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MCAT Biology > Endocrine system > Flashcards

Endocrine system Flashcards

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1
Q

What are the three types hormones can be?

A

Peptide, steriod or tyrosine derivative

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2
Q

What is a peptide hormone?

A

They have amino acids and often contain carbohydrate portions. They are made in the RER and modified in the golgi apparatus. They exocytois because they are water solouble. THEY ACT ON EFECTOR CELL MEMBRANE RECEPTORS AND INITIATE A CASCADE.

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3
Q

What is a steriod hormone?

A

Derived from cholesterol in the SER and mitochondria. They are hydrophobic so are packaged for transport. They bind to receptor INSIDE the cytosol. Cytosolic receptor and steroid complex moves into nucleus and influences gene expression.

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4
Q

Which hormones are fast acting but short lived?

A

Peptides

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5
Q

Which hormones are slow acting but long lived?

A

Steroids

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6
Q

What are Tyrosine derivative hormones?

A

Lipid soluble hormones derived from the amino acid tyrosine. Produced in cytosol or RER. Catecholamines are an example of tyrosine derivative hormones.

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7
Q

Name some catecholamines?

A

Epinephrine and norepinephrine

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8
Q

What are some differences between normal tyrosine derivative hormones and catecholamines?

A

They are: Water soluble (dissolve in blood). Bind to receptors on cell surface of target cells and activate secondary cascades.

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9
Q

What is the function of the hypothalamus?

A

Master gland of endocrine system. It synthesis and releases both direct and tropic PEPTIDE hormones.

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10
Q

What are direct hormones?

A

Directly stimulate target cells to induce effects, i.e. an organ

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11
Q

What are tropic hormones?

A

Effect endocrine glands as their target

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12
Q

What connects the anterior pituitary to the hypothalamus?

A

The hypothalamic-hypophyseal portal system.

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13
Q

What is a portal system?

A

A capillary bed that drains into another capillary bed through a vein without going through a heart?

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14
Q

What are two other examples of a portal system other than the hhps?

A

Hepatic and renal portal system

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15
Q

How are the posterior pituitary and the hypothalamus connected?

A

With a special group of nerve cells called the neurosecretory cells (produce hormones).

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16
Q

What is the function of the posterior pituitary?

A

Storage of hormones from the hypothalamus.

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17
Q

What hormones are stored in the posterior pituitary (direct)?

A

Vasopression (ADH) and Oxytocin

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18
Q

What is the function of vassopressin?

A

It causes increased water re-absorption in the kidney tubules.

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19
Q

What inhibits ADH?

A

Caffeine and/or alcohol.

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20
Q

What is the function of oxytocin?

A

It causes an increases utrine contractions and it stimulates milk secretion in mammary glands during infant suckling.

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21
Q

What are the hormones that the hypothalamus creates that inhibit or release anterior hormones (tropic)?

A

Growth hormone releasing hormone, somatostain, corticotraopin-releasing hormne, gonadotropin-releasing hormone, dopamine and thyrotropin-releasing hormone.

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22
Q

What are the hormones that are created by the anterior pituitary?

A

Growth hormone, adrenocorticotropic hormone, thyroid-stimulating hormone, luteinizing hormone, follicle stimulating hormone, endorphines and prolactin. (Go Look For The Adenoma PleasE)

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23
Q

Growth Hormone

A

Stimulated by: Growth hormone-releasing hormone

Inhibited by: Somatostatin

–

Stimulates all cells for growth

General trends: ↑ frequency of mitosis, ↑ cell size, ↑ protein synthesis, ↑ fatty acid breakdown and metabolism and ↓ use of glucose by certain cells

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24
Q

Adrenocorticotropic Hormone

A

Stimulated by: Corticotropin-releasing hormone

–

Stimulates the adrenal cortex to synthesize and secrete glucocorticoids and cortical hormones

