Homones and Stress

Question 1

The Neuroendocrine System

Answer 1

> . The system links processes in the central nervous system (i.e., the brain) to the endocrine system, which releases hormones.
. The most thoroughly studied neuroendocrine complex, the Hypothalamic-Pituitary-Adrenal (HPA) axis, has been implicated as the chief mechanism in the human stress response.
•Thus the multitude of processes involved with the stress response are collectively called allostasis.

Question 2

Hormone production

Answer 2

Our somatic processes are largely controlled by hormones.
Hormones are chemical messengers released by a cell in one part of the body that affect cells in other parts of the body.
Hormones commonly travel via the circulation system.
Hormones bind to specific receptor proteins expressed on the surface of the target cell, resulting in a cell type-specific response.

Question 3

Effects on the Body

Answer 3

• stimulation or inhibition of growth
• mood swings
• induction or suppression of apoptosis
• activation or inhibition of the immune system
• regulation of metabolism
• preparation of the body for mating, fighting, fleeing, and other activity
• preparation of the body for a new phase of life, such as puberty, parenting, and menopause
• control of the reproductive cycle
• hunger cravings

Question 4

Glands

Answer 4

Generally, hormones are released from specialized cell types residing within a particular endocrine gland
Endocrine Gland: an organ whose primary function it is to release hormones
But other organs also release hormones (e.g., stomach, liver, fat tissue)

Question 5

Types of Hormones = Vertebrate

Answer 5

1. Amine acid derivatives, derived from the amino acids tyrosine and tryptophan. e.g., thyroxine.
2. Peptide hormones, chains of amino acids.
   Small chains: vasopressin (water retention)
   Long chains: (Protein hormones) Insulin
3. Steroid Hormones, synthesised from cholesterol
   e.g., testosterone and cortisol

Question 6

The Pituitary Gland

Answer 6

• The anterior pituitary gland, regulates several physiological processes including stress, growth, and reproduction
• Regulated by the hypothalamus, targets adrenal gland, liver, bone, thyroid gland, and gonads
• The posterior pituitary gland, a collection of axonal projections from the hypothalamus terminating behind the anterior pituitary gland.
• Both the paraventricular nuclei and the supraoptic Nuclei from the hypothalamus release:

Oxytocin: Uterine contractions; lactation
Vasopressin: Water retention, raises

Question 7

Regulation of Hormone Levels

Answer 7

1) Neural: All endocrine glands (except the anterior pituitary) receive neural signals from cerebral neurons or neurons from the ANS (Sympathetic vs. Parasympathetic)
2) Hormonal: e.g., tropic hormones. Maintains stable blood concentrations via negative feedback
3) Non-hormonal Chemicals, e.g., glucose and insulin.

• Hypothalamic Releasing Hormones: Releasing and inhibiting hormones control production and release.

Question 8

Stress

Answer 8

> . The body responds to environmental and life events
. If exposed to harm or threat the body enacts a stress response
. Stress is characterised by physiological changes that prepare the organism to survive a stressor
. Stressors (objects or events that trigger stress)
. Chronic psychological stress negatively impacts health

Question 9

The Autonomic Nervous System

Answer 9

A control system in which the brain manages numerous biological processes based upon the demands of the environment. The autonomic nervous system controls, amongst other processes, heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, urination, and sexual arousal.

Question 10

The Neuroendocrine System

Answer 10

The system linking processes in the central nervous system (i.e., the brain) to the endocrine system, which releases hormones. The most thoroughly studied neuroendocrine complex, the Hypothalamic-Pituitary-Adrenal (HPA) axis, has been implicated as the chief mechanism in the human stress response.

Question 11

The Immune System

Answer 11

A collection of bodily structures and processes concerned with the identification, elimination, and disposal of foreign objects (i.e., antigens). Immune systems protect the body from infection, and when compromised, leave an individual vulnerable to disease.

Question 12

The STRESS Response

Answer 12

Hans Selye: Short-term Stress J vs. Long-term Stress L
Stressors induce adrenocorticotropic hormone (ACTH) release from the anterior pituitary.
The ACTH triggers the release of glucocorticoids (e.g., Cortisol) from the adrenal cortex
Glucocorticoids, damaging if levels are chronically raised
Selye: Both physical or psychological stressor can produce a general stress response

Question 13

Glucocorticoids

Answer 13

Steroid hormones that bind to the glucocorticoid receptor (GR), which is present in almost every vertebrate animal cell.
GCs are part of the feedback mechanism in the immune system that turns immune activity (inflammation) down

Question 14

Adrenaline

Answer 14

Increases heart rate, contracts blood vessels and dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system

Question 15

Noradrenaline

Answer 15

A stress hormone, affecting parts of the brain where attention and responding actions are controlled. Also underlies the fight-or-flight response along with adrenaline.

Question 16

The Hypothalamic Pituitary Adrenal Axis

Answer 16

• Integrates perceptual, emotional, and cognitive inputs, and underlies our response to threats.

• Axis and end products, glucocorticoids (cortisol):
– control energy supply through gluconeogenesis
– suppress responses to inflammation and infection
– regulate development and aging
– are critical for successful behavioural adaptation to stress
– cortisol restrains defense reactions, which otherwise can
become damaging
– but in excess, this restraint of defense can increase
vulnerability to disease

Question 17

The Hypothalamus is a regulator

Answer 17

• Autonomic functions (GIT, circulation)
• Metabolism
• Biological rhythms
• Body temperature
• Feeding-drinking
• Instinct behaviours and emotions
• Endocrine system

Question 18

Hypothalamic nuclei

Answer 18

• The nuclei that connect with the posterior pituitary are located in the supraoptic region:
Supraoptic nucleus (SON)
Paraventricular nucleus (PVN)

Question 19

Stress and Gastric Ulcers

Answer 19

Gastric ulcers – lesions of stomach lining and duodenum
More common in those who are stressed; readily created in the animal lab
Ulcers are caused by a bacteria – stress appears to make the body vulnerable to this bacteria
75% of healthy subjects have the bacteria

But even brief exposures to stressors can raise levels of stress hormones
For example, brief stressors increase the blood level of cytokines
Cytokines are vital components in the bodies immune response, causing fever and tissue inflammation

Question 20

Psychoneuroimmunology

Answer 20

> . Study of the interaction of psychological factors, nervous system, and immune system
. Stress can increase or susceptibility to infectious diseases
. Antigens – surface proteins that identify a cell as native or foreign
. Cell-mediated vs. Anti-body mediated immunity

Question 21

Immune System

Answer 21

Divisions of the mammalian immune system
Innate immune system
First line of defense
>. Attacks generic classes of pathogens
>. Adaptive immune system
>. Targets specific pathogens identified by their antigens
>. Has memory (the basis of effectiveness of vaccination)
>. Cytokines activate lymphocytes (white blood cells)
>. Cell-mediated (T lymphocytes)
>. Antibody-mediated (B lymphocytes)

Question 22

The Immune System and Stress

Answer 22

> . Effects of stress on immune function depend on the kind of stress
. Acute stressors (eustress) improve immunity
. Chronic stressors (distress) impair immunity
. Many ways that stress can impact immune function
. Effects of stress can be good (adaptive and healthful), bad, or mixed