Neuroendocrine & Hormonal Flashcards by Tasha Unknown

Where is hypothalamus

Above brainstem

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Where is pituitary gland

Base of brainstem

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What is difference between anterior vs posterior PG

Posterior: hypothalamus directly connected via stalk, neuronal tissue, ADH, Oxytocin

Anterior: hypothalamus connected via ME, pituitary portal blood system, hormonal release, requires releasing hormone, stores 2” hormones

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What is difference between anterior vs posterior PG

Posterior: hypothalamus directly connected via stalk, neuronal tissue, ADH, Oxytocin

Anterior: hypothalamus connected via ME, pituitary portal blood system, hormonal release, requires releasing hormone, stores 2” hormones

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What is difference between anterior vs posterior PG

Posterior: hypothalamus directly connected via stalk, neuronal tissue, ADH, Oxytocin

Anterior: hypothalamus connected via ME, pituitary portal blood system, hormonal release, requires releasing hormone, stores 2” hormones

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What does anterior and posterior PG have in common?

Triggered by neural stimuli

Hypothalamic neurons

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What can influence changes in neuroendocrine system?

Changes in receptor expression and binding tissues

Changes in hypothalamic nuclei hormone synthesis

Changes in ME / pituitary portal blood system storage

Changes in receptor binding ability

Changes in hormone clearance

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What are the 3 important hypothalamic hormones involved in ageing and state corresponding AP hormone

Thyroid
- TRH (thyroid releasing hormone)
- TSH (thyroid stimulating hormone)
- T4 (thyroxine)
- T3 (triiodothyronine)

Adrenal
- CRH (corticotrophin releasing hormone)
- ACTH (adrenocorticotrophic hormone)
- Cortisol (glucocorticoid)

Growth
- GRHR (growth hormone releasing hormone)
*Somatostatin
- GH (growth hormone)

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How is endocrine system controlled in hypothalamus via Anterior Pituitary

1) Neural Stimuli
2) Hypothalamic nuclei releasing X
3) X stored in ME
4) ME releases X to AP via Pituitary Portal Blood System
5) X stimulates AP to release stored 2” hormones (Y)
6) Y binds to receptors on tissues
*Negative feedback mechanisms to AP + Hypothamalus
*Hormonal clearance

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What are the 3 main systems involved in ageing with AP

Growth Hormone & IGF-1

Hypothalamus-Pituitary-Thyroid (HPT Axis)

Hypothalamus-Pituitary-Adrenal (HPA Axis)

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What are the two nuclei in posterior pituitary gland called

Supraoptic Nuclei

Paraventricular Nuclei

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What cells does TRH act on?

Thyrotrophs

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What cells does GHRH act on?

Somatotrophs

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What cells does CRH act on?

Corticotrophs

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What glands do GH, ACTH, TSH act on, respectively

GH on Brain, Muscle, Adipose

TSH on thyroid

ACTH on adrenals

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What is the main purpose of GH

Acts on BAM (Brain, Adipose, Muscle) to
- Stimulate growth
- Regulate growth
- Maintain growth
- Repair

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What is another name for GH

Somatotrophin

What is the hypophyseal portal system

Pituitary portal blood system, connects hypothalamus via ME to AP

What stimulates GRHR

Hypoglycaemia
Epinephrine
Exercise
Testosterone
Oestrogen

How is GHRH controlled?

[serum GHRH]

somatostatin (-ve feedback)

What is the action of somatostatin?

Inhibits GHRH

Inhibits pancreatic hormone release: glucagon, insulin, gastrin

What is the action of GH?

Increases cellular metabolism (O2/ATP) =

Adipose: lipolysis

Liver: Gluconeogensis, glycogenolysis

Muscle: increased AA uptake + protein production via IGF-1

Blood Glucose = increase blood glucose

Why is giving Growth Hormone leading to diseases?

Diabetogenic:
increases cellular metabolism= increased [blood glucose] = increased insulin resistance

Describe how IGF-1 relates to GH?

GH stimulates IGF-1 in liver to increase growth effect on BAM
- Cell division, decreased apoptosis, cellular metabolism

What is ageing effect on GHRH, GH & IGF-1

Somatopause = LESS recovery, repair, maintenance, impaired metabolism - GHRH decline in hypothalamus - GHRH: Somatostatin Ratio more equal = more inhibition GHRH - Somatotroph Cell size decrease = less GH = less IGF-1 - NO cicardian rhythm based GH release

What are the consequences of GH administration for ageing?

Increased CVD, Diabetes, Acromegaly, Hypertension - IGF-1 already imposes insulin resistance

Describe the HPA axis

1) Neural Stimuli 2) Hypothalamic nuclei release CRH 3) CRH stored in ME, released via hypophyseal portal system 4) AP: Corticotrophs release ACTH 5) ACTH cleaved act on adrenal to release Cortisol *Negative Feedback: Cortisol

What is the effect of Cortisol?

BREAKDOWN in STRESS Liver: glycogenolysis Protein: inhibits synthesis Immune System: anti-inflammatory

What are the receptors for Cortisol

GR, MR

Cortisol receptors in hippocampus

MR, GR

How does Cortisol affect memory in ageing?

Cortisol readily binds to MR more than GR in hippocampus Young: less cortisol, more bind to MR = beneficial for brain Old: more cortisol, binding to MR occurs AND binding to GR more = impairs memory

What are the 2 effects of ageing on HPA axis and what are the health effects?

Hippocampal atrophy / poor memory due to higher cortisol binding to GR in hippocampus neurons Decreased cortisol clearance = prolongs cortisol effect / less decline Increased risk of CVD, bone fractures due to lower BMD, adiposity increased due to increased appetite

Why does increased cortisol increased weight gain

Increased cellular metabolism (glycogenolysis, lipolysis, glycolysis) increases appetite

Is there a difference between men and women on HPA axis ageing?

Women are more effect, slower decline than men in cortisol

Describe HPT axis?

1) Neural stimuli 2) Hypothalamic nuclei release TSH 3) TRH stored in ME, released via hypophyseal blood system 4) TRH stimulates Thyrotrophs release TSH to release T4 in AP 5) T4 in liver deiodinase = T3 6) T3 acts on thyroid *T4 negative feedback

Why does elevated cortisol in ageing cause sleep disturbance?

Cortisol runs on cicardian rhythm, which it no longer does in ageing

What is the effect of T3?

Calorigenesis, ATP Lowers cholesterol Maintenance of NS, mental health, body temperature

What happens to HPT axis in healthy ageing?

TSH decreases T3 decreases T4 remains same

Why does T3 decrease and T4 remain same in ageing?

T3 decreases due to decreased deiodinase enzyme expression T4 remains same due to decreased hormonal clearance, not release

What are the detrimental effects of HPT ageing

Increased serum cholesterol Decreased calorigensis: CVD, T2D, Hypertension Hyperthyroidism: Grave's Hypothyroidism: Hashimotos