biopsychology

the functions of the nervous sysstem are:

• to collect, process and respond to information in the environment 
• to co-ordinate different organs and cells within the body 

the nervous system is divided into the central nervous system and the peripheral nervous system

the main functions of the CNS is to control behaviour and to regulate the body's physiological processes.

THE BRAIN

centre of all conscious awareness and is divided into four main areas: the cerebrum, cerebellum, diencephalon and the brain stem 

THE SPINAL CORD 

main function is to relay information from the brain to the rest of the body. the spinal cord connects to muscles and glands by spinal nerves and is responsible for reflex actions 

contains all nerve cells outside of the CNS and it relays information from the brain and spinal cord to the rest of the body and then back to the CNS

SOMATIC NERVOUS SYSTEM (SNS)

contains skeletal muscles and connects the nervous system to the senses, is under conscious control and therefore involves voluntary movements, operates in the motor cortex in the brain, contains motor and sensory neurons

AUTONOMIC NERVOUS SYSTEM (ANS)

controls internl organs and glands and their important functions, invoulntary system, its divided into two parts (sympathetic and parasympathetic), contains only motor nerurons, operates from the brain stem

primarily involved in responses that help us to deal with emergencies (fight or flight). the main neurotransmitter is adrenaline

things the sympathetic nervous system does:

• dilates pupils 
• inhibits salivation 
• relaxes bronchi 
• accelerates heart
• inhibits digestive activity 
• relaxes bladder
• contracts rectum 
• stimulates glucose release by liver 

relaxes and slows the body down after an emergency, its known as 'rest and digest'. the main chemical involved in this system is acetylcholine

things the PNS does:

• constricts pupils 
• stimulates salivation 
• inhibits heart 
• constricts bronchi
• stimulates digestive activity 
• stimulates gallbladder 
• contracts bladder
• relaxes rectum

• when faced with a treat, the autonomic nervous system activates the sympathetic state of arousal 
• the sympathetic system stimulates the release of adrenaline from the adrenal medulla in adrenal glands into the bloodstream 
• adrenaline has direct effects on the body
• this increased blood flow prepares the body for physical action and increased the supply of oxygen to brain for rapid response plaiing 
• once the threat has passed, the parasympathetic system is re-activated and reduces the heightened activity of the body 

carry information from the senses to the CNS, they have long dendrites and short axons 

allow nerve impulses to be sent between sensory and motot neurons. short axons and dendrites

take information from the brain and spinal cord to muscles and glands around the body, responsible for controlling muscle movement and the strength of the movement, short dendrites and long axons

• a neuron is activated and the inside of the cell becomes positivly charged. an electrical impulse (action potential) is sent down the axon to the presynaptic terminal 
• the electrical impulse triggers the release of neurotransmitters from sacs called synatic vesicles into the synaptic gap
• neurotransmitters bind to special recpetors on the postsynaptic neuron. different neurotransmitters bind to different receptors 
• once the receptors are activated the signal is converted back into an electrical impulse and the process of transmission occurs again in the next neuron 
• stimulation of receptors can result in either excitation or inhibition 

excitation - neurotransmitter increases the positive chrage of the postsynaptic neuron, increasing the likelihood the neruon will fire and pass on the elctrical impulse 

inhibition - neurotransmitter increased the negative charge of the postsynaptic neuron, decreasing the likelihood the neuron will fire and pass on the electrical impulse 

network of glands that manufacture and release chemical messengers called horones. the function of this system is:

• regulate cell/organ activity within the body and to control vital physiological processes
• release hormones from glands into the bloodstream 

pituitary gland

called the master gland and found in the brain, causes other glands to release a range of hormones within the body and releases a number of hormones itself including FSH

the adrenal glands

responsible for releasing adrenaline and therefore controlling the SNS

the thyroid gland

produces thyroxine which affects cells in the heart and throughout the body increasing metabolic rates and heart rate, associated with growth

pancreas 

secretes insulin and glucagon which regulate blood sugar levels 

biological cycles which last around 24 hrs

the sleep/wake cycle 

dictates when we should be sleeping and when we should be awake, its influenced by endogenous pacemakers and our internal circadian 'clock' which is suggested to be free running. its also influenced by exogenous zeitgebers

regulation of temperature 

Siffre supports the sleep/wake cycle as he spent serveral extended periods underground to study his own biological rhythms. he found that he maintained a consistent sleep/wake cycle which supoorts this is a naturally occuring circadian rhythm

Aschoff and Wever conducted a study where ps spent 4 weeks in a WWII bunker deprived of natural light. all but one ps displayed a circadian rhythm which lasted between 24-25 hrs. thus suggests that the sleep/wake cycle is a free running circadian rhyth, but there may be some individual differences 

have positive real world applications 

knowledge of circadian rhythms has led to suggestions being made about how to maximise the productivity of shift workers and reduce any negative health effects. for example, Boivin found that accidents are more likely to hapen around 6am when there is a 'circadian trough' and a lack of concentration. 

can increase the effectiveness of drug treatments 

research into circadian rhythms has found how well drugs are absorbed and distributed in the body. therefore, guidelines have been developed which suggest the best times for certain drugs to be administered 

individual differences in circadian rhythms 

not all individuals follow circadian rhythms on a 24 hr cycle and there are differences within the sleep/wake patterns between individuals. for example, Duffy found differences betwwen people she called owls and larks and some research has established that younger individuals including teenagers may follow a different circadian rhythm to adults

these refer to internal processes that regulate our biological rhythms and form our 'internal body clock'. there are a number of pacemakers that influence our sleep/wake cycle

the suprachiasmatic nucleus (SCN)

this is a tiny bundle of nerve cells located in the hypothalamus and is an influential pacemaker in the sleep/wake cycle. it acts as a master clock. the SCN has a 'built-in' circadian rhythm which only needs resetting when extenal lights levels change. the SCN also regulates the manufacture and secretion of melatonin in the pineal gland via an interconnecting neural pathway 

the pineal gland and the role of melatonin

the SCN passes information on day length and light to the pineal gland which is a pea-like structure located behind the hypothalamus. during the night, this gland produces melatonin which encourages sleep by inhibiting the brain mechanisms which promote wakefulness

