Chapter 48: Regulating the Internal Environment

Of the 13 essential vitamins, ____ are water soluble and ____ are fat soluble.

9,4

Vitamin __________ is produced in human skin when exposed to sunlight.

D

A deficiency of __________ produces a goiter in humans.

iodine

Food is formed into a bolus in the ____________ .

mouth

The ___________ layer of the digestive tract in mammals is in direct contact with the lumen.

mucosa

The ____________ layer of the mammalian gut performs peristalsis.

muscularis

Heartburn is caused by the ________________ .

gastroesophageal sphincter remaining a bit

open

The ____ digestive structures in humans secrete amylase.

pancreas and salivary glands

Most peptic ulcers are caused by ____.

Bacteria (helicobacter pylori)

The majority of absorption in the digestive process in the human body takes place in the ____.

small intestine

Homeostatic Control Systems

compensate for changing conditions and maintain the internal environment within the relatively narrow limits that cells can tolerate

osmoregulation

is the regulation of water and ion balance

excretion

•helps maintain the body's water and ion balance while ridding the body of metabolic wastes

Thermoregulation

•is the control of body temperature

Osmosis

Diffusion of water through a selectively permeable membrane from a region of higher water concentration (low solute concentration) to a region of lower water concentration (high solute concentration)

osmolarity

total concentration of all solute particles in a solution

Osmolarity of body fluids in humans and other mammals

300 mOsm/L

hyperosmotic

higher osmolarity

hypoosmotic

lower osmolarity

isoosmotic

same osmolarity on either side of a membrane

osmolarity of saline

Osmolarity of saline 0.9% NaCal - 308 mOml/L

osmoconformers

the osmolarity of cellular and extracellular solutions matches that of the environment

osmoregulators

use control mechanisms to keep the osmolarity of cellular and extracellular fluids the same, but at levels that may differ from the osmolarity of the surroundings

Most Conformer Animals

Aquatic animals

Most Regulator Animals

Terrestrial Animals

Freshwater v Saltwater fish

Freshwater fish need to gain ions and lose water, saltwater fish need to lose ions and gain water.

The freshwater fish are constantly pumping water out so that they don't swell up to their their salty in interior

osmoles

the number of solute molecules and ions (in moles) per liter of solution

How do animals control osmolarity?

Removing certain substances from body fluids and releasing them into the environment ;

animals excrete H+ ions, nitrogenous products of metabolism, and breakdown products of poisons and toxins

; excretion of ions and metabolic products is accompanied by water excretion - water is a solvent for those molecules ;

animals that take in large amounts of water may also excrete water to maintain osmolarity

What animals excrete

H+ ions and nitrogenous products

Water excretion

Excretion of ions and metabolic and metabolic products

what animals would excrete water to maintain osmolarity

animals that take in large amounts of water

Is excretion tied to osmoconformers or osmoregulators

Osmoreguators

Why is H+ excreted

Keep pH of body near neutral level

transport epithelium

microscopic tubules carrying out osmoregulation and excretion

Distal end of tubule

open to the body exterior

Proximal End

Body fluids (kidney in humans)

transport proteins

move specific molecules and ions into and out of the tubule by either active or passive transport, depending on the substance and its concentration gradient

4 Steps of Tubule Function

1. filtration

2. tubular reabsorption

3. tubular secretion

4. excretion

Filtration

the nonselective movement of water and solutes, but not large molecules such as proteins, into the proximal end of the tubules through spaces between cells

Tubular reabsorption

Important molecules (e.g., glucose and amino acids) and ions are transported by the transport epithelium back into the ECF and eventually into the blood as the filtered solution moves through the excretory tubule

Tubular secretion

3.is a selective process in which specific small molecules and ions are transported from the ECF and blood into the tubules

Excretion

3.Fluid (urine) containing waste materials is released into the environment from the distal end of the tubule - in some animals, waste fluids are concentrated into a solid or semisolid form

Secretion vs. Reabsorption

metabolic water

•used in chemical reactions and is involved in physiological processes such as the excretion of wastes

ammonia, urea, uric acid

nitrogenous products of the breakdown of proteins, amino acids, and nucleic acids

factors of the waste

•produced depends on a balance among toxicity, water conservation, and energy requirements

ammonia (NH3)

