Sight Search

How the dive Reflex protects the brain and heart

What is the mammalian dive reflex?

The mammalian diving response, or "dive reflex," is the way our body automatically prioritizes blood delivery to the brain and heart when we hold our breath underwater. When your head is underwater, you are using up the oxygen in your blood and not replacing it by breathing, a condition known as hypoxia. The brain and the heart are exceptionally sensitive to hypoxia, whereas other parts of our body, such as our arms and our legs, can tolerate hypoxia much more easily.

Immersing your face in cold water triggers the trigeminal nerve (also called the fifth cranial nerve) in your face and sends signals to the brain. The brain then activates the vagus nerve (or 10th cranial nerve), which is part of the autonomic nervous system. The autonomic nervous system helps control things such as our heart rate and breathing without us having to think about it. The vagus nerve slows down the rate at which our heart beats; when it beats more slowly, it doesn't need as much oxygen to function.

Simply being immersed in water creates a hydrostatic pressure effect on the body that essentially squeezes some of the blood from our extremities back toward our heart. The vagus nerve also causes certain blood vessels to constrict (called vasoconstriction), subsequently pushing even more blood from our extremities back toward our heart and brain. Immersion of your face in cold water or breath holding can cause these effects, but they are much more pronounced if you hold your breath while also immersing your face in cold water.

Interestingly, there is also a response by our spleen to breath holding underwater. Red blood cells carry oxygen in our blood to our tissues. Extra red blood cells are stored in the spleen and can be added into the blood circulation during times of stress — such as hypoxia, bleeding and strenuous exercise — by the action of splenic contracture. Extra red blood cells allow more oxygen to be carried to where we need it. Some populations of indigenous breath-hold divers, such as the Bajau of Southeast Asia, have developed larger spleens and thus a larger reservoir of red blood cells and better tolerance to hypoxia. Conversely, we don't see this effect in people who have had their spleen removed.

All diving mammals experience these dive reflexes, although in humans it is less intense than in diving animals. Elephant seals, for example, can dive to more than 5,000 feet holding their breath and during migration can spend more than 80 percent of the time underwater. Researchers tracked an elephant seal that breath held to more than 4,000 feet for two hours.

Whether you fall into the water by accident or you are holding your breath for competition, your brain and heart need oxygen. While we may not be as adept as the elephant seals, you can see how the dive reflex helps to ensure our brain and heart get the oxygen they need when we hold our breath underwater.
— Kaighley Brett, M.D.

