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Anatomy > (LESSON 18) Endocrine System > Flashcards

(LESSON 18) Endocrine System Flashcards

1
Q

Endocrine System

A

A series of ductless glands that secrete messenger molecules called hormones into the circulation. These hormones travel to distant body cells and signal characteristic physiological responses in those cells.

Controls and integrates the functions of other organ systems in the body.

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2
Q

Hormones

A

messenger molecules.

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3
Q

Purely Endocrine Organs

A
  • primary gland: at the base of the brain
  • pineal gland: in the roof of the diencephalon
  • thyroid gland: in the neck
  • parathyroid gland: in the neck
  • adrenal gland on the kidneys
    • adrenal cortex
    • adrenal medulla
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4
Q

Partly Endocrine Organs

A
  • pancreas
  • thymus
  • gonads
  • hypothalamus
    • neuroendocrine organ
  • heart
  • skin
  • kidneys
  • placenta
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5
Q

Origination of most endocrine cells

A
  • epithelia
  • however, endocrine system is so diverse that it also includes hormone-secreting neurons, muscle cells, and fibroblast-like cells
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6
Q

Classes of hormones

A
  • Amino-acid based hormones
    • modified amino acids
      • amines
    • peptides
      • short chains of amino acids
    • proteins
      • long chains of amino acids
  • Steroids
    • lipid molecules derived from cholesterol
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7
Q

Basic Hormone Action

A
  1. Cluster, cords, or branching endocrine cells maximizes contact with capillaries
  2. Cells release hormones into extracellular space
  3. Hormones immediately enter capillaries
  4. Circulate throughout the entire body
  5. a given hormone influences only specific tissue cells, target cells
  6. Target cells’ specific recepter molecules allow hormones to bind to tissue
  7. Target cell reacts in preprogrammed way
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8
Q

Humoral Stimuli

(type of hormone stimuli)

A
  • secrete hormones in direct response to changing levels of ions or nutrients in the blood
  • humoral: relating to the blood and other body fluids
  • simplest endocrine control mechanism
  • ex:
    • cells of the parathyroid gland directly monitor concentration of calcium ions in the blood and then respond to any decline in this concentration by secreting a hormone that acts to reverse the decline
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9
Q

Neural Stimuli

type of hormone stimuli

A
  • A few endocrine glands are controlled this way
  • ex
    • sympathetic nerve fibers stimulate cells in the adrenal medulla to release epinephrine and norepinephrine during flight-or-flight situations
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10
Q

hormonal stimuli

type of hormonal stimuli

A
  • glands that secrete their hormones in response to hormonal stimuli received from other endocrine glands.
  • AKA: the purpose of some hormones is to promote the secretion of other hormones
  • ex
    • hypothalamus secretes some hormones that stimulate the anterior part of the pituitary gland
    • Pituitary gland then secrete its hormones which stimulate hormonal secretion by other glands:
      • thyroid
      • adrenal cortex
      • gonads
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11
Q

Feedback Loops

A
  • Control hormone secretion
  • Ensure that hormone concentration stay within a narrow “desirable” range in the blood
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12
Q

Negative feedback loop

A
  • if blood concentration declines below a minimum set point then more hormone is secreted
  • if maximum set point is exceeded then hormone production is halted
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13
Q

Positive Feedback loop

A
  • As blood concentrations of hormones increase, the response of the effector organ stimulates further secretion
  • Oxytocin:
    • hormone that controls the progression of childbirth
    • operates via positive feedback
    • stimulates the uterus to contract which stimulates further secretion of oxytocin
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14
Q

Pituitary Gland

A
  • Hypophysis: Undergrowth from the brain
  • secretes at least nine major hormones
  • sits inferior to the brain in the hypophyseal fossa of cella turcica of spehnoid bone
  • resembles a golf club
    • gland forms head of club and shaft is called infundibulum.
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15
Q

Infundibulum

A
  • forms shaft of pituitary gland
  • connects superiorly to a part of the hypothalamus called tuber cinereum
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16
Q

Two basic divisions of pituitary gland

A
  1. adenohypophysis: Anterior. Composed of grandular tissue
  2. Neurohypophysis: posterior. composed of neural tissue and part of the brain
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17
Q

Adenohypophysis

A
  • Anterior
  • coposed of grandular tissue
  • Subdivisions:
    • pars distalis (anterior lobe): most anterior part
    • pars intermedia: posterior to pars distalis
    • pars tuberalis: wraps around infundibulum like a tube
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18
Q

