Hypothalamus Pituitary Axis

Question 1

Hypothalamus in Relation to Endocrine system

Answer 1

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

Question 2

Pituitary Gland Relation to Endocrine

Answer 2

2 distinct portions: anterior (adenohypophysis) and posterior (neurohypophysis)

Question 3

Neural Pathway Outline

Answer 3

Signal from hypothalamus to posterior pituitary. Neural (instantaneous release of hormones). Made of neurophysisns

Question 4

Vascular Link Outline

Answer 4

Signal from hypothalamus to anterior pituitary. Hypophyseal portal system (blood vessels between hypothalamus and pituitary gland). Chemical (slow release of hormones)

Question 5

Neuroseceretory Neurons Outline

Answer 5

Neurons in hypothalamus that produce and release hormones into blood

Question 6

Suparotic Neurons

Answer 6

Neurons in hypothalamus that Produce vasopressin and (little) oxytocin as prohormones (inactive)

Question 7

Paraventricular Neurons

Answer 7

Neurons in hypothalamus produces oxytocin, (less) vasopressin and corticopressin releasing hormone (CRH) as prohormones (inactive due to protein attached)

Question 8

Neurophysins Def

Answer 8

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

Question 9

Oxytocin Function

Answer 9

Mamary glands contract pushing milk into ducts and triggers uterine contractions in childbirth

Question 10

Oxytocin Release Outline

Answer 10

Made in paraventricular neurons, stored in posterior hypothalamus. Signals move down neorophysis to release into systemic circulation

Question 11

ADH Release During Dehydration

Answer 11

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

Question 12

Stimulants of ADH Release

Answer 12

Low blood vol, high blood conc and stress

Question 13

ADH Inhibitors

Answer 13

High blood vol, low blood conc and alcohol intake

Question 14

Examples of ADH Deficency

Answer 14

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)

Question 15

Hypothalamus and anterior pituitary releasing Outline

Answer 15

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

Question 16

How pituitary gland attaches to hypothalamus

Answer 16

Pituitary stalk

Question 17

Anterior Pituitary Cells

Answer 17

Gonadotropes (FSH and LH), corticotropes (adrenocorticotropic hormone), Thyrotropes (thyroid stimulating hormones), lactotropes (prolactin) and somatotropes (growth hormones). All hormones are excreted as peptides

Question 18

F.L.A.T. P. I G. (Hormones of Anterior Pituitary)

Answer 18

Folical Stimulating (reproduction), luteinizing Hormone (reproduction), adrenocorthitrpic hormone (stress) , Thyroid Stimulating Hormone, Prolactin and Growth Hormone

Question 19

Regulation of Anterior Pituitary

Answer 19

Hypothalamus and endocrine glands (except for prolactin which doesn’t act on an endocrine gland)

Question 20

Example of a Hypothalamic Hormone that works on 2 pituitary hormones

Answer 20

Prolactin inhibitory hormone acts like dopamine inhibiting thyroid stimulating hormone

Question 21

3 Types of feedback

Answer 21

short feedback loop, long feedback loop and ultra short feedback loop

Question 22

Long Loop Feedback Outline

Answer 22

Hormones from target gland travel to hypothalamus or pituitary to reduce their own production

Question 23

Short Loop Feedback Outline

Answer 23

Hormones from pituitary act on hypothalamus to reduce their own stimulating hormones

Question 24

Ultra Short Loop Feedback Outline

Answer 24

Hormones from Hypothalamus act on hypothalamus

Question 25

Stress Feedback Mechanism

Answer 25

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

Question 26

Thyroid Gland Hormones

Answer 26

T4 (Tyroxine), T3 (Triiodothyrine) and calcitoninin

Question 27

T3 and T4 Function

Answer 27

Brain and nervous system gowth and development. Regulate energy and metabolism

Question 28

Calcitonin Function

Answer 28

Helps regulate Ca levels in blood

Question 29

Thyroid Hormone Feedback Outline

Answer 29

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

Question 30

Other Hormone that inhibits thyroid hormone relaese

Answer 30

Somatostatin