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The posterior pituitary releases the hormone oxytocin    , which stimulates uterine contractions during childbirth. The uterine smooth muscles are not very sensitive to oxytocin until late in pregnancy when the number of oxytocin receptors in the uterus peaks. Stretching of tissues in the uterus and cervix stimulates oxytocin release during childbirth. Contractions increase in intensity as blood levels of oxytocin rise via a positive feedback mechanism until the birth is complete. Oxytocin also stimulates the contraction of myoepithelial cells around the milk-producing mammary glands. As these cells contract, milk is forced from the secretory alveoli into milk ducts and is ejected from the breasts in milk ejection (“let-down”) reflex. Oxytocin release is stimulated by the suckling of an infant, which triggers the synthesis of oxytocin in the hypothalamus and its release into circulation at the posterior pituitary.

Hormonal regulation of metabolism

Blood glucose levels vary widely over the course of a day as periods of food consumption alternate with periods of fasting. Insulin and glucagon are the two hormones primarily responsible for maintaining homeostasis of blood glucose levels. Additional regulation is mediated by the thyroid hormones.

Regulation of blood glucose levels by insulin and glucagon

Cells of the body require nutrients in order to function, and these nutrients are obtained through feeding. In order to manage nutrient intake, storing excess intake and utilizing reserves when necessary, the body uses hormones to moderate energy stores. Insulin is produced by the beta cells of the pancreas, which are stimulated to release insulin as blood glucose levels rise (for example, after a meal is consumed). Insulin lowers blood glucose levels by enhancing the rate of glucose uptake and utilization by target cells, which use glucose for ATP production. It also stimulates the liver to convert glucose to glycogen, which is then stored by cells for later use. Insulin also increases glucose transport into certain cells, such as muscle cells and the liver. This results from an insulin-mediated increase in the number of glucose transporter proteins in cell membranes, which remove glucose from circulation by facilitated diffusion. As insulin binds to its target cell via insulin receptors and signal transduction, it triggers the cell to incorporate glucose transport proteins into its membrane. This allows glucose to enter the cell, where it can be used as an energy source. However, this does not occur in all cells: some cells, including those in the kidneys and brain, can access glucose without the use of insulin. Insulin also stimulates the conversion of glucose to fat in adipocytes and the synthesis of proteins. These actions mediated by insulin cause blood glucose concentrations to fall, called a hypoglycemic “low sugar” effect, which inhibits further insulin release from beta cells through a negative feedback loop.

This animation describe the role of insulin and the pancreas in diabetes.

Questions & Answers

what if cranium break
Alimamy Reply
it will cause a concussion and may affect the brain
INGIPHILE
how will it affect the brain?
Gaone
it may cause mechanical shock which might lead to a formation of a tumor and seizures
INGIPHILE
what are prokaryotes
Jacob Reply
Prokaryotes are cells with well defined nucleus or cells with membranes example; Bacteria,Nostoc etc.
Emmanuel
what is bilateral symmetry
Mameibi Reply
Explain kingdom of fungi
HARUNA Reply
what are the nutritional requirement of organism
Patience Reply
which part of the alimentary canal were these cross section taken
Getrude Reply
what is alimentary canal were these cross section taken
Getrude
what is matter
Gifty Reply
from which part of the alimentary canal were these cross section taken fig 2.1 fig 2.2 b,c
Getrude Reply
explain the role played by b in the alimentary canal
Getrude
what is biology
Sunday Reply
what is mitosis
David Reply
structure of a kidney
Idriss Reply
explain sexual reproduction of a named flower taking account of pollination, fertilization and the change to seed and fruit.
Chinyi Reply
The study of all life or living matterThe living organisms of a particular region.
Oyewale Reply
what is ology
Green Reply
in which of the following stages of the cell cycle are chromosomes pulled apart to opposite poles of the cell
Amie Reply
Anaphase
Jonah

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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