Endocrine system Flashcards
What is a hormone?
a regulatory substance produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action.
Describe the endocrine system
glands, tissues, and cells that secrete hormones.
contrast endocrine with exocrine glands
Endocrine glands
-No ducts
-Contain dense, fenestrated capillary networks which allow easy uptake of hormones into bloodstream
-Internal secretions
-Intracellular effects such as altering target cell metabolism
Exocrine glands
-Have ducts; carry secretion to an epithelial surface or the mucosa of the digestive tract
-external secretions
-Extracellular effects (food digestion)
Nervous system vs endocrine system
Nervous system
-Electrical impulses are the messengers in the nervous system
-Brain and the spinal cord constitute the nervous system
-Nerve impulses are transmitted through neurons
-The nervous system is under both voluntary and involuntary control
-Nerve impulses make use of the neurotransmitters at synaptic clefts and sodium and potassium channels and enter the target cells.
-Responses are localized
Endocrine system
-Hormones are the chemical messengers in the endocrine system that target cells through the bloodstream
-Glands and organs like thyroid, pituitary glands and reproductive organs (ovaries and testes) are involved in the endocrine system
-Hormones are transmitted through blood vessels
-The endocrine system is under involuntary control
-The hormones enter into the target cells by diffusing through the plasma membrane or by binding to the cell receptors
-Responses are widespread
describe the anatomical relationships between the hypothalamus and pituitary gland
The hypothalamus forms the floor and walls of the third ventricle of the brain. It regulates primitive functions of the body ranging from water balance and thermoregulation to sex drive and childbirth. Many of its functions are carried out by way of the pituitary gland.
list the hormones produced by the hypothalamus
Thyrotropin-releasing hormone(TRH)
Gonadotropin-releasing hormone(GnRH)
Growth hormone-releasing hormone(GHRH)
Corticotropin-releasing hormone(CRH)
Somatostatin
Anterior pituitary produces what hormones?
Growth hormone
Thyroid stimulating hormone
Adrenocorticotropic hormone
Luteinizing Hormone
Melanocyte-Stimulating Hormone
Posterior pituitary gland produces what hormones?
Antidiuretic hormone
Oxytocin
Effects of growth hormone?
growth hormone (GH), also called somatotropin or human growth hormone, peptide hormone secreted by the anterior lobe of the pituitary gland. It stimulates the growth of essentially all tissues of the body, including bone.
describe the structure and location of endocrine glands
Hypothalamus: This gland is located in your brain and controls your endocrine system. It uses information from your nervous system to determine when to tell other glands, including the pituitary gland, to produce hormones. The hypothalamus controls many processes in your body, including your mood, hunger and thirst, sleep patterns and sexual function.
Pituitary: This little gland is only about the size of a pea, but it has a big job. It makes hormones that control several other glands such as the thyroid gland, adrenal glands, ovaries and testicles. The pituitary gland is in charge of many different functions, including how your body grows. It’s located at the base of your brain.
Thyroid: Your thyroid is a butterfly-shaped gland in the front of your neck. It’s responsible for your metabolism (how your body uses energy).
Parathyroid: These four tiny glands are no larger than a grain of rice. They control the level of calcium in your body. For your heart, kidneys, bones and nervous system to work, you need the right amount of calcium.
Adrenal: You have two adrenal glands, one on top of each kidney. They control your metabolism, blood pressure, sexual development and response to stress.
Pineal: This gland manages your sleep cycle by releasing melatonin, a hormone that causes you to feel sleepy.
Pancreas: Your pancreas is part of your endocrine system, and it plays a significant role in your digestive system too. It makes a hormone called insulin that controls the level of sugar in your blood.
Ovaries: In women, the ovaries release sex hormones called estrogen, progesterone and testosterone. Women have two ovaries in their lower abdomen, one on either side.
Testes: In men, the testes (testicles) make sperm and release the hormone testosterone. This hormone affects sperm production, muscle strength and sex drive.
identify the chemical classes to which various hormones belong.
- amino acid derivatives
- peptide hormones
- lipid derivatives
describe how hormones are synthesized and transported to their target organs
The glands of the endocrine system secrete hormones directly into the extracellular environment. The hormones then diffuse to the bloodstream via capillaries and are transported to the target cells through the circulatory system.
describe how hormones stimulate their target cells
Hormones mediate changes in target cells by binding to specific hormone receptors. In this way, even though hormones circulate throughout the body and come into contact with many different cell types, they only affect cells that possess the necessary receptors.
Explain how target cells regulate their sensitivity to circulating hormones
Target cells can adjust their sensitivity to a hormone by changing the number of receptors for it.
In up-regulation, a cell increases the number of hormone receptors and becomes more sensitive to the hormone.
Down regulation is the process in which a cell reduces its receptor population, and this becomes less sensitive to a hormone.
Up-regulation makes a cell more sensitive to its receptor Down-regulation makes a cell less sensitive.
describe how hormones affect each other when two or more of them stimulate the same target cells;
synergistic effects: two or more hormones act together to produce an effect that is greater than the sum of their separate effects.
Permissive effects: one hormone enhances the target organs response to a second hormone to come later.
Antagonistic effects: One hormone opposes the action of another.
