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Flashcards in Exam 1 Deck (76):
1

Hormone

signaling molecule (primary messenger( that reaches its target by circulating in the blood

2

Endocrine Organ

any organ that produces and secretes hormones into the blood
i.e. heart, liver, kidneys, GI tract, brain

3

Target cell

a cell whose function can be altered by the hormone
a target cell for a specific hormone will have a protein receptor molecule that binds the hormone

4

Chemical signals

molecules that alter cell function

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primary messengers

molecues that convey information between cells

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secondary messengers

intracellular molecules that mediate the action of primary messengers
i.e. cAMP, cGMP, calcium/calmodulin

7

Neurotransmitters

produced by neurons, released directly onto their target cells at the synapse
function to alter the membrane potential of the target cell

8

neuropeptides

produced by neurons, released directly onto their target cells at the synapse
act either as growth factors or as neuromodulators

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neuromodulators

primary messengers that alter a neurons response to neurotransmitters

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paracrines

signaling molecules that act within the same organ that produces them
not secreted into the blood to react with their target cells, often include growth factors

11

juxtacrines

a subset of paracrines
passed directly between neighboring cells, often through gap junctions
insulin and glucagon act as juxtacrines in the pancreas

12

autocrines

primary messenger molecules such as hormones can act on the cells that produce them (self- stimulation)

13

cytokines

signaling molecules produced by the immune system
can act locally, but also travel in the bloodstream as immune cells are often found in the blood

14

Psycho-neuro-endocrine-immunology

interactions between the nervous, endrocrine, and immune systems
constant communication between the three systems, each modifies the function of the others

15

homeostasis

maintenance of a constant internal environment
only a few physiological variables do not change their set points
pH, osmotic pressures, and ion concentrations are some examples

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variable

physiological parameter to be controlled

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set point

the optimal level of a variable

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sensors

receptors which detect and measure the level of a variable

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afferent pathways

conveys information from sensors to an integrating center

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integrating center

recieves information about a variable and other relevant variables from many different sensors
compares the level of the variable to the ideal level and activates the effectors to enact necessary changes to the variable

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efferent pathways

carry information from the integrating center to the effectors

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effectors

calls that act to change the variable
could be muscle, secretory, immune, endocrine cells, ect.

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Homeodynamics

maintenance of an ideal internal environment
the set point changes as the body's need for specific levels of a variable change

24

Homeodynamic mechanisms can:

contain all elements within a single cell
involve the entire body
incolve several organs or cell types

25

Regulation of hormones levels in blood

rate of secretion
rate of metabolism
rate of excretion
binding proteins in blood

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Factors effecting a body's need for a specific hormone level

physiological state
individual sensitivity to a hormone
simultaneous action of other chemical messengers on the same cell

27

Additive effects of hormones

two or more hormones working together is equal to the sum of their individual effects
this is usually seen when both hormones have the same action on a cell, and there is often a plateau in their actions

28

Syngergistic effects of hormones

hormones working together will be greater than the sum of their individual effects
each hormone has a different action and their combined actions multiply each other's effects

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Antagonistic effects of hormones

two hormones oppose or black each other's actions
this may occur through inhibiting the enzyme another hormone activates, causing destruction of receptors for another hormone, or binding to a receptor to block another hormone from binding

30

Biphasic effects of hormones

One hormone can produce opposite effects on the same cell at different concentrations by acting through different mechanisms
this can occur by having a receptor with high binding affinity (only needs low hormone concentrations) and one with low binding affinity (would require higher hormone concentrations to be activated)

31

Biphasic effects of hormones lead us to what major course concept?

If a little bit of a hormone is good, then a lot is a disaster

32

Hormones can modify which physiological actions:

enzyme activity
gene transcription
RNA translation
secretion of molefules
rate of mitosis
rate of cell death
cell permeability
"anything a cell can do, a hormone can modify"

33

Half life

the amount of time it takes the body to metabolize half of the circulating hormone molecules

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Importance of hormone half life:

shorter half lives allow for finer control of a variable while longer half lives allow the body to save the energy of synthesis, packaging, and secretion

35

what determines whether a hormone can cross a cell membrane?

lipid solubility

36

Lipid soluble hormones

steroid hormones
nonpolar
can cross the cell membrane and bind to intracellular receptors, and regulate gene expression

37

Polar hormones

amino acid derivatives, proteins, and glycoproteins
unable to cross the cell membrane, so must work through a secondary messenger

38

Steroid hormone action

the steroid hormone binds to a receptor within the cell
the steriod-receptor complex then binds to recognition (acceptor) sites on the DNA
this then influences the gene expression at that site
the physiological response can take several hours to weeks before it is seen

39

Hormone response elements

acceptor sites on DNA that recognize the steriod-receptor complex and allows the complex to bind the DNA

40

Dose- Response effects of steriods

some actions of steriods are only seen at specific hormone concentrations

41

Tyrosine Kinase

The receptor on the ouside of the cell is a transmembrane protein that contains tyrosine kinase
the tyrosine kinase phosphorylates proteins at the amino acid tyrosine

