Week 9 Flashcards
1
Q
Oxygen binding to hemoglobin in the blood is affected by different physical and chemical conditions, such as the blood’s _____
and _____.
A
Temperature and pH.
2
Q
Carbon dioxide produced during cellular metabolism is converted to which of the following compounds inside of red blood cells?
A
Bicarbonate ions
3
Q
The presence of hydrogen ions has which of the following effects on hemoglobin?
A
More oxygen molecules are released from hemoglobin.
4
Q
The Bohr effect is illustrated on the oxyhemoglobin dissociation curve as a shift to the
_______ .
A
Right
5
Q
The most important characteristic of all organisms with a gastrovascular cavity is
A
having bodies only several cells thick.
6
Q
The binding of oxygen to hemoglobin is influenced by other factors such as ______.
A
Temperature
pH
7
Q
Pseudocoelomates achieve adequate ______
by moving their body against the body fluids.
A
circulation
8
Q
Carbon dioxide lowers the pH of blood by combining with water to produce _______ acid which dissociates into a _________ ion and a proton.
A
Blank 1: carbonic
Blank 2: bicarbonate, HCO3-, or HCO3
9
Q
Elevated temperatures has which of the following effects on the binding of oxygen to hemoglobin?
A
Decreases the affinity of hemoglobin for oxygen
10
Q
The effect of pH on hemoglobin’s affinity for oxygen is known as the ______.
A
Bohr effect
11
Q
If you wanted to find an animal from a phylum that commonly exemplifies an open circulatory system, you would select a/an
A
arthropod
mollusk (except cephalopods)
12
Q
Animals that have gastrovascular cavities have which characteristic?
A
They are all a few cells thick.
Reason: they would not have a gastrovascular cavity
13
Q
The circulating fluid and the extracellular fluid of an animal with an open circulatory system are the same. This fluid is called
A
Hemolymph
14
Q
Which pseudocoelomate uses the fluids of the body cavity for circulation?
A
Rotifer
Roundworm
15
Q
After circulating through the channels and cavities of the body of an insect, the hemolymph drains back into the ________
cavity.
A
central
16
Q
In earthworms, a ________
vessel contracts to function as a pump and blood is sent to 5 small connecting arteries.
A
dorsal
17
Q
The nitrogen in amino acids and other nitrogen containing molecules in animals is excreted in the form of which of the following?
A
Nitrogenous wastes
18
Q
Animals in the phylum Arthropoda typically have _________
circulatory systems.
A
open
19
Q
True or false: All animals produce a combination of ammonia, urea, and uric acid as their nitrogenous waste.
A
False, different animals usually produce one of the three nitrogenous wastes, depending on the species and environment they live in.
20
Q
The fluid that bathes tissues of invertebrates with an open circulatory system is called
A
hemolymph.
21
Q
Which are forms of nitrogenous waste typically excreted by animals?
A
Urea
Uric acid
Ammonia
22
Q
The insect heart first pumps hemolymph into
A
channels
23
Q
This vessel moves blood posteriorly in the earthworm.
A
Ventral vessel
24
Q
Are any waste products generated from the breakdown of protein and if so, what is their nature?
A
Yes; nitrogenous wastes
25
How many different kind(s) of nitrogenous waste do most animals produce?
One
26
The three main forms of nitrogenous waste are ammonia, ______
and ______ acid.
Blank 1: urea
| Blank 2: uric
27
How do heterotrophs gain energy?
By eating other organisms
28
What are herbivores, carnivores and omnivores?
• Herbivores- Eat mainly autotrophs (plants & algae)
• Carnivores- Eat other animals
• Omnivores-Regularly consume animal as well as
plant or algal matter
29
What is a characteristic of most animals?
most animals are opportunistic – deer
may eat invertebrates as well as plants.
--Most animals are opportunistic, eating foods that are outside their main dietary category when these foods are available to them. E.g. cattle and deer may occasionally eat small animals, invertebrates or bird eggs.
30
The diets of animals must satisfy three nutritional needs: What are these 3 needs?
1. Fuel for cellular work.
2. Raw materials for biosynthesis.
3. Essential nutrients
31
Why do animals need fuel for cellular work?
Conversion of nutrients into energy for movement, growth, reproduction
32
Why do animals need raw materials for biosynthesis?
Sources of organic carbon and nitrogen to make complex molecules, such as CH & fats
33
Why do animals need essential nutrients?
Items that cannot be biosynthesised
34
What are some essential nutrients?
```
Essential AA
Essential Fatty acids
Vitamins
Minerals
EAA, EFA, VITAMINS- are pre assembled organic molecules.
```
35
Why are EAAs needed?
20 AAs required to build proteins. Approx. ½ are synthesized; 8 are EAAs.
Meat contains all AAs; plants do not.
-- Many plants may lack EAA such as maize which lacks lysine which can lead to niacin or vitamin B3 deficiency and pellagra (is a condition which leads to symptoms such as inflamed skin, diarrhea, dementia and sores in the mouth and the areas in the skin that are exposed to sunlight or friction are typically affected first.
--Are 8 essential amino acids- isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
36
Why are EFAs needed?
Animals can synthesise most FAs. EFAs (e.g. linoleic acid) common in food.
37
Why are vitamins needed?
Usually required in small amounts. (Vit A for opsins; Vit D for bones; Vit C).
38
Why are minerals needed?
(simple inorganic nutrients)
| Ca2+; P: ATP, nucleic acids
39
Why may malnutrition occur and what does it cause?
can occur when there is a long term absence of one or more essential nutrients.
- --deformities, disease, death
- --Malnutrition is most commonly due to a deficiency in proteins, i.e. a failure to acquire EAA and its rarely attributed to a deficiency in EFA.
40
Animal behaviour is influenced by the
need to obtain essential nutrients.
41
Herbivores living where soils are deficient in essential minerals will eat
bones or visit salt licks to obtain these nutrients.
42
What are the 4 stages of food processing?
Stage 1- Ingestion
Stage 2-Digestion
Stage 3- Absorption
Stage 4-Elimination
43
What is ingestion?
Consumption of food via oral cavity.
44
What is digestion?
Food broken down into molecules small enough for the body to absorb.
The process of breaking down food by mechanical and chemical digestion, into molecules small enough to absorb.
--Digestion is the process of breaking down food into small molecules that can be absorbed. Occurs in two phases.
45
What is absorption?
of small molecules into cells.
46
What is Elimination?
Undigested material passed out of body.
47
Stage 1-
| What are suspension feeders?
* Sift small food particles from water.
* Could have mucus, tentacles, filters
* EXAMPLES: clams, baleen whales, flamingos.
48
Stage 1-
| What are Fluid feeders?
