Posterior Pituitary Hormones Flashcards
What are the divisions of the pituitary gland/hypophysis?
Anterior pituitary/Adenohypophysis
Posterior pituitary/Neurohypophysis
Embryological origin of anterior pituitary
Pharyngeal epithelium
Embryological origin of posterior pituitary
Neural tissue
Key hormones secreted from anterior pituitary
Growth Hormone (GH)
Adrenocorticotropic hormone/Corticotropic (ACTH)
Thyroid Simulating Hormone (TSH)
Leuteinizing Hormone (LH)
Follicle Stimulating Hormone (FSH)
Prolactin (PRL)
Key hormones secreted from posterior pituitary
Vasopressin/ADH
Oxytocin
Which nuclei supply the posterior pituitary?
Paraventricular nucleus
Supraoptic nucleus
Chemical structure of oxytocin and vasopressin
Both contain 9 amino acids
Two amino acids vary between oxytocin and vasopressin
Where is oxytocin synthesized?
Paraventricular nucleus
Where is vasopressin synthesized?
Supraoptic nucleus
How are the hormones transported to the posterior pituitary gland?
Through the hypothalamo-hypophysial tract
How are the posterior pituitary hormones transported around the body?
In combination with carrier protein neurophysin
What is the purpose of vasopressin?
Maintains blood pressure
Maintains serum osmolarity
What are the vasopressin receptors?
V1A
V1B
V2
Binding of ADH to V1A receptors have the effects of …
Increasing blood pressure
Platelet aggregation
V1A receptors
Pathway to raising blood pressure
V1A receptors
Pathway to causing platelet aggregation
What effect does V1B receptors have on the body?
Maintaining blood pressure
Pathway for V1B to maintaining BP
What effect does V2 have on the body?
Regulation of water reabsorption
Pathway for V2 to affect water reabsorption
ADH binds to V2 receptors
Causes phosphorylation of aquaporins
Aquaporins enable water reabsorption
Pathway for increasing ADH secretion
How is the effect of ADH reduced?
Cortisol inhibits ADH release from pituitary
ANP inhibits ADH effect on renal collecting ducts
What type of receptor are oxytocin receptors?
G protein-coupled receptors
What are the target tissues for oxytocin binding?
Breast
Brain
How does oxytocin affect the target tissue?
Mitogen-activated protein (MAP) kinase is activated
Signaling cascade causes altered gene expression
Describe oxytocin sensitivity in third trimester
Estradiol levels increase causing more oxytocin receptor sensitivity in preparation for labour
Describe response to oxytocin in first stage of labour
What is the synthetic form of oxytocin?
Pitocin
Purpose of pitocin
Initiate stronger contraction to hasten delivery
Used during postpartum hemorrhage to slow excess bleeding
Why does oxytocin secretion continue after delivery?
Enables continued uterine contraction in postpartum period to help uterus reach pre-pregnancy size
Pathway of oxytocin affecting breast milk secretion
What regions of the central nervous system can oxytocin affect?
Hypothalamus
Amygdala
Basal Ganglia
How does oxytocin affect the hypothalamus?
Reduces stress by CRH-ACTH-Cortisol Axis
Promotes nurturing and bonding behaviors
How does oxytocin affect the amygdala?
Reduces activity in the amygdala (Reduces fear, anxiety, and aggression)
How does oxytocin affect the basal ganglia?
Stimulates the ventral striatum which processes motivation and reward
Ventral striatum is activated by feelings of love, anticipation, and interpersonal social rewards
What other behavioural effects may oxytocin have?
Maternal-fetal bonding
Motivation and reward
Group decision-making and teamwork
Negative memories
Behavioral release (reduces pain associated with stress)
Sexual stimulation and orgasm