Categories

 2020
 2019
 2018
 2016
immersion and bubble formation Accidents Acid reflux Acute ailments After anaesthesia Air Quality Air exchange centre Air hose failure Airway control Air Alert Diver Magazine Alternative gas mix Altitude changes Altitude sickness Aluminium Oxide Ama divers Amino acids Anaerobic Metabolism Annual renewal Apnea Apnoea Archaeology Arterial gas embolism Arthroscopic surgery Aspirin Aurel hygiene BCD BHP BLS BWARF Back adjustment Back pain Back treatment Backextensors Badages Bag valve mask Bahamas Balancing Bandaids Barbell back squat Barometric pressure Barotrauma Basic Life Support Batteries Bench press Benign prostate hyperplasia Beth Neale Black Blood flow Blood thinners Blue Wilderness Blurred vision Boat safety Bone fractures Bouyancy compensators Boyle's Law Boyle\'s Law Bradycardia Brain Breast Cancer Breath Hold Diving Breath holding Breath hold Breath-hold Breathing Gas Breathing gas contamination Breathing Breathold diving Broken bones Bruising Bubbleformation Buddy Exercise Buddy checks Buoyancy Burnshield CGASA CMAS CO2 COVID-19 COVID CPR Cabin pressure Caissons diseas Camera settings Cancer Remission Cancer treatments Cancer Cannabis and diving Cannabis Cape Town Dive Festival Cape Town CapeTown Carbon Monoxide Carbon dioxide Cardio health Cardiological Cardiomyopathy Chamber Safety Chamber science Charging batteries Charles' Law Charles\' Law Charles\\\' Law Charles\\\\\\\' Law Charles\\\\\\\\\\\\\\\' Law Charlie Warland Chemotherapy Chest compressions Chiropractic Chlorophll Citizen Conservation Cleaning products Coastalexcursion Cold Water Cold care ColdWater Cold Commercial diving Commercial schools Compressed Air Compressed gas Consercation Conservation Contaminants Contaminated air Coral Conservation Coral Reefs Coral bleaching Corals Core strength Corona virus Courtactions Crohns disease Crowns Crystal build up Crystallizing hoses Cutaneous decompression DAN Courses DAN Profile DAN Researchers DAN medics DAN members DAN report DCI DCS Decompressions sickness DCS theories DCS DEMP DM training DNA DReams Dalton's Law Dalton\'s Law Dalton\\\'s Law Dalton\\\\\\\'s Law Dalton\\\\\\\\\\\\\\\'s Law Danel Wenzel Dauin island Dean's Blue Hole Deco dives Decompression Illness Decompression Sickness Decompression Stress Decompression illsnes Decompression treatment Decompression Deep diving Deep water exploration Delayed Offgassing Dental Diaphragms Diseases Dive Chamber Dive Computer Dive Destinations Dive H Dive Industry Dive Instruction Dive Instructor Dive Medical Form Dive Medical Dive Pros Dive Research Dive South Africa Dive Training Dive Travel Dive accidents Dive buddies Dive computers Dive excursions Dive fitness Dive gear Dive heallth Dive health Dive medicines Dive medicine Dive operators Dive planning Dive safety Dive safe Dive staff DiveLIVE Diveleader training Diveleaders Diver Health Diver Profile Diver infliencers Diver on surface Divers Alert Diving Divas Diving Kids Diving Trauma Diving career Diving emergencies Diving emergency management Diving fit Diving guidelines Diving injuries Diving suspended Diving Dizziness Dolphins Domestic Donation Dowels Dr Rob Schneider Drysuit diving Drysuit valves Drysuits Dyperbaric medicines EAPs EAP Ear pressure Ear wax Ears injuries Eco friendly Education Electronic Emergency action planning Emergency decompression Emergency plans Emergency underwater Oxygen Recompression Emergency Enviromental Protection Environmental factors Environmental impact Environmental managment Equalisation Equipment care Evacuations Evacuation Evaluations Even Breath Exercise Exhaustion Extended divetime Extinguisher Extreme treatments Eye injuries FAQ Factor V Leiden Failures Fatigue Faulty equipment Female divers Fillings Fire Coral Fire Safety Firefighting First Aid Equipment First Aid Kit First Aid Training First Aid kits Fish Identification Fish Fitness Training Fitness to dive Fitness Flying Fractures Francois Burman Fredive Free Student cover Free diving Free flow Freedive INstructor Freedive Training Freediver Freediving performance Freediving Gas Density Gas consumption Gas laws Gas mixes GasPerformance Gases Gastoeusophagus Gastric bypass Gastroenterologist Gear Servicing Gordon Hiles Great White Sharks Gutt irritations HCV HELP HIRA HMS Britanica Haemorhoid treatment Hazard Description Hazardous Marine life Hazardous marinelife Health practitioner Heart Attack Heart Health Heart Rate monitor Heart rates Heart rate Heart Heat stress Helium Hepatitis C Hepatitus B High temperatures Hip strength Hip surgery Hippocampus History Hot Humans Hydrate Hydration Hydrogen Hydroids Hydrostatic pressure Hyperbaric Chamber Hyperbaric research Hyperbarics Hypothermia Hypoxia IdentiFin Immersion Immine systems In Water Recompression Indemnity form Indian Ocean Indonesia Inert gas Infections Infra red Imaging Injections Instinct Instruction Instructors Insurance Integrated Physiology International travel International Interval training Irritation Joint pain Junior Open Water Diver KZN South Coast Kidneys Kids scubadiver KwaZulu Natal Labour laws Laryngospasm Lauren Arthur Learning to dive Legal advice Legislation Leukemis Liability Risks Liability releases Liability Life expectancy Lifestyle Lightroom editing Live aboard diving Liver Toxicity Liver diseas Low blood pressure Low pressure deterioration Low volume masks Lung Irritation Lung function Lung injuries