biology: osmoregulation- water regulation in vertebrates
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Lesson 1: Biology Unit 2, Water Regulation in VertebratesThursday, 9th August, 2012.
Class duration: 70 minsClass setting: Science laboratoryMaterials: None
Learning intention:To understand the physiological the adaptions in mammals that assist them to maintain water balance.
Time (mins)
Teacher activity Student activity
5 Introduce myself, mark the roll.
20 Introduce topic, and teach the process of water regulation in mammals.
Vasopressin
Listen, answer questions, copy definitions and diagrams from the board.
10-15 mins?
Tell students to get into groups of 2-3, and teach each ot her.
Drawing/teaching
15 Revision mind-map cut and paste activity (work in pairs)
Cutting and pasting steps into the mindmap.
10 Check answers as a class (page 329) Checking their answers.
Lesson 1: Biology Unit 2, Water Regulation in VertebratesThursday, 9th August, 2012.
Class duration: 70 mins Class setting: Science laboratory Materials: Projector
Learning intention:To understand the physiological the adaptions in mammals that assist them to maintain water balance.
Teacher activity
Introduce topic:Physiological Adaptions for Maintaining Water Balance in Vertebrates
Break down the meaning of the topic:Physiological: In relation to the scientific study of the processes and functions of a living organism.
Adaptions: Any genetically controlled features that may assist survival and reproduction of organisms in their specific environments.
Vertebrates: Animals distinguished by the possession of a backbone (including mammals, marsupials, birds, reptiles, amphibians, and fish).
The physiological adaptions for maintaining water balance in MAMMALS
1. Does anybody know which organ controls water balance of the body for all vertebrates?
Ans: Kidneys
2. What is the function of the kidneys?
Ans: To eliminate nitrogenous wastes from the body while ensuring water balance.
3. Why is it important to maintain water balance (osmoregulation)?
Ans: To stabilize the internal environment of the body (homeostasis). That’s why kidneys are important. We would only survive for a few days without them.
Osmoregulation is associated with the maintenance of blood pressure.
Increase water (in body) = increase blood pressure
“Osmoregulation is associated with the maintenance of blood pressure.” … HOW?
Two significant compounds (hormones) are involved:- Antidiuretic hormone (ADH) a.k.a. Vasopressin- Renin
Vasopressin (Antidiuretic hormone, ADH) is a hormone found in most mammals (including humans).
*Show diagram of the brain*Produced in the hypothalamus, and released by the pituitary gland.
*Draw diagram on the board. Students copy this.*
- Vasopressin is produced by neurosecretory cells in the hypothalamus of the brain.- There are cells in the hypothalamus called osmoreceptors.- Neurosecretory cells are activated when osmoreceptors in the hypothalamus detect an increase in
blood solutes…
1. When there is a rise in blood solutes (increase of osmolarity), is there an increase or decrease of water in the blood? Ans: there is a decrease in water concentration in the blood.
2. What could cause the decrease of water concentration in the blood? Ans: insufficient intake of water, excessive sweating, diarrhoea.
- Neurosecretory cells release vasopressin. Vasopressin flows through the axons of the neurosecretory cells to the posterior pituitary gland, where it is released into the bloodstream (or stored).
- Vasopressin is transported through the bloodstream to the kidneys, where it increases the permeability of distal tubules and collecting ducts to water.
What does this mean? “increased permeability to water”?What does “permeable” mean? Ans. Allows fluids to go through (i.e. more water).
So the distal tubules and collecting ducts (in the kidneys) become more permeable to water, allows water to pass through. So there is an increase of water being reabsorbed by these areas…
With the reabsorption of water from the kidneys, our bodies would now contain sufficient water. Then what would happen to the concentration of blood solutes (increase or decrease)?Ans. Fall/decrease… blood becomes more diluted, and concentration of blood solute decreases
If there is a decrease in the concentration of blood solutes (osmolarity), what would happen to the levels of vasopressin in our blood?Ans: Decrease, because Vasopressin is released when there is a decrease in blood solutes.
THIS IS CALLED “NEGATIVE FEEDBACK”.
How do you feel when you don’t have enough water in your body? Ans. THIRSTY!!!Why? Because osmoreceptors generate a sensation of thirst when they detect a rise in blood solutes! Increased drinking also acts as a feedback mechanism leading to reduced secretion of Vasopressin.
If water is being reabsorbed from the kidneys and back into our bloodstream, what would happen to our urine?Ans. Become more concentrated, less water/less urine, yellow in colour.
Concentration of solutes in
blood (osmolarity)
increases
Detected by osmoreceptors
in the hypothalamus
Increased production of vasopressin in
neurosecretory cells and flow to posterior
pituitary
Increased release of vasopressin from the
posterior pituitary into the bloodstream
Increased permeability of distal nephron
tubules to water
Increased water
reabsorption from nephron
tubules
Blood pressure increased (vessels
constricted) and
Decreased production of vasopressin in
neuroscretory cells
Negative Feedback
mechanism
Creates sensation of
thirst
Increased intake of water
Increased production of vasopressin in
neurosecretory cells and flow to posterior
pituitary
Increased release of vasopressin from the
posterior pituitary into the bloodstream
Decreased production of vasopressin in
neuroscretory cells
Increased production of vasopressin in
neurosecretory cells and flow to posterior
pituitary
Increased release of vasopressin from the
posterior pituitary into the bloodstream
Decreased production of vasopressin in
neuroscretory cells
Increased production of vasopressin in
neurosecretory cells and flow to posterior
pituitary
Increased release of vasopressin from the
posterior pituitary into the bloodstream
Decreased production of vasopressin in
neuroscretory cells
Concentration of solutes in
blood (osmolarity)
increases
Detected by osmoreceptors
in the hypothalamus
Increased water
reabsorption from nephron
tubules
Blood pressure increased (vessels
constricted) and
Negative Feedback
mechanism
Creates sensation of
thirst
Increased intake of water
Increased permeability of distal nephron
tubules to water
Concentration of solutes in
blood (osmolarity)
increases
Detected by osmoreceptors
in the hypothalamus
Increased water
reabsorption from nephron
tubules
Blood pressure increased (vessels
constricted) and
Negative Feedback
mechanism
Creates sensation of
thirst
Increased intake of water
Increased permeability of distal nephron
tubules to water
Concentration of solutes in
blood (osmolarity)
increases
Detected by osmoreceptors
in the hypothalamus
Increased water
reabsorption from nephron
tubules
Blood pressure increased (vessels
constricted) and
Negative Feedback
mechanism
Creates sensation of
thirst
Increased intake of water
Increased permeability of distal nephron
tubules to water