* Suck nutrient-rich fluid from living host.
| * EXAMPLES: aphids, mosquitoes, hummingbirds.
49
Stage 1-
| What are Substrate feeders?
* Live in or on their food source.
| * EXAMPLES: caterpillars, maggots, parasites.
50
Stage 1-
| What are Bulk Feeders?
Eat relatively large pieces of food.
• Most common method among animals.
• EXAMPLES: snakes, wolves, tigers.
51
Stage 2- What are the two types of digestion?
Mechanical and chemical
52
What is mechanical digestion?
Increases surface area of food.
| Using teeth or gizzard, for example.
53
What is chemical digestion?
Splits food into small molecules that can pass through cell membranes.
--- During chemical digestion polysaccharides are split into monomers. Fats are converted to glycerol and fatty acids and proteins are cleaved into AA.
54
What is Enzymatic hydrolysis in chemical digestion?
splits bonds in molecules with the addition of water.
55
What is intracellular digestion?
Food particles ingested by phagocytosis.
| Food vacuoles fuse with lysosomes containing hydrolytic enzymes.
56
What is extracellular digestion?
(most animals)
Occurs in compartments that are continuous with the outside of the animal’s body.
• Breakdown of food particles outside cells
• Absorption of simple molecules into cells
57
What are properties of animals with simple body plans?
• Have a gastrovascular cavity that
functions in both digestion and the distribution of nutrients.
• Hydra (Cnidaria) gather food into the mouth using their tentacles & release enzymes into gastrovascular cavity to break down food & then ingest food particles into cells by phagocytosis.
• Undigested food is eliminated back out through the mouth.
58
What are properties of animals with more complex body plans?
• Have a digestive tube called an alimentary canal, which is often folded to maximize surface area.
• Food moves through in a single direction, and so the tube can be
organised into specialised compartments to carry out digestion and nutrient absorption in a stepwise fashion.
• New meals can be ingested while older meals are being absorbed.
59
stage 2- What are evolutionary adaptions in the oral cavity?
* Teeth
* Tongue
* Saliva
60
stage 2-What are some Specialisations of the oral cavity?
• First stage of digestion begins in the mouth and is mechanical and enzymatic.
• Dental adaptations aid prey capture and digestion. High level of specialisation in mammalian teeth. Teeth chew(masticate) food into smaller particles that are exposed to salivary amylase, initiating breakdown of glucose polymers.
• Saliva lubricates food to facilitate swallowing and the tongue shapes food
into a bolus and assists with swallowing.
61
Stage 2- What are some Dental specialisations in mammals?
CARNIVORES
- -Elongated incisor teeth- For capturing prey.
- - Carnassial teeth- Modified molars/pre-molars for shearing meat.
```
HERBIVORES-
-- Large flat molars- Grinding down tough
plant cellulose.
--Hypsodonty- Protection against
wear (grit in food).
```
62
Stage 2- What are some Specialisations of salivary glands?
* Venomous snakes and lizards have highly modified saliva.
* Contains powerful zootoxins.
* Fangs to inject venom deep into tissue.
* Vampire bats Desmodus spp. produce an anticoagulant (draculin) which inhibits coagulant factors in blood.
* Also includes compounds that prevent the constriction of blood vessels.
* Incisors specialised for cutting.
* Specialised thermoreceptors on nose to find place where blood near surface.
63
What are the properties of humans needed for digestion?
* Tubular gastrointestinal tract
* Swallowed food enters esophagus
* Smooth muscle contraction: peristalsis
* Rhythmic contractions move bolus
* Food stored in stomach (early digestion)
* Accessory digestive organs
64
What some properties of birds helping them in digestion?
Lack teeth
Break up food in 2-chambered stomach
Gizzard
65
What are gizzards?
Gizzard – small pebbles ingested by the bird grind up seeds/plants by muscular action.
Gizzard is essentially another chamber of the stomach that acts to grind up food stuff like seeds and plants, and it does this using tiny little pebbles that have been previously ingested by the organism.
66
What are some Specialisation of the stomach?
- -The stomach stores food & secretes gastric juice which kills bacteria & denatures proteins – food ‘chyme’.
- --Gastric juice is made up of hydrochloric acid (HCI) and pepsin (low pH of about 2).
67
How do we prevent digestion of own cells?
Parietal cells
Chief cells
Mucus
68
What are parietal cells?
Secrete hydrogen and chloride ions, which combine in the lumen.
69
What are chief cells?
Secrete inactive pepsinogen which is
| activated to pepsin when mixed with HCI.
70
Why is Mucus needed?
Protects stomach lining from gastric juice
71
What are some Specialisations of the small intestine?
* The small intestine is the longest section of the alimentary canal, and the major organ for chemical digestion and absorption.
* Following starch digestion in mouth and protein digestion in stomach, most digestion occurs in the first portion (25-35 cm in humans) of the small intestine, the duodenum.
* Here, acid chyme from the stomach mixes with digestive juices from the accessory glands and from cells lining the duodenum.
72
What are some accessory glands of the small intestine?
Pancreas
Liver
• Epithelial cells
73
Why is the pancreas needed?
functions as an exocrine gland - secretes additional proteases (trypsin and chymotrypsin). The solution is alkaline, and so neutralises the acidic chyme.
74
Why is the liver needed?
Liver produces bile, which is stored in the gall bladder.
| • Bile: no enzymes but contains salts and aids in the digestion and absorption of fats.
75
Why are the Epithelial cells beneficial?
lining the duodenum produce several other digestive enzymes.
76
What does the pancreas also function as?
Pancreas also functions as an endocrine gland – secreting hormones into blood to control levels of glucose and other nutrients
77
Stage 3-
| What are some of the properties of the small intestine?
• Huge surface area, approx. 300m2 in humans (size of a tennis court)
• Highly folded surface with projections called villi.
• Epithelial cells of a villus have many microvilli
• ‘Brush Border’
Highly vascularised
Nutrient-rich blood flows to the liver via the hepatic portal vein
78
Outline the Absorption of the products of digestion
(A) Monosaccharides and amino acids are transported into blood capillaries
(B) Fatty acids and monoglycerides within the intestinal lumen are absorbed and converted within the intestinal epithelial cells intro triglycerides (often coated with proteins to form chylomicrons, which enter lymphatic capillaries.
79
Crypt base columnar cells (CBCs) can
can differentiate into four cell types:
| Paneth cells; Enteroendocrine cells; Goblet cells and Absorptive epithelial cells (enterocytes)
80
What are some of the Specialisations of the large intestine?
• Larger in diameter than small
| intestine; small intestine is longer.
81
What is the cecum?
* Connects where the small and large intestine meet.