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25
Q

Thyroid stimulating hormone

A

Stimulated by: Thyrotropin-releasing hormone

Inhibited by: Somatostatin

–

(Tropic peptide) Stimulates the thyroid gland to increase in size, absorb iodine and synthesize/release thyroid hormone (T3 and T4)

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26
Q

Luteinizing Hormone

A

Stimulated by: Gonadotropin-releasing hormone

Inhibited by: Estrogen and progesterone

–

(tropic peptide hormone)

In females: stimulates ovulation and formation of corpus luteum

In males: stimulates interstitial cells of the testes to synthesize testosterone

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27
Q

Follicle Stimulating hormone

A

Stimulated by: Gonadotropin releasing hormone

Inhibited by: estrogen and progesterone

–

(tropic peptide hormone)

in females: causes maturation of ovarian follicles

in males: stimulates maturation of seminiferous tubules for sperm production

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28
Q

Prolactin

A

Stimulated by: Thyrotropin-releasing hormone

Inhibited by: Dopamine

–

(direct peptide hormone)

Promotes lactation in the breasts

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29
Q

Endorphines/Enkephalins

A

(direct peptide hormone)

–

Inhibits the perception of pain

30
Q

Adrenal Cortex

A

Responds to ACTH and synthesizes/secretes corticosteroids

31
Q

Adrenal medulla

A

Secretory cells secrete epinephrine and norepinephrine as part of sympathetic nervous system

32
Q

Glucocorticoids

(i.e. cortisol)

A

(steroid-based hormone)

↑ blood glucose by promoting gluconeogensis, ↓ protein synthesis and ↓ immunological/inflammatory response

Released in response to stress and reg. by neg. feedback loops

33
Q

Cortical Sex Hormones

(i.e. androgens)

A

(steroid hormones)

Responsible for secondary sex characteristics and can produce masculinizing effects in women

34
Q

Mineralocorticoids

(i.e. aldosterone)

A

(steroid based)

Reg. plasma levels of electrolytes and consequently, total extracellular water volume

35
Q

Aldosterone

A

Renin-angiotensin system

Acts in the distal convoluted tubules and collecting tubules of kidnery to increase Na+ and Cl- reabsorption and K+ and H+ secretion

36
Q

How does aldosteronen effect blood plasma level?

A

There is a net gain of plasma particles which increases blood volume and pressure.

37
Q

What are examples of catecholamines?

A

Epinephrine and Norepinephrine

38
Q

Functions of catecholamines?

A
  • Increase the conversion of glycogen to glucose in the liver
  • Increase the rate and strength of heart beat
  • Vasoconstrict blood vessels to internal organs
  • Vasodilate blood vessels of skeletal muscles
39
Q

What hormones does the thyroid gland produce?

A

Thyroxine (T4) and triiodothyronine (T3) and calcitonin.

40
Q

T3and T4

A

(lipid soluble Tyrosine derivative)

Act to increase basal metabolic rate

T3and T4 inhibit TSH and TRH via neg. feedback loop

41
Q

Calcitonin

A

(Peptide hormone)

It decreases blood calcium levels by inhibiting the release of calcium from bone by osteoclasts.

42
Q

Parathyroid hormone

A

(peptide hormone)

Increases blood calcium by stimulating calcium release from bone by osteoclasts.

*based on calcium homeostasis

43
Q

What is calcium homeostasis of blood?

A

9 - 11 mg/100 mL

44
Q

Endocrine

A

Secrete their hormone products directly into the blood

45
Q

Exocrine glands

A

Secrete their products into ducts that lead directly into the external environment.

i.e. digestive enzymes into the duodenum

46
Q

Islets of Langerhans

A

A glandular structure which is composed of alpha, beta and delta cells.

47
Q

Glucagon

A

(alpha cells)

Increases blood glucose by stimulating protein and fat degradation converison of glycogen to glucose and activation of gluconeogensis

48
Q

Somatostatin

A

(delta cells)

ALWAYS INHIBITORY.

