Theory L8 - Biochemical Perspective 2 Flashcards
What is Epigenetics?
Changes in the phenotype without changes in the genotype - NO GENETIC MUTATION.
Changes are due to changes in chemical environment - eg. methylation if DNA causing for the protein to be expressed or not.
- Thought to be how cells terminally differentiate, and how diseases develop.
- TURNS GENES OFF AND ON
What is DNA methylation?
when DNA is methylated, strands cannot separate from each other, and information cannot get out - thus, no protein is made.
DE-METHYLATION - results in protein being made - some times this extra protein is not needed = DANGEROUS.
What are 3 ways epigenetics happens?
- dna methylation
- histone modification
- non-coding RNA associated gene silencing - these moderate gene expression - if they aren’t there, a protein may not be expressed / or silenced and thus create problems!!
What are some epigenetic diseases?
- Cancer
- Neuropsychiatric disorders - Scz, Mood Disorders, Neurodegenerative disorders (AD), Autism (chr 15)
- Fetal Alcohol Syndrome
What are instances where epigenetic disease can occur
- hormonal influences - the pill
- alcohol during pregnancy
- stressed mother
What are the two systems involved in stress?
- Autonomic NS - quick, direct connection between adrenal medulla and hypothalamus.
- Endocrine system
Describe the biological systems involved in stress.
Direct connections between hypothalamus and adrenal medulla lead to hormone supply of adrenaline and noradrenaline.
These lead to different bio changes in the body, and has a -ve feedback loop to prevent extra production of these hormones.
endocrine responses are slower, but their effect lasts longer - cortisol and other glucocorticoids - measured in saliva.
ANS divisons?
Sympathetic - increase HR, increase respiration o2, increased BP
Parasympathetic - digestion, slow HR,
effects of arousal works SYNERGISTICALLY - work together not against.
What is the two-system view of stress response?
Stressor –> Brain–>
- anterior pituitary > adrenal cortex > glucocorticoids
- Symp NS > adrenal medulla > norepinephrine & epinephrine.
2 different responses. one quick one slow.
What are catecholamines?
- released from adrenal medulla following SNS
- NA (associated with physical stress) and Adrenaline (associate with psychological stress) - Type of stress results in different concentrations of the hormones
What does the release of catecholamines trigger?
- CNS arousal (alertness)
- Muscle contraction
- Cardiac output
- Blood pressure
- Oxygen consumption
^ these are secondary effects - measure these if you can’t measure the hormone itself.
- mobilises glucose stores
- inhibition of gastrointestinal and sexual activity.
What are corticosteroids?
they are the slow endocrine response to stress.
- these hormones are secreted by endocrine system, by the adrenal glands in response to stress.
- response to the kind of stress that is - novel, uncertain, unpredictable, helpless and distressing - BOTH psychological and physical.
- GLUCOCORTICOIDS (CORTISOL) , MINERAL CORTICOIDS
provides body with glucose energy
What do corticosteroids achieve in the body?
Mineralcorticoids
- Regulation of ion concentrations.
Glucocorticoids (Cortisol)
- Increase glucose by increasing metabolism of carbohydrates, proteins and fats.
Chronic secretions can have detrimental effects:
- Inhibits immunity (stomach ulcers, illness).
- High levels destroy hippocampal neurons.
Why is it important to use both objective and subjective measures of stress?
Objective measures are good.
However, people vary in levels of stress. The subjective experience of a situation may differ across people. Need to make sure that what you are actually measuring, is stress. - use self report scales to make sure the two experimental groups aren’t too different due to participant variables.
- biopsychosocial model
Can investigate the interactions between objective and subjective experiences of stress.
what are some patterns of hormone responses?
- With repeated exposure to a stressor, the increase in stress will diminish.
- Some hormones will increase AFTER the stressor - due to slow response - EPINEPHRINE
- CORTISOL may also increase AFTER stressor on the first time - because the individual will not have known how stressful the situation was going to be. Couldn’t anticipate, so got stressed. but stress response will DECREASE with repeated exposure
- NOREPINEPHRINE decreases with repeated exposure
- TESTOSTERONE increases with repeated exposure, but decreases after the actual jump in every trial
- growth hormone decreases with repeated exposure, but decreases after actual jump in every trial
What are some methods for eliciting stress?
- mental arithmetics - but need to use an incentive
- cold water hand for 3 mins
What can we measure stress with in the endocrine system?
Cortisol.
What can we measure stress with in the ANS?
- Epinephrine and Norepinephrine
- salivary alpha amylase - an enzyme which correlates with epinephrine.
- Can also measure SECONDARY MEASURES.
What are secondary measures? Limitations?
- These are indirect measures of an increase in NA or A.
- eg. BP, HR.
Limitations:
- does not determine the exactly increase in NA or A - simply indicates activation of the NS.
- If you don’t do these at the exact optimal time, it can change very quickly, so may miss the increase.
- Leads to research inconsistencies.
- so BEST to have multiple measurements over time to INCREASE RELIABILITY.
What is the limitation of measuring alpha amylase?
- The amount changes with salivary flow.
- Best to just measure HR for the whole time.
How do you measure CHRONIC STRESS?
- Measure cortisol in the morning. It will be increased.
- High cortisol awakening response = chronically stressed- normally LOW immediately after waking, due to circadian rhythm of cortisol.
- it sharply increases within half hour, and so the participant needs to take it at the RIGHT time.
- Maybe get them to take one sample when waking up and one 30 mins later to look at the INCREASE!! This is what is done NOW :)
- BLUNTED STRESS RESPONSE - show less awakening response due to exhaustion in the body. cant produce enough cortisol.
How do you measure acute stress?
- measure pre & post.
- Easier - used with many validated stressors.
How long does it take for chronic stress system exhaustion?
Years.
Blunted cortisol awakening response!!!!!
indicates large level of chronic stress.
What is the best time during day to measure cortisol/
Between 2pm-6pm
this is the time when cortisol levels are most levelled.
Everything shifts according to when they wake up and then according to circadian rhythm
Describe the circadian rhythm of cortisol?
*assuming their wake at 8am
- sharp increase when waking
- sharp decrease throughout morning after peak is reached.
- somewhat stable until 8pm?
- decreases throughout night till sleep.
Is acute stress related to cell loss?
No
only chronic stress
Steps to answering a question?
- Identify whether it is an animal or human study
- Write a Method
- Identify the sample to get the data
- lab methods to get data - Control group? Manipulation Check?
- What would the results mean?
