Introduction to Nervous System 2

Question 1

What is the HPA axis?

Answer 1

The hypothalamic-pituitary-adrenal (HPA) axis is a:
* Complex system of neuroendocrine pathways & feedback loops involving the hypothalamus, pituitary gland & adrenal glands
* Its primary action is to regulate the stress response
* It is also a negative & positive feedback system to control physiological systems such as stress, digestion, immune function, reproductive function, mood, energy

Question 2

How does the HPA work?

Answer 2

When something stressful happens, your initial stress response is mediated by sympathetic nervous system (SNS).
* This causes the release of epinephrine (adrenalin) & norepinephrine (noradrenalin) from the adrenal medulla causing a physical response, eg heart rate increase
* About 10 seconds later, the HPA axis is stimulated
* Firstly the hypothalamus releases corticotropin-releasing hormone (CRH)
* This increases SNS activity to help cope with the stressor - & signals pituitary gland
* The anterior pituitary gland then releases adrenocorticotropic hormone (ACTH) into the bloodstream. ACTH binds to receptors of adrenal cortex to produce cortisol. Cortisol blood levels are detected by hypothalamus & hippocampus
* This creates a negative feedback loop to stop hypothalamus producing (CRH) so this leads to a shutting off of the stress response.

Question 3

Where and what are the adrenal glands? What do they do?

Answer 3

• The adrenal glands are located on top of kidneys
• Composed of 2 parts producing different hormones - cortex & medulla
• Adrenal glands job is to produce hormones to regulate your stress response, plus metabolism, immune system, blood pressure, stress response and other essential functions
• Adrenal cortex secretes cortisol, aldosterone, DHEA & androgenic steroids
• Adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline)

Question 4

What is cortisol?

Answer 4

Nearly all cells in the body have cortisol receptors so its effects are wide reaching
* Fight or flight responses
* Stimulates the liver to converts glycogen to glucose for energy release
* It ↑ blood pressure, heart rate, respiratory rate slows digestion

Also
* controls salt & water balance
* anti-inflammatory actions
* immune regulation
* memory formation
* blood pressure regulation
* circadian rhythm
* growth hormone regulation
* metabolism

Question 5

What is aldosterone?

Answer 5

Aldosterone
* Primary function to regulate blood pressure and pH
* Does this in two ways; signals kidneys & colon to increase sodium to bloodstream & amount of potassium released in your urine (blood pressure and pH via electrotlyte control); Increased sodium increases plasma water retention in your blood which increases blood volume
* Helps regulate blood pH by controlling electrolytes
* Part of renin-angiotensin-aldosterone system

Question 6

What is DHEA & Adrenergic steroids?

Answer 6

• DNEA is one of the most abundant steroid hormones
• Its an endogenous steroid hormone precursor for Testosterone, Oestrogen
• Androgens are a group of male sex hormones
• Testosterone is predominant androgen

All genders androgens help with
* Bone density, muscle development, puberty, red blood cell production, sexual desire & function

Males they contribute to:
* Deep voice (vocal cord lengthening), hair growth on the face, scalp, chest, underarms & genitals, sperm development

Females they contribute to:
* Converts androgen into oestradiol, which: regulates menstruation, aids conception and pregnancy, minimizes bone loss, stimulates pubic & underarm hair growth

Question 7

What are epinephrine (adrenalin) & norepinephrine (noradrenalin)?

Answer 7

• Epinephrine is both a Hormone (from adrenal glands) & a CNS neurotransmitter whic his a chemical transmitter
• Its part of acute stress response
• Work together
• Abnormal levels of ephinephrine is linked to many conditions

Epinephrine (adrenalin) is responsible for:
* Dilation of airways, vasoconstriction, reduce pain perception, increase strength, heightened awareness

Norepinephrine (noradrenalin) is responsible for:
* ↑heart rate, fat metabolism, ↑glucose availability, circadian rhythm, focus/attention

Question 8

What is acute versus chronic stress?

Answer 8

• Acute stress is a normal physiological response to event or situation for survival
• Our stress response system has not evolved however
• Chronic stress is a prolonged activation of stress response system and creates a ‘new normal’
• Ongoing elevated cortisol → levels reduced immune response & ↑ inflammation, ↑heart rate, blood pressure, respiratory rate, muscle tension.
• Sx low energy, low mood, sleep disturbances, MSK, change in appetite, difficulty focusing
• Can also lead to hypertension, heart disease, obesity, metabolic syndrome, type 2 diabetes, arthritis, addiction, mood disorders
• More recently its best to consider embracing stress rather than trying to eliminate all stress
• Stress resilience

Question 9

What is adrenal fatigue?

Answer 9

• Adrenal fatigue should not to be confused with adrenal insufficiency which is potentially fatal.
• Controversial topic as not a recognised medical condition in orthodox medicine
• But some GPs etc do recognise a correlation between hypocortisolism & some disease states
• Standard blood tests only look at extreme underproduction or overproduction of hormone levels
• In theory adrenal fatigue hard to identify - a syndrome (a group of symptoms) rather than disease
• Sub-clinical syndrome
• Some think it may be a failure of adrenals but others think a failure in communication system?

Question 10

How do you manage stress and adrenal fatigue holistically?

Answer 10

Managing stress & adrenal fatigue holistically
* Lifestyle advice - social connections, a sense of purpose etc have a huge impact on mental health.
* Refer to other professionals - CBT, mindfulness and meditation can help; we can refer on
* Herbal support - looking at nervines & HPA axis regulators (hormonal systems too)