{"id":4773,"date":"2025-08-25T00:00:20","date_gmt":"2025-08-25T04:00:20","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/?post_type=chapter&#038;p=4773"},"modified":"2025-12-13T17:53:48","modified_gmt":"2025-12-13T22:53:48","slug":"factors-that-increase-heart-rate","status":"web-only","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/chapter\/factors-that-increase-heart-rate\/","title":{"raw":"7p5 Factors That Increase Heart Rate","rendered":"7p5 Factors That Increase Heart Rate"},"content":{"raw":"<strong>Overview:<\/strong>\r\n<ul>\r\n \t<li>Heart rate varies frequently in response to body needs and external stimuli.<\/li>\r\n \t<li>Several internal and external factors influence the <strong style=\"text-align: initial;font-size: 1em\">medulla oblongata<\/strong><span style=\"text-align: initial;font-size: 1em\">, the brain\u2019s cardiovascular control center to adjust <strong>heart rate<\/strong> by either:<\/span>\r\n<ul>\r\n \t<li><span style=\"text-align: initial;font-size: 1em\"> stimulating the <strong>SNS<\/strong> cardioaccelerator nerve which releases Epinephrine and Norepinephrine on the <strong>SA node<\/strong>, binding to beta-1 adrenergic receptors, opening Ca<sup>++<\/sup> channels, causing <strong>depolarization,<\/strong> bringing cardiomyocytes closer to threshold.<\/span><\/li>\r\n \t<li>stimulating the <strong>PSNS<\/strong> vagus nerve which releases Acetylcholine on the <strong>SA node<\/strong>, binding to muscarinic receptors, opening K+ channels, causing <strong>hyperpolarization,<\/strong> bringing cardiomyocytes further from threshold.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<h1><strong>Factors That Can Increase Heart Rate:<\/strong><\/h1>\r\n<h1><strong>1. Thyroid Hormone:<\/strong><\/h1>\r\n<ul>\r\n \t<li>Regulates\u00a0<strong>basal metabolic rate<\/strong>\u00a0(BMR).<\/li>\r\n \t<li>Increased thyroid hormone \u2192 higher BMR \u2192 increased heart rate.<\/li>\r\n \t<li>Conditions:\r\n<ul>\r\n \t<li><strong>Hyperthyroidism:<\/strong>\u00a0Excess thyroid hormone leads to faster heart rates.<\/li>\r\n \t<li><strong>Hypothyroidism:<\/strong>\u00a0Less thyroid hormone results in slower heart rate.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<h1><strong>2. Stress Response &amp; Temperature:<\/strong><\/h1>\r\n<ul>\r\n \t<li><strong>Biological Stressors:<\/strong> Exercise, Extreme heat or cold, Illness, or Emotional stress.<\/li>\r\n \t<li>\r\n<ul>\r\n \t<li>The body activates\u00a0<strong>fight or flight (Sympathetic Nervous System, SNS),<\/strong> increasing heart rate to deliver more oxygen and nutrients.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li><strong>Heat:<\/strong>\u00a0Blood vessels dilate for heat dissipation, requiring a faster heartbeat.<\/li>\r\n \t<li><strong>Cold:<\/strong>\u00a0The body may also increase heart rate to maintain core temperature.<\/li>\r\n<\/ul>\r\n<h1><strong>3. Physical Activity &amp; Exercise:<\/strong><\/h1>\r\n<ul>\r\n \t<li>During exertion:\r\n<ul>\r\n \t<li>The\u00a0<strong>cardiac accelerator nerve<\/strong>\u00a0releases\u00a0<strong>epinephrine<\/strong>\u00a0on\u00a0<strong>beta-1 adrenergic receptors<\/strong>\u00a0on the SA node.<\/li>\r\n \t<li>This speeds depolarization, increasing both\u00a0<strong>heart rate<\/strong>\u00a0and\u00a0<strong>force of contraction<\/strong>.<\/li>\r\n \t<li>Supports muscle activity by delivering oxygen-rich blood more rapidly.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<h1><strong>4. Smoking &amp; Nicotine Use:<\/strong><\/h1>\r\n<ul>\r\n \t<li><strong>Nicotine<\/strong>\u00a0stimulates release of\u00a0<strong>epinephrine<\/strong>.<\/li>\r\n \t<li>Results:\r\n<ul>\r\n \t<li>Increased\u00a0<strong>heart rate<\/strong>.<\/li>\r\n \t<li><strong>Vasoconstriction<\/strong>\u00a0and narrowing of blood vessels.<\/li>\r\n \t<li>Elevated blood pressure, making the heart work harder.<\/li>\r\n \t<li>Over time, can cause\u00a0<strong>heart deterioration<\/strong>.