42

Effects of phosphorylation

activate or inhibit an enzyme
open or close a channel
activate or inhibit gene expression

43

G Protein second messenger systems

a complex of 3 g proteins: alpha, beta, and gamma are found in the cell membrane
they are able to interact with other membrane molecules to enact the physiologic effects of the hormone

44

G alpha

possesses GTPase activity
this regulates how long a hormone can act on a cell
once the G alpha splits GTP to GDP, it recombines with G beta and G gamma and stops the effects of the hormone

45

Activating step in the G protein system

G alpha binds GTP and releases G beta and gamma
G beta and G gamma cause the physiologic effects of the hormone once they are released from G alpha

46

If GTPase activity is blocked,

the hormone action is accentuated and prolonged

this occurs with cholera and some forms of cancer

47

Adenyl cyclase system

G proteins activate adenyl cyclase (ATP --> cAMP)
cAMP activates cAMP dependent kinases (Protein Kinase A)

48

Cascade effect

the effect of one molecule of hormone can be multiplied several times through the action of second messenger

49

Down regulation of hormone receptors

loss of hormone receptors leads to decreased sensitivity (responsiveness) to the hormone
this occurs in minutes and is important to prevent overstimulation of the cell

50

upregulation of hormone receptors

increased synthesis and insertion of receptors on the cell membrane
can take hours to days and leads to increased sensitivity and response to the hormone over time

51

Phosphodiesterase

an enzyme that destroys cAMP
some hormones antagonize the action of hormones that work via cAMP by activating phosphodiesterase

52

DAG

diacyl glycerol
activates DAG dependent kinases

53

DAG dependent kinases

often membrane associated, phosphorylate ion channels and other membrane associated proteins

54

IP3

inositol triphosphate
causes the release of intracellular calcium stores from the endoplasmic reticulum

55

Direct action of a molecule

the concentration of a molecule in the extracellular fluid influences the secretion of the hormone
i.e. glucose regulation of insulin secretion

56

Neural control of hormone release

neurotransmitters function as the signal to stimulate hormone release

57

endocrine control of hormone release

regulation of hormone secretion by other hormones

58

Releasing hormones

of the hypothalamus
trigger the synthesis and secretion of anterior pituitary hormones

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Inhibiting hormones

of the hypothalamus
inhibit secretion of anterior pituitary hormines

60

Trophic hormones

from the anterior pituitary
stimulate the secretion of hormones from their target organs
(i.e. corticotrophin stimulates the adrenal cortex to secrete glucocorticoids)

61

Neural functions of the Hypothalamus

sensory- cells that measure nutrient levels in blood, osmotic pressure, temp, hormone levels, ect
integrating centers- nuclei which regulate physiological functions and which regulate the secretion of hormones

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Endocrine functions of the hypothalamus

neuroendocrine cells produce hypothalamic hormones which regulate the anterior pituitary or those that are stored in and released from the posterior pituitary

63

Antidiuretic Hormone actions

aka vasopressin
opposes water loss in urine
vasoconstriction to raise blood pressure
stimulates thirst

64

Regulation of ADH secretion

osmoreceptors in the hypothalamus measure osmotic pressure of the blood, ADH is secreted when osmotic pressure rises
baroreceptors in the carotid body/aortic arch measure BP, ADH is secreted when BP is low

65

Pre-prohormones

large precursors to protein hormones
made up of the hormone along with neurophysins
made in the cell body of the hypothalamic magnocellular neurons
packaged by the golgi and move down axons by axo-plasmic flow

66

Neurophysins

part of a pre-prohormone that is cleaved off to reveal a functional hormone

67

Oxytocin actions

stimulates contraction of smooth muscle within the reproductive teacts
stimulates contractions of smooth muscle cells in the mammary glands (milk letdown)

68

Regulation of oxytocin secretion

Stimulation of sensory neurons in the mammary gland and uterine cervix and in the male reproductive tract triggers spinal sensory pathways to trigger oxytocin release
stimuli associated with breastfeeding also triggers release
stress and alcohol inhibit oxytocin release

69

Hypothalamic hypophyseal portal system

hypothalamic portal veins connect capillaries in the hypothalamus and anterior pituitary
communication can go both ways so hypothalamic hormones influence anterior pituitary function and vice versa

70

Importance of the portal system

hypothalamic hormones are small peptides that are rapidly destroyed
they reach the anterior pituitary before being destroyed in the periphery

71

Anterior pituitary hormones that act directly on peripheral target cells

prolactin
growth hormone
melanocyte stimulating hormone (aka melanotropin)

72

Hormones that stimulate the activities of other endocrine glands

TSH
ACTH
FSH
LH
Prolactin
Growth Hormone

73

CRH

corticotropic releasing hormone
stimulates ACTH and MSH release

74

TRH

Thyrotropic Releasing Hormone
stimulates the release of TSH

75

GnRH

Gonadtrophic releasing hormone
releases FSH and LH

76

Growth Hormone Releasing Hormone

stimulates the release of GH