The role of the skin in thermoregulation of the body
Abstract of a biology lesson using the digital laboratory "Archimedes" with a multimedia application (biology grade 8)
Chernushka 2012
The purpose of the lesson :
to form students' knowledge about the functions of the skin associated with the regulation of the constancy of the internal environment of the body, using for this knowledge of biology, physics.
to consolidate knowledge about the structure of the skin, with its basic properties; form the need to take care of your health;
to draw the child's attention to himself, to his own structure through experience, to come to scientific knowledge, to lead to an understanding of himself as a person.
Lesson Objectives:
educational:
to concretize knowledge about the structure of the skin;
to form knowledge about the skin as an organ of heat transfer;
To reveal the conditions for maintaining a constant body temperature when the temperature rises and falls.
developing:
develop the ability to draw conclusions from the results of practical work;
develop the ability to establish the relationship between physical work and thermoregulation of the body;
develop the ability to analyze and compare information, generalize and establish causal relationships.
educational:
continue hygiene education students, respect for their health,
develop communication skills.
Equipment:
projector
presentation
Nova 5000 laptop
temperature sensors
humidity sensor
thick thread
plastic bag
rubber ring
During the classes
Organizing time
updating basic knowledge: Very often letters from readers are published in youth newspapers and magazines, listen to an excerpt from such a "letter". Are there biological errors and inaccuracies in it? What are they?
The long-awaited time has finally begun - the holidays! My friend and I woke up at noon and immediately ran to the beach. Rather into the water! Having bathed enough to the point of exhaustion, we stretched out on the sand and sunbathed for three hours. I taught in biology lesson that ultraviolet rays increase the stratum corneum of the skin, pigment gradually accumulates in its cells, which gives it Brown color- Tan. This is beauty and health.
Learning new material:
take a look at the slide and determine which two groups the animals depicted here can be divided into. What is the basis of the division into groups? ( slide 1)
Which of these groups does the person belong to?
What property of an organism is called warm-bloodedness? (Warm-bloodedness is the property of the body to maintain body temperature at a certain level.) (slide 2)
“And now guys, I want to tell you a legend (nice music sounds). ( slide 3)
Nearly five centuries ago, in last days 1496, in the luxurious castle of the Duke of Milan, Moreau was preparing for new year holiday... The Duke was going to show his guests such wonderful performances such as the world had never seen. Still would! The celebration was organized by the great artist and unrivaled mechanic Leonardo da Vinci. He planned to celebrate the golden age of the world, which came after many years of the Iron Age of devastating wars.
To depict the Iron Age, blacksmiths under the supervision of Leonardo da Vinci made a huge figure of a reclining knight, chained in armor. And the golden age was supposed to depict a naked boy, covered from head to toe with gold paint. This was the son of a poor baker. Father for money provided him for the amusement of the duke.
In the midst of the festive fun, the defeated knight was brought into the hall. From his womb came a "golden boy" with wings and a laurel branch in his hand. Frightened, he looked at those around him, uttering a memorized greeting to the duke. The holiday could not be completed, because the duke's wife suddenly fell ill. The guests departed. The lights went out. They forgot about the boy, of course ... He was left alone, in a huge, cold, semi-dark hall. Only the next day, Leonardo da Vinci saw him in a dark corner. The child trembled and cried pitifully. Leonardo wrapped him in a cloak, took him home and tended him for three days, trying to save him. But on the fourth day the boy died. Centuries have passed. The story of the "golden boy" associated with the name of the great artist has not been forgotten. And the reason for his death remained unclear for a long time and caused different interpretations.
Can you answer me and name the main reasons for the death of the boy? (Students formulate an answer and say that this boy died from hypothermia. Thermoregulation was impaired.)
Today we will talk about thermoregulation. Write down the topic of the lesson "Thermoregulation of the body" ( slide 4)
From the point of view of physics, a person is just a physical body and it would seem that processes should occur with him, the same as with any physical bodies. The body temperature of a person is 36.6 0 C, and in the classroom - 24 0 C. A person must give part internal energy ambient air until the temperature is the same. But is it really so?
