2 week 7 Flashcards
diff bw direct and indirect cell-to-cell communication?
direct: physical link via connexons
indirect: use chemical messengers
whats a neurohormone?
chemicals released by neurons into the blood
diff bw primary and secondary endocrine organs?
primary: main function = hormone secretion
secondary: main function = something else
what are the 6 secondary endocrine organs?
heart
stomach
liver
kidney
small intestine
skin
what is hormone secretion regulated by? (5)
neurotransmitters
other hormones
metabolites
ions
hormonal feedback
diff bw hydrophilic and hydrophobic hormones?
hydrophilic (“lipophobic”)
- water/plasma soluble
- NOT lipid soluble, cannot cross plasma membrane
- examples: peptide hormones, protein hormones, catecholamines
hydrophobic (“lipophilic”)
- NOT water/plasma soluble
- lipid soluble, readily cross plasma membrane
- examples: steroid and thyroid hormones
how are hydrophilic and hydrophobic hormones synthesized, released, and transported in blood?
hydrophilic vs hydrophobic
- synthesized: in advance/stored vs on demand
- released: exocytosis vs diffusion
- transported: dissolve vs bind to carrier proteins
describe intracellular receptors (4)
- cytoplasmic/cytosolic or nuclear
- bind hydrophobic hormones
- directly alter gene transcription
- slow responses
describe membrane-bound receptors (4)
- g-protein linked receptors
- ligand-gated ion channels or alter enzyme activity
- bind hydrophilic hormones
- rapid responses
describe the steps of intracellular receptors binding to hormones (5)
- if receptor located in nucleus, hormone diffuses into nucleus and binds (hormone-receptor complex). if receptor located in cytosol, forms hormone-receptor complex that then enters the nucleus.
- in nucleus, hormone-receptor complex binds to hormone response element (HRE), located at the beginning of a specific gene.
- activates or deactivates gene, ultimately increases or decreases synthesis of mRNA.
- mRNA moves into the cytosol.
- mRNA translated by ribosomes to yield proteins.
describe the steps of membrane-bound receptors binding to hormones (6)
- 1st messenger binds to receptor, activating g-protein.
- g-protein releases alpha subunit, which binds to and activates enzyme adenylate cyclase.
- adenylate cyclase converts ATP to cAMP (the 2nd messenger).
- cAMP binds to and activates PKA.
- PKA phosphorylates certain proteins in cell.
- change in cell occurs.
what is amplification?
- single activated receptor can activate several g-proteins, each of which can activate an adenylate cyclase molecule.
- ex the action of one first messenger can lead to the phosphorylation of 2,500,000 proteins.
T or F: hormones carry out a target effect in a cell.
false! hormones simply relay information to cells through receptors.
T or F: cells can have receptors for more than one hormone.
true!
how does the posterior pituitary work?
neurosecretory cells project into posterior pituitary which release hormones into bloodstream
ADH/vasopressin
- secreted by paraventricular nucleus
- primary function = increases water reabsorption in the kidneys
- increases permeability of kidney cells to increase reabsorption, resulting in
low urine output
in terms of regulation of ADH release, what detects changes in a) osmolarity? b) blood volume and pressure?
a) osmoreceptors in hypothalamus
b) baroreceptors in walls of atria in heart + aortic/carotid arteries
T or F: alcohol promotes ADH
false! inhibits
oxytocin
- secreted by posterior pituitary
- stimulates uterine muscle contraction during labour + ejection of milk after parturition
how does the anterior pituitary work?
- neurosecretory cells release tropic hormones into capillary bed at the median eminence.
- travel to pituitary gland via portal vein, from which they enter a second capillary bed.
- stimulate or inhibit release of hormone.
what are tropic hormones?
hormones that regulate the secretion of other hormones
diff bw short and long loop negative feedback of hormone release regulation?
short loop: inhibition of hypothalamic hormone 1 by the anterior pituitary hormone 2.
long loop: hormone 3 feeds back to the hypothalamus to inhibit secretion of hormone 1, thereby limiting its own + hormone 2’s secretion.
what are the two growth spurts of life?
- post-natal growth spurt (ages 0-2)
- pubertal growth spurt (ages 12-16)
what are insulin-like growth factors (IGFs)?
peptides which act as chemical messengers that bear some structural resemblance to insulin.
T or F: growth hormone (GH) is released in pulses, more during the day.
false! night
what are the two ways GH and IGFs promote linear growth?
- increase proliferation (hypertrophy)
- increase protein synthesis (hyperplasia)
what is the epiphyseal plate?
site of bone lengthening, composed of cartilage.
what does red marrow produce? yellow marrow?
red marrow = red and white blood cells
yellow marrow = adipocytes
what is epiphyseal plate closure effected by?
circulating sex hormones
define:
a) osteoblast
b) osteoclast
c) chondrocyte
d) calcification
a) bone makers that deposit osteoid
b) bone breakers that break bone cells down via resorption
c) divide, produce cartilage, then degenerate
d) deposition of calcium phosphate crystals onto osteoid
how does bone growth occur? (5)
- under influence of GH and IGF, chondrocytes divide and enlarge, producing cartilage in epiphyseal plate.
- increased cartilage in epiphyseal plate elongates the bone.
- chondrocytes degenerate and osteoblasts move in.
- osteoblasts convert cartilage to bone, which becomes calcified.
- epiphyseal plate closes in late adolescence.
what is happening physiologically in gigantism and acromegaly?
- gigantism: more GH before plate fuses = long bones.
- acromegaly: excess of GH after puberty = proliferation of features despite not growing anymore.
which has longer axons: hypothalamic neuroendocrine cells regulating anterior pituitary function or those involved in posterior pituitary function?
posterior pituitary function