•the result of a series of biochemical steps beginning with the removal of amino groups (—NH3+) from amino acids as a part of protein breakdown

ammonia

soluble in water, but highly toxic - it must be either excreted or converted to a nontoxic derivative

where ammonia can be excreted

in dilute solutions

What animals excrete ammonia

aquatic invertebrates, teleosts, and larval amphibians

What converts ammonia to urea

all mammals, most amphibians, some reptiles, some marine fishes, and some terrestrial invertebrates combine ammonia with HCO3

Pros and Cons of urea production

requires more energy than forming ammonia, excreting urea instead of ammonia requires only about 10% as much water

Animals that make uric acid instead of urea or ammonia

terrestrial invertebrates, reptiles, and birds form uric acid

uric acid

nontoxic and insoluble - it precipitates in water as a crystal and can be excreted as a concentrated paste

how much nitrogen does uric acid have

•four times as much nitrogen as ammonia

how much water does uric acid exretion conserve

99%

Fish in Bowl concept

die from ammonia build up if not regulated

KNOW TABLE ON SLIDE 29 OF EXCRETORY SYSTEMS

marine invertebrates

•osmoconformers - the osmolarity of their intracellular and extracellular fluids and the surrounding seawater is the same, about 1,000 mOsm/L

freshwater invertebrates

osmoregulators - they must expend energy to excrete excess water to keep their internal fluids hyperosmotic to their surroundings

how do they actively transport salt ions

from the water, through skin or gills, into their bodies

•invertebrate osmoregulators use three types of tubules for carrying out excretion:

1.Protonephridia,

2.Metanephridia,

3.Malpighian

Protonephridia

1.the simplest form of excretory tubule, found in flatworms and larval mollusks

Metanephridia

found in annelids and most adult mollusks

Malpighian tubules

found in insects and other arthropods

flame cells (protonephridia)

Specialized hollow excretory or osmoregulatory structure composed of one or several small cells containing a tuft of flagella and situated at the end of a minute tubule; connected tubules ultimately open to the outside

Interdigitating example

Fingers intertwined

hemolymph

passes through protonephridia, some molecules and ions are reabsorbed, and nitrogenous wastes are secreted into the tubules

urine (protonephridia)

released through pores at the distal ends of the tubules where they reach the body surface

metanephridia in earthworms

•a pair of metanephridia are located in each body segment, one on each side of the body

•hemolymph enters a funnel-like proximal end surrounded with cilia

•some molecules and ions are reabsorbed

•nitrogenous wastes are secreted into the tubule and excreted from the distal end at the body surface

malpighian tubules

•grasshopper

•have a closed proximal end immersed in hemolymph

•distal ends empty into the gut

•tubules secrete K+ into the lumen of the proximal segment, which draws in Cl- from the hemolymph

•water follows the KCl

•uric acid is secreted into the tubule

•when fluid reaches the hindgut, K+ `and Cl- are reabsorbed, followed by water

•uric acid precipitates as crystals - released with feces

nephrons

Functional units of the kidneys

Urine Processing

Urine is processed in collecting ducts, then drains through the renal pelvis, ureter, urinary bladder, and urethra

loop of Henle

descends through the medulla and returns to the cortex

differences in permeability along the nephron

1.established by specific membrane transport proteins in each region

increases from the renal cortex to the deepest levels of the renal medulla

a concentration gradient of molecules and ions in the interstitial fluid of the kidney

UNDERSTAND THE ORDER FOR RENAL CORTEX SLIDE 40

glomerular filtration

•occurs in Bowman's capsule, which cups around a ball of arterial capillaries (the glomerulus)

Bowman's capsule

cups around a ball of arterial capillaries

glomerulus

a ball of arterial capillaries

proximal convoluted tubule

•descends into the renal medulla in a U-shaped bend called the loop of Henle and then ascends again to form a distal convoluted tubule

loop of Henle shape

U shaped bend

peritubular capillaries

reabsorb important molecules and ions from the filtrate

Filtration in Bowman's Capsule

•glomerular capillaries have pores that make them more permeable to water and solutes than other capillaries

