Lecture 33 Flashcards
Where is the hypothalamus located?
Inferior to the thalamus, roughly in the center of the brain.
How is the pituitary gland attached to the hypothalamus?
The pituitary gland is found inferior to the hypothalamus and is attached via a thin stalk known as the infundibulum, between the hypothalamus and the pituitary gland (the part which isn’t connected) is a series of blood vessels known as the hypophyseal portal system.
What are the proper names of the two parts of the pituitary gland? What hormones does each side release?
The anterior lobe is more correctly known as the adenohypophysis and the posterior lobe is known as the neurohypophysis.
The adenohypophysis releases growth hormone (GH), adenocoticotropic hormone (ACTH), thyroid stimulating hormone (TSH), gonadotropic hormones (FSH (follicle stimulating hormone) and LH (luteinizing hormone) and prolactin
The neurohypophysis releases antidiuretic hormone (ADH) and oxytocin (OT).
What hormones released by the hypothalamus inhibit hormone secretion by the anterior pituitary gland?
Somatostatin (SS) inhibits Thyroid stimulating hormone and growth hormone secretion. Prolactin inhibitory hormone inhibits prolactin secretion.
What hormones released by the hypothalamus stimulate the anterior pituitary gland?
Gonadotropin-releasing hormone (GnRH) stimulates release of the gonadotropic hormones (follicle-stimulating hormone (FSH) and luteinizing hormone (LH)).
Growth hormone releasing hormone (GHRH) stimulates secretion of growth hormone.
Thyroid release hormone (TRH) signals secretion of Thyroid stimulating hormone and prolactin.
Prolactin release hormone (PRH) signals for secretion of prolactin.
Cortisol release hormone (CRH) signals for release of adrenocorticotropic hormone).
What are the main effects of the anterior pituitary hormones?
Follicle stimulating hormone (FSH) and luteinizing hormone (LH) both cause effects in the gonads such as estrogen and testosterone secretion.
Growth hormone aids in nutrient metabolism and tissue growth.
Thyroid stimulating hormone triggers the thyroid gland to release thyroid hormones.
Prolactin helps in breast development and milk production. Adrenocorticotropic hormone causes cortisol secretion from the adrenal cortex.
How does the hypothalamus trigger secretions in the anterior pituitary gland?
The hypothalamus has neurons which synapse at the median eminence, here neurotransmitter is released into the hypophyseal portal system (blood vessels which join the pituitary gland and the hypothalamus). These hormones then quickly(due to the short distance) reach the anterior pituitary gland and are noticed by receptors which trigger the necessary response.
How does the hypothalamus trigger secretions from the posterior pituitary gland?
In this case the hypothalamus is connected to the posterior pituitary gland by neurons which terminate in the posterior lobe of the pituitary. The amount of secretion can be regulated by increasing or decreasing the frequency of action potentials down these neurons.
What seperates the storage/release of hormones from the two pituitary lobes?
The anterior lobe doesn’t store hormones before releasing them, the hormones are made on demand and released. For the posterior lobe however they are stored at the synaptic knob of the posterior lobe actions until required.
What are the functions of the posterior pituitary lobe hormones? What is odd about where they are produced?
Antidiuretic hormone stimulates the kidneys to reabsorb water, helping our bodies conserve water when dehydrated.
Oxytocin has many effects, but a few are the stimulation of the uterine muscles to contract during childbirth, stimulating the milk release when breast feeding.
Both hormones are produced in the hypothalamus and stored until required.
How does the negative feedback system for ADH work?
ADH (antidiuretic hormone) is released by the hypothalamus when the osmoreceptors detect a high ECF osmolarity concentration, this signals that there is not enough water and as such the kidneys respond to the ADH and conserve water by opening water channels back into the blood stream. This means less water is lost and as such water entering the system is more effective, as such the osmolarity decreases as the person is no longer dehydrated. The osmoreceptors no longer detect a high osmolarity and hence the hypothalamus stops secreting ADH.
How does the positive feedback system for oxytocin work?
As the baby suckles a message is sent ot the hypothalamus to release the milk, as the milk is lost another message is sent to the hypothalamus, the hypothalamus releases oxytocin to have the milk replaced. Once the baby stops the oxytocin signal is stopped and hence the milk will also stop.