What new should we learn on this topic? Let's formulate the goals of our lesson (students formulate goals, and the teacher specifies them) (slide 5) Explain why our body temperature remains constant. To answer this question, we must remember the structure of the skin. (slide 6)
Do you know how much heat is generated in the human body in one hour? Just enough to boil 1 liter of ice water. And if the body instead of the skin were covered with a heat-impermeable case, then in an hour the body temperature would rise by about 1.5 degrees, and in forty hours it would reach the boiling point of water. During hard physical work, the generation of heat increases several times. (slide 7)
And yet, the body temperature does not change. When they talk about body temperature, they mean the temperature of the internal regions of the body, i.e. tissues lying deeper than 2.5 cm under the skin surface. In humans, the surface temperature of the skin is not the same in different areas. The lowest temperature is in the skin of the hands and feet (28.5 0 C), and the highest is in the neck. Inside the liver, where oxidative processes take place, the temperature reaches 39 0 C. (slide 8)
In a healthy person, it is usually 36.5-37 degrees. Its rise above 43 0 and falling below 25 0 C are fatal. This constancy of body temperature is maintained almost exclusively by regulating the transfer of heat through the skin. After all, it is in direct contact with the external environment, therefore, it registers all temperature changes.
The set of physiological reactions of the body that ensure the constancy of body temperature is called thermoregulation(slide 9)
When does the body produce heat? (food intake, muscle work) (slide 10)
What are the sources of heat in the human body? (Nutrients (proteins, fats, carbohydrates), which, when broken down (hydrolysis with the participation of enzymes - biological catalysts), release heat (exothermic reactions occur), in addition, there are active tissues - liver, muscles.)
For the body to give off heat to the environment, the heat it generates must "have access" to the external environment. Heat from deep within the body (core) is transported by blood to the skin, from where it can be transferred to the environment due to one of the following mechanisms: ( slide 11)
Loss of heat through the skin by radiation
By convection
By thermal conduction.
They all depend on the amount of blood flowing through the skin.
But how it depends, we will check by holding laboratory work"Violation of blood circulation when applying a tourniquet." We will use a digital laboratory to carry it out. You have everything on your tables necessary materials for its implementation and instructions (appendix 1)
Why does the temperature of the insulated fingers get lowered?
Why, after the restoration of normal blood supply, the temperature of the fingers increases slightly compared to the initial one?
Human skin is abundantly supplied with blood vessels. Many capillaries form loops and anastomoses, allowing the amount of blood flowing through the cutaneous capillaries to be altered. With the narrowing of these vessels, heat transfer decreases. When they expand, the generation of heat increases. In addition, a large amount of blood flows through the sweat glands. ( slide 12)
Now try to explain the experiment of Dr. C. Blagden, carried out in England more than 200 years ago. Together with a few friends and a dog, I spent 45 minutes in a dry chamber at a temperature of +126 without any health consequences. At the same time, a piece of meat taken into the chamber turned out to be boiled, and cold water, which was prevented from evaporating by a layer of oil, was heated to a boil. ( slide 13)
During evaporation, heat is lost from the surface of the body during the conversion of water to water vapor. Evaporation of 1 g of water consumes 2.45 kJ of heat. Heat transfer by evaporation of sweat occurs continuously in the form of perspiration invisible to us.
Sweat is a watery liquid containing 0.1-0.4% sodium chloride, sodium lactate and urea. It is formed from tissue fluid. ( slide 14)
In humans, sweating begins when the temperature rises above 36.7 0 C. Under normal conditions, 900 ml are released per day, but with very strong heat and an adequate supply of water and salts, this value can reach 12 liters.
Now you will carry out one more laboratory work "Excretory and thermoregulatory function of the skin" after which you will answer the following questions:
Why does the temperature in the bag rise during the experiment?
Why does the moisture in the bag rise?
Why in the second experiment the humidity increased faster and reached a higher value than in the first experiment?
Why are summer clothes made from natural rather than synthetic fabrics? ( slide 15)
Now let's try to formulate the main conclusions of this lesson.
Skin is the main organ of thermoregulation
Depending on the nature of the implementation of thermoregulatory mechanisms, warm-blooded and cold-blooded animals are distinguished.
