Hypothalamus/ Ant and Post Pituitary Flashcards
Types of Secretory Patterns
- Circadian (diurnal) Rhythm
- Ultradian Rhythm
- Stimulus Induced
- Longer time interval Rhythms
What is the most common example of a circadian rhythm hormone?
Cortisol
- ACTH stimulates cortisol release so it also has a circadian rhythm
What is an ultradian rhythm and what is an example?
An Ultradian rhythm is one that occurs multiple times each day.
LH (leutenizing Hormone) release is an example
Three methods of controlling plasma hormone concentrations?
1) Increases or decrease secretion rate
2) Increase or decrease the level of hormone biding protein for that particular hormone
3) Increase or decrease degradation rate
Positive feedback
The endocrine system’s response to a stimulus reinforces that stimulus.
Ex: stretch of the cervix stimulates oxytocin release, this leads to more stretch of the cervix
Negative feedback
The endocrine system’s response to a stimulus is to reduce that stimulus
Describe the negative feedback mechanism associated with a rise in plasma glucose
Plasma glucose ^^ –> Rise in Insulin secretion–> Inc concentration of insulin in the plasma –> Rise in glucose uptake and utilization by the muscle and adipose tissue –> plasma glucose slowly goes back down to normal
So…how does the plasma glucose level keep from dropping too far below normal?
As Plasma Glucose Goes down –> GLUCAGON is secreted –> Hepatic Glucose is released –> Plasma glucose concentration comes back to normal.
How do hormones move from the top region of the pituitary gland to the bottom?
Axoplasmic flow…takes about a week for them to move this short distance.
How does hormone get stimulated to start the movement down the center of the pituitary?
Action potential
Where is the Pituitary gland located
base of brain in a bony pocket called the Sella turcica
What connects the pituitary to the base of the brain?
Infundibulum…this contains the nerves and veins
What are the two posterior pituitary gland hormones?
ADH and OT (oxytocin)
The posterior pituitary is basically a neural extension of the hypothalamus…where do the nerve axons come from?
Mainly from two nuclei in the hypothalamus: the Supraoptic nucleus (SON) and the Paraventricular Nucleus (PVN). The axon terminals are located near capillaries in the posterior pituitary and release their hormones here.
The area where hormones are released in the posterior pituitary is called?
Pars Nervosa
What is the function of Oxytocin…KNOW
stimulates contraction of the uterus and myoepithelial cells in the mammary gland (pushes out breastmilk)
WHat is the function of ADH,,,KNOW
regulates retention of water by increasing water channels in the walls of the kidney.
Also increases the contractility of vascular smooth muscle…Pressor effectM
REMEMBER: Oxytocin and Vasopressin have slightly overlapping activity
What is the chemical structure of ADH and OT
Nonapeptides (nine amino acids), both have a disulfide bridge, very similar structure which explains their overlapping activity
When are ADH and OT secreted
When action potentials reach their nerve terminals. Analogous to neurotransmitter release
- They are secreted together with their respective neurophysins
Main stimuli of ADH
Low ECF (plasma) volume
Plasma volume has to drop by how much to lead to increase in ADH secretion
5-10 %
Osmolarity has to change by how much to increase ADH secretion
1-2%
KNOW THE EXPERIMENT ON STALK SECTION AND RECOVERY
ok
Where does most of the blood supply to the pituitary gland come from
looks like it comes from the Internal carotid artery for the most part
What are the six major hormones of the anterior pituitary glands
GH (Growth Hormone), PRL (Prolactin), ACTH (adrenocorticotrophic hormone), LH, FSH, TSH
Most are called Trophic hormones….means it makes target tissues grow
Chemical nature of the hormones secreted from ant pituitary)
ACTH….39 amino acids, straight chain
Glycoproteins: TSH, FSH, LH….all are dimers of alpha and beta subunits and all have alpha and beta subunits that are very similar, but different enough to lead to different bioloogical functions. (Beta subunit accounts for the difference), SO IF YOU DO AN ASSAY, YOU WANT TO MEASURE THE BETA SUBUNIT»»KNOW THIS
Proteins: GH and PRL. These are the acidophils (they occupy about 75% of the Pituitary)
The biological activity of ACTH is found at what end?
The end opposite of the COOH….you only need about 20 amino acids for biological activity
ACTH 1-24?
Its the first 24 AAs but it has full activity
MSH activity is what
Melanocyte stimulating hormone…the structure of this hormone lies within ACTH so excess ACTH causes hyperpigmentation
The six releasing hormones and their effects
CRH- Corticotrophin releasing hormone increases ACTH secretion
TRH- increases TSH secretion
GNRH- inc LH and FSH
GHRH- Gh release
Somatostatin- GH goes down
Dopamine- Prolactin decreases
Where are the osmoreceptors that sense changes in plasma osmolarity that would lead to an upregulation in vasopressin (ADH)?
Hypothalamus…KNOW
So changes in plasma osmolarity are realized by osmoreceptors where?
hypothalamus (Supraoptic and Paraventricular Nuclei)
Changes in plasma volume (ECF volume) are recognized by volume receptors where?
Central nervous System
Which hormones from teh anterior pituitary stain acidophilic
GH, Prolactin
Regarding the family groupings of anterior pituitary hormones, which fall into the glycoprotein family
TSH, LH, FSH
Regarding the family groupings of the anterior pituitary hormones, which fall into the protein family
GH and Prolactin
Oxytocin secretion is tied to sensory input and emotional input when it comes to the release of milk.
In a study, it was shown that oxytocin levels rose even before suckling began. This was in anticipation of suckling like upon seeing or hearing the baby.
GH and Prolactin (the proteins and acidophiles) consume how much of the anterior pituitary’s volume?
75%
Somatotrophs are what
GH producing cells
How much of the anterior pit volume do they occupy
50%
What hormone increases GH excretion
T3
Lactotrophs do what
produce prolactin
Basophils occupy what percentage of pituitary volume>
15-20
