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NE Exam 3 > Intro To Endocrine System > Flashcards

Intro To Endocrine System Flashcards

1
Q

What is autocrine signaling?

A

Cell secretes a hormone that influences that cell itself or a similar cell type in the same tissue

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2
Q

What is paracrine signaling?

A

Cell releases a hormone that influences a nearby cell of a different type (within the same tissue)

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3
Q

What is endocrine signaling?

A

Cell releases a hormone into the blood which travels to and influences the target tissue

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4
Q

What is neuroendocrine signaling?

A

Neuron releases hormone into the blood which then influences the target tissue

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5
Q

What is neurocrine signaling?

A

Direct release of hormone from neuron onto the target tissue

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6
Q

What are the classical endocrine glands?

A

Hypothalamus, anterior/posterior pituitary, thyroid, parathyroid, adrenal cortex/medulla, gonads, endocrine pancreas, placenta (transitory organ)

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7
Q

Describe protein and peptide hormones

A

Produced by protein synthesis
Most synthesized as a non-functional pre-prohormone -> pro-hormone -> functional hormone which is stored in secretory vesicle where they are released following stimulation of the endocrine gland

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8
Q

Describe steroid hormones

A

Derivates of cholesterol
Synthesized within the adrenal cortex, gonads and corpus luteum
Lipid soluble
Not stored in endocrine tissue due to being permeable through cell
Act upon intracellular receptors at their target tissues

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9
Q

Describe the amine hormones

A

Synthesized from tyrosine

Two major groups: catecholamines and thyroid hormones

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10
Q

Describe the catecholamines

A

Dopamine, NE and epinephrine
Synthesized via enzymatic conversion of tyrosine in cytosol and secretory granules
Able to act through cell membrane receptors at their target tissues

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11
Q

Describe the thyroid hormones

A

Synthesized in the thyroid gland
Stored as thyroglobulins in follicles in the gland
Able to cross cell membranes of target tissue and act through nuclear receptors

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12
Q

What is the half life and clearance rate of thyroid hormones?

A

Majoring in circulation interact with binding proteins

Increases their plasma half life and decreases metabolic clearance rates

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13
Q

What is the half life and metabolic clearance rate of protein hormones?

A

Rarely utilize binding proteins

Short plasma half life and rapid clearance rates

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14
Q

What is the plasma half life and clearance rate of steroid hormones?

A

Are towards the middle (in between steroid and protein hormones)
Those that do interact with binding proteins have longer half life and slower clearance rates

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15
Q

When hormones are bound to binding proteins they are in what state?

A

Inactive

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16
Q

When are hormones active in the circulation?

A

Must be unbound from binding protein to interact with target tissues

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17
Q

What is the neural mechanism for regulation of hormone secretion?

A

Neural input to endocrine cell which will cause an increase or decrease of hormone secretion
Ex. Sympathetic preganglionic innervation of the adrenal medulla - when stimulated causes the release of catecholamines into the circulation

18
Q

What is positive feedback?

A

Part of the pathway itself will stimulate another portion of the feedback loop in order to increase secretion of the hormone

19
Q

What is negative feedback?

A

Some portion of the pathway will inhibit further secretion of the hormone by acting on another part of the same feedback loop
Helps keep the hormone within a normal range

20
Q

What is an example of a short loop?

A

Anterior pituitary (2nd tier) hormone inhibits the hypothalamus (1st tier)

21
Q

What is an ultra short loop?

A

Hormone affects the target gland secreting the hormone itself

22
Q

What is a long loop mechanism?

A

Hormone released from a peripheral endocrine gland inhibits the anterior pituitary and hypothalamus

23
Q

Describe the connection between the hypothalamus and posterior pituitary

A

Pareventricular and supraoptic nuclei are located in the hypothalamus —> send axons down the neurohypophysis (posterior pituitary) and release oxytocin and vasopressin —> oxytocin and vasopressin are stored in secretory vesicles in the posterior pituitary and will be released into the circulation upon stimulation

24
Q

What is the function of oxytocin?

A

Affects on behavior, uterine contractions and milk let down

25
Q

What is the function of vasopressin?

