Chapter 18

Question 1

direct communication

Answer 1

two cells of the same type, in contact with each other, exchange ions and molecules between gap junction

Question 2

Examples of direct communication

Answer 2

cilliary movement, contraction of cardiac muscles, propagation of action potential

Question 3

Paracrine communication

Answer 3

“local”, chemical messengers transfer info from cell to cell within a single tissue. Primary effects occur within the tissue of origin. It is acting as a HORMONE when it has a secondary effect in other tissues beside the original

Question 4

Example of Paracrine communication

Answer 4

prostaglandis, various growth factors

Question 5

Hormones

Answer 5

chemical messengers transported in the blood stream to alter activities in cells in another tissue; effects substance outside its tissue of origin

Question 6

Target cells

Answer 6

cells with specialized receptors for specific hormones that reads it message and alters its activity accordingly

Question 7

5 Functions of a hormone

Answer 7

1. stimulate enzyme or protein synthesis
2. alter transcription or translation to increase or decrease rate of protein & enzyme synthesis
3. turn on or off channel or membrane enzyme by altering shape
4. alter cellular activities of several tissues at the same time
5. coordinate cell, tissue & organ activities on a long term basis

Question 8

Synaptic Communication

4 facts

Answer 8

1. chemical communication using neurotransmitters across synaptic clefts (not in blood stream)
2. target cells are close to the synapse and have specific receptors
3. carries high speed messages which are quick/short lived (adrenaline)
4. crisis management (fight or flight)

Question 9

3 Classes of Hormones

Answer 9

Amino Acid Derivatives
Peptide
lipid derivatives

Question 10

amino acid derivatives

Answer 10

• small, related to amino acids
• thyroid hormone and CATECHOLAMINES (E, NE & DOPAMINE) are derived from the amino acid tyrosine
• melatonin derived from the amino acid tryptophan

Question 11

peptides

Answer 11

• THYROID stimulating hormone, LH and FSH are glycol proteins that consist of long chains of amino acids
• all hormones from the: hypothalamus, heart, digestive tract, thymus, pancreas and posterior pituitary gland are short POLYPEPTIDES

Question 12

lipid derivatives

Answer 12

• eicosanoids have paracrine effects, prostaglandins, leukotrines, thomboxanes and prostacyclins
• steroid hormones resemble cholesterol; secreted by repo glands, adrenal glands and the kidneys

Question 13

Distribution of hormones

Answer 13

pass through bloodstream

circulate freely or bound to transport proteins

Question 14

Freely circulating hormones

Answer 14

*short lived (few minutes - 1 hr)

Question 15

Freely circulating hormones are inactive when (3)

Answer 15

1. diffuse out of blood stream and bind to target cell receptor
2. absorbed and broken down by liver or kidneys
3. enzymes in the cell plasma break it down

Question 16

Why do thyroid and steroid hormones circulate/last longer?

Answer 16

they attach to a transport protein, the blood stream can have a 2 wk supply at any given time, maintaining equilibrium in the blood stream

Question 17

Hormone receptor

4 facts

Answer 17

1. Is a protein molecule to which particular molecules bind strongly
2. can respond to several different hormones
3. different tissues have different combos of receptors
4. presence or absence of specific receptor determines hormonal sensitivity

Question 18

Hormones do not affect all tissues with their receptors the same

Answer 18

cells have dif. combos. of receptors so hormones can have dif. effects on dif. target organs

Question 19

Catecholamines and peptide hormones

Answer 19

NOT lipid soluble and cannot penetrate the plasma membrane, it has to bind to an extracellular receptor to get in

Question 20

Eicosanoids

Answer 20

ARE lipid soluble, they diffuse through membrane to reach receptor proteins on the INNER surface called the INTRAcellular receptor

Question 21

1st and 2ed messengers

Answer 21

hormones that bind to receptors in the plasma membrane cannot have direct effect on activities inside taget cell; they have to cue intracellular intermediary to exert effects

Question 22

First messenger

Answer 22

the hormone that binds to the plasma membrane; leads to second messanger

Question 23

Second messenger

Answer 23

act as enzyme activator, inhibitor or cofactor resulting in change in rates of metabolic reactions

Question 24

Important second messengers:

Answer 24

Cyclic-AMP (cAMP) - derivative of ATP
Cyclic-GMP (cGMP) - derivative of GTP
Calcium ions

Question 25

The process of amplification

Answer 25

binding of a smaller number of hormone molecules to membrane receptors which leads to thousands of 2ed messengers in cell; magnifies effect of hormone on target cell

Question 26

down regulation

Answer 26

the presence of a hormone triggers a decrease in number of rormone receptors; when levels of hormone ar high, cells become less sensitive to it

Question 27

Up regulation

Answer 27

absence of a hormone triggers an increase in number of hormone receptors; when levels are low cells become MORE sensitive to it