Thermoregulation is the process of balancing heat generation and heat transfer in accordance with the conditions of the external and internal environment.
Violation of thermoregulation processes can lead to overheating or hypothermia of the body. ( slide 16)
The formation and release of heat is regulated reflexively and humorally. There is a thermoregulatory center located in the hypothalamus (diencephalon). It is believed that in its front part there are centers that regulate heat transfer, and in the region of the posterior hypothalamus there are centers that control the processes of production and preservation of heat. ( slide 17)
Temperature environment and its fluctuations act on the skin's thermoreceptors. It is estimated that there are 12 cold receptors per 1 cm 2, 1-2 heat receptors. And the entire skin surface of the human body contains 250 thousand cold receptors and only 30 thousand heat receptors.
Consolidation of the studied material: ... (slide 18 - 21)
Solve biological problems:
The effect of alcohol on the body causes vasodilation. Which person, sober or drunk, will freeze faster in the cold?
Feet in tight shoes freeze in winter, and get very hot in summer. Explain why?
Why is it harmful to tighten the belt tightly and wear tight shoes?
A person in a temperate climate wears clothing appropriate for the weather. However, the inhabitants of Central Asia wear warm wadded robes in the hottest weather. Give an explanation for this phenomenon.
Homework ... (slide 22)
§42
Make a cinquain on the theme "Leather"
This video tutorial is devoted to the topic "The role of the skin in heat regulation". The human body produces heat all the time. In the lesson, the teacher will tell you what is the role of the skin in heat regulation. You will consider a lot interesting facts related to the human body. For example, you will learn what keeps our body temperature constant even in the hottest weather.
BIOLOGY 8 CLASS
Topic: Excretory system. Leather
Lesson 54. The role of skin in heat regulation
Shevyakhova Yulia Olegovna
biology teacher of the highest category, laureate of the PNPO prize, TsO No. 1445
Three quarters of the heat generated by the body is lost through the skin.
A person emits heat all the time. A person generates so much heat per day that it is enough to bring 33 liters of ice water to a boil
Like all warm-blooded organisms, humans have the same amount of heat in the body both in winter and in summer. External conditions change, but the body temperature remains constant. This means that at different times there is a different heat transfer. Heat transfer depends on air temperature, humidity and movement.
The constancy of the temperature of our body is ensured by the regulation of heat transfer.
Thermoregulation is the body's ability to maintain a constant body temperature in a changing environment.
Thermoregulation ensures a constant temperature between 36.5 and 36.9 degrees, which is very important for the functioning of proteins and other organic substances.
A person can tolerate only slight fluctuations in temperature inside his body. Its rise to 43 and drop to 25 degrees is usually fatal.
Thermoregulation is carried out due to two important processes: a change in the lumen of blood vessels and sweating.
At high ambient temperatures, the blood vessels expand, therefore more blood passes through them, the skin heats up, and the heat transfer to the environment increases.
With a cold snap, skin vessels reflexively narrow, blood flow in the skin decreases, and heat loss decreases.
The change in blood flow in the skin leads to a change in its color. With strong emotions, such as fright, the small vessels of the skin overlap and the skin turns pale. When a person is angry, the flow of the skin to the blood increases and the person blushes.
In extreme heat, when the body temperature is lower than the ambient temperature, the expansion of blood vessels can no longer enhance the transfer of heat. In this case, the risk of overheating is eliminated by perspiration. As it evaporates, sweat absorbs large amounts of heat from the skin's surface. This is why a person's body temperature does not rise even in the hottest weather.
Of course, all the processes that we talked about occur under the influence of the nervous system.
But sometimes our body temperature rises. This happens when we get sick. The fact is that when an infection penetrates our body, along with protective substances, pyrogenic (heat-generating) substances are also formed. The reaction of the nervous system to these substances leads to an increase in temperature and is an indicator of a favorable course of the disease, this is a reflection of the body's active struggle against infection, its natural reaction.
An increase in temperature accelerates chemical processes, increases metabolism in tissues, increases the activity of leukocytes, liver, pituitary gland. This is how the body's defenses are mobilized.