* Not to be confused with the Appendix (plays a minor role in immunity; NOT in digestion) and may act as a safe house from which beneficial bacteria can recolonise the intestine following illness.
82
In most vertebrates, other than mammals, the waste products emerge from
the large intestine into the cloaca
83
The cloaca (cavity) also receives products from the
urinary and reproductive systems – all are eliminated via the anus.
84
What does the colon do in the large intestine?
Colon: recovers water from the alimentary canal. Waste becomes increasingly solid as water is reabsorbed.
• Colon houses bacteria (1/3 of the dry weight of faeces) which live on unabsorbed organic material.
• Some of the bacteria produce vitamins that are absorbed and supplement the diet of the animal.
85
What does the rectum do in the large intestine?
stores feces before being eliminated.
86
How is cellulose digested?
Much of the chemical energy in the diet of herbivorous animals is contained in the cellulose of plant cell walls, which animals cannot digest themselves.
--Mutualistic communities of microorganisms can break down cellulose.
87
What does the cecum contain?
Cecum is significantly enlarged (2.5 m) in many herbivorous mammals, such as the koala.
Cecum contains mutualistic communities
of microorganisms that can break down cellulose
88
What do termintes and Iguanas do?
Termites:
• Eat mainly wood, and house bacteria and protists in their hindgut that break down cellulose.
Iguana:
• Has a microbial flora in its hindgut
• Hatchlings raised in captivity do less well than those raised in the wild due to lack of fermentation microflora
89
What are ruminants?
have a specialised fermentation chamber called a rumen that houses complex communities of microorganisms.
90
What are the properties of the four chambered stomach?
1. Rumen
2. Reticulum (cellulose digestion),
3. Omasum (water absorption),
4. Abomasum (protein digestion).
91
What is the cud?
* Periodically, the animal regurgitates and rechews the cud to accelerate digestion. Cud reswallowed along with many microorganisms and digested and absorbed.
* Microorganisms reproduce rapidly in the rumen, maintaining a stable population.
92
Why do rabbits eat their poo?
Rodents and lagomorphs: also ferment their food with the aid of microorganisms
• Rodents ingest soft faeces that are products from the cecum – coprophagy
• Lagomorphs swallow the faeces whole and they lodge in the stomach where
they continue to ferment for several hours.
• Analogous to fermentation in the rumen
• Allows better absorption of nutrients
93
Mutualistic communities of microorganisms break down
cellulose
94
Why do we have gas exchange systems?
for extracting O2 from the environment and excreting CO2
95
Why do we have a circulatory systems?
for transporting respiratory gases from exchange organs to body cells
96
All organisms must
exchange materials with their environment
97
What are unicellular organisms?
exchange materials directly, via diffusion, with the environment.
98
What are multicellular organisms?
that are small and/or thin may also exchange materials directly with the environment.
99
What have bigger more complex organisms evolved?
Bigger, more complex organisms evolve specialised exchange organs and
internal transport systems that connect organs of exchange with body cells.
100
What are some essential aspects of gas exchange?
- -Oxygen must be extracted from the environment (air or water) for cellular respiration.
- -Respiration at the whole-body level involves uptake of O2 from the environment and excretion of CO2.
- -Respiration at the cellular level releases energy from organic molecules (glucose) as ATP.
* Gas exchange across respiratory surfaces takes place by diffusion, and organs of exchange vary by animal.
101
Diffusion of respiratory gases is a
passive process
102
Where does gas diffuse from?
Gas diffuses from a region of higher partial pressure to a region of lower partial pressure.
103
What is Fick's Law of diffusion?
R = k x a (p1 – p2)/ d
```
R= rate of diffusion
k = diffusion coefficient
a = area for diffusion
p1 – p2 = pressure gradient
d = distance for diffusion
```
104
Diffusion coefficient (k) is a
constant that is linked to the solubility of a gas in a medium.
105
Gas exchange occurs across
specialised respiratory surfaces
106
To maximise gas exchange animals
| have respiratory organs that:
1. Maximise surface area
2. Maximise pressure gradient
3. Minimise distance for diffusion
107
What are some respiratory adaptions?
Gas exchange in aquatic and terrestrial organisms
```
• Aquatic organisms
- Gills
- Countercurrent exchange mechanisms
- Ventilation
• Terrestrial organisms
- Lungs
- Mammals, amphibians, insects
```
108
What are some respiratory adaptations of aquatic organisms?
* Gills
* Countercurrent exchange mechanism
* Ventilation
109
How is gas exchanged in water?
• Oxygen is not very soluble in water, so the concentration of O2 is much lower in water than in air.
• Diffusion rate of oxygen in water is 5,000-10,000 times lower than in air.
* Obtaining O2 from water requires greater efficiency than air breathing.
110
Why are the gills highly specialized?
* Gills are highly filamentous, with gill lamellae providing a very large surface area for gas exchange – similar to structure of villi in intestines.
* Gills are highly vascularised, and blood vessels are very close to the surface to minimise distance for diffusion.
* Gills vs Lungs
111
What would the countercurrent exchange system look like in gills?
* Maintains a continuous pressure gradient between water and blood.
* Blood flows in the opposite direction to water passing over the gills.
* Thus, blood is always less saturated with O2 than the water it meets.
* O2 moves out of water and into blood down a diffusion gradient.
112
Where is the oxygen concentration always higher?
Oxygen concentration is always higher in the water than in the blood: diffusion occurs.
113
What is ventilation in aquatic animals?
--Aquatic animals move through the water and channel water over their gills by
passive ventilation.
--Moves the respiratory medium over the respiratory exchange surface.
--Maintains a high pressure gradient for respiratory gases between the body and the environment.
--Aquatic animals ventilate gills by buccal pumping, ram ventilation or jet propulsion.
114
What is Buccal pumping?
Two cavities expand alternately to pump water: mouth - past gills - out via the operculum.
115
What is an example of ram ventilation?
Swimming fast with mouth partially open to ventilate gills.
116
What are some respiratory adaptations of terrestrial organisms?
* Air has a higher oxygen concentration than water
* Diffusion is faster in air than in water
* Lungs are internal - large SA:V, short diffusion distance
* Fick’s Law
117
Outline the respiratory exchange systems in insects.
```
--The tracheal system of insects consists
of tiny branching tubes (tracheoles)
that penetrate the body.
--Air enters the largest tubes (tracheae)
through spiracles on the body surface.
--Tracheoles supply O2 directly to body
cells across a moist epithelium.
--Larger insects must ventilate their
tracheal system using air sacs to meet
O2 demands – beating of wings.
```
118
Respiratory exchange systems in amphibians
- -Ventilate lungs by positive pressure breathing – forcing air in and out of lungs.
