(E1, L2) The Endocrine System Flashcards
What is endocrinology?
the study of the endocrine glands and their associated hormones
What is a neurohormone?
A hormones that is released by a neuron, or neurosecretory cell (vs. a hormone released by a non-neural cell is just a hormone)
What is neuroendocrinology?
The study of the transduction of a neural signal into a hormonal signal
Chemical messenger
any substance that is produced by a cell that affects the function of another cell
Cytokine
A chemical messenger that evokes proliferation (cell reproduction) of other cells, especially in the immune system
Neuromodulator
a hormone that changes the response of a neuron to some other factors
Neuropeptide
peptide hormone produced by a neuron
Neurosteroid
steroid hormone produced by a neuron
nuerotransmitter
a chemical messenger that acts across the neural synapse
What are the systems of chemical mediation?
Intracrine mediation
Autocrine mediation
Paracrine mediation
Endocrine mediation
Ectocrine mediation
What is intracrine mediation?
Intracrine substances regulate intrecellular events (inside the cell
What is Autocrine mediation?
Autocrine substances feed back to influence the same cells that secreted them. (go out of cell then back in, binds to own cell receptor)
What is Paracrine mediation?
paracrine cells secrete chemicals that affect adjacent cells (essentially like neurotransmission)
What is endocrine mediation?
endocrine cells secrete chemicals into the bloodstream, where they may travel to distant target cells
What is ectrocrine mediation?
Ectrocrine substances, such as pheromones, are released into the environment by individuals to communicate with others (pheromones, for example)
What is the difference between endocrine and exocrine cells?
Endocrine cells release hormones into the bloodstream, exocrine cells send it out into the environment (salivary, sweat, mammary glands, ect)
Hypothalamus
- Master control of hormone secretions
- Takes info from both outside and inside, then decides what hormones to release in response (not all, but most hormonal release)
Pineal gland
reproductive maturation; body rhythms
Pituitary gland
Anterior pituitary and posterior pituitary
Anterior pituitary
hormone secretion by thyroid, adrenal cortex, and gonads; growth
Posterior pituitary
water balance; salt balance
Thyroid
growth and development; metabolic rate
Adrenal glands
Adrenal cortex (outer bark), Adrenal medulla (inner core)
Adrenal cortex
Salt and Carbohydrate metabolism; inflammatory reactions
Adrenal medulla
Emotional arousal; stress response
Pancreas
sugar metabolism
Gut
Digestion and appetite control
Gonads
(testes/ovaries) Body development; maintenance of reproductive organs in adults
What makes up the hypothalamus?
- Several collections of cell bodies, or nuclei
- Comprised of neurosecratory cells –> modified neurons that recieve info via NTs, but then release hormones (neural info into hormonal secretion)
Describe the hypothalamic-pituitary axis
Hypothalamus communicates with pituitary in 2 ways:
1. Neurohormones reach the anterior pituitary via the portal system, then cause the AP to release its own hormones (releasing hormones; caused by something)
2. A completely different set of hypothalamic neurosecretory cells directly innervates the posterior pituitary, where it releases neurohormones into general circulation (direct, into bloodstream)
What are the four main classes of hormones?
- Protein and peptide hormones
- Steroid hormones
- Monoamines
- Lipid-based hormones
How do the four classes of hormones differ?
- mode of release
- how they move through the blood
- the location of their target cells’ receptors
- mechanism of action at the receptor
What are peptide and protein hormones?
- made up of amino acids
- only a few amino acids in length–> peptide hormones
- larger ones –> protein hormones
- most common type in mammals
- can be stored in endocrine cells (in vesicles) and released via exocytosis
- large –> can’t pass through cell membranes, need receptors
- fast
What are the 3 domains of peptide and protein hormone receptors?
- An extracellular domain- binds ligand
- a transmembrane domain
- a cytoplasmic domain
(Two kinds: intrinsic enzymatic activity and second messenger)
What are steroid hormones?
- derived from cholesterol
- most come from adrenal glands, gonads and brain
- small and lipophilic (passes through cell membranes)
- never stored, so released immediately upon production
- some require carrier proteins to help move them through blood
- slow (hours to days)
- receptors are inside the cell
What are monoamine hormones?
