Why Do We Shiver

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  Why Do We Shiver? The human body has many amazing systems that help keep us running smoothly through various conditions. Our body has homeostatic functions  that automatically monitor, adjust and regulate our important systems without our even knowing it. Breathing, heart rate, weight regulation and  blood pressure are all regulated subconsciously. Shivering is just one of these homeostatic functions our body employs to regulate our body temperature. Also called thermoregulatory shivering,  we shiver in an effort to keep ourselves warm. Our   brain  both consciously and subconsciously detects cold simultaneously through different sensory systems, which prompts the body to shiver  —   the sensory system that prompts the shiver isn’t the same as our conscious detection of cold. Our body attempts to maintain our core temperature of 98.6 degrees Fahrenheit (37 degrees C), despite ambient temperature. In an attempt to avoid hypothermia where our body temperature is lowered to dangerous levels, our muscles are prompted to contract and expand quickly, resulting in a shiver. This in turn  produces more heat in the skeletal muscles to provide extra warmth to our organs. It does use a lot of energy, and severe shivering is a last resort in an attempt to stay warm. Along with shivering, your teeth may chatter due to tightening jaw muscles. In some cases, we shiver after having anesthesia, because the drugs and medication affects the body’s ability to regulate our temperature. This may result in a drop in our core body temperature, and we shiver to compensate. It is usually a transitory side affect, and should resolve in less than an hour. Those suffering with a fever may also shiver and shake with chills. Although they may have a temperature above 98.6 degrees, the “set point” of the    body’s temperature has been raised by the brain by the onset of a fever. This prompts the body to do things to make it warmer. Shivering when you have a fever creates more heat as it would in the cold, thus, elevating your body’s temperature even more. Shivering is just another way our body works to maintain itself  —   take it as a clue to get out of the cold or add another layer. Remember also that as we age, our sensory systems have a decreased ability to identify changes in temperature and respond accordingly. Elderly people should rely less on our body’s automatic response systems, and more on common sense in extreme cold, or heat. Shivering From Wikipedia, the free encyclopedia Shiver redirects here. For other uses, see Shiver (disambiguation).  This article needs additional citations for verification . Please help improve this article  by adding citations to reliable sources. Unsourced material may be challenged and removed. (September 2014)   Shivering  (also called rigors  or shuddering ) is a bodily function in response to early hypothermia or just feeling cold [1]  in warm-blooded animals. When the core  body temperature drops, the shivering reflex is triggered to maintain homeostasis. Muscle groups around the vital organs  begin to shake in small movements, creating warmth by expending  energy. Shivering can also be a response to a fever , as a person may feel cold. During fever the hypothalamic set point for temperature is raised. The increased set point causes the body temperature to rise ( pyrexia), but also makes the patient feel cold until the new set point is reached. Rigor occurs because the patient's body is effectively shivering in a physiological attempt to increase body temperature to the new set point. Located in the posterior  hypothalamus near the wall of the third ventricle is an area called the  primary motor center for shivering. This area is normally inhibited by signals from the heat center in the anterior hypothalamic-preoptic area but is excited by cold signals from the skin  and spinal cord. Therefore, this center becomes activated when the body temperature falls even a fraction of a degree below a critical temperature level. Increased muscular activity results in the generation of heat as a byproduct. Most often, when the purpose of the muscle activity is to produce motion, the heat is wasted energy. In shivering, the heat is the main intended product and is utilized for warmth. Shivering can also appear after surgery. This is known as  postanesthetic shivering.   Newborn babies, infants, and young children experience a greater (net) heat loss than adults  because they cannot shiver to maintain body heat. They rely on non-shivering thermogenesis.  Children have an increased amount of   brown adipose tissue (increased vascular supply, and high mitochondrial density), and, when cold-stressed, will have greater oxygen consumption and will release norepinephrine. Norepinephrine will react with lipases in  brown fat to break down fat into triglycerides. Triglycerides are then metabolized to glycerol and non-esterified fatty acids. These are then further degraded in the needed heat-generating process to form CO 2  and water. Chemically, in mitochondria the proton gradient producing the  proton electromotive force that is ordinarily used to synthesize ATP is instead bypassed to produce heat directly http://en.wikipedia.org/wiki/Shivering Brrr!! Shivering is when your muscles contract and relax quickly, causing uncontrollable quivering all over your body. This is an involuntary muscle reaction to a variety of conditions, the most common of which is feeling cold. Fever, illness, fear, childbirth, orgasms, or other circumstances can also set off the shivers. Fevers produce shivering because they can cause one to feel cold, even though the person’s core temperature is higher than normal. Internal organs can shiver, too! In the case of a reaction to cold, a drop in skin and body temperature will signal the hypothalamus. Once activated, this part of the brain stimulates muscle contractions (the shivering reflex) in order to warm up your body. After enough heat has been produced, the shivering stops. Did you know that babies and very young children can’t shiver? That’s one reason for the extra baby fat. Whe n they’re cold, babies thermo -regulate by burning fat in a process called thermogenesis, rather than by shivering, which is the same mechanism used by hibernating mammals to keep warm. Goose bumps are caused by the pilomotor reflex. When you're exposed to cold temperatures or intense emotional stimuli (such as awe, pleasure, or fear), or if your skin's irritated, this  reflex triggers an involuntary muscle contraction that raises the hairs of your skin, producing goose bumps. This response to cold or other stimuli, known as piloerection, results in erect hairs trapping air near the skin, thereby retaining heat for the body (this feature works better in mammals with more fur than humans). In a fear reaction, shivering and goose bumps are triggered by adrenaline. This is why strong emotional experiences, especially fear, can produce shivering or “the chills.” Again, for mammals with lots of fur, all the erect hair makes them appear larger and more threatening to  predators. And in the case of some mammals, like the porcupine, this makes them not only appear more threatening, but more dangerous as well. Stay warm! http://goaskalice.columbia.edu/goosebumps-and-shivers 
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