4. Hypothalamus and the pituitary Flashcards
name of the structure that connects HYPOTHALAMUS and PITUITARY (POSTERIOR)
INFINDIBULUM
what is the HYPOTALAMUS ANATOMICALLY
a collection of NEURONS
what is the HYPOTALAMUS PHYSIOLOGICALLY
a master CONTROL CENTRE
- orchestrates coordinated responses from brain, endocrine system & autonomic nervous system
HYPOTHALAMUS INPUTS
- BRAIN STEM
- CEREBREL CORTEX
- LIMBIC SYSTEM
- NON-NEURAL INPUT: osmolality, BP, Endocrine feedback
- SENSORY INPUT: temperature, pain, smell, light
HYPOTALAMUS OUTPUTS
- BRAIN STEM, SPINAL CORD
- CEREBRAL CONRTEX THALAMUS
- PITUITARY AND HORMONES
- AUTONOMIC NERVOUS SYSTEM
-TEMPERATURE, SLEEP, THIRST, APPETITE
PITUITARY GLAND WEIGHT
0.5 GRAMS
what does PITUITARY SIT WITHIN
SELLA TURCICA / PITUITARY FOSSA
saddle-shaped depression of the sphenoid bone of the skull
PITUITARY connected to HYPOTHALAMUS via
PITUITARY STALK / INFINDIBULUM
BLOOD VESSEL NETWORK (hypothalamo-hypophyseal-portal system)
3 parts of ANTERIOR PITUITARY
- PARS TUBERALIS - surrounds infundibulum
- PARS INTERMEDIA
- PARS DISTALIS - full lobe
2 parts of POSTERIOR PITUITARY
- INFUNDIULAR STALK
- PARS NERVOSA
what is OPTIC CHIASM
part of the brain where the optic nerves cross
anterior to & above/superior to PITUITARY
relationship between PITUITARY and OPTIC NERVES
2 OPTIC NERVES CROSS ABOVE PITUITARY
(optic chiasm)
therefore pituitary growth can compress and cause visual disturbance
what is around the PITUITARY
CAVERNOUS SINUS (right & left)
what does the CAVERNOUS SINUS contain
- CRANIAL NERVES:
OCULOMOTOR
TROCHLEAR
ABDUCENT
OPTHALAMIC
MAXILLARY - CAROTID ARTERY
CRANIAL NERVES in CAVERNOUS SINUS
OCULOMOTOR
TROCHLEAR
ABDUCENT
OPTHALAMIC
MAXILLARY
(can get squashed if lateral growth of pituitary)
what is ANTERIOR PITUITARY DERIVED from (embryology)
ECTODERM of RATHKE’S POUCH
what is POSTERIOR PITUITARY DERIVED from (embryology)
downward extension of NEURAL ECTODERM from the floor of the DIENCEPHALON
GHRH (Growth Hormone Releasing Hormone)
from HYPOTHALAMUS acts on which PITUITARY CELLS,
which PITUITARY HORMONE is secreted,
to which TARGET GLANDS,
RESULT
SOMATOTROPHS
GROWTH HORMONE
BONE, LIVER, ADIPOSE, MUSCLE
IGF-1, GROWTH, METABOLIC FUNCTION
CRH - Corticotrophin Releasing Hormone
from HYPOTHALAMUS acts on which PITUITARY CELLS,
which PITUITARY HORMONE is secreted,
to which TARGET GLANDS,
RESULT
CORTICOTROPHS
ACTH - Adrenocorticotrophic hormone
ADRENAL GLAND CORTEX
CORTISOL & ANDROGENS synthesis/release
TRH - Thyrotrophin Releasing Hormone
from HYPOTHALAMUS acts on which PITUITARY CELLS,
which PITUITARY HORMONE is secreted,
to which TARGET GLANDS,
RESULT
THYROTROPHS
TSH - Thyroid Stimulating hormone
THYROID
THYROID HORMONE T3,T4 synthesis/release
GNRH - Gonadotrophin releasing hormone
from HYPOTHALAMUS acts on which PITUITARY CELLS,
which PITUITARY HORMONE is secreted,
to which TARGET GLANDS,
RESULT
GONADOTROPHS
FSH, LH
OVARIES, TESTES
ESTROGEN, PROGESTERONE, TESTOSTERONE
EGG/SPERM production
TRH ?
