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BIO 235 Midterm 2 > Chapter 18: The Endocrine System > Flashcards

Chapter 18: The Endocrine System Flashcards

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1
Q

Compare the control of the nervous and endocrine system by the following characteristics:

Mediator molecules 
Site of mediator action 
Target cells 
Time to onset of action 
Duration of action
A

Mediator molecules

  • NS: NTs released locally in response to nerve impulses
  • ES: hormones delivered to tissues throughout body by blood

Site of mediator action

  • NS: close to site of release, at synapse; binds to postsynaptic membrane
  • ES: far from site; binds to receptors on/in target cells

Target cells

  • NS: muscle cells, gland cells, other neurons
  • ES: cells throughout the body

Time to onset of action

  • NS: within ms
  • ES: seconds to hrs to days

Duration of action

  • NS: brief (ms)
  • ES: longer (seconds to days)
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2
Q

Define hormone

A

mediator molecule that is release in one part of the body but regulates the activity of cells in others parts of the body

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3
Q

Distinguish between exocrine and endocrine glands

A

Exocrine - secrete products into ducts that cary decorations into body cavities, into lumen of organs, or to the other surface of body (sudoriferous, sebaceous, and digestive glands)

Endocrine - secrete their products into the interstitial fluid surrounding the secretory cells rather than into ducts; they get to target cells via blood (pituitary, thyroid, parathyroid, adrenal, and pineal)

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4
Q

What is the difference between down-regulation and up regulation?

A

down-regulation: if a hormone is present in excess, the number of target-cell receptors may decrease

up-regulation - when a hormone is deficient, the number of receptors may increase

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5
Q

Differentiate between circulating and local hormones

A

Circulating - pass from secretory cells that make them into ISF and then into blood
Local - act locally on neighbouring cells or on same cell without first entering blood

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6
Q

What are paracrines and autocrines?

A

Paracrines - local hormones that act on neighbouring cells

Autocrines - local cells that act on the same cell that secreted them

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7
Q

Describe the 3 lipid-soluble hormones:

steroid
thyroid
nitric oxide

A

steroid - derived from cholesterol; each steroid hormone is quince due to the presence of different chemical groups attached

thyroid (T3 & T4) - are synthesized by attaching iodine to the amino acid tyrosine

nitric oxide - both a hormone and NT

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8
Q

Describe the 3 water-soluble hormones:

Amine
Peptide and protein
Eicosanoid

A

Amine - retain an amino grop

Peptide and protein - amino acid polymers; several have attached carbohydrate group groups are are this a glycoprotein

Eicosanoid - derived from arachidonic acid; two major ropes are prostaglandins and leukotrienes (important local hormones)

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9
Q

What are transport proteins? What are their functions?

A

Lipid-soluble hormone molecules are mostly bound to transport proteins which are synthesized in the liver; they:

  • make lipid soluble hormones temporarily water-soluble increasing solubility in blood
  • retard passsage of small hormone molecules through filtering mechanisms in kidneys
  • provide a ready reserve of hormone
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10
Q

Define free fraction

A

Lipid soluble molecules that are not bound to a transport protein - they diffuse out of capillaries, bind to receptors, and trigger responses

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11
Q

What is the mechanism of action of a lipid-soluble hormone?

A
  1. lipid-soluble hormone diffuses into cell
  2. Activated receptor-hormone complex alters gene expression
  3. Newly formed mRNA directs synthesis of specific proteins on ribosomes
  4. New protons alter cells activity
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12
Q

What is the action of the receptor-hormone complex?

A

Alters geen expression by turning specific genes of nuclear DNA on or off

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13
Q

What is the mechanism of action for a water soluble hormone?

A
  1. Binding of hormone (first messenger) to its receptor activates G protein which activates adenylate cyclase
  2. Activated adenylate cyclase covered ATP to cAMP
  3. . cAMP serves as a second messenger to activate protein kinases
  4. Activated protein kinases phosphorylate collate proteins
  5. Millions of phosphorylated proteins cause reactions that produce physiological responses
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14
Q

Describe the following hormone interactions:

permissive effect
synergistic effect
antagonistic effect

A

permissive effect - actions of some hormones on target cells require a simulates or recent exposure to a second hormone; the second hormone is the premissive one and it can increase # of receptors for other hormone or promote synthesis of a enzyme requires for the expression of the other hormone

synergistic effect - the effects of two hormones acting together is greater or more extensive than the effect of each hormone acting alone

antagonistic effect - one hormone opposes the actions of another hormone

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15
Q

What three types signals control hormone secretion?

