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Biology 102 > Leture 13 - Endocrine System > Flashcards

Leture 13 - Endocrine System Flashcards

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1
Q

Endocrine Cells

A
  • cells that produce and release hormones
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2
Q

Endocrine Gland

A

Group of endocrine cells forming a secretory organ

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3
Q

Hormones

A

chemical signal released by endocrine cells that influences the activity of other cells at a distance

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4
Q

Long distance signaling

A
  • travel through blood stream
  • blind to receptors on or in distant target cells
  • target cell must have the proper receptor to bind the hormone
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5
Q

Timing of endocrine system:

Coordination fo endocrine system:

A
  • longer to turn on and off than more direct signaling (ie neurotransmitters)
  • can coordinate many different responses
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6
Q

3 chemical groups of hormones

A
  1. Peptide or protein hormones
  2. steroid hormones
  3. Amine hormones
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7
Q

Peptide/protein hormones

A
  • majority of hormones
  • ex: insulin
  • water soluble
  • transported through blood without carriers
  • receptors on the cell surface
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8
Q

steroid hormones

A
  • ex: testosterone
  • synthesized from cholesterol
  • lipid soluble
  • easily pass through cell membranes
  • bound to carrier molecules in blood
  • receptors are mostly intracellular (in cytoplasm or nucleus)
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9
Q

Amine hormones

A
  • ex: thyroxine
  • synthesized from the amino acid tyrosine
  • can be water soluble OR lipid soluble
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10
Q

Cell’s response to a signal depends on:

A

which receptors it possesses

  • for that particular signal
  • different types of cells have different types of receptors that bind the ligand –> different responses
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11
Q

Receptors and intracellular pathways

A
  • intracelllula rpathways activated by a particular receptor differ
  • same receptor that binds ligand, but different responses
  • due to cell’s predetermined state

*which “responders” are called to scene of activation

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12
Q

Same Hormone, different responses in different cells…

Epinephrine

A

Ex: epinephrine

  • one hormone can bind to receptors in many different tissues
  • initiates fight or flight response
  • heart pumps faster and stronger
  • blood vessels to skin and gut constrict, shunting blood to muscles
  • liver breaks down glycogen to supply glucose to blood
  • fat cells release fatty acids to blood
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13
Q

Receptor Specificity of Cells

A
  • No receptor at all = no response

- different receptors might bind the same hormone = different pathways activated in those cells = different responses

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14
Q

Control of hormone release

A
  1. brain responds to environmental conditions
  2. provide a signal to the endocrine cells to release hormones
  3. hormones released into blood stream
  4. bind to receptors on target cell
  5. physiological response
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15
Q

Step 1: Brain communicated with endocrine system

A
  1. Hypothalamus: integrates infotmation from body and environment and communicates this to endocrine system
  2. sends it to the “control center”/pituitary gland of endocrine system
  3. pituitary then regulates other glands of body
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16
Q

Pituitary

A

“mouthpiee through which the brain speaks to the body”

2 lobes:

  • anterior
  • posterior
  • Hypothalamus speaks to pituitary
  • regulates each lobe differently
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17
Q

Posterior Pituitary

A
  • NO secretory cells
  • just capillaries
  • hypothalamus releases neurohormones into capillaries in posterior pituitary
  • hypothalamus axons extend down to posterior pituitary
  • release hormones that go into blood stream
  • from there, continue circulating through body
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18
Q

Two hormones released by hypothalamus

A
  • oxytocin
    (childbirth, lactation, promotes bonding)
  • ADH
    ( increases water conserved by kidneys, inresponse to blood volume and salt concentration)
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19
Q

Anterior pituitary

A
  • an actual gland that synthesizes and releases itw own hormones
  • neurones from the hypothalamus do not project all the way to pituitary
  • release hormones onto blood vessels that run to anterior pituitary
  • releasing hormones and releasing inhibiting hormones
  • these hormones cause pituitary cells to secrete or stop secreting hormones into blood stream
20
Q

Type of hormones released by anterior pituitary

A

Tropic hormones

  • control activities of other endocrine glands
  • tropic hormones act on thyroid, adrenal gland, testes and ovaries
  • ex: corticotropin –> signal the adrenal gland to release cortisol
21
Q

The Stress Response

A
  1. Hypothalamus:
    - releases Corticotropin releasing hormone (CRH)
  2. Ant Pituitary
    - CRH causes pituitary to release corticotropin into blood stream
  3. Adrenal Glan
    - Corticotropin causes Adrenal gland to release cortisol
  4. Cortisol
    - mobilizes energy reserves
    - supresses immune system
    - effect neuron activity in short- and long-term
22
Q

Negative feedback loop

A
  • endocrine cells in pituitary are also under negative feedback control by hormones f the glands that they stimulate
  • tropic hormones released from pituitary stimulates release of a hormone from another endocrine gland
  • this second hormone inhibits release of more tropic hormone from the pituitary

Ex: stimulates adrenal gland to release cortisol. Cortisol inhibits further release of corticotropin and corticotropin release hormone

23
Q

Thyroid gland

A

Hormones regulate its two main functions:

