Endocrine System

hormones

chem signals secreted by cells or glands which influence the actions of other cells within the body

what does the endocrine system regulate

• responses to the environment

• growth and development

• homeostasis

• reproduction

responses to the environment are

physiological changes

growth and development

embryo to adult

homeostasis involves

• negative feedback loops

• the hormones are the signals that effector cells receive

what triggers the release of hormones in environmental response

sensory input from the nervous system

what is the response for the environmental presence of a predator

release of adrenaline

what is the response for the environmental presence of a mate

release of sex hormones

examples of growth regulation triggered by hormones

• development of sex characteristics

• molting

• metamorphosis

what do the release of sex hormones trigger

the development of secondary sex characteristics and ossification of growth plates as an animal approaches adulthood

what triggers molting and metamorphosis in insects

release of hormones in tissues in the head

in growth regulation when are hormones released in metamorphosis

at each developmental stage

neurosecretory cells

cells that are neurons that secrete hormones, rather than neurotransmitters

what gland primarily controls growth regulation in humans

pituitary gland

what hormone does the pituitary gland secrete

the human growth hormone (hGH or somatotropin)

what does hGH/somatotropin do

tells body at which rate to mature

homeostasis regulation

• circadian rhythms

• metabolism

• fight, flight, freeze responses

• blood sugar

circadian rhythms

wakefulness/restfulness periods

metabolism

• hunger/fullness cues

• gut microbiome communicates with mind

fight, flight, freeze responses

stress

blood sugar

amount of glucose in body

what do negative feedback loops do

maintain homeostasis

is blood sugar regulation homeostasis

yes, it is regulated by a negative feedback loop

pancreas

• “sugar battery”

• endocrine and digestive organ that regulates blood sugar via negative feedback loops

negative feedback loop of pancreas/blood sugar regulation

• blood glucose levels rise (ex: by big meal)

• pancreas releases insulin because it detects a rise in sugar

• in response to insulin, target cells take up glucose and the liver converts glucose to glycogen

• blood glucose level falls (ex: heavy workout because consuming glucose in blood to fuel workout)

• pancreas releases glucagon to raise blood sugar

• in response to glucagon, the liver breaks down glycogen and releases glucose into the blood

purpose of positive feedback loops

• bring permanent change to body

• go from extreme A to extreme B and stay at extreme B

• have destabilizing impact

• used to precipitate a particular event

childbirth as positive feedback loop example

• baby’s growth takes up all space in uterus and puts on pressure

• pressure activates stretch receptors in uterus

• brain signals for release of oxytocin (time to give birth)

• oxytocin is increasingly released to further induce contractions by uterine muscles

• move baby and contractions get stronger until baby is delivered