A

Signals from the nervous systems
Chemical changes in the blood
Other hormones

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16
Q

Describe the locations of and relationships between the hypothalamus and pituitary gland

A

The pituitary gland attaches to the hypothalamus by a stalk, the infundibulum

The hypothalamus secrets hormones that influences secretions in the pituitary; together they play important roles in the regulation of virtually all aspects of growth, development, metabolism, and homeostasis

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17
Q

What are the two anatomically and functionally separate portions in the pituitary gland?

A

Anterior pituitary - accounts for 75% of the weight and is composed of epithelial cells; consists of the pars distalis and the pars tuberalis

Posteror pituitary - composed of neural tissues; consists of the pars nervosa, infundibulum

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18
Q

Define pars intermedia

A

A third regions of the pituitary gland that atrophies during human fetal development and ceases to exist as a separate lobe in adults

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19
Q

How do releasing and inhibiting hormones influence the pituitary ?

A

They are sent by hypothalamus and either stimulate or suppress hormones

20
Q

Describe the hypophyseal portal system

A

Blood flows from capillaries in the hypothalamus into portal veins that carry blood to capillaries in the anterior pituitary

Neurosecretory cells syntheisize the hypothalamic releasing and inhibiting hormones in their cell bodies and package hormones inside vesicles

The hormones diffuse into the hypophyseal portal system and directly act on the anterior pituitary

Anterior pituitary hormones, known as tropic hormones, then act on other endocrine glands

21
Q

Describe the releasing and inhibting secretions of types of anterior pituitary cells:

Human growth hormone (hGH) 
Thyroid-stimulating hormone (TSH) 
Gonadotropins 
Prolactin 
Adrenocorticostipic hormone (ACTH) 
Melanoycte-stimualting hormone (MSH
A

Human growth hormone (hGH) - secreted by Somatotrophs

  • growth hormone releasing hormone (GHRH)
  • Growth hormone–inhibiting hormone (GHIH)

Thyroid-stimulating hormone (TSH) - secreted by Thyrotrophs

  • Thyrotropin-releasing hormone (TRH).
  • Growth hormone–inhibiting hormone (GHIH).

Gonadotropins - include follice-stimulating hormone (FSH) and luteinizing hormone (LH)
- Gonadotropin-releasing hormone (GnRH).

Prolactin - secreted by Lactotrophs
- Prolactin-releasing hormone (PRH).
Prolactin-inhibiting hormone (PIH), which is dopamine.

Adrenocorticostipic hormone (ACTH) - secreted by Corticotrophs
- Corticotropin-releasing hormone (CRH)

Melanoycte-stimualting hormone (MSH)

  • Corticotropin-releasing hormone (CRH).
  • Dopamine.
22
Q

Which other target gland hormones suppress secretion of hypothalamic and anterior pituitary hormones by negative feedback?

A

Thyroid hormones suppress secretion of TSH by thyrotriphs and of TRH by hypothalamic neurosecretory cells; gonadal hormones suppress secretion of FSH by gonadtrops and of GnRH by hypothalamic neurosecetory cells

23
Q

Describe the principal functions of the following anterior pituitary hormones

Human growth hormone (hGH/ somatotropin)
Thyroid-stimulating hormone (TSH/ thyrotropin)
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Proloactin (PRL)
Adrenocorticotropic hormone (ACTH/corticotropin)
Melanocyte-stimulating hormone (MSH)

A

hGH - stimulates liver, muscle, cailage, bone, and other tissues to synthesize insulin like growth factors that promote growth of body cells, protein synthesis, tissue repair, liplysisi, and elevation of glucose

TSH - stimulates thyroid hormones in thyroid gland

FSH - inmates development of oocytes and induces ovarian secretion in females; stimulates testes to produce sperm in men

LH - in females stimulates secretion of estrogen/prgoreteroone/olvuation; in men stimulates testes to produce testosterone

PRL - promotes milk production

ACTH - stimulates secretion of glucocorticoids by adrenal cortex

MSH - may influence brain activity and can darken skin

24
Q

What is the function of the posterior pituitary?

A

It does not synthesize hormones but it does store and release two hormones

25
Q

Define the hypothalmohyopohyseal tract

A

Axons of hypothalamic neurosecretory cells form the hypothalamohypophyseal tract, which extends from the paraventricular and supraoptic nuclei to the posterior pituitary.

Hormone molecules synthesized in the cell body of a neurosecretory cell are packaged into secretory vesicles that move down to the axon terminals.

Nerve impulses trigger exocytosis of the vesicles, thereby releasing the hormone.