But nevertheless, doctors advise to reduce a very high temperature by using antipyretics. The point is that persistent heat puts a lot of stress on the heart. The patient's pulse quickens, the whole body weakens, the work of some enzymes may deteriorate. The patient usually cannot tolerate such a condition for a long time.
When overheating in the sun in calm weather, especially in an atmosphere saturated with water vapor, during physical work in stuffy, poorly ventilated rooms or in clothing that is poorly permeable to air, the body's return of heat is difficult.
An imbalance between heat generation and heat dissipation can result in heatstroke. Headache, shortness of breath, dizziness, tinnitus, weakness appear, pulse quickens, "flies" flash before the eyes. The person is paler and may faint.
The victim must be moved to a cool place, undressed or unbuttoned; put soaked on your head cold water towel or ice, raise your legs with a roller from clothes. If the patient has not lost consciousness, they give him a drink of cool water.
To reduce the body temperature of the victim, a wet sheet is wrapped and fanned to create air movement and increase evaporation.
And, of course, you need to call an ambulance right away!
Lesson topic: The role of skin in thermoregulation.
Target: to form the concept of "thermoregulation".
Tasks: 1. To reveal the role of the skin in the regulation of body temperature.
2. Learn the rules of first aid in violation of thermoregulation.
3. Be able to use personal experience when establishing the dependence of heat transfer on environmental conditions.
4. Develop the skills of independent work with the text of the textbook to obtain the necessary information.
Lesson plan: 1. Organizational moment.
2. Statement of a problem situation.
3. "Opening" the topic of the lesson, setting goals and objectives of the lesson.
4. Experiment.
5. Test poll.
6. Learning new material.
7. Anchoring.
During the classes.
Slide number 1. Questions: 1) By what principle are these animals divided into two groups?
2) Which of these groups does the person belong to?
Slide number 2. Now imagine that we are in 15th century Italy. In the luxurious castle of the Duke of Moreau of Milan, a magnificent celebration is taking place, the idea of which was invented by the great Leonardo da Vinci. The "Golden Age" of the Renaissance personifies little boy whose body was covered in gold paint. After the holiday, everyone forgot about him. And only the next day, Leonardo da Vinci found the baby in a dark corner of the cold room. He was crying and shivering from the cold. The boy died a few days later.
Question: What is the reason for the death of the "golden boy"?
You can write down the versions that the guys are proposing on the board.
Teacher: You see that so far you do not have enough knowledge to give the correct answer to the question.
Together with the students, the topic of the lesson, goal, tasks are formulated.
Slide number 3.
Experiment. The children are invited to measure the temperature of different parts of the body (palm, hand, face, armpit), the data is written to the board. While 3-4 people are performing the experiment, the rest are performing a test on the topic "The structure and function of the skin."
Analysis of the results of the experiment, the formulation of conclusions. 1) Different parts of the body have different temperatures... 2) 36.6 ° C - the average temperature of the human body. 3) 25 ° C> fatal> 43 ° C.
Learning new material.
In the human body, in 1 hour, as much heat is generated as is needed to boil 1 liter of ice water. During hard physical work, the generation of heat increases several times. And yet, the body temperature does not change. Why? (Discussion of the problem by students).
The constancy of body temperature is maintained by regulating the release of heat from the body. And this role belongs to our skin, since this organ is in direct contact with the external environment and, therefore, registers the change in its temperature.
Slide number 4. Working with the scheme.
A message about how the body releases heat can be given in advance, or strong students can be invited to work with the article while others are doing the test and experiment. The death of the "golden boy" is discussed again, the reason is established. More than 200 years ago, the English doctor C. Blagden conducted an experiment: together with several friends, he spent 35 minutes in a dry chamber at a temperature of + 126 ° C without any health consequences. At the same time, a piece of meat taken into the chamber turned out to be boiled, and cold water boiled under a layer of oil.
Hall: analyze the data and determine the dependence of heat transfer on environmental conditions. Fill the table.
Slide number 5. The correctness of the assignment is checked.
Independent work with the textbook. Task: fill in the table "First aid in case of violation of thermoregulation".
Anchoring.
