Circadian Timing System

Circadian rhythms occur every 24 hours; an example of a circadian rhythm is the sleep-waking cycle. We are diurnal animals who are active during the daytime and asleep at night, other animals are nocturnal they are active at night but asleep during the day. The circadian rhythm depends on the interaction of physiological and psychological processes to be tuned into the sleep-waking cycle so energy is provided when needed. As diurnal humans we have a fairly stable sleep pattern with the time we go to sleep and the time we wake up, this consistency suggests an internal mechanism controls sleep, endogenous pacemaker. However, this can be overridden by external factors, exogenous zeitgebers.

Within the last century, and even merely in the past decade, incredible advancements in technology have allowed modern medicine to rapidly progress to extraordinary levels, leaving scientists with unprecedented understanding of the human body, and of the aging process especially. While the field of gerontology has flourished as a result and knowledge of physiological changes in the aging body increased, scientists still only have a some-what fundamental understanding of the normal aging brain, and even less of abnormal age-related changes in the brain.

Humans have a natural rhythm of 25 hours of sleep and wakefulness, in order to reset this the brain plays an important role with the suprachiasmatic nucleus which is a cluster of neurons in the medial hypothalamus of the brain. The SCN

McMahon , et al, 2014). Another factor that can play into S.A.D. is melatonin, which helps with sleep and wake cycles. Rosenthal, et al, notes how the pineal gland, the gland that produces melatonin, will react to dark surroundings with drowsiness that can lead people to being lethargic (as cited in Melrose, 2015). When melatonin increases and serotonin decreases, the offset of the proteins can cause circadian rhythms to be disrupted, which is the bodies “24 hour” clock. Researcher Melrose writes that “…circadian rhythms respond to the rhythmic light-dark changes that occur daily and throughout each of the seasons.” (2015). People with S.A.D. disorder normally find that their circadian rhythms are off beat and timed differently with day lengths, for example feeling tired in the middle of the day while being wide awake or feeling wide awake when it would normally be time to sleep.

Non-24-Hour Sleep-Wake Disorder, short for Non-24, is a chronic circadian rhythm disorder that affects people that are completely blind. The circadian rhythms control the body clock and regulate sleep-wake cycle and various other cycles that are critical in the body. In most people, this body clock runs marginally longer than 24 hours. This means that rather than cycle on a 24-hour day, most people’s natural rhythms actually run a bit longer. Whether the cycle runs two minutes or 30 minutes longer, patients with Non-24 have these minutes add up day after day, few days adding to a few more the next. Eventually causing evident changes in one’s body. Their body’s circadian rhythm becomes out of sync from regular day and night cycle.

The pineal gland also plays a key role in regulating animal circadian rhythms, which vary across species. Melatonin is synthesized from serotonin by N-acetyltransferase. In mammals, N-acetyltransferase activity is stimulated in the CNS by sympathetic nerves stemming from the superior cervical ganglion, whereas in birds, the N-acetyltransferase “control switch” appears to lie within the gland itself (Deguchi, 1979).

show several aging-dependent changes such as changes in anatomy and function in identified neurons [8], behavioral changes [9,10], expression of mRNAs [11], and neurotransmitter regulation [12]. (2) A simple and well-studied nervous system and behavioral repertoire to facilitate the study of neurological and behavioral correlates of aging at the level of single neurons and circuits. (3) Two learning assays (Sensitization and Habituation of the GWR) proposed in this study are well studied and show age dependent decline [9]. (4) Importantly, neural circuitry underlying GWR has been identified [5]. Neurons of Aplysia GWR offer several advantages. In contrast to Drosophila, C. elegans or mammalian neurons, those of Aplysia are gigantic, allowing relatively easy study of cell-specific changes during aging. Importantly the presynaptic sensory (LESN) and postsynaptic motor (L7MN) neurons of the GWR circuitry can be easily identified (Fig 1) and manipulated. Sensitization of GWR result in growth of new synaptic connections, whereas habituation induces retraction of synapses. Thus, the experimental system allows for precise measurements of electrophysiological, morphological and molecular changes to address the specific aims of this proposal. (5) As described in the “Significance” section it is important to recognize that many concepts that are central to our overall understanding of the LTM were established using Aplysia [5, 13-17;18-23]. Therefore it is expected that

Every individual has its own genetic coding which predetermines the process of ageing and the rate of this process. This biological clock own

The Monk and Buysse (2014) study looked at the interaction of an individual’s Morningness or Eveningness preference in relation to their sleep quality and duration. It had previously been established that sleep patterns progressively change upon aging (their chronotype) (i.e. their time to bed and time of awakening are both earlier). It would be interesting to apply the co-sleeping condition with specific nocturnal animals (e.g. cats or hamsters) to see if the animal’s nocturnal activities influence sleep quality and

The passage discusses how the body regulates its internal clock. Write an essay analyzing the importance of the body’s clock to people’s everyday life. Use evidence from the passage to support your response.

According to O’Brien, Isayama, Richardson, & Berson (2002), the ganglion cells also consist of over a dozen different subtypes of cells and the functionality of these subtypes rely greatly on the individual responses that are stimulated by light entering into the retinal synaptic network. Early studies on ganglion cells in a cat’s retina showed that there were three physiological responses reported in the cat’s ganglion cells and that these cells had both a central and peripheral district within the retina. It was noted that both of these areas produce opposite effects upon activity of the ganglion cells (Enroth-Cugell, Goldstick, & Linsenmeier.

3. Wintering over is a syndrome that 50% of the Antarctic inhabitants experience during the winter. This suggests that:

Circadian clocks are important to our bodies, most importantly for our sleep patterns. Everyone has their own outlooks on time change, but I like when time springs backwards. Even though the day goes by slower I still get an extra hour of sleep at night. I only like springing forward because the day ends quicker. For example, I feel like I am always sleep deprived. I work at Walmart, so I’m always getting off late at 10 P.M. By the time I get home, I take a shower, then study for 30 minutes to a 1 hour. By the time I’m done studying some nights I don’t always fall asleep very easily. Then there is some nights I don’t get the chance to study because, when I get home from work I sometimes have to be up early again at 7 A.M to work an 8 hour

The circadian clock holds large importance in a number of bodily functions including the cardiovascular system. In particular there are a number of connections between the circadian clock and myocardial infarctions (heart attacks). Myocardial infarctions (MIs) as a term is more commonly used in scientific journals than heart attacks, therefore, the term myocardial infarction (MI) will be used throughout the duration of this paper. Overall a discussion of the link between MIs and the circadian clock, the effect of disrupted sleep on MIs, and certain cases where there is an attenuation of the link between the circadian clock and MIs will be considered

Bipolar cells serve as a direct pathway linking the ganglion cells and the photoreceptors. There are many different types of bipolar cells, the most common being rod and cone, but all of the cells are either ON or OFF types. The cells can be distinguished by glutamate receptor expression, response to light and in their structural layout. Bipolar cells responds to light when initiated by the synapses of photoreceptors. The neurotransmitter released by these photoreceptors is glutamate. The bipolar cells respond in two different ways to this stimulus, ON which is glutamate hyperpolarization and OFF which is glutamate depolarization. Retinal bipolar cells have voltage gated channels that lie within their membranes and take part in the voltage responses. The most common types of ions that pass through these channels are calcium and potassium. The three primary types of receptors are kainate, AMPA and NMDA. The AMPA receptors select for transient components of the light signal while the kainate receptors conduct sustained characteristics of the signal. This paper will review what role bipolar cells play in the transduction pathway of a light stimulus to the retina and the