- -Small lungs, with no ribs or diaphragm.
- -Also respire across skin, which must remain damp to allow diffusion of gases.
119
What are some examples of amphibian exchange systems?
Coconut crab
• Terrestrial – cannot survive in water
• Has respiratory structures that are intermediate between gills and lungs and remain rigid in air
• Must be kept moist
Lungless salamanders
• Have no lungs
• Breathe through skin
120
Respiratory exchange systems in birds
--Birds have a VERY efficient respiration system, with numerous air sacs that
function like a bellows system.
--Air flows in one direction through parabronchi (small tubes) where gas exchange occurs.
--Incoming air does not mix with stale air, so every exhalation and inhalation
completely renews the air in the lungs.
121
Respiratory exchange in mammals
Trachea
Bronchi
Bronchioles
Alveoli where gas exchange occurs.
Gas must dissolve in fluid before it can diffuse across membranes.
Surfactants
Lower surface
tension of water
122
What is Negative pressure breathing?
pulls air into lungs; Exhalation is passive.
| * Maximum PO2 in alveoli is always less than in the atmosphere.
123
Gas exchange in blood capillaries
PO2 lungs = 105 mmHg
| Oxyhaemoglobin dissociation curve
124
What is the function of a circulatory system?
Inhaled air needs to be circulated to cells.
Circulatory systems connect cells in body
tissues with organs where gas exchange,
absorption of nutrients or disposal of waste products occurs.
125
What are some essential components of a circulatory system?
1. A circulatory fluid (blood)
2. A network of tubes (blood vessels)
3. A muscular pump (heart)
126
What are the two circulatory systems?
Animals may have an open or closed
| circulatory system.
127
Why have respiratory pigments?
* Oxygen is not very soluble in liquid.
--But oxygen is efficiently transported bound to respiratory pigments. Greatly increases the amount of oxygen that blood can carry.
--Most vertebrates and some invertebrates use iron-containing haemoglobin (contained within erythrocytes in vertebrates).
--Arthropods and many molluscs use coppercontaining haemocyanin.
Carbon dioxide is also transported.
128
What is an open circulatory system?
Insects, other arthropods, and most
molluscs have an open circulatory system.
* Blood bathes organs directly (few vessels)
In an open circulatory system there is no
distinction between blood and interstitial
fluid.
This general body fluid is more correctly
called haemolymph.
129
What is a closed circulatory system?
--In closed systems, the blood is separate from the interstitial fluid that bathes the tissues – gas exchange occurs between the two.
* Blood is confined to vessels.
Closed systems are more efficient
at transporting circulatory fluids to
tissues and cells – high pressure.
Humans and other vertebrates
have a closed circulatory system,
the cardiovascular system.
130
What is single circulation?
A single circulation, where blood leaving the heart passes through two capillary beds before returning.
• Two chambered heart – ventricle and atrium.
• Blood pressure drops in capillary beds in gills.
• Muscle contractions while swimming help to accelerate circulation.
131
What do mammals and birds have?
Mammals and birds have a double circulation, where oxygen-rich and oxygen poor blood are pumped separately from the right and left sides of the heart.
Double circulation maintains higher blood pressure in systemic capillary beds than does single circulation.
Left side of the heart receives and pumps only oxygen-rich blood; the right side only oxygen-poor blood. Chambers are completely separate.
Mammals and birds are endotherms and require more O2 than ectotherms. Their CV system meets the body’s continuous demand for O2.
132
What do amphibians have?
Amphibians and reptiles also have a double circulation. Oxygen-poor blood flows through a pulmocutaneous circuit to pick up oxygen through the lungs and the skin.
Have a three chambered heart,
including two atria and one ventricle.
Ridge within the ventricle diverts oxygenpoor and oxygen-rich blood into the PC
and systemic circuits, respectively.
Underwater, blood flow to lungs is almost
completely shut off, but continues to the skin.
133
What are the types of blood vessels?
Velocity: Arteries > Arterioles > Veins > Capillaries
134
What are key aspects of the cardiac cycle?
Systole – contraction
| Diastole – relaxation
135
What is osmoregulation?
Balancing water and solute concentrations in body fluids
• Controlled movement of solutes between internal & external environment.
• Regulates solute concentrations and balances the gain and loss of water.
• Water content of cells is influenced by the fluid that surrounds the cells (interstitial).
136
How do you regulate the chemical composition of body fluids?
- -Physiological systems of animals operate in a fluid environment.
- -If water uptake is excessive, cells swell and burst.
- -If water loss is substantial, cells shrivel and die.
137
What is Hyperosmotic?
high solute concentration
138
What is Hypoosmotic?
Low solute concentration
139
Most marine invertebrates
are osmoconformers
140
What are some properties of Echinoderms?
Do not regulate ions
141
What are some properties of Aurelia?
Only regulates sulfate
142
What are some examples of amphibian osmoconformers?
Amphibians
e.g. crab-eating frog
Sharks and rays
143
What do osmoregulators expend?
Osmoregulators expend energy to control water uptake and loss in a hyper- or hypo-osmotic environment.
144
Outline Osmoregulation in marine vertebrates.
- -Excretion from gills.
- -Gain from food.
- -Osmotic loss through gills and body.
- -Gain from drinking seawater.
- -Excretion in concentrated urine from kidneys
145
Outline Osmoregulation in freshwater vertebrates.
- -Gain from food
- -Gain through gills.
- -Osmotic gain through gills and body.
- -Excretion of large amounts of dilute urine.
146
Outline Osmoregulation in marine mammals
* Are physiologically isolated from the water, unlike marine fish.
* Ingest salt via sea water and food and excrete concentrated urine to remove it to maintain their osmolarity.
* Have highly effective kidneys.
147
Osmoregulation is an
active process
148
What is active transport?
is required to regulate solute concentrations in body fluids.
149
What are the specialised cells that help in active transport?
Specialised epithelial cells move solutes
in controlled amounts and may face the
outside environment directly or can be
arranged in complex tubular networks
with an extensive surface area (kidneys).
EXAMPLE: salt gland in marine birds that
must drink sea water to survive.
150
What are some Osmoregulatory adaptations?
--Salt glands in marine birds remove excess NaCl from the blood.
--Secretory tubules are lined with single
layer of transport epithelial cells that
actively pump salt (NaCl) from blood
--Counter current exchange system
--Net gain of water
151
What are some other examples of salt glands?
1. Marine iguanas squirt salt secretions out through their nose.
2. Turtles excrete excess salt via tear ducts.
3. Crocodiles via modified salivary glands.
152
Why is Osmoregulation needed in terrestrial animals?
```
Threat of dehydration due to water loss.
