BIO254:Pacemaker

Due Date: 11/20

A pacemaker is a biological oscillator (biological clock, biological timer) that directs one or more periodic biological processes or functions. The field of biology that studies pacemakers is chronobiology.

Range of periods

The periods of pacemakers range from sub-microsecond in the electric organ of eels (Moortgat, 1998), to 24 hours in the circadian rhythm, to 1 month in the menstrual cycle, to 12 months in hybernation, and even longer. For example the progression from sexual immaturity to reproductive competence to menopause in women can be considered a single cycle of a biological clock.

Mechanisms

Pacemakers use various mechanisms to keep track of time, and control many different biological functions. Here we will focus on pacemakers involved in the nervous system.

and functions of neurobiological pacemakers=

Oscillatory processes that underlie sensory coding, attention, memory and sleep (Fontanini, 2006).

 Biological pacemakers drive many time-dependent processes in organisms, including heart rate, cell division in embryogenesis, and circadian activities.  

Artificial pacemakers

Artificial pacemakers are used to rescue patients with deficient pacemakers, for example when the sinus node of the heart does not function correctly. Genetically engineered pacemakers may begin to replace microelectronic pacemakers (Boink, 2006).

Biological pacemakers can be in a single cell, but typically involve many cells. The periods of biological pacemakers span a large range.

References

Boink GJ, Seppen J, de Bakker JM, Tan HL (2006) .Gene therapy to create biological pacemakers.Med Biol Eng Comput. Oct 18; [Epub ahead of print]

Fontanini A, Bower JM.Slow-waves in the olfactory system: an olfactory perspective on cortical rhythms.Trends Neurosci. 2006 Aug;29(8):429-37. Epub 2006 Jul 13.

Moortgat KT, Clifford H. Keller§, Theodore H. Bullock, and Terrence J. Sejnowski (1998) Submicrosecond pacemaker precision is behaviorally modulated: The gymnotiform electromotor pathway. PNAS Vol. 95, Issue 8, 4684-4689.

Heterotrimeric G proteins

Heterotrimeric G proteins are comprised of three subunits -- α, β and γ -- that exist as a complex (G_αβγ) in the GDP-bound state but dissociate (into G_α and G_βγ) upon the release of GDP and binding of GTP. G_α contains the GDP/GTP binding site and GTPase activity (Fig. 1). The C-terminus of G_α gives the G protein affinity for specific membrane-bound GPCRs (see below).

Figure 1. Image from (Milligan, 2006). Some parts have been removed for clarity. GDP is shown in purple. The α subunit C-terminus residues, shown in blue, convey GPCR specificity. The N-terminus helix, shown in red, is required for binding of G_αto the other subunits.

A pacemaker (in the context of NBIO 254) is a biological clock, or in other words a rhythm generator in an organism.

Recent updates to the site:

List of abbreviations:

N

This edit created a new page (also see list of new pages)

m

This is a minor edit

b

This edit was performed by a bot

(±123)

The page size changed by this number of bytes

26 April 2024

05:25

Ernesto-Perez-Rueda:Contact‎ diffhist −94‎ Ernesto Perez-Rueda talk contribs

25 April 2024