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<h1><strong>5. Carbon Monoxide Poisoning:<\/strong><\/h1>\r\n<ul>\r\n \t<li>Carbon Monoxide is a product of gas combustion (e.g., engine exhaust)<\/li>\r\n \t<li>Binds to hemoglobin, displacing oxygen.<\/li>\r\n \t<li>Causes\u00a0<strong>hypoxia<\/strong>.<\/li>\r\n \t<li>Chemoreceptors detect low oxygen, signaling the medulla to\u00a0<strong>increase heart rate<\/strong>\u00a0to compensate.<\/li>\r\n<\/ul>\r\n<h1><strong>6. Lung Conditions &amp; Tar:<\/strong><\/h1>\r\n<ul>\r\n \t<li>Tar buildup damages lung tissue, reducing\u00a0<strong>gas exchange surface area<\/strong>.<\/li>\r\n \t<li>Leads to\u00a0<strong>hypoxia<\/strong>, which triggers reflex mechanisms to speed up the heart.<\/li>\r\n \t<li>Pulmonary fibrosis and alveolar damage due to frequent lung infections or inhalation of damaging chemicals<\/li>\r\n<\/ul>\r\n<h1><strong>7. Pregnancy:<\/strong><\/h1>\r\n<ul>\r\n \t<li>Increases\u00a0<strong>metabolic rate<\/strong>\u00a0due to fetal growth and supporting physiological changes.<\/li>\r\n \t<li>Larger\u00a0<strong>ATP requirement<\/strong>\u00a0and oxygen demand.<\/li>\r\n \t<li>Heart rate increases to sustain the increased blood volume and metabolic activity.<\/li>\r\n<\/ul>\r\n<h1><strong>Summary:<\/strong><\/h1>\r\nMultiple factors\u2014<strong>hormonal, environmental, physiological,<\/strong> and<strong> pathological\u2014<\/strong>can influence <strong>heart rate<\/strong>. These responses aim to ensure <strong>adequate oxygen<\/strong> and <strong>nutrient delivery<\/strong> during stress, activity, or illness. Understanding these factors helps evaluate normal physiology and the body\u2019s adaptation to various stimuli.","rendered":"<p><strong>Overview:<\/strong><\/p>\n<ul>\n<li>Heart rate varies frequently in response to body needs and external stimuli.<\/li>\n<li>Several internal and external factors influence the <strong style=\"text-align: initial;font-size: 1em\">medulla oblongata<\/strong><span style=\"text-align: initial;font-size: 1em\">, the brain\u2019s cardiovascular control center to adjust <strong>heart rate<\/strong> by either:<\/span>\n<ul>\n<li><span style=\"text-align: initial;font-size: 1em\"> stimulating the <strong>SNS<\/strong> cardioaccelerator nerve which releases Epinephrine and Norepinephrine on the <strong>SA node<\/strong>, binding to beta-1 adrenergic receptors, opening Ca<sup>++<\/sup> channels, causing <strong>depolarization,<\/strong> bringing cardiomyocytes closer to threshold.<\/span><\/li>\n<li>stimulating the <strong>PSNS<\/strong> vagus nerve which releases Acetylcholine on the <strong>SA node<\/strong>, binding to muscarinic receptors, opening K+ channels, causing <strong>hyperpolarization,<\/strong> bringing cardiomyocytes further from threshold.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h1><strong>Factors That Can Increase Heart Rate:<\/strong><\/h1>\n<h1><strong>1. Thyroid Hormone:<\/strong><\/h1>\n<ul>\n<li>Regulates\u00a0<strong>basal metabolic rate<\/strong>\u00a0(BMR).<\/li>\n<li>Increased thyroid hormone \u2192 higher BMR \u2192 increased heart rate.<\/li>\n<li>Conditions:\n<ul>\n<li><strong>Hyperthyroidism:<\/strong>\u00a0Excess thyroid hormone leads to faster heart rates.<\/li>\n<li><strong>Hypothyroidism:<\/strong>\u00a0Less thyroid hormone results in slower heart rate.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h1><strong>2. Stress Response &amp; Temperature:<\/strong><\/h1>\n<ul>\n<li><strong>Biological Stressors:<\/strong> Exercise, Extreme heat or cold, Illness, or Emotional stress.<\/li>\n<li>\n<ul>\n<li>The body activates\u00a0<strong>fight or flight (Sympathetic Nervous System, SNS),<\/strong> increasing heart rate to deliver more oxygen and nutrients.<\/li>\n<\/ul>\n<\/li>\n<li><strong>Heat:<\/strong>\u00a0Blood vessels dilate for heat dissipation, requiring a faster heartbeat.