Questions for checking knowledge at the compulsory level:
What is the role of the skin in thermoregulation?
How to prevent heat and sunstroke?
What is the danger of a significant burn of the body?
Questions for testing knowledge at an advanced level:
Why is heat easier to tolerate in dry desert than in humid rainforest?
What should be summer and winter clothes?
Why is it unacceptable to use alcoholic beverages to "warm" with hypothermia?
Homework.
Test on the topic "Structure and function of the skin"
1. The skin protects deeper organs and tissues from damage, as it ...
A) strong and resilient
B) maintains the constancy of the internal environment of the body
B) waterproof
D) contains many receptors
2. The skin protects the body from ultraviolet rays, because in it ...
A) a lot of fibers
B) there is subcutaneous fatty tissue
C) there are receptors
D) vitamin D is produced
3. The epidermis is located ...
A) on the surface of the skin
B) under the skin itself
B) on the surface of the subcutaneous fatty tissue
D) under the subcutaneous fatty tissue
4. The skin itself ...
A) forms keratinized cells
B) gives the skin elasticity
B) inhibits ultraviolet rays
D) does not allow liquids and gases to pass through
5. Fat is secreted ...
A) sweat glands
B) sebaceous glands
C) receptors
D) lymphatic vessels
Let's try to figure out how a constant temperature of 36.6 C is maintained in the human body?
And yet, the body temperature does not change. Why do you think? Now, I wonder why our body temperature remains constant? Some processes take place in the human body.
Now we will try to explain the mechanism of the formation and release of heat. Let's work with the diagram.
Task number 1. Analyze and explain the diagram.
Conversation according to the scheme. Here is a table. When you eat hot food, the body becomes warm. And when?
To do this, I suggest you fill out the table.
Task number 2. Fill in the table "Regulation of heat transfer by blood vessels". Valeological pause (music)
Task number 3 ... A also, what conditions are favorable for heat regulation? Correctly selected clothing for the seasons of the year, depending on the ambient temperature and quality.
Let's make a simple experiment: take glass sticks, dip them in water and touch them to the skin of your hand, how did you feel?
Task number 4 Problem situation from everyday life.
In summer, on a sunny day, Masha played for a long time with her friends on the beach. When she returned home, she had a fever, had a headache and was very thirsty. The grandmother thought that the granddaughter had a cold, gave her tea, wrapped her in a blanket. But Masha did not get better. The doctor who arrived on call for some reason scolded the grandmother for her actions. Why do you think?
What happened to the girl? (got sunstroke)
What was your grandmother wrong? (did not give first aid correctly)
What measures should be taken in case of heat and sunstroke?
Conclusion: An increase in body temperature depends on the ambient temperature, and we must know the rules of first aid for heat and sunstroke.
Now, guys, let's work in groups and solve biological problems. 1st group: The effect of alcohol on the body causes vasodilation. Which person, sober or drunk, will freeze faster in the cold? Warm blood heats the skin. Thermal receptors create a feeling of warmth. The vessels of the deep layers of the skin are diluted and the person loses the last heat. Expansion or constriction of blood vessels creates a feeling of warmth. The release of excess heat occurs in the skin vessels, in which 30% of the entire blood of the body can be accommodated.
Group 2:
The development of a febrile state is often accompanied by tremors and a feeling of coldness (chills). Explain these symptoms based on the understanding of the thermoregulatory mechanism (water evaporates, the body cools). Chills are muscle contractions. With muscle contraction, the blood vessels narrow, the temperature is injected. It is the body’s protective property to fight infection.
Conclusion: Thus, heat regulation occurs due to the vessels of the skin, sweat glands, and the nervous system.
And now we solve the test individually, consisting of 6 questions. Evaluation criteria: 6 points - "5",
5 points - "4", 4 - 3 points - "3", 1-0 points - "2".
Let's look at the problematic issue with you:
Task number 6. Why do some people, being outside at low temperatures, quickly freeze and catch colds, and others are in the cold for a long time and do not get sick?
Yes, hardening is indeed one of the ways to strengthen and maintain health. .
What is the motto of hardening? Motto: "The sun, air and water are our best friends!"