Neurohypophysis

A
  • Posterior division of pituitary gland
  • composed of neural tissue and part of the brain
  • subdivisions
    • pars nervosa (posterior lobe): most inferior
    • infundibular stalk: middle
    • median eminence: cone shaped, part of hypothalamus
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19
Q

Superior Hypophyseal Artery

A
  • A branch of the internal carotid artery through which the artierial blood supplies the hypophysis
  • supplies the entire adenohypophysis and infundibulum
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20
Q

Inferior hypophyseal artery

A
  • branch of the internal carotid artery
  • supplies the pars nervosa
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21
Q

Somatotrophic Cells

A
  • The most abundant cells in the pars distalis (adenohypophysis)
  • secrete Growth Hormone (GH) aka Somatotrophic Hormone (SH) or Somatotrophin
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22
Q

Growth Hormone

A
  • AKA Somatotrophic Hormone (SH)
  • AKA Somatotrophin
  • Found in Somatotrophic Cells of Pars Distalis (adenohypophyis)
  • Stimulates growth of the entire body
    • stimulates body cells to increase protein production
    • stimulates growth of epiphyseal plates of skeleton
    • Stimulates directly
    • Also stimulates indirectly by signaling liver to secrete insulin-like growth factor-1
23
Q

Mamotrophic Cells

A
  • In pars distalis of the adenohypophysis
  • mamm=breasts
  • secrete prolactin, a hormone that stimulates manufacture of breast milk
24
Q

Prolactin

A
  • a hormone that stimulates manufacture of breast milk
  • Found in mamotropic cells
25
Q

Thyrotrophic Cells

A
  • In pars distalis of the adenohypophysis
  • secrete thyroid-stimulating hormone (TSH), which prompts the thyroid gland to secrete its own hormone
26
Q

thyroid-stimulating hormone (TSH)

A
  • secrete thyroid-stimulating hormone (TSH), which prompts the thyroid gland to secrete its own hormone
  • found in thyrotropic cells
27
Q

Corticotropic cells

A
  • In pars distalis of the adenohypophysis
  • secrete at least two hormones that are split from a common parent molecule
    • **adrenocorticotropic hormone **(ACTH) stimulates the adrenal cortex to secrete hormones that help people cope with stress
    • **melanocyte-stimulating hormone **(MSH) darkens skin pigmentation by stimulating melanocytes to produce melanin
28
Q

adrenocorticotropic hormone (ACTH)

A
  • stimulates the adrenal cortex to secrete hormones that help people cope with stress
  • Comes from corticotropic cells
29
Q

melanocyte-stimulating hormone (MSH)

A
  • darkens skin pigmentation by stimulating melanocytes to produce melanin
  • comes from corticotropic cells
30
Q

Gonadotropic Cells

A
  • In pars distalis of the adenohypophysis
  • secrete **Gonadotropins **that act on the gonads, stimulating maturation of the sex cells and inducing the secretion of sex hormones
    • follicle stimulating hormone (FSH)
    • Luteinizing hormone
31
Q

Gonadotropins

A
  • act on the gonads, stimulating maturation of the sex cells and inducing the secretion of sex hormones
  • follicle stimulating hormone (FSH)
  • Luteinizing hormone
32
Q

Tropic Hormones

A
  • Hormones of the pars distalis that regulate the secretion of hormones by other endocrine glands
  • TSH, ACTH, FSH, LH
33
Q

3 categories of pars distalis cell tissue

A
  • when dyed and viewed by light microscopy
  1. Acidophils: stain with acidic stains
    • somatotrophic cells
    • mammotropic cells
  2. Basophils: stain with basic stains
    • thyrotropic
    • corticotropic
    • gonadotropic
  3. Chromophobes: stain poorly
    • immature cells or cells depleted of hormones
34
Q

Releasing Hormones

(releasing factors)

A
  • peptide hormones of the hypothalamus that secrete to control the secretion of hormones in the adenohypophysis
35
Q

Inhibiting hormones

A
  • hormones of the hypothalamus that turn off the secretion of adenohypophysis hormones when necessary
36
Q

How the releasing hormones of hypothalamus signal secretion of adenohypophyseal hormones

