Mcat Biology Lecture 5

Front 1

Exocrine glands

Back 1

release enzymes into external environment through ducts

exocrine glands include:
1. Sudoriferous (sweat)
2. Sebacious (oil)
3. Mucous
4. Digestive

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Endocrine glands

Back 2

release hormones directly into body fluids

effects are (when compared to nervous system):
1. slower (may take seconds to days)
2. less direct
3. longer lasting

generally they alter metabolic activities, regulate growth and development, and guide reproduction

works in conjunction with nervous system (neurons can stimulate endocrine glands to secrete)

Front 3

Receptors

Back 3

all hormones act by binding to protein receptors

highly specific for its hormone

reduction or increase of receptors can regulate hormones

can be on the membrane or inside the cell

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3 types of hormones

Back 4

1. peptide
2. steroid
3. tyrosine derivatives

Front 5

Peptide hormones

Back 5

derived from peptide

large or small and often include carbohydrate portions

manufactured in rough ER as a pre-prohormone, then converted to prohormone in ER lumen, then transported to golgi for packaging into secretory vesicles

water soluble, move freely through blood

difficulty diffusing through cell membrane

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effector

Back 6

the target cell of a hormone. The cell that hormone is meant to affect

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peptide hormone-receptor binding

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instead of diffusing through membrane, peptide hormones bind to membrane-bound receptor. Then the receptor may:
1. act as ion channel
2. activate or deactivate intrinsic membrane proteins that also act as ion channels
3. activate intracellular second messenger (cAMP, cGMP or calmodulin) which activates or deactivates enzymes and/or ion channels and often creates "cascades" that amplify effect of hormone

Front 8

Peptide hormones to know:

Back 8

1. anterior pituitary hormones: FSH, LH, ACTH, hGH, TSH and Prolactin
2. posterior pituitary hormones: ADH and oxytocin
3. parathyroid hormone: PTH
4. pancreatic hormones: glucagon and insulin

Front 9

Steroid hormones

Back 9

derived from and often chemically similar to cholesterol

formed in smooth ER and mitochondria

lipids, require protein transport molecule in order to dissolve in blood stream

lipid soluble, diffuse through cell membrane of effector

once inside cell, combine with receptor in cytosol, which transports it into nucleus and acts a transcription level

typical effect is to increase certain membrane or cellular proteins within effector

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steroid hormones to know:

Back 10

1. glucocorticoids and mineral corticoids of adrenal cortex: cortisol and aldosterone

2. gonadal hormones: estrogen, progesterone, testosterone (estrogen and progesterone are also produced by placenta)

Front 11

Tyrosine derivative hormones

Back 11

thyroid or catecholamine hormones

Formed by enzymes in the cytosol or on the rER. They are lipid soluble and must be carried in blood by plasma protein carriers

Thyroid hormones diffuse through nucleus of effector and bind to receptors inside nucleus. They increase transcription of large numbers of genes in nearly all cells of body.

Catecholamines act on receptors at the membrane, can't diffuse through membrane

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Tyrosine derivative hormones to know:

Back 12

1. T3 (triiodothyronine contains 3 iodine atoms)

2. T4 (thyroxine contains 4 iodine atoms)

3. catecholamines formed in adrenal medulla: epinephrine and norepinephrine (water soluble and dissolve in blood, bind to receptors on effector and act through second messenger system)

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negative feedback

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The control point of feedback is the conduct of the effector, NOT concentration of hormone. So the secreting gland lags behind the effector. The hormone responds to conditions, it doesn't create them.

If there is high blood glucose there is high levels of insulin

Front 14

Anterior Pituitary

Back 14

located in brain, beneath hypothalamus (the hypothalamus controls release of anterior pituitary hormones with releasing and inhibitory hormones)

The anterior pituitary releases 6 peptide hormones:
1. human growth hormone (hGH)
2. adrenocorticotropin (ACTH)
3. thyroid-stimulating hormone (TSH)
4. follicle-stimulating hormone (FSH)
5. leutinizing hormone (LH)
6. prolactin

Front 15

Human growth hormone (hGH)

Back 15

peptide

stimulates growth in almost all cells

increases episodes of mitosis, cell size, rate of protein synthesis, mobilization fat stores, use of fatty acids for energy

decreases use of glucose

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Adrenocorticotropic hormone (ACTH)

