Biopsychology

Question 1

CNS

Answer 1

Brain and spinal cord, it controls behaviour and regulation of the body’s physiological processes, to do this the brain receives info from the sensory receptor and sends messages to the muscles and glands of the body

Question 2

Brain

Answer 2

Cerebrum- largest part of the brain, four lobes and two hemispheres
Cerebellum- motor skills, balance and coordinating muscles to allow precise movements
Diencephalon- thalamus ( consciousness, sleep and alertness)+ hypothalamus (regulates body tempo, stress response and hunger and thirst)
Brain stem- regulates breathing and heart rate

Question 3

Spinal cord

Answer 3

Relay informs between the brain and the rest of the body, allows brain to monitor and regulate bodily processes e..g digestion, connected to different parts of the body by pairs of spinal nerves, connecting specific muscles and glands

Question 4

Peripheral nervous system

Answer 4

Consists of somatic and autonomic nervous system, responsible for transmitting messages to and from the CNS

Question 5

Somatic nervous system

Answer 5

Responsible for tracks siting information from sense organs to the CNS and transmitting in from from the CNS to the effectors (e.g. muscles and glands), control voluntary movement under conscious control, it has sensory and motor pathway, controls skeletal muscles. Controlled by the motor cortex

Question 6

Automatic nervous system

Answer 6

Has the sympathetic and parasympathetic nervous system and is responsible for transmitting info to and from internal bodily organs, it is involuntary, only has motor pathways and it controls smooth muscles and the internal organs and glands of the body. Controlled by the brain stem

Question 7

Sympathetic Nervous System (SNS)

Answer 7

works alongside the endocrine system to bring about physiological arousal in the fight or flight response. It is activated when a person is stressed. Heart rate and breathing increase, digestion stops, salivation reduces, pupils dilate, and the flow of blood is diverted from the surface on the skin (fight or flight response).

Question 8

The Parasympathetic Nervous System (PNS)

Answer 8

system works alongside the endocrine system to return the body to its resting state after fight or flight. Heart rate and breathing reduce, digestion starts, salivation increases, and pupils constrict. This is known as the rest and digest response.

Question 9

Structure of neurone

Answer 9

Neurons are specialised nerve cells that move electrical impulses to and from the Central Nervous System (CNS).
There are several parts to a neuron;
• Cell Body: Control centre of the neuron.
• Nucleus: Contains genetic material.
• Dendrites: Receives an electrical impulse (action potential) from other neurons or sensory receptors (e.g. eyes, ears, tongue and skin).
• Axon: A long fibre that carries the electrical impulse from the cell body to the axon terminal.
> Myelin Sheath: Insulating layer that protects the axon and speeds up the transmission of the electrical impulse.
> Schwann cells: Make up the myelin sheath.
• Nodes of Ranvier: Gaps in the myelin sheath. They speed up the electrical impulse along the axon.

Question 10

Sensory neurone

Answer 10

Sensory neurons are found in sensory receptors. They carry electrical impulses from the sensory receptors to the CNS (spinal cord and brain) via the Peripheral Nervous System (PNS). Sensory neurons convert information from sensory receptors into electrical impulses. When these impulses reach the brain they are converted into sensations, such as heat, pain etc. so that the body can react appropriately. Some sensory impulses terminate at the spinal cord. This allows reflexes to occur quickly without the delay of waiting for the brain to respond.

Question 11

Motor neurone

Answer 11

Motor neurons are located in the CNS but project their axons outside of the
CNS. They send electrical impulses via long axons to the glands and muscles so they can affect function. Glands and muscles are called effectors. When motor neurons are stimulated they release neurotransmitters that bind to the receptors on muscles to trigger a response, which leads to movement.

Question 12

Relay neurone

Answer 12

Relay neurons are found in the CNS. They connect sensory neurons to motor neurons so that they can communicate with one another. During a reflex arc (e.g. you put your hand on a hot hob) the relay neurons in the spinal cord are involved in an analysis of the sensation and decide how to respond (e.g. to lift your hand) without waiting for the brain to process the pain.

