Fundamentals of Anatomy & Physiology: Chapter 18 Flashcards

adjacent cells coordinate cellular activities by exchanging ions and molecules across gap junctions

1. coordinate ciliary movement among epithelial cells, 2. coordinate the contractions of cardiac muscle cells, and 3. facilitate the propagation of action potentials from one neuron to the next at electrical synapses.

the use of chemical messengers to transfer information from cell to cell with a single tissue.

chemical messengers that are released in one tissue & transported in the bloodstream to alter the activities of specific cells in other tissues.

a substance with effects outside its tissue of origin is called a hormone if its chemical structure is known, and a factor if that structure remains to be determined.

specific cells that have receptors needed to bind and "read" the hormonal message when it arrives

the activity of hormones in coordination cellular activities in tissues in distant portions of the body.

• stimulate the synthesis of an enzyme or a structural protein not already present in the cytoplasm by activating appropriate genes in the cell nucleus
• increase or decrease the rate of synthesis of a particular enzyme or other protein by changing the rate of transcription or translation
• turn an existing enzyme or membrane channel "on" or "off" by changing its shape or structure.

• electrical activity in the presynaptic neuron is converted into the release of a chemical called a neurotransmitter that binds to receptors located in the plasma membrane of the postsynaptic cell
• can form between two neurons, a neuron & muscle cell (neuromuscular junction), & a neuron & gland cell (neuroglandular junction)

includes all the endocrine cells & tissues of the body that produce hormones of paracrine factors with effects beyond their tissues of origin

• both systems rely on the release of chemicals that bind to specific receptors on their target cells
• the two systems share many chemical messengers. norepinephrine & epinephrine are called hormones when released into the bloodstream, but neurotransmitters when released across synapses
• both systems are regulated mainly by negative feedback control mechanisms
• the two systems share a common goal: to preserve homeostasis by coordinating & regulating the activities of other cells, tissues, organs & systems

glandular secretory cells that release their secretions into the extracellular fluid

secrete their products onto epithelial surfaces, generally by way of ducts.

1. amino acid derivatives
2. peptide hormones
3. lipid derivatives

relatively small molecules that are structurally related to amino acids, the building blocks of proteins

The primary hormone made from tryptophan is ______, produced by the pineal gland.

1. thyroid hormones, produced by the thyroid gland
2. the compounds epinephrine (E), norepinephrine (NE), & dopamine, which are sometimes called catecholamines

1. eicosanoids
2. steroid hormones

• signaling molecules
• Include: leukotrienes, prostaglandins, thromboxanes, & prostacyclins

1. it diffuses out of the bloodstream & binds to receptors on target cells
2. it is absorbed & broken down by cells of the liver or kidneys
3. it is broken down by enzymes in the blood or interstitial fluids

(like a neurotransmitter receptor) -is a protein molecule to which a particular molecule binds strongly

on the plasma membrane or inside the cell

a hormone that binds to a receptor on the plasma membrane surface

an intermediary molecule that appears due to a hormone-receptor interaction

1. cyclic AMP (cAMP), a derivative of ATP
2. cyclic GMP (cGMP), a derivative of GTP, another high-energy compound
3. calcium ions (Ca²⁺), focuses on cAMP & Ca²⁺

magnifies the effect of a hormone on the target cells

the production of a linked sequence enzymatic reactions

• a process in which the presence of a hormone triggers a decrease in the number of hormone receptors
• cells become less sensitive to high levels of a particular hormone

• process in which the absence of a hormone triggers an increase in the number of hormone receptors
• cells become more sensitive to low levels of a particular hormone

The link between the first messenger & the second messenger generally involves a _____?

When is a G protein activated?

an enzyme that attaches a high-energy phosphate group to another molecule in a process called phosphorylation.

inactivates cyclic AMP by converting it to AMP (adenosine monophosphate)

a process that opens the c channels & permits extracellular Ca²⁺ to enter the cell

• an intracellular protein
• can activate specific cytoplasmic enzymes
• calmodulin activation is also involved in the responses to oxytocin & to several regulatory hormones secreted by the hypothalamus

the combination of DAG & intracellular calcium ions activates a membrane protein called _______.

stimulates the production of enzymes & structural proteins in skeletal muscle fibers, causing muscle size & strength to increase

• are the functional counterparts of neutral reflexes
• endocrine reflexes can be triggered by:
  1. humoral stimuli (changes in the composition of the extracellular fluid)
  2. hormonal stimuli (the arrival or removal of a specific hormone)
  3. neural stimuli (the arrival of neurotransmitters at neuroglandular junctions)

• controlled by negative feedback
• a simple endocrine reflex involves only one hormone
  • control hormone secretion by the heart, pancreas, parathyroid glands, & digestive tract
• more complex endocrine reflexes involve one or more intermediary steps & two or more hormones

1. The hypothalamus itself acts as an endocrine organ. Hypothalamic neurons synthesize hormones & transport them along axons to the posterior lobe of the pituitary gland, where they are released into the circulation.
2. The hypothalamus secretes

special hormones that control endocrine cells in the pituitary gland

the secretory activities of endocrine cells in the anterior lobe of the pituitary gland

substance secreted by endocrine tissues into the blood that acts on the target tissue to produce a specific response

the use of chemical messengers to transfer information from cell to cell within a single tissue

