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Fundamentals of Anatomy & Physiology > The Endocrine System > Flashcards

The Endocrine System Flashcards

1
Q

Direct communication

A

Occurs between two cells of the same type in extensive physical contact

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2
Q

Gap junctions

A
  1. Coordinate ciliary movement among epithelial cells
  2. Coordinate the contractions of cardiac muscle cells
  3. Facilitate the propagation of action potentials from one neuron to the next at electrical synapses
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3
Q

Paracrine communication

A

Messages occur between cells within a single tissue

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4
Q

Autocrine communication

A

Occurs when the messages affect the same cells that secrete them

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5
Q

Endocrine communication

A

Occurs when the endocrine system uses hormones to relay information and instructions between cells in distant portions of the body

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6
Q

Target cells

A

Specific cells in other tissues that have the receptors needed to bind and read hormonal messages

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7
Q

Synaptic communication

A

Neurons release neurotransmitter at a synapse very close to target cells that have the appropriate receptors

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8
Q

Differences between endocrine and nervous communication

A

Nervous: split-second, specific, short-lived
Endocrine: slow, affect all cells, long-lasting

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9
Q

Similarities of nervous and endocrine communication

A
  1. Rely on the release of chemicals that bind to specific receptors on their target cells
  2. Share chemical messengers
  3. Regulated mainly by negative feedback control mechanisms
  4. Aim to control homeostasis
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10
Q

Major processes affected by hormones

A
  1. Growth and development
  2. Reproduction
  3. Regulation of cell metabolism and energy balance
  4. Regulation of body water content and levels electrolytes and organic nutrients
  5. Mobilisation of body defences
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11
Q

Endocrine cells

A

Glandular secretory cells that release their secretions into the extracellular fluid

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12
Q

Exocrine cells

A

Secrete their products onto epithelial surfaces through ducts

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13
Q

Classes of hormones

A
  1. Amino acid derivatives
  2. Peptide hormones
  3. Lipid derivatives
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14
Q

Amino acid deriatives

A
  • Synthesised from amino acids tyrosine (thyroid hormones, E, NE and dopamine) and tryptophan (melatonin)
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15
Q

Peptide hormones

A

Glycoproteins and short polypeptides and small proteins

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16
Q

Lipid derivatives

A
  1. Eicosanoids

2. Steroid hormones

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17
Q

Eicosanoids

A

Signalling molecules including leukotrienes, prostaglandins, thromboxanes and prostacyclins

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18
Q

Inactivation of hormones

A

A freely circulating hormone remains functional for less than 1 hour

It is inactivated when:

  1. It diffuses out of the bloodstream and binds to receptors on target cells
  2. It is absorbed and broken down by cells of the liver or kidneys
  3. It is broken down by enzymes in the blood or interstitial fluids
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19
Q

Binding of a hormone

A
  1. Alter genetic activity
  2. Alter the rate of protein synthesis
  3. Change membrane permeability
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20
Q

Hormone receptor

A

Protein molecule to which a particular molecule binds strongly

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21
Q

Why do hormones have different effects on different tissues?

A

Cells have different combinations in different tissues

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22
Q

Down regulation

A

A process in which the presence of a hormone triggers a decrease in the number of hormone receptors

Cells become less sensitive to high levels of a particular hormone

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23
Q

Up regulation

A

A process in which the absence of a hormone triggers an increase in the number of hormone receptors

Cells become more sensitive to low levels of a particular hormone

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24
Q

Extracellular receptors

A

E, NE and dopamine
Peptide hormones

(Can’t penetrate a plasma membrane because they aren’t lipid soluble)

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25
Q

First messenger

A

A hormone that binds to an extracellular receptor

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26
Q

Second messenger

A

An intermediary molecule that appears due to a hormone-receptor interaction

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27
Q

Amplification

A

When a small number of hormone molecules binds to extracellular receptors, thousands of second messengers may appear in a cell

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28
Q

G protein

A

An enzyme complex coupled to a membrane receptor that serves as a link between the first and second messenger

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29
Q

Increasing cAMP level

A
  1. Activated G protein activates the enzyme adenylate cyclase
  2. Adenylate cyclase converts ATP to cAMP
  3. cAMP functions as a second messenger by activating kinase
  4. Generally cAMP activates kinase that phosphorylate proteins which have an effect on the cell
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30
Q

