Exam 3- Histology and Function of the Pituitary and Pineal Gland Flashcards
what are the three parts of the anterior lobe of the pituitary?
pars distalis
pars tuberalis
pars intermedia
what are the parts of the posterior lobe of the pituitary?
pars nervosa
infundibulum (infundibular process and median eminence)
what are the effects of thyrotropin releasing hormone (TRH)?
stimulates thyrotropes to secrete TSH (stimulates secretion thyroxin)
stimulates lactotropes to secrete prolactin
stimulates melanotropes to secrete POMC, which is processed into ACTH and other things
what does the hypothalamus respond to?
impulses from CNS
circulating levels hormones
inflammatory mediators
what are the three histologic cell types in the pars distalis?
acidophils
basophils
chromophobes
are there basophils in the pars intermedia?
yes, but no acidophils
what type of hormones do basophils produce?
tropic hormones: regulate other endocrine glands
what type of hormones do acidophils produce?
hormones that act directly on target organs
what is canine cushings disease caused by?
tumor in pars distalis
what is equine pars intermedia dysfunction caused by?
tumor in pars intermedia
does the hypothalamohypophyseal tract end on another neuron?
no; end near capillaries
what is neurohypophysis referring to?
hormones released from posterior pituitary actually produced in hypothalamus
what are herring bodies?
dilated portion of axon, neurosecretory vesicle storage site, hormones bound to neurophysin
what does the pineal gland produce that helps to regulate biorhythms?
melatonin
does melatonin play a role in breeding?
yes, in seasonal breeders
where is the pineal gland in reptiles?
close to surface of brain and receives light signals from parietal organ: third eye
not snakes
where does the pineal gland in mammals get light signals from?
eyes
what is the pathway for light going from mammalian eyes to the pineal gland?
retina to suprachiastmatic nucleus to superior cervical ganglia to pineal gland
what are corpora arenacea?
concentric calcium deposits characteristic of the pineal gland
what are hypothalamic hormones to regulate the anterior pituitary?
corticotropin-releasing hormone (CRH)
thyrotropin releasing hormone (TRH)
growth hormone releasing hormone (GHRH)
somatostatin
gonadotropin releasing hormone (GnRH)
dopamine
where do the primary capillaries in the hypothalamus drain?
hypophyseal portal veins
does the pars distalis have direct arterial supply?
no
true/false: the anterior pituitary is controlled only by the hypothalamus
false: also circulating levels hormones and paracrine secretions from cells in pituitary
what cells release adrenocorticotropic hormone (ACTH, POMC)?
corticotropes: pars distalis
melanotropes: pars intermedia
what cells release melanocyte-stimulating hormone (MSH from POMC)?
melanotropes: pars intermedia
what does post-translational modification of POMC within secretory granules result in?
ACTH
melanocyte stimulating hormone
beta-endorphin
what stimulates secretion of products of POMC?
corticotropes
melanotropes
are the neurons in the hypothalamohypophyseal tract myelinated?
no
what can be seen in the pars nervosa?
nonmyelinated axons with herring bodies
capillaries (fenestrated)
pituicytes (glial cells)
true/false: more melatonin is produced at night
true
what does melatonin control?
sleep cycles and functions associated with circadian rhythm
what does melatonin do in fall breeders when days are short?
increased melatonin stimulates GnRH (LH and FSH) secretion and reproduction
what does melatonin do in spring breeders?
when days are short, melatonin inhibits GnRH secretion, suppressing libido
what is in the pineal gland histologically?
pinealocytes
glial cells (astrocytes)
capillary endothelial cells
sometimes melanocytes
corpora arenacea (“brain sand”): concentric calcium deposits
where in the hypothalamus is responsible for production of antidiuretic hormone and oxytocin?
paraventricular nucleus
supraoptic nucleus
true/false: melatonin promotes sleep in nocturnal animals
false: promotes activity
true/false: all reptiles have a pineal body
false: not snakes
