Lecture 28

Question 1

Hypothalamic- pituitary adrenal axis

Answer 1

• Non stresss stimulus- day night rhythm, low blood gluclose
• hypothalamus secretes - in response to the stimulus, hypothalamus secrrtes CRH, corticotropin releasing hormone
• anterior pituitary gland secretes ACTH adrenocorticotropin hormone
• adrenal gland ( cortex ) secretes CORTISOL
• target and effects of cortisol
  = Liver, muscle and adipose; pancreas ( opposes insulin, stimulates glucangen )
  = cardiovascular system ( maintains normal blood pressure )
  = immune system ( suppresses/reduces inflammation to increase immunity )

Negative feedback: cortisol negatively feeds back to reduce realise of ACTH and CRH

Question 2

Daily pattern of cortisol secretion

Answer 2

• plasma cortisol concentration fluctuates in a 24 hour circadian rhythm
• cortisol is highest upon waking up form a sleep
• if normal sleep patterns are disturbed, it will affect the normal, pattern of cortisol release

Question 3

Adrenal gland location

Answer 3

• there are 2 adrenal gland
• they sit on top of the kidney

Question 4

Hormones of adrenal, gland

Answer 4

• cortisol - secreted form the cortex ( outer layer)
• aldosterone - secreted form the cortex ( outer layer )
• catecholamines - secreted from the medulla ( middle of adrenal gland )

Question 5

Target cell activation by cortisol

Answer 5

Cortisol is lipid soluble and is produced when required. So first it is diffused through membrane lipids
Carried in blood bound to a carrier protein
Detached from the carrier protein and enters the target cell
Cortisol binds to a receptor in the cytosol
Cortisol receptor complex enters nucleus and binds to DNA, binding to the hormone receptor complex to DNA
Activates specific genes to produce proteins. So this is when transcription and mRNA is produced
Proteins have effects, translation and protein synthesis
Response time; minutes - days

Question 6

Cortisol effects - normal ( non stress )

Answer 6

Increases blood ( gluclose ) by stimulating
- pancareas: to realises glucangon
- liver: to reduce gluclose intake from blood and create new glucose
- skeletal muscle: to reduce glucose intake from blood and increase protein breakdown
- adipose: to reduce gluclose intake from blood and increase fat breakdown
- maintain normal blood pressure
- supresses inflammation which boost overall immunity

Question 7

What are the phases/stages of stress response

Answer 7

• good health ( at homeostasis)
  Alarm stage
  Resistance stage
  Exhaustion stage

Question 8

Alarm phase. What does ur body do and how is that response helpful for dealing with the stressior

Answer 8

Fight or flight
For example, when you are being frightened
- jump scare
- bad news
- serious injury
- social situations

What does ur body do in response:
- increased breathing rate
- increased heart rate
- dry mouth

How is that response helpful with destling with the stressor
- increase oxygen intake
- increase oxygen and gluclose circulated to the brain and skeletal muscle
- reduce activation of unnecessary body functions ( digestive and saliva )

Question 9

Alarm phase - stress triggers the sympathetic nervious system

Answer 9

• the stress begins when distress signals ( APS) are sent to the hypothalamus from an emotion centre of the
  brain
• hypothalamus neurons are the control centre for both the sympathietic ( fight or flight ) and parasympathetic ( rest or digest ) nervous system
• stress triggers the hypothalamus to activate the sympathetic nervous system

Question 10

What is parasympathetic

Answer 10

Rest or digest nervous system

Question 11

What does the sympathetic nervous system’s do

Answer 11

Help deal with stress

Question 12

Alarm phase - sympathetic nerves stimulate catecholamine ( eg; adrenaline) secretion

Answer 12

Sympathetic nerves stimulate the adrenal gland ( medulla )
- to release adrenaline and noradrenaline into the main bloodstream
- to stimulate target cells to help the body deal with stress