Phosphodiesterase (PDE)

A

Inactivate cAMP by converting it to AMP

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31
Q

Effects of cAMP

A

Metabolic activity of the cell accelerated

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32
Q

Opening of calcium ion channels

A
  1. G protein first activates the enzyme phospholipase C (PLC)
  2. This enzyme triggers a receptor cascade that begins with the production of DAG and IP3 from membrane phospholipids
  3. IP3 diffuses into the cytoplasm and triggers the release of CA2+ from intracellular reserves
  4. Combination of DAG and intracellular calcium ions activates protein kinase C (PKC) > phosphorylation of calcium ion channel proteins
  5. Calmodulin binds with calcium ions which can activate specific cytoplasmic enzymes
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33
Q

Which hormones target intracellular receptors?

A

Mostly steroid and thyroid hormones

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34
Q

Steroid hormones

A

Alter the rate of DNA transcription in the nucleus and so change the pattern of protein synthesis

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35
Q

Thyroid hormones

A

Activate specific genes or change the rate of transcription

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36
Q

Negative feedback

A

A stimulus triggers the production of a hormone whose direct or indirect effects reduce the intensity of the stimulus

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37
Q

Triggers of hormone secretion

A
  1. Humoral stimuli: changes inextracellular fluid
  2. Hormonal stimuli: arrival of specific hormone
  3. Neural timuli: arrival of neurotransmitters
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38
Q

Infundibulum

A

Connects the hypothalamus to the pituitary gland

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39
Q

3 mechanisms of hypothalamic control over endocrine function

A
  1. Production of ADH and OXT > release of ADH and OXT from posterior lobe
  2. Secretion of regulatory hormones to control activity of the anterior lobe of the pituitary gland > hormones secreted by the anterior lobe control other endocrine organs
  3. Control of sympathetic output to adrenal medulla > secretion of E and NE from adrenal medulla
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40
Q

Adenohypophysis

A

Anterior lobe of the pituitary gland

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41
Q

3 regions of adenohypophysis

A
  1. Pars distalis: largest
  2. Pars tuberalis: extension
  3. Pars intermedia: narrow band
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42
Q

Fenestrated capillaries

A

Allow relatively large molecules to enter or leave the bloodstream

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43
Q

Blood supply to pituitary gland

A
  1. Superior hypophyseal artery delivers blood to a capillary network in the upper infundibulum
  2. Inferior hypophyseal artery delivers blood to the posterior lobe of the pituitary gland
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44
Q

Blood leaving pituitary gland

A
  1. Portal vessels deliver blood containing regulatory hormones to the capillary network in the anterior lobe of the pituitary
  2. Hypophyseal veins carry blood containing the pituitary hormones to the cardiovascular system for delivery to the rest of the body
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45
Q

Portal vessels

A

Link two capillary networks

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46
Q

Benefits of hypophyseal portal system

A

Ensures that all the hypothalamic hormones entering portal vessels reach the target cells in the anterior lobe before being diluted through mixing with general circulation

47
Q

Releasing hormone (RH)

A

Stimulates the synthesis and secretion of one or more hormones at the anterior lobe

48
Q

Inhibiting hormone (IH)

A

Prevents the synthesis and secretion of hormones from the anterior lobe

49
Q

Thyroid stimulating hormone (TSH)

A

Targets the thyroid gland and triggers the release of thyroid hormones

50
Q

Adrenocorticotrophic hormone (ACTH)

A

Stimulates the release of steroid hormones by the adrenal cortex

Affect glucocorticoids (glucose metabolism)

51
Q

Gonadotropins

A

Regulate activities of the gonads

  1. Follicle-stimulating hormone
  2. Luteinizing hormone
52
Q

Follicle-stimulating hormone

A

Promotes follicle development in females

Stimulates the secretion of estrogens

53
Q

Luteinizing hormone

A

Females
Induces ovulation
Promotes ovarian secretion of estrogens and progestrone

Males
Stimulates production of androgens

54
Q

Hypogonadism

A

Caused by abnormally low production of gonadotropins

Prevents sexual maturation in children

55
Q

Prolactin (PLR)

