title: The beat goes on: Cardiac pacemaking in extreme conditions.
abstract: In order for an animal to survive, the heart beat must go on in all environmental conditions, or at least restart its beat. This review is about maintaining a rhythmic heartbeat under the extreme conditions of anoxia (or very severe hypoxia) and high temperatures. It starts by considering the primitive versions of the protein channels that are responsible for initiating the heartbeat, HCN channels, divulging recent findings from the ancestral craniate, the Pacific hagfish (Eptatretus stoutii). It then explores how a heartbeat can maintain a rhythm, albeit slower, for hours without any oxygen, and sometimes without autonomic innervation. It closes with a discussion of recent work on fishes, where the cardiac rhythm can become arrhythmic when a fish experiences extreme heat.
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada. Electronic address: chris7_77@hotmail.com.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Wilson
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
authors.forename: Georgina K
authors.initials: GK
authors.lastname: Cox
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada; Faculty of Land & Food Systems, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Farrell
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000235:genetics / Q000502:physiology; D019143:Evolution, Molecular; D029941:Fish Proteins / Q000235:genetics / Q000502:physiology; D006196:Hagfishes / Q000235:genetics / Q000502:physiology*; D006339:Heart Rate / Q000235:genetics / Q000502:physiology*; D006358:Hot Temperature / Q000009:adverse effects; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / Q000235:genetics / Q000502:physiology; D000860:Hypoxia / Q000503:physiopathology; D008955:Models, Cardiovascular; D010802:Phylogeny
chemical_list: D029941:Fish Proteins; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels
keywords: Anoxia; Carp; HCN; Hagfish; Heart rate; Hypoxia; Salmon; Temperature; Turtle