Adrenaline (advanced)

Adrenaline (advanced)

Adrenaline, also known as epinephrine, is a hormone produced in our bodies in stressful situations and plays an important role in the fight-or-flight response.

Biology

Keywords

adrenaline, epinephrine, stressful situation, stress, alarm reaction, hormone, neurotransmitter, sympathetic nervous system, adrenal medulla, vasoconstriction, vasodilation, catecholamine, blood sugar level, homeostasis, human, biology

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Scenes

Alarm reaction

  • brain - Blood vessels of the brain dilate, therefore the flow of blood in the brain is increased.
  • heart - The heart muscle contracts stronger and with a higher frequency. The circulatory minute volume rises. Blood vessels of the heart dilate.
  • lungs - Bronchioles dilate, the respiratory minute volume increases.
  • eyes - The pupils dilate.
  • intestines - Blood vessels of the intestines constrict; blood flows into the skeletal muscles.
  • skin - The skin becomes pale as its blood vessels constrict; blood flows into the skeletal muscles.
  • kidneys - Blood vessels of the kidneys constrict, excretory processes slow down; blood flows into the skeletal muscles.
  • skeletal muscles - The blood flow of the skeletal muscles increases. Glycogen stored in the muscles is converted into glucose, thus the blood glucose level increases.
  • liver - The liver plays a central role in the storage of glycogen. Liver glycogen is converted into glucose, thus the blood glucose level increases.

Vasoconstriction (alpha receptor)

  • smooth muscle cell
  • adrenaline - Also known as epinephrine, it is a stress hormone secreted by the medulla of the adrenal glands in response to the stimulation of the sympathetic nervous system. Its effect is practically the same as the effect of the sympathetic nervous system: it triggers the alarm reaction described by Walter Cannon, known as the fight-or-flight response.
  • alpha receptor - Our body cells contain either alpha or beta adrenaline receptors. When binding to alpha receptors, adrenaline increases the calcium (Ca²⁺) concentration; when binding to beta receptors, it increases the cAMP concentration. The smooth muscle cells of the intestines contain alpha receptors. Adrenaline causes the contraction of these blood vessels and thereby the decrease of blood flow of the intestines through increasing the Ca²⁺ concentration. Adrenaline has a similar effect on the blood vessels of the skin, this is why our skin turns pale in stressful situations.
  • G protein - A protein that plays an important role in signal transduction pathways. Out of its 3 subunits, the alpha subunit can bind GTP and activate the target protein, which, in this case, is phospholipase C.
  • GDP - Guanosine diphosphate. Its structure is similar to that of ADP, but instead of adenine, it contains guanine.
  • GTP - Guanosine triphosphate. Its structure is similar to that of ATP, but instead of guanine, it contains adenine. Its binding activates the alpha subunit of the G protein.
  • phospholipase C - An enzyme protein that cleaves the PIP2 molecule found in the cell membrane, thereby activating protein kinase C and causing the release of Ca²⁺. Therefore a metabolic change occurs in the smooth muscle cell, which contracts, causing the narrowing of the capillary.
  • activation of protein kinase C and release of Ca²⁺
  • smooth muscle cell contracts
  • vasoconstriction

Vasodilation (beta receptor)

