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Hormones and the Endocrine System
Hormones and the Endocrine System (ch. 45)
Intercellular communication: endocrine, paracrine, autocrine, synaptic, and neuroendocrine signaling
The ways signals are classified are usually by two characteristics: the type of secreting cell and the route that is taken by the signal when trying to get to its intended target.
The following figure explains each type of signalling: endocrine, paracrine, autocrine, synaptic, and neuroendocrine
Water-soluble vs. Lipid-soluble hormones
Such as peptides and derivatives of amino acids.
Repelled by fats/lipids, like the lipids in cell and nucleus membranes.
They are soluble to water, so they will easily travel in blood
they tend to bind to receptors that are outside of the cell, because they can not cross the membrane.
Such as sex hormone steroids (estrogen, androgen, etc.)
Lipid soluble, water repellent
They usually travel in a special carrier protein, so they can go through the water.
These special carrier proteins are soluble to water and lipid, so they can carry peptide and amino acid derivatives into lipid "areas", and they can carry sex hormone steroids into water "areas"
A molecule that when secreted, influences molecules all around from where it was secreted.
Coordination of endocrine and neuroendocrine signaling
In all animals (excluding simple invertebrates), the endocrine and nervous systems coordinate together to control reproduction and development
Example: Life Cycle of butterfly
butterflies grow in stages
PTTH (prothoacicotropic hormone) helps the process go, this eventually leads to a successful molt.
Juvenile Hormone (JH): As the process goes on, JH goes down, as it becomes an adult.
The figure below describes the rest of the details.
Simple endocrine and neuroendocrine pathways
Simple endocrine pathways
endocrine cells directly respond to an internal or environmental source by secreting a secreting a certain hormone. The hormone travels through the bloodstream to the target cells, in which it will interact with specific receptors.
Simple neuroendocrine pathways
Rather than the environment or an internal source, the cells respond to a sensory neuron, which stimulates a neurosecretory cell. That cell then secretes a neurohormone that diffuses into the bloodstream and it travels to its target cells.
Negative feedback: A form of regulation in which accumulation of an end product slows the process
Positive feedback: A form of regulation in which the lack of an end product speeds up the process.
Negative feedback and positive feedback combined is what is known as Feedback regulation.
Blood glucose control in humans, effects of diabetes mellitus
Blood glucose control in humans
When glucose is high in system, causes negative feedback, and the release of insulin into the system
When glucose is low in the system, cuases positive feedback, and the release of glucagon into the system.
An endocrine disease that causes the body to be unable to regulate glucose levels
type 1 results from autoimmune destruction of insulin secreting cells
type 2 results from reduced responsiveness of target cells to insulin; obesity and lack of exercise increase chances for type 2 diabetes.
90% of people with diabetes have type 2 diabetes.
Coordination of endocrine and nervous systems in vertebrates: hypothalamus and pituitary function and hormones
the hypothalamus controls: autonomic nervous system, thirst, hunger, temperature in the body, pituitary gland, and emotions.
The hormones of the hypothalamus are Oxytocin and Antidiuretic hormone (ADH)(aka vasopressin), but these hormones are released by the posterior pituitary gland.
Functions of the Pituitary gland
The pituitary gland controls: metabolism, growth/maturation, sexuality, reproduction, etc.
Pituitary gland hormones
Hormones of the Pituitary gland
Hormones of the Posterior Pituitary gland
Oxytocin: stimulates contraction of uterus and mammary glands
Antidiuretic Hormone (ADH) (aka vasopressin): promotes water retention in the kidneys
Hormones of the Anterior Pituitary gland
Growth Hormone (GH): Stimulates growth(especially in bones) and metabolic functions
Prolactin: Stimulates the production and secretion of milk
Follicle-Stimulating Hormone (FSH): stimulates production of ova and sperm
Luteinizing Hormone (LH): Stimulates ovaries and testes
Thyroid-Stimulating hormone (TSH): Stimulates the thyroid gland
Adrenocorticotropic hormone (ACTH): Stimulates adrenal cortex to secrete glucocorticoids
Other major human endocrine glands and hormones: thyroid, parathydroid, adrenal, pineal
Hormones of the Thyroid gland
Triiodothyronine (T3) and thyroxine (T4): Stimulate and maintain metabolic processes.
Calcitonin: Lowers blood calcium levels
Hormones of the Parathyroid gland
Parathyroid hormone (PTH): raises blood calcium levels
Hormones of the Adrenal Gland
Hormones of the Adrenal Medulla
Epinephrine and norepinephrine: Raises blood glucose level;increases metabolic activity;constricts certain blood vessels
Hormones of the Adrenal cortex
Glucocorticoids: Raises blood glucose level
Mineralcorticoids: Promotes reabsorption of Na+ and excretion of K+ in the kidneys
Hormones of the Pineal gland
Melatonin: Involved in biological rhythms (sleep)
Tropic vs. nontropic hormones
Nontropic hormones are hormones that directly stimulate target cells to induce effects.
Growth hormone (GH)
Tropic hormones are hormones that target other endocrine glands.
Thyroid-stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
Luteinizing Hormone (LH)
Follicle-stimulating hormone (FSH)
growth hormone (GH)
Growth hormone can be both tropic and nontropic
Blood calcium regulation in humans
Blood calcium levels are maintained using feedback regulation
When blood calcium levels are low, this causes positive feedback, and the release of PTH
When blood calcium levels are high, this causes negative feedback, and the release Calcitonin
Stress response in vertebrates
Overview of gonadal sex hormones
Hormones of the testes
Androgens: Supports sperm formation;promotes development and maintenance of male secondary sex characteristics
Hormones of the ovaries
Estrogens: Stimulates uterine lining growth;promotes development and maintenance of female secondary sex characteristics.
Progestins: Promotes uterine lining growth
A foreign molecule that interrupts the normal function of a hormone pathway
diethylstilbestrol (DES) was a perscription drug that was given to pregnant women who were at risk of having complications (between 1938 and 1971)
Daughters of women who took DES tended to have more reproductive abnormalitites, such as vaginal and cervical cancer, structural changes in reproductive organisms, and increasked risk of miscarriage.
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