Adaptations that reduce water loss are
key to survival on land, including:
--Physiological adaptations
--Behavioural adaptations
```
153
What is a Physiological adaptation?
e.g. waxy layer on exoskeleton of desert beetles, snail shells and keratinized skin.
154
What is a behavioural adaption?
e.g. nocturnality (fennec fox) and
| a reduced requirement to drink.
155
How is the water budget managed in terrestrial animals?
Water budgets managed by:
• drinking water
• eating moist foods
• using metabolic water
EXAMPLES:
Kangaroo rat
Some Australian desert frogs
156
What are some further terrestrial adaptations?
--Ostrich have two-chambered nasal passages that allow them to slow air passage and remove water vapor as they exhale.
--Desert spadefoot toad deals with dry periods by hiding for ¾ of the year and secreting a membrane around themselves.
157
Osmoregulation is the
balancing of water and solutes
158
Most marine invertebrates are
osmoconformers
159
Most marine vertebrates are
osmoregulators
160
Various adaptations to
excrete excess salt in marine vertebrates
161
Terrestrial animals have various adaptions to
conserve water
162
How is nitrogenous waste excreted?
* Waste products of metabolism are dissolved in water for excretion.
* Type and quantity of waste products affects water balance.
* Nitrogenous breakdown products of proteins and nucleic acids: ammonia, urea, uric acid.
163
Outline the properties of Ammonia (NH3).
Highly toxic and must be excreted quickly.
- -Ammonia excretion is most common in aquatic animals.
- -Ammonia is very soluble.
- --Ammonia is highly toxic because in part it interferes with oxidative phosphorylation, so it can only be tolerated in small quantities in the body. Ammonia must therefore be excreted very quickly and animals that do excrete nitrogenous waste need lots of water. Diffuses easily across membranes. Into surrounding water.
- --Is not suited for terrestrial animals as it can only be excreted in large volumes of dilute solutions. And terrestrial animals do not have access to the amount of water they would require.
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Ammonia converted to
urea
165
What are properties of urea?
Energetically expensive
Urea is less toxic than ammonia
Excreting urea requires less water
----The liver of mammals, most adult amphibians and some fish can therefore convert ammonia to urea. Urea can be transported safely in the circulatory system and stored in high concentrations prior to excretion via the kidneys. Amphibians can switch between excreting ammonia and urea, depending on their life stage.
166
What is uric acid?
- -Uric acid is relatively nontoxic
- -More energetically expensive to produce than urea
- -Insoluble in water
- -Less toxic for embryos in eggs
- -Uric acid is useful for animals with little access to water.
167
Why do animals have a simple excretory system?
• Different excretory systems in animals
where osmoregulation is coupled with
excretion of nitrogenous wastes.
• Lots of variation, but generally built on a
complex network of tubules that provide
large surface area for exchange of water
and solutes, including nitrogenous wastes.
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What is protonephridia of flatworms?
* Network of dead-end tubules connected to external openings.
* The smallest branches capped by a cellular unit called a flame bulb.
* Beating cilia draw in water and solutes from the interstitial fluid.
* Fluid filtrate excreted out of the body via the tubules.
169
What are the Malpighian tubules in insects?
* Tubules extend from dead end tips immersed in the haemolymph.
* Solutes and nitrogenous wastes are secreted into tubules and into the alimentary canal (water follows).
* Solutes and most of water reabsorbed in the rectum.
170
What are Antennal glands in crustaceans?
* ‘Green glands’ located in the head that open near the antennae.
* Consist of a sac, an excretory tubule and a bladder.
* Urine is formed by filtration and reabsorption.
* Some species reabsorb water and/or solutes.
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Lots of variation in
excretory systems
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Generally built on a complex network of ______ that provide ____ ____ ____ for exchange of water and solutes, including nitrogenous wastes.
tubules
| large surface area
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What are aspects of the complex excretory system?
* Filtration
* Absorption
* Secretion
* Excretion
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How is urine produced?
- -Filtration: from capillaries into interstitial fluid or haemolymph.
- -Reabsorption: key substances reabsorbed into blood.
- -Secretion: non-essential substances are secreted.
- -Excretion (micturition): the altered filtrate (urine) is excreted.
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How does reabsorption take place?
```
• Salt (NaCl)
• Water (H20)
• Urea (UT transporters in collecting duct;
upregulated by ADH)
• Concentration (osmotic) gradient in
the inner medulla
```
176
What is countercurrent multiplication?
--Loop of Henle
--Ascending limb
NaCl actively pumped out. Impermeable to water
--Descending limb
NaCl passively diffuses
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How is blood supplied to the medulla?
* Capillaries form hairpin loops that parallel the loops of Henle
* Looped shape prevents circulation of blood destroying concentration gradients of NaCl and Urea.
* Important role in removing water from medullary ISF.
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What is Antidiuretic hormone (ADH)?
- -Produced in hypothalamus
- -Released by pituitary gland
- -Directly affects water reabsorption in DCT and CD
- -Increases blood pressure
- -Decreases blood osmolarity, which in turn downregulates ADH production
179
How does ADH increase water reabsorption in the DCT and CD?
A couple of clues:
• Aquaporins
• Urea transporters
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What are some adaptations in excretory systems?
• Vampire bats stomach lining rapidly absorbs blood plasma, which is transported to the kidneys.
• The kidneys can rapidly produce either very dilute or very concentrated urine.
• Allows the bats to reduce their body weight rapidly (to fly) or digest large
amounts of protein while conserving water (when home).
• The length of the loop of Henle varies among animals; correlated with demand for conserving water.
• The kangaroo rat, and other desert mammals, have long loops of Henle
• Freshwater mammals (e.g. beaver) have low risk of dehydration and relatively short loops of Henle.
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What are some adaptations in birds?
• Many birds that live in dehydrating environments have juxtamedullary
neurons specialized for conserving water.
• Loops of Henle do NOT extend deep into the medulla.
• The main water conservation adaptation in birds is having uric acid as the nitrogen waste molecule, which can be excreted
as a paste (reduces water loss).
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Nitrogenous wastes can be excreted via
ammonia, urea or uric acid
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Various systems in animals, but all based on
tubules that provide a large surface area
| for exchange
184
What is excretion controlled by?
hormones
185
What are autotrophs?
Autotrophs are producers that can create complex organic compounds from simple inorganic substances such as co2.
186
Why might undernutrition occur?
Undernutrition can occur if an organism does not consume enough calories. And humans and other animals such as guinea-pigs and some birds and reptiles are incapable of synthesizing vitamin C and a lack of this can lead to scurvy etc. so herbivores live where soils are deficient in essential minerals will eat bones or visit salt licks to obtain these nutrients. Deer might eat their antlers when they shed and giraffes make bones to recover phosphorus and elephants often cover large distances to visit salt licks to obtain these minerals.