Question 28

G protein

Answer 28

middle man between 1st and 2ed messenger, they bind to GTP and are activated when a hormone binds to its receptor at the membrane surface

Question 29

G Proteins and cAMP (fig 18-3)

Answer 29

G proteins increase or decrease the 2ed messenger cAMP levels in response to peptides, catecholamines and eicosanoids

Question 30

Increasing cAMP | 4 steps

Answer 30

1. activated G protein activates adenylate cyclase 2. adenylate cyclase converts ATP to cAMP 3. cAMP is now a 2ed messenger and activates kinase causing phosphorylation 4. phosphodiesterase inactivates cAMP to AMP making increased levels of cAMP short lived

Question 31

Decreasing cAMP | 4 steps

Answer 31

1. G protein activates phospholipase C (PLC) 2. triggers a receptor cascade allowing ca2+ release from intracellular reserve (SER) 3. phosphorylation of calcium channel proteins opens the channel and permits extracellular calcium to center the cell 4. calcium, acting as 2ed messenger, can bind to calmodulin which ativates other enzymes

Question 32

Hormones and intracellular receptors (fig. 18-4) 4 facts

Answer 32

1. alter rate of DNA transcription in nucleus 2. change patterns of protein synthesis 3. directly affect metabolic activity and structure of target cell 4. include steroid and thyroid hormones

Question 33

steroid hormones

Answer 33

diffuse through the plasma membrane and bind to receptor in the cytoplasm or nucleus; the hormone then binds to DNA in the nucleus to activate certain genes

Question 34

Thyroid hormones

Answer 34

enter the cytoplasm and bind to receptors of the mitochondria or in the nucleus; activates genes or accelerates ATP production

Question 35

The pituitary gland (fig 18-6)

Answer 35

also called the hypophysis; lies within cella tucica isolated from cranial cavity; hangs inferior to hypothalamus and is connected by the infundibulum

Question 36

Pituitary gland | 3 facts

Answer 36

1. releases 9 important peptide hormones 2. hormones bind to receptors 3. use cAMP as 2ed messenger

Question 37

Anterior lobe of pituitary gland

Answer 37

also called adenohypophysis; hormones turn on endocrine glands or support other organs

Question 38

hypothalamic control of the anterior lobe

Answer 38

two classes of hypothalamic regulatory hormones; rate of secretion is controlled by negative feedback 1. releasing hormones (RH)- stimulate synthesis and secretion of one or more hormones at anterior lobe 2. inhibiting hormones (IH)- prevent synthesis and secretion of hormones from the anterior lobe

Question 39

7 hormones of the anterior lobe

Answer 39

``` thyroid stimulating adrenocorticotropic gonadotropins follicle stimulating luteinizing prolactin growth hormone ```

Question 40

ACTH targets

Answer 40

glucocorticoids (effect glucose metabolism)

Question 41

Low levels of gonadotropins causes

Answer 41

hpogonadism; children can't mature sexually, adults sterile

Question 42

Luteinizing prepares the body for

Answer 42

pregnancy, stimulates testosterone in males

Question 43

prolactin is found in males and might help regulate ______ production?

Answer 43

testosterone

Question 44

Growth hormone stimulates growth indirectly

Answer 44

liver cells respond to GH by producing compounds that stimulate growth tissue; these peptides bind to receptors on membrane to increase uptake of amino acids for new protein synthesis

Question 45

Growth hormones stimulate growth directly

Answer 45

stem cell division and differentiation of epithelial and connective tissues, in adipose tissue; glucose-sparing effect where fatty acids are released from adipose tissue for energy, and in the liver; stimulates the break down of glycogen into glucose from the liver increasing blood glucose levels

Question 46

Posterior lobe of pituitary

Answer 46

contains unmyelinated axons of hypothaamic neurons; secretes antidiuretic hormone and oxytocin

Question 47

antidiuretic hormone also referred to as

Answer 47

vasopressin

Question 48

Thyroid gland

Answer 48

lies anterior to thyroid cartilage of larynx; consists of two lobes connected by narrow isthmus

Question 49

thyroid follicles

Answer 49

hollow spheres lined by cuboidal epithelium

Question 50

Thyroxine (t4)

Answer 50

contains 4 iodide ions | T4 can be converted to T3 in the liver when needs

Question 51

Triiodonthyronine (t3)

Answer 51

contains 3 iodide ions

Question 52

Causes thyroid follicles to become inactive?

Answer 52

the absence of thyroid stimulating hormone

Question 53

Functions of thyroid hormone

Answer 53

* essential to development of skeletal, muscular and nervous system in children * responsible for calorigenic effect where the cell consumes more energy resulting in increased heat generation and

Question 54

The C cells of the thyroid gland and calcitonin

Answer 54

* c (clear) cells also called parafollicular cells | * produce calcitonin (ct)