A

Stimulates mammary gland development in females

56
Q

Growth hormone (GH)

A

Stimulates cell growth and division by accelerating rate of protein synthesis

57
Q

Neurohypophysis

A

Posterior lobe of pituitary gland

Contains the axons of hypothalamic neurons

58
Q

Supra-optic nuclei

A

Produce ADH

59
Q

Paraventricular nuclei

A

Produce OXT

60
Q

ADH

A

Released in response to an increase in the solute concentration in the blood or a decrease in blood volume or pressure

Acts on the kidneys to retain water and decrease urination

61
Q

OXT

A

Women
Stimulates smooth muscle contraction in the wall of the uterus, promoting L&D
Stimulates ejection of milk

Men
Stimulates smooth muscle contraction in the sperm duct and prostate gland

62
Q

Thyroid gland

A

Ductless gland in the neck that secretes hormones regulating growth, development and metabolism

63
Q

Isthmus

A

Connect two lobes of thyroid gland

64
Q

C cells

A

Lie between cuboidal follicle cells and their basement membrane

65
Q

Follicle cavity

A

Holds colloid fluid

Surrounded by follicle cells

66
Q

Thyroid hormones

A

T3 and T4

Regulated by thyroid-stimulating hormone

67
Q

Synthesis of thyroid hormones

A
  1. Iodide ions are absorbed from the digestive tract delivered to the thyroid gland by the bloodstream
  2. Iodide ions diffuse to the apical surface of each follicle cell where they are converted into an atom of iodine. The tyrosine portion of thyroglobulin bind the iodine atoms
  3. Iodine-containing thyroxine molecules become linked to form T3 and T4
  4. Follicle cells remove thyroglobulin from the follicles by endocytosis
  5. Lysosomal enzymes break down the thyroglobulin and the amino acids and thyroid hormones enter the cytoplasm
  6. The released T3 and T4 diffuse from the follicle cell into the bloodstream
  7. A majority of the T3 and T4 bind to transport proteins
68
Q

Functions of thyroid hormones

A

Depend on location of hormones:

  1. Cytoplasmic receptors: storage
  2. Mitochondria: increase rates of ATP production
  3. In the nucleus: activates genes that control synthesis of enzymes involved in energy activation and use
69
Q

Calorigenic effect

A

Thyroid hormones also activate genes that code for enzymes involved in glycolysis and ATP production, increasing metabolic rate of the cell

70
Q

Calcitonin

A

Produced by C cells of the thyroid gland

Helps to regulate Ca2+ concentration in body fluids

71
Q

Parathyroid glands

A

Four
Parathyroid cells produce parathyroid hormone
Parathyroid oxyphil cells

72
Q

Parathyroid cells

A

Monitor the circulating concentration of calcium ions

Secrete PTH when Ca2+ blood concentration falls

73
Q

Effects of parathyroid hormones

A
  1. Mobilises calcium from bone by affecting osteoblast and osteoclast activity
  2. Enhances the reabsorption of Ca2+ by the kidneys, reducing urinary loss
  3. Stimulates the formation and secretion of calcitriol by the kidneys
74
Q

Adrenal glands

A

Two

Adrenal cortex produces steroid hormones

75
Q

Corticosteroids

A

Steroid hormones produced by adrenal glands

Exert their effects by turning on transcription of certain genes in the nuclei of the target cells

76
Q

Zones of the adrenal cortex

A
  1. Outer zona glomerulosa
  2. Middle zona fasciculata
  3. Inner zona reticularis
77
Q

Zona glomerulosa

A

Outer

Produces mineralocorticoids

78
Q

Mineralocorticoids

A

Steroid hormones that affect the electrolyte composition of body fluids

79
Q

Aldosterone

A

Main mineralocorticoid of the zona glomerulosa

Stimulates conversation of sodium ions and elimination of potassium ions

80
Q

Zona fasciculata

A

Middle

Produces glucocorticoids

81
Q

Glucocorticoids

A

When stimulated by ACTH, zona fasciculata secretes cortisol, corticosterone and cortisone

Speed up the rate of glucose synthesis and glycogen formation
Also anti-inflammatory