Question 13

Synaptic transmission

Answer 13

Neurones transmit electrical impulses (action potentials) between pre and post synaptic neurons, when it reaches the pre synaptic terminal it triggers the release of neurotransmitters from vesicles in a process of exocytosis, the neurotransmitters will diffuse across the syntactic cleft where if binds to specialised post synaptic receptor sites on the post synaptic membrane. It only takes a fraction of a second and the effects are terminated in a process called re-uptake. The neurotransmitter is taken back by the vesicles on the presynaptic neurone where they are stored for later release, the quicker it is taken back the shorter the effects

Question 14

Excitatory or inhibitory

Answer 14

Most are both, but GABA is purely inhibitory, excitatory neurotransmitters cause an electrical change in the membrane of the post-synaptic neuron resulting in an excitatory post synaptic potential, meaning that the post synaptic neurone in more likely to fire an impulses opposite for inhibitory

Question 15

Epsp and Ipsp

Answer 15

The likelihood that the neuron will fire an impulses opposite is determined by adding up the excitatory and the inhibitory synaptic input, the net result of this calculation is summation

Question 16

Direction of synaptic transmission

Answer 16

Information can only travel in ONE direction at a synapse. The vesicles containing neurotransmitters are ONLY present on the pre-synaptic membrane. The receptors for the neurotransmitters are ONLY present on the post-synaptic membrane. It is the binding of the neurotransmitter to the receptor which enables the information to be transmitted to the next neuron.
Diffusion of the neurotransmitters mean they can only go from high to low concentration, so can only travel from the pre-synaptic membrane to the post-synaptic membrane.

Question 17

Medication

Answer 17

Psychoactive drugs (medication that affects brain function to alter perception, mood or behaviour), such as SSRIs, work by affecting (increasing or inhibiting) the transmission of neurotransmitters across the synapse.
Some pain medications mimic the effects of inhibitory neurotransmitters.
Stimulation of postsynaptic receptors by an inhibitory neurotransmitter results in inhibition of the postsynaptic membrane. When an inhibitory neurotransmitter binds to the post-synaptic receptors it makes the post-synaptic neuron less likely to fire. Due to summation, if inhibitory neurotransmitters are higher than excitatory neurotransmitters they can inhibit an action potential from occurring. Therefore, pain medications would decrease the overall activity and reducing brain activity may lead to less pain.

Question 18

Endocrine system

Answer 18

It provides a chemical system of communication in the body via the blood stream, they produce and secrete hormones into the bloodstream which are required to regulate many bodily functions, the major ones are pituitary gland and the adrenal glands. Each gland produces different hormones which regulate activity of organs/tissues in the body, they only affect limited number of cells (target cells). Because they have the receptor for that hormone, when enough receptor sites are stimulated by that hormone there is a physiological reaction

Question 19

Pituitary gland

Answer 19

Located in the brain, controlled by the hypothalamus, controls the release of hormones from all other glands, e.g. it produces ACTH which is involved in the stress response by stimulating the production and release of cortisol from the adrenal glands (anterior pituitary gland), releases hormone OxyContin which is crucial for mother/infant bonding (posterior pituitary gland)

Question 20

Adrenal glands

Answer 20

We have 2, situated on top of each kidney, each one made up of two distinct parts, adrenal gland produces adrenaline which triggers fight or flight response

Question 21

Adrenal cortex

Answer 21

Outer section of the adrenal gland, produces hormone cortisol produced in high amount when someone is experiencing chronic stress, also responsible for the cardiovascular system e.g. increases bo and causes blood vessels to constrict

Question 22

Adrenal Medulla

Answer 22

Inner section of the adrenal glands, produces adrenaline

Question 23

Sympathomedullary pathway

Answer 23

During stressful situations the body’s fight or flight response is activated by the sympathetic branch of the autonomic nervous system, the sympathetic nervous system is trigger by the hypothalamus, it then stimulates the adrenal medulla to release adrenaline in the blood stream

Question 24

Evaluation of fight or flight response

Answer 24

+ makes sense from evolutionary psychology- explains how individuals survived threats
+studies show that adrenaline is essential for preparing the body in stressful situation, a person with a malfunctioning adrenal gland does not have normal, fight or flight response
-freeze
-women are more likely to tend and befriend- hormone oxycotocin

Question 25

Localisation of function

Answer 25

Principle that functions have specific locations within the brain, the hemisphere of the cerebrum represent the opposite side of the body (contralateral organisation)

