What Controls Homeostasis In The Brain
Beside this, how the brain maintains homeostasis?
The nervous system maintains homeostasis by controlling and regulating the other parts of the body. A deviation from a normal set point acts as a stimulus to a receptor, which sends nerve impulses to a regulating center in the brain.
Similarly, what controls homeostasis? The endocrine system plays an important role in homeostasis because hormones regulate the activity of body cells. The release of hormones into the blood is controlled by a stimulus. For example, the stimulus either causes an increase or a decrease in the amount of hormone secreted.
In this regard, what part of the brain controls homeostasis?
What are the 3 components of homeostasis?
Homeostatic control mechanisms have at least three interdependent components: a receptor, integrating center, and effector. The receptor senses environmental stimuli, sending the information to the integrating center.
How Does The Human Body Maintain Homeostasis
The human body is an exquisite machine, partly because it maintains functionality in a variety of environments. Humans can thrive in conditions ranging from the arctic to the equator, and with a variety of diets and lifestyles. Part of the reason for this adaptability is the bodys ability to maintain homeostasis.
Homeostasis is a fancy word meaning “equilibrium,” and it entails many interwoven variables that are amazing to consider. Temperature is among the most straightforward of these. The body sweats to keep cool and shivers to stay warm. But the human body is masterful at balancing many other factors. Most are subtler, involving the regulation of hormones and other bodily chemicals. All of the bodys systems self-regulate using an intricate coordination of three principle roles: signal reception, centralized control and action.
The Autonomic Nervous System
The autonomic nervous system is comprised on the sympathetic and parasympathetic nervous systems which both have critical homeostatic functions. The sympathetic system innervates the heart and increases heart rate and the force of its contractions. It also controls the constriction of blood vessels and dilation of bronchioles in the lungs. The parasympathetic system has the opposite effects on the heart and lungs but is has no effect on blood vessels.
The image above shows the components of the nervous system. Note the green and red dots indicating the structure and function, respectively, within each component.
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A Dilemma: To Bbb Or Not To Bbb
Areas of the brain that contain fenestrated blood vessels have been known to scientists for quite a while. However, it is still unclear how the vessels in these regions remain leaky. The blood vessels of the brain face a dilemma: to make fenestrae that enable communication with the body at the risk of infection, or to protect the brain from harmful invaders by isolating it. We sometime call this dilemma To BBB or not to BBB? after the famous quote from William Shakespeares play Hamlet: To be or not to be, that is the question .
The Cell Structure Of The Brain
The brain is made up of two types of cells: neurons and glial cells, also known as neuroglia or glia. The neuron is responsible for sending and receiving nerve impulses or signals. Glial cells are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin and facilitate signal transmission in the nervous system. In the human brain, glial cells outnumber neurons by about 50 to one. Glial cells are the most common cells found in primary brain tumors.
When a person is diagnosed with a brain tumor, a biopsy may be done, in which tissue is removed from the tumor for identification purposes by a pathologist. Pathologists identify the type of cells that are present in this brain tissue, and brain tumors are named based on this association. The type of brain tumor and cells involved impact patient prognosis and treatment.
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Intrinsic Mechanisms: Renal Autoregulation
Renal autoregulation refers to the intrinsic ability of the kidney to respond to a perturbation that elicits a vasoactive response, which alters renal vascular resistance in the direction that maintains RBF and GFR. Changes in perfusion pressure are the manipulation most commonly used to demonstrate autoregulatory efficiency. Although the efficiency with which blood flow is maintained differs from organ to organ , all organs and tissues exhibit autoregulation. As shown inFig. 3.17, the kidney autoregulates renal blood flow over a wide range of renal perfusion pressures. Autoregulation of blood flow in response to changes in perfusion pressure requires parallel changes in resistance.
Disease As A Homeostatic Imbalance
What Is Disease?
Disease is any failure of normal physiological function that leads to negative symptoms. While disease is often a result of infection or injury, most diseases involve the disruption of normal homeostasis. Anything that prevents positive or negative feedback system from working correctly could lead to disease if the mechanisms of disruption become strong enough.
Aging is a general example of disease as a result of homeostatic imbalance. As an organism ages, weakening of feedback loops gradually results in an unstable internal environment. This lack of homeostasis increases the risk for illness and is responsible for the physical changes associated with aging. Heart failure is the result of negative feedback mechanisms that become overwhelmed, allowing destructive positive feedback mechanisms to compensate for the failed feedback mechanisms. This leads to high blood pressure and enlargement of the heart, which eventually becomes too stiff to pump blood effectively, resulting in heart failure. Severe heart failure can be fatal.
Diabetes: A Disease of Failed Homeostasis
Normal Blood Sugar Regulation
Figure 8.5. Homeostasis of Glucose Metabolism: This image illustrates glucose metabolism over the course of a day. Homeostasis may become imbalanced if the pancreas is overly stressed, making it unable to balance glucose metabolism. This can lead to diabetes.
Causes of Homeostatic Disruption
Like Dissolves Like.
