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Medicine For Engineers Part 1 > Endocrine > Flashcards

Endocrine Flashcards

1
Q

What is the Endocrine System?

A

Endocrine system – the body’s second great controlling system which influences metabolic activities of cells by means of hormones

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2
Q

Which are the Endocrine Glands?

A

Endocrine glands

  • pituitary
  • thyroid
  • parathyroid
  • adrenal
  • pineal
  • thymus
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3
Q

What does the pancreas and gonads produce?

A

The pancreas and gonads produce both hormones and exocrine products

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4
Q

What is an important feature of hypothalamus?

A

The hypothalamus has both neural functions and releases hormones

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5
Q

Apart from glands, gonads, pancreas and hypothalamus - name some other tissues and organs that produce hormones.

A

Other tissues and organs that produce hormones – adipose cells, pockets of cells in the walls of the small intestine, stomach, kidneys, and heart

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6
Q

Which are the Major Endocrine Organs?

A

Major Endocrine Organs

  1. Pineal gland
  2. Hypothalamus
  3. Pituitary gland
  4. Thyroid gland
  5. Parathyroid glands (on dorsal aspect of thyroid gland)
  6. Thymus gland
  7. Adrenal glands
  8. Pancreas
  9. Ovary (female)
  10. Testis (male)
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7
Q

Explain Autocrines and Paracrines

A

Autocrines and Paracrines

  • Autocrines – chemicals that exert effects on the same cells that secrete them
  • Paracrines – locally acting chemicals that affect cells other than those that secrete them
  • These are not considered hormones since hormones are long-distance chemical signals
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8
Q

Explain Hormones

A

Hormones – chemical substances secreted by cells into the extracellular fluids

  • Regulate the metabolic function of other cells
  • Have lag times ranging from seconds to hours
  • Tend to have prolonged effects
  • Are classified as amino acid-based hormones, or steroids
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9
Q

Which are two major classifications of hormones?

A

Types of Hormones

  • Amino acid based
    • Amines, thyroxine, peptide, and protein hormones
  • Steroids – gonadal and adrenocortical hormones
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10
Q

How does hormones alter target cell activity?

A

Hormone Action

Hormones alter target cell activity by one of two mechanisms

  • Second messengers:
    • Regulatory G proteins
    • Amino acid–based hormones
  • Direct gene activation
    • Steroid hormones, thyroid hormone

The precise response depends on the type of the target cell

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11
Q

How does Steroid Hormones act?

A

Steroid Hormones

  • This interaction prompts DNA transcription to produce mRNA
  • The mRNA is translated into proteins, which bring about a cellular effect
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12
Q

Explain the term target cell in the endocrine system.

A

Target Cell Specificity

  • Hormones circulate to all tissues but only activate cells referred to as target cells
  • Target cells must have specific receptors to which the hormone binds
  • These receptors may be intracellular or located on the plasma membrane
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13
Q

Explain how Target cells are activated.

A

Target Cell Activation

  • Target cell activation depends on three factors
    • Blood levels of the hormone
    • Relative number of receptors on the target cell
    • The affinity of those receptors for the hormone
  • Up-regulation – target cells form more receptors in response to the hormone
  • Down-regulation – target cells lose receptors in response to the hormone
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14
Q

How does Hormones circulate in the blood?

A

Hormone Concentrations in the Blood

  • Hormones circulate in the blood in two forms – free or bound
    • Steroids and thyroid hormone are attached to plasma proteins
    • All others are unencumbered
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15
Q

How are Hormones removed from the blood

A

Hormones are removed from the blood by:

  1. Degrading enzymes
  2. The kidneys
  3. Liver enzyme systems
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16
Q

Which are the three types of Hormone interaction?

A

Interaction of Hormones at Target Cells

Three types of hormone interaction

  1. Permissiveness – one hormone cannot exert its effects without another hormone being present
  2. Synergism – more than one hormone produces the same effects on a target cell
  3. Antagonism – one or more hormones opposes the action of another hormone
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17
Q

How is the control of Hormone release executed?