You can choose to comment on your homework.
P. 168-170 textbook, answer questions 1-4 orally
- Draw up a memo "5-point hardening rules"
Kobzeva Irina Valerievna
Lesson topic: The role of the skin in thermoregulation.
Target: to form the concept of "thermoregulation", to highlight the reasons that affect sweating.
Tasks:
1. To reveal the role of the skin in the regulation of body temperature.
2. Be able to use personal experience in establishing the dependence of heat transfer on environmental conditions.
3. To develop the skills of independent work with the text of the textbook to obtain the necessary information.
Lesson plan:
1. Organizational moment.
2. Statement of a problem situation.
3. "Opening" the topic of the lesson, setting the goal and objectives of the lesson.
4. Experiment.
5. Learning new material.
6. Anchoring.
During the classes.
Checking d / z
Slide number 1. Questions:
1) By what principle are these animals divided into two groups? (Crucian carp, frog, snake, lizard, hare)
2) Which of these groups does the person belong to?
Slide number 2. Now imagine that we are in 15th century Italy. In the luxurious castle of the Duke of Moreau of Milan, a magnificent celebration is taking place, the idea of which was invented by the great Leonardo da Vinci.He planned to celebrate the golden age of the world, which came after many years of the Iron Age of devastating wars.
To depict the Iron Age, blacksmiths under the supervision of Leonardo da Vinci made a huge figure of a reclining knight, chained in armor. And the golden age was supposed to depict a naked boy, covered from head to toe with gold paint. This was the son of a poor baker. Father for money provided him for the amusement of the duke.
In the midst of the festive fun, the defeated knight was brought into the hall. From his womb came a "golden boy" with wings and a laurel branch in his hand. Frightened, he looked at those around him, uttering a memorized greeting to the duke.
After the holiday, everyone forgot about him. And only the next day, Leonardo da Vinci found the baby in a dark corner of the cold room. He was crying and shivering from the cold. The boy died a few days later.
Question: What is the reason for the death of the "golden boy"?
You can write down the versions that the guys are proposing on the board.
Teacher: You guessed it, the topic of our lesson is one of the functions of the skin: thermoregulation.
Together with the students, the topic of the lesson, goal, tasks are formulated.
For a long time, no one could explain the reason for the death of the child. It was assumed that the gold paint disturbed the perspiration, the intake of air into the body. Only much later, inXIXcentury, found that the cause is associated with a violation of thermoregulation.
III. Learning new material.
The skin is the organ of thermoregulation.
Skin reaction to ambient temperature (teacher's story).
Causes affecting sweating (story with elements of conversation, research).
From the point of view of physics, a person is just a physical body and it would seem that processes should occur with him, the same as with any physical bodies. The human body temperature is 36.6С, and in the classroom it is 24С. A person must give part of his internal energy to the surrounding air until the temperature becomes the same. But is it really so? (No)
What new should we learn on this topic? Let's formulate the goals of our lesson (students formulate goals, and the teacher specifies them)
Explain why our body temperature remains constant.
To answer this question, we must remember the structure of the skin. (slide 3)
In the human body, in 1 hour, as much heat is generated as is needed to boil 1 liter of ice water. During hard physical work, the generation of heat increases several times. And yet, the body temperature does not change.
Question:
Why do you think the body temperature remains constant?
Supposed answer:
The body temperature does not change because the body gives off heat.
The constancy of body temperature is maintained by regulating the release of heat from the body. And this role belongs to our skin, since this organ is in direct contact with the external environment and, therefore, registers the change in its temperature.
1.What is thermoregulation? (This is the body's ability to maintain a constant body temperature in a changing environment; or it is the balancing of the processes of formation and release of heat in the body).
2. Why is thermoregulation necessary for the body? (Thermoregulation ensures a constant body temperature within the range from 36.5 ° C to 36.9 ° C, which is very important for the functioning of proteins and other organic substances. A person can tolerate only slight fluctuations in body temperature. Its rise above 43 ° C and falling below 25 ° C is usually fatal ).
3. What are the mechanisms of thermoregulation? (Thermoregulation is carried out due to changes in the lumen of blood vessels and sweating).
