Endocrine system

Question 1

Difference between endocrine and exocrine glands?

Answer 1

Endocrine = ductless glands

Exocrine = sebaceous glands/sweat glands in integumentary system; contains an acinus which has a duct for secretion/release of their products

Question 2

What is autocrine, paracrine and neurocrine?

Answer 2

Autocrine = A > hormone > A response

• some cell producing hormone is some cell influenced by that hormon

Paracrine = A > hormone > B response

• Hormone travels to a nearby cell inducing appropriate responses

Neurocrine = Neuron > hormone > bloodstream > B > response

Question 3

WHat is a hormone?

Answer 3

A chemical substance released in the ECF that regulates the metabolic functions of other cells in the body

Question 4

What are important characteristics about hormones?

Answer 4

• Hormones must bind to specific receptors to influence target cell functions
• Hormones are specific - they can only influence target cells that express receptors for it, the level of target cell activation depends on;
  a) hormone concentration
  b) target cell receptor content (if a cell expresses a lot of receptors, there is a stronger stimulation)
  c) affinity of hormone for receptor (low affinity = hormone might bind to it or pass it by) i.e. how strongly that hormone is attracted to the receptor to bind to it

Question 5

What is the main mechanism of action of a peptide/protein hormone?

Answer 5

A water soluble hormone so it cannot cross the plasma membrane

Bind to a cell surface receptor
Activation of membrane bound G protein
Production of 2nd messenger (cyclic AMP(
Activation of protein kinases to regulate activity of key enzymes, open/close channels

Protein kinases = able to phosphorylate targets

Question 6

What is phosphodiesterase?

Answer 6

Enzyme that degrades leftover cAMP molecules

Important in bringing the stimulation to and end so that hormones can still later stimulate receptors when needed

Question 7

what are steroid hormones?

Answer 7

Lipid soluble therefore they can enter the nucleus and activate gene transcription

Because they are lipid soluble they can easily cross the PM/nuclear membrane

Question 8

what is a half life pertaining to a hormone?

Answer 8

the persistence of a hormone in the blood

steroid hormones tend to last longer in the bloodstream while peptide/proteins/amino acids usually diffuse out of the blood therefore staying there for a shorter period of time

Question 9

what does the blood level of a hormone depend on?

Answer 9

• rate of synthesis
• rate of degradation/clearance from the blood (how long the hormone is being broken down for or removed from the blood)

Question 10

Where is the one place during a hormonal response where the ratio is 1:1 in the sequence of products forming?

Answer 10

Between cylic AMP to the activated protein kinases because only 1 cAMP can bind to 1 protein kinase

Question 11

Describe the 3 types of stimuli for a hormonal release

Answer 11

1. Humoral stimuli; hormone secretion in direct response to a change in the blood level of a nutrient or ion (PTH and blood Ca+2)
2. Neural stimuli; not as common (sympathetic NS and epinephrine release by the adrenal medulla)
3. Hormonal stimuli; a 3 tierd system (hypothalamus, pituitary and target endocrine gland) - hypothalamic-pituitary axis

Question 12

what is a portal system?

Answer 12

A set of 2 capillaries with direct communication via the veins (2 capillary beds connected through veins)

Question 13

What type of stimuli is the hypothalamus?

Answer 13

Neural; produces a number of releasing factors (hormones) that travel to the anterior pituitary via the hypophyseal portal system

Question 14

What structure connects the pituitary to the hypothalamus?

Answer 14

Infundibulum

Question 15

What is the posterior lobe considered as?

Answer 15

A hormone storage area; releases hormones but does not produce them

Question 16

What is SON and PVN?

Answer 16

Antidiuretic hormone (SON) = involved in water balance via supraoptic

Oxytocin (PVN) = controls smooth muscle contraction via paraventricular and is located primarily in walls of the uterus

Question 17

What are key differences between the ANS and the endocrine system?

Answer 17

ANS;

• sympathetic vs parasympathetic motor output
• fast responses
• uses pathways to reach target organs

Endocrine;

• hormones are released into ECF and often travel to target organs via the bloodstream
• slower response time but response usually lasts longer
• different chemical classes of hormones with associated mechanisms of action (recall steroid hormones enter directly to the nucleus of a cell)