Hormones include oxytocin and antidieuretic hormone (vasopressin)

26
Q

Define pituitcytes

A

Specialized neuroglia in the axon terminals in the posterior pituitary

27
Q

Describe how antidiuretic hormone (ADH) is regulated

A
  1. high blood osmotic pressure stimulus hypothalamic osmoreceptors (neurones in the hypothalamus)
  2. osmoreceptors activate neurosecretory cells that synthesize and release ADH
  3. nerve impulses liberate ADH from axon terminals in the posterior pituitary into the blood stress
  4. Blood carries ADH to kidneys, sudoriferous glands, and smooth muscles in blood vessel walls
  5. low blood osmotic pressure inhibits hypothalamic osmoreceptros
  6. ADH secretion stops
28
Q

Describe the thyroid gland

A

Located inferior to the larynx and is composed of right and left lateral lobes, one on either side of the trachea that are connected by an isthmus

Microscopic sacs called thyroid follicles make up most of the thyroid gland - the wall of each folic consists primarily of cells called follicular cells

29
Q

What two hormones are produced by the follicular cells?

A

Thyroxine and triiodothyronine

Together known as thyroid hormones

30
Q

What are parafollicular cells?

A

The lie between thryroid follicles and help produce the hormone calcitonin which helps regulate calcium homeostasis

31
Q

What is the storage form of thyroid hormones?

A

thyroglobulin (TGB)

32
Q

List two principal actions of the thyroid hormones

A
  1. Increase basal metabolic rate, the rate of oxygen consumption under standard or basal conditions, by stimulating production of ATP
  2. stimulate synthesis of Na+-K+ ATPase pumps which uses more ATP and increases body temrpature, known as the calorigenic effect `
33
Q

How are the actions of the thyroid hormones regulated?

A
  1. low blood levels of T3 and T3 or low metabolic rate stimulates release of TRH
  2. TRH carried by hypophyseal portal veins to anterior pituitary stimulates release of TSH by thryotrophs
  3. TSH released into blood stimulates thyroid follicular cells
  4. T3 and T4 released into blood by follicular cells
  5. Elevated T3 inhibits release of TRH and TSH (negative feedback)
34
Q

How foes calcitonin decrease levels of calcium?

A

Inhibiting the action of osteoclasts, the cells that break down bone extracellular matrix

35
Q

What are the two types of epithelial cells in parathyroid glands?

A

Chief cells - produce parathyroid hormone (PTH)

Oxyphil cell - function unknown

36
Q

Define calcitriol

A

The active form of fit D that is formed in the kidneys by effect of the parathyroid hormone

37
Q

Describe how calcitonin and parathyroid hormones are controlled

A
  1. High level of Ca2+ in blood stimulates thyroid gland parafollicular cells to release more CT
  2. CT inhibits osteoclasts, decreases Ca2+ levels
  3. Low Ca2+ stimulates parathyroid gland chief cells to release more PTH
  4. PTH promotes release of Ca2+ into blood and slows loss of Ca2_ in using, increasing levels
  5. PTH stimulates the kidneys to release calcitriol
  6. calcitriol stimualtes increases absorption of Ca2_ from foods, which increases levels

Summary: Low blood Ca2􏰑 levels stimulate secretion; high blood Ca2􏰑 levels inhibit secretion of parathyrid gland hormone

38
Q

Define pituitary dwarfism and giantism

A

dwarfism - Hyposecretion of hGH during the growth years flows bone growth and the epiphyseal plate closes before normal height is reached

giantism - hypersecretion of hGH during childhood causes abnormal increase in length of long bones

39
Q

Define acromegaly

A

Hypersecretion of hGH during adulthood causing thickening of the bones of hands, feet, cheeks, and jaw

40
Q

Define diabetes insipidus

A

defects in antidiuretic hormone receptors or an inability to secrete ADH

41
Q

Define congenital hypothyroidism

A

Hyposecretion of thyroid hormones present at birth that has devestating consequences if not treated

Can cause severe mental retardation and stunted bone growth

42
Q

Define myexedma

A

Hypothyroidism during the adult years - hallmark of this disorder is edema (accumulation of interdigital fluid)

43
Q

Define graves diseases

A

autoimmune disorder in which the person produces antibodies that mimic the action is thyroid-stimulating hormone (TSH)

They cause hyperthyroidism

44
Q

Define cushing’s syndrome

A

Hypersecretion of cortisol by the adrenal cortex

Characterized by breakdown of muscle proteins and redistribution of body fat - rounded moon face, buffalo hump on back

45
Q

Define addison’s disease

A

Hyposecretion of glucocorticoids and aldosterone causes it

symptoms include mental lethargy, anorexia, nausea, vomitting, weight loss, etc

46
Q

Define diabetes mellitus

A

genetic and environmental factors contribute to onset of the two types of diabetes mellitus—type 1 and type 2—but the exact mechanisms are still unknown.

47
Q

Define hypo and hyper glycemia

A

hypoglycemia, decreased blood glucose level, which occurs because the excess insulin stimulates too much uptake of glucose by body cells.

Hyerglycemia is increased blood glucose elves due to too little insulin

BIO 235 Midterm 2 (8 decks)

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