A
  • hormones are secreted from the hypothalamic neurons they enter in the median eminence of a primary capillary plexus
  • Then they travel inferiorly in hypophyseal portal veins to a **second capillary plexus **in the pars distalis
  • Leaving this plexus the releasing hormones attach to adenohypophyseal cells and stimulate them to secrete hormones.
37
Q

Hypothalamic-hypophyseal tract

A
  • a group of axons in the neurohypophysis that arise from neuron cell bodies
38
Q

Antidiuretic Hormone

(ADH)

A
  • Made in the neurons of the supraoptic nucleus in the neurohypophysis
  • AKA Vasopressin (vessel constrictor)
  • targets collecting ducts and distal tubules in the kidneys
  • Helps body retain as much fluid as possible when thirst (dehydration) or fluid loss (severe bleeding) occurs
39
Q

Oxytocin

A
  • produced in the paraventricular nucleus in the neurohypophysis
  • induces contraction of the smooth musculature of reproductive organs in both males and females
  • signals uterus to contract, expelling infant during child birth
40
Q

Thyroid Gland

A
  • butterfly shaped
  • anterior neck on the trachea, just inferior to the larynx
  • has two lateral lobes (wings) connected by a median bridge (isthmus)
  • largest purely endocrine gland in the body
  • Produces two hormones
    • Thyroid Hormone
    • Calcitonin
41
Q

Thyroid hormone

(TH)

A
  • Main function is to increase the basal metabolic rate
  • The higher your TH secretion the higher your activity level and warmth
  • the lower your TH secretion you may feel sluggish and cold
42
Q

Calcitonin

A
  • secreted by parafollicular cells of the thyroid
  • a protein hormone secreted when blood calcium levels are high to lower levels
  • mostly during childhood. no demonstratable function in adults

*PTH and calcitonin have opposite or antagonistic effects*

43
Q

Parathyroid Glands

A
  • small yellow-brown glands on the posterior surface of the thyroid gland
  • remain distinct surrounded by their own connective tissue capsules
  • Most people have 2 pair, as many as 8 have been reported
44
Q

Parathyroid Hormone

PTH

A
  • AKA Parathormone
  • a small protein hormone that increases the blood concentration of Ca2+ whenever it falls below some threshold value
  • Raises blood calcium by:
    1. stimulating osteoclasts to release more Ca2+ from bone
    2. decreasing secretion of Ca2+ by the kidneys
    3. activating vitamin D which stimulates the uptake of Ca2+ by intestine
  • Essential to life. W/o it would lead to lethal neuromuscular disorders
45
Q
A
46
Q

Goiters

A

a swelling of the neck resulting from enlargement of the thyroid gland.

47
Q

Cortisol

(Glucocorticoids)

A
  • Helps the body deal with stressful situations such as:
    • fasting
    • anxiety
    • trauma
    • crowding
    • and infection
  • Keeps glucose levels high enough to support brain’s activities while forcing other cells to switch energy sources to amino acids and fats
48
Q

Aldosterone

(main mineralocorticoid)

A
  • secreted by the zona glomerulosa in response to:
    • blood volume
    • blood pressure
  • Released in severe hemmorhage
49
Q

Pineal Gland

A
  • Small, pine cone shaped structure at the end of a short stalk on the roof of the diencephalon
  • Produces melatonin
50
Q

Thymus

A
  • In the lower neck, anterior thorax
  • Thymic hormones
    • family of peptide molecules
51
Q

Gonads

A
  • testes and ovaries
  • main source of steroid sex hormones
  • Testes produce androgens
    • primarily testosterone
      • maintains reproductive organs and promoted formation of sperm
  • Ovaries produce
    • estrogen
      • maintain reproductive organs
    • progesterone
      • signals uterus to prepare for pregnancy
52
Q

Adrenal Cortex

A
  • 3 layers
  • secretes corticosteroids
    • ​mineralocorticoid
      • ​aldosterone
    • glucocorticoids
      • ​cortisol
53
Q

Adrenal Medulla

A
  • secrete
    • epinephrine
    • norepinephrine
54
Q

Pancreas

A
  • Secretes
    • Glucagon
      • liver cells release glucose from storage
    • Insulin
      • signals most cells to take up glucose from blood and to store glucose in liver to lower blood sugar levels
    • somatostatin
      • inhibits secretion of glucagon and insulin
    • pancreatic polypeptide
      • inhibits exocrine activity in pancreas

Anatomy (25 decks)

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