82
Q

Zona reticularis

A

When stimulated by ACTH, zona reticularis secretes small amounts of androgens

83
Q

Adrenal medulla

A

Secretes E and NE

84
Q

Pineal gland

A

Main part of the epithalamus

Contains neurons, neuroglia and pinealocytes

85
Q

Pinealocytes

A

Synthesise melatonin from seratonin

86
Q

Functions of melatonin

A
  1. Influencing circadian rhythyms
  2. Inhibiting reproductive functions
  3. Protecting against damage by free radicals
87
Q

Exocrine pancreas

A

Consists of clusters of gland cells and their attached ducts
Secrete an alkaline, enzyme-rich fluid that reaches the lumen of the digestive tract through a network of secretory ducts

88
Q

Endocrine pancreas

A

Small groups of cells scattered among the exocrine cells

89
Q

Pancreatic islets

A

Clusters in endocrine pancreas

90
Q

Pancreatic islet cells

A

Alpha, beta, delta and pancreatic polypeptide cells

91
Q

Alpha cells

A

Produce glucagon which raises blood glucose level

92
Q

Beta cells

A

Produce insulin which lowers blood glucose level

93
Q

Delta cells

A

Produce peptide hormone which supresses the release of glucagon and insulin

94
Q

Pancreatic polypeptide cells

A

Produce pancreatic polypeptide which inhibits gallblader contractions and regulates the production of some pancreatic enzymes

95
Q

Effects of insulin

A
  1. Accelerating glucose uptake
  2. Accelerating glucose use
  3. Stimulating glycogen formation
  4. Stimulating amino acid absorption and protein synthesis
  5. Stimulating triglyceride formation

Decreases blood glucose levels

96
Q

Effects of glucagon

A
  1. Stimulating the breakdown of glycogen
  2. Stimulating the breakdown of triglycerides
  3. Stimulating the production and release of glucose

Increases blood glucose levels

97
Q

Diabetes mellitus

A

Glucose accumulates in the blood and urine as a result of faulty glucose metabolism

98
Q

Calcitriol

A

Steroid hormone secreted by the kidneys in response to PTH

Stimulates calcium and phosphate ion absorption along the digestive tract

99
Q

Eryhtropoietin

A

Peptide hormone secreted by the kidneys in response to low oxygen levels in kidney tissues
Stimulates red bone marrow to produce RBCs

100
Q

Renin

A

Released by specialised kidney cells in response to

  1. Sympathetic stimulation
  2. A decline in renal blood flow

Functions as an enzyme that starts RAAS cascade (BP regulation and electrolyte metabolism)

101
Q

RAAS

A
  1. Renin converts to angiotensinogen
  2. ACE modifies angiontensin I to angiotension II
  3. Angiotension II secretes aldosterone
102
Q

Natriuretic peptides

A

If blood volume becomes too great, endocrine cells are stretched excessively to the point which they begin to secretes natriuretic peptides

Promote the loss of Na+ and water by the kidneys

103
Q

Thymus

A

Located in the mediastinum

104
Q

Interstitial endocrine cells

A

In males, produce androgens

105
Q

Nurse cells

A

Support differentiation and physical maturation of sperm

Secrete inhibin under FSH stimulation

106
Q

Estrogen

A

Produced in females in the ovaries under FSH and LH stimulation

107
Q

Leptid

A

Peptide hormone produced by adipose tissue

Feedback control of appetite

108
Q

Hormonal effects

A
  1. Antagonistic: opposing
  2. Synergistic: additive
  3. Permissive: one is needed for the other
  4. Integrative: different but complementary results
109
Q

Hyperglycemia

A

High glucose levels in the blood

110
Q

Glycosuria

A

Glucose appears in the urine

111
Q

Polyuria

A

Urine volume becomes excessive

112
Q

Type 1 diabetes

A

Inadequate insulin production by the pancreatic beta cells

113
Q

Type 2 diabetes

A

Normal insulin production but tissues don’t respond properly

114
Q

3 phases of general adaptation syndrome

A
  1. Alarm phase (flight or fight, sympathetic division of the ANS)
  2. Resistance phase (glucocorticoids)
  3. Exhaustion phase (eventual breakdown of homeostatic regulation and failure of one or more organs

Fundamentals of Anatomy & Physiology (25 decks)

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