endocrine 1.2

Question 1

stretch reflex have different reflex arcs - patellar tendon*

Answer 1

stimulus on tendon

muscle spindle stretch and fire in quad

afferent path : AP travels through sensory neuron

sensory neuron synapses in spinal cord

2 different efferent paths : somatic motor neuron and interneuron

somatic motor neuron goes to quad and fires

interneuron inhibits somatic motor neuron going to hamstring (relaxes, reciprocal inhibition)

Question 2

endocrine secretion regulation : negative feedback between 2 hormones

Answer 2

A produces hormone A which acts on tissue B that produces hormone b and stops A from making hormone A

Question 3

negative feedback - between a hormone and a metabolite

Answer 3

tissue makes a hormone that increase the amount of compound which can be a metabolite, once the metabolite increases its going to stop the production of the original hormone

Question 4

negative feedback between antagonistic pairs of hormones

Answer 4

2 hormones that are going to work with a compound or metabolite
eg. release glucagon when sugar level low to increase
release insulin when sugar levels high to decrease

Question 5

positive feedforward

Answer 5

increase in estrogen cause positive feedforward to FSH and LH

Question 6

hormone transport in blood - water solubility

Answer 6

most peptide and all catecholamine hormones are water-soluble
-dissolve in plasma

• *steroid and thyroid hormones**
• bound to large proteins so they are not water soluble

Question 7

total hormone concentration in plasma

Answer 7

= free hormones + bound hormones

Question 8

free hormones

Answer 8

only free hormones can diffuse out of capillaries and encounter its target cells

-free hormones are what we look at in tests

when hormones are attached to large proteins in the blood they have to dissolve all to enter into a cell

Question 9

peptides and catecholamimes

Answer 9

• free (unbound) in plasma
• receptors on plasma membrane

signaling mechanisms :

most common signaling mechanisms

second messengers -cAMP, Ca, IP3

enzyme activation by receptor (JAK)

intrinsic enzymatic activity of receptor

Question 10

steroid and thyroid hormones

Answer 10

protein bound in plasma

receptor in intracellular

signaling mechanisms :

-intracellular receptors directly alter gene transcription

Question 11

hormones concentration in the plasma depends on

Answer 11

• its rate of secretion by the endocrine gland
• its rate of removal from the blood (metabolic transformation or excretion)

Question 12

what happens after the hormone acts on the target tissue

Answer 12

we clear the hormone

can have dangerous effects from prolonged exposure to target tissue if we don’t clear

Question 13

removal by excretion or metabolic transformation

Answer 13

• by the liver, kidneys or cells it acts upon
• enzymes in the blood and tissues rapidly breakdown catecholamine and peptide hormones

→ free vs protein-bound hormones (protein-bound hormones hard to get rid of)

-metabolism of a hormone can activate it instead of inactivating it

Question 14

released hormone secreted gets to blood then…

Answer 14

• excreted in urine/feces
• inactivated by metabolism
• bind to receptor and produce a cellular response
• activated by metabolism

Question 15

hormone receptors

Answer 15

• in order for a response to a hormone, need the SPECIFIC receptors to be present on or in target cells
• peptide hormones and catecholamines receptors on plasma membrane of target cells
• steroid and thyroid hormone receptors locateed inside the target cells

Question 16

regulation of hormone receptors

Answer 16

upregulate : increase number of a hormones receptors in a cell

→ because of prolonged exposure to low concentration of target tissue, we want to increase the sensitivity to the hormone

down-regulate : decrease the number of a hormones receptors in a cell

→ help prevent over stimulation

Question 17

permissiveness

Answer 17

your hormones can regulate its own receptors up and down regulation, but it can also up or down regulate another hormones receptor

• thyroid hormone increases the number of beta-adrenergic receptors on the cell, which epinephrine attaches to
• up-regulating so they become more sensitive to epinephrine

Question 18

effects of peptide hormones and catecholamines - activated receptor can directly influence..

Answer 18

1. enzyme activity that is part of the receptor
2. activity of cytoplasmic janus kinases associated with the receptor
3. G proteins coupled in the plasma membrane to effector protein-ion channels and enzymes that generate 2nd messengers such as cAMP and Ca2+

can exert both rapid and slower actions on the same target cell

Question 19

enzyme activity that is part of the receptor

Answer 19

Enzyme activity is part of the receptor itself

first messenger binds to a specific receptor, has a conformational change to receptor so enymatic side is activated

• results in phosphorylation of the receptor because it gets phosphate group from ATP
• makes phosphotyrosine and acts as a docking site for cytoplasmic proteins
• docking proteins climb behind to activate cells response to signalling pathway

Question 20

activity of cytoplasmic janus kinases associated with the receptor

Answer 20

janus kinase attached to receptor but not on it

• first messenger (peptide hormone or catacolamine) makes conformational change to receptor
• activation of janus kinase
• will phosphorylate different target proteins by taking phosphate from ATP and adding it to proteins and activating them
• results in a protein + ADP that carries out the cell’s response

Question 21

G proteins

Answer 21

G proteins coupled in the plasma membrane to effector proteins-ion channels and enzymes that generate 2nd messengers such as cAMP and Ca2+

-G proteins (alpha, beta, gamma) activate when first messenger binds

• Alpha leaves when activated and binds to GTP lined to plasma membrane
• leads to different events towards cell response such as secondary mesengers and change in membrane potential

Question 21

G proteins

Answer 21

G proteins coupled in the plasma membrane to effector proteins-ion channels and enzymes that generate 2nd messengers such as cAMP and Ca2+

-G proteins (alpha, beta, gamma) activate when first messenger binds

• Alpha leaves when activated and binds to GTP lined to plasma membrane
• leads to different events towards cell response such as secondary mesengers and change in membrane potential

Question 22

effects of steroid and thyroid hormone

Answer 22

• leads to activation or inhibition of the transcription of particular genes
• when we change the concentration of proteins, we see an activation or inhibition of particular processes the cell carries out or a change in the cell’s rate of protein secretion
• receptors can be in nucleus or cytosol (will move to the nucleus)
• binds to DNA to do gene transcription