Question 26

Motor cortex

Answer 26

Responsible for voluntary movements, located in the frontal lobe of both hemisphere, different parts of the motor cortex control different parts of the body. Damage to this area can cause loss of muscle function in one or both sides of the body depending on the hempishere

Question 27

Somatosensory cortex

Answer 27

Responsible for processing sensations such as pain and pressure, located in the parietal lobe of both hemisphere

Question 28

Visual cortex

Answer 28

Process info such as colour and shape, located in the occipital lobe of both hemisphere, visual processing starts in the retina where light enters and strikes the photoreceptors, transmitted to the brain by the optic nerve

Question 29

Auditory cortex

Answer 29

Process info such as pitch and volume, lies in the temporal lobe in both hemisphere of the brain, begins in the cochlea in the inner ear, where sound waves are converted to nerve impulses which travel via the auditory nerve to the auditory cortex

Question 30

Broca’s area

Answer 30

Lesion to the left hemisphere of the frontal lobe, damage to the Broca’s area causes expressive aphasia, the disorder affects language production but not understanding

Question 31

Wernicke’s area

Answer 31

Left hemisphere of the frontal lobe, could speak but not understand language, it is responsible for processing of spoken language, both are connected by a neural loop, causes receptive aphasia

Question 32

Evaluation

Answer 32

- Some functions are more localised than others. Motor and somatosensory functions are highly localised to specific areas of the cortex. However, higher functions (e.g. personality and consciousness) are much more widely distributed Functions such as language are too complex to be assigned to just one area and instead involve networks of brain regions. Although some components of language, such as speech production, may be localised (Broca's Area. - Equipoteniality theory (Lashley, 1930) holds that higher mental functions are not localised. The theory also claims that intact areas of the cortex take over responsibility for a specific cognitive function following injury to the area normally responsible. - Dronkers et al. (2007) re-examined the preserved brains of two of Broca's patients. MRI scans revealed that several areas of the brain had been damaged. Lesions to the Broca's Area cause temporary speech disruption they do not usually result in severe disruption of language. Language is a more widely distributed (and less localised) skill than originally thought. - It may be that how brain areas communicate with each other is more important than specific brain regions. Dejerine (1892) reported a patient who could not read because of damage between the visual cortex and Wernicke's area. - Bavelier et al. (1997) found that there are individual differences in which brain areas are responsible for certain functions. They found that different brain areas are activated when a person is engaged in silent reading. They observed activity in the right temporal lobe, left frontal lobe and occipital lobe. This means that the function of silent reading does not have a specific location within the brain.,

Question 33

Hemispheric lateralisation

Answer 33

Certain functions are governed by one side of the brain Language centres are lateralised,aided to the left hemisphere, the right hemisphere is dominant for visual-spatial funcgkon and facial recognition, both are connected by a bundle of nerve fibres known as cropus callosum allowing for info to be communicated between the two hemisphere

Question 34

Evaluation of hemispheric lateralisation

Answer 34

+ an advantage is that it makes sense from an evolutionary perspective, it increases neural processing capacity which adaptive, by using both hemispheres for different tasks we increase chances of survival, chickens found to be able to perform 2 tasks simultaneously (finding food and being vigilant for predators) +patients with extensive damage to their left hemisphere can experience global aphasia (loss of speech production and speech comprehension), suggesting that language is later,aided to the left hemisphere - lateralisation patterns shift with age with most tasks becomeing less lateralised in healthy adulthood -speech isn’t fully lateralised to the left, as JW a split brain patient developed the capacity to speak using his right hemisphere, with the result that they could speak about info presented either left or right visual field (more fluent with left) -if one hemisphere is damaged then the other hemisphere undamaged regions can compensate. EB an Italian 17 yrs old boy had his left hemisphere removed due to benign tumour at the age of 2.5,his language seemed normal in every day life however further testing showed that he Had poorer than normal skill of naming pictures and reading of loan words

Question 35

Split brain patients

Answer 35

Patients who underwent this procedure to have their corpus callous cut to prevent the violent electrical activity caused by epileptic seizures crossing from one hemisphere to the other. Information from the left visual field goes into the right hemisphere and vice versa however split brain patients have severed corpus callous there is no way for the information to travel from one to the other hemisphere

