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A&P - Study Sets > Chapter 16 > Flashcards

Chapter 16 Flashcards

1
Q

Endocrine system acts with …

A

nervous system to coordinate and integrate activity of body cells

  • Influences metabolic activities via hormones transported in blood
  • Responses slower but longer lasting than nervous system responses
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2
Q

Endocrinology:

A

study of hormones and endocrine organs

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3
Q

Nervous System

A
  • initiates responses rapidly
  • short-duration responses
  • acts via action potentials and neurotransmitters
  • acts at specific locations determined by axon pathways
  • neurotransmitters act over very short distances
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4
Q

Endocrine System

A
  • initiates responses slowly
  • long-duration responses
  • acts via hormones released into the blood
  • acts at diffuse locations - targets can be anywhere blood reaches
  • hormones act over long distances
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5
Q

Endocrine system controls and integrates:

A
  • Reproduction
  • Growth and development
  • Maintenance of electrolyte, water, and nutrient balance of blood
  • Regulation of cellular metabolism and energy balance
  • Mobilization of body defenses
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6
Q

Exocrine glands:

A
  • Produce nonhormonal substances (examples: sweat, saliva)

- Have ducts to carry secretion to membrane surface

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7
Q

Endocrine glands:

A
  • Produce hormones

- Lack ducts

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8
Q

Endocrine glands include…

A
  • pituitary
  • thyroid
  • parathyroid
  • adrenal
  • pineal glands
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9
Q

Hypothalamus is a … organ

A

neuroendocrine

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10
Q

Some have exocrine and endocrine functions …

A
  • Pancreas
  • Gonads
  • Placenta
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11
Q

Other tissues and organs that produce hormones…

A

Adipose cells, thymus, and cells in walls of small intestine, stomach, kidneys, and heart

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12
Q

Chemical messenger comparison: Hormones

A

long-distance chemical signals that travel in blood or lymph throughout the body

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13
Q

Chemical messenger comparison: Autocrines

A

short-distance chemical signals that exert effects on same cells that secrete them

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14
Q

Chemical messenger comparison: Paracrines

A

short-distance chemical signals that act locally (same tissue) but affect cells other than those that secrete them

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15
Q

Two main classes of hormones:

A

Amino acid–based hormones
- Amino acid derivatives, peptides, and proteins

Steroids

  • Synthesized from cholesterol
  • Gonadal and adrenocortical hormones
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16
Q

Hormone action on target cells may be to:

A
  • Alter plasma membrane permeability and/or membrane potential by opening or closing ion channels
  • Stimulate synthesis of enzymes or other proteins
  • Activate or deactivate enzymes
  • Induce secretory activity
  • Stimulate mitosis
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17
Q

Hormones act in one of two ways, depending on their chemical nature and receptor location…

A
  1. ) Water-soluble hormones (all amino acid–based hormones except thyroid hormone)
    - Act on plasma membrane receptors
    - Act via G protein second messengers
    - Cannot enter cell
  2. ) Lipid-soluble hormones (steroid and thyroid hormones)
    - Act on intracellular receptors that directly activate genes
    - Can enter cell
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18
Q

Plasma Membrane Receptors and Second-Messenger Systems: Cyclic AMP (cAMP) signaling mechanism

A
  1. ) Hormone (first messenger) binds to receptor
  2. ) Receptor activates a G protein
  3. ) G protein activates or inhibits effector enzyme adenylate cyclase
  4. ) Adenylate cyclase then converts ATP to cAMP (second messenger)
  5. ) cAMP activates protein kinases that phosphorylate (add a phosphate) other proteins
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19
Q

Intracellular Receptors and Direct Gene Activation…

A
  • Lipid-soluble steroid hormones and thyroid hormone can diffuse into target cells and bind with intracellular receptors
  • Receptor-hormone complex enters nucleus and binds to specific region of DNA
  • Helps initiate DNA transcription to produce mRNA
  • mRNA is then translated into specific protein (proteins synthesized have various functions / Ex: metabolic activities, structural purposes, or exported from cell)
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20
Q

Hormone release: Blood levels of hormones

A
  • Controlled by negative feedback systems (Increased hormone effects on target organs can inhibit further hormone release)
  • Levels vary only within narrow, desirable range
  • Hormone release is triggered by Endocrine gland stimuli and
    Nervous system modulation
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21
Q

Endocrine gland stimuli: Humoral stimuli

A

Changing blood levels of ions and nutrients directly stimulate secretion of hormones