187
How do single celled organisms digest their food?
Single celled organisms digest their food intracellularly, e.g. paramecia ingest food by phagocytosis, so they engulf their food and fuse it with digestive lysozymes that contain hydrolytic enzymes.
188
But how do the majority of animals digest their food?
The majority of animals, however, process food extracellularly in specialized compartments that are continuous with the outside of the animal's body. This is to reduce the risk of the animal digesting their own body cells.
189
Where does extracellular digestion happen in many multicellular organisms?
Many multicellular organisms digest their food extracellularly within a digestive cavity and if there’s no specialization of this cavity it is called a gastrovascular cavity due to the fact that every cell is exposed to every stage of the food processing.
190
When does specialisation occur?
Specialisation occurs when the digestive tract or alimentary canal has a separate mouth and anus such that transport of food is unidirectional or one way. Using the Earthworm has an organism with a more complex digestive system, we can see that food is sucked in through the mouth, its passed through the crop, which is an organ for storage and then through the gizzard, which is an organ that essentially fragments the food, so grinding action of pebbles, breaks the food down and then into the intestine.
191
When does chemical digestion occur?
Chemical digestion occurs to liberate monosaccharides, AA and fatty acids from the food and these products pass through the epithelial lining of the gut into the blood and this process is known as absorption. Waste products are excreted through the anus and the advantage of these more complex body plans is that new meals can be ingested while older ones are still being absorbed.
192
What is the role of saliva in digestion?
Saliva plays other roles aside from enzymatic digestion. It contains a lysozyme, which is an antimicrobial compound which helps to neutralize acid produced by bacteria, and it lubricates the movement of food through the elementary canal or digestive tract. The epiglottis closes access to the trachea when swallowing food, enabling it to pass through the esophagus via peristalsis to the stomach.
193
What do herbivores have that is very prominent?
Herbivores seem to have very prominent molars/ premolars and this is to grind the tough plant materials and they tend to have very short incisors. So omnivores lie somewhere between, so we possess all four types of teeth but none of them are particularly dominant.
194
Food entering the esophagus is swallowed by the
contraction of the skeletal muscle.
195
Where is chyme moved?
So chyme is moved into the duodenum and after passing through the duodenum food then enters the jejunum and then the ileum and in these regions, absorption takes place through microvilli.
196
What happens when chyme arrives in the small intestine?
When chyme arrives in the small intestine or the duodenum, it triggers the release of secretin which stimulates the pancreas in preparation for digestion. And digestive juices from the pancreas including proteases such as trypsin and chymotrypsin, which break down proteins and gland cells of the small intestine are added to the duodenum. Pancreas can therefore be considered as an exocrine gland.
197
```
What is the function of the following-
1-Stomach
2-Liver
3-Gall Bladder
4-Pancreas
5-Colon
```
```
1-secretes gastric juice
2-Produces bile
3-Stores bile
4-Secretes proteases
5-Absorbs water and electrolytes
```
198
What is the anatomy of the small intestine specialised for?
Anatomy of the small intestine is specialized for digestion and uptake of nutrients. The huge surface area is created by the extensive folding of the epithelium and this results in small fingerlike projections called villi.
199
When can you see the microvilli and what can be observed?
Can only see the microvilli looking under electron microscope. The brush-border- references this epithelial surface at the apical surface of the epithelial cells. So the brush border enzymes which sit in the membranes, are important for completing the process of chemical digestion. So chemical digestion begins with the action of saliva.
200
How are proteins and carbohydrates transported?
Proteins and carbohydrates are transported across this brush border in their broken down forms of AA and polysaccharides respectively. Proteins are broken down into AA and these get transported across these epithelial cells across this border on the apical surface and the same happens with monosaccharides which are broken down versions of carbohydrates.
201
Absorption can require
ATP OR IT CAN be completely passive.
202
What are further important aspects of villi?
If we looked at the villi you will see columnar cells, so these are CBC cells, so the cells that are based in the crypt of the villi and they also called intestinal stem cells or ISC’s. These are capable of differentiating into four different types of cells.
203
What are the four cells that columnar cells can differentiate in to?
Paneth cells , enteroendocrine cells, goblet cells and absorptive epithelial cells( enterra sites). Differentiate from cells in the crypt of the villi in the small intestine and they have different functions
204
What are Paneth cells?
Paneth cells are really important for secreting antimicrobial peptides and this is important for maintaining bacterial populations.
205
What are enteroendocrine cells?
Enteroendocrine cells release digestive hormones.
206
What are Goblet cells?
Goblet cells secrete mucus, and the enterra sites absorb nutrients and pass them into the blood.
207
What is cecum in the large intestine?
Cecum- its a structure that is found at the connection between the small and large intestine and it may act as a safe house where beneficial bacteria can recolonize the intestine following illness. In herbivores the cecum plays a really important role in housing microorganisms that assist in the digestion of cellulose.
208
In mammals the urogenital products are separated from the
fecal material
209
Where does the fecal material enter in the large intestine?
In the large intestine, the fecal material enters the rectum and is expelled through the anus. In humans approx 7L of water is secreted into the elemental canal for digestion and approximately 90% of this water is recovered in the small intestine and colon.
210
What is cellulose?
Cellulose is a major source of glucose that is used in cellular respiration for most herbivores. So although herbivores do gain much of their energy from cellulose of plant cell walls, they actually lack the enzymes required to digest it.
211
Why may many organisms in captivity do less well?
Many organisms in captivity may do less well in the wild due to lack of fermentation microflora.
212
What are the three phases of respiration?
1st phase is external respiration also known as ventilation, where the medium, so the air or water thats carrying the oxygen crosses the membranes for gas exchange. 2nd phase is internal respiration where the oxygen and carbon dioxide are transported in the blood. In 3rd phase, cellular respiration, oxygen is used by the cells and cellular respiration uses oxygen to release energy from organic molecules like glucose as ATP.
213
Where does oxygen enter the organism?
Oxygen enters the organism through a respiratory surface thats optimized for exchange, usually an increased surface area. This oxygen moves through a circulatory system. Then oxygen then diffuses into the cells. A cellular respiration then occurs, so oxygen thats released travels back via the circulatory system to the respiratory exchange surface to be exchanged back to the environment.
214
What is diffusion driven by?
Diffusion is driven by the concentration gradients of oxygen and carbon dioxide across the membranes of the respiratory surface. So for dissolved gases, concentration is usually expressed as pressure and gases always diffuse from a region of higher pressure to a region of lower pressure.