A

Blood levels of hormones:

  • Are controlled by negative feedback systems
  • Vary only within a narrow desirable range
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18
Q

Hormones are synthesized and released in response to… (stimuli)

A

Hormones are synthesized and released in response to:

  1. Humoral stimuli
  2. Neural stimuli
  3. Hormonal stimuli
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19
Q

Explain Humoral Stimuli.

A

Humoral stimuli.

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20
Q

Explain Neural Stimuli

A

Neural Stimuli

Neural stimuli – nerve fibers stimulate hormone release

  • Preganglionic sympathetic nervous system (SNS) fibers stimulate the adrenal medulla to secrete catecholamines
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21
Q

Explain Hormonal Stimuli

A

Hormonal Stimuli

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22
Q

Describe the Pituitary Gland (Hypophysis)

A

Pituitary gland - two-lobed organ that secretes nine major hormones

  • Neurohypophysis – posterior lobe (neural tissue) and the infundibulum
    • Receives, stores, and releases hormones from the hypothalamus
  • Adenohypophysis – anterior lobe, made up of glandular tissue
    • Synthesizes and secretes a number of hormones
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23
Q

Explain the Pituitary-Hypothalamic Relationships for Posterior Lobe

A

Pituitary-Hypothalamic Relationships: Posterior Lobe

  • The posterior lobe is a downgrowth of hypothalamic neural tissue
  • Has a neural connection with the hypothalamus (hypothalamic-hypophyseal tract)
  • Nuclei of the hypothalamus synthesize oxytocin and antidiuretic hormone (ADH)
  • These hormones are transported to the posterior pituitary
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24
Q

Explain the Pituitary-Hypothalamic Relationships for Anterior Lobe

A

Pituitary-Hypothalamic Relationships: Anterior Lobe

  • The anterior lobe of the pituitary is an outpocketing of the oral mucosa
  • There is no direct neural contact with the hypothalamus
  • There is a vascular connection, the hypophyseal portal system, consisting of:
    • The primary capillary plexus
    • The hypophyseal portal veins
    • The secondary capillary plexus
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25
Q

Which are the 6 hormones of the adenhypophysis?

A

Adenophypophyseal Hormones

The six hormones of the adenohypophysis:

  • Abbreviated as GH, TSH, ACTH, FSH, LH, and PRL
  • GH=Growth Hormone, PRL=Prolactin, TSH=Thyroid-stimulating hormone, ACTH=Adrenocorticotropic hormone, FSH=Follicle-stimulating hormone, LH=Luteinizing hormone
  • Regulate the activity of other endocrine glands

In addition, pro-opiomelanocortin (POMC):

  • Has been isolated from the pituitary
  • Is split into ACTH, opiates, and MSH
26
Q

Describe the Growth Hormone (GH)

A

Growth Hormone (GH)

Produced by somatotropic cells of the anterior lobe (pituitary gland) that:

  • Stimulate most cells, but target bone and skeletal muscle
  • Promote protein synthesis and encourage the use of fats for fuel
  • Most effects are mediated indirectly by somatomedins
27
Q

What is Prolactin (PRL)?

A

Prolactin (PRL)

  • In females, stimulates milk production by the breasts
  • Triggered by the hypothalamic prolactin-releasing hormone (PRH)
  • Inhibited by prolactin-inhibiting hormone (PIH)
  • Blood levels rise toward the end of pregnancy
  • Suckling stimulates PRH release and encourages continued milk production
28
Q

Which hormones does the Posterior Pituitary gland store?

A

Posterior pituitary – made of axons of hypothalamic neurons, stores antidiuretic hormone (ADH) and oxytocin

  • ADH and oxytocin are synthesized in the hypothalamus
29
Q

What does the hotmone ADH influence?