  • Ex: Ca2+ in blood
    Declining blood Ca2+ concentration stimulates parathyroid glands to secrete PTH (parathyroid hormone). PTH causes Ca2+ concentrations to rise, and stimulus is removed
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22
Q

Endocrine gland stimuli: Neural stimuli

A

Nerve fibers stimulate hormone release

  • Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines
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23
Q

Endocrine gland stimuli: hormonal stimuli

A

Hormones stimulate other endocrine organs to release their hormones

  • Hypothalamic hormones stimulate release of most anterior pituitary hormones
  • Anterior pituitary hormones stimulate targets to secrete still more hormones
  • Hypothalamic–pituitary–target endocrine organ feedback loop (hormones from final target organs inhibit release of anterior pituitary hormones)
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24
Q

Nervous system modulation: Nervous system can make adjustments to …

A

hormone levels when needed

  • Can modify stimulation or inhibition of endocrine glands
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25
Q

Nervous system modulation: Nervous system can override…

A

normal endocrine controls

  • Ex: under severe stress, hypothalamus and sympathetic nervous system override insulin to allow blood glucose levels to increase
  • Prepare body for “fight or flight”
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26
Q

Target cells must have specific…

A

receptors to which hormone binds

  • ex: ACTH receptors are found only on certain cells of adrenal cortex, but thyroxin receptors are found on nearly all cells of body
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27
Q

Target cell activation depends on three factors:

A
  1. ) Blood levels of hormone
  2. ) Relative number of receptors on/in target cell
  3. ) Affinity (strength) of binding between receptor and hormone
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28
Q

Hormones circulate in blood either…

A

free or bound

  • Steroids and thyroid hormone are attached to plasma proteins; others don’t require carriers
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29
Q

Concentration of circulating hormone reflects:

A
  1. ) Rate of release

2. ) Speed at which it is inactivated and removed from body

30
Q

Hormones can be removed from blood by:

A
  • Degrading enzymes or
  • Kidneys or
  • Liver

Half-life: time required for level of hormone in blood level to decrease by half
- Varies anywhere from fraction of a minute to a week, depending on hormone

31
Q

Amount of hormone can influence number of receptors for that hormone …

A
  • Up-regulation: target cells form more receptors in response to low hormone levels
  • Down-regulation: target cells lose receptors in response to high hormone levels (Desensitizes the target cells to prevent them from overreacting to persistently high levels of hormone)
32
Q

Multiple hormones may act on same target at same time …

A
  • Permissiveness
  • Synergism
  • Antagonism
33
Q

Permissiveness

A

One hormone cannot exert its effects without another hormone being present

  • Ex: reproductive hormones need thyroid hormone to have effect
34
Q

Synergism

A

More than one hormone produces same effects on target cell, causing amplification

  • Ex: glucagon and epinephrine both cause liver to release glucose
35
Q

Antagonism

A

One or more hormones oppose(s) action of another hormone

- Ex: insulin and glucagon

36
Q

Hypothalamus is connected to pituitary gland via …

A

stalk called infundibulum

37
Q

Pituitary secretes at least…

A

eight major hormones

38
Q

It has two major lobes:

A
  • Posterior pituitary: composed of neural tissue that secretes neurohormones
  • Anterior pituitary: consists of glandular tissue
39
Q

Posterior lobe is neural tissue derived from …

A

a downgrowth of brain

40
Q

Posterior lobe secretes …

A

Two neurohormones (oxytocin and ADH)

  • Hormones are stored in axon terminals in posterior pituitary and are released into blood when neurons fire
41
Q

Oxytocin

A
  • Strong stimulant of uterine contractions released during childbirth
  • Also acts as hormonal trigger for milk ejection
  • Both are positive feedback mechanisms
  • Acts as neurotransmitter in brain
42
Q

Antidiuretic hormone (ADH)

A
  • Hypothalamus contains osmoreceptors that monitor solute concentrations
  • If concentration too high, posterior pituitary triggered to secrete ADH
  • Targets kidney tubules to reabsorb more water to inhibit or prevent urine formation
43
Q

Anterior lobe secretes…

A

six hormones - all are peptide hormones

  • All but two are tropic hormones (tropins) that regulate secretion of other hormones
  • Growth hormone (GH)
  • Thyroid-stimulating hormone (TSH) (tropic)
  • Adrenocorticotropic hormone (ACTH) (tropic)
  • Follicle-stimulating hormone (FSH) (tropic)
  • Luteinizing hormone (LH) (tropic)
  • Prolactin (PRL)
44
Q

Growth hormone (GH)

