Lab 5: Stress Physiology

What is the purpose of this lab?

to explore the effect of a physical stressor, the cold pressor test, on perceived stress level, heart rate, and systolic pressure.

What is eustress?

prepares us to meet certain challenges and is thus beneficial. Distress is harmful.

What is a stressor?

any stimulus that produces a stress response in the body. A stressor may be almost any disturbance to the body- heat or cold, environmental poisons, toxins given off by bacteria, heavy bleeding from a wound or surgery, a strong emotional reaction, or hypoglycemia.

What did Hand Seyle (1907-1982) do?

a pioneer in stress research, showed that a variety of stressful conditions (e.g., prolonged food deprivation, shock, excessive exercise, etc.) elicit a similar sequence of changes in the body.

What are the three stages of the stress response or general adaptation syndrome (GAS)?

1. an initial fight-or-flight response (also known as the alarm phase) 2. a slower resistance reaction 3. exhaustion

What is the fight-or-flight (alarm) phase?

occurs shortly after a stressful event, gives people a burst of energy; blood glucose levels go up and heart rate increases to deliver more nutrients to the body's tissues.

What is the resistance phase?

right after fight-or-flight phase, during which the body tries to counteract the physiological changes that happened during the alarm phase. If the stressor has stopped, the body is able to return to normal homeostasis.

What is the exhaustion phase?

if the stress continues, body enters the exhaustion phase. The body has depleted its energy resources by continually trying to respond to the stressor. If the exhaustion phase is prolonged, long-term damage to the body may occur.

How is the stress response produced?

most physical and psychological stressors are integrated through the CNS.

What controls activation of the stress response?

the hypothalamus, which receives a variety of stress signals, including signals form the amygdala.

What does the amygdala do?

area of the brain that contributes to emotional processing.

What are the two stress pathways that the hypothalamus activates?

a fast, neurally-mediated pathway (autonomic response), and a slower, but longer-lasting endocrine response.

What initiates the fight-or-flight response?

action potentials from the hypothalamus to the sympathetic division of the autonomic nervous system, including the adrenal medulla (sympathoadrenal system). The hypothalamus activates preganglionic neurons in the CNS.

What do the preganglionic neurons do?

they project to autonomic ganglion outside the central nervous system. There, the preganglionic neurons synapse with postganglionic neurons.

What do the postganglionic neurons do?

have their cell bodies in the ganglion and project their axons to the effector tissues.

What does the fight-or-flight response do to the body?

it brings large amounts of glucose and oxygen to the organs that are most active in warding off danger: the brain, the skeletal muscles, and the heart.

How does the brain ward off danger?

becomes highly alert

How do the skeletal muscles ward off danger?

right off an attacker or flee

How does the heart ward off danger?

must work vigorously to pump enough blood to the brain and muscles.

How does the sympathetic nervous system elicit the fight or flight response?

uses a variety of chemical signals and membrane receptor proteins.

Where do preganglionic neurons originate?

the hypothalamus release the neurotransmitter acetylcholine onto nicotinic cholinergic receptors on the postganglionic cell.

What does the postganglionic neuron release?

norepinephrine

What do the chromaffin cells of the adrenal medulla release?

epinephrine which can bind to a (alpha) or B (beta) adrenergic receptors on the target tissue

What do the B1-adrenergic on cardiac tissues do?

increase heart rate and force of contraction

What do the a-adrenergic receptors do?

dilate the pupils of the eyes.

What do the a-receptors do?

results in vasoconstriction, which decreases blood flow to nonessential organs, such as the gastrointestinal tract. Dividing blood to the skeletal muscles, liver, and heart.

What do the b2-receptors do?

results in vasodilation, which enhances blood flow, and found in smooth muscle of blood vessels to the heart, skeletal muscles, and liver

What do B2-adrenergic receptors do?

mediate lipolysis (breakdown of fat) in adipose tissue, glycogenolysis (breakdown of glycogen) in liver, and catabolism of skeletal muscle proteins into amino acids.

What are lipolysis, glycogenolysis, and catabolism important for?

to provide substrates for making ATP and energy to fight or flee the stressor.

What to catecholamines do?

binding of catecholamines to a- and b adrenergic receptors results in glucagon secretion and inhibition of insulin secretion. The net effect is an increase in blood glucose concentrations.

What mediates the resistance reaction?

the endocrine system as well as initiated by the hypothalamus. Helps the body continue fighting a stressor after the fight-or-flight response dissipates.

What happens if the resistance phase fails to combat the stressor?

the body moves into the state of exhaustion

How does the body sustain energy throughout the resistance phase?

activation of the hypothalamis-pituitary-adrenal (HPA) axis.

How does the HPA response begin?

when the hypothalamus, activated by stress, secretes corticotrophin-releasing hormone (CRH).

What does the corticotrophin-releasing hormone do?

directs the anterior pituitary to release adrenocorticotropic hormone (ACTH).

What does ACTH do?

directs the adrenal cortex to secrete the steroid hormone cortisol.

What does cortisol do?

diffuses into the blood and travels (attached to a carrier protein) to target tissues, such as the liver, skeletal muscle, or adipose tissue, to help mobilize energy stores by promoting gluconeogenesis by liver cells, lipolysis in adipose tissue, and protein catabolism in skeletal muscle.

What does prolonged exposure to high levels of cortisol cause?

wasting of muscle, suppression of the immune system, ulceration of the GI tract, and failure of pancreatic beta cells. As well as pathological changes.

What does prolonged stress cause?

suppression of the immune system, increased risk of developing type 2 diabetes, cardiovascular disease, depression, and memory problems.

What are you measuring in the lab?

cold pressor test, on perceived stress level, heart rate, and systolic pressure.

What is a sphygmomanometer used for?

standard way to measure blood pressure (an inflatable cuff with pressure gauge) and a stethoscope to listen to blood flow. Inflated to 180 mmHg.