Question 36

Split brain research

Answer 36

Patients are asked to stare at a dot in the centre of a screen and then info is either presented to the right or left visual field. They are then asked to make a response by either left hand, right hand or ,verbally (left hemisphere) without being a belt to see what their hands are doing. They may be flashed an image of a dog in their right and then asked what they have seen, they will be able to say dog because the info will have travelled into their left hemisphere where the language centres are located. However if shown a cat on the left they won’t be able to say it, but will be able to draw it their left hand because the right hemisphere control this hand

Question 37

Evaluation of split brain research

Answer 37

+highly controlled and scientific - the disconnection between the hemispheres wasn’t constant between all patients -some split brain patients have experience of drug therapy for much longer than others - the comparison groups were not considered to be valid as they were often people with no history of epileptic seizures - many studies have as few as three participants, so there is difficulty in generalising - the data is very artificial and lacks ecological validity, because in real world a severed corpus callous, can be compensated for by unrestricted use of both visual fields

Question 38

Brain plasticity

Answer 38

Ability of the brain to modify the structure and functions based in experience . It allows the brain to cope with the indirect effects of brain damage, such as swelling or haemorrhage following a road accident, or the damage resulting from inadequate blood supply from a stroke

Question 39

Evaluation of brain plasticity

Answer 39

+a psychologist found an increase in grey matter in hippocampus, visual correct and cerebellum of the brain after playing video games for 3- mins a day over two months +a psychologist demonstrates the permanent damage in the brain generated after prolonged meditation (higher rate of gamma waves which coordinate neural driving) than students with no experience of meditation +another psychologist found that the posterior hippocampus volume of London taxi drivers positively correlated with their time as a driver, there was also a significant difference between taxi drivers brain and those of a control group

Question 40

Functional recovery

Answer 40

Where the brain recovers abilities previously lost due to brain damage ( it is an example of plasticity). Younger brain are more plastic but the brain is camels of functional recovery and plasticity at any age, studies show that women recover from a brain injury faster than men do. Full recovery of the brain is not passive, depends on the extent of the damage and on various internal and external factors over time. Spontaneous recovery from a traumatic event tends to slow down after a few weeks so treatments are required to maintain improvements in functioning

Question 41

Stages of brain recovery

Answer 41

Neuronal unmasking- dormant synapses are activated to compensate for damaged areas of the brain, structural changes support it, such as axon sprouting ( undamaged axons grow new nerve endings to fo reconnect the neurones which severed by damage), reformation of blood vessels (facilitates the growth of new neuronal pathways) and recruitment of homologous areas (the intact hemisphere takes over he functions of the damaged Hampshire) Neural reorganisation- transfer of functions from damaged areas of the brain to the undamaged areas (greater in children) Neural regeneration- growth of new neurons to compensate for the damaged areas

Question 42

Evaluation of functional recovery

Answer 42

+ practical applications to the field of neural rehabilitation, understanding this concept has led to the development of techniques like motor therapy and electrical stimulation of the brain to counter the negative effects and deficits in motor and cognitive functions following accidents -variable factors affect recovery after trauma. Research has found that those with a university education recover better, going to university provides a cognitive reserve. Age is another important aspect, neural reorganisation is better in children, gender also has impact as women are likely to recover from a brain injury. Alcohol and such can impair functional recovery

Question 43

Post mortem examinations

Answer 43

Psychologists may study a person who displays an interesting behaviour while they are alive. When the person dies they look for abnormalities in the brain to explain the behaviour. Post mortem studies have found link between brain abnormalities and psychiatric disorder e.g. there is evidence of reduced glial cells in the frontal lobe of patients with depression

Question 44

Evaluation of post mortem examination

Answer 44

+ allow for more detailed examination of anatomical and neurochemical aspects of the brain than would be possible with other methods, allowed psychologists to examine deeper region such as hippocampus and hypothalamus -may lack validity, because people die in a variety of circumstances and at varying stages of diseases, and th r length of time between death and post mortem aswell as drug therapy can all affect the brain -they have a small sample size, so can not be said to be representative

Question 45

fMRI

Answer 45

Functional magnetic resonance imaging, provides an indirect measure of neural activity. Using magnetic field and radio waves to monitor blood flow in the brain. Measures change in the energy release by haemoglobin , to reflect on the activity of the brain to give a moving picture of brain; activity in regions of interest can be compared during a base line task and during a specific activity

