Bio of Psychology: The Endocrine System Flashcards
The ____ is fast-acting with relatively short term effects
nervous system
The ____ takes longer to communicate signals but has generally longer lasting effects
endocrine system
–> regulates physiology (especially metabolism) over a period of hours to days
Can neurons signal the release of hormones from endocrine glands?
Yes
Primary connection btw the nervous and endocrine systems (axis)
Hypothalamic-pituitary axis
Hormone
Signal of the endocrine system, secreted into the bloodstream by an endocrine gland, and has effects on distant target cells possessing the appropriate receptor
Endocrine Gland
Ductless gland whose secretory products are picked up by capillaries supplying blood to the region
Exocrine glands
Secrete their products into the external environment by way of ducts, which empty into the gastrointestinal lumen or the eternal world
Hormone receptor (what is it?) What happens when ligand (hormone) binds?
A polypeptide that has a ligand-specific binding site
When hormone binds to the site it causes the receptor to modify target cell activity
2 classes of hormones:
Hydrophilic hormones: peptides and amino-acid derivatives-must bind to receptors on the cell surface
Hydrophobic hormones: steroid hormones-bind to receptors in the cellular interior
Peptide Hormones
Synthesized in rough ER, modified in golgi
Stored in vesicles until needed and then released by exocytosis
Hydrophilic, so dissolve in plasma in bloodstream
Communicate with interior of target cell by second messenger cascades
What activates the second messenger cascade?
The polypeptide receptor with a domain on the inner surface of the plasma membrane
End result of 2nd messenger activation?
The function of proteins in the cytoplasm has changed
Key feature of 2nd messenger cascade?
Signal amplification, which allows a few activated receptors to change the activity of many enzymes in the cytoplasm
What do peptide hormones do and how long are their effects?
They modify modify the activity of existing enzymes in the cytoplasm, so their effects are exerted rapidly, minutes to hours from the time of secretion and duration of effects is brief
2 subgroups of peptide hormones:
Polypeptides and amino acid derivatives
Ex. Insulin
- Polypeptide Hormone
- Complex tertiary structure involving disulfide bridges
- Secreted by B cells of the pancreatic islets of langerhans in response to elevated blood glucose and binds to a cell-surface receptor with a cytoplasmic domain possessing protein kinase activity
Amino Acid derivatives
Derived from a single amino acid and contain to peptide bonds
Ex. Catecholamines (includes epinephrine) and thyroid hormones
- Tyrosine is parent amino acid for these
- Catecholamines act like peptide hormones and thyroid hormones are more like steroid hormones
Epinephrine
Small cyclic molecule secreted by the adrenal medulla upon activation of the sympathetic nervous system; binds to cell-surface receptors to trigger a cascade of events that produces the 2nd messenger cAMP and activates protein kinases in the cytoplasm
Thyroid hormones
Incorporate iodineinto structure
Enter cell, bind to DNA, and activate transcription of genes involved in energy mobilization
Steroid hormone
- Hydrophobic
- Synthesized from cholesterol in the smooth ER
- Freely diffuse through biological membranes
- Not stored and diffuse into bloodstream as soon as they are made (if it’s not needed it won’t be made)
- Hydrophobic, so can NOT be dissolved in the plasma, so they journey through bloodstream stuck to proteins in the plasma, such as albumin
- Steroid stays bound to plasma protein by hydrophobic interactions, no bonds
- Exerts effects by diffusing through plasma membrane to bind to receptor in the cytoplasm
- Once it binds ligand, the steroid hormone-receptor complex is transported to the nucleus, where it acts as a sequence-specific regulator of transcription
What do steroid hormones do and how long are their effects?
