PNB Exam #4 (3rd set of videos)

what is the second system that operates in communication throughout the body other than the NS

Endocrine system

what are the 5 factors that influence the release of various hormones

- change in plasma ion concentration

- change in organic nutrient concentration

- neurotransmitter activation of hormonal release

- circadian rhythms

- many other hormones have their own set of regulating factors

what is an example of change in plasma ion concertation that influence hormones

calcium regulation: PTH and calcitonin

when is PTH released? when is calcitonin released?

PTH: when blood calcium = low

- releases stored calcium (from bones)

Calcitonin: when blood calcium = high

- stores calcium (in bones)

what is an example of hormones being released due to change in organic nutrient concentration

glucose and regulation of insulin

what is insulin's job

job is to help cells in the body take up glucose

- brings them into the cell so they can use them for energy

when is insulin released

when plasma glucose is high

what is an example of hormones being released due to neurotransmitter activation of hormonal release

preganglionic cells synapse with the chromaffin cells in the adrenal medulla which stimulates epinephrine

what is an example of hormones being released for circadian rhythms

melatonin is secreted as darkness comes in

are the reasons that hormones are released mutually exclusive

NO: reasons can occur at the same time

what is the parathyroid hormone secreted by

parathyroid gland

- which is embedded in the posterior side of the thyroid gland

what does PTH help do

raise blood calcium levels

what is calcitonin secreted by

thyroid gland

- c cells of thyroid gland

what does calcitonin do

lowers blood calcium levels

what do PTH and calcitonin do together

maintain homeostatic levels of calcium in plasma

what does pleiotropic mean

has many affects

what else does calcitonin do

also stimulates the kidneys to start excreting more calcium

- more calcium will be part of the urine and leave the body

what else does parathyroid hormone do

- causes more reabsorption of calcium from kidneys

- stimulates another hormone called calcitriol

how does PTH cause reabsorption of calcium from the kidneys

- some of the blood initially becomes filtrate fluid

- takes as much calcium as it can from filtrate, so we do not pee it out

what does calcitriol do

acts on GI tract (digestive system) to help absorb as much calcium as we can from food

all of PTH target tissues are working together to do what

to increase blood calcium levels and bring us back to homeostatic set point

PTH and calcitonin both show ...

different effects on their different target tissues of the same hormone but all of their responses work together towards one goal

(PTH has one goal)

(Calcitonin has one goal)

what system is epinephrine regulated by

the NS

- specifically autonomic NS

what is within the adrenal gland (specifically adrenal medulla)

modified post ganglionic neurons called chromaffin cells

what are chromaffin cells innervated by? what do these neurons release?

preganglionic sympathetic neurons (cholinergic neurons) that release ACH in the adrenal medulla

what does the ACH that is released in the adrenal medulla do

it stimulates the chromaffin cells to release epinephrine directly into the blood stream

- that epinephrine will circulate and create a coordinated effect

what is epinephrine classified as because it travels through the blood

here it is classified as a hormone even though it is regulated by the ANS

- some hormones are regulated by the ANS

can hormones interact with other hormones?

yes

what happens when epinephrine and thyroid hormone interact

both epinephrine and thyroid hormone function in releasing stored nutrients for our bodies to use for energy

- thyroid hormone on its own has a limited affect

- epinephrine can cause stimulation to release some fatty acids

- together they have a huge effect on fatty acid release

why do epinephrine and TH have a huge effect on fatty acid release

thyroid hormone has a priming effect on adipose tissue

- primes it for epinephrine and enhances response of adipose tissue to epinephrine hormones

how can hormones modulate the effects of other hormones

usually through receptors

- through creation of more receptors or enhancing sensitivity of that receptor -> permissiveness

what is permissveness

upregulation of the sensitivity of a hormone in a particular tissue through the secretion of a different hormone

how else can hormones affect other hormones

they can interact with each other by causing the synthesis and secretion of other hormones

what is the pituitary gland

major regulator of peripheral hormone release

what is the anterior pituitary also called

adenohypophysis

what is the anterior pituitary? what is it made from?

- more of a typical endocrine gland structure

- made of epithelial tissue

what do the epithelial cells of the anterior pituitary gland secrete

secretes hormones

what is the posterior pituitary called and why

neurohypophysis: named for nervous tissue

what is within the posterior pituitary

neurons

why is the posterior pituitary considered neuroendocrine

has neurons but these neurons actually secrete hormones that travel through the blood stream

pituitary once was believed to be the master control center of all different hormones: why is it no longer considered that?

pituitary gland is actually highly regulated by the hypothalamus

where do the neurons within the tissue of the posterior pituitary extend from and where do they go

cell bodies: hypothalamus

axons: extend down

axon terminals: tissue (neuroendocrine tissue) of the posterior pituitary gland

where are the cell bodies of the posterior pituitary actional located (2 regions)

in hypothalamus

1) supraoptic region

2) paraventricular nuclei (PVN)

what happens in the supraoptic region and the paraventricular nuclei

hormones are synthesized here and they travel down the axon

once hormones travel down the axon from the hypothalamus to the posterior pituitary gland, where do they go

then stored and released into the blood stream through capillaries in the posterior pituitary

what are the 2 hormones released by the posterior pituitary

- oxytocin

- ADH / vasopressin (antidiuretic hormone)

what are the 2 hormones released by the posterior pituitary referred to as? why?

neurohormones: synthesized by neurons but released into the blood stream

what is the general function of ADH

helps us with water regulation: specifically, when we do not have enough water in our bodies

