ZOOL313 Stress, Reproduction, and Melatonin Modules

homeostasis

maintenance of constant or relatively constant internal conditions irrespective of fluctuating external conditions

Claude Bernard

Father of modern experimental medicine. Lived in the 1800’s, research and teaching, and the pancreas and digestion

Walter B. Cannon

Key concept he found out about was homeostasis and did some research dealing with the physiology of emotions. Adrenal medulla, fight or flight

allostasis

a “variable” state; change of state; involves changing the set points e.g. red blood cell increasing in response to higher altitudes in athletes or hormone levels increasing in preparation for sheep breeding season

acclimitization

adjustment of set points to a new equilibrium in a natural setting

habituation

adaptation in a physiological context

acclimation

adjustment of set points to a new equilibrium in a laboratory setting

endocrine signaling

the signal is released into the bloodstream for those chemicals who can tune in and are happy to do so

synapse signaling

chemical message released across a synapse (open area from a nerve cell to another cell) with receptors picking up specific signals. Can be compared to using cups on strings for communication

Cell Communication Signal Receiving Steps

secretion, reception, signal transduction through some cellular pathway

paracrine signaling

a local form of cell signaling via the extracellular matrix

autocrine signaling

a cell signals itself

cytokines

immune system signaling molecules used to fight infection and inflammation

ligand

first messengers in signal transduction that act through receptors, often by binding to them. They are often neurotransmitters, hormones, or cytokines. Often bind to more than one receptor subtype

membrane receptor

located on the plasma membrane and the ligands that bind to such things can’t cross the plasma membrane. Many of these sort of things work like this

intracellular receptor

ligands for these things can cross the plasma membrane and find it in the cell

Hans Selye

“father of stress physiology,” got ideas from visiting hospital wards as a medical student, and identified the importance of the adrenal cortex

stressor

the disturbance that gives rise to a stress response, e.g. earthquake

stress response

stimulates a physiological response in response to a psychological factor

stress

state of prolonged exposure to a stressor. Depending on its severity, it may result in sickness or death, e.g. Covid-19, exposure to prolonged heat/cold

peripheral nervous system

describes the nervous system outside of the brain and spinal cord

autonomic nervous system

have no control over this broad part of the peripheral nervous system

sympathetic division

fight and flight

parasympathetic division

rest and digest

adrenal glands

on top of the kidneys and are made up of the adrenal cortex and adrenal medulla

adrenal medulla

catecholamine release, adrenaline and noradrenaline

adrenal cortex

corticosteroid production and release; cortisol/corticosterone

adrenaline

signal that drives the fight or flight response. The tyrosine amino acid is used as a starting point to produce with dopamine as an intermediate. Needs to kick in instantly for survival

adrenergic receptor

a G-protein coupled receptor that binds adrenaline in the center of the binding pocket. Crosses the plasma membrane 7 times and is arranged in a circle from the top

osmorespiratory compromise

when there is a stressor, the gills in fish become more permeable so that more oxygen can come in. Comes at the expense of upsetting the water/mineral balance, which drives fight or flight

triad of stress

adrenal enlargement, gastrointestinal ulcers, thymolymphatic atropy (supression of the immune system)

lymphatic system

a network of organs, vessels, and tissues that protects an animal from infection and maintains fluid balance

inflammatory response

a defense mechanism that evolved in higher organisms to protect them from infection and injury. When an animal gets wounded and perforated, pathogens come in and chemical signals come. Phagoctyes, fluid, and blood clotting elements then come in. The dilation and increased permeability of blood vessels occurs. Phagocytosis of pathogens occurs

pro-inflammatory cytokines

activate the immune system’s army of white blood cells; e.g. IL-1, IL-6, IL-8, tumor necrosis factor-alpha (TNF α) (macrophage activator)

exaggerated immune responses

allergies, anaphylatic shock, cardiovascular inflammation and injury, lethargy, severe SIRS (sepsis)

self-directed immune responses

autoimmune disease (thyroid, diabetes, rheumatoid arthritis, MS, mood disorders)

SIRS

systemic inflammatory response syndrome; hyper-inflammation associated with infectious agent

glucocorticoids

vertebrate stress hormones produced by the adrenal cortex. Play a role in curtailing the immune response and restoring things to their “normal” state

cortisol

glucocorticoid in almost all fish and most mammals

corticosterone

glucocorticoid in amphibians, reptiles, birds, and rodents

interrenal tissue

responsible for the synthesis of corticosteroids in fish

HPA Axis

complex set of interactions between the hypothalamus, pituitary gland, and adrenal glands; plays a critical role in regulating stress responses, mood, digestion, immune function, and energy storage and expenditure in the body. The pathway of the axis results in the production of corticosteroids

hydrocortisone

anti-inflammatory cream

amygdala

memory and emotions (fear!)

hippocampus

long-term memory and spatial navigation

declarative memory

the conscious or voluntary recollection of previously learned information

Propranolol

beta blocker drug; blocks the release of adrenaline

Metyrapone

inhibitor of 11-beta-hydroxilase, one of the enzymes that catalyzes cortisol synthesis

migration

large-scale movement of members of a species to a different environment, which often occurs seasonality and can help time when animals have their offspring. In some species, certain physiological aspects can change in preparation for it e.g. salmon’s ability to survive seawater increases because enzyme activity for pumps that help regulate water-mineral balances increases fourfold in the span of 2-3 months

ultimate cause

explains why or how it got to be that way, often related to evolution or adaptation

proximate cause

explains how it works mechanism-wise and ontogenetic (developmental factors)

atrophy

degenerate, regress

recrudesce

to grow

pineal gland

secretes melatonin, the messenger (hormone) of darkness; gathers information on the change in photoperiod to function

pinealectomy

removal of the pineal gland; prevents testicular atrophy in hamsters

suprachiasmatic nucleus (SCN)

neural pathway from the retina to the pineal passes through this in mammals; is a tiny region within the hypothalamus and generates a rhythm that affects melatonin secretion from the pineal; master clock and has an endogenous rhythm that doesn’t run exactly on a 24 h day-night cycle (light entrains this rhythm)

pinealocytes

cells of the pineal gland that secrete melatonin during darkness; not directly light sensitive, so they are affected by neural input from the SCN and lateral eyes

pineal complex

contains two components: pineal organ or gland and a parapineal organ. Present in fish (3 classes), amphibians, and reptiles

parietal eye

located at the top of the head and is essentially the parapineal gland; appearance and function of a lateral eye; passes day/night signals to the pineal gland as well

HPG Axis

controls reproduction, aging, and development. Gonadotropin-releasing hormone (GnRH) is secreted by the hypothalamus by GnRH-expressing neurons. The anterior portion of the pituitary gland produces luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and the gonads produce estrogen and testosterone. This has a slightly different name and works slightly differently in female oviparous organisms