Chapter 14: Chemical signals

hormone

chemical signal secreted into body fluids; does not need a lot to bring a response

target cells

cells that are equipped to response to hormone; in order to respond to chemical signal must have a receptor

• gland cells

• neurosecretory cells

• epithelial cells

what glands secrete hormones

exocrine glands

glands that are ducted and releases products that are not hormones; products such as Na bicarbonate and various digestive enzymes

endocrine glands

glands that are ductless and will release hormones in the IF → capillaries → throughout the body

lipid soluble hormones

• steroids from cholesterol

• thyroid hormones (T3/T4)

1. can act in small concentrations

2. same hormones can have different effects on different animals

3. same hormone can have different targets and responses in the same mammal

4. have antagonistic pairs

what are the four characteristics of hormones

• signal binds receptor → nucleus

• binds to control region of genes

• can activate or inactivate genes

• signal molecule → long lived

• cellular response → slow

• duration of response → long term

characteristics of non-water soluble hormones (thyroxine/steroids)

• signal transducers are in the membrane which change activity of proteins in cells

• signal molecules are short lived

• cell response is rapid

characteristic of water-soluble hormones

mRNA → cytosol → ribosome → specific protein

activation of non-water soluble hormones

1. receptors outside of plasma membrane have a binding site for the hormone outside (which is transmembrane)

how do water soluble hormones pass plasma membrane

1. hormone passes through plasma membrane

2. hormone binds to receptor = activation

3. activated receptor binds to regulatory sequence in gene

   1. activation/inhibition

how do non-water soluble hormones bind to receptor in cell

ion-channel-linked receptor

a type of membrane receptor that are gated (neurons)

enzyme-linked receptor

the type of membrane receptor where the receptor functions directly as an enzyme or is closely linked to an enzyme

• tends to be protein kinases

• cellular response due to activation or deactivation of proteins in the cell

tyrosine kinase receptor

an enzyme-linked receptor that is a monomer and separates when inactive, as it needs two hormones to bind to the receptor, making two monomers sticky

• uses MAPK1 → MAPK2 → MAPK3 pathway

1. signal molecules bind and two receptors assemble into a dimer

2. activation of protein kinases. and autophosphorylation of receptor

3. transduction and cellular responses

process of tyrosine kinase receptor

G-protein linked receptors

a type of membrane receptor that involves a relay protein between the receptor and the effector

• the G-protein is a trimer

• binding of GDP = inactive

• binding of GTP = active

• one subunit of activate G-protein interacts with effector protein (enzyme

characteristic of a G-protein linked receptor

acts on the secondary messenger on the cytoplasmic side of the membrane

what does the effector do in a G-protein linked

effector

in a G-protein linked receptor pathway that is membrane-bound protein (usually an enzyme/ion channel) actiated by G-protein subunit/binding to receptor

e.g) Adenylyl cyclase

receptor

a specialized protein molecule located on the surface of a cell, in the cytoplasm, or in the nucleus that binds to specific signaling molecules (ligands) such as hormones, neurotransmitters, or drugs

cAMP phosphodiesterase

a cyclic enzyme where the gene is always active

• target is cAMP which breaks down cAMP → AMP

• limited number

reception

the first stage of a signal transduction pathway where the hormone will bind to the receptor

transduction

the second stage of the signal transduction pathway that creates the amplification of the signal (phosphorylation cascade)

response

the third stage of the signal transduction pathway which is the end result after the amplification of the signal

second messenger

what the STP generates on the cytoplasmic side of the membrane which relay signals from receptors to effector proteins within the cytoplasm

• often cAMP

• short term responses

• signal amplification

cAMP dependent protein kinases

protein kinases that cAMP activates which will interact with proteins in cell leading to cascade of events changing the behavior of the cell

epinephrine binds to G-linked receptor → inactive G-protein → active G-protein → inactive adenylyl cyclase → active → ATP → cAMP → inactive protein kinase A → active → inactive phosphorylase kinase → active → inactive glycogen phosphorylase → active → glycogen → glucose-1-phosphate

STP pathway of epinephrine

1. enters target cells

2. binds to intracellular receptor

3. alters gene expression

4. slow/long-lived

summary of steroids (non water soluble)

1. follows a signal transduction pathway that is transmembrane

2. receptor → relay → effector → second messenger → phosphorylation cascade

3. regulates cytoplasmic enzymes/proteins

4. fast/short lived

5. transcription factors → slow/long lived

Summary of amino acids/ peptides

neurosecretory cells

cells that produce hormones that are stored in the posterior pituitary gland/ produce releasing or inhibiting hormones that control the release of hormones from the anterior pituitary gland

• diffsed → IF → capillaries → body

releasing/inhibiting factors

hormones when the hypothalamus releases own hormones it affects the release from the anterior pituitary gland

hypophyseal portal veins

vessels that are ordered on both sides by capillaries and where the hormones are released into

tropic hormones

hormones that control the realse of hormones from another gland essentially hormones controlling hormones

gigantism

the conditions which is the overproduction of growth hormones in children and will increase the growth zones near the heads of the femur which are cartilage building cells

dwarfism

the conditions that is the underproduction of growth hormone in children where the cartilage will ossify making bones short; however with recombinant DNA technology human growth hormones can be inserted into children

acromegaly

the condition which is the overproduction of growth hormone in adults; essentially stimulates cartilage growth

type I diabetes

a condition which are insulin-dependent (autoimmune) since they have low insulin production

type II diabetes

a condition where it have lower responsiveness of target cells and are not insulin dependent; are insulin resistant where they have a mutation in the insulin receptor

glucogenesis

the function in cortisol where it will convert amino acids into glucose

hypothalamus → corticotropin-releasing hormone → ACTH → adrenal cortex → cortisol

pathway in the release of cortisol

secondary sex characteristics

the characters that are different between males and females and are not related to reproduction (e.g: males having lower voices)