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How Does The Nervous System Maintain Homeostasis
Of all the body systems, the nervous system is the major control system of homeostasis. It provides monitoring, response, and regulation of all systems in the human body and other organisms. It functions from the tiny level of individual cells to affecting the whole body at once.
Receptors inside and outside the body are constantly monitoring conditions and watching for changes. When a body system leaves a set point and falls outside its normal range, signals are sent through the nervous system which trigger responses to bring the system back into the normal range of functioning. This is the process of homeostasis. These complicated and intricate processes have evolved over millions of years. For example, thermoreceptors and mechanoreceptors in the skin sense changes in temperature and pressure, respectively. Then, signals sent from them to the brain make it possible to detect situations that could cause injury or death. In addition, nerves make muscles contract which moves the bones of the skeleton, making it possible to evade predators and/or fight. This ability to perceive the environment and reacting to it is critical to maintaining homeostasis in the body.
The Hypothalamus: The Brains Center Of Homeostasis
So far, we have described how the brain collects information from the body and decides which commands to send in order to maintain homeostasis. The specific region of the brain where most of this activity takes place is called the hypothalamus, which means under the inner chamber in Greek . The hypothalamus controls many important body functions, such as sleep, blood pressure, temperature, hunger, thirst, and energy consumption and storage. Much like a computer microprocessor, the hypothalamus runs an algorithm that computes the information by following a set of rules. Then, the hypothalamus makes a decision about whether or not to send commands to the body. This type of computation occurs in brain cells called neurons. The neurons in the hypothalamus can receive feedback both from inside the body and from the external environment. They can also produce various hormones.
- Figure 2 – The meeting point between hypothalamic neurons and pituitary capillaries.
- On the right, the hypothalamus is highlighted in green and the pituitary in blue. On the left, you can see that commands from the hypothalamus travel along the neurons to the pituitary gland. The pituitary then releases commands in the form of hormones into the bloodstream, via the fenestrated capillaries.
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Nuclei Of The Hypothalamus
As mentioned above, the hypothalamus actually consists of a collection of nuclei, each of which have their own functional roles in the brain. In this section, I will briefly discuss the main hypothalamic nuclei and summarize some of their functions. It’s important to note that this will not be a complete list of all of the nuclei in the hypothalamus, nor a thorough explanation of everything those nuclei are involved in . Also, some hypothalamic nuclei are subdivided into smaller nuclei I will not go into that level of detail in this section. Finally, it’s important to mention that the nuclei of the hypothalamus are paired structures, meaning there is one nucleus on either side of the midline of the hypothalamus. So, while below I will discuss individual nuclei such as the suprachiasmatic nucleus, this would be more accurately described as the suprachiasmatic nuclei because there are two of them.
The anterior hypothalamus contains a region called the preoptic area, which contains several preoptic nuclei. Different nuclei of the preoptic area are involved in: the regulation of blood composition and volume , the regulation of body temperature, sleep regulation, and reproductive behavior. You can read more about the preoptic area in this article: Know Your Brain: Preoptic Area.
The anterior nucleus is situated above the supraoptic nucleus it is best-known for its role in the regulation of body temperature.
Levels Of Blood Gases
Changes in the levels of oxygen, carbon dioxide, and plasma pH are sent to the respiratory center, in the brainstem where they are regulated.The partial pressure of oxygen and carbon dioxide in the arterial blood is monitored by the peripheral chemoreceptors in the carotid artery and aortic arch. A change in the partial pressure of carbon dioxide is detected as altered pH in the cerebrospinal fluid by central chemoreceptors in the medulla oblongata of the brainstem. Information from these sets of sensors is sent to the respiratory center which activates the effector organs the diaphragm and other muscles of respiration. An increased level of carbon dioxide in the blood, or a decreased level of oxygen, will result in a deeper breathing pattern and increased respiratory rate to bring the blood gases back to equilibrium.
Too little carbon dioxide, and, to a lesser extent, too much oxygen in the blood can temporarily halt breathing, a condition known as apnea, which freedivers use to prolong the time they can stay underwater.
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When To See A Doctor
Autonomic disorders can be serious. People who experience symptoms of an autonomic disorder should see a doctor for a full diagnosis.
Talking to a doctor is particularly important for people with diabetes or other conditions that can increase the likelihood of autonomic disorders.
To diagnose the cause of ANS symptoms, a doctor will first assess a persons medical history for risk factors.
A doctor may also request one or more of the following:
- Tests to detect orthostatic hypotension: A doctor may measure OH using a tilt-table test. In this test, a person lies on a bed that tilts their body at different angles while a machine records their heart rate and blood pressure.
- Electrocardiogram: This test measures electrical activity within the heart.
- Sweat test: This test assesses whether the sweat glands are functioning correctly. A doctor uses electrodes to stimulate the sweat glands and measures the volume of sweat they produce in response to the stimulus.
- Pupillary light reflex test: This test measures how sensitive the pupils are to changes in light.
What Is The Hypothalamus And What Does It Do
The hypothalamus is a collection of nuclei with a variety of functions. Many of the important roles of the hypothalamus involve what are known as the two H’s: Homeostasis and Hormones.
