Ch 45 Endocrine System Flashcards
Hormones
Chemical signals
Where are hormones secreted into?
The circulatory system
Hormones serve what purpose?
Communicating regulatory messages within the body
What allows hormones only to effect target cells?
Receptors on those target cells for the specific hormone
What two systems coordinate internal communication?
1) Endocrine system
2) Nervous system
Endocrine system
Secretes hormones that coordinate slower, but longer-acting responses
Nervous system
Conveys high-speed electrical signals along neurons
What do signals within the nervous system do?
Regulate other cells
Neurons
Specialized cells of the nervous system
Endocrine signaling maintains what?
Homeostasis
Endocrine signaling mediates what?
Responses to stimuli
Endocrine signaling regulates what?
Growth and development
Local regulators
Molecules that act over short distances
How do local regulators reach target cells?
Solely by diffusion
Two types of signaling that produces local regulators
1) Paracrine signaling
2) Autocrine signaling
Paracrine signaling
Target cells lie near the secreting cells
Act locally by diffusing to nearby target cells
Autocrine signaling
Target cell is also the secreting cell
Have regulatory action on the cell that produces them
Endocrine glands
Small, ductless glands that release hormones into blood vessels
Synapses
Specialized junction formed between neurons and target cells
Neurons secrete what?
Neurotransmitters
Neurotransmitters
Molecules that diffuse short distances and bind to receptors on target cells
Neurosecretory cells
Specialized nerves in the brain that secrete neurohormones into the circulatory system
Three major classes of molecules that function as hormones
1) Polypeptides
2) Amines
3) Steroids
What two major classes of molecules that function as hormones are also water soluble?
1) Polypeptides
2) Amines
What major class of molecules that function as hormones are also lipid soluble?
Steroids
Water soluble hormones freely diffuse into what?
The blood
Water soluble hormones bind to what?
Signal receptor proteins in cell membranes
How do lipid soluble hormones enter the circulatory system?
Bound to transport proteins
Once in the circulatory system, how do lipid soluble hormones reach their target cells?
Freely diffusing through cell membranes
Hormones binding to membrane receptor proteins activate what?
Second-messengers within the cell
Second-messengers serve what purpose?
They are used in multiple reactions
Second-messenger activation amplifies what?
The hormone’s signal and activates kinases
Kinases
Molecules that regulate enzymes
Steroids hormones (estrogen, testosterone) bind to proteins located where?
In the cytoplasm
What happens after steroid hormones bind to proteins in the cytoplasm?
The hormone-receptor complex enters the cell nucleus and activates/inhibits transcription of specific genes
Genetic code leaves the nucleus in what form?
Messenger RNA
Ribosomes
Translate mRNA into polypeptides
How do members of the same animal species sometimes communicate?
With pheremones
Pheremones
Chemicals that are released into the environment
Functions of pheremones
1) Marking trails leading to food
2) Defining territories
3) Warning of predators
4) Attracting potential mates
The same hormones may have different effects on target cells that have different…
1) Receptors for the hormone
2) Signal pathways
3) Proteins for carrying out the response
Can a hormone have different effects in different species?
Yes
Epinephrine has multiple effects in mediating what?
The body’s response to short-term stress
Epinephrine binds to receptors on the plasma membrane of what?
Liver cells
Binding of epinephrine and liver cells triggers what?
The release of messenger molecules that activate enzymes and result in the release of glucose into the bloodstream
Simple hormonal negative feedback loops
The product of the hormonal response has a negative effect on the stimulation of further hormone release
Antagonistic hormones
Have opposite effects and forms a homeostatic system of negative feedback loops
Insulin
Reduces blood glucose by promoting uptake of glucose by cells and production of glycogen by the liver
Glucagon
Increases blood glucose by stimulating breakdown of glygogen to glucose
Type 1 diabetes mellitus (insulin-dependent)
Autoimmune disorder in which the immune system destroys pancreatic beta cells
Type 2 diabetes mellitus (non-insulin-dependent)
Involves insulin deficiency or reduced response of target cells due to change in insulin receptors
Major endocrine glands
1) Hypothalamus
2) Pineal gland
3) Pituitary gland
4) Thyroid gland
5) Parathroid glands
6) Adrenal glands
7) Pancreas
8) Kidney
9) Ovaries
10) Testes (males)
Organs containing endocrine cells
1) Thymus
2) Heart
3) Liver
4) Stomach
5) Kidney
6) Small intestine
Hypothalamus
Receives information from the nervous system and initiates responses through the endocrine system
What is attached to the hypothalamus?
Pituitary gland
What two structures compose the pituitary gland?
1) Posterior pituitary
2) Anterior pituitary
Posterior pituitary
Stores and secretes hormones that are made in the hypothalamus
Anterior pituitary
Makes and releases hormones under regulation of the hypothalamus
Tropic hormones effect what?
The release of other hormones
Growth Hormone (GH)
Secreted by the anterior pituitary gland and has tropic and nontropic actions and diverse metabolic effects
Growth hormone stimulates the production of what?
Growth factors
What causes gigantism?
An excess of growth hormone
What causes dwarfism?
Lack of growth hormone
Hormone cascade pathway
A hormone can stimulate the release of a series of other hormones, the last of which activates a nonendocrine target cell
Do hormone cascade pathways typically involve negative or positive feedback?
Negative feedback
The release of thyroid hormone to increase metabolism results from what?
A hormone cascade pathway involve the hypothalamus, anterior pituitary, and thyroid gland
Adrenal gland
Releases hormones that regulate the stress response
Where is the adrenal gland located?
On top of the kidney’s
Two glands that make up the adrenal gland
1) Adrenal medulla
2) Adrenal cortex
Adrenal medulla
Inner portion of adrenal gland
Rapid response
Adrenal cortex
Outer portion of adrenal gland
Long-term response
Three sex hormones
1) Androgens
2) Estrogens
3) Progestrins
Are all three sex hormones found in males, females, or both?
Found in both males and females, but in different proportions
Testes primarily synthesize what sex hormones?
Androgens
Primarily testosterone
Testosterone
Stimulates development and maintenance of the male reprodcutive system
Estrogens
Responsible for maintenance of the female reproductive system and the development of female secondary sex characteristics
What is the most important estrogen?
Estradiol
Progestins serve what purpose in mammals?
Primarily involved in preparing and maintaining the uterus
Pineal gland
Secretes melatonin
Located in the brain
What controls the release of melatonin?
Light and dark cycles
The primary functions of melatonin appear to relate to what?
Biological rhythms associated with reproduction
