Human Biology 2 Exam 1

paracrine chemical signaling

chemical released from cell and has effects on nearby target cell, local communication

autocrine chemical signaling

chemical released from cell and has effect on itself

endocrine chemical signaling

chemical produced by cell, released into bloodstream for wide spread, systemic effects

endocrine glands

ductless glands that release hormones to act on distant target cells

primary endocrine organ

primary function or organ is to produce hormones

secondary endocrine organ

has its own specialized function but also secretes hormones

classification of hormones

amines, lipid derivatives, peptide

amines

derived from tyrosine

examples: thyroid hormone, epinephrine, norepinephrine, dopamine

lipid derivatives

1. steroid hormones: derived from cholesterol

2. eicosanoids: derived from arachidonic acid

peptide hormones

• majority of hormones

• synthesized as prohormones

• stored in secretory vescicles

prohormone

inactive protein, becomes active later when its ready to be used, made in abundance

hormones in the blood

• transport: circulate in the blood either free form or bound to a carrier (hydrophobic hormones need help)

• breakdown of hormones: uptake by target cell and degradation, liver and kidney, urinary excretion

bioavailability

amount of hormone available to exert action on target cell, has potential/ability to bind to its target

half life

the time it takes for concentration of hormone in blood to decrease to 50% its initial concentration

hormone receptors

• proteins

• reactive to one hormone or specific to a group of hormones

• small concentrations of a hormone have a large effect

• undergo structural changes when ligand binds

2 types

1. intracellular receptors

2. plasma membrane receptors

intracellular receptors

• steroid hormones, thyroid hormones

• altered gene expression

• slow acting - once receptor binds, it acts as transcription factor (increases expression of gene they are responsible for binding to) which impacts gene expression

plasma membrane receptors

• peptide hormones, most amines

• fact acting

• altered activity of proteins in cell

G protein coupled receptor (GPCR)

• integral protein with 7 transmembrane spanning domains

G proteins

have 3 subunits: alpha, beta, gamma

alpha is able to bind to GTP and GDP

desensitization

• decreases a cell’s response to hormone

• decrease in number of receptors on plasma membrane

• receptors degraded in lysosomes or proteosomes

sensitization

• increases cell’s response to hormone

• increase in receptor number on plasma membrane

• vesicle fusion of stored receptors with membrane

phosphorylation of receptor

can lead to desensitization or sensitization

anterior pituitary

• cells that release hormones into circulation

• Under the control of hypothalamic hormones (hypophyseal portal system)

posterior pituatary

• axon terminals of neurons whose cell body is in hypothalamus

• neuroendocrine cells

• Release antidiuretic hormone (ADH) and oxytocin (OXT) from posterior lobe

• stores and releases hormones produced by the hypothalamus

Oxytocin

• peptide hormone

• maternal behaviors and love

• stimulus for release:

  • breast - suckling of lactating breast

  • uterus - cervical stretch during labor (positive feedback)

• detected by sensory receptors in breast and uterus

milk let down response

baby suckling, stimulates posterior, causes contraction of milk producing cells, pushes milk out

Antidiuretic Hormone (ADH) / Vasopressin

• peptide hormone

• purpose: kidney to reabsorb water → when we are dehydrated

• stimulus for release:

  • increase in plasma osmolarity

  • detected by osmoreceptors in hypothalamus

• target organ: kidney

• effect: increased water reabsorption

  • put water into blood and then stop producing ADH

hypothalamus releases Growth Hormone Releasing Hormone (GHRH) and Growth Hormone Inhibiting Hormone (GHIH) for anterior pituitary to regulate release of

Growth Hormone

hypothalamus releases Prolactin Inhibiting Hormone (PIH) for anterior pituitary to inhibit release of

Prolactin

hypothalamus releases Thyrotropin Releasing Hormone (TRH) for anterior pituitary to release

Thyroid Stimulating Hormone

hypothalamus releases Corticotropin Releasing Hormone (CRH) for anterior pituitary to release

Adrenocorticotropic Hormone

hypothalamus releases Gonadotropin Releasing Hormone (GnRH) for anterior pituitary to release

Luteinizing hormone (LH) and Folicle Stimulating Hormone (FSH)

5 types of secretory cells

1. somototrophs

2. lactotrophs

3. thyrotrophs

4. Corticotrophs

5. Gonadotrophs

Somototrophs

Growth Hormone

Lactotrophs

prolactin

Thyrotrophs

thyroid stimulating hormone

Corticotrophs

adrenocorticotropic hromone

Gonadotrophs

follicle stimulating hormone (FSH) and Luteinizing Hormone (LH)

Prolactin

• peptide hormone

• involved in breast feeding

• normally prolactin isn’t being released because of PIH

• pregnancy and suckling on breast decrease PIH release and sensory receptors send afferent signal to hypothalamus

• Stimulates growth and development of mammary glands; stimulate milk SYNTHESIS

what does prolactin inhibit

GnRH - FSH and LH not being produced and influence menstrual cycle - stops when not released

hypterprolactinemia

pituitary gland making too much prolactin causing menstrual cycle irregularities

Growth Hormone

• Stimulus for release: has a circadian rhythm with a peak in release in early hours of sleep

• effect on target organs through 2 mechanisms

  • binds to GH receptors on target cell directly

  • stimulates production of insulin like growth factors (IGFs)

    • more potent form of growth factor

  • binds to receptors on target cells indirectly

• effect on target organ: stimulates cell growth and division

excess growth hormone

• before puberty: gigantism

• after puberty: acromegaly

less growth hormone

• before puberty: dwarfism

follicle

• the smallest functional unit of thyroid

• fluid (colloid) filled sphere lined by simple cubodial epithelial cells (follicle cells)

