Chapter 7: Stress and Adaptation Flashcards
Learning Objectives
- Describe the concepts of homeostasis, components of the control system and the negative feedback system.
- Explain the interactions of the autonomic nervous system in mediating the stress response.
- Describe the stress responses related to the endocrine system, the immune system, and the musculoskeletal system.
- Discuss chronic stress r/t general adaptation syndrome (GAS).
- Describe the characteristic of posttraumatic stress disorder and treatment.
What is homeostasis
the maintenance of internal balance/stability
What is negative feedback
An attempt of a system to return to homeostasis that responds to a disturbance in the OPPOSITE direction of the original disturbance (as opposed to positive feedback that responds in the same direction).
ex: thermostat (if it’s set at 70 and a cold wind Decreases the temperature to 67, the thermostat will elicit a negative feedback response and Increase the temperature back to 70)
Another example: blood sugar
(resting blood sugar is 90mg/100mL.)
Eating raises blood sugar. beta cells in the pancreas release insulin which helps glucose either get taken up by the cells or stored in the liver as glycogen. Blood sugar returns to its set point.
Fasting lowers blood sugar. Alpha cells in the pancreas release glucagon which signals the liver to break down glycogen and release glucose into the blood stream. Blood sugar increases back to its set point.
what is positive feedback?
a self-reinforcing response to a stimulus (responds in the same direction as the stimulus) that helps maintain body stability
ex: Childbirth – stretching of uterine walls cause contractions that further stretch the walls (this continues until birthing occurs)
Lactation – the child feeding stimulates milk production which causes further feeding (continues until baby stops feeding)
what is stress and what are the types of stress
the response to any bodily stimuli
symptoms related to activation of the neuroendocrine and immune systems
Distress (ie: disease or injury) v. Eustress (ie: childbirth or test taking)
what is adaptation
the response to stressors (physical or psychological) and the ability to return to homeostatic balance
What is General Adaptation Syndrome (GAS)?
the stages of stress developed by Selve
“Stressors ARE bad”
A: alarm
R: resistance
E: exhaustion
Identify the changes that occur in all three stages of
Selve’s GAS
Alarm: the physiological response to stress that triggers the sympathetic nervous system (SNS; fight or flight) and the hypothalamic-pituitary-adrenal axis (HPA axis). This leads to hormone release that helps prep the body for the rest of the stress response. Specifically catecholamines (epi & norepi) and cortisol. Meanwhile, the body decreases unessential energy expenditure (ie: digestion)
Resistance: the body responds with its defense and cortissol levels drop. Prolonged stress leads to stage 2-resistance and can occur in chronic diseases or ongoing stressors (homelessness, abuse…)
Exhaustion: When the body’s resources are depleted. Too much wear and tear can lead to systemic damage and the body is more susceptible to illness
Stress hormones overview & effects of catecholamines
*Note: these hormones come from HPA origins *
Catecholamines (NE, epi):
come from the LC ((locus coeruleus: brain region in the pons associated w stress) & adrenal medulla
*Decrease insulin resistance
*Increase glucagon (increases glycogen formation, decreases glucose uptake by the tissues), heart rate, vascular smooth muscle contraction, relaxation of bronchial smooth muscle
Adrenocorticotropic hormone (ACTH)
comes from the anterior pituitary gland
stimulates synthesis and release of cortisol
Corticotropin-releasing factor (CRF):
comes from the hypothalamus
stimulates ACTH release from the anterior pituitary. increases LC (locus coeruleus) neuronal activity
glucocorticoid hormones
ex: cortisol
come from the adrenal cortex
increases the effects of epi and glucagon
inhibits the release/actions of reproductive hormones and TSH (thyroid stimulating hormone)
decreases immune cells and inflammatory mediators
mineralocorticoid hormones
ex: aldosterone
come from the adrenal cortex
increase sodium absorption by the kidney
antidiuretic hormone (ADH/vasopressin)
comes from the hypothalamus
and posterior pituitary
increases water absorption by the kidney (does not want to release water)
produces vasoconstriction of blood vessels
stimulates release of ACTH
HPA Axis
(basic definition and mechanism of stress response)
hypothalamic-pituitary-adrenal axis: the neuroendocrine-–immune system Regulation of the stress response.
stress–>
release of corticotropin-releasing factor (CRF) by the hypothalamus
CRF can travel to the pituitary gland that in turn signals the release of ACTH (adrenocorticotropic hormone)
this signals the activation of the adrenal gland (of the kidney) to synthesize and secrete glucocorticoid hormones (ex: cortisol)
CRF also activates the LC (locus coruleus) which stimulates the autonomic nervous system –> catecholamine release –> sympathetic nervous response (fight or flight)
Summary of Neurological Responses to Stress Diagram
- How is the HPA axis activated?
- What happens in response to the release of cortisol from the HPA axis?
- What happens in the Autonomic Nervous System (ANS) upon a stress response (stimulated by CRF production)?
- What happens in the Reticular Activating System (RAS) with stress?
- through the activation of the limbic system (part of the brain involved when it comes to behaviours we need for survival: feeding, reproduction and caring for our young, and fight or flight responses. Consists of the amygdala, hippocampus, thalamus, hypothalamus, basal ganglia, and cingulate gyrus.)
- cortisol triggers the increase of fat, increased mobilization of glucose, and increased protein metabolism and the suppression of inflammation and immune responses
- When the ANS is activated, the adrenal medulla releases catecholamines that lead to cardiac symptoms of fight or flight
- we become more alert and muscle tension is increased