from HYPOTHALAMUS acts on which PITUITARY CELLS,
which PITUITARY HORMONE is secreted,
to which TARGET GLANDS,
RESULT
LACTOTROPHS
PROLACTIN
BREAST
Direct Action, MILK production
what is secreted by HYPOTHALAMUS to INHIBIT GROWTH HORMONE secretion by PITUITARY
SOMATOSTATIN
what are PERIPHERAL STIMULUS are GHRH
STRESS
EXERCISE
HYPOGLYCAEMIA
MALNOURISHED
SEPSIS
GROWTH HORMONE acts on (4)
- LIVER :
IGF-1 - GROWTH PLATE (BONES):
growth - ADIPOSE TISSUE:
lipolysis - MUSCLE:
less glucose uptake
more protein synthesis
IGF-1 (INSULIN LIKE GROWTH FACTOR) is secreted by
LIVER
STIMULATED BY GROWTH HORMONE
most of the EFFECTS of GH on peripheral tissues is mediated by
IGF-1
why is IGF-1 measured in blood samples
long half life
stable marker
unlike pulsatile secretion of GH
what is used for DIAGNOSIS of GH ABNORMALITIES
PLASMA LEVELS of IGF-1
predominant FUNCTION of GH in children
LINEAR GROWTH
EFFECTS of GH on ADIPOSE TISSUE
LIPOLYSIS
EFFECTS of GH on MUSCLE
DECREASED GLUCOSE UPTAKE
INCREASED PROTEIN SYNTHESIS
EFECTS of GH on LIVER
release of IGF-1
increased GLUCONEOGENESIS
increased GLYCOGEN SYNTHESIS
in GROWTH HORMONE REGULATION what is the SHORT LOOP
when EXCESS GH
sends NEGATIVE signal to hypothalamus to DECREASE GHRH secretion
decrease GH
in GROWTH HORMONE REGULATION what is the LONG LOOP
using IGF-1 and FREE FATTY ACIDS (from lipolysis) sends NEGATIVE SIGNAL to hypothalamus
to DECREASE GHRH / INCREASE SOMATOSTATIN so less GH
in GROWTH HORMONE REGULATION what is the OPEN NEURAL LOOP
when HYPOGLYCAEMIA and uses GHRELIN to send POSITIVE SIGNAL for MORE GHRH
more GH (stress response)
EFFECT of PROLACTIN
STIMULATES BREASTS to PRODUCE MILK
lactating hormone
when are PROLACTIN LEVELS HIGHEST
PREGNANCY & POST CHILD-BIRTH in preparation for breast-feeding
what STIMULATES RELEASE of PROLACTIN
some positive affects of TRH (hypothalamus)
SUCKLING
what has INHIBITORY EFFECTS on PROLACTIN release
DOPAMINE (hypothalamus)
lack of dopamine = increase prolactin
INCREASED PROLACTIN has negative effects on
GONADOTROPHINS (sex hormones)
(infertility)
CORTISOL STIMULUS
STRESS,
SEPSIS,
HYPOGLYCAEMIA,
HYPOTENSION,
SURGERY
how is CORTISOL released from ADRENAL CORTEX (zona fasciculata)
CRH from HYPOTHALAMUS
ACTH from PITUITARY
LOW CORTISOL can be
LIFE-THREATENING
what does CORTISOL act on
BRAIN
HEART
BONE
KIDNEYS
MUSCLE
LIVER
ADIPOSE TISSUE
IMMUNE REGULATORY FUNCTION
EFFECTS of CORTISOL on BRAIN
COGNITIVE FUNCTION
MEMORY
SLEEP
MOOD
EFFECTS of CORTISOL on BONE
INHIBITS OSTEOBLASTS
(high cortisol can cause weakening of bones & osteoporosis)
EFFECTS of CORTISOL on HEART
MAINTAINS BLOOD PRESSURE
INCREASES CARDIOVASCULAR REACTIVITY (to maintain BP)
(low cortisol can cause hypotension)
