Unit 6: Hormones, Homeostasis, and Excretion Flashcards
Homeostasis (2)
- the process by which organisms maintain a stable internal environment
- the internal environment is narrow as it fluctuates very little
What are some examples of homeostatic components? (2)
- body temperature
- blood glucose levels
What two systems are important in maintaining homeostasis? (2)
- nervous system
- endocrine system
How is the nervous system involved in regulating homeostasis?
it send electrical impulses from the central nervous system to neurons to tissues
How is the endocrine system involved in regulating homeostasis?
send chemical hormones from glands through lymph and blood to tissues
Homeostatic Mechanisms
mechanism that maintains a set point
What is an example of a homeostatic mechanism?
negative feedback
Negative Feedback
one thing is produced which inhibits/lowers something else
What is an example of negative feedback?
body temperature
Positive Feedback (2)
- the body continues the stimulus
- not a homeostatic mechanism
What is an example of positive feedback?
contractions, oxytocin produces uterine contractions right before birth, more oxytocin, more contractions
How is body temperature maintained? (2)
- by a negative feedback system
- the hypothalamus
How does the hypothalamus regulate body temperature?
if body temperature is too high, it send impulses through neurons throughout the body
What are ways to bring body temperature down if it is too high? (3)
- sweat glands produce sweat for evaporative cooling
- metabolic rate can be lowered so that excess heat is not produced
- vasodilation
What are ways to bring body temperature up if it is too low? (4)
- vasoconstriction
- shivering
- hugging someone
- countercurrent heat exchange
Countercurrent Heat Exchange (3)
- bodily process that animals only have
- arteries carrying warm blood are in blood contact with veins conveying cool blood back toward the core
- allows heat to transfer from the arteries to veins
What are the 2 hormones produced to regulate blood glucose? (2)
- insulin
- glucagon
What organ produces insulin and glucagon?
the pancreas
Insulin
a hormone that is responsible for glucose uptake from the blood to lower glucose concentrations
What happens as a result of the release of insulin? (3)
- glucose is taken up by cells for respiration
- glucose is stored in the liver and muscles as glycogen
- glucose is stored as adipose tissue
Glucagon
a hormones that is antagonistic to insulin, it releases glucose into the blood
What happens as a result of the release of glucagon? (2)
- glucose is released from glycogen in the liver and muscles
- blood glucose concentration is increased
Islets of Langerhans
cells in the pancreas that regulate glucose concentration
What types of cells in the pancreas release glucagon?
alpha cells
What types of cells in the pancreas release insulin?
beta cells
When is insulin released?
after eating because blood glucose levels are elevated
When is glucagon released?
after fasting because blood glucose levels are low
In order, what is broken down after glucose runs out? (3)
- glycogen
- adipose tissue
- muscle
Why is it dangerous to breakdown muscle for energy?
it decreases the pH of the blood
Diabetes (2)
- a metabolic disease that concerns blood glucose concentration
- there are two types
Type 1 Diabetes
an autoimmune disease where the beta cells of the pancreas are destroyed and thus insulin is not produced
What does being unable to make insulin mean?
glucose is not stored away
How is type 1 diabetes treated?
taking insulin injections
In what states of health can patients with type 1 diabetes be in? (2)
- hyperglycemic
- hypoglycemic
Hyperglycemic
without insulin, resting muscles cannot take up glucose, so muscle, proteins, and fat are broken down rather than glucose
What is a possible result of hyperglycemia? (2)
- ketoacidosis, where dehydration occurs and pH of blood drops
- can result in coma and death
hypoglycemia
leads to coma and death if left untreated
Type 2 Diabetes (2)
- insulin resistant diabetes where the patient has elevated levels of insulin
- cells have lost the ability to recognize insulin
How do cells lose the ability to recognize insulin?
over time, too much blood sugar accumulates and it reduces the body’s ability the to recognize insulin
What is the result of a reduced ability to recognize insulin?
glucose is stored away more slowly
How is type 2 diabetes treated? (3)
- diet
- exercise
- medication
How is exercise a form of treatment for type 2 diabetes?
activity can remove some of the excess glucose in the blood
What state of health is a patient with type 2 diabetes in?
hyperglycemic
How is fiber helpful to someone with type 2 diabetes?
it helps get rid of toxins
What happens if type 2 diabetes is left untreated? (2)
- sugar will deposit in various areas of the body which can cause blindness or limb loss
- liver and kidneys can have decreased function
What hormones does the thyroid produce? (2)
- T3
- T4
What is another name for the T4 hormone?
thyroxine
What are the functions of thyroxine? (3)
- increases body temperature
- regulates bone growth and neural development
- regulates fat, carb and protein metabolism
What is required to produce thyroxine?
iodine (salt)
What happens as a result of an iodine deficiency?
a goiter appears
What glands also regulate hormone levels? (2)
- hypothalamus
- pituitary glands
Which hormones affect hunger and satiety? (2)
- leptin
- ghrelin
Leptin (2)
- released by adipose tissue to decrease hunger
- this acts on the hypothalamus
Ghrelin
released by the GI tract and is released when the stomach is empty, and stops release when the stomach is stretched
How does leptin relate to obesity?
obesity often leads to cells being resistant to leptin even though levels are higher in blood
What can throw off the balance of leptin and ghrelin?