215
What is partial pressure?
the force exerted by a gas. The sum of the partial pressures of all the gases in a mixture equals the total pressure. Partial pressure is extremely important in predicting the movement of gases. Recall that gases tend to equalize their pressure in two regions that are connected.
216
What does ficks law suggest?
Ficks law of diffusion suggests that the rate of diffusion will increase as the SA for gas exchange increases and as the concentration pressure gradient of dissolved gases increases. So if A and or the difference in pressure increase, then so will R. So the rate of diffusion will get faster when you've got a bigger SA or a bigger pressure gradient. Rate of diffusion is inversely proportional to distance, so this is why distance here is at the bottom of the equation. K is the diffusion coefficient, is a constant value that represents the size of the molecule. The membrane permeability and temperature.
217
How do bacterial protists obtain oxygen?
So where bacterial protists are small enough to obtain oxygen by diffusion directly from their environment, respiratory adaptations need to exist in other organisms to assist in this uptake of oxygen.
218
What do most invertebrates lack?
Most invertebrates lack specialized respiratory organs, but they are able to use beating cilia to replenish oxygen supply in the water over their respiratory surfaces.
219
What do most multicellular organisms require?
Most multicellular organisms, however, do require structural adaptations to obtain enough oxygen for cellular respiration. The rate of diffusion R can be optimised by changes that increase the SA for gas exchange or increase the pressure gradient and or decrease the distance of diffusion.
220
What are Gills?
If a respiratory surface is turned out or evaginated, its called a gill. Gills can remain turned out like in the salamander, or can be secondarily enclosed as in fish. If the general body surface is turned in or invigilated then the respiratory organ is called a lung.
221
What are the properties of water entering the fish?
Water entering the fish is 100% saturated since deoxygenated blood is flowing in the opposite direction to the water, this generates a concentration or pressure difference. Since oxygen is a dissolved gas. Dissolved gases always diffuse from a region of high to low partial pressure. In this case oxygen will move from the water into the blood.
222
Where are gills located in bony fish?
Gills of bony fish are located between the oral cavity, the buchel cavity and the operculum or the operculum cavity. And these two sets of cavities function as pumps that expand alternately to move water into the mouth through the gills and out of the fish through the operculum. Some bony fish that swim continuously, such as tuna and shark have practically immobile opercula and these fish swim with their mouths partially opened to constantly force water over the gills in what is known as ram ventilation.
223
What is jet propulsion?
Jet propulsion is a form of movement in squid and octopus. With octopus it involves water being taken into the mantle cavity and being drawn across the gills and then being ejected through the syphon. This creates movement and simultaneously ventilates the gills to increase oxygen availability at a time when it is most needed, such as when it needs to escape rapidly.
224
How do amphibians force air into their lungs?
Amphibians force air into their lungs by filling their oral cavity with air, closing their mouths, then elevating the floor of their oral cavities. When male frogs puff themselves up in an aggressive or courtship display they disrupt their breathing cycle, taking in air several times without allowing any release.
225
Where is partial energy higher?
The maximum partial pressure of oxygen in the lungs is higher in birds than in mammals and avian respiration is much more efficient.
226
How does inhaled air travel in mammals?
inhaled air passes through the trachea, Bronchi and Bronchioles to the alveoli where the gas exchange occurs. Surfactants coat the surface of the alveoli and lowers surface tension in order to allow the diffusion of gas across the respiratory surface.
227
What happens at rest?
At rest the atmospheric and intrapulmonary pressures are equal, so theres no air flow.
228
What happens in inspiration?
During inspiration, the diaphragm contracts or flattens and this expands the thoracic cavity, reducing the intrapulmonary pressure by about 3mm. Air flows into the lungs, since the atmospheric pressure is now higher than the intrapulmonary pressure. Exhalation is a passive process, not an active one.
229
What is interstitial fluid?
Interstitial fluid is the fluid that bathes and surrounds the tissue cells in multicellular animals. It does not play a role in gas exchange, but it is important for transport.
230
What happens to the gills when there is a pressure drop?
Due to the pressure drop slows the circulation from the gills to the rest of the body and is therefore a limiting factor of oxygen to the tissues. Single circuits like these work fine in fish because when they swim, the contraction and relaxation of their muscles helps to accelerate this relatively sluggish pace of circulation of blood in the capillary bed.
231
What are the 5 variables that influence blood flow and blood pressure?
These are cardiac output, which is essentially the flow of blood out of the ventricles in liters per minute. Compliance, which is the ability of a blood vessel to expand to accommodate the blood flow, blood volume, viscosity of the blood the thickness of the blood, and the length and diameter of the blood vessels. Velocity is highest in the arteries and will be lowest in the capillary’s, this is because the velocity of blood flow varies with the diameter of the blood vessels. So velocity will be higher in the veins that it is in the capillaries due to the lower internal resistance in the veins because they have a bigger diameter.
232
What is kept separate in a double circulatory system?
the pulmonary and systemic circulations are kept separate.
233
What needs to be maintained in a narrow range?
As with many physiological parameters, the relative concentrations of water and solutes must be maintained within a narrow range
234
What does Osmoregulation regulate?
Osmoregulation regulates solute concentrations and balances the gain and loss of water.
235
How is water and interstitial fluid regulated?
Water enters and leaves cells by osmosis following the movement of solutes. Water content of cells is influenced by the fluid that surrounds them.
The interstitial fluid or hemolymph of an organism that is regulated not the cells specifically.
236
```
Define these:
1-Osmosis
2-Osmolarity
3-Isoosmotic
4-Osmolality
```
1-movement of water across a selectively permeable membrane
2-is a solid concentration of a solution which determines the movement of water across a selectively permeable membrane.
3- this means they have the same osmolarities as each ither, so the net movement of water is equal in both directions.
If two solutions differ in osmolarity, the net flow of water is from the hypoosmotic to the hyperosmotic solution.
4-refers to the number of particles of solute per kilogram of solvent.
237
What are osmoconformers?
are isosmotic with their surroundings, which means they match the osmolarity of their body fluids to that of their environment, either actively or passively. generally , constant composition and concentrations of solutes in body fluids still differ from seawater and is regulated. Some echinoderms do not regulate ions. Most animals live in environments where the solute concentrations are unsuitable for internal physiology so they must regulate their internal fluids.
238
Why are most marine vertebrates osmoregulators?
Most marine vertebrates are osmoregulators- because the ocean is a strongly dehydrating environment for them
239
Marine or saltwater vertebrates are
are hypoosmotic to use seawater and constantly lose water to their surroundings. They balance this water loss by drinking large amounts of seawater and excreting excess salt by the kidneys and gills. They pump out chloride and sodium follows passively along the electrical gradient.