  • smooth muscle cell
  • adrenaline - Also known as epinephrine, it is a stress hormone secreted by the medulla of the adrenal glands in response to the stimulation of the sympathetic nervous system. Its effect is practically the same as the effect of the sympathetic nervous system: it triggers the alarm reaction described by Walter Cannon, known as the fight-or-flight response.
  • beta receptor - Our body cells contain either alpha or beta adrenaline receptors. When binding to beta receptors, adrenaline increases the cAMP concentration of cells; when binding to alpha receptors, it increases the calcium (Ca²⁺) concentration. Smooth muscle cells of the blood vessels supplying skeletal muscles contain beta receptors. Adrenaline causes the dilation of these blood vessels and thereby the increase of blood flow in skeletal muscles through increasing the cAMP concentration.
  • G protein - A protein that plays an important role in signal transduction pathways. Out of its 3 subunits, the alpha subunit can bind GTP and activate the target protein, which, in this case, is adenylate cyclase.
  • GDP - Guanosine diphosphate. Its structure is similar to that of ADP, but instead of adenine, it contains guanine.
  • GTP - Guanosine triphosphate. Its structure is similar to that of ATP, but instead of guanine, it contains adenine. Its binding activates the alpha subunit of the G protein.
  • adenylate cyclase - An enzyme protein that can synthesize cAMP (cyclic AMP) from ATP. cAMP is a second messenger important in many biological processes.
  • ATP
  • smooth muscle cell relaxes
  • vasodilation

Rising blood glucose level (beta receptor)

  • glucose release - In stressful situations, blood glucose level rises. Cells produce the most ATP by breaking down glucose, therefore the rising blood glucose level covers the energy need of the fight-or-flight response described by Walter Cannon.
  • adrenaline - Also known as epinephrine, it is a stress hormone secreted by the medulla of the adrenal glands in response to the stimulation of the sympathetic nervous system. Its effect is practically the same as the effect of the sympathetic nervous system: it triggers the alarm reaction known as the fight-or-flight response, described by Walter Cannon.
  • beta receptor - Our body cells contain either alpha or beta adrenaline receptors. When binding to beta receptors, adrenaline increases the cAMP concentration of cells; when binding to alpha receptors, it increases the calcium (Ca²⁺) concentration. Liver cells contain beta receptors. Adrenaline causes the release of glucose from the liver through increasing the cAMP concentration.
  • G protein - A protein that plays an important role in signal transduction pathways. Out of its 3 subunits, the alpha subunit can bind GTP and activate the target protein, which, in this case, is adenylate cyclase.
  • GDP - Guanosine diphosphate. Its structure is similar to that of ADP, but instead of adenine, it contains guanine.
  • GTP - Guanosine triphosphate. Its structure is similar to that of ATP, but instead of guanine, it contains adenine. Its binding activates the alpha subunit of the G protein.
  • adenylate cyclase - An enzyme protein that can synthesize cAMP (cyclic AMP) from ATP. cAMP is a second messenger important in many biological processes.
  • ATP
  • cAMP - Cyclic AMP. Important second messenger which, among other things, mediates the effect of adrenaline (first messenger, neurotransmitter) in the cell. It is synthesized from ATP by the cleavage of the 2 phosphate groups. Its only phosphate group binds to the 5th and 3rd carbon atoms of the ribose, thus forming a cyclic structure.
  • protein kinase A - Kinase enzymes are capable of phosphorylating other enzyme proteins, which influences their activity.
  • glycogen phosphorylase - Glycogen is a polymer of glucose molecules. Glycogen phosphorylase can convert it into glucose phosphate.
  • glycogen - Glycogen is a polymer of glucose molecules; it is one of the main forms of energy storage in the body besides fats. It is primarily found in the liver and in skeletal muscles. It can be converted into glucose quickly in order to increase blood glucose level and supply body cells with energy.
  • glucose phosphate
  • phosphatase - An enzyme protein that can convert glucose phosphate into glucose by removing the phosphate group from the molecule.
  • glucose - In stressful situations, blood glucose level rises. Cells produce the most ATP by breaking down glucose, therefore the rising blood glucose level covers the energy need of the fight-or-flight response.
  • glucose transporter - Glucose molecules cannot pass through the lipid membrane by themselves, their transport is facilitated by protein molecules.