Back 16

peptide

stimulates adrenal cortex to release glucocorticoids via second messenger system using cAMP

ACTH is stimulated by stress, glucocorticoids are stress hormones

Front 17

Thyroid-stimulating hormone (TSH)

Back 17

peptide

stimulates thyroid release of T3 and T4 via second messenger system (cAMP)
TSH->Thyroid->T3 + T4->cAMP

TSH increases thyroid cell size, number and rate of secretion of T3 and T4

T3 and T4 concentrations have a negative feedback effect on TSH release, both at anterior pituitary and hypothalamus

Front 18

Prolactin

Back 18

peptide

promotes lactation by breasts (inhibited by progesterone and estrogen)

hypothalamus mostly inhibits release of prolactin

Front 19

Posterior Pituitary (neurohypophysis)

Back 19

composed of support tissue for nerve endings extending from hypothalamus

The hypothalamus synthesizes the small polypeptide hormones:
1. oxytoxin
2. ADH

hormones synthesized in neural cell bodies of hypothalamus and transported down axons to posterior pituitary, where they are released into blood

Front 20

Oxytocin

Back 20

small peptide

increase uterine contractions during pregnancy

causes milk to be ejected from breasts

Front 21

Antidiuretic hormone (ADH or vasopressin)

Back 21

small peptide

causes collecting ducts of kidney to become permeable to water, reducing amount of urine and concentrating urine

since fluids are reabsorbed, blood pressure also increases

coffee and beer are ADH blockers that increase urine volume

Front 22

Adrenal glands

Back 22

located on top of kidneys

separated into adrenal cortex and adrenal medulla

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Adrenal cortex

Back 23

outside portion of adrenal gland

secretes only steroid hormones:
1. mineral corticoids - affect electrolyte balance in blood stream (aldosterone)
2. glucocorticoids - increase blood glucose concentration and increase fat and protein metabolism (cortisol)

Front 24

Aldosterone

Back 24

steroid, mineral corticoid

acts in distal convoluted tubule and collecting duct

increases Na+ and Cl- reabsorption
increases K+ and H+ secretion

creates net gain in particles in plasma, which results in increase in blood pressure (secondary effect)

same effect on sweat, salivary and intestine glands

Front 25

cortisol

Back 25

steroid, glucocorticoid

increases blood glucose levels by stimulating gluconeogenesis in liver (creation of glucose and glycogen, in liver, from amino acids, glycerol and/or lactic acid)

degrades adipose tissue to fatty acids to be used for cellular energy

causes decrease in use of glucose by cells

causes degradation of nonhepatic proteins, decrease of nonhepatic amino acids and as a result increase in liver and plasma proteins and amino acids

stress hormone

Front 26

Catecholamines

Back 26

tyrsoine derivatives synthesized in adrenal medulla

1. epinephrine (adrenaline)
2. norepinephrine (noradrenaline)

vasoconstrictors of most internal organs and skin

vasodilators of skeletal muscles

fight or flight response, stress hormones

Front 27

Thyroid

Back 27

Thyroid hormones:
1. T3 (triiodothyronine)
2. T4 (thyroxine)
3. calcitonin

located along the trachea just in front of larynx

Front 28

T3 & T4

Back 28

similar in effect. both are lipid soluble tyrosine derivatives

T3 (3 iodine atoms)
T4 (4 iodine atoms)

diffuse through lipid bilayer and act in nucleus of cells

increase basal metabolic rate (resting metabolic rate)

secretion is regulated by TSH

Front 29

Calcitonin

Back 29

large peptide released by thyroid gland

slightly decreases blood calcium by decreasing osteoclast activity and number

not necessary for calcium level control

Front 30

Pancreas (islets of langerhans)

