PHYSIOLOGY OF STRESS AND ANXIETY Flashcards
what is stress?
Any condition that actually or potentially poses a challenge to the body’s ability to maintain homeostasis.
what is eustress?
Mild stress that is useful. Prepares us to meet challenges, is helpful and improves performance e.g. giving a speech
what is distress?
Unpleasant or disease producing stress that can impair performance e.g. death of family member
what is a stressor?
Any stimulus that produces a stress response
what are external stressors?
physical environment, social interactions, organisation e.g. rules, major life events, daily hassles
what are internal stressors?
lifestyle choices
negative self talk
mind
personality traits e.g. perfectionist
what is the general adaptation syndrome?
Physiological response to stressors in an attempt to regain homeostasis
what are the stages of the stress response?
- Alarm phase (short-term stress response): Initial ‘fight-or-flight’ response
- Resistance or adaptation phase (long-term stress response): Body attempts to cope with prolonged stress
- Exhaustion phase: Resources are depleted - body unable to maintain function
describe the short term stress pathway?
Stress activates cerebral cortex which activates the hypothalamus. this then activates the sympathetic nervous system which activates the adrenal medulla causing the release of catecholamines (adrenaline and noradrenaline)
describe the long term stress pathway?
Stress activates cerebral cortex which activates the hypothalamus
which then release CRH which activates the anterior pituitary gland to secrete ACTH. ACTH then travels through the blood to adrenal glands which are stimulated to release cortisol
what are the sympathetic responses to short term stress?
Increase heart rate Increase blood pressure Blood diverted to heart and skeletal muscles, away from nonessential organs (digestive, reproductive, urinary) Dilation of airways (increase oxygen) Conversion of glycogen to glucose in liver Metabolic rate increases Alertness increases Sweating (cooling)
what is CRH?
corticotropin releasing hormone
what is ACTH?
adrenocorticotropic hormone
what are the effects of cortisol on the body?
Lipids released into blood
Amino acids/proteins released from muscles into blood
Increase in glucose in blood, through synthesis from lipids and proteins
Aldosterone released by adrenal cortex causes retention of sodium, increased water retention, increased blood pressure
Leads to immune suppression by suppressing number of WBCs
why does cortisol cause release of lipids and proteins into the blood?
to synthesise glucose as all glycogen stores are used up. this is important for maintaining energy reserves for cells to be able to continue working
what is psychoneuroimmunology?
Looks at interactions between the nervous system, behaviour and the immune system
describe the effect of stress on the immune system?
Acute stressors can upregulate the immune system, but chronic stress inhibits the immune system
how does cortisol inhibit the immune system?
by decreasing B and T cell numbers
how can we use the fact that stress impacts the immune system to our advantage?
We can use glucocorticoids as anti-inflammatory and immunosuppressive agents
what are some effects of excessive stress?
Anxiety disorders/depression High blood pressure Ulcers/gastrointestinal diseases Immune dysfunction Aging Cancer Increase the frequency and severity of migraine headache, asthma attacks, and blood sugar fluctuations in diabetics Suppression of sex steroid secretion
when does the body enter the exhaustion stage?
when resources of the body become so depleted that they cannot sustain the resistance phase
what does prolonged exposure to high levels of cortisol cause?
o Muscle breakdown (as being used for glucose) o Suppression of immune response o Ulceration of gastrointestinal tract o Depression / psychosis o Failure of pancreatic beta cells o Aging even death
what is the function of the amygdala?
it is involved in the fear response
what happens when the central nucleus in the amygdala is activated?
The hypothalamus is activated which then activates the HPA and the sympathetic nervous system
The periaqueductal grey matter is activated which leads to avoidance behaviour
The diffuse modulatory systems is activated which increased vigilance
describe the effect of the amygdala and the hypothalamus on the HPA axis?
Amygdala activation stimulates HPA axis and stress response
Hippocampal activation suppresses HPA axis – less stress
how do the amygdala and hypothalamus cause changes in HPA axis?
by regulating corticotropin releasing hormone neurons in the brain
describe the cortisol feedback mechanism
Circulating cortisol binds to glucocorticoid receptors in hippocampus
Activation of hippocampus, which suppresses CRH release by hypothalamus
Reduces HPA activation – less cortisol release by adrenals
what’s the link between stress and memory?
Emotionally salient events are remembered better than neutral ones
Increased cortisol enhances memory, decreased cortisol reduces memory
what are the types of anxiety disorders?
generalised anxiety disorder panic disorder phobias obsessive compulsive disorders post traumatic stress disorders
what is generalised anxiety disorder?
Ongoing state of anxiety lacking any reason or focus at least 6 months duration - worry excessively about many issues
what is panic disorder?
Brief periods of intense terror and apprehension (panic attacks). Symptoms include shortness of breath, hyperventilation, heart palpitations, chest pain/tightness, trembling, tingling/numbness, dizziness. Often think they are having a heart attack.
what are phobias?
Strong fears of specific things or situations
what is obsessive compulsive disorder?
Intrusive thoughts (obsessions) cause anxiety (e.g., contamination with germs). Compulsions are repetitive behaviours that neutralise anxiety (e.g., frequent hand washing)
what is post traumatic stress disorder?
Anxiety triggered by recall of past stressful experiences
Occurs in some people following the experience or witnessing of life-threatening events
People relive the experience through nightmares and flashbacks, have difficulty sleeping and feel detached
Increased arousal and avoidance of stimuli associated with the trauma
what changes in the brain due to PTSD?
Hippocampus reduced in size and there is abnormal activation of the amygdala
what are the methods of treating anxiety?
psychological approaches first e.g. CBT and then pharmacological action
what are benzodiazepines?
anxiolytics which also have a sedative and muscle relaxant effect so are effective in short-term for acute anxiety
what are some side effects of benzodiazepines?
drowsiness confusion amnesia impaired cognition withdrawal symptoms reduced effectiveness and addictive with long-term use
what is the mechanism of action of brnzodiazepines?
They bind to a regulatory site on the GABAA-receptor to enhance the inhibitory effect of GABA
Increases the influx of Cl- into the neuron, causing hyperpolarisation and inhibiting action potentials
By inference, causes suppression of brain circuits in stress response
what drugs can be used for anxiety?
benzodiazepines
SSRIs
beta-adrenoreceptor antagonists
how do SSRIs work?
They work by prolonging the action of serotonin by blocking reuptake
how do beta adrenoreceptor antagonists work?
Reduce physical (sympathetic) symptoms of anxiety such as tremor, palpitations, sweating and also used to treat hypertension (high blood pressure)
what are some non-pharmacological stress reduction strategies?
social and recreational programmes relaxation training learning about how to manage stress meditation counselling
