Jackson Lectures 1

Question 1

• preprohormone is synthesized on ——–; includes extra

Answer 1

ribosomes, amino acids and foldings.

Question 2

• prohormone formed by cleaving

Answer 2

extra amino acids in the RER; packaged into secretory vesicles in the Golgi apparatus.

Question 3

Some cholesterol is produced by de novo synthesis from

Answer 3

acetyl CoA.

Question 4

Cholesterol esterase releases

Answer 4

cholesterol from stores

Question 5

Steroid acute regulatory protein (StAR) facilitates

Answer 5

intracellular transport of cholesterol by binding to cholesterol and transporting it through the watery cytoplasm to the mitochondria where is crosses both outer and inner membranes

Question 6

Cholesterol is converted to steroids by

Answer 6

P450 enzymes in the mitochondria – these are cytochrome P450 enzymes that add –OH or cleave C-C. Steroids shuffled to SER for further enzyme modification

Question 7

Synthesis of steroids is regulated by regulating the

Answer 7

peptide hormone that stimulates their synthesis, the synthesis of steroidogenic enzymes, and/or the number of steroidogenic cells

Question 8

Catecholamines or catecholaminergic hormones are synthesized in the

Answer 8

adrenal medulla and hypothalamus (in neurons or cells derived from neural crest cells)

Question 9

norepinephrine (NE) (noradrenaline) produced in –

Answer 9

adrenal medulla (catecholamine)

Question 10

epinephrine (E) (adrenaline) produced in

Answer 10

adrenal medulla (catecholamine

Question 11

dopamine (DA) - produced in

Answer 11

hypothalamus (catecholamine)

Question 12

catecholamines are common neurotransmitters so other neurons make them, particularly those of the

Answer 12

autonomic nervous system

Question 13

NE, E and DA are

Answer 13

hydrophillic, polar

Question 14

Eicosanoid hormones – group of locally-acting hormones derived from

Answer 14

arachidonic acid.

Question 15

Eicosanoid hormones Are known for

Answer 15

local effects and are responsible for most inflammatory mediators

Question 16

Aspirin inhibits enzymes that produce

Answer 16

prostaglandins

Question 17

Most hormones are secreted in

Answer 17

short bursts with the timing of the bursts controlled by an upstream signal.

Question 18

No hormone is released in between

Answer 18

vesicular release or the next round of steroid synthesis (because they can’t be stored).

Question 19

Some secretion is.

Answer 19

circadian

Question 20

The circadian pattern is typically due to

Answer 20

increases and decreases in pulse frequency, but can also be associated with changes in pulse amplitude.

Question 21

*Patterns of secretion may be controlled by three factors

Answer 21

1. plasma concentrations of a nutrient, e.g. GH and glucose; calcium regulating hormones
2. neural control, e.g. neurons have rhythmic firing pattern; psychological stress responses
3. hormonal control, e.g. GnRH → LH → T; common pattern

Question 22

• carrier or binding proteins are synthesized in the

Answer 22

liver, and the use of carriers affects the availability of hormone

Question 23

• [free hormone] is a function of

Answer 23

[binding protein]

Question 24

• binding proteins also protect the hormone from

Answer 24

degradation and clearance;

Question 25

small hydrophilic hormones can also use

Answer 25

binding proteins to minimize rate of clearance

Question 26

Some degradation of hormones occurs in the blood due the action of circulating

Answer 26

enzymes. Catecholamines and peptides are highly susceptible to enzymatic degradation – rate is related to molecular size and association with binding proteins.

Question 27

• Steroid and thyroid hormones are less susceptible to degradation in the blood due to the fact that they

Answer 27

attach to binding proteins.

Question 28

• Receptors for hydrophilic hormones are on cell surface/in plasma membrane. These hormones are too

Answer 28

large and/or too lipophobic to pass through membrane

Question 29

• ionotropic responses open

Answer 29

ion channels; Ca2+ , Na+ and K+

Question 30

• metabotropic responses alter

Answer 30

cell activity; phosphorylate proteins including second messengers; move things around (receptors, vesicles)

Question 31

• Receptors for lipophilic hormones are

Answer 31

intracellular and/or nuclear (steroid and thyroid hormones)

Question 32

Steriods/thyroid hromone: • Receptor + ligand forms a

Answer 32

DNA-binding protein → regulates transcription

these responses are delayed – protein synthesis takes time

Question 33

there are some membrane receptors for steroid hormones that control

Answer 33

rapid, non-genomic responses

Question 34

• The anterior pituitary gland or adenohypophysis develops from an

Answer 34

outpocketing of the oral ectoderm that pinches off from the roof of the mouth and lies above the palate.