- derived from a single amino acid
- two classes of these hormones affect behavior: indolamines and catecholamines
- thyroid hormones are also monoamines, but they don’t affect behavior
What are lipid-based hormones?
- possess a 20-carbon fatty acid skeleton
- prostaglandins are the largest family of these
- 4 different groups distinguishable by differences in cyclopentyl group of fatty acid skeleton
- Effects: wide array of biological actions, often have opposing effects
What are the anterior pituitary hormones?
(peptides and protein)
- anterior pituitary releases tropic hormones in respons to the releasing hormones of the hypothalamus
- Luteinizing hormone (LH)
- Follicle-stimulating hormone (FSH)
- Thyroid-stimulating hormone (TSH)
- Growth hormone (GH)
- Prolactin
- Adrenocorticotropic hormone (ACTH)
What are the posterior pituitary hormones?
Rather than being released into a portal system, the neurohormones from the hypothalamus are secreted directly into the PP
- Oxytocin (OT)
- Arginine vasopressin (AVP)
What are the pancreatic hormones?
Four major peptide hormone products are secreted from the pancreas:
- Insulin
- Glucagon
- Somatostatin
- Pancreatic polypeptide
What are the Gastrointestinal hormones?
- secretin
- Cholecystokinin (CCK)
- Ghrelin
How do the placental hormones work?
- The placenta is a temporary endocrine organ thaht develops in the uterus during pregnancy
- It helps to maintain nutritional, repiratory, and excretory functions for the fetus
- it also produces several peptide and steroid hormones;
- human chorionic gonadotropin (hCG)
- Progesterone (P)
How does the adrenal medulla work?
- releases epinephrine, norepinephrine and dopamine in response to neural signals into general circulation
- these are monoamines
- stimuli that evoke release of catecholamines: stress, exercise, emotionality, low temps
- influence circulatory and metabolic systems to prepare the body for action
How do the hormones in the adrenal cortex work?
- Zona glomerulosa: outer most zone, releases aldosterone
- Zona fasciculata: middle zone, releases glucocorticoids (steroid hormones)
- Zona reticularis: innermost area, releases low levels of some steroid hormones
What is the purpose of the gonads?
- production of gametes
- production of steroid hormones (required for gamete production, development of secondary sex characteristics, behaviors that bring gametes together
(male = testes, female = ovaries)
What are sertoli cells?
(in testes) house and nourish developing sperm; produce the peptide hormone inhibin
What are leydig cells?
(in testes) primary hormone-producing cells; produce steroid hormones (androgens) in response to gonadotropins from anterior pituitary
What are androgens?
a class of hormones that have many physiological and behavioral effects
- testosterone
–Dihydrotestosterone (DHT; converted from testosterone in the presence of the enzyme 5-alpha-reductase)
–Androtestosterone
How do the ovaries work?
produce gametes and steroid hormones (like the testes) (in the thecal cells) in response to gonadotropins from anterior pituitary
- Estrogens and progesterone
- they exhibit cyclic changes in function, whereas the testes do not
How do estrogens function in the ovaries?
converted directly from testosterone via the enzyme aromatase (in the ovary)
- most common form is estradiol
What is progesterone?
produced by the corpus luteum and is important for the maintenance of pregnancy (if it occurs)
Are there such things as female hormones?
-no!
- both males and females produce estrogens and androgens, albeit in different amounts
How do hormones work in the pineal gland?
-individual pineal cells each function as secretory structures
-produce serotonin and melatonin (indoleamines)
- primary functions has shifted from photoreception to neurorecretion
What are the thyroid hormones?
-Thyroxine (T4), and triiodothyronine (T3)
- derived from a single amino acid, tyrosine
- released in response to TSH from the anterior pituitary
- Affect metabolism, alter growth and differentiation, influence reproduction
How are hormones regulated?
- by physiological by-products generated in response to their actions
- by the stimulatory or inhibitory effects of other hormones
What is negative feedback?
shuts off system/production once the hormone binds to a receptor due to the “product” of behavior
What is positive feedback?
The hormone illicits a behavior that then signals to the hormone to continue to its work