49
Q

Insulin

A

(beta cells)

Decreases blood glucose by stimulating uptake of glucose by muscle and adipose cells

50
Q

What types of cells are in testes?

A

Interstitial cells and seminiferous tubules.

51
Q

What is sperm production called and where does it take place?

A

Spermatogensis and in the seminiferous tubules.

52
Q

Where are developed sperm stored?

A

Epididymis

53
Q

What structures do the sperm travel through during ejaculation?

A

Vans deferens to the ejaculatory duct and then the urethra which passes through the penis.

54
Q

SEVEN UP mnemonic for sperm travelling?

A

Seminiferous tubules

Epididymis

Vans deferens

Ejaculatory duct

Nothing

Urethra

Penis

55
Q

Stages of spermatogenesis?

A

Spermatogonium (2n)

↓ mitosis

Primary spermatocyte (2n)

↓ 1st meiotic division

(2) secondary spermatocyte (n)

↓ 2nd meitoic division

(4) spermatids (n)

↓ dif’n and mat’n

sperm cells

56
Q

Stages of Oogenesis?

A

oogonium (2n)

↓ replicated (b/f birth) and arrest at

primary oocyte (2n) (prophase 1 of M1) + polar body

↓ at puberty complete M1 and onset M2

secondary oocyte (n) (metaphase of M2) + PB

↓entry of sperm

Fertilization/completion

(ovum and spermatozoa become zygote)

57
Q

Explain what occurs in Menstrual cycle?

A

FSH + LH promote development of follicle.

Follicle secrete estrogen, increased estrogen towards end of follicular phase stimulates GnRH.

GnRH causes more release of LH + FSH thus spike at day 14. Mature follicle (at day 14) bursts and releases 2nd oocyte -> corpus luteum.

Corpus luteum secretes estrogen + progesterone.

Progesterone causes endometrium to mature.

Estrogen and progesterone cause inhibition of LH, FSH + GnRH.

58
Q

What occurs if not fertilization occurs?

A

Menstruation

Corpus luteum dies, causes decline in progesterone which causes bleeding of endometrium.

Also drop in estrogen (together w/ drop in progesterone means no more inhibition of GnRH)

59
Q

What occurs if fertilization takes place?

A

Fertilization occurs in the fallopian tube b/w 2 layers, zona pellucida and corona radiata.

Sperm enters ovum resulting in a diploid zygote

60
Q

What occurs after fertilization?

A

The zygote begins indeterminate cleavage (no determined end product just mitosis). After five days the embryo implants in uterine endometrium.

Then Blastulation occurs and then determinate cleavage occurs.

61
Q

Blastulation

A

Eight-cell morula develops into blastula (has fluid filled cavity called blastocoel).

62
Q

Determinate cleavage

A

Mitotic division with a restriction in cell fate

63
Q

What occurs to the blastocyst after the implanation?

A

Becomes three layered gastrula via inpocketing (no more blastocoel). Endo, Meso, Ecto.

64
Q

What structures develop from the mesoderm?

A

Musculoskeletal, circulatory, excretory, connective and digestive systems

65
Q

What structures develop from ectoderm?

A

Integument, lens of eyes and nervous system

66
Q

What develops from the endoderm?

A

Epithelial lining of digestive/respiratory tract, parts of liver, pancreas, thyroid and bladder.

67
Q

What occurs after the third week of gastrulation?

A

The gastrula develops into neurula (called neurulation).

68
Q

What does neurulation entail?

A

Notochord induces overlay ecto into neural plate.

Neural plate folds (now called neural folds) and forms neural tube (spinal cord/brain/nervous system).

The neural crest forms peripheral nervous components.

69
Q

What occurs after gestation?

A

After eight weeks it became a fetus and recieves nutrients via umbilical cord.

70
Q
A

MCAT Biology (2 decks)

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