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The cells that make up the nervous tissues are specialized to receive and send electrical impulses from one area of the body to another.
The cell body of the neuron is the large structure with a central nucleus.
Projections from the cell body are either dendrites or a single axon.
Some glial cells are shown.
Astrocytes regulate the chemical environment of the nerve cell, and oligodendrocytes insulate the axon so the electrical nerve impulse is transferred more efficiently.
glial cells that aren't shown support the nutrition and waste requirements of the neuron
The glial cells remove debris from the tissue.
A nerve is made of cells.
There are projections called dendrites that receive signals and projections called axons that send signals in the neuron.
There are two types of glial cells that insulate the axon and regulate the chemical environment of the nerve cell.
Click through the interactive review to learn more about the tissues.
A Pathologist is a doctor who specializes in the detection of diseases in animals and humans.
Medical school education is followed by an extensive post-graduate residency at a medical center.
The evaluation of body tissue and blood samples for the detection of disease can be done by a pathologist.
They use a microscope to look for cancer and other diseases.
Pathologists perform autopsies to determine the cause of death.
By the end of this section, you will be able to discuss positive and negative feedback mechanisms used in homeostasis.
The changes might be in the level of blood sugar or calcium in the body.
It is constantly adjusting to the changes in the body's systems.
Body functions are kept within certain ranges.
This homeostatic equilibrium is maintained by an animal that is inactive.
The body's systems try to go back to this point when there are normal fluctuations from the set point.
The response of the system is to adjust the deviation parameter toward the set point when a change in the internal or external environment is detected.
Changes are made to cool the animal if it becomes too warm.
If the blood's sugar goes up after a meal, it's a good idea to get the nutrition into tissues that need it or to store it for later use.
An adjustment must be made when there is a change in an animal's environment.
In most cases, the brain sends a signal to the control center when the environment changes, which in turn signals an effector.
The effector is a muscle that contracts or relaxes.
Homeostatsis is maintained by negative feedback loops.
Positive feedback loops may be necessary for life to occur.
Homeostasis is controlled by mammals.
It can either increase or decrease theStimulus, but it is not allowed to continue as it was before.
If a level is too high, the body does something to bring it down, and if a level is too low, the body does something to make it go up.
An example is the maintenance of blood sugar levels in animals.
Blood sugar levels rise when an animal eats.
The nervous system senses this.
The hormones in the endocrine system are released by specialized cells in the pancreas.
If an animal doesn't eat or have low blood sugar levels, the hormone glucagon is released in another group of cells in the pancreas, which causes the levels to increase.
The control of blood calcium is an example of an increase as a result of the feedback loop.
The breakdown of bone in order to liberate calcium is possible if calcium levels decrease because specialized cells in the parathyroid glands sense this and release parathyroid hormone.
Blood levels of the element are raised by the effects of PTH.
Negative feedback loops are the main mechanism used in the body.
A negative feedback loop controls blood sugar levels.
There are few examples of positive feedback loops in animal bodies, but one can be found in the cascade of chemical reactions that result in blood clotting.
When one clotting factor is activated, the next factor in sequence is activated.
This is positive feedback because the direction is not changed.
The contraction of the uterus is stimulated by the hormone oxytocin.
This causes pain to be felt by the nervous system.
Instead of causing the pain to go away, more oxytocin is produced until the baby is born.
Positive feedback is what leads to the birth of a human infant.
The following processes are regulated by a positive or negative feedback loop.
A person feels happy after eating.
There is a lot of red blood cells in the blood.
Erythropoietin, a hormone that stimulates the production of new red blood cells, is no longer released from the kidneys.
It's possible to change a system's set point.
The feedback loop works to keep the new setting.
Over time, the normal or set point for blood pressure can increase as a result of continued increases in blood pressure.
The body no longer recognizes the elevation as normal and no attempt is made to return to the lower set point.
Maintaining elevated blood pressure can have harmful effects on the body.
The set point in the system can be lowered with medication.
In order to maintain a set point in another system, changes can be made in a group of body organ systems.
This happens when an animal migrates to a higher altitude than it is used to.
The body increases the number of red blood cells in order to adjust to the lower oxygen levels at the new altitude.
An example of acclimatization is an animal that has a heavier coat in the winter and a light coat in the summer to keep their body temperature from rising to harmful levels.
If you want to understand feedback mechanisms, watch a short video lesson on positive and negative feedback loops.
Body activities are affected by body temperature.
As body temperature increases, the activity of the enzyme increases as well.
The high heat of 50oC causes the body to denature and lose function.
For every ten degree centigrade drop in temperature, the activity of the enzymes will decrease by half.
Some fish can return to normal after being frozen solid.