A

Water reabsorption back into the circulation in the kidneys and regulates vascular resistance and arterial BP

26
Q

Describe the connection between the hypothalamus and the anterior pituitary

A

Secretions of the releasing hormones from the hypothalamus will be released into the primary plexus of the hypophyseal portal system/circulation
Hypophyseal veins will carry the secretions into the anterior pituitary
Cells in the anterior pituitary will respond to their respective hormone and then secrete it into the circulation upon stimulation

27
Q

What is the the hypothalamic thyroid axis?

A

Thyrotropin releasing hormone induces secretion of TSH from anterior pituitary which acts on the thyroid gland to cause production and secretion of thyroid hormones

28
Q

What is the hypothalamic adrenal axis?

A

Corticotropin releasing hormone from hypothalamus causes release of ACTH from the anterior pituitary which acts on the adrenal glands to induce production and secretion of cortisol

29
Q

What is the hypothalamic gonad axis?

A

Gonadotropin releasing hormone from hypothalamus —> release of LH and FSH from anterior pituitary -> act upon ovaries and testes to regulate production of testosterone, progesterone, estrogen; necessary for sperm and oocyte maturation and ovulation

30
Q

What is the hypothalamic growth hormone axis?

A

GH releasing hormone produced in hypothalamus -> anterior pituitary secretes GH -> stimulates protein synthesis and has a positive affect on growth for many tissues (either by direct action on target tissues or indirectly through stimulating IGF in the liver)

31
Q

What is the role of dopamine (prolactin inhibiting factor)?

A

Inhibits the release of prolactin from the anterior pituitary (even though it is continuously being produced)
Decreased dopamine concentrations are required for prolactin release

32
Q

What is the role of somatostatin (GH inhibiting hormone)?

A

Released from hypothalamus and inhibits release of GH

33
Q

Describe the regulation of the hypothalamus

A

Occurs at the level of neural input which helps modulate hormone secretion from the hypothalamus
Major inputs include SCN which imposes a circadian rhythm upon the secretion of releasing hormones
Pineal gland releases melatonin which can feedback to the SCN about day/night cycles
Physiological stresses and changes in perimeters can influence the release of hormones from hypothalamus

34
Q

Describe the regulation of hormone receptors

A

Receptors confer specificity to the hormone actions (hormone receptor complex)
Responsiveness of target tissue is expressed in dose response relationship
Responsiveness can be changed in two ways (changing the # of receptors through upregulation or downregulation or changing the affinity of the receptors for the hormones)

35
Q

How can the number of receptors be altered?

A

Through receptor upregulation by increasing number of new receptors through synthesis of new receptors or decreasing degradation of existing ones
Or by downregulation by reducing number of receptors either through limitation of synthesis of new receptors or increasing degradation of existing ones

36
Q

Describe the adenylyl cyclase mechanism

A

1st messenger hormones: ACTH, LH, FSH, TSH and glucagon which binds to Gs receptor
Primary effector: adenylyl cyclase (converts ATP -> cAMP)
2nd messenger: cAMP -> AMP
Second effector: protein kinase A (PKA) which phosphorylates proteins to cause the physiologic action of the hormone

37
Q

What is the phospholipase C mechanism?

A

1st messenger hormones: GnRH, TRH, oxytocin binding to Gq receptor
Primary effector: PLC
2nd messenger: IP3/DAG/Ca2+
Secondary effector: PKC (causes physiologic actions) or calmodulin

38
Q

Describe the cell signaling mechanism steroid hormone use

A

Pass through target cell membrane and interact with receptors within cytosol or nucleus
Receptor-hormone complex will bind to DNA sequence that activate or repress target gene transcription and translation

39
Q

What is the guanylyl cyclase mechanism?

A

Activation converts GTP to cGMP

cGMP activates cGMP kinase in response to ANP and results in relaxation of vascular smooth muscle (due to NO signaling)

40
Q

Describe receptor tyrosine kinases

A

Intrinsic tyrosine kinase activity

When activated tyrosine kinase phosphorylates downstream proteins

41
Q

Describe tyrosine kinase associated receptors

A

Associate non-covalently to proteins that have kinase activity
When activated kinase phosphorylates downstream proteins

NE Exam 3 (16 decks)

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