EFFECTS of CORTISOL on KIDNEYS
INCREASES GLOMERULAR FILTRATION RATE
& WATER EXCRETION
EFFECTS of CORTISOL on ADIPOSE TISSUE
stimulates LIPOLYSIS
- increases free FATTY ACIDS
(excess cortisol, high ffa, toxic)
EFFECTS of CORTISOL on MUSCLE
INCREASES PROTEIN BREAKDOWN
inhibits protein synthesis
EFFECTS of CORTISOL on LIVER
INCREASES GLUCOSE LEVELS BY
GLUCONEOGENESIS
GLYCOGENOLYSIS
IMMUNE EFFECTS of CORTISOL
IMMUNOLOGICAL & INFLAMMATORY RESPONSES
when are CORTISOL levels HIGH
MORNING (8-9am)
low at night
THYROID HORMONE ACTIONS
HEART:
INCREASED HEART RATE & CARDIAC OUTPUT
BONE:
INCREASED BONE TURNOVER & RESORPTION
GI:
INCREASED GUT MOTILITY
METABOLIC RATE, BODY WEIGHT REGULATION
promotes GLUCOSE UPTAKE
INCREASES LIPOLYSIS
SYMPATHETIC NERVOUS SYSTEM:
INCREASED CATECHOLAMINE SENSITIVITY
FUNCTIONS of GONADAL AXIS in WOMEN
- PUBERTAL CHANGES
- DEVELOPING SECONDARY SEXUAL CHARACTERISTICS
- MENSTRUAL CYCLE
- FOLLICULAR GROWTH in ovaries
- OVULATION
- FERTILITY
- BONE MINERALISATION
FUNCTIONS of GONADAL AXIS in MEN
-PUERTAL CHANGES
- MASCULINITIY
- SEXUAL FUNCTION
- LIBIDO
- ERECTILE FUNCTION
- SPERMATOGENESIS
- BONE MINERALISATION
- MUSCLE STRENGTH
- ENERGY LEVELS
HORMONES in POSTERIOR PITUITARY
does NOT produce hormones
- STORES HORMONES from HYPOTHALAMUS
(neurons travel down from SUPRAOPTIC NUCLEUS and PARAVENTRICULAR NUCLEUS)
2 IMPORTANT NUCLEI in HYPOTHALAMUS used for STORAGE of hormones in POSTERIOR PITUITARY
SUPRAOPTIC NUCLEUS
PARAVENTRICULAR NUCLEUS
2 HYPOTHALAMUS HORMONES STORED in POSTERIOR PITUITARY
- OXYTOCIN
- VASOPRESSIN
VASOPRESSIN aka
AVP - Arginine Vasopressin
ADH - Anti-Diuretic Hormone
AVP/ADH/VASOPRESSIN acts on
KIDNEYS
AVP/ADH/VASOPRESSIN on KIDNEYS action
CONSERVES BODY WATER
& regulates overall BODY VOLUME STATUS
- aquaporins REABSORB water
when is AVP/ADH/VASOPRESSIN release stimulated
REDUCTION IN BODY VOLUME/FLUID
eg dehydration, diarrhoea
how is AVP/ADH/VASOPRESSIN stimulated when there is REDUCTION in BODY VOLUME/FLUID
-INCREASED plasma OSMOLALITY
(concentration of dissolved particles in your blood/ less water)
- activates Hypothalamic OSMORECEPTORS / BARORECEPTORS
what in the HYPOTHALAMUS detect INCREASED PLASMA OSMOLALITY
OSMORECEPTORS & BARORECEPTORS
- release AVP/ADH
LOW AVP/ADH:
when too much water in system
more WATER EXCRETION
increased PLASMA OSMOLALITY causes
THIRST
& AVP for WATER REABSORPTION
when is OXYTOCIN (stored in posterior pituitary) useful
in CHILD BIRTH and LACTATION
what does OXYTOCIN STIMULATE during CHILD BIRTH (PARTURITION)
MYOEPITHELIAL CONTRACTIONS in UTERUS
what does OXYTOCIN also STIMULATE
(besides contractions in uterus)
MILK EJECTION from lactating MAMMARY GLANDS
(suckling major stimulus for release)