You can watch the Discovery Channel video on thermoregulation to see illustrations of the process in a variety of animals.
Some animals have a constant body temperature in the face of differing environmental temperatures, while others have a body temperature that is the same as their environment.
Animals rely on external temperatures to set their body temperature.
The term cold-blooded may not apply to an animal in the desert with a very warm body temperature.
Animals with constantly varying internal temperatures are called poikilotherms.
A homeotherm is an animal that has a constant body temperature.
Animals that rely on internal sources for body temperature maintenance are called endotherms.
The animals are able to maintain a level of metabolism at cooler temperatures because of differing levels of activity.
Some animals have relatively constant body temperatures due to the constant environmental temperatures in their habitats.
These animals are similar to deep sea fish.
Four mechanisms can be used to exchange heat between an animal and its environment.
The emission of heat waves is called radiation.
The heat comes from the sun and the heat comes from dry skin.
Liquid can be removed from a surface.
This happens when a mammal sweats.
As the air passes over the dry skin, it removes heat from the surface.
During direct contact with the surface, heat will be conducted from one surface to another.
Four mechanisms can be used to exchange heat.
There are a variety of ways animals conserve heat.
Fur, fat, feathers, or some combination of these are some of the insulation animals have in certain climates.
Animals with thick fur or feathers have an insulation layer between their skin and internal organs.
The polar bears and seals live and swim in a warm environment.
The fluffy tail of the arctic fox helps it sleep in cold weather.
Small hairs stand up when the individual is cold because of the effect of arrector pili muscles, which causeose bumps.
The same layers of fat are used by mammals.
Losing body fat will affect an individual's ability to conserve heat.
The body temperature can be maintained with the help of the circulatory systems.
Vasodilation helps to cool the body by bringing more blood and heat to the surface.
Vasoconstriction reduces blood flow in peripheral blood vessels, forcing blood to the core and the vital organs found there.
Some animals have adaptions to their circulatory system that allow them to transfer heat from arteries to veins.
The countercurrent heat exchange prevents the cold blood from cooling the heart and other internal organs.
Some animals can be shut down to prevent overheating their internal organs.
The adaption to countercurrents is found in many animals.
Similar changes can help cool endotherms, such as dolphin ears.
Some animals use changes in their behavior to regulate their body temperature.
An animal in the desert may seek cooler areas during the hottest part of the day to keep from getting too warm.
During a cold desert night, animals may climb onto rocks to capture heat.
Some animals look for water to aid in cooling down.
Bee activity is used to warm a hive to survive the winter.
mammals use metabolic waste heat as a heat source Most of the energy used in muscle actions is wasted when the muscles are weakened.
Cold causes the body to generate heat.
Brown fat is a type of fat that is specialized in generating heat.
The advanced animal brain is the center of the processes of temperature control and homeostasis.
The body is able to regulate temperature.
When leuckocytes destroybacteria, they release pyrogens into the blood.
The body's thermostat is set to a higher temperature.
The set point for body temperature is maintained by the hypothalamus through reflexes that cause sweating when the body is too warm or too cold.
It responds to the body's chemicals.
There are chemicals in the blood when a bacterium is destroyed.
The hypothalamus can be used to reset the thermostat.
This allows the body's temperature to go up.
An increase in body temperature causes iron to be used less bybacteria.
An increase in body heat increases the activity of the animal's protective cells and also increases the activity of the invading microorganisms.
The pathogen may be killed by heat.
A normal defense mechanism is believed to be the cause of a fever.
There are different sizes and shapes of animal bodies.
Four of the basic building blocks of complex animals are animal size and shape.
These are combined to form organs.
Their size and development are affected by Diffusion.
Animals use and get energy from the skin and kidneys.
Organs are organized according to their size, activity level, and environment.
Epithelia, connective tissues, muscle tissues, and nervous tissues are the four primary tissues.
It is in equilibrium because body functions are kept within a normal range, with some fluctuations around a Homeostasis being a dynamic equilibrium that is maintained in set point for the processes.
A person feels happy after eating.
Simple cells are involved in the b.
There is a lot of red blood cells in the blood.
Depending on how full the bladder is, Pyrogens reset.
An animal is divided into equal right and left habitats by a plane.
The name of the substance is Plasma.
It confuses people.
The animal can gather food from all sides.
The movement in any direction is the type of muscle cell under voluntary control.
The barriers between the cells are maintained by the discs.
The type of cell found in the urinary beat is a single unit.
There is a thermostat in the body.
They are adjusting the timing of their activities.
The size of animals is constrained by a bug.
How is a condition such as diabetes a good example of endotherms?
If necessary, review it.
The loss of insulation around neuron axons is a hallmark of multiplesclerosis.
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