1. direct communication
2. paracrine communication
3. endocrine communication
4. synaptic communication

(E) epinepherine, & (NE) norepinephrine

include both neural & endocrine components because the adrenal medullae secrete both E & NE in response to action potentials rather than to circulating hormones

complex information by varying the frequency & pattern of action potentials in a sensory neuron

a hormone that stimulates glucose uptake & utilization (when blood glucose levels climb, the pancreas increases its secretion of insulin)

several hypothalamic & pituitary hormones are released in sudden bursts

changes in the frequency of pulses & in the amount secreted in each pulse

• small, oval gland lies nestled within the sella turcica
• is inferior to the hypothalamus
• connected by slender, funnel-shaped structure called the infundibulum
• held in position by the sellar diaphragm

a depression in the sphenoid bone

• the base lies between the optic chiasm & the mammillary bodies
• cradled by the sella turcica

locks the pituitary gland in position & isolates it from the cranial cavity

1. the pars distalis- the largest & most anterior portion of the pituitary gland
2. an extension called the pars tuberalis- which wraps around the adjacent portion of the infundibulum
3. the slender pars intermedia- a narrow band bordering the posterior lobe

a swelling near the attachment of the infundibulum

allow relatively large molecules to enter or leave the bloodstream

blood vessels that link two capillary networks

stimulates the synthesis & secretion of one or more hormones at the anterior lobe

prevents the synthesis & secretion of hormones from the anterior lobe

• also known as thyrotropin
• targets the thyroid gland & triggers the release of thyroid hormones

• also known as corticotropin
• stimulates the release of steroid hormones by the adrenal cortex
• specifically targets cells that produce glucocorticoids
• ACTH release occurs under the stimulation of CRH

the outer portion of the adrenal gland

hormones that affect glucose metabolism

• from the hypothalamus
• as glucocorticoid levels increase, the rates of CRH release & ACTH release decline

regulate the activities of the gonads

• from the hypothalamus
• stimulates production of gonadotropins

• an abnormally low production of gonadotropins
• children: do not mature sexually
• adults: cannot produce functional sperm (males) or oocytes (females)

1. follicle-stimulating hormone
2. luteinizing hormone

• also known as follitropin
• promotes follicle development in females
• in combination with luteinizing hormone, stimulates the secretion of estrogens by ovarian cells
• estradiol is the most important estrogen
• in males: FSH stimulates nurse cells

specialized cells in the seminiferous tubules where sperm differentiate

inhibin

a peptide hormone released by cells in the testes & ovaries

• also known as lutropin
• induces ovulation
• promotes ovarian secretion of estrogens & progesterone

the production of reproductive cells in females

prepares the body for possible pregnancy

stimulates the production of sex hormones by the interstitial cells of the testes

• male sex hormones
• most important is testosterone

• estrogens
• progesterone
• androgens

inhibit...

• works with other hormones to stimulate mammary gland development
• stimulates milk production by the mammary glands
• in males: PRL helps regulate androgen production by making interstitial cells more sensitive to LH

also known as dopamine

• secreted by the hypothalamus
• circulating PRL stimulates PIH release & inhibits the secretion of PRF

• prolactin
• estrogens
• progesterone
• glucocorticoids
• pancreatic hormones
• hormones produced by the placenta

milk ejection

• somatotropin
• stimulates cell growth & replication by acceleration the rate of protein synthesis

cartilage cells

• skeletal muscle cells
• chondrocytes (cartilage cells)

1. primary mechanism- indirect
2. direct

• also known as insulin-like growth factors (IGFs)
• liver cells repspond to GH by synthesizing & releasing...
• stimulate tissue growth by binding to receptors on a variety of plasma membranes

• skeletal muscle fibers
• cartilage cells
• other target cells

GH, acting through the somatomedins

as circulating fatty acid levels rise, many tissues stop breaking down glucose to generate ATP & instead start breaking down fatty acids

the elevation of blood glucose levels by GH because, diabetes mellitus (endocrine disorder) is characterized by abnormal high blood glucose concentrations

• also known as somatocrinin
• production of GH is regulated by...
• somatomedins inhibits _______

• also known as somatostatin
• production of GH is regulated by...
• somatomedins stimulate ______

• also known as melanotropin
• the pars intermedia may secrete two forms
• stimulates the melanocytes of the skin (increasing their production of melanin)
• dopamine inhibits the release of ______

a brown, black, or yellow-brown pigment

1. during fetal development
2. in very young children
3. in pregnant women
4. in the course of some diseases

• also called the neurohypophysis
• contains the axons of hypothalamic neurons

1. antidiuretic hormone (ADH)
2. oxytocin (OXT)

• also known as vasopressin (VP)
• is released in response to a variety of stimuli (a rise in the solute concentration in the blood or a fall in blood volume or blood pressure)

• a rise in the solute concentration stimulates specialized neurons in the hypothalamus
• they respond to a change in the osmotic concentration of body fluids