Homeostasis is the maintenance of equilibrium in a system like the human body. Optimal biological function is facilitated by keeping things such as body temperature, blood pressure, and caloric intake/expenditure at a fairly constant level. The hypothalamus receives a steady stream of information about these types of factors. When it recognizes an unanticipated imbalance, it enacts a mechanism to rectify that disparity.
The hypothalamus generally restores homeostasis through two mechanisms. First, it has connections to the autonomic nervous system, through which it can send signals to influence things like heart rate, digestion, and perspiration. For example, if the hypothalamus senses that body temperature is too high, it may send a message to sweat glands to cause perspiration, which acts to cool the body down.
The hypothalamus thus has widespread effects on the body and behavior, which stem from its role in maintaining homeostasis and its stimulation of hormone release. It is often said that the hypothalamus is responsible for the four Fs: fighting, fleeing, feeding, and fornication. Clearly, due to the frequency and significance of these behaviors, the hypothalamus is extremely important in everyday life.
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Causes And Risk Factors Of Hypothalamus Disorders
A physical injury to the head that impacts the hypothalamus is one of the most common causes of hypothalamic dysfunction. Others include surgery, brain injury, brain tumors or radiation treatment to the brain.
Less common causes can include nutrition problems such as eating disorders, blood vessel problems in the brain, certain genetic disorders or certain immune system diseases that lead to infection or inflammation in the brain.
What Are The Parts Of The Brain
The brain is made up of three main sections: the forebrain, the midbrain, and the hindbrain.
The forebrain is the largest and most complex part of the brain. It consists of the cerebrum the area with all the folds and grooves typically seen in pictures of the brain as well as some other structures under it.
The cerebrum contains the information that essentially makes us who we are: our intelligence, memory, personality, emotion, speech, and ability to feel and move. Specific areas of the cerebrum are in charge of processing these different types of information. These are called lobes, and there are four of them: the frontal, parietal, temporal, and occipital lobes.
The cerebrum has right and left halves, called hemispheres. They’re connected in the middle by a band of nerve fibers that lets them communicate. These halves may look like mirror images of each other, but many scientists believe they have different functions:
- The left side is considered the logical, analytical, objective side.
- The right side is thought to be more intuitive, creative, and subjective.
So when you’re balancing your checkbook, you’re using the left side. When you’re listening to music, you’re using the right side. It’s believed that some people are more “right-brained” or “left-brained” while others are more “whole-brained,” meaning they use both halves of their brain to the same degree.
In the inner part of the forebrain sits the thalamus, hypothalamus, and :
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Making Chemical Connections: Neurotransmitters
The chemical exchange between neurons occurs at synapses, the small spaces separating the dendrites and axon endings .
Figure 2.10 The synapse
The first nerve cell releases chemical neurotransmitters that can bind with receptors in the second neuron. The exchange can result in excitation or inhibition, depending upon the type of receptor activated. Figure 2.11 lists the major neurotransmitters along with their roles in the body.
Figure 2.11 The major neurotransmitters
Psychoactive drugs can affect mood, thought, and behavior. Most achieve these effects by impacting upon neurotransmitters and synaptic connections. In Chapter 11 , we will consider the use of psychoactive drugs in the treatment of depression and schizophrenia.
Movement Of Molecules Across The Membrane
One of the great wonders of the cell membrane is its ability to regulate the concentration of substances inside the cell. These substances include ions such as Ca++, Na+, K+, and Cl nutrients including sugars, fatty acids, and amino acids and waste products, particularly carbon dioxide , which must leave the cell.
Whenever a substance exists in greater concentration on one side of a semipermeable membrane, such as the cell membranes, any substance that can move down its concentration gradient across the membrane will do so. Consider substances that can easily diffuse through the lipid bilayer of the cell membrane, such as the gases oxygen and CO2. O2 generally diffuses into cells because it is more concentrated outside of them, and CO2 typically diffuses out of cells because it is more concentrated inside of them. Neither of these examples requires any energy on the part of the cell, and therefore they use passive transport to move across the membrane.
Figure 8.12. Simple Diffusion across the Cell Membrane. The structure of the lipid bilayer allows small, uncharged substances such as oxygen and carbon dioxide, and hydrophobic molecules such as lipids, to pass through the cell membrane, down their concentration gradient, by simple diffusion.
Figure 8.13. Facilitated Diffusion.Figure 8.14. Osmosis.Figure 8.15. States of Tonicity.
Figure 8.16 The turgor pressure within a plant cell depends on the tonicity of the surrounding solution.
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What Does The Brain Do
The brain controls what we think and feel, how we learn and remember, and the way we move and talk. But it also controls things we’re less aware of like the beating of our hearts and the digestion of our food.
Think of the brain as a central computer that controls all the body’s functions. The rest of the nervous system is like a network that relays messages back and forth from the brain to different parts of the body. It does this via the spinal cord, which runs from the brain down through the back. It contains threadlike nerves that branch out to every organ and body part.
When a message comes into the brain from anywhere in the body, the brain tells the body how to react. For example, if you touch a hot stove, the nerves in your skin shoot a message of pain to your brain. The brain then sends a message back telling the muscles in your hand to pull away. Luckily, this neurological relay race happens in an instant.