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Anatomy & Physiology 208 > Endocrine System Part I > Flashcards

Endocrine System Part I Flashcards

1
Q

endocrinology

A

the study of hormones and the endocrine organs

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2
Q

speed of endocrine system

A

responses are slower but longer lasting than those of the nervous system

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3
Q

endocrine system controls and integrates

A
  • reproduction
  • growth/development
  • maintenance of electrolyte, water, and nutrient balance
  • regulation of cellular metabolism and energy balance
  • mobilization of body’s defenses
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4
Q

exocrine glands

A
  • produce nonhormonal substances (sweat, saliva)
  • have ducts to carrry secretions to membrane surfaces
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5
Q

endocrine glands

A
  • produce hormones
  • lack ducts
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6
Q

hypothalamus

A

neuroendocrine organ
*pancreas, gonads, and placenta have exocrine and endocrine functions

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7
Q

all endocrine glands

A
  • pituitary, thyroid, parathyroid, adrenal, pineal
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8
Q

other tissues and organs that produce hormones

A

adipose cells, thymus, cells in walls of small intestine, stomach, kidneys, heart

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9
Q

paracrines

A

locally acting chemicals that affect cells other than those that secrete them
- local, not considered part of the endocrine system

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9
Q

hormones

A

long-distance chemical signals; travel through blood or lymph

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10
Q

autocrines

A

chemicals that exert effects on the same cells that secrete them
- local, not considered part of the endocrine system

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11
Q

steroids

A

synthezised from cholesterol; gonadal and adrenocortical hormones

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12
Q

amino acid based hormones

A

amino acid derivatives, peptides, and proteins

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13
Q

how endocrine system works

A

hormones circulate systemically, but only cells with receptors for a specific hormone will be affected

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14
Q

target cells

A

tissues with receptors for a specific hormone
- hormones alter target cell activity

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15
Q

upon arrival at target cells, hormones may be able to:

A
  • alter plasma membrane permeability and/or membrane potential by opening/closing ion channels
  • stimulate synthesis of enzymes or other proteins
  • activate/deactivate enzymes
  • induce secretory activity
  • stimulate mitosis
16
Q

water soluble hormones

A

all amino acid based hormones except thyroid hormone
- cannot directly enter a cell
- act on plasma membrane receptors
- typically, receptors are coupled to 1+ intracellular second messengers via regulatory molecules called g proteins

17
Q

except for thyroid hormone, amino acid based hormones exert effects through second-messenger systems:

A
  • cyclic AMP
  • PIP 2-calcium
17
Q

lipid soluble hormones

A

steroid and thyroid hormones
- can directly enter a cell
- act on intracellular receptors that directly activate genes

18
Q

cAMP is degraded by

A

phosphodiesterase

18
Q

cAMP signaling mechanism

A
  1. Hormone (First Messenger) binds to receptor
  2. Receptor activates a G Protein
  3. G Protein activates or inhibits amplifier enzyme adenylate cyclase
  4. Adenylate cyclase converts ATP to cAMP (Second Messenger)
  5. cAMP activates proteins kinases that phosphorylate other proteins and generate responses within the cell
19
Q

molecular relay race analogy

A

hormone (1st messenger) > receptor > G protein > enzyme > 2nd messenger

20
Q

pip 2 calcium signaling mechanism

A

hormone activated g protein activates phospholipase c - an effector enzyme

21
Q

activated phospholipase c splits membrane protein, pip 2, into 2nd messengers:

A
  • dialglycerol (DAG); activates protein kinases and triggers responses within target cells
  • inositol triphosphate (IP3) causes Ca2+ to be released from intracellular storage sites
22
Q

freed ca2+ ions act as another second messenger

A
  • ca2+ either alters enzyme and channel activity or binds to a regulatory protein called calmodulin
  • once ca2+ binds to calmodulin, it activates enzymes that amplify the cellular response
23
Q

intracellular receptors and direct gene activation

A
  • Lipid-soluble steroid hormones and thyroid hormone can diffuse into target cells and bind with their intracellular receptors
  • Receptor-hormone complexes then enter the nucleus and bind to specific regions of the DNA
  • Binding helps to initiate transcription of DNA to produce mRNA
  • mRNA is then translated into specific proteins
  • The proteins synthesized have various functions – metabolic activities, structural purposes, or exportation from the cell
23
Q

other signaling mechanisms

A
  • cyclic guanosine monophosphate (cGMP) is a 2nd messenger for selected hormones
  • other hormones work without any second messenger system
  • ex insulin receptor is a tyrosine enzyme that autophosphorylates upon insulin’s binding; the activated tyrosine kinases provide docking sites for relay proteins that trigger cell responses
24
Q

endocrine glands are stimulated to synthesize and release hormones in response to 1 of 3 stimuli

A
  • humoral stimuli
  • neural stimuli
  • hormonal stimuli
25
Q

release of hormones

A
  • negative feedback loop
  • internal/external stimulus triggers release of hormone
  • rising hormone levels cause effects at target hormones
  • additional rise in hormone levels inhibits further release
  • hormonal levels vary within a narrow, desirable range
26
Q

humoral stimuli

A

changing blood levels of ions and nutrients directly stimulates secretion of hormones
- ex. level of ca2+ in blood > when it declines PTH is secreted

27
Q

neural stimuli

A

nerve fibers stimulate hormone release
- ex. in times of stress, fibers of the sympathetic nervous system stimulate the adrenal medulla to secrete catecholamines

28
Q

hormonal stimuli

A

hormones can stimulate other endocrine glands to release their hormones
- ex. Hypothalamic hormones stimulate the release of most anterior pituitary hormones
- Anterior pituitary hormones stimulate their targets to secrete still more hormones
- Hormones from the final target organs inhibit the release of anterior pituitary hormones – the hypothalamic-pituitary-target endocrine organ feedback loop

29
Q

nervous system modulation

A

nervous system can adjust hormone levels when needed - can modify stimulation/inhibition of different endocrine glands
- nervous sytem can override mechanical endocrine controls
- ex. under severe stress, the hypothalamus and sympathetic nervous system override insulin controls to allow blood glucose levels to rise

30
Q

target cell specificity

A

target cells must have the specific receptors to which a hormone binds
- ex. receptors for ACTH are only on certain cells of adrenal cortex but thyroxin receptors are found on nearly every cell of the body

30
Q

target cell activation 3 factors

A
  1. blood levels of the hormone
  2. relative # of receptors on/in a target cell
  3. affinity (strength) of binding between receptor and hormone
31
Q

permissiveness

A

one hormone cannot exert its effects without another hormone being present
- ex. reproductive hormones need thyroid hormone to have effect

32
Q

synergism

A

more than one hormone produces the same effects on the target cell - causes amplification
- ex. glucagon and epinephrine both cause the liver to release glucose

33
Q

antagonism

A

one or more hormones oppose the action of another hormone
- ex. insulin and glucagon

Anatomy & Physiology 208 (39 decks)

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