A
  • (Antidiuretic hormone) ADH influences water balance
  • ADH helps to avoid dehydration or water overload
  • Prevents urine formation
  • Osmoreceptors monitor the solute concentration of the blood
  • With high solutes, ADH preserves water
  • With low solutes, ADH is not released, thus causing water loss
  • Alcohol inhibits ADH release and causes copious urine output
30
Q

What does Oxytocin influence?

A
  • Oxytocin stimulates smooth muscle contraction in breasts and uterus
  • Oxytocin is a strong stimulant of uterine contraction
  • Regulated by a positive feedback mechanism to oxytocin in the blood
  • This leads to increased intensity of uterine contractions, ending in birth
  • Oxytocin triggers milk ejection (“letdown” reflex) in women producing milk
  • Synthetic and natural oxytocic drugs are used to induce or hasten labor
  • Plays a role in sexual arousal and satisfaction in males and nonlactating females
31
Q

Describe the Thyroid Gland. What substance does the follicles produce?

A

Thyroid Gland

  • The largest endocrine gland, located in the anterior neck, consists of two lateral lobes connected by a median tissue mass called the isthmus
  • Composed of follicles that produce the glycoprotein thyroglobulin
  • Colloid (thyroglobulin + iodine) fills the lumen of the follicles and is the precursor of thyroid hormone
  • Other endocrine cells, the parafollicular cells, produce the hormone calcitonin
32
Q

What is the function of Thyroid Hormone?

A

Thyroid Hormone

Thyroid hormone – major metabolic hormone

  • Consists of two related iodine-containing compounds
    • T 4 – thyroxine; has two tyrosine molecules plus four bound iodine atoms
    • T 3 – triiodothyronine; has two tyrosines with three bound iodine atoms
33
Q

Effects of Thyroid Hormone

A

Effects of Thyroid Hormone

TH is concerned with:

  • Glucose oxidation
  • Increasing metabolic rate
  • Heat production

TH plays a role in:

  • Maintaining blood pressure
  • Regulating tissue growth
  • Developing skeletal and nervous systems
  • Maturation and reproductive capabilities
34
Q

Explain how Thyroid Hormone is synthesized

A

Synthesis of Thyroid Hormone

  • Thyroglobulin is synthesized and discharged into the lumen
  • Iodides (I –) are actively taken into the cell, oxidized to iodine (I 2), and released into the lumen
  • Iodine attaches to tyrosine, mediated by peroxidase enzymes, forming T 1 (monoiodotyrosine, or MIT), and T 2 (diiodotyrosine, or DIT)
  • Iodinated tyrosines link together to form T 3 and T 4
  • Colloid is then endocytosed and combined with a lysosome, where T 3 and T 4 are cleaved and diffuse into the bloodstream
35
Q

How does transport and regulation of TH work?

A

Transport and Regulation of TH

  • T 4 and T 3 bind to thyroxine-binding globulins (TBGs) produced by the liver
  • Both bind to target receptors, but T 3 is ten times more active than T 4
  • Peripheral tissues convert T 4 to T 3
  • Mechanisms of activity are similar to steroids
  • Regulation is by negative feedback
  • Hypothalamic thyrotropin-releasing hormone (TRH) can overcome the negative feedback
36
Q

What is Calcitonin?

A

Calcitonin

  • A peptide hormone produced by the parafollicular, or C, cells
  • Lowers blood calcium levels in children
  • Antagonist to parathyroid hormone (PTH
  • Calcitonin targets the skeleton, where it:
    • Inhibits osteoclast activity (and thus bone resorption) and release of calcium from the bone matrix
    • Stimulates calcium uptake and incorporation into the bone matrix
  • Regulated by a humoral (calcium ion concentration in the blood) negative feedback mechanism
37
Q

Describe the Parathyroid Glands. What is the hormone the principal cells secrete?