<\/li>\n<li><strong>Cold:<\/strong>\u00a0The body may also increase heart rate to maintain core temperature.<\/li>\n<\/ul>\n<h1><strong>3. Physical Activity &amp; Exercise:<\/strong><\/h1>\n<ul>\n<li>During exertion:\n<ul>\n<li>The\u00a0<strong>cardiac accelerator nerve<\/strong>\u00a0releases\u00a0<strong>epinephrine<\/strong>\u00a0on\u00a0<strong>beta-1 adrenergic receptors<\/strong>\u00a0on the SA node.<\/li>\n<li>This speeds depolarization, increasing both\u00a0<strong>heart rate<\/strong>\u00a0and\u00a0<strong>force of contraction<\/strong>.<\/li>\n<li>Supports muscle activity by delivering oxygen-rich blood more rapidly.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h1><strong>4. Smoking &amp; Nicotine Use:<\/strong><\/h1>\n<ul>\n<li><strong>Nicotine<\/strong>\u00a0stimulates release of\u00a0<strong>epinephrine<\/strong>.<\/li>\n<li>Results:\n<ul>\n<li>Increased\u00a0<strong>heart rate<\/strong>.<\/li>\n<li><strong>Vasoconstriction<\/strong>\u00a0and narrowing of blood vessels.<\/li>\n<li>Elevated blood pressure, making the heart work harder.<\/li>\n<li>Over time, can cause\u00a0<strong>heart deterioration<\/strong>.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h1><strong>5. Carbon Monoxide Poisoning:<\/strong><\/h1>\n<ul>\n<li>Carbon Monoxide is a product of gas combustion (e.g., engine exhaust)<\/li>\n<li>Binds to hemoglobin, displacing oxygen.<\/li>\n<li>Causes\u00a0<strong>hypoxia<\/strong>.<\/li>\n<li>Chemoreceptors detect low oxygen, signaling the medulla to\u00a0<strong>increase heart rate<\/strong>\u00a0to compensate.<\/li>\n<\/ul>\n<h1><strong>6. Lung Conditions &amp; Tar:<\/strong><\/h1>\n<ul>\n<li>Tar buildup damages lung tissue, reducing\u00a0<strong>gas exchange surface area<\/strong>.<\/li>\n<li>Leads to\u00a0<strong>hypoxia<\/strong>, which triggers reflex mechanisms to speed up the heart.<\/li>\n<li>Pulmonary fibrosis and alveolar damage due to frequent lung infections or inhalation of damaging chemicals<\/li>\n<\/ul>\n<h1><strong>7. Pregnancy:<\/strong><\/h1>\n<ul>\n<li>Increases\u00a0<strong>metabolic rate<\/strong>\u00a0due to fetal growth and supporting physiological changes.<\/li>\n<li>Larger\u00a0<strong>ATP requirement<\/strong>\u00a0and oxygen demand.<\/li>\n<li>Heart rate increases to sustain the increased blood volume and metabolic activity.<\/li>\n<\/ul>\n<h1><strong>Summary:<\/strong><\/h1>\n<p>Multiple factors\u2014<strong>hormonal, environmental, physiological,<\/strong> and<strong> pathological\u2014<\/strong>can influence <strong>heart rate<\/strong>. These responses aim to ensure <strong>adequate oxygen<\/strong> and <strong>nutrient delivery<\/strong> during stress, activity, or illness. Understanding these factors helps evaluate normal physiology and the body\u2019s adaptation to various stimuli.<\/p>\n","protected":false},"author":1370,"menu_order":11,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["zoe-soon"],"pb_section_license":"cc-by-nc-sa"},"chapter-type":[],"contributor":[60],"license":[57],"class_list":["post-4773","chapter","type-chapter","status-web-only","hentry","contributor-zoe-soon","license-cc-by-nc-sa"],"part":55,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/4773","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/users\/1370"}],"version-history":[{"count":9,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/4773\/revisions"}],"predecessor-version":[{"id":5282,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/4773\/revisions\/5282"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/parts\/55"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/4773\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/media?parent=4773"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapter-type?post=4773"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/contributor?post=4773"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/license?post=4773"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}