Back 30

acts as endocrine and exocrine gland

endocrine peptide hormones, released in blood

1. insulin
2. glucagon

Front 31

Insulin

Back 31

peptide, released by beta-cells of pancreas

released when blood levels of carbohydrates and proteins are high

affects carbohydrate, protein and fat metabolism. net effect is to lower blood glucose levels

causes storage of carbohydrates as glycogen in liver and muscles, fat in adipose tissue and amino acids taken up by cells and made into proteins

binds to membrane receptor and causes cascade reaction, which causes cells (except neurons in brain) to become permeable to glucose, amino acids and intracellular metabolic enzymes are activated and translation and transcription rates are effected

insulin receptor is not glucose carrier

Front 32

Glucagon

Back 32

peptide, released by alpha-cells of pancreas

effects are opposite of insulin

stimulates glycogenolysis (breakdown of glycogen) and gluconeogenesis in liver

acts via second messenger system (cAMP)

high concentrations cause glucagon breakdown of adipose tissue, increasing fatty acid level in blood

net effect is to raise blood glucose levels

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parathyroid

Back 33

4 small parathyroid glands attached to back of thyroid

release parathyroid hormone (PTH)

Front 34

parathyroid hormone (PTH)

Back 34

peptide, increases blood calcium

increases osteocyte absorption of calcium and phosphate from bone, stimulates proliferation of osteoclasts

increases renal calcium reabsorption and renal phosphate excretion

increase calcium and phosphate uptake from gut by increasing renal production of steroid DOHCC (derived from vitamin D)

PTH secretion is tfbhs ssxregulated by calcium ion plasma concentration parathyroid glands shrink and grow accordingly

Front 35

Non-steroid reproductive hormones

Back 35

peptides

1. FSH
2. LH
3. HCG

Front 36

what are the male gonads called?

Back 36

the testes

Front 37

What occurs in the seminiferous tubules?

Back 37

it is where production of sperm occurs

seminiferous tubules are in the testes

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What's the order of sperm formation?

Back 38

Spermatogonia -> spermatocyte -> spermatid -> spermatozoa

Front 39

Spermatogonia

Back 39

located in seminiferous tubules

Spermatogonia arise from epithelial tissue to become spermatocytes, spermatids and then spermatozoa

Front 40

Sertoli cells

Back 40

surround and nurture spermatocyte and spematids

stimulated by FSH.

Front 41

Testosterone

Back 41

released by leydig cells, located in interstitium between tubules, when stimulated by LH

primary androgen (male sex hormone), stimulates germ cells to become sperm. responsible for development of secondary sex characteristics (pubic hair, enlargement of larynx, growth of penis and seminal vesicles)

LH -> leydig cell stimulation -> release of testosterone

Front 42

Spermatozoon

Back 42

no cytoplasm

1. head (nuclear material and lysosome-like enzymes)
2. midpiece (mitochondria)
3. tail (locomotion)

Front 43

Epididymus

Back 43

location where spermatozoon matures

Front 44

Vas deferens

Back 44

upon ejaculation, path through which spematozoa are propelled

Front 45

Semen

Back 45

complete mixture of spermatozoa and fluid that leaves penis upon ejaculation

composed of fluid from seminal vesicles, prostate and bulbourethral glands (Cowper's glands)

Front 46

What stage are the eggs of a female frozen?

Back 46

All eggs of female are arrested as primary oocytes at birth.

Becomes a secondary oocyte upon ovulation

Front 47

Zona pellucida

Back 47

viscous substance secreted by granulosa cells around the egg. The structure is called a primary follicle.

Front 48

Estradiol

Back 48

type of estrogen. Steroid hormone.

upon stimulation by LH, theca cells secrete androgen which is converted to estradiol by granulosa cells in presence of FSH and secreted into blood

prepares uterine wall for pregnancy

inhibits LH secretion by anterior pituitary except LH surge just before ovulation

Front 49

Ovulation

Back 49

bursting of follicle, releasing egg. Caused by luteal surge.