A

Has direct actions on metabolism and indirect growth-promoting actions

  • Direct actions on metabolism:
    (Triggers liver to break down glycogen into glucose
    Increases blood levels of fatty acids for use as fuel and encourages cellular protein synthesis)
  • Indirect actions on growth:
    (GH stimulates most cells to enlarge and divide, but major targets are bone and skeletal muscle)
45
Q

Hypersecretion of GH is usually caused by anterior pituitary tumor …

A
  • In children results in gigantism
    (Can reach heights of 8 feet)
  • In adults results in acromegaly
    (Overgrowth of hands, feet, and face)
46
Q

Hyposecretion of GH

A
  • In children results in pituitary dwarfism (May reach height of only 4 feet)
  • In adults usually causes no problems
47
Q

Regulation of Thyroid hormone secretion…

A

Hypothalamus releases TRH (thyrotropin releasing hormone)

Anterior pituitary releases TSH (thyroid stimulating hormone)

Thyroid gland releases Thyroid hormones (T3/T4)

  • The main functions of the thyroid hormones are to increase basal metabolic rate and body heat production.
  • Low levels of TH can stimulate TRH release. TRH can also override the negative feedback in emergency situations, such as exposure to extreme cold (particularly in infants).
48
Q

Thyroid Hormone (TH)

A
  • Body’s major metabolic hormone
  • Found in two forms:

T4 (thyroxine): major form secreted and in blood
Must be converted to T3 at tissue level

T3 (triiodothyronine): different structure; more active
10x more active than T4 at receptors.

  • Hormones carried in blood by thyroxine-binding globulins (TBGs)
49
Q

Thyroid Hormone (TH) Effects

A
  • increasing basal metabolic rate and body heat production, by turning on transcription of genes concerned with glucose oxidation. this is the hormones calorigenic effect
  • regulating tissue growth and development. TH is critical for normal skeletal and nervous system development and maturation and for reproductive capabilities
  • maintaining blood pressure by increasing the number of adrenergic receptors in blood vessels
50
Q

Ever wonder why most table salt is iodized?

A
  • Lack of iodine decreases TH levels, which triggers increased TSH secretion, triggering thyroid to synthesize more and more unusable thyroglobulin
  • Thyroid enlarges even though TH levels are low
51
Q

Thyroid Disorders: Hyposecretion

A

Called ‘myxedema’

Symptoms:

  • Low metabolic rate
  • Lethargy
  • Feeling cold/chilly
  • Edema
  • Dry skin

Overweight is often secondary to low metabolism.

52
Q

Thyroid Disorders: Hypersecretion

A

Called ‘Graves’ disease’

Symptoms:

  • Elevated metabolic rate
  • Excess sweating
  • Nervousness
  • Irregular heartbeat
  • Exopthalmos

Elevated metabolic rate causes weight loss despite adequate food.

53
Q

Adrenocorticotropic hormone (ACTH)

A
  • ACTH stimulates adrenal cortex to release corticosteroids

Regulation of ACTH release:

  • Triggered by hypothalamic corticotropin-releasing hormone (CRH) in daily rhythm
  • Highest levels in morning
  • Internal and external factors that alter release of CRH include fever, hypoglycemia, and stressors
54
Q

Adrenal Gland

A

Paired, pyramid-shaped organs atop kidneys

Structurally and functionally, it is two glands in one

  • Adrenal cortex: synthesizes and secretes several different hormones
  • Adrenal medulla: nervous tissue that is part of sympathetic nervous system
55
Q

Cortex produces corticosteroids…

A

Three layers of cortical cells produce the different corticosteroids:

  • Mineralocorticoids (glomerulosa cells)
  • Glucocorticoids (fasciculata cells)
  • Gonadocorticoids (reticularis cells)
56
Q

Adrenal cortex: mineralocorticoids

A

Regulate electrolyte concentrations (primarily Na+ and K+) in ECF

  • Importance of Na+: affects ECF volume, blood volume, blood pressure.
  • Importance of K+: sets resting membrane potential of cells

Aldosterone: most potent mineralocorticoid

  • Stimulates Na+ reabsorption by kidneys
  • Results in increased blood volume and blood pressure
  • Stimulates K+ elimination by kidneys
57
Q

Aldosteronism

A

hypersecretion usually due to adrenal tumors

Results in two major problems:

  1. ) Hypertension and edema due to excessive Na+
  2. ) Excretion of K+, leading to abnormal low plasma levels and nonresponsive neurons and muscle
58
Q

Glucocorticoid Overview

A

Hormone: Glucocorticoid (cortisol)

Regulation of Release: stimulated by ACTH, inhibited by feedback back inhibition exerted by cortisol

Target Organ and Effects: body cells; promote gluconeogenesis and hyperglycemia; mobilize fats for energy metabolism; stimulate protein catabolism; assist body to resist stressors; depress inflammatory and immune repsonses

Effects of Hypersecretion vs Hyposecretion: Hyper is cushing’s syndrome. Hypo is addison’s disease

59
Q

Short term vs. long term stress

A

Short-term stressors cause SNS activation and include the release of E and NE from the adrenal medulla.

