chapter 45: hormones and the endocrine system Flashcards
What are hormones?
chemical signals secreted into circulatory system
What are the two systems that coordinate communication throughout the body?
- endocrine system
- nervous system
What is the role of the endocrine system?
it secretes hormones that coordinate slower but longer-acting responses like..
1. reproduction
2. development
3. energy metabolism
4. growth
5. behaviour
What is the role of the nervous system?
convyes high-speed electricl signals along specialized cells called neurons
How does endocrine signalling work?
hormones secreted into extracellular fluids by endocrine cells reach their targets in bloodstream.
this maintains homeostasis, mediates responses to stimuli and regulates growth and development
What are local regulators?
molecules that act over short distances, reaching target cells solely by diffusion
- prostaglandins
What is paracrine signalling?
target cells near the secreting cells
- blood pressure regulation, nervous system function, reproduction
What is autocrine signalling?
target cell is also secreting cell
- blood pressure regulation, nervous system function, reproduction
How does signalling by pheromones work?
- mark trails leading to food
- define territories
- warning of predators
- attracting potential mates
What are the chemical classes of intercellular signalling factors?
- polypeptides - water-soluble
- amines - water-soluble
- steroid hormones - lipid-soluble
What is special about lipid-soluble hormones?
they pass easily through cell membranes whereas water-soluble hormones do not.
What are the protein and amide signalling factors?
- proteins incoded in genes
- insulin: inactive prohormone polypeptide secreted when needed to reduce blood sugar
- growth factors: regulates cell cycle - amine hormones; signalling factors produced from amino acids
What are the lipid signalling factors?
prostaglandins promote fever and inflammation, steroids are derived from cholesterol
What is the cellular response pathway for water-soluble hormones?
- are secreted by exocytosis
- they travel freely in bloodstream
- they bind to cell-surface receptors
What is the cellular response pathway from lipid-soluble hormones?
- they diffuse across cell membranes
2, they travel in the bloodstream bound to transport proteins - they bind to receptors in the cytoplasm or nucleus
- binding initiates signal transduction pathway
- results in gene expression
What does the hormone epinephrine (adrenaline) responsible for?
has multiple effects in mediating the body’s response to short-term stress
What is the pathway of epinephrine?
- it binds to receptors on the plasma membrane of liver cells
- this triggers the release of messenger molecules that activate enzymes
- one response in the cell is the activation of an enzyme that breaks down glycogen which results in the release of glucose int o the bloodstream
What are endocrine glands?
endocrine cells grouped in ductless organs
What are exocrine glands?
salivary glands have ducts to carry secreted substances onto body surfaces or into body cavities
What are some major human endocrine glands?
- thyroid gland
- hypothalamus
- ovaries
- adrenal glands
What is a simple endocrine pathway?
stimulus happens to endocrine cell
endocrine cell releases hormone
hormone circulates throughout body via blood
hormone reaches target cells
response activated by target cells
What is the pathway of a simple neuroendocrine pathway?
- stimulus is recieved by a sensory neuron
- this stimulates neurosecretory cell
- this secretes neurohormone that enters and travels bloodstream to target cells
What is oxytocin?
the love hormone
What is negative feedback?
loop inhibitd response by reducing inital stimulus, preventing excessive pathway activity
What is positive feedback?
reinforces a stimulus to produce an even greater response
What hormones controls molting and development in insects?
PTTH
juvenile hormone
ecdysone
What is the function of the pineal gland?
- secretes melatonin
- release of melatonin is controlled by SCN neurons
What is the function of the hypothalamus?
- intergrating the endocrine and nervous system
- receives information from nervous system and initiates response through endocrine signalling
What is the role of the hypothalamus-pituitary axis?
- oxytocin regulates milk secretion by mammary glands
- ADH regulates physiology and behaviour
- hormone production in anterior pituitary is controlled by releasing and inhibiting hormones secreted from hypothalamus
What is the role of the thyroid?
- If thyroid hormone levels drops, hypothalamus secretes TRH causing anterior pituitary to secrete TSH, stimulating release of thyroid hormone by thyroid gland
What is hypothyroidism?
too little thyroid function, can lead to weight gain, cold intolerance
What is hyperthyroidism?
excessive production of thyroid hormone, can lead to high temperature, sweating, weight loss, high blood pressure
What is the role of the growth hormone?
- is secreted by pituitary gland
- promotes growith
- stimulates production of growth factors
What is the role of parathyroid glands?
- regulates calcium levels in blood with help of PTH (increases level of Ca+ and calcitonin decreases Ca+ levels
What is the role of the adrenal gland
- is associated with the kidneys
- produce hormones that help regulate your metabolism, immune system, blood pressure, response to stress and other essential functions.
What is the role of the testicles and ovaires?
- produces sex hormones: androgens, estrogens and progestins
- testicles mainly synthesize androgens: testosterone, stimulating development of male reproductive system
