Stress Psychophysiology Chapter 2

Chapter Overview Components of the brain and body involved with stress Stress pathways (endocrine, autonomic) Other components involved: cardiovascular system gastrointestinal system muscles, skin

The Brain Two major components Cerebral cortex (thinking functions) Subcortex (physiological processes)

Subcortex Includes the Limbic System (“seat of emotions”) Thalamus Hypothalamus See Figure 2.1 Diencephalon

The Brain Hippocampus (sounds the stress alarm) Cerebellum (coordinates body movement) Pons (regulates sleep) Medulla oblongata (heart beat, respiration)

Did You Know? Adrenal glands release glucocorticoids during stress Glucocorticoids are detected by hippocampal cells With prolonged stress, these cells are damaged and possibly lost forever

Stress and Its Pathways The hypothalamus activates the following under a stress response: Autonomic nervous system Immediate fight-or-flight response Endocrine system Short-term and long-term stress response

Stress and It’s Pathways

Autonomic Nervous System Two systems working together during immediate stress: Sympathetic (responsible for expending energy) Parasympathetic (responsible for conserving energy) Figure 2.6 shows innervation of both divisions of the ANS

Endocrine System Includes glands that secrete hormones Hormones travel through the blood stream These hormones change function of bodily tissues See Figure 2.3

Major endocrine glands

Endocrine System (cont.) Four pathways Adrenal Medulla Adrenal Cortex Thyroid Vasopressin (ADH) and Oxytocin

Adrenal Medulla Secretes two catecholamines: epinephrine (adrenalin) and norepinephrine (noradrenalin) Effects remain 10 times longer than adrenal corticoids and include: Increased heart rate Increased stroke force Dilation of coronary arteries Dilation of bronchial tubes Increased basal metabolic rate Constriction of vessels to skin of arms, legs, muscles Increased O2 consumption

Adrenal Cortex Influenced by the hypothalamus and pituitary gland Adrenal cortex secretes glucocorticoids and mineralocorticoids Primary glucocorticoid is cortisol Primary mineralocorticoid is aldosterone Cortisol provides fuel for “fight-or-flight” action Aldosterone increases blood pressure to prepare for action

Thyroid Influenced by the hypothalamus and pituitary gland Thyroid gland secretes thyroxin Increases the following: basal metabolic rate free fatty acids gluconeogenesis gastrointestinal motility respiration heart rate blood pressure anxiety

Vasopressin (ADH) and Oxytocin ADH and oxytocin are produced by the pituitary gland ADH acts on the kidneys to decrease urine production via water retention Oxytocin increases contraction of the walls of blood vessels Together, these two changes will increase blood pressure

The Autonomic Nervous System

The Cardiovascular System Transports blood to cells and organs Stress on the circulatory system may cause release of oxytocin and vasopressin Both can constrict blood vessels, leading to increased blood pressure Heart responds with increased force of contraction Cholesterol and free fatty acids increase risk of heart disease

The Gastrointestinal System Responsible for digestion Stress reduces saliva production and increases hydrochloric acid production Ulcers can develop Stress can alter rhythmic movement of food, leading to bowel distress and diseases

The Muscles Stress results in tensing, known as “bracing” Leads to the development of muscle pain and aches

The Skin Involved with stress response Temperature and electrical conduction affected Stress causes increased perspiration Vasoconstriction occurs during stress, causing skin color to change

Stress Psychophysiology