Long-term/prolonged/chronic stress also causes the endocrine system to exert more of an effect by causing CRH and ACTH release, which leads to mineralo- and gluco-corticoid release. Cortisol exerts negative feedback on CRH and ACTH release.

This long-term stress response can lead to chronic hypertension (due to increased blood volume and sodium levels) as well as diabetes (increased blood glucose levels) and increased risk of infection due to immunosuppression.

60
Q

Short-term stress

A

the hypothalamus activates the adrenal medulla via neural stimuli

short-term stress response helps the body successfully respond to a short-term emergency (running from fire)

61
Q

Long-term stress

A

the hypothalamus activates the adrenal cortex via hormonal stimuli. this greatly reinforces the continuing short-term stress response

long-term stress response helps the body successfully deal with some long-term stressors (starvation). if the stress response is prolonged, it can become detrimental. it may lead to high BP, muscle loss, altered immune function, etc.

62
Q

Hypersecretion- Cushing’s syndrome/disease …

A

Depresses cartilage/bone formation and immune system; inhibits inflammation; disrupts neural, cardiovascular, and gastrointestinal function

  • Causes: tumor on pituitary gland or adrenal cortex; overuse of corticosteroids
  • Treatment: removal of tumor, discontinuation of drugs

Glucocorticoid drugs can control symptoms of many inflammatory diseases (arthritis, allergies) but can also cause undesirable effects.

63
Q

Hyposecretion—Addison’s disease…

A
  • Usually involves deficits in both glucocorticoids and mineralocorticoids
  • Decrease in plasma glucose and Na+ levels
  • Weight loss, severe dehydration, and hypotension are common
  • Treatment: corticosteroid replacement

Early sign is characteristic bronzing of skin due to high levels of ACTH which triggers melanin production in melanocytes

64
Q

Pancreas

A

Triangular gland located partially behind stomach

  • Acinar cells (exocrine) produce enzyme-rich juice for digestion
  • Pancreatic islets (islets of Langerhans) contain endocrine cells
  • Alpha cells produce glucagon (hyperglycemic hormone)
  • Beta cells produce insulin (hypoglycemic hormone)
65
Q

Insulin

A

Secreted when blood glucose levels increase

Insulin lowers blood glucose levels:

  • Enhances membrane transport of glucose into fat and muscle cells
  • Inhibits breakdown of glycogen to glucose
  • Inhibits conversion of amino acids or fats to glucose

Insulin also triggers cells to:

  • Catalyze oxidation of glucose for ATP production: first priority
  • Polymerize glucose to form glycogen
  • Convert glucose to fat (particularly in adipose tissue)
66
Q

Factors that influence insulin release…

A

pancreas beta cells secrete insulin when stimulated by:

  • elevated blood glucose levels
  • rising blood levels of amino acids and fatty acids
  • acetylcholine released by parasympathetic nerve fibers
  • hyperglycemia hormones, this effect is indirect and occurs because all of these hormones increase blood glucose levels

activation of sympathetic NS inhibits insulin release

67
Q

Glucagon

A

Release triggered by decreased blood glucose levels, rising amino acid levels, or sympathetic nervous system

Raises blood glucose levels by targeting liver to:

  • Break down glycogen into glucose (Glycogenolysis)
  • Synthesize glucose from lactic acid and other noncarbohydrates (Gluconeogenesis)
  • Release glucose into blood
68
Q

Negative feedback loops regulating blood glucose levels are controlled by …

A

hormone secretion from the pancreas

69
Q

Diabetes mellitus (DM) can be due to:

A

Hyposecretion of insulin: Type 1

Hypoactivity of insulin: Type 2

70
Q

Three cardinal signs of DM:

A

Polyuria: large urine output
Glucose acts as osmotic diuretic

Polydipsia: excessive thirst
From water loss due to polyuria

Polyphagia: excessive hunger and food consumption
Cells cannot take up glucose and are “starving”

A&P - Study Sets (3 decks)

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