Period 4 Chapter 45
The Endocrine System
Endocrine Vs. Nervous
- The endocrine system coordinates slower and longer response to stimulus.
- Regulates growth and homeostatic processes.
- The nervous system coordinates response to sudden environmental changes through high-speed electrical signals.
Negative and Positive Feedback
- Negative Feedback: the response from the effector reduces the initial stimulus.
- Positive Feedback: the response triggers amplification of the stimulus, leading to a greater response
Hormones Protein vs. Steroids
- Protein hormones are water-soluble.
- Protein hormones bind to the receptor extracellularly (on the surface of a target cell).
- Steroid hormones are not water-soluble.
- Steroid hormones bind to the receptor intracellularly (inside the cell).
Hormone and Receptor Interaction
- Hormone and receptor interactions are based on the target cell, the receptor, and the species.
- the process in which local
- regulators convey messages
- between neighboring cells.
- (Short distance signaling)
- An example of this would be prostagladins, which help induce fever and inflammation as well as intensify pain.
Ligands and Ligand-gated Channels
- A ligand is a molecule that binds specifically to a receptor side of another molecule.
- A ligand-gated channel is a type of membrane receptor, which has a “gate.”
- When the ligand binds to the receptor, the gate opens and specific ions can flow through and change the concentration of that ion in the cell. This may directly change the activity of the cell.
- G-protein linked receptor is a plasma membrane that works with G proteins.
- When activated by a signal molecule, the receptor causes a G protein to activate.
- The G protein then binds to an enzyme and alters its activity.
- Receptor tyrosine kinases is characterized by enzymatic activity.
- When bonded to a signal molecule, the two polypeptide receptors touch.
- When fully activated, the receptor proteing is recognized by proteins in the cell.
- The proteins bind to a phosphorylated tyrosine and undergo structural change.
- Each activated protein triggers a transduction pathway.
- A second messenger relays a signal to a cell’s interior in response to a signal received by a signal receptor protein.
- Second messengers are small, nonprotein, water-soluble molecule or ion.
- Examples: calcium ion, or cyclic AMP.
Duct and Ductless Glands
- Duct glands are glands that secrete their messengers through ducts.
A duct is a vessel, canal, or tube that conveys body fluids, especially secretions and excretions.
- Ductless glands are glands that secrete their chemical messengers directly to extracellullar fluid.
Hypothalamus and Anterior Pituitary
- It is on the underside of the brain that receives information from throughout the body and brain and initiates endocrine signals to adapt to the conditions.
- The anterior pituitary is a fold of tissue at the roof of the embryonic mouth. It is stimulated by the tropic hormones of the hypothalamus. It secretes at least six different hormones.
- Both the hypothalamus and anterior pituitary control the secretion of the thyroid gland.
Thyroid & Parathyroid Glands
- The thyroid gland stimulates and maintains metabolic processes.
- It also secretes calcitonin to lower blood calcium levels.
- The parathyroid gland secretes prathyroid hormones to raise calcium blood levels.
- They are four small structures, embedded in the surface of the thyroid.
- A Deficiency in Iodine in a person’s diet can result in a goiter.
- A goiter is an enlargement of the thyroid gland.
- Without sufficient iodine, the thyroid gland can’t synthesize adequate amounts of triiodothyronine and thyroxine.
- This causes low blood levels of the two and negative feedback on the hypothalamus and anterior pituitary to be altered.
- This causes the anterior pituitary to continuously secrete TSH and enlarge the thyroid.
- The thymus gland is a peptide that secretes thymosin.
- This stimulates the production of certain infection-fighting cells, especially the maturation of T cells.
- The pancreas regulates blood sugar in the body.
- It secretes insulin and glucagon.
- When blood glucose levels become to low, glucagon is secreted and broken down by the liver into glucose and released into the blood.
- When blood glucose levels become to high, insulin is secreted to cause liver to take and store glucose as glucagon.
- Epinephrine is secreted from the adrenal medulla.
- They are part of the class of compounds, catecholamines.
- It works directly on several target tissues and give the body a rapid bioenergetic boost.
- It also increases both the rate and the stoke volume of the heartbeat and dilate the bronchioles in the lungs, which increase the rate of oxygen delivery to body cells.
- FSH and LH are secreted by GnRH in the hypothalamus.
- These hormones control the synthesis of androgens and estrogens.
Gonadal Sex Hormones
- The gonads secrete three types of hormones.
- Androgens- stimulate the development and maintenance of the male reproductive system and human male secondary sex characteristics.
- Estrogens- responsible for the maintenance of the female reproductive system and female secondary sex characteristics.
- Progestins- involved in preparing and maintaining the uterus in mammals, which supports the growth and development of the embryo.