrine System Flashcards
What are hormones?
Molecules produced by the endocrine system.
Function of hormones
- Send messages to parts of the body
- Maintain homeostasis
- Regulate body’s processes (hunger, bp, sex drive)
Exocrine Glands
Secrete through ducts to the outside of the body
Ex: digestive enzymes
Endocrine Glands
Lack ducts and secrete hormones into the blood
Endocrine System
Consists of ductless glands scattered throughout the body. These glands secrete hormones which travel through blood to target cells.
- Target cells have receptors for binding with specific hormone
- Regulates or directs particular function
Hydrophilic Hormones
Peptide hormones and catecholamine’s, water loving
Lipophilic Hormones
Steroid hormones and thyroid hormone, lipid loving
Endocrine only function
Pituitary, parathyroid, thyroid, and the adrenal gland
Mixed function
Pineal, hypothalamus, thymus, heart, stomach, pancreas, duodenum, kidney, skin, adipose tissue, ovaries, placenta, and testes
Influences of concentration of hormones in plasma
- Hormone rate of secretion
- Rate of metabolic activation or conversion
- Transport (binding to plasma proteins)
- Inactivation (excretion)
Regulation of secretion
- Negative feedback
- Neuroendocrine reflexes ability of nervous system to regulate secretion
- Diurnal (circadian) rhythms
Endocrine dysfunction
Commonly result from abnormal plasma concentrations of a hormone via inappropriate rates of secreation
Types of endocrine dysfunction
- Hyposecretion
- Hypersecretion
Hyposecretion
Too little hormone is secretion
Primary hyposecretion
Too little hormone is secreted because of abnormality within gland
Secondary hyposecretion
Too little secretion of hormone due to deficiency of its tropic hormone, no problem with gland
Hypersecretion
Too much hormone is secreted
Causes of hypersecretion
- Tumors that ignore normal regulatory input and continuously secrete excess hormone
- Immunologic factors
Primary hypersecretion
Too much hormone is secreted due to abnormality within gland
Secondary hypersecretion
Excessive stimulation from outside the gland causes over-secretion
How can hormones influence activity of another hormone at given target cell?
- Permissiveness
- Synergism
- Antagonism
Permissiveness
One hormone must be present in adequate amounts for full exertion of another hormone’s effect
Synergism
Occurs when actions of several hormones are complimentary
- Combined effect is greater than the sum of their separate effects
Antagonism
Occurs when one hormone causes loss of another hormone’s receptors
- Reduces effectiveness of second hormone
Hypothalamus
Endocrine organ (secretes several hormones); most of them affect the pituitary
Pituitary Gland
Pea-sized gland connected to the hypothalamus via the infundibular stalk
- Posterior pituitary
- Anterior Pituitary
Posterior Pituitary
Neurohypophysis; composed of nervous tissue
Anterior Pituitary
Adenohypophysis; consists of glandular epithelial tissue
What is released from the pituitary gland?
Human growth hormone (hGH)
Adrenocorticotropin (ACTH)
Thyroid stimulating hormone (TSH)
Gonadotropic hormones
- Luteinizing hormone (LH)
- Follicle stimulating hormone (FSH)
Prolactin (PRL)
Vasopressin
Oxytocin
Magnocellular Neurons
Secrete two hormones (neurohormones); vasopressin and oxytocin; synthesized and packaged into vesicles that are transported to posterior pituitary
ADH/Vasopressin
Conserves water during urine formation
Oxytocin
Stimulates uterine contraction during childbirth and milk ejection during breast-feeding
Vasopressin in kidneys
Nephrons in kidneys, increase permeability of distal and collecting tubules to H2O
Vasopressin arterioles
Throughout body, causes constriction
Hypothalamic-Hypophyseal Portal System
System that provides a vascular link to the anterior pituitary from the hypothalamus
Posterior Pituitary Hormones
Vasopressin and oxytocin
Anterior Pituitary Hormones
TSH
ACTH
FSH
LH
GH
PRL