Unit 5: Week 2 Flashcards
What is the pituitary gland?
It’s inferior to the hypothalamus and hangs from it via the pituitary stalk or infundibulum. It’s protected by the sphenoid bone. It’s also known as the master endocrine gland.
How does the posterior and anterior pituitary connect to the brain?
The posterior pituitary is connected to the hypothalamus via neurons.
The anterior pituitary is connected via a shared blood supply through the portal veins. There’s a network of three capillary beds, two of them are in the anterior pituitary, and one is in the hypothalamus.
The hypophyseal arteries supply blood to the hypothalamus and posterior pituitary. The hypophyseal take the hormone with the returning blood.
How does the hypothalamus interact with the pituitary?
Hypothalamic nuclei produce oxytocin and ADH and are stored in neurosecretory cells and the posterior pituitary, or neurohypophysis (arrive ready made)
The hypothalamus produces releasing and inhibiting hormones which act on the anterior pituitary or adenohypophysis to regulate hormonal release.
What is growth hormone?
A general metabolic, non-tropic hormone released by the adenohypophysis. It mainly targets long bones and skeletal muscle and is a major factor in determining final body size. It causes amino acids to form proteins and fat to be broken down into energy.
Hyposecretion during childhood leads to pituitary dwarfism. This is adolescent size but in proportion (another form of dwarfism is achondroplasia. This is where torso grows but limbs are out of proportion- long bones are affected).
Hypersecretion during childhood leads to gigantism- body grows above normal size but in proportion. Growth primarily in long bones. After puberty, hypersecretion leads to acromegaly, where the bones grow wider, you have a prominent brow, hands and feet more stumpy and shovel-like, wider tongue, mandible growth, soft tissue growth (liver), generally the result of a pituitary tumour. Slow progression.
What is prolactin (PRL)?
It’s a non-tropic hormone which stimulates and maintains milk production following childbirth. Men can have prolactin-secreting tumours and begin lactating.
What is adreocprtocotropic hormone (ACTH)?
A tropic hormone that regulates endocrine activity in the adrenal cortex. Weak effect on aldosterone, strong effect on cortisol.
What is follicle stiumilating hormone (FSH)?
A gonadotropic hormone which stimulates follicle development in ovaries. Egg is developed from a finite store. In testes, stimulates the development of sperm.
What is luteinizing hormone (LH)?
A gonadotropic hormone.
Ovulation- egg is released from ovaries into fallopian tubes.
Testes- testosterone production.
What’s common in all of the hormones in the anterior pituitary?
They’re all water soluble which means they can’t penetrate the lipid membrane of the cell, act via the second messenger system.
They’re mostly regulated through tropic hormonal stimuli and negative feedback loops with the anterior pituitary and hypothalamus.
What happens during the second messenger mechanism?
The hydrophobic plasma membrane doesn’t allow the hydrophilic hormone to enter so it attaches to receptor proteins.
G proteins on the inner surface of the membrane are activated and the alpha subunit dissociates and replaces its GDP with GTP.
The alpha subunit binds with adenylyl cyclase and activates it. It catalyses the conversion of ATP into cyclic AMP which binds and activates PKA which alters cellular function by going to the nucleus to alter gene expression.
First messenger-hormone
Second messenger-ANP.
What does oxytocin do (OXY)?
It’s an anterior pituitary hormone that stimulates contractions of the uterus during labour. It also stimulates feelings of attraction and causes the let down reflex in nursing women.
What is antidiaretic hormone (ADH)?
It inhibits urine production and aids reabsorption of water in the kidneys by increasing permeability of the distal convoluted tubual and collecting ducts.
High levels of ADH can cause vasoconstriction which is why it’s also known as vasopressin.
What are some tropic hormones released from the hypothalamus? 5 releasing 2 inhibiting
Releasing hormones:
- Growth hormone releasing hormone (GHRH)
- Thyroid releasing hormone (TRH)
- Gonadotropin releasing hormone (GnRH)
- Prolactin releasing hormone (PRH)
- Corticotropin releasing hormone (CRH)
Inhibitory hormones:
- Growth hormone inhibiting hormone (GHIH), aka somatostatin
Prolactin inhibiting hormone (PIH) dopamine
what is thyroid-stimulating hormone (TSH)?
Stimulates the grown and activity of the thyroid gland to release T4 and T3 (calcitonin is humoral stimuli). these act on negative feedback.