  1. cell metabolism (thyroxine)
  2. regulation of blood calcium levels (calcitonin, parathyroid hormone - PTH, calcitrol)
24
Q

Thyroxine synthesis

A
  • release stimulates by thyroid stimulating hormone (TSH) produced by anterior pituitary
  • thyroxine is modified by iodine atoms
  • initially four iodine atoms are added onto the hormone
  • Thyroid releases mostly T4 into bloodstream
  • but thyroxine is active when only 3 iodines are on it, T3
  • T4 is converted to T3 by an enzyme in the target cells
  • therefore each target cell can set its own sensitivity to thyroid hormones by controlling the conversion step
25
Q

Role of Thyroxine

A

Regulates cell metabolism:

Elevates metabolic rates of most cells and tissues

  • most cells int he body have thyroxine receptor
  • promotes amino acid uptake and protein synthesis
  • very important during development

hypothalamus regulates release in response to temperature, day length, etc
- ex: exposure to cold leads to increased level of thyroxine

26
Q

Hyperthyroidism

A
  • excess production of thyroxine

- high metabolic rates, jumpy/nervous, feel hot

27
Q

Hypothyroidism

A
  • deficiency of functional thyroxine
  • low metabolism, intolerance of cold, physical and mental sluggishness
  • ex: iodine deficiency
  • can both lead to goiter
28
Q

Thyroid gland and blood calcium concentrations

A

Regulates blood calcium concentrations:

  • 99% of body calcium is stored in bones
  • very important for the amount circulating in the blood to be tightly regulated
  • body has multiple mechanisms for changing blood calcium levels:
    1. deposition of absorption levels
    2. excretion or retention of calcum (by kidneys)
    3. absorbption of calcium from digestive tract
29
Q

3 hormones that regulate blood calcium levels

A
  1. calcitonin
  2. parathyroid hormone (PTH)
  3. Calcitrol
30
Q

Calcitonin

A

Blood calcium too high:

  • reduces blood calcium
  • its deposited into bone
  • more important in young individuals that are actively growing
31
Q

Parathyroid hormone

A

Blood calcium levels too low:

  • increase in blood calcium
  • breakdown of bones releases calcium
  • most important hormone in regulation of blood calcium levels
  • activates synthesis of calcitrol
32
Q

calcitrol

A

Blood calcium levels too low:

  • synthesized from vitamin D
  • stimulates kidneys and git to reabsorb calcium back into the blood rather than excrete it
33
Q

Pancreas

A

Produces insulin and glucagon

34
Q

Insulin

A
  • released in response to eating a meal (high blood glucose)
  • stimulates insertion of glucose transporters into cell membrane
  • glucose can enter cell and be used as fuel
  • also promotes storage of glucose as glycogen in liver
  1. glucose as fuel
  2. storage of glucose as glycogen
35
Q

Glucagon

A
  • released in response to low blood glucose levels

- stimulates the lover to break down the stored glycogen and release glucose

36
Q

Diabetes Mellitus

A
  • lack on insulin (type i)
  • lack of insulin responsiveness in target tissues (Type ii)
  • glucose entry into cells is impaired
  • high blood sugar
  • cells suffer from a lack of metabolic fuel
37
Q

Adrenal Gland

A

Medulla and cortex

38
Q

Adrenal medulla

A
  • inner core
  • epinephrine
  • norepinephrine
  • acute release in response to stresful situations
  • direct innervation from autonomic nervous system
  • fight or flight response
39
Q

Adrenal cortex

A
  • surrounds medulla
  • produces steroid hormones
  • ex: cortisol
  • release controlled by corticotropin from anterior pituitary
  • slower to turn on, longer lasting stress response
  • mobilizes energy reserves
  • suppress immune system
40
Q

Cortisol and chronic stress

A
  • cortisol release normally turned off by negative feedback
  • repeated activation of cortisol system has been shown to lead a decreased inability to terminate the stress response
  • old rats also shown to be able to turn on stress response as well as young ones, but unable to turn it off as effectively
  • digestive system problems, cardiovascur problems, strokes, impaired immune system
  • mice given daily injections of cortisol show signs of neuron death
41
Q

Gonads and their hormones

A

Male: testes
- produce androgens –> testosterone

female: ovaries
produce estrogen, progesterone

42
Q

Pineal gland

A
  • produces melatonin
  • melatonin released int he dark
  • marks length of the night
  • exposure to light inhibits its production
  • involved in biological rhythms
43
Q

Photoperiodicity

A
  • changes in day length cause physiological changes

Ex: siberian hamsters

  • white in winter and do not reproduce
  • brown in summer and breed
44
Q

How does the body change blood calcium levels?

A
  1. deposition of absorption levels
  2. excretion or retention of calcum (by kidneys)
  3. absorption of calcium from digestive tract
45
Q

Importance of sex hormones

A

Development:

  • Y chromosome –> gonads produce androgens in 7th week of development
  • androgens –> undifferentiated reproductive system into a male

Puberty:

  • production of sex steroids increases dramatically at the beginning of uberty
  • hypothalamus stimulates pituitary to release gonadotropins
  • gonadotropins stimulate release of sex hormones from gonads
  • initiate development of secondary sex characteristics

Biology 102 (15 decks)

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