Front 50

luteal surge

Back 50

prior to ovulation, estradiol level rises rapidly, causing a dramatic increase in LH secretion

results from positive feedback loop of rising estrogen levels which increase LH levels, which increase estrogen levels...

causes the follicle to burst (ovulation), releasing the egg (secondary oocyte) into body cavity

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Fallopian (uterine) tube or oviduct

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where egg is swept into after ovulation, by fimbriae

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Corpus luteum

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the remaining portion of follicle left behind after ovulation

secretes estradiol and progesterone throughout pregnancy, or in case of no pregnancy, for 2 weeks until corpus luteum degrades into corpus albicans

Front 53

Corpus albicans

Back 53

degraded corpus luteum after 2 weeks

no pregnancy

Front 54

6 steps of ovulation

Back 54

1. primary oocyte within follicle
2. growing follicle consists of theca cells surrounding granulosa cells which surround the zona pellucida and oocyte
3. secondary (graffian) follicle
4. ovulation: follicle ruptures, releasing secondary oocyte
5. corpus luteum develops from remnants of follicle
6. corpus luteum degenerates to corpus albicans if not fertilization of egg

Front 55

Menstrual cycle

Back 55

repeats itself every 28 days after puberty, unless pregnancy occurs

several oocytes may begin ovulation process, but only one completes the development to ovulation

3 phases:
1. follicular phase
2. luteal phase
3. flow

Front 56

follicular phase

Back 56

begins with development of follicle and ends at ovulation

Front 57

luteal phase

Back 57

begins with ovulation and ends with degeneration of corpus luteum into corpus albicans

Front 58

flow

Back 58

shedding of uterine lining lasting ~5 days

Front 59

ovum

Back 59

once sperm nucleus enters cytoplasm of oocyte and cortical reaction occurs, occyte goes through second meiotic division to form an ovum and releases a second polar body

Front 60

Fertilization

Back 60

occurs when nuclei of ovum and sperm fuse to form zygote

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cleavage

Back 61

begins while zygote is still in fallopian tube

goes through various cycles of mitosis

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Morula

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when zygote comprises of 8 or more cells

at this stage, the embryo doesn't grow during cleavage

1st 8 cells are equivalent in size, shape and are totipotent

Front 63

blastocyst

Back 63

hollow fluid-filled ball after 4 days of dividing post morula phase

lodges in uterus (implantation)

made up of embryonic stem cells

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implantation

Back 64

The lodging of the blastocyst in the uterus that occurs in the 5th - 7th day after ovulation

female is said to be pregnant

Front 65

human chorionic gonadotropin (HCG)

Back 65

peptide hormone

secreted by egg upon implantation

prevents degeneration of corpus luteum

maintains secretion of estrogen and progesterone

HGC in blood and urine of mother, sign of pregnancy

Front 66

Placenta

Back 66

formed from tissue of egg and mother

takes over job of hormone secretion

reaches full development by end of 1st trimester

begins secreting its own estrogen and progesterone while lowering its secretion of HCG

Front 67

Determination

Back 67

process where cell becomes committed to a specialized developmental path (this happens after 8-cell stage)

cells become determined to give rise to specific tissue early one, no longer stem cells

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Differentiation

Back 68

specialization that occurs at end of development forming a specialized tissue cell

Front 69

gastrula

Back 69

formation occurs in 2nd week after fertilization

Front 70

gastrulation

Back 70

process of gastrula formation

3 primary germ layers are formed:
1. ectoderm
2. mesoderm
3. endoderm

Front 71

ectoderm

Back 71

develop into outer coverings of body

outer layers of skin, nails, tooth enamel and into cells of nervous system and sense organs

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mesoderm

Back 72

everything between ectoderm and endoderm

between inner and outer covering of body

skeleton, muscles, blood vessels, heart, blood, gonads, kidneys, dermis of skin

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endoderm

Back 73

develop into lining of digestive and respiratory tract, liver, pancreas, thymus, thyroid

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neurula

Back 74

3rd week gastrula forms neurula

Front 75

neurulation

Back 75

process of neurula formation

In neurulation, notochord (mesoderm) induces overlying ectoderm to thicken and form neural plate. the notochord eventually degenerates, and a neural tube forms from the neural plate to become the spinal cord, brain, and most of the nervous system.

Front 76

notochord induction

Back 76

made from mesoderm

induces ectoderm to thicken and form neural plate


eventually degenerates, while neural tube forms from neural plate to become spinal cord, brain and nervous system

induction occurs when one cell type affects the direction of differentiation of another cell type

Front 77

Apoptosis

Back 77

programmed cell death

part of normal development

essential for development of nervous system, operation of immune system and destruction of tissue between fingers and toes

damaged cells may undergo this process as well, failure to do may result in cancer

regulated by protein activity and not transcription or translation