240
What is different in fresh water vertebrates?
Fresh water vertebrates have the opposite osmoregulatory problems, they constantly take up water by osmosis, from their hypoosmotic environment because they are hyperosmotic. The water balance is maintained by excreting large amounts of very dilute urine and drinking almost no water. So its lost by diffusion or replaced in foods and by uptake across the gills. They pump in chloride and sodium follows passively along an electrical gradient.
241
What do epithelial cells pump?
Epithelial cells pump salt from the blood into the tubule lumen. This is a countercurrent exchange because blood is flowing in the opposite direction to flow within the tubules, so this enhances salt transfer in a similar way to gas exchange in the gills of fish.
242
How can water be lost?
Water can be lost through a number of routes, including urine, feces, skin and from moist surfaces in gas exchange organs. Adaptations that reduce water loss are key to survival on land and they include physiological and behavioural adaptations.
243
In many animals what is osmoregulation coupled with?
coupled with excretion of the waste products of metabolism. These waste substances are dissolved in water. When proteins and nucleic acids are broken apart for energy or converted to carbohydrates or fats, enzymes remove nitrogen in the form of ammonia.
244
In mammals what is each kidney supplied by?
In mammals each kidney is supplied with blood by a renal artery and its drained by a renal vein. During circulation, 25% of the blood is directed through the kidneys and urine exits each kidney through a duct, called a ureter. Both of the ureter is drained into a common urinary bladder and urine is expelled through a urethra.
245
Outline the aspects of the kidney.
Kidneys function in both osmoregulation and excretion, and there are two distinct layers in the kidney. The renal cortex- outer layer of the kidney and the renal medulla- inner layer of kidney. The nephron is the functional unit of the kidney, and it consists of a capillary bed called the glomerulus- where filtration occurs. Renal tubules, where the fluid can flow through the nephron and the collecting duct. So the collecting ducts collect the urine and allow it to exit the kidney.
246
How are mammalian nephrons adapted?
Mammalian nephrons are adapted for minimising urinary water loss and for the excretion of nitrogenous waste. There are 2 types of nephrons- cortical- which have very short loops of henle and they are confined to the renal cortex and we have these juxtamedullary nephrons which have very long loops of henle that project down into the renal medulla.
247
How do mammals filter their blood?
Mammals filter their blood through a specialized system of capillaries that enable the non selective passage of small molecules across the epithelium. This is driven by circulatory pressure and water solutes and nitrogenous waste move from the capillary’s into the interstitial fluid. The resulting filtrate contains salts glucose, AA, vitamins, nitrogenous wastes, and other small molecules.
248
What is GFR?
THIS IS the rate at which fluid is generated.
249
What is clearance?
Clearance- refers to the amount of fluid cleared completely of a certain substance, which enables clinicians to estimate the GFR.
250
What is selective reabsorption?
Selective reabsorption- water and other useful solutes are reabsorbed by moving into the medulla. Down the concentration gradient thats maintained by the loop of henle creating a concentrated urine for excretion via the collecting duct. The diffusion of water and urea is passive, sodium chloride however can cross the membrane by different mechanisms depending on which transport mechanisms are present in the epithelial cells of the tubule. Sodium chloride can be actively transported out of the ascending loop of Henle. Whereas diffusion of sodium chloride can be passive in other regions of the nephron, is important for the countercurrent multiplication system.
251
How are concentration differences established?
Concentration differences are established by the permeability properties of membranes and they are strongly influenced by the transport mechanisms that exist within epithelial cells. The features of the epithelial cells that line the tubules of the nephron differ depending on where they are located. E.g. the descending limb contains very simple squamous epithelium so this section of the nephron is highly permeable to water. The thick ascending limb of the Henle, you can see the epithelial cells are quite different in structure and they contain these tight junctions between cells, that really limit the movement of water from the medulla into the lumen of the tubule. So this region of the nephron is very impermeable to water .
252
What is the single effect phenomenon?
The single effect phenomenon has been documented in the outer segments of the medulla where the fixed segments of the ascending limb of the loop of Henle occurs. If there were no membrane transport mechanisms in the membranes of epithelial cells of the tubules, then the fluid that's entering the loop of Henle would be isosmotic. So the same osmolarity as the fluid that is leaving the loop of Henle via the distal tubule. And this tubular fluid would also be isosmotic with the fluid in the interstitial fluid in the medulla. Sodium and chloride ions would be very equally distributed. This isn't actually the case as the cells of the epithelium in the ascending limb there are transport mechanisms that actively transport sodium chloride out of the tubule. The movement of this sodium chloride acts to produce a concentration gradient. So there's going to be less solute inside the tubule with respect to outside. There is passive diffusion of some sort of another allowing sodium and chloride to enter the descending limb, and water is freely permeable so it will leave in response to that. So as sodium chloride is being pumped out of the ascending thick limb of the Henle, at the same time you are getting equaliberation across the descending limb.
253
What does the countercurrent system of the loop of Henle essentially do?
essentially multiples this single effect difference. It turns this concentration difference into a much larger difference in concentration from one end to the other of the loop of Henle. So and end to end difference of 600 millosmols is not unusual and many mammals can create differences that are much greater than this. Differences in osmolarity are paralleled by differences in concentration. If a concentration of something increases, so does the osmolarity. So if we take sodium chloride and put it into a solution it will dissociate into sodium and chloride, therefore the osmolarity is twice the concentration difference. CC- creates this concentration gradient from one end of the loop of Henle to the other and this allows for the concentration of urine.
254
What is the vasa recta?
blood supply of the medulla.
255
What is ADH?
plays an important role in coordinating the autoregulatory function of the kidney and it does this by altering the permeability properties of the epithelial cells in the nephrons to increase the reabsorption of water. There's a negative feedback loop which controls the activity of osmoreceptor cells in the hypothalamus, which acts to monitor the osmolarity of blood and regulate the release of ADH. levels of ADH in the blood affect the level of reabsorption of water in the kidney, higher the ADH levels are, the more reabsorption of water you have and the lower the ADH levels are, you get reduced reabsorption of water.
256
What is RAAS?
Renin is released from the juxtaglomerular apparatus and this happens in response to the detection of low blood flow. When your blood pressure goes down, renin is released. Renin converts angiotensinogen into angiotensin II and angiotensin II causes the constriction of blood vessels to help increase the blood pressure and it also causes aldosterone to be released from the adrenal cortex. So aldosterone is a hormone and aldosterone acts to increase the reabsorption of sodium and also chloride and water. This in turn increases the blood volume and there’s a negative feedback loop here to reduce the amount of renin that's released. This system essentially allows blood pressure to be kept within the normal ranges.