DeCoursey demonstrated the importance of the SCN in chipmunks. she founf that those who had their SCN connections destroyed had no identifiable sleep/wake cycle and by the end of the 80 day observation many had been killed by predators. this supports that the SCN is a key endogenous pacemaker which regulates the sleep/wake cycle 

Ralph bred a group of 'mutant' hamster who were programmed to have a 20 hr sleep/wake cycle. the hamsters adopted a 20 hr sleep/wake cycle supporting the role of the SCN as an endogenous pacemaker 

light 

• light is a key zeitgeber in humans as it can reset the body's main endogenous pacemaker (SCN) and therefore plays a significant role in the sleep/wake cycle. light resets the internal biological clock everyday and there is one special light detecting cell in the retina that gauges overall brightness to help reset the internal biological clock. a protein called melanopsin is critical in this system. a small number of retinal cells contain melanopsin and carry signals to the SCN to set the dailt body cycle 
• Burgess et al aimed to see if jet lag could be reduced through ecposure to light. ps exposed to 3 days of bright light in the morning before a west-east flight shifted their circadian rhythm by 2.1 hrs. this suggests that exogenous zeitgerbers play an important tole in regulating the sleep/wake cycle

• Campbell and Murphy conducted research to see if light can be detected by skin receptors and not just the eyes. 15 ps were woken at various times and a light was shone on the back of their knees. they found in some cases this alterted the sleep/wake cycle by up to 3 hrs

exogenous zeitgebers are environmental cues that can affect our biological rhythms and especially the sleep/wake cycle. these include light and social cues

social cues 

• social cues such as eating or taking part in social activities may also have a role as zeitgebers.foe example, the times at which people eat and interact with others can play a role in adjusting their sleep/wake cycle
• however, some research has suggested that social cues may not be an important exogenous zeitgeber. for example, Lughton-Miles report the case of a blind man who was ecposed to social cues in everyday society but who still displayed a sleep/wake cycle that lasted longer than 24hrs. this suggests that light might have a greater infleunce on the sleep/wake cycle than social cues 

infradian rhythms are those in which a cycle occurs less frequently than every 24 hrs. they may be cycles lasting days, weeks or months.

the female menstrual cycle 

the female reproductive cycle takes on average 28 days and is mainly regulated internally by hormomes such as oestrogen and progesterone.

seasonal affective disorder

SAD occurs on a yearly cycle, its a depressive disorder which shares many common symptoms of depression and the symptoms tend to be triggered by the onset of winter. this is suggested to be a disorder which is heavily influenced by the exogenous zeitgeber of light.

other evidence suggests that the menstrual cycle may not only be affected by endogenous hormones but could also be influenced by exogenous zeitgebers 

• Russel et al had 2 groups of women and compared them for the timing of the onset of their menstrual cycles. one group was rubbed on the upper lip with a mixture of alcohol and underarm perspiration collected from a single female donor. the other group was rubbed with plain alcohol. the group which recieved the perspiration showed a significant shift in the timing of their menstrual cycle
• McClintock found that 68% of women who were exposed to chemicals/hormones of other women experienced changes in their own cycles and closer in similarity to the cycles of the other women (menstrual synchrony)

evidence supports the role of light as an influence on SAD

rates of SAD tend to be higher in countries which have a higher latitude and where people would typically experience less hours of daylight. this supports the role of SAD as an infradian rhythm which is influenced by exogenous factors 

positive real world application 

research into SAD has led to the development of phototherapy to try and reduce the symptoms of depression in people with the disorder. its suggested to relieve the symptoms in up to 60% of suffers. it works by exposing people to bright light, it can reduce levels of melatonin and therefore increases levels of serotonin 

however, others argue that a placebo form of phototherapy can be effective in up to 30% of cases which suggests that the exogenous zeitgeber of light may not be the only influence on SAD with cognitive factors possibily playing a role 

ultradian rhythms are those which have a frequency of more than one cycle in 24hrs 

the sleep cycle 

one of the most common ultradian rhythms is the sleep cycle and the alteration between REM and non-REM sleep.this is an ultradian rhythm for the fact that this cycle repeats over the course of the night and lasts approximately 90 mins.

psychologists have identified 5 stages of sleep, one is REM and the other 4 are non-REM, 

Dement and Kleitman monitored the sleep patterns of 9 ps in a sleep lab over 61 nights. brain activity was recorded using an EEG and the effects of caffeine and alcohol were controlled for. it was found that sleep did occur in distinct stages and that REM was highly correlated with dreaming. this study supports the nature of RED/NREM sleep and the fact that it coccurs in stages as an ultradian rhythm

uses scientific and objective measurements 

the findings of sleep research should be valid, supporting the role of the sleep cycle as an ultradian rhythm because scientific measurements were used such as EEG recordings 

positive real world applications 

positive real world applications in attempting to maximise the positive effects o sleep and minimise the effects of sleep disruption

other exogenous factors may influence the sleep cycle 

Freidman and Fisher observed eating and drinking behaviour in agroup of psychiatric pateients over periods of 6 hrs. they detected a clear 90-minute cycke in eating and drinking behaviour supporting the role of BRAC as an ultradian rhythm