Question 35

Two hormones are released from the posterior pituitary –

Answer 35

oxytocin and vasopressin

Question 36

Oxy and vaso are synthesized in the neuronal cell bodies in the

Answer 36

supraoptic and paraventricular nuclei (see green neurons in Fig 11.13 above), and secretory vesicles are stored in the axon terminals within the posterior pituitary.

Question 37

• Oxytocin stimulates

Answer 37

smooth muscle contraction- one of the few things that involves positive feedback
•

Question 38

Vasopressin (or antidiuretic hormone) has actions in the

Answer 38

kidney and blood vessels to regulate blood pressure.

Question 39

The adenohypophysis is NOT an extension of the hypothalamus, but it is regulated by

Answer 39

hormones secreted by hypothalamic neurons

Question 40

Hypothalamic neurons secrete

Answer 40

hypophysiotropic (or releasing) hormones; hypophysiotropic hormones are typically named for the pituitary hormone(s) they regulate.

Question 41

Hypothalamic neurons: axon terminals lie in the

Answer 41

median eminence; at the base of the median eminence are portal blood vessels/capillaries

Question 42

Some things to remember about hypophysiotropic hormones

Answer 42

• often found elsewhere in the nervous system; they’re not all peptides!
• the hypothalmo-pituitary portion of the endocrine system is often referred to as the neuroendocrine system; hypothalamus + pituitary + target = an axis
• the complexity of the system provides multiple control sites, and permits amplification of the initial signal

Question 43

Anterior pituitary secretes at least eight hormones

Answer 43

follicle stimulating hormone (FSH)

2. luteinizing hormone (LH)
3. growth hormone (GH) (somatotropin)
4. thyroid stimulating hormone (TSH or thyrotropin)
5. prolactin (PRL)
6. adrenocorticotropic hormone (ACTH or corticotropin)
   7 and 8. β - lipotropin and β- endorphin which are products of the pro-opiomelanocortin (POMC) gene. POMC is a precursor polypeptide synthesized in corticotrophs that is cleaved to yield multiple peptides with varied actions and target tissues. One of those situations – ACTH released, you get these.

Question 44

7 and 8. β - lipotropin and β- endorphin which are products of the

Answer 44

pro-opiomelanocortin (POMC) gene.

Question 45

. POMC is a precursor polypeptide synthesized in

Answer 45

corticotrophs that is cleaved to yield multiple peptides with varied actions and target tissues. One of those situations – ACTH released, you get these.

Question 46

o Long-loop negative feedback is

Answer 46

self-regulation by product/hormone of ultimate target tissue, e.g. cortisol and ACTH/CRH

Question 47

o Short-loop negative feedback occurs when the hormone from

Answer 47

2nd gland in the axis affects the action of the 1st gland, e.g. LH and GnRH

Question 48

Thyroid synth: all the words!!!

Answer 48

1. Iodide is transported across the basal side of the follicle cells via a Na+ / I- transporter. This is called iodide trapping, and is really only found in the Thyroid. It has to come from diet because body cannot make iodide.
2. Iodide diffuses down its concentration gradient across the apical membrane into the colloid of the follicle. Pendrin is the protein transporter that helps get I- into colloid (Na/I- transporter).
3. The follicle cells also synthesize a large, tyrosine-rich protein called thyroglobulin (TG), and the enzyme thyroid peroxidase. Both proteins are exocytosed across the apical membrane into the colloid.
4. In the colloid (which is extracellular fluid), iodide is oxidized by thyroid peroxidase, and linked to thyroglobulin. Binding I- to TG maintains the concentration gradient needed in step 2 to continuously sequester I- in the colloid. Iodinating tyrosine residues on TG. Can have one or two iodides attached to TG to have di-iodoTG
   If one I- is added to a tyrosine residue the resultant molecule is monoiodotyrosine (MIT); iodinating two sites on a tyrosine produces diiodotyrosine (DIT).
5. DITs combine with either other DITs to form tetra-iodothyronine (T4, or thyroxine), or an MIT to form tri-iodothyronine (T3). T3 and T4 remain attached to TG, and are stored in the colloid. T2 is not energetically favorable. This is how they are stored in the colloid and do not diffuse across. This ensures that you always have a store of hormones that can be released when needed. YOU HAVE TO HAVE IODIDE TO SYNTHESIZE thyroid hormone.
6. In response to TSH, droplets of colloid containing TG + T3/T4 are pinocytosed into the follicle cells.
7. The droplet fuses with a lysosome containing enzymes that cleave T3 and T4 from the TG
8. T3 and T4 are released in the cytoplasm by lysosomal hydrolysis.
9. T3 and T4 diffuse into capillaries. Amino acids from the degraded TG are recycled into new TG

Question 49

TH has

Answer 49

negative feedback actions that regulate its own secretion at the level of the hypothalamus and pituitary.

Question 50

Most of T3 and T4 will attach to

Answer 50

binding proteins, some will be free-floating.

Question 51

T3 —– times more active than T4

Answer 51

10