Stress Response

Aims

To measure a range of physiological and psychological responses to both physiological and psychological ‘stress’ conditions in order to better understand the physiological significance and underlying mechanisms of ‘stress’.

Introduction

Stress define as biological and psychological sciences and also refers to either physiological or psychological state. One of the example for physiological stress is temperature extreme where the body will undergo heat stress and a number of stress responses to the extreme heat in our body including perspiration and thirst. An example for psychological stress happens when sitting for final exam where the stress response can occur any time before, during or after the exam and this would increase heart rate and blood pressure and feeling of anxiety.

Stressor activates the hypothalamic pituitary adrenal (HPA) axis when stress is applied. HPA act as an important component for the stress response. During the activation of HPA, hypothalamus release corticotrophin releasing (CRF) hormone and will binds to CRF receptors on the anterior pituitary gland. The binding process on the anterior pituitary gland will then stimulates the secretion of adrenocorticotropic hormone (ACTH). ACTH will binds to the receptors on the adrenal cortex stimulating adrenal to release cortisol hormone. Coritsol is a type of glucocorticoid hormone where its primary hormones are responsible for stress response. The main function of cortisol is to restore homeostasis after exposure to stress. When the glucose level decreass, cortisol will counters it by increasing level of glucose through the stimulation of gluconeogenesis which synthesizes glucose from oxaloacetate. Glucose synthesis is stimulated in the liver. Cortisol will also inhibits the production of insulin in order to prevent glucose storage and favoring its immediate use. There are two glucocorticoids hormones released by the adrenal cortex are hydrocortisone and corticosterone where hydrocortisone will regulate the conversion of fats, carbohydrates and protein into energy and help to regulate our blood pressure and cardiovascular function. Corticosterone also function as regulating immune response and suppress inflammatory reactions. Mineralcorticoid consider as the main group of corticosteroid hormones are mediated by signals triggered by the kidney in which to maintain the balance of salt and water in order to control blood pressure (Greenberg, Carr & Summers 2002).

Stressor causes hypothalamus to activate adrenal medulla where it is part of the autonomic nervous system, autonomic nervous system and peripheral nervous system that will acts as a control system to maintain homeostasis in our body. The activities performed by these nervous system are controlled without conscious state. Adrenal medulla will secretes adrenaline hormone to prepare our body ready for any fight or flight response. Adrenaline will responds to stress by increasing our heart rate and blood flow to our brain and muscles. It also helps in increasing the blood sugar level by stimulating the conversion of glycogen to glucose in the liver. Adrenal medulla secretes norepinephrine hormone and it works along with epinephrine to respond to stress but norepinephrine can causes vasoconstriction that narrow blood vessels and decrease blood supply which lead to an increase in blood pressure (Tsigos & Chrousos 2002).

Material and Methods

Stress response 1

Materials

20 10ml sterile tubes, 20 Eppendorf tubes, treatment groups (control, pain stress, exercise stress and mental stress) , labeled cuvettes and LabChart software program on the computer (connected to Powerlab physiological recording equipment)

Method

1. 4 students were each given a condition (1 student act as a control, 1 student physical stress involving cold/ pain stress- holding hand in a bucket of ice water for 5 minutes, 1 student physical stress involving exercise stress- performing vigorous ‘star jumps’ or ‘steps’ for 5 minutes, 1 student psychological stressor involving mental arithmetic and singing- singing to one group members for 5 minutes)

2. Equipment was hooked on each person for the measurements of the baseline measurements for 5 minutes which was connected to LabChart. For the BP and HR, 2 measurements were taken for the average. For the CORT, saliva was collected sometime during the 5 minutes period.

3. Each stressor condition and control condition was initiated on each student for 5 minutes. Tc, GSR and HR were recorded throughout. For BP, the measurement was taken at the end of the ‘stressor’. For CORT, saliva was collected at the end of the ‘stressor’.

4. Until 20minutes point, continue recording Tc, GSR and HR throughout and at 20 minutes point BP was measured and saliva was collected. At this point TC, GSR, HR and BP had returned to baseline, it was not necessary to take further readings for these measurements.

5. At 60 and 120 minutes time points, saliva was collected at both of these points. The control student’s saliva was collected at the same time as the student doing the 1st stressor which was cold stress. The other measurements Tc, GSR, HR and BP were made in the original order.

Stress response 2

Materials

Microtitre plate (coated with monoclonal anti-cortisol antibodies), Wash Buffer Concentrate (10x), Assay diluents, cortisol standard, controls, cortisol enzyme conjugate, TMB substrate solution, non-specific binding wells, 5-50uL micropipette, 30-300uL multichannel micropipette, reagent reservoir pack, 3M Stop solution, falcon tube, pipette tips: yellow and white, 10mL micropipette, 450ml deionized water in 500mL Schott’s bottle, waste plastic beaker, 50mL measuring cylinder

Method

1. 1x wash buffer (500ml) was prepared by diluting wash buffer concentrate 10 fold with room temperature deionized water (50ml of 10x wash buffer to 450ml deionized water).

2. The plate layout was determined

3. 24mL of assay diluents was pipetted into a disposable tube

4. Following samples were pipette:

-standards: 12 wells

-assay diluents: 2wells (zero)

-assay diluents into NSB: 2 wells

-control high: 2 wells

-control low: 2wells

-samples: 3 wells per