For the body to give off heat to the environment, the heat it generates must "have access" to the external environment. Heat from deep inside the body is transported by blood to the skin, from where it can be transferred to the environment. Thermoregulation processes depend on the amount of blood flowing through the skin.
But how it depends, we will check by conducting the laboratory work "Circulatory disorders when applying a constriction."
You have all the necessary materials and instructions on your tables (Appendix 1)Why does the temperature of the insulated fingers get lowered?Human skin is abundantly supplied with blood vessels. Many capillaries form loops that allow the amount of blood flowing through the cutaneous capillaries to change. With the narrowing of these vessels, heat transfer decreases. When they expand, the generation of heat increases.
The formation and release of heat is regulated reflexively and humorally. There is a thermoregulatory center located in the hypothalamus (diencephalon). It is believed that in its front part there are centers that regulate heat transfer, and in the region of the posterior hypothalamus there are centers that control the processes of production and preservation of heat.Video.
The ambient temperature and its fluctuations act on the thermoreceptors of the skin. It is calculated that there are 12 cold receptors per 1 cm2, 1-2 heat receptors. And the entire skin surface of the human body contains 250 thousand cold receptors and only 30 thousand heat receptors.
The vasodilatation can occur under the influence of some environmental factors, for example, irritation, application of various substances (gold paint) to the skin, blood alcohol content, etc.
The death of the "golden boy" is discussed again, the reason is established. (Under the influence of irritation, the vessels of the skin expanded, it was very cold in the hall, the body gave off heat and the boy died of hypothermia).
More than 200 years ago, the English doctor C. Blagden conducted an experiment: together with several friends, he spent 35 minutes in a dry chamber at a temperature of + 126 ° C without any health consequences. At the same time, a piece of meat taken into the chamber turned out to be boiled, and cold water boiled under a layer of oil. (sweating and cooling of the skin surface occurred through the skin).
Heat transfer by evaporation of sweat occurs continuously in the form of perspiration invisible to us. Sweat is a watery liquid containing 0.1-0.4% sodium chloride, sodium lactate and urea. It is formed from tissue fluid.
In humans, sweating begins when the temperature rises above 36.70C. Under normal conditions, 900 ml are released per day, but with very intense heat and an adequate supply of water and salts, this value can reach 12 liters.
Now you will carry out one more laboratory work "Excretory and thermoregulatory function of the skin"
Purpose: to investigate the thermoregulatory and excretory function of human skin. Conclusion: Human skin secretes water, together with it, excess salts are released. Evaporating, moisture cools the skin, thereby participating in the thermoregulation of the body.
Progress:
Place the bag over your wrist and secure it around your wrist with a rubber ring or string. Record observations for 5-6 minutes.
While the experiment is running, we will complete the following task.
Assignment: Analyze the data and determine the dependence of heat transfer on environmental conditions. Fill the table(video).
Environment conditions
Prevents heat dissipation
Promotes heat release
1. The air is dry, its temperature is lower
body temperature.
2. The air is saturated with water vapor, its temperature is low,
3. The air is dry, its temperature is higher than the body temperature.
4. The air is humid and hot.
Answer the following questions:1. Why does the temperature in the bag rise during the experiment? (heat transfer occurs)2. Why does the moisture in the bag rise? (sweating occurs).3. Why are summer clothes made from natural and not synthetic fabrics?
4. What is the significance of the function of perspiration for the body?
Anchoring.
What did we learn in lesson today?
Now let's try to formulate the main conclusions of this lesson.1) What is the role of the skin in thermoregulation?2) Depending on the nature of the implementation of thermoregulatory mechanisms, there are two groups of animals (warm-blooded and cold-blooded).3) What is Thermoregulation? (Is the process of balancing heat generation and heat transfer in accordance with the conditions of the external and internal environment).4) What can lead to Violation of thermoregulation processes (can lead to overheating or hypothermia of the body).
D.Z. Solve biological problems:
The effect of alcohol on the body causes vasodilation. Which person, sober or drunk, will freeze faster in the cold?
Feet in tight shoes freeze in winter. Explain why?