Effect of beta blockers

  • heart muscle cell
  • adrenaline - It binds to the beta receptors of the heart muscle. It increases the activity of the heart muscle, its effect can be fatal in certain cases, for example after a heart attack. Its binding to receptors can be inhibited by beta blockers.
  • beta blocker - Inhibits the binding of adrenaline to beta receptors. In the heart, of the different types of beta receptors, the ß₁ type is typical. Certain beta blockers are selective ß₁ receptor inhibitors, thereby their effects are targeted at the heart. There are however non-selective beta blockers that affect all beta receptors found in the body.
  • beta receptor - When binding to it, adrenaline initiates a signal transduction pathway in the heart muscle cell. This increases the activity of the heart muscle. Beta blockers can inhibit the binding of adrenaline. In the heart, of the different types of beta receptors, the ß₁ type is typical.
  • heartbeat slows down

Animation

  • brain - Blood vessels of the brain dilate, therefore the flow of blood in the brain is increased.
  • heart - The heart muscle contracts stronger and with a higher frequency. The circulatory minute volume rises. Blood vessels of the heart dilate.
  • lungs - Bronchioles dilate, the respiratory minute volume increases.
  • eyes - The pupils dilate.
  • intestines - Blood vessels of the intestines constrict; blood flows into the skeletal muscles.
  • skin - The skin becomes pale as its blood vessels constrict; blood flows into the skeletal muscles.
  • kidneys - Blood vessels of the kidneys constrict, excretory processes slow down; blood flows into the skeletal muscles.
  • skeletal muscles - The blood flow of the skeletal muscles increases. Glycogen stored in the muscles is converted into glucose, thus the blood glucose level increases.
  • liver - The liver plays a central role in the storage of glycogen. Liver glycogen is converted into glucose, thus the blood glucose level increases.
  • smooth muscle cell
  • adrenaline - Also known as epinephrine, it is a stress hormone secreted by the medulla of the adrenal glands in response to the stimulation of the sympathetic nervous system. Its effect is practically the same as the effect of the sympathetic nervous system: it triggers the alarm reaction described by Walter Cannon, known as the fight-or-flight response.
  • alpha receptor - Our body cells contain either alpha or beta adrenaline receptors. When binding to alpha receptors, adrenaline increases the calcium (Ca²⁺) concentration; when binding to beta receptors, it increases the cAMP concentration. The smooth muscle cells of the intestines contain alpha receptors. Adrenaline causes the contraction of these blood vessels and thereby the decrease of blood flow of the intestines through increasing the Ca²⁺ concentration. Adrenaline has a similar effect on the blood vessels of the skin, this is why our skin turns pale in stressful situations.
  • G protein - A protein that plays an important role in signal transduction pathways. Out of its 3 subunits, the alpha subunit can bind GTP and activate the target protein, which, in this case, is phospholipase C.
  • GDP - Guanosine diphosphate. Its structure is similar to that of ADP, but instead of adenine, it contains guanine.
  • GTP - Guanosine triphosphate. Its structure is similar to that of ATP, but instead of guanine, it contains adenine. Its binding activates the alpha subunit of the G protein.
  • phospholipase C - An enzyme protein that cleaves the PIP2 molecule found in the cell membrane, thereby activating protein kinase C and causing the release of Ca²⁺. Therefore a metabolic change occurs in the smooth muscle cell, which contracts, causing the narrowing of the capillary.
  • activation of protein kinase C and release of Ca²⁺
  • smooth muscle cell contracts
  • vasoconstriction
  • smooth muscle cell
  • adrenaline - Also known as epinephrine, it is a stress hormone secreted by the medulla of the adrenal glands in response to the stimulation of the sympathetic nervous system. Its effect is practically the same as the effect of the sympathetic nervous system: it triggers the alarm reaction described by Walter Cannon, known as the fight-or-flight response.
  • beta receptor - Our body cells contain either alpha or beta adrenaline receptors. When binding to beta receptors, adrenaline increases the cAMP concentration of cells; when binding to alpha receptors, it increases the calcium (Ca²⁺) concentration. Smooth muscle cells of the blood vessels supplying skeletal muscles contain beta receptors. Adrenaline causes the dilation of these blood vessels and thereby the increase of blood flow in skeletal muscles through increasing the cAMP concentration.