Lung squeeze Lung surgery Lung MOD Maintenance Malaria Mammalian Dive Response Mammalian effect Marine Biology Marine Scientists Marine conservation Marine parks Marinelife Masks Master scuba diver Maximum operating depth Medical Q Medical emergencies Medical questionaire Medical statement Medication Mehgan Heaney-Grier Mermaid Danii Mesophotic Middle ear pressure Mike Bartick Military front press Mixed Gas Mono Fins Mooring lines More pressure Motion sickness Mozambique Muscle pain Mycobacterium marinum Nausea Nautilus Neck pain Neurological assessments Nitrogen Narcosis Nitrogen build up Nitrox No-decompression Non-rebreather Mask Normal Air Nosebleeds O2 providers O2 servicing OOxygen maintenance Ocean Research Ocean pollution Oil contamination Open water divers Orbital implants Oronasal mask Osteonecrosis Out and about Outreach Oxygen Cylinder Oxygen Units Oxygen deficit Oxygen deicit Oxygen dificiency Oxygen ears Oxygen equipment Oxygen masks Oxygen supply Oxygen therapy Oxygen P J Prinsloo PFI PJP Tech Part 3 Partner Training Philippine Islands Philippines Phillipines Photography Physioball Physiology Physiotherapy Pills Pistons Planning Plastic Pneumonia Pneumothorax Poison Pollution Pool Diving Post-dive Pre-dive Predive check Preparation Prepared diver Press Release Professional rights Provider course Psycological Pulmanologist Pulmonary Bleb Pulmonary Edema Pulse Punture wounds Pure Apnea Purge RAID South Africa RCAP REEF Radio communications Range of motion Rashes Rebreather diving Rechargeable batteries. Recompression chamber Recompression treatment Recompression Recycle Reef Conservation Reef surveyors Regulator failure Regulators Regulator Remote areas Renewable Report incidents Rescue Procedure Rescue breathing Rescue breaths Rescue training Rescue Resume diving Return to diving Risk Assessments Risk assesments Risk assessment Risk elements Risk management SABS 019 SafariLive Safety Stop Safety SaherSafe Barrier Salty Wanderer Sanitising Sara Andreotti Saturation Diving Save our seas Science Scombroid Poisoning Scuba Air Quality Scuba Injury Scuba Instructor Scuba children Scuba dive Scuba health Scubalearners Sea Horses Sealife Shark Protection Shark Research Shark conservation Shark diving Sharks Shoulder strength Sideplank Signs and Symptoms Sit-ups Skin Bends Skin outbreak Skin rash Snorkeling Snorkels Social Distancing Sodwana Bay Solomon Islands South Africa Spinal pain Splits Squeezes Stability exercise Standars Stay Fit Stents Step ups Stepping up Stroke Submerged Sudafed Sulawesi Supplemental oxygen Surface supplied Air Surfaced Surgeries Surgery Suspension training TRavel safety Tabata protocol Talya Davidoff Tattoes Technical Diving The Bends The truth Thermal Notions Tides Tips and trick Tooth squeeze Transplants Travel smarter Travel tips Travel Tropical Coastal Management Tunnelling Tweezers Ultrsound Umkomaas Unconsciousness Underground work Underwater hockey Underwater photographer Underwater photography Underwater pho University of Stellenbosch Urinary retention. Vaccines Vagus nerve Valsalva manoeuvers Vape Vaping Vasopressors Vasvagal Syncope Venting Virus infections Volatile fuels Washout treatments Wastewater Watchman device Water Resistance Water Weakness Weigang Xu Weights West Papua Wet diving bell Wetsuit fitting Wetsuits White balance Wide angles Winter Woman in diving Woman Women In Diving SA Women in diving Work of Breathing Workout Wound dressings Wreck divers Wreck dive Wreckdiving Wrecks Yoga Youth diver Zandile Ndholvu Zoology abrasion acoustic neuroma excision air-cushioned alert diver altitude anemia antibiotics anticoagulants antiseptics bandages barodontalgia bent-over barbell rows bioassays body art breathing air calories burn carbon dioxide toxicity cardiovascular cerebrospinal fluid checklist chemo port child clearances closed circuit scuba currents cuts dead lift decompression algorithms decongestants decongestion dehydration dive injuries dive medicing dive ready child dive reflex dive tribe diver in distress diver rescue diver training dive diving attraction doctors domestic travel dri-suits drowning dry mucous membranes dry suits dry e-cigarettes ear spaces elearning electrolyte imbalance electroytes emergency action plans emergency assessment equalising equalizing exposure injuries eyes fEMAL DIVERS fire rescue fitnes flexible tubing frediving freedivers gas bubble gas poisoning gastric acid gene expression health heartburn histidine hospital humidity immersion and bubble formation immersion pulmonary edema (IPE jaundice join DAN knee longevity lower stress malaise marine pathogens medical issues medical procedures medical risk assesment medications mental challenge micro-organisims minor illness mucous membranes nasal steroids nasal near drowning nematocysts neurological newdivers nitrogen bubbles off-gassed operating theatre operations orthopeadic outgas pain perforation phillippines physical challenges pinched nerves plasters polyester-TPU polyether-TPU post dive posture preserve prevention psychoactive pulmunary barotrauma rebreather mask rebreathers retinal detachment risk areas safety stops saturation scissors scuba equipment scuba single use sinus infections smoking snorkeling. spearfishing sterilising stings strength sub-aquatic swimmers ears tattoo care tecnical diver thermal protection toxicity training trimix unified standards vision impaired warmers water quality