The Pituitary Gland Flashcards
Describe the hypothalamic communication with the pituitary gland
- Neural to the posterior pituitary
- Endocrine to the anterior pituitary gland
Describe the features of the hypothalamus
- Integration centre for the endocrine systems
- Located at the base of the brain
- Connected to the pituitary via a stalk
Describe the features of the pituitary gland
- Bean shaped and sized gland
- Located in a pocket in the sphenoid bone below the hypothalamus
- Contains two distinct types of tissue: anterior and posterior pituitary
List the key functions of the hypothalamus
-Cold
-Stress
-Metabolic demand
-Hydration
-Exercise
-Daylight
-Menstrual cycle
-Sleep
Breastfeeding
-Pregnancy
-Puberty
List the key functions of the pituitary gland
- Adrenal function
- Thyroid function
- Gonadal function
- Lactation
- Parturition
- Growth
- Water balance
- Metabolism
Name the two types of hypothalamic neurohormones
- Tropic: neurohormones secreted into capillaries travelling to the anterior pituitary
- Non-tropic: neurohormones produced in the hypothalamus and travel to the posterior pituitary where they are released into the blood
Name the five hypothalamic releasing hormones
- Thyrotropin Releasing Hormone (TRH)
- Corticotropin Releasing Hormone (CRH)
- Growth Hormone Releasing Hormone (GHRH)
- Gonadotrophin Releasing Hormone (GnRH)
- Prolactin Releasing Hormone (PRH)
Name the two hypothalamic inhibiting hormones
- Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin
- Dopamine aka Prolactin Inhibiting Hormone (PIH)
Describe the features of the hypothalamo-hypophyseal portal system
- Network of tiny vessels which transfer trophic hormones from the hypothalamus to the anterior pituitary
- Small numbers of neurosecretory neurons sufficient for control
- Hormones released from the neurosecretory neurons at the median eminence
- Very small amounts of hormone required
- Short distance
Describe the features of the anterior pituitary gland
- True endocrine tissue
- Epithelial origin
- Connected to the hypothalamus via the capillary portal system
- Also called adenohypophysis
- Makes up 2/3 of the gland
- Production of anterior pituitary hormones is controlled by hypothalamus (using the trophic hormones)
Describe the features of the posterior pituitary gland
- Neuroendocrine tissue
- Neural tissue origin
- Neural connection to the hypothalamus
- Secretes neurohormones made in the hypothalamus
- Also called neurohypophysis
- Makes up 1/3 of the gland
Name the six anterior pituitary hormones
- Thyroid Stimulating Hormone (TSH)
- Adrenocorticotrophic Hormone (ACTH)
- Follicle Stimulating Hormone (FSH)
- Lutenising Hormone (LH)
- Growth Hormone (GH)
- Prolactin
Name the sites of action of the anterior pituitary hormones
- Prolactin > breast (lactation)
- TSH > thyroid (TH release)
- ACTH > adrenal cortex (cortisol release)
- GH > liver (IGF-1 release and tissue metabolism)
- FSH and LH > gonads (regulation of reproductive function and sex hormone release)
Describe the anterior pituitary feedback control pathway
- Three integration centres: hypothalamus, anterior pituitary and target endocrine cell
- Hormones themselves act as negative feedback signal
- Long loop feedback: feedback from endocrine target
- Short loop feedback: feedback from the anterior to hypothalamus
Describe the posterior pituitary hormones
- Vasopressin/ADH and oxytocin
- These are synthesised in the magnocellular neurons in the hypothalamus
- Axons project down the infundibulum to the posterior pituitary and synapse directly onto the capillaries
- Activity in the neurons results in the release of ADH or oxytocin directly into the blood stream at the posterior pituitary