  • G protein - A protein that plays an important role in signal transduction pathways. Out of its 3 subunits, the alpha subunit can bind GTP and activate the target protein, which, in this case, is adenylate cyclase.
  • GDP - Guanosine diphosphate. Its structure is similar to that of ADP, but instead of adenine, it contains guanine.
  • GTP - Guanosine triphosphate. Its structure is similar to that of ATP, but instead of guanine, it contains adenine. Its binding activates the alpha subunit of the G protein.
  • adenylate cyclase - An enzyme protein that can synthesize cAMP (cyclic AMP) from ATP. cAMP is a second messenger important in many biological processes.
  • ATP
  • smooth muscle cell relaxes
  • vasodilation
  • glucose release - In stressful situations, blood glucose level rises. Cells produce the most ATP by breaking down glucose, therefore the rising blood glucose level covers the energy need of the fight-or-flight response described by Walter Cannon.
  • adrenaline - Also known as epinephrine, it is a stress hormone secreted by the medulla of the adrenal glands in response to the stimulation of the sympathetic nervous system. Its effect is practically the same as the effect of the sympathetic nervous system: it triggers the alarm reaction known as the fight-or-flight response, described by Walter Cannon.
  • beta receptor - Our body cells contain either alpha or beta adrenaline receptors. When binding to beta receptors, adrenaline increases the cAMP concentration of cells; when binding to alpha receptors, it increases the calcium (Ca²⁺) concentration. Liver cells contain beta receptors. Adrenaline causes the release of glucose from the liver through increasing the cAMP concentration.
  • G protein - A protein that plays an important role in signal transduction pathways. Out of its 3 subunits, the alpha subunit can bind GTP and activate the target protein, which, in this case, is adenylate cyclase.
  • GDP - Guanosine diphosphate. Its structure is similar to that of ADP, but instead of adenine, it contains guanine.
  • GTP - Guanosine triphosphate. Its structure is similar to that of ATP, but instead of guanine, it contains adenine. Its binding activates the alpha subunit of the G protein.
  • adenylate cyclase - An enzyme protein that can synthesize cAMP (cyclic AMP) from ATP. cAMP is a second messenger important in many biological processes.
  • ATP
  • cAMP - Cyclic AMP. Important second messenger which, among other things, mediates the effect of adrenaline (first messenger, neurotransmitter) in the cell. It is synthesized from ATP by the cleavage of the 2 phosphate groups. Its only phosphate group binds to the 5th and 3rd carbon atoms of the ribose, thus forming a cyclic structure.
  • protein kinase A - Kinase enzymes are capable of phosphorylating other enzyme proteins, which influences their activity.
  • glycogen phosphorylase - Glycogen is a polymer of glucose molecules. Glycogen phosphorylase can convert it into glucose phosphate.
  • glycogen - Glycogen is a polymer of glucose molecules; it is one of the main forms of energy storage in the body besides fats. It is primarily found in the liver and in skeletal muscles. It can be converted into glucose quickly in order to increase blood glucose level and supply body cells with energy.
  • glucose phosphate
  • phosphatase - An enzyme protein that can convert glucose phosphate into glucose by removing the phosphate group from the molecule.
  • glucose - In stressful situations, blood glucose level rises. Cells produce the most ATP by breaking down glucose, therefore the rising blood glucose level covers the energy need of the fight-or-flight response.
  • glucose transporter - Glucose molecules cannot pass through the lipid membrane by themselves, their transport is facilitated by protein molecules.
  • heart muscle cell
  • adrenaline - It binds to the beta receptors of the heart muscle. It increases the activity of the heart muscle, its effect can be fatal in certain cases, for example after a heart attack. Its binding to receptors can be inhibited by beta blockers.
  • beta blocker - Inhibits the binding of adrenaline to beta receptors. In the heart, of the different types of beta receptors, the ß₁ type is typical. Certain beta blockers are selective ß₁ receptor inhibitors, thereby their effects are targeted at the heart. There are however non-selective beta blockers that affect all beta receptors found in the body.
  • beta receptor - When binding to it, adrenaline initiates a signal transduction pathway in the heart muscle cell. This increases the activity of the heart muscle. Beta blockers can inhibit the binding of adrenaline. In the heart, of the different types of beta receptors, the ß₁ type is typical.
  • heartbeat slows down

