FINAL: Endocrine System Flashcards
What does regulation of homeostasis require
Sensory input, integration and communication between organs
What is the nervous system
Made of nervous tissue
- electrical signals and chemical messages (neurotransmitters)
- fast, direct communication to target tissue
What is the endocrine system
Made of glandular tissue (secretes something)
- chemical messages (hormones)
- slower, indirect communication to target tissue (must have receptors)
Hormones are either….
Steroid or protein (non-steroid)
What is a steroid
- Made from cholesterol (a type of lipid)
- Ex. Testoterone and estrogen
What are protein hormones
- typically polar and/or negatively charged
- made from amino acids
- ex. Insulin
How do hormones interact with target cells to alter the function of the cell (usually by making new proteins)
- A hormone travels through the bloodstream
- from source gland to target tissue - Target tissue is determined by receptors
- receptors are proteins in the plasma membrane (for protein hormones) or cytoplasm (steroid hormones) - Receptors act like switches to turn on or off gene expression
- causes molecular changes
- primarily activation (or synthesis) of proteins
Hormone/receptor complex must be terminated
Example of steroid hormone action
Where are the digestive endocrine glands located
Pancreas, liver
Where are the reproductive endocrine glands located
Gonads (testes, ovaries)
Where are the nervous endocrine glands located
Hypothalamus, pituitary gland, pineal gland
What organs are unique to the endocrine system
Thyroid, parathyroid and adrenal glands
Function of the anterior pituitary gland
Synthesize and secrete hormones (a true endocrine gland)
Function of the posterior pituitary gland
Store and secrete hormones (extension of neural tissue, not an endocrine gland)
Function of the pituitary gland
Regulate many endocrine organs throughout body ( regulation is called an axis )
What does the hypothalamic-pituitary axis involve
It involves the hypothalamus, anterior pituitary, endocrine glands and target cells
How does the hypothalamic -pituitary axis regulate
- hypothalamic neurons produce hormones (typically a releasing hormone (RH))
- RH triggers release of hormone from pituitary gland (hormone 1)
- Hormone 1 triggers release of hormone 2 from another endocrine gland
- hormone 2 causes change in target tissue
(Also limited hypothalamic production of RH hormones = negative feedback)
Example of growth hormone and growth hormone releasing hormone forming an negative feedback loop
Effects of growth hormone
Wide ranging effects
- affects metabolism
- stimulates liver to produce insulin like growth factors (IGFs)
What are IGFs
Hormones that stimulate growth
- increase division of chondrocytes
- increase activity of osteoblasts
- triggers hypothalamus to produce somatostatin (which inhibits GH)
What is gigantism
In children an increase in height at epiphyseal plates, due to overproduction of growth hormone
- usually the result of a tumor on the pituitary gland
What is acromegaly
In adults, the thickening of the bones (growth in width) due to overproduction of growth hormone
- usually the result of a tumor on the pituitary gland
GH levels throughout a lifespan
Why do we stop growing
- GH levels drop after puberty
- Sex hormone levels peak at puberty
- Includes estrogen (produced by gonads: ovaries and testes)
- Estrogen stimulates osteoblasts and inhibits osteoclasts
How does the closure of epiphyseal plates occur
- during puberty high GH levels stimulate chondrocyte division
- at the same time, rising estrogen levels stimulate osteoblasts activity
- osteoblasts eventually “out-compete” chondrocytes and the epiphyseal plate completely ossifies = no more growth
What is achrondroplastic dwarfish
Alteration in a gene that affects the epiphyseal plate
Limits the division of chondrocytes in epiphyseal plate
Mostly affects the limbs
What is osteoporosis
When bone resporption outpaces bone deposition
Spongy bone is most vulnerable
It commonly occurs in older women as estrogen levels drop
What is the parathyroid hormone
An important hormone that helps to regulate free calcium concentrations in our body
- secreted by the parathyroid glands located in the neck, closely associated with the thyroid gland
What is hydroxyapatite
The mineralized ground substance found in osseous tissue
What is hypocalcemia
Low blood calcium levels
- Parathyroid hormone is released to bring blood calcium back to ideal range by stimulating osteoclasts to release bone calcium into the blood stream
What is hypercalcemia
High blood calcium levels
- calcitonin is released to inhibit osteoclasts and activate osteoblasts, returning blood calcium to ideal range
