Hypothalamus Pituitary Axis Flashcards
Hypothalamus in Relation to Endocrine system
Connects with many regions of brain and spinal cord integrating signals to act as interface between body’s internal (homeostasis) and external (emotions, apetite, ect) environment
Pituitary Gland Relation to Endocrine
2 distinct portions: anterior (adenohypophysis) and posterior (neurohypophysis)
Neural Pathway Outline
Signal from hypothalamus to posterior pituitary. Neural (instantaneous release of hormones). Made of neurophysisns
Vascular Link Outline
Signal from hypothalamus to anterior pituitary. Hypophyseal portal system (blood vessels between hypothalamus and pituitary gland). Chemical (slow release of hormones)
Neuroseceretory Neurons Outline
Neurons in hypothalamus that produce and release hormones into blood
Suparotic Neurons
Neurons in hypothalamus that Produce vasopressin and (little) oxytocin as prohormones (inactive)
Paraventricular Neurons
Neurons in hypothalamus produces oxytocin, (less) vasopressin and corticopressin releasing hormone (CRH) as prohormones (inactive due to protein attached)
Neurophysins Def
Nerve fibres that carry signals from hypothalamus to posterior pituitary. This triggers a release of prohormones into blood. The protein separates from the hormone in the blood activating hormone
Oxytocin Function
Mamary glands contract pushing milk into ducts and triggers uterine contractions in childbirth
Oxytocin Release Outline
Made in paraventricular neurons, stored in posterior hypothalamus. Signals move down neorophysis to release into systemic circulation
ADH Release During Dehydration
Less water results in higher blood conc (higher osmolarity). Osmoreceptors in hypothalamus signal ADH production in neurosecretory cells and storage in posterior pituitary. Signals down nurphysis results in ADH being released into systemic circulation. ADH retains water causing high conc, low vol urine. When osmoreceptors sense a lowering in osmarility ADH production decreases
Stimulants of ADH Release
Low blood vol, high blood conc and stress
ADH Inhibitors
High blood vol, low blood conc and alcohol intake
Examples of ADH Deficency
Diabetes Insipidus. Central: Due to brain injuries/tumours/autoimmune disorders, brain doesn’t produce enough ADH. Nephrogenic: due to genetics or drugs kidney doesn’t respond to ADH. Symptoms are polyuria and polydipsia (excessive thirst). Can only be treated when central (given ADH)
Hypothalamus and anterior pituitary releasing Outline
Hypothalamic produces stimulating/inhibitory hormones. These are released into hypothalamus hypophyseal portal system, travelling to anterior pituitary. Anterior pituitary receives signal to stimulate/prevent hormone release into secondary capillary plexus
How pituitary gland attaches to hypothalamus
Pituitary stalk
Anterior Pituitary Cells
Gonadotropes (FSH and LH), corticotropes (adrenocorticotropic hormone), Thyrotropes (thyroid stimulating hormones), lactotropes (prolactin) and somatotropes (growth hormones). All hormones are excreted as peptides
F.L.A.T. P. I G. (Hormones of Anterior Pituitary)
Folical Stimulating (reproduction), luteinizing Hormone (reproduction), adrenocorthitrpic hormone (stress) , Thyroid Stimulating Hormone, Prolactin and Growth Hormone
Regulation of Anterior Pituitary
Hypothalamus and endocrine glands (except for prolactin which doesn’t act on an endocrine gland)
Example of a Hypothalamic Hormone that works on 2 pituitary hormones
Prolactin inhibitory hormone acts like dopamine inhibiting thyroid stimulating hormone
3 Types of feedback
short feedback loop, long feedback loop and ultra short feedback loop
Long Loop Feedback Outline
Hormones from target gland travel to hypothalamus or pituitary to reduce their own production
Short Loop Feedback Outline
Hormones from pituitary act on hypothalamus to reduce their own stimulating hormones
Ultra Short Loop Feedback Outline
Hormones from Hypothalamus act on hypothalamus
Stress Feedback Mechanism
Hypothalamus releases Corticotropin Stimulating Homone. This travels through hypothalmic - hypophyseal portal system stimulating anterior pituitary to produce adrenocorticotropic hormone. This travels in systemic circulation to adrenal glands which release cortisol. High cortisol levels signal pituitary and hypothalamus to stop releasing adrenocorticotropic hormone and corticotropic stimulating hormone
Thyroid Gland Hormones
T4 (Tyroxine), T3 (Triiodothyrine) and calcitoninin
T3 and T4 Function
Brain and nervous system gowth and development. Regulate energy and metabolism
Calcitonin Function
Helps regulate Ca levels in blood
Thyroid Hormone Feedback Outline
Hypothalamus releases thyrotropin release hormone. This travels in hypothalmic hypophyseal portal system until it reaches anterior pituitary. Anterior pituitary releases thyroid stimulating hormones. This travel in circulation until it reached thyroid releaseing T3 and T4. High T3 and T4 send signals back to hypothalamus and pituitary to stop releasing thyrotropin stimulating hormone and thyroid stimulating hormone
Other Hormone that inhibits thyroid hormone relaese
Somatostatin