• synthesis of thyroid hormone

parafollicular cells - C cells

• synthesis/release of calcitonin hormone

• in between follicle cells

calcitonin

• released when too much Ca2+ in blood

• inhibit osteoclasts

• increase excretion of Ca2+ by kidney

• prevent absorption of Ca2+ by digestive system

thyroid hormone T4 & T3

• derived from amino acid tyrosine (amine hormone)

• T4: 4 iodine atoms

• T3: 3 iodine atoms

T4

most abundant form of thyroid hormone

T3

body prefers this form to actually use

synthesis of thyroid hormone

1. iodide ions (I-) are transported from blood into follicular cell (TSH dependent)

   1. TSH receptors on thyroid follicular cells which turns on iodide pump

2. iodide ions (I-) converted into iodine atoms (I) by thyroid peroxidase (called activating iodine) then paired with thyroglobulin → get pushed into the colloid

   1. thyroglobulin makes a lot of tyrosine (imagine it being a packet of tyrosine)

3. In the colloid thyroid hormone is made and then brought back into the cell - thyroglobulin has T3 and T4 in it

4. When the body needs the hormone, it brings in chunks of colloid and and fuses with a lysosome to free T3 and T4

5. through diffusion, T4 and T3 enter into capillaries and bind with TBG (carrier protein to help thyroid hormone travel because it doesn’t travel well in the blood by itself)

actions of thyroid hormone

• fast, strong, short increase in rate of cellular respiration → increased production of ATP

• 3 receptor locations within a cell

  • cytoplasmic receptors: storage

  • mitochondria receptors: increase rate of ATP production

  • nucleus: increase gene transcription and act like transcription factor (inc/dec certain proteins being made in the cell)

• specific actions:

  • increased metabolic rate (heat production)

  • increased HR and BP

  • stimulate RBC formation → increase oxygen delivery

  • trigger bone remodeling process

hypothyroidism

• thyroid hormone = increased ATP

  • not having enough means you’re tired

• iodine deficiency

• TRH → TSH → tells thyroid gland to make more thyroid hormone but it can’t because lack of iodine → can’t tell hypothalamus to stop releasing TRH

• TRH and TSH levels high → causes growth of thyroid gland

hyperthyroidism

• most common cause: graves disease

  • antibody activated TSH receptor

  • goiter and increased T4 & T3

• body making protein abnormally → thyroid stimulating antibody

  • binds to TSH receptor → making lots of thyroid hormone and tells hypothalamus to stop releasing TSH but keeps on making more thyroid hormone

parathyroid gland

• 4 small glands on posterior surface of thyroid

• collection of parathyroid principle cells

• secrete parathyroid hormone (PTH) in response to low levels of Ca2+ levels in the blood

• effects:

  • stimulates osteoclasts

  • increased absorption of Ca2+ by kidney

  • stimulates formation of calcitriol (active form of vitamin D) by kidney

adrenal glands

• composed of

  • outer cortex: corticosteroids - makes steroid hormones

  • inner medulla: epinephrine and norepinephrine

layers of outer cortex: corticosteroids (outer to inner)

1. zona glomerulosa

2. zona fasciculata

3. zona reticularis

hormones of adrenal cortex: zona glomerulosa

• mineralcorticoids (hormone class) : regulation of sodium and potassium levels in ECF

• aldosterone (main type of hormone): released in response to low levels of Na+

  • reabsorption of Na+ from urine, seat glands, and salivary glands at the expense of K+

hormones of adrenal cortex: zona fasciculata

• glucocorticoids (hormone class): regulation of carbohydrate levels in ECF, anti-inflammatory properties (reduce activity of immune systems - helps reduce pain)

• cortisol (specific hormone): speed up rate of glucose synthesis and glycogen formation

  • helps regulate glucose and tells body to make new glucose molecules

hormones of adrenal cortex: zona reticularis

• sex hormones → usually make sex hormones

• weak androgens, useful as precursors for the production of estrogen and testosterone by other tissues

• influence muscle mass and sex drive in adult women

hypothalamic pituitary adrenal (HPA) axis

• stress or higher brain centers cause hypothalamus to release CRH → anterior pituitary releases ACTH → enters blood stream and reaches adrenal cortex (zona fasciculata) and stimulates it to release cortisol

• cortisol effects on body:

  • ↑ glucose formation (gluconeogenesis)

  • ↑ fatty acid release

  • ↓ protein synthesis (breaks muscle protein)

  • This provides energy during stress

Chronic stress

• Cortisol stays high for long periods

• Brain receptors become desensitized

• So cortisol can’t shut off CRH properly anymore

  • will keep releasing CRH → ACTH → cortisol

short term stress response

stressful response kicks on cortisol → makes glucose and rebuilding glycogen reserves

long term stress response

starvation

Atrioventricular valves

• tricuspid (right atria and ventricle) and bicuspid/mitral (left atria and ventricle)

• Between the atria and ventricles

Semilunar valves

aortic and pulmonary

heart wall laters (outer to inner)

1. parietal pericardium (faces outer cavity)

2. epicardium

3. myocardium

4. endocardium

cardiomyocytes

• cardiac muscles cells

• striated (because of thick and thing filaments)

• branched at ends

• mono-nucleated

• reduced SR system but extensive T tubule system

• intercalated discs

intercalated discs

specialized, zigzag-shaped junctions connecting individual cardiac muscle cells (cardiomyocytes), crucial for synchronizing heart contractions; where cells come in contacct

• desmosomes (thick proteins holding them together, adhesion proteins) - mechanical couples

• gap junctions - electrical coupling