Question 46

Evaluation of fMRI

Answer 46

+captures dynamic brain activity as opposed to a post mortem examination which purely show the physiology of the brain + fMRI have good spatial results (smallest feature that a measurement can detect) -interpretation is difficult and is affected by poor temporal resolution (resolution of a measurement with respect to time), biased interpretation and by the base line task used -fMRI research is expensive so a small sample size

Question 47

EEG

Answer 47

Electroencephalagram, directly measures general neural activity in the brain, usually linked to states like sleep and arousal. Electrodes are placed on the scalp and detect neural activity directly below where they are placed, different number of electrodes can be used depending on the focus of the study, when the electrical signals from different electrode are graphed over a period of time, the representation is called an EEG pattern, patients with epilepsy show spikes of electrical activity, those with brain injury show a slowing of electrical activity

Question 48

Evaluation of EEG

Answer 48

+ useful in clinal diagnosis, for instance allows the recording of neural activity associated with epilepsy so the doctor can confirm seizures - cheaper than fMRI so can be used more widely in research -have poor spatial resolution

Question 49

Event related potential

Answer 49

Electrodes are placed on the scalp and directly measure neural activity in response to a specific stimulus introduced by a researcher. They are difficult to pick out from all other electoral activity being generated within the brain. To establish a specific response to a target stimulus many presentations of this stimulus and the responses are averaged together. Any extraneous neural activity that is not related to the specific stimulus will not occur consistently whereas activity linked to the stimulus will

Question 50

Evaluation of a ERP

Answer 50

+ measure the processing of a stimulus even in the absence of a behavioural response, therefore it is possible to measure covertly the processing of a stimulus + cheap so used widely +good temporal resolution -poor spatial resolution -only sufficiently strong voltage changes generated across the scalp are recordable, important electrical activity occurring deeper in the brain is not recorded, restricted to the neocortex

Question 51

Biological rhythms

Answer 51

Cyclical changes in physiological systems, evolved because the environment in which organism live have cyclical changes e..g day/night. There are three types of biological rhythms: ultradian infradian , circadian

Question 52

Circadian rhythms

Answer 52

Are any cycle that lasts 24 hours. Nearly all organisms possess a biological representation of the 24 hours da, these optimise an organisms physiological and behaviour to best meet the demand of the day/night cycle. Driven by the SCN (suprachiasmatic nuclei) in the hypothalamus . This pacemaker controls the rate at which something occur, must constantly reset so we are in synchrony with the outside world. Natural light provides the input to the system, setting the SCN to the correct time in a process called photo entrainment. The SCN uses this information to coordinate activity of circadian rhythms throughout the body

Question 53

Sleep wake cycle

Answer 53

Light and darkness are the external signals that determine when we feel the need to sleep or wake up. This rhythm dips and rises at different times of the day, the strongest sleep urge is between 2-4 am and 1-3pm. Melatonin is released during darkness (pineal gland) induced sleep by inhibiting neural mechanism that promote wakefulness, light suppress the production of it, sleep and wakefulness is also under homeostatic control, homeostatic tells us that we need for sleep because of the amount of energy used up, this drives gradually increases throughout the day, reaching maximum in the late evening. Circadian rhythms keep [us awake until there is daylight promoting sleep when it is dark, the homeostatic system tends to make us sleeper regardless of light. The internal circadian rhythm maintains a cycle of 24-25 hours even without natural light

Question 54

Evaluation of the circadian rhythm

Answer 54

+ one application- chronotherapeutics . The time the patient takes medication it’s important for the success of the procedure, it is essential that the right concentration of drug is released in the target area of the body athe time the drug is needed. Risk of heart attack is the greatest during the early morning hours, medications have been developed which are taken at night but not released until 6am -There are individual differences in the length of circadian rhythms. One research study found that cycles can vary from 13 to 165 hours (Czeisler et al, 1999). - Another individual difference in circadian rhythms is when they reach their peak. 'Morning people' prefer to rise early and go to bed early whereas 'evening peoplé prefer to rise late. - Studies of individuals who live in Artic regions, where the sun does not set in the summer months, show normal sleeping patterns despite the prolonged exposure to light. This suggests that there are occasions where the exogenous zeitgeber of light may have very little bearing on our internal biological rhythms. -

Question 55

Ultradian rhythm

Answer 55

Span of a period less than 24 hours, e.g. five sleep stages, human sleep follows an alternating pattern of rapid eye