They modify transcription by changing the amount and/or type of proteins in the cell
Their effects are exert slowly, over a period of days, and persist for days to weeks
Steroids regulating sexuality, reproduction, and development are secreted by:
The testes, ovaries, and placenta
Steroids regulating water balance and other processes are secreted by”
The Adrenal Cortex
All other endocrine glands secrete:
Peptide hormones
**Thyroid hormone is derived from an amino acid but behaves more like a steroid hormone
Regulation of the endocrine system is not preplanned or structured but:
(and type of regulation)
Automatic
- Hormone levels rise and fall according to physiological needs
- Feedback regulation
Ex. of feedback regulation with calcitonin and serum [Ca2+]
- Function of calcitonin is to prevent serum [Ca2+] from peaking above normal levels
- The amount of calcitonin secreted is directly proportional to increases in serum [Ca2+] above normal
- When Ca2+ become elevated, calcitonin is secreted
- Then when Ca2+ levels fall, calcitonin secretion stops
- Falling Ca2+ levels (that which is regulated) feeds back to the cells which secrete calcitonin (regulators)
- Ca2+ levels is a physiological endpoint which must be maintained at constant levels
- ->This demonstrates the role of the endocrine system in maintaining homeostasis, or physiological consistency
Tropic Hormones
Hormones that regulate hormones
Meta-Regulators, superimposed upon the hormonal regulation of physiological endpoints
Feedback regulation applies to tropic hormones, ex. level of ACTH is influenced by the level or cortisol; when cortisol is needed, ACTH is secreted, and when the serum [cortisol] increases enough, ACTH secretion slows
Tropic Hormone ex. ACTH
- Secreted by the anterior pituitary
- Role is to stimulate increased activity of the adrenal cortex, which is responsible for secreting cortisol
- This is a tropic hormone because it does not directly affect physiological endpoints, but regulates another regulator (cortisol)
Cortisol
Regulates physiological endpoints, including cellular responses to stress and serum [glucose]
Hypothalamus
Controls much of the endocrine system; located at the center of the brain
Controls the endocrine system by releasing tropic hormones that regulate other tropic hormones–>called releasing and inhibiting factors/hormones
Ex. hypothalamus secretes CRH, whose role is to cause increased secretion of ACTH
ACTH secretion is regulated by feedback inhibition from cortisol, and CRH secretion is also inhibited by cortisol
–> Controls the anterior pituitary which controls most of the endocrine system
Hypothalamic-pituitary control axis
The hypothalamus exerts its control of the pituitary by secreting hormones into the bloodstream, just like any other endocrine gland
Hypothalamic-pituitary portal system
Special mini circulatory system provided for efficient transport of hypothalamic releasing and inhibiting factors to the anterior pituitary
Blood supply
Pressure drops or increases in the capillaries??
DROPS
Hepatic Portal System
Form gastrointestinal tract to the liver
Anterior Pituitary also known as:
Adenohypophysis
Posterior pituitary also known as:
Neurohypophysis
Anterior Pituitary
-Normal endocrine gland controlled by hypothalamic releasing and inhibiting factors (tropic hormones)
Posterior Pituitary
- Composed of axons which descend form the hypothalamus
- Hypothalamic neurons that send axons down to the posterior pituitary are an example of neuroendocrine cells, which are neurons that secrete hormones into the bloodstream
Hormones of the posterior pituitary
ADH (or vasopressin)-causes the kidney to retain water in times of thirst
Oxytocin-causes milk let-down fro nursing as well as uterine contractions during labor
All hypothalamic and pituitary hormones are what kind of hormone?
Peptides
Thyroid Hormone
- Produced from AA tyrosine in thyroid gland and comes in 2 forms, with 3 or 4 iodine atoms per molecule
- Production of thyroid hormone is increased by TSH from the anterior pituitary, which is regulated by the hypothalamus and the CNS
- Thyroid hormone binds to receptor in cytoplasm of cells and then regulates transcription in the nucleus
Effect of regulation of thyroid hormone on transcription in nucleus?
To increase overall metabolic rate and body temp, and in children to stimulate growth
–> exposure to cold can increase the production of of thyroid hormone
Cortisol
- Secreted by the adrenal cortex in response to ACTH from the pituitary
- The effects of cortisol help the body deal with stress
- Also helps to mobilize glycogen and fat stores to provide energy in times of stress and also increases the consumption of proteins fro energy
What effect does an inhibitor of protein synthesis have on thyroid hormone?
Effects would not be seen because TH binds to a receptor that regulates transcription , and the mRNA stimulated by TH receptor in the nucleus must be processed and translated before effects of TH are seen
