Bio 133 Homeostasis and Endocrine Signaling Terms

homeostasis

“steady state” or internal balance regardless of external environment

process of Homeostasis

set point → stimulus → response

hypothalamus

region of the brain that controls thermoregulation in mammals, triggering heat loss or heat generating mechanisms

stimulus

change from set point in the body

what happens when the body is too hot?

blood vessels in skin dilate

what happens when the body is too cold?

blood vessels in the skin constrict

endocrine system

organs and tissues that produce hormones

hormones

regulatory chemicals secreted into extracellular fluid and carried by the blood

what are the 3 classes of hormones?

peptide and proteins, amino acid derivatives, and steroids

what is a lipophilic hormone?

lipid soluble, steroid/thyroid hormones, travel on transport proteins in blood, bind to intracellular receptors, tend to act over brief time period

what is a hydrophilic hormone?

water soluble, all other types of hormones, freely soluble in blood, bind to extracellular receptors, tend to have much longer active period

what is the pituitary gland

hangs by a stalk from the hypothalamus and consists of two parts

anterior pituitary

epithelial tissue in origin (true endocrine)

posterior pituitary

nervous tissue in origin

how does the anterior pituitary work?

controlled by hormones from the hypothalamus when it secrets releasing hormones and inhibiting hormones, negative feedback/feedback inhibition

how does the posterior pituitary work?

stores and releases two hormones like ADH and Oxytocin

what is Antidiuretic hormone (ADH)?

Peptide hormone that stimulates water reabsorption by the kidney, and thus inhibits diuresis (urine production)

Oxytocin

Peptide hormone in mammals, it stimulates the milk ejection reflex and uterine contractions during labor, and it regulates reproductive behavior

pancreas

raises pH in the duodenum

exocrine gland

secreting substances through a duct

endocrine gland

secreting hormones directly into interstitial fluid

what are the functions of the excretory systems?

regulation of extracellular fluid volume and blood pressure, regulation of osmolarity, maintenance of ion balance, homeostatic regulation of pH, excretion of wastes, and production of hormones

osmoconformers

organisms that are in osmotic equilibrium with their environment
among vertebrates, only the primitive hagfish are strict osmoconformers
sharks and relatives (cartilaginous fish) are also isotonic

osmoregulators

all other vertebrates, maintain a relatively constant blood osmolarity despite different concentrations in their environment

what is the vertebrate kidney made of?

thousands of repeating units - nephrons

all vertebrates can produce a urine that is isotonic or hypotonic to blood

only birds and mammals can make a hypertonic urine (more concentrated than blood)

What are the three basic functions of the kidney

filtration, reabsorption, and secretion

what does ADH do to the walls of the distal tubule and collecting ducts?

makes it more permeable to water by releasing aquaporins, it increases the reabsorption of water, leading to a more concentrated urine

what does aldosterone do?

causes distal convoluted tubule and collecting ducts to reabsorb Na+, low levels of Na+ in the blood are accompanied by a decrease in blood volume

atrial natriuretic hormone (ANH)

opposes the action of aldosterone in promoting salt and water retention, secreted by the right atrium of the heart in response to an increased blood volume, promotes the excretion of salt and water in the urine and lowering blood volume