Endocrine 2 Flashcards
Pituitary Gland
- located at the base of the Brian and is attached to the hypothalamus
- the hypothalamus controls the secretion of pituitary hormones (when activated by neural input, the hypothalamus stimulates the pituitary gland to secrete hormones)
- some pituitary hormones stimulate target cells and some stimulate the secretion of hormones by other endocrine glands
- has two parts: anterior lobe and posterior lobe
- each part has a distinctive mechanism for hormone secretion
Posterior lobe of the pituitary gland
- connected the the hypothalamus by neurons
- secretes hormones into blood
How does the hypothalamus communicate with the posterior pituitary
- the hypothalamus is connected to the posterior lobe by neurons: cell bodies in the hypothalamus, axons terminate in the posterior lobe.
- posterior pituitary hormones - are made in the hypothalamus (cell body of neuron), travel down the axon, and are stored at the axon endings until requires (peptide hormones)
- the hypothalamus uses neural communication with the posterior lobe to release hormones into the blood: results in an increase or decrease of frequency of action potentials leads to a corresponding change in hormaone release
- Antidiuretic hormone (ADH) or oxytocin released into blood
Hormones released by posterior pituitary
- antiduereitc hormone
- oxytocin
Antidiuretic hormone
- stimulates the kidneys to reabsord water (the kidneys conserve water when the body dehydrates)
Oxytocin
- stimulates the contraction of uterine muscles during childbirth (an example of positive feedback)
- stimulates milk release in breastfeeding (mild ejection reflex )
Where are the two hormones made
Both hormones are Mede in the hypothalamus and stored int the posterior pituitary until required
Anterior love of the pituitary gland
Connected to the hypothalamus by blood vessels
- hypothalamus hormones stimulate or inhibit release of stored hormones form specific anterior pituitary cells
How does the hypothalamus communicate with the anterior pituitary
I don’t understand this one
Stimulus: neural input within hypothalamus
- hypothalamus signals the anterior pituitary to release hormones by hormonal stimulation, secreting stored releasing hormone (or inhibiting hormone)
- hormone binds to receptor on membrane of a specific cell type and a specific anterior pituitary hormone is secreted e.g. prolactin, growth hormone
Feedback regulation of the anterior pituitary gland- HOW EFFECT IS TURNED ON
Stimulus
Hypothalamus releases releasing hormone that travels through portable blood system down the anterior pituitary gland
Anterior putiotary gland releases the pituartay hormone that travels through the blood and around the body to a target organ or tissue
Target organ releases another hormone - this is the hormone that goes on and has the effects
Feedback regulation of the anterior pituitary gland- HOW EFFECT IS TURNED OFF
- 3rd hormone will negatively impractical the anterior punitary gland and the hypothalamus from releasing their hormones
Anterior pituitary hormones
(Many others as well)
Growth hormone controlled release - NEGATIVE FEED BACK INHIBITION
- IGF-1 inhibits the release fo further GHRH
- IGF-1 encourages the releases of GHIH, which will then inhibit the release of growth hormone from the anterior putirtary
Growth hormone has ____ actions and in____ actions
Anterior pituitary growth hormone has direct effects on the function of liver muscle and fat as well as indirect effects through the actions of IGF-1
Direct effects of GH
Muscle: stimulates protein synthesis (long term) and inhibits cellular uptake of glucose (short term)
Liver: stimulates glucose synthesis (short term)
Fat: increases triglyceride breakdown in adipose tissue (short term)
Indirect effects of GH
Promotes the growth of bones, muscle and other tissues by release of somatomedin C, which promotes cell division (long term)
GH has a _____ effect on ____ and ______ effects on ______
GH has a long term effect on growth ( cos IGF-1promotes cell division) and short term effects on metabolism
Pattern of growth hormone secretion over a day
GH concentrations have peaks and troughs throughout the whole day
GH concentrations are highest during sleep
Pattern of growth hormone secretion over a life time
- GH concentrations are higher in children then adults, with a peak period during puberty
- GH secretion declines with aging
Sum
Growth hormone controlled release
- hypothalamus decides if a response is needed
- hypothalamus releases GH-RH from GHRH neurons into portal blood system
- causes anterior pituitary to release growth hormone
- growth hormone travels through the systemic circulation and that will act on the liver
- causes liver to release somatomedin C (IGF-1) - EFFECTOR
Growth hormone feedback loop
Hypothalamus (after it has inrergrated information about whererter or not a response is needed) will release GHRH into portal blood vessels
This causes the anterior pituitary gland to release growth hormone
Growth hormone travels through the systemic circulation and will act upon the liver causing the release of somatomedin C (IGF-1)
Effects in body
