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The Function of the Endocrine System - Coggle Diagram
The Function of the Endocrine System
Biological rhythms, like the sleep/wake cycle, are regulated by a balance between internal biological clocks (endogenous pacemakers) and external environmental cues (exogenous zeitgebers).
Endogenous Pacemakers:
Internal mechanisms within organisms that regulate rhythms independently of external factors.
Located in the hypothalamus, the SCN is the most important endogenous pacemaker.
Closely linked to the pineal gland and influential in maintaining the circadian sleep/wake cycle.
Role of SCN:
Controls various biological rhythms.
Receives information about light levels from the optic nerve, synchronizing circadian rhythm with the external environment.
Animal Studies on the SCN:
DeCoursey et al. (2000):
Method: Destroyed SCN connections in the brains of 30 chipmunks.
Observation: Chipmunks returned to natural habitat and observed for 80 days.
Findings: Sleep-wake cycle disappeared by study's end; significant proportion killed by predators, likely due to being awake when they should be asleep.
Martin Ralph et al. (1990):
Method: Bred mutant hamsters with a 20-hour wake-sleep cycle.
Observation: Fetal tissue of mutant hamsters replaced with brains of normal hamsters.
Findings: Cycle of second group defaulted to 20 hours.
Key Points:
Role of SCN: Demonstrated in establishing and maintaining the circadian sleep-wake cycle.
Importance: Animal studies highlight the significance of the SCN in regulating behavior and vulnerability to environmental factors like predation.
Pineal Gland:
Increases melatonin production during the night under the influence of the SCN.
Melatonin implicated in conditions like seasonal affective disorder
External cues such as light or social schedules that synchronize internal biological clocks with the external environment.
exogenous zeitgebers
Exogenous zeitgebers are extrernal factors that reset are biological clocks through a process known as entrainment. EG light, mealtimes, and social activities.
research support
Study by Campbell and Murphy (1998):
Objective: Investigate if light can be detected by skin receptor sites on the body, independent of eye reception.
Method:
15 participants woken at various times.
Light pads placed on the back of their knees instead of eyes.
Findings:
Participants' usual sleep-wake cycle deviated by up to three hours.
Light detected by skin receptors influenced sleep-wake patterns significantly.
Implications:
Suggests light is a potent exogenous zeitgeber, capable of affecting biological rhythms even without direct eye exposure.
This study underscores the powerful influence of light as an external cue on regulating the sleep-wake cycle, extending our understanding of how biological rhythms are synchronized with environmental cues.
evaulation
One significant difference lies in the genetic makeup and evolutionary history of animals compared to humans. While many molecular and cellular mechanisms may be conserved across species, there are also critical differences that can impact how these mechanisms function in distinct organisms. For example, while the suprachiasmatic nucleus (SCN) is a crucial regulator of circadian rhythms in both animals and humans, its precise functioning and response to stimuli may vary.
Ethical Concerns:
Reflection on the ethical costs and benefits of animal research, as seen in the DeCoursey study.
Complex Interaction:
Interplay between endogenous pacemakers and exogenous zeitgebers is intricate, affected by individual differences and environmental contexts.
Hormones are chemical substances that circulate in the bloodstream and only affect target organs
They are produced in large quantities and can be very powerful
They control ongoing internal functions and enable our bodies to react according to changes in the environment
Endocrine glands synthesise substances such as hormones and release them into the bloodstream
The Pituitary Gland:
Function: Often termed the 'master gland' for its control over hormone production and release from other endocrine glands.
Control by Hypothalamus:
The hypothalamus regulates the pituitary gland's activity.
Anterior Lobe:Releases adrenocortical trophic hormone (ACTH). Stimulates the adrenal cortex, prompting cortisol release.
Posterior Lobe:Releases oxytocin.Responsible for uterine contractions during childbirth.
Oxytocin's Role:Regulates emotional responses and pro-social behaviors.Influences trust, empathy, and bonding cues processing.
Pineal Gland
This releases melatonin which is responsible for important biological rhythms, including the sleep-wake cycle
It receives information from the environment about the light-dark cycle which influences the production and secretion of melatonin
Thyroid Gland
This plays a role in controlling heart, muscle and digestive function, brain development and bone maintenance
It releases thyroxine, which is responsible for regulating our metabolism through other organs like the liver and kidneys
Our metabolism is involved in chemical processes of converting food into energy
The Fight or Flight Response
During situations that induce stress, fear, or excitement, the neurons of the sympathetic nervous system activate the adrenal medulla within the adrenal gland to secrete adrenaline
Adrenaline, a hormone, readies the body for responding to stressful circumstances. This reaction is commonly referred to as the "fight or flight" response. The effects of adrenaline lead to typical symptoms experienced during stressful situations, such as increased heart rate, dry mouth, and heightened sweating.
Adrenaline, functioning as a hormone, is transported through the bloodstream and binds to receptors on target organs. One significant target is the sinoatrial node (SAN), increasing excitation frequency and subsequently elevating heart rate to supply blood to muscles at a faster rate
This increases the impulses travelling along the sympathetic neurones affecting the heart, further speeding up the heart rate
Blood vessels to less important organs (such as the digestive system and skin) constrict so that more blood can be diverted to organs that will be involved in the "fight or flight" response
The changes experienced by the body during the "fight or flight" response are controlled by a combination of nervous and hormonal responses.
This increased blood flow delivers more oxygen and glucose to muscle cells, enhancing aerobic respiration and energy release crucial for responding to stressful situations.
psychologists have developed and refined Cannon’s work, coming to a better understanding of how people react to threats.
Thus defining what is now called fight, flight, freeze:
Fight: facing any perceived threat aggressively.
Flight: running away from danger.
Freeze: unable to move or act against a threat.
Some psychologists suggest that men and women respond differently to social stress: men tend to exhibit a "fight or flight" response, while women display a "tend and befriend" reaction. Physiologist Walter Cannon proposed the universal "fight-or-flight" response to stress in the 1930s. Traditional gender roles often assigned women caregiving roles, fostering social connections and support systems. From an evolutionary perspective, prioritizing social bonds and nurturing behaviors could have been advantageous for survival. Therefore, women may have developed adaptive responses that emphasize social connection and support during times of stress.