•blood pressure drives fluid containing solutes through the pores of the capillaries into Bowman's capsule - blood cells and plasma proteins are retained in the capillaries

•the diameter of the afferent arteriole delivering blood to the glomerulus is larger than that of the efferent arteriole - maintaining a high level of glomerular capillary pressure

afferent arteriole

The small artery that carries blood toward the capillaries of the glomerulus.

efferent arteriole

The small artery that carries blood away from the capillaries of the glomerulus.

Reabsorption in the PCT

•Na+/K+ pumps in the epithelium of the convoluted tubule move Na+ and K+ from the filtrate into the interstitial fluid surrounding the tubule

•a voltage gradient causes Cl- ions to be reabsorbed from within the tubule with the positive ions

•specific active transport proteins reabsorb glucose, amino acids, and other nutrient molecules into the interstitial fluid, making the filtrate hypoosmotic to the interstitial fluid

•water moves from the tubule into the interstitial fluid by osmosis - aided by transport proteins (aquaporins)

•nutrients and water that entered the interstitial fluid move into the capillaries of the peritubular network

•H+ ions enter the tubule by active transport - products of detoxified poisons (from the liver) enter by passive diffusion

•reabsorbed ions, nutrients, and water are transported into the interstitial fluid, then into peritubular capillaries

Descending loop of henle Functions

•filtrate leaving the proximal convoluted tubule enters the descending segment of the loop of Henle, where water is reabsorbed

•this segment descends through regions of increasingly higher solute concentrations in the interstitial fluid of the medulla - water moves out of the tubule through aquaporins

•osmolarity of the filtrate gradually increases to a peak of about 1,200 mOsm/L at the bottom of the loop

asending loop of henle function

•the ascending segment has membrane proteins that transport salt ions, but no aquaporins - water is trapped, while salt ions move out of the tubule

•reabsorption of salt ions helps establish the concentration gradient of the medulla - high near the renal pelvis and low near the renal cortex

•at the top of the ascending loop, filtrate osmolarity has dropped to about 150 mOsm/L

Secretion via the DCT

•additional water is recovered by osmosis from the fluid in the distal convoluted tubule in response to hormones triggered by changes in the body's salt concentrations

•varying amounts of K+ and H+ ions are secreted into the fluid, and Na+ and Cl- ions are reabsorbed - urea and other nitrogenous wastes remain the same

•by the time the fluid (urine) enters the collecting ducts, it is isoosmotic with blood plasma (about 300 mOsm/L) but very different in composition

Concentrating via Collecting Ducts:

•collecting ducts are permeable to water but not salt ions

•as they descend from the cortex through the medulla of the kidney, they encounter an increasing solute concentration

•water moves out osmotically, increasing the concentration of the urine - up to 1,200 mOsm/L at the bottom of the medulla

•passive urea transporters near the bottom of the medulla contribute to the concentration gradient of solutes in the medulla

•the hyperosomotic state of the interstitial fluid toward the bottom of the medulla would damage the medulla cells if they were not protected against osmotic water loss

•the protection comes from high concentrations of otherwise inert organic molecules called osmolytes in the cytoplasm of these cells

•the osmolytes, primarily a sugar alcohol called sorbitol, raise the osmolarity of the cells to match that of the surrounding interstitial fluid

LEARN TABLE ON 50

thermoregulation

temperature regulation

thermoreceptors

detect changes in temperature

temperature regulation definition

•is based on negative feedback pathways in which temperature receptors (thermoreceptors) detect changes from a set point

signals from receptors trigger

•physiological and behavioral responses that return the temperature to the set point

all responses triggered by negative feedback mechanisms involve adjustments in rate of heat-generating oxidative reactions within the body

•coupled with adjustments in rate of heat gain or loss at the body surface

example of heat generating oxidativereactions within the body

shivering

0°C to 45°C range of tolerable temperatures

•an animal's organismal performance (biochemical, physiological, and whole-body processes) varies greatly