Mam Phys II Exam 3

3 classes of hormones.

-proteins/peptides

-steroids

-amines

T or F

Steroid hormones tend to bind to intracellular or cytoplasmic receptors.

True

T or F

No matter the mechanism of action of a hormone, the end result of a hormone binding to a receptor is a change in the protein activity of a cell.

True

Which of these hormone is released by the posterior pituitary?

a) hGH

b) ACTH

c) TSH

d) ADH

e) PRL

d) ADH

Which of these is a metabolic effect of an increase in growth hormone?

a) increase in protein synthesis only

b) decrease in fat utilization only

c) increase in carbohydrate utilization only

d) increase in protein synthesis, decrease fat utilization, and increase carbohydrate utilization

a) increase in protein synthesis only

A major constituent of colloid in the follicles of the thyroid gland is a large glycoprotein called ____________.

thyroglobulin

T or F

Thyroxine and triiodothyronine are bound to a plasma protein for transport through the blood.

True

Which hormones are derived from cholesterol?

mineralocorticoids, glucocorticoids, and sex hormones only

Which organ secretes insulin and glucagon?

pancreas

Which hormone helps reinforce the positive feedback loop during labor that results in the delivery of a baby?

oxytocin

released by the axon terminals of neurons into synaptic junctions and locally to control nerve cell function

Neurotransmitters

released by glands or specialized cells into the bloodstream and influences cells at another location

Endocrine Hormones

secreted by neurons into bloodstream and influence the function of cells at another location; ex: ADH, oxytocin, hypophysiotropic hormones

Neuroendocrine Hormones

secreted by cells into the ECF and affect neighboring cells of a different type

Paracrines

secreted by cells into the ECF and affect the same cells that produced them

Autocrines

peptides secreted by cells into the ECF and can function as autocrines, paracrines, or endocrine hormones

Cytokines

Most hormone are _______.

proteins/polypeptides

Peptide hormone size ranges from ___ AA (TRH) to ___ AA (GH, prolactin).

3 to 200

Peptide hormones are produced where and as what?

produced at rough ER as preprohormones

Peptide hormones are cleaved where and become what?

cleaved at ER to become prohormones

How are peptide hormones secreted?

exocytosis

Stimulus for peptide hormone secretion.

calcium ion influx or cAMP

T or F

Peptide hormones are water soluble.

True

Examples of protein/polypeptide hormones.

insulin, glucagon, parathyroid hormone

What are steroids secreted by?

adrenal cortex, ovaries, testes, placenta

Steroids are made from ________.

Cholesterol

Steroids are _____ soluble.

lipid

T or F

Steroids diffuse directly through cell membrane and enter bloodstream to be bound and carried by a plasma proteins.

rue

Very little ______ storage, but very large ________ stores.

steroid, cholesterol

Example of steroids

cortisol, aldosterone, estrogen, progesterone, testosterone

Steroids consist of

3 cyclohexyl rings and 1 cylopentyl ring (4 ring structure)

Amines are secreted from

thyroid and adrenal medulla

Amines are derived from

tyrosine (semi-essential amino acid)

Tyrosine is synthesized from

phenylalanine (essential amino acid)

Thyroid hormones are bound to

thyroglobulin

Where is thyroglobulin stored

thyroid

Secretion of thyroid hormones involves

splitting amines off thyroglobulin and releasing them into the bloodstream.

What do thyroid hormones often bind to?

plasma proteins (thyroxin-binding globulin)

Which amines are formed in adrenal medulla?

norepinephrine and epinephrine

Epinephrine and norepinephrine released upon

neural stimulation

Examples of amines.

Epinephrine, norepinephrine, thyroxine (T4), triiodothyronine (T3)

Norepinephrine and epinephrine have full effect in _____, thyroxine or growth hormone may take _____ for full effects to be shown.

seconds, months

Hormone concentration in blood is ____.

small

T or F

Hormones bound to plasma proteins are cleared more slowly than those which are not.

True

Half life of adrenal steroids

~20 - 100 minutes

Half life of thyroid hormone

~1 - 6 days

The amount of time a hormone stays in the blood is dependent on?

the rare of secretion and the rate of removal

How are hormones cleared from plasma?

1. metabolic destruction by the tissues

2. binding with the tissues

3. excretion by the liver into bile

4. excretion by the kidneys into urine

What is the affected variable in the negative feedback control of hormone levels?

the degree of activity of the target tissue

Examples of positive feedback control of hormone secretion

-LH triggers ovulation in the menstrual cycle

-oxytocin during labor

Basic mechanism of hormone action

hormone must bind to a receptor to cause anything to happen; no receptor = no response

T or F

The only way that a cell can respond to a hormone is if that cell has a receptor for that hormone.

True

3 places where receptors can be found in or on a cell

1. integral cell membrane protein (protein, peptide, and catecholamine hormones bind to these)

2. cytoplasmic (steroid hormones bind to these)

3. nucleic (thyroid hormone bind to these)

How are the number of hormone receptors regulated? (two ways)

1. up-regulation: binding of hormone results in an increase in the number of receptors

2. down-regulation: binding of hormone results in a decrease in the number of receptors

Down regulation can occur as a result of

1. inactivation of some of the receptor molecules

2. inactivation of some of the intracellular protein signaling molecules

3. temporary sequestration of the receptor inside the cell

4. destruction of receptors by lysosome after internalization

5. decreased production of receptor