- helps us retain more water

what is the function of oxytocin

producing contractions in smooth muscle

- particularly in reproductive organs

how does ADH regulate water

by taking H2O from fluid that is about to become urine

how is urine made

in kidneys: much of blood is filtered to become a fluid called filtrate

what happens after fluid becomes filtrate (to make urine)

filtrate passes through a series of tubes

- filtrated is refined by reabsorbing some substances back into blood and secreting other substances into the filtrate

what happens when the kidney is satisfied with the filtrate product

becomes urine that exits our bodies

what happens when we secrete ADH

it travels through the blood stream and then acts on target tissue

what is the target tissue of ADH

the collecting duct: one of the tubes in the kidney

what happens after the ADH acts on the collecting duct

ADH inserts aquaporins into the tubule which allows more H2O to be reabsorbed into he capillary

- we will keep that H2O in the blood

what does taking out H20 from our urine do

causes less urine and causes the urine to be a dark yellow

what is oxytocin involved in (in terms of breast-feeding mothers)

the milk let down

when is oxytocin released (in terms of breast-feeding mothers) 2 causes

- thinking about baby (hearing it cry)

- stimulation of breasts from baby

what happens to initiate birth

smooth muscles of uterus contract and the cervix stretches as baby enters birth canal

what does the stretching of the cervix during childbirth cause

causes brain to release oxytocin from the posterior pituitary

- oxytocin will then enhance the contractions of the uterus which will continue to stretch and dilate the cervix

what type of feedback loop is childbirth and why

positive feedback loop: stimulus is stretching of the cervix, and oxytocin works to further stretch and dilate the cervix

what is another role of oxytocin in the body

released when we are in the presence/ in physical contact with a partner

- can be called romance hormone

- also released when interacting/ cuddling with pet

does the hypothalamus also regulate the anterior pituitary

yes

what is the tuberal region of the hypothalamus and how does it interact with the anterior pituitary gland

contains neurons that secrete hormones directly into a capillary bed that then flows into veins, and then flow into another capillary bed in the anterior pituitary

what are the hormones that are released from the hypothalamus to the anterior pituitary gland known as

releasing and inhibiting hormones

what do releasing and inhibiting hormones do

they stimulate the release or inhibition of hormones from the anterior pituitary gland

why is the vascular network important to the hypothalamus and the anterior pituitary gland?

they have vessels that travel between the hypothalamic capillary bed and the anterior pituitary bed

- normally entering a capillary bed will travel towards bigger veins then into the heart

what is the vein between the two capillary beds called

portal vessel or portal vein

what is the whole system of veins and beds between the hypothalamus and the anterior pituitary called

hypotheses portal system or hypothalamic pituitary portal system

are the neurons going to the anterior pituitary shorter or longer than the ones going to the posterior pituitary: why?

much shorter: they do not leave the hypothalamus

- instead, they secrete the hormones into blood vessels to the anterior pituitary where they meet the receptors

what happens after the hormones from the hypothalamus reach the receptors in the anterior pituitary

they initiate the secretion of other hormones: known as tropic hormones

where do the tropic hormones go after the anterior pituitary

they will travel to peripheral endocrine tissues in the body where it will release other hormones

where do releasing and inhibiting hormones come from

hypothalamus

where do the tropic hormones come from

anterior pituitary gland

where do effect hormones come from

peripheral endocrine glands

what do effector tissues do

go to their target tissues and cause a response that will negate the stimulus

what maintains homeostasis

negative feedback loops

what is an ultra short loop

- releasing hormone on hypothalamus

releasing hormones within the thalamus can cause inhibition of that same releasing hormone from being secreted further

what is a short loop

tropic hormone on hypothalamus

- feedback of the anterior pituitary hormone/ tropic hormone feeding back on the hypothalamus

what is a long loop

effector hormone on hypothalamus and anterior pituitary

- when levels of the effector hormone are high in the plasma -> feedback on the anterior pituitary & hypothalamus - causes those tissues to stop secreting their hormones

is breast feeding a negative or positive feedback loop

positive feedback

how does the positive feedback of breast-feeding work

suckling of baby initiates a stimulation that is sent to the brain, and oxytocin is released from hypothalamus

in the positive feedback loop of breast feeding what happens after oxytocin is released from the hypothalamus

the oxytocin is sent into the posterior pituitary and then released into the blood stream

in the positive feedback loop of breast feeding what happens after oxytocin is in the blood stream

the lactiferous ducts are going to squeeze and release breast milk

- that release of milk will cause more suckling for the baby

- repeats

what is milk synthesis regulated by

the hormone prolactin

- also estrogen and cortisol

when does prolactin play a major role in the body

just after childbirth: suckling can initiate the secretion of prolactin which creates milk

what is growth hormone released from

the anterior pituitary

what is growth hormone regulated by

regulated by releasing hormones of the hypothalamus

what is the releasing hormone for growth hormone called

Growth hormone releasing hormone: GHRH

what are the 5 reasons GHRH is released

1) low plasma glucose

2) raised plasma arginine

3) exercise

4) sleep

5) fasting

why does raised plasma arginine release GHRH

when we have readily availible amino acids (particularly arginine) it can release GHRH

why do exercise, sleep, and fasting release GHRH

they all decrease our nutrient availability to make ATP

What is Growth Hormone Inhibiting Hormone produced by

hypothalamus

what does GHIH do

stops production of GHRH and inhibits release of GH

is growth hormone just involved in growth

no: many functions

what are the two types of functions of growth hormone

- effecter functions (metabolic)

- tropic functions (growth)

what does it mean that GH has effector functions

- GH works directly as a hormone

- METABOLIC EFFECT

what is the metabolic effect of GH

increases nutrient availability to make ATP

- that increases our metabolic activity

- it triggers lipolysis of fats so we can use fats to make ATP

what are GHs tropic functions

targets the liver: the liver works as an endocrine tissue and releases insulin-like growth factor 1 / somatomedins