A

Parathyroid Glands

  • Tiny glands embedded in the posterior aspect of the thyroid
  • Cells are arranged in cords containing oxyphil and chief cells
  • Chief (principal) cells secrete PTH
  • PTH (parathormone) regulates calcium balance in the blood
38
Q

What are the Effects of Parathyroid Hormone?

A

Effects of Parathyroid Hormone

  • PTH release increases Ca2+ in the blood as it:
    • Stimulates osteoclasts to digest bone matrix
    • Enhances the reabsorption of Ca2+ and the secretion of phosphate by the kidneys
    • Increases absorption of Ca2+ by intestinal mucosal
  • Rising Ca2+ in the blood inhibits PTH releas
39
Q

Explain the structure and functionality of Adrenal (Suprarenal) Glands.

A

Adrenal (Suprarenal) Glands

  • Adrenal glands – paired, pyramid-shaped organs atop the kidneys
  • Structurally and functionally, they are two glands in one
    • Adrenal medulla – neural tissue that acts as part of the SNS
    • Adrenal cortex – glandular tissue derived from embryonic mesoderm
40
Q

What is the Adrenal Cortex?

A

Adrenal Cortex

  • Synthesizes and releases steroid hormones called corticosteroids
  • Different corticosteroids are produced in each of the three layers
    • Zona glomerulosa – mineralocorticoids (chiefly aldosterone)
    • Zona fasciculata – glucocorticoids (chiefly cortisol)
    • Zona reticularis – gonadocorticoids (chiefly androgens)
41
Q

What is the function of Mineralocorticoids?

A

Mineralocorticoids

  • Regulate electrolytes in extracellular fluids
  • Aldosterone – most important mineralocorticoid
    • Maintains Na + balance by reducing excretion of sodium from the body
    • Stimulates reabsorption of Na + by the kidneys

Aldosterone secretion is stimulated by:

  • Rising blood levels of K +
  • Low blood Na +
  • Decreasing blood volume or pressure
42
Q

What are the Four Mechanisms of Aldosterone Secretion

A

The Four Mechanisms of Aldosterone Secretion

  1. Renin-angiotensin mechanism – kidneys release renin, which is converted into angiotensin II that in turn stimulates aldosterone release
  2. Plasma concentration of sodium and potassium – directly influences the zona glomerulosa cells
  3. ACTH – causes small increases of aldosterone during stress
  4. Atrial natriuretic peptide (ANP) – inhibits activity of the zona glomerulosa
43
Q

What is the Mechanism of Glucocorticoids (Cortisol)?

A

Glucocorticoids (Cortisol)

  • Help the body resist stress by:
    • Keeping blood sugar levels relatively constant
    • Maintaining blood volume and preventing water shift into tissue
  • Cortisol provokes:
    • Gluconeogenesis (formation of glucose from noncarbohydrates)
    • Rises in blood glucose, fatty acids, and amino acids
44
Q

What occurs with Excessive Levels of Glucocorticoids?

A

Excessive Levels of Glucocorticoids

  • Excessive levels of glucocorticoids:
    • Depress cartilage and bone formation
    • Inhibit inflammation
    • Depress the immune system
    • Promote changes in cardiovascular, neural, and gastrointestinal function
45
Q

What are Gonadocorticoids?

A

Gonadocorticoids (Sex Hormones)

  • Most gonadocorticoids secreted are androgens (male sex hormones), and the most important one is testosterone
  • Androgens contribute to:
    • The onset of puberty
    • The appearance of secondary sex characteristics
    • Sex drive in females
  • Androgens can be converted into estrogens after menopause
46
Q

What is the Adrenal Medulla?

A

Adrenal Medulla

  • Made up of chromaffin cells that secrete epinephrine (adrenalin) and norepinephrine (noradrenalin)
  • Secretion of these hormones causes:
    • Blood glucose levels to rise
    • Blood vessels to constrict
    • The heart to beat faster
    • Blood to be diverted to the brain, heart, and skeletal muscle
47
Q

In what areas are the Epinephrine and Norepinephrine more potent?

