Hypothalamus and Pituitary Gland

Hypothalamus

What does the hypothalamus form

walls and floors of the third ventricle

What does the hypothalamus regulate (3) and how

primitive funcitons - sex drive, water balance, thermoregulation

most funcitons carried out by the pituitary gland

Pituitary gland

Infundibulum → connects hypothalamus to posterior pituitary gland

What is another name for pituitary gland

hypophysis

What are the two lobes of the pituitary gland

anterior pituitary (adenohypophysis)

posterior pituitary (neurohypophysis)

2 main difference between anterior and posterior pituitary gland

anterior pituitary / adenohypophysis→ glandular tissue → creates and secretes its own hormones

vs

posterior pituitary / neurohypophysis → neural tissue → extension of hypothalamus → doesn’t create hormones only stores hormones from hypothalamus and release it

Hypothalamus has direct control over posterior lobe and indirect control over anterior lobe

how does Anterior pituitary / adenohypophysis connect to hypothalamus

through blood vessels of hypophyseal portal system

• hormones from hypothalamus travel to anterior pituitary via capillaries and veins

how does hypothalamus cause anterior pituitary gland to secrete hormones

hypothalamic neurons secrete releasing or inhibiting hormones into capillary plexus → if stimulated anterior pituitary secretes hormone into secondary capillary plexus → empties into general circulation

How does the posterior pituitary / neurohypophysis connect to hypthothalamus

neural connection

How does hypothalamus affect posterior pituitary

Hypothalamic nuclei (cell bodies) make neurohormones (oxytocin and ADH(antidiuretic hormones) ) → travel through axons through infundibulum to be stored in posterior pituitary

when hypothalamus cell bodies are stimulated → axons in posterior pituitary release hormone into blood stream

Which is an extension of the hypothalamus

posterior pituitary

What are the 6 hypothalamic hormones that regulate anterior pituitary

GnRH - gonadotropin releasing hormone

TRH - thyrotropin releasing hormone

CRH - corticotropin releasing hormone

PIH - prolactin inhibiting hormone

GHRH - growth hormone releasing hormone

GIRH / somatostatin - growth hormone inhibiting hormone

What are the 6 anterior pituitary hormones

1. GH - growth hormone / somatotropin

2. TSH - thyroid stimulating hormone / thyrotropin

3. ACTH - Adrenocorticotropic hormone - corticotropin

4. FSH - follicle stimulating hormone

5. LH - Luteinizing hormone

6. PRL - Prolactin

What are most of the anterior pituitrary hormones and which are the 2 exceptions

tropic hormones → hormones that stimulate other hormones

exceptions -growth hormones and prolactin

GH/ - which lobe

• what type of hormone is it

• what does it do (4)

• what cells does it stimulate

• when are they mostly released

• How are they regulated (2)

Growht hormone / somatotropin - anterior pituitary

• they are anabolic hormones → build tissues not break down

• stimulates mitosis; cell differentiation; encourage protein synthesis and use of fat for fuel instead of others;

• most cells but mainly bone and skeletal muscle

• More during puberty

• regulated by hypothalamic hromones (growth hormone releasing and growth hormone inhibiting hormone / somatostatin)

Gigantism vs acromegaly vs pituitary dwarfism

Gigantism - hypersecretion of GH/ somatotropin during childhood

acromegaly - hypersecretion of GH during adulthood (after epihphyseal plate closes)

pituitary dwarfism - hyposecretion of GH during childhood

TSH - which lobe

• what does it do

• how is it regulated

thyroid stimulating hormone - anterior pituitary

• stimulates development and secretory activity of thyroid gland

• negative feedback mechanism

  • thyroid hormone level in blood rises → inhibit anterior pituitary and hypothalamus

TSH pathway

Hypothalamus → thyrotropin releasing hormones → anterior pituitary gland → thyroid stimulating hormone/ thyrotropin → thyroid gland → thyroid hormone

ACTH - what lobe

• what does it do

• how is it regulated

adrenocorticotropic hormone/ corticotropin → anterior pituitary

• stimulates adrenal cortex to secrete corticosteroids (glucocorticoids)

• regulated by corticotropin releasing hormones from hypothalamus → negative feed back

ATCH pathway

Hypothalamus → corticotropin releasing hormones → anterior pituitary → adrenocorticotropic hormones / corticotropin → adrenal cortex → corticosteroids like glucocorticoid

FSH and LH - what are they + what lobe

• what are they secreted by

• what do each of them do

• 
  

follicle stimulating hormones & luteinizing hormone → gonadotropins - anterior pituitary

• secreted by gonadotrophs in anterior pituitary

• follicle stimulating hormones stimulate gamete production (egg sperm)

• luteinizing hormones promotes production of gonadal hormones (testosterone and progesterone)

Which hormones are absent from blood prepuberty

FSH (follicle stimulating hormone) and LH (luteinizing hormones)

Gonadotropins pathway

hypothalamus → gonadotropin releasing hormone → anterior pituitary → gonadotroph → FSH (follicle stimulating hormones) and LH (Luteinizing hormones) → testes and ovaries → eggs and sperm + gonadal hormones respectively

PRL - which lobe

• what is it secreted by

• what does it do

• how is it regulated

prolactin - anterior pituitary

• secreted by lactotrophs in anterior pituitary

• stimulates milk production in females

• prolactin levels in blood rise at end of pregnancy + suckling stimulates prolactin release continuing milk production

PRL pathway

hypothalamus → prolactin inhibiting hormone not secreted → anterior pituitary gland → lactotroph → prolactin → mammary glands → milk

Wbat are the two hypothalamic hormones stored in posterior pituitary and released on demand when the hypothalamic neurons are stimulated

ADH - antidiuretic hormone

OT - oxytocin

ADH - which lobe + how is it regulated

antidiuretic hormones - posterior pituitary

• hypothalamic osmoreceptor → change in concentration of solute in blood

  • when high solute concentration → ADH produced and released → ADH acts on kidney collecting ducts → water resorbed back into blood + inhibits urine (less urine produced)
    
    retains water when dehydrated / solute concentration is high

OT - which lobe + how is it regulated (when is it released, what 2causes it to be released )

oxytocin - posterior pituitary

• released during sexual arousal and orgasm

• stimulates uterine contraction during childbirth through positive feedback (contractions → more oxytocin → stronger contractions)

• Milk ejection/ letdown → infant suckling promotes oxytocin → bonding