dramatic weight loss
Melatonin (3)
- regulates the sleep cycle
- anticipates darkness
- released in darkness
Where is melatonin produced?
the pineal gland
What disrupts melatonin? (2)
- light from phones
- jet lag from travelling across time zones
What hormone does melatonin interact with?
leptin
Excretion
the removal of the wastes created by metabolic activities
Why is excretion crucial for organisms?
the products are harmful to keep
What is the primary waste product in plants? (2)
- oxygen
- must be excreted because it is reactive
What is the primary waste product in animals? (2)
- carbon dioxide, which comes from cellular respiration
- must be excreted because it lowers the pH of the blood
What does protein digestion result in?
surplus amino acid components, which must be removed
What do fish excrete?
ammonia
What do birds excrete? (2)
- pasty insoluble liquid
- this is because they do not carry much water
What do mammals excrete? (2)
- urea in their urine
- whether or not it is concentrated or diluted depends on the mammal’s water intake
What are the components of the kidney? (6)
- renal vein
- renal artery
- ureter
- medulla
- pelvis
- cortex
Urea
a nitrogenous waste product which humans remove in urine
What is advantageous to do in excretion?
conserve as much water as possible
How is water balance achieved?
balancing salt and hormone concentration in the kidney
What processes is the kidney responsible for? (3)
- filtration
- reabsorption
- secretion
How is water lost? (3)
- sweating
- urination
- breathing
How is salt lost?
sweating
Nephron (2)
- functional unit of the kidney
- these are supplied with blood by a renal artery which receive about 20% of cardiac output
What does the nephron consist of? (6)
- glomerulus
- Bowman’s capsule
- proximal convoluted tubule
- loop of Henle
- distal convoluted tubule
- collecting duct
What is the purpose of a nephron?
to balance the good and the bad
Where do conserved products from the blood go?
back into the bloodstream to the body
Where do waste products from the blood go?
through the ureters to the bladder to exit the body
Glomerulus
a bundle of blood vessel that allows for filtration of small solutes via a pressure gradient
Where is the glomerulus located?
within the Bowman’s capsule
Where does blood enter and exit in the glomerulus? (3)
- blood enters through the afferent arteriole
- blood exits through the efferent arteriole
- both branch off from the renal artery
How does filtration in the glomerulus occur? (2)
- filtration occurs as blood pressure forces fluid of from the the blood in the glomerulus into the lumen
- the porous capillaries are permeable to water and small solutes, but not blood cells or large molecules such as proteins
How does pressure play a role in the ultrafiltration of the glomerulus? (4)
- there is a pressure difference between the afferent and efferent arterioles
- the afferent arteriole has more space, so pressure is lower
- the efferent arteriole has less space, so pressure is higher
- this pressure helps sift out smaller molecules
How has filtered blood changed after going through the glomerulus?
it is 20% of the original volume
What does filtrate contain after going through the glomerulus? (5)
- salt
- electrolytes
- glucose
- vitamins
- urea
Proximal Convoluted Tubule (PTC) (2)
- nutrients must be absorbed back into circulation so it pumps things out of the urine
- solute transport substantially changes the composition of the filtrate
How are nutrients moved in the PTC?
via active transport for reabsorption
What nutrients are reabsorbed in PTC? (3)
- glucose
- amino acids
- vitamins
What is the structure of the PTC? (2)
- single layer of cells for easy transport
- microvilli to increase surface area
What is an important function of the PTC?
reabsorption of most of the salt and water from the initial filtrate
How does Na+ move across PTC?
actively
How does Cl- move across the PTC?
passively
How does water move across the PTC?
via osmosis
Where does most water and glucose go from the PTC?
back into circulation rather than being excreted in the urine
What happens to glucose in the PTC for diabetics?
there is an increased blood glucose, so not all of it is reabsorbed
Loop of Henle (2)
- composed of the descending and ascending limbs, main role is to increase solute concentration in the medulla
- reabsorption of water continues as the filtrate moves into the descending limb of the LoH
Descending Limb (2)
- freely permeable to water, but not to salt
- for water to move out by osmosis, the interstitial fluid bathing the tubule must be hypertonic to filtrate
What is the purpose of the descending limb?
to increase water absorption
Ascending Limb (2)
- permeable to salt, but not water
- as filtrate goes up the ascending limb, NaCl is secreted out of the tubule into the interstitial fluid
What is the purpose of the ascending limb?
to pump salt
What is filtrate like when it leaves the LoH?
it still has relatively large amount of water
Collecting Duct(2)
- where water is released depending on the body’s need for it
- permeable to water, but not salt or urea
How does urine become more concentrated?
as water is reabsorbed by osmosis
What does the collecting duct do if the body is in need of water? (3)
- more water will be reabsorbed by the collecting duct
- the hypothalamus produces and the posterior pituitary releases Anti-Diuretic Hormone (ADH)
- ADH creates aquaporins in the duct for water to pass through
What does the collecting duct do if the body is not in need of water? (3)
- if there is excess water in the body, ADH is not released
- water can be excreted along with urine
- this is negative feedback because ADH prevents additional water loss
Why does alcohol inhibit ADH? (2)
- alcohol is mainly composed of water
- this is why people get dehydrated