A

Adrenal Medulla

  • Epinephrine is the more potent stimulator of the heart and metabolic activities
  • Norepinephrine is more influential on peripheral vasoconstriction and blood pressure
48
Q

What is the link between stress and the Adrenal Gland?

A

Stress and the Adrenal Gland

49
Q

Describe the structure and functionality of the Pancreas.

A

Pancreas

  • A triangular gland, which has both exocrine and endocrine cells, located behind the stomach
  • Acinar cells produce an enzyme-rich juice used for digestion (exocrine product)
  • Pancreatic islets (islets of Langerhans) produce hormones (endocrine products)
  • The islets contain two major cell types:
    • Alpha ( α) cells that produce glucagon
    • Beta ( β) cells that produce insulin
50
Q

What are the major target of Glucagon? Describe Glucagon.

A

Glucagon

  • A 29-amino-acid polypeptide hormone that is a potent hyperglycemic agent
  • Its major target is the liver, where it promotes:
    • Glycogenolysis – the breakdown of glycogen to glucose
    • Gluconeogenesis – synthesis of glucose from lactic acid and noncarbohydrates
    • Release of glucose to the blood from liver cells
51
Q

Explain the structure and functionality of Insulin.

A

Insulin

  • A 51-amino-acid protein consisting of two amino acid chains linked by disulfide bonds
  • Synthesized as part of proinsulin and then excised by enzymes, releasing functional insulin
  • Insulin:
    • Lowers blood glucose levels
    • Enhances transport of glucose into body cells
    • Counters metabolic activity that would enhance blood glucose levels
52
Q

Explain the Effects of Insulin Binding.

A

Effects of Insulin Binding

  • The insulin receptor is a tyrosine kinase enzyme
  • After glucose enters a cell, insulin binding triggers enzymatic activity that:
    • Catalyzes the oxidation of glucose for ATP production
    • Polymerizes glucose to form glycogen
    • Converts glucose to fat (particularly in adipose tissue)
53
Q

Describe the Regulation of Blood Glucose Levels.

A

Regulation of Blood Glucose Levels

54
Q

Explain the cause and 3 cardinal signs of Diabetes Mellitus (DM).

A

Diabetes Mellitus (DM)

  • Results from hyposecretion or hypoactivity of insulin
  • The three cardinal signs of DM are:
    • Polyuria – huge urine output
    • Polydipsia – excessive thirst
    • Polyphagia – excessive hunger and food consumption
  • Hyperinsulinism – excessive insulin secretion, resulting in hypoglycemia
55
Q

Explain the location and secretory product of Pineal Gland.

A

Pineal Gland

  • Small gland hanging from the roof of the third ventricle of the brain
  • Secretory product is melatonin
  • Melatonin is involved with:
    • Day/night cycles
    • Physiological processes that show rhythmic variations (body temperature, sleep, appetite)
56
Q

Describe the Thymus.

A

Thymus

  • Lobulated gland located deep to the sternum (=Bröstben)
  • Major hormonal products are thymopoietins and thymosins
  • These hormones are essential for the development of the T lymphocytes (T cells) of the immune system
57
Q

Which hormone does the heart produce?

A

Heart – produces atrial natriuretic peptide (ANP), which reduces blood pressure, blood volume, and blood sodium concentration

58
Q

Which hormones does the GI-tract produce?

A

Gastrointestinal tract – enteroendocrine cells release local-acting digestive hormones

59
Q

Which hormone do the Kidneys produce?

A

Kidneys – secrete erythropoietin, which signals the production of red blood cells

60
Q

Which hormone does the skin produce?

A

Skin – produces cholecalciferol, the precursor of vitamin D

61
Q

Which hormone does the Adipose tissue produce?

A

Adipose tissue – releases leptin, which is involved in the sensation of satiety, and stimulates increased energy expenditure

Medicine For Engineers Part 1 (6 decks)

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