Narration

Human homeostasis, or the dynamic stability of the internal conditions of the body, can be threatened by a number of factors. In such a situation, a stress reaction is produced in response to the stimulation of the nervous system and the hormonal system. This reaction helps us to avoid danger and maintain homeostasis.
In a stressful situation, the sympathetic nervous system is activated, stimulating the release of a hormone called adrenaline, or epinephrine, by the adrenal medulla.
The combined effect of adrenaline and the sympathetic nervous system leads to a fight-or-flight reaction. The main symptoms of this include: the dilation of the pupils; an increase of the heart rate and of the circulatory minute volume; a release of glucose into the blood stream from the liver and skeletal muscles, causing the increase of blood glucose level; a dilation of the blood vessels in the brain and the heart; and a constriction of the blood vessels in the intestines, kidneys and skin.

The smooth muscle in the blood vessels found in different organs contains either alpha or beta adrenaline receptors. When binding to alpha receptors, adrenaline causes blood vessels to contract; while binding to beta receptors, it dilates blood vessels. The smooth muscle in our intestines, kidneys and skin typically contains alpha receptors. When the adrenaline is bound, the alpha receptor activates the G protein, which has three subunits. Its alpha subunit converts GDP into GTP, and then activates the phospholipase C enzyme. Phospholipase C breaks the PIP2, that is the phosphoinositol diphosphate molecule, into IP3 and DAG, that is, inositol triphosphate and diacylglycerol. IP3 causes the endoplasmic reticulum to release calcium ions, while DAG activates the protein kinase C enzyme. Calcium ions and protein kinase C have the joint effect of contracting smooth muscle cells, constricting blood vessels and decreasing the blood supply to the organs.

The smooth muscle in our heart, brain and blood vessels typically contains beta receptors. Thus the blood supply to these organs is increased during an alarm reaction. Adrenaline binds to the beta receptors in the smooth muscle cell of blood vessels. This activates the G protein: the alpha subunit replaces the GDP with a GTP and activates an enzyme called adenylate cyclase. This enzyme converts ATP into cyclic AMP, also known as cAMP. This results in the dilation of blood vessels and thereby the increase of the blood supply to the organ.
As adrenaline causes the contraction of certain blood vessels and the dilation of others, it basically sends blood to the skeletal muscles, the heart and the brain.

As an effect of adrenaline, the blood glucose level rises, thus providing energy for the muscles, the heart and the brain. Glucose is stored in a polymer form, as glycogen, primarily in the liver and the skeletal muscles. This is the quickest source of glucose in the body.
The beta receptors in liver cells bind adrenaline. Then the alpha subunit of the G protein activates the adenylate cyclase, which synthesizes cyclic AMP. cAMP activates the protein kinase A enzyme. This phosphorylates and thereby activates the glycogen phosphorylase enzyme, which catalyzes the release of glucose phosphates from glycogen. The phosphate groups in the glucose phosphate molecules are removed by an enzyme, and glucose is released into the blood.

The heart muscle contains a large amount of a subtype of the beta receptor, the beta-1 receptor. Since adrenaline stimulates the heart through this receptor, drugs known as beta blockers can be used to reduce the load on the heart. There are selective beta-1 blockers, but there are those that act on all types of beta receptors. The use of beta blockers may be necessary for disorders of the heart rate or high blood pressure, or after a heart attack, in order to relax the heart muscle.

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