W3 - Endocrine Axes (essential reading) Flashcards
(37 cards)
To maintain the internal environment, what is needed?
-ve feedback loop
What does the -ve feedback loop aim to get a controlled variable to?
Physiological set point
Describe +ve feedback loop in terms of variable and the physiological set point
Accelerates variable’s level away from physiological set point
What differs between the different types of feedback loops?
The number of control points
Direct/first order feedback loops, second order and third order feedback loops have how many control points?
Direct/first - one, second - two, third - three
What type of feedback loops are typically in vertebrates?
2nd and 3rd
Direct FL - a physiological stimulus directly stimulates the endocrine gland to release hormones into circulatory system, what is the one control point in this pathway?
After the target organ is acted on, the target organ produces a physiological response which decreases the incoming stimulus (this is the CP)
ANP is the one example of a DFL in mammals, what does it do to decrease the plasma volume (to stop stretched atria)?
Released from atrial cardiomyocytes, it acts on kidney to increase Na+ and therefore water lost in urine, decreasing plasma volume and the stretch
What is the CP in the ANP DFL?
The decreased volume of plasma decreasing the stretch in the atria lessens the stimulus to release ANP
What are series of interacting endocrine glands referred to as?
Endocrine axis
Describe the pathway of SODL from change in variable detected to target organ
Change in variable detected by sensor which sends signal via sensory neuron to integrator, integrator sends signal via neuron to intermediary endocrine gland, endo gland secretes hormones into circ system to act on target organ
What are the two CPs that are used in SOFLs?
Lowers stimulus to sensor AND suppresses action of endocrine gland
Describe the pathway of TODL from change in variable detected to endocrine gland 1
Change in variable detected by sensor which sends signal via sensory neuron to integrator, integrator sends signal to intermediary endocrine gland, endo gland 1 secretes H1
Describe pathway of TODL from endo gland 1 to target organ
H1 moves via circ system to second intermediary endo gland which secretes H2, H2 acts on target organ
What are the 3 CPs for a TODL?
Lowers stimulus to sensor, suppression of endo gland 1 activity AND endo gland 2
Where does the hypothalamus sit in relation to the thalamus and what connects the HT to the pituitary gland?
HT sits below T and HT is connected to the PG via the infundibulum
The posterior pituitary lobe (neurohypophysis) is formed by an outgrowth of neural tissue down from the…
Hypothalamus
The anterior pituitary lobe (adenohypophysis) is formed by a growth of glandular epithelial tissue up from the…
Roof of the buccal cavity
The hypothalamus contains different neurons in discrete hypothalamic nuclei, the endocrine cells of the anterior pituitary also have distinct populations for different hormones, how many different hormones are there?
5
Neurohypophyseal hormones are transc/transl in the HT and then transported along axons from HT to be secreted by post PG, what neurons are used here, where are their cell bodies and where do their axons travel?
Magnocellular neurons, cell bodies are in the HT and the axons travel down thee hypothalamo-hypophyseal tract
How is the HT connected to the anterior PG and where are the two major capillary beds found?
Via the hypothalamo-hypophyseal portal circulation, capillary beds in median eminence of HT and in anterior PG
Which neurons are involved in the anterior PG transport of hormones?
Hypothalamic parvicellular neurons
The hypothalamus responds to endocrine or neural stimuli by synthesis/secretion of 6 hypophysiotropic hormones. How many of these are peptide hormones and how many are NTMs?
5 peptide HM, 1 NTM (dopamine)
List the 6 hypophysiotropic hormones
Dopamine, TGH, CRH, GHRH, GHIH, GnRH