Question 13

Alarm phase- adreanaline from adrenal medulla, location

Answer 13

We have 2 and they sit on top of the kidney

Question 14

Hormaones of adrenaline from adrenal medulla, alarm phase

Answer 14

• cortisol - secreted from cortex
• aldosterone- secreted from the cortex
• catercholamines - secreted from the medulla

Question 15

Alarm phase; target cell activation by catecholamines

Answer 15

Catecholamines are water soluble and travel in blood unbound
Bind to membrane receptors
Initiate actions of a second messenger system
Lead to amplification of cellular responses that help the body deal with stress
Response time - seconds to minutes

Question 16

Catecholamines effects

Answer 16

Increased rate of O2 and delivery of blood cells
Increases fuel released into the blood for cells to use

Question 17

Increased intake of O2 and delivery of blood into cells. Catecholamine effects

Answer 17

Lungs - increased rate of breathing. Airway dilation is wider
Heart - heart rate and strength of contraction
Blood vessels - blood pressure

Question 18

Increased fuel release into the blood for cells to use

Answer 18

Liver - glycogen breakdown ( glycogenolysis )
Skeletal muscle - glycogen breakdown ( glycogenolysis )
Adipose - Fat breakdown ( lipolysis )

Question 19

How does the alarm phase change to resistance phase

Answer 19

Alarm
- if the stress is removed, the alarm phase ends, adrenaline release stops and the body enters the recovery phase
- the glycogen that is stored in liver and muscle are replenished
- heart rate and blood pressure return to normal

However jf the stress continues the body enters the resistance phase

Resistance phase
- gluycogen reserves were deplkcted in the alarm phase so lipid and protein stores need to be mobilised in the resistance phase

Question 20

The resistance phase overview

Answer 20

This is when the body is working to resist the effects of the stress
- occurs when stress last longer then a few hours
- cortisol is the dominant hormone of the resistance phase
- other hormones also play important role

Question 21

Resistance phase, key actions and hormones

Answer 21

Fuel metabolism into blood
- cortisol ( from adrenal cortex )
- glucagon ( from pancreatic alpha cells )
- adrenaline ( from adrenal medulla )
- growth hormone ( from anterior pituitary)

Increased blood pressure
- cortisol ( from adrenal cortex)
- ADH ( from posterior pituitary)
- aldosterone ( from adrenal cortex )

Suppressed reduction inflammation
- cortisol ( from adrenal cortex )

Question 22

Fuel metabolism in blood plasma. Resistance phase

Answer 22

• energy demands are higher than normal - to deal with stress
• most hormones secreted in the resistance phase ( ie, cortisol, glucagon, adrenaline, GH ) act to increase fuel in plasma
• fats from adipose and amino acids from skeletal muscles are mobilised for non neural cells to use
• gluclose is mobilized primarily for neural tissue to use

Question 23

Increased blood pressure, resistance phase

Answer 23

Ensuring that blood can be directed into organs where it is needed most ( brain )
- ADH ( from posterior pituitary) stimulates vasoconstriction of blood vessels and also stimulates the kidney reasonable more water into plasma
- aldosterone ( from adrenal cortex) stimulates the kidney to reabsorb more Na+ into plasma

Vasoconstriction and isosmotic fluid ( water and Na+ ) retention increases plasma volume, both which increases blood pressure

Question 24

From resistance to exhaustion

Answer 24

Resistance phase
- the body lipid reserves can maintain resistance phase for weeks or even months
- if body stays in this phase for too long the homeostatic regulation breaks down causing the body to enter thr excusaion phase

Question 25

Exhaustion phase overview

Answer 25

Can last for weeks or even years however is Varys by individual and causes of stress Eventually the body’s compensatory responses are inadequate to sustain health as energy reserves are depleted Oftern requires medical intervention Common deseases states linked to prolonged stress: chronic high blood pressure, stroke, heart attack, autoimmune disease

Question 26

Exhaustion phase

Answer 26

- when lipid reserves are depleted, organs begin to get damaged as structural proteins are broken down - cardiovascular and immune system damage, and inability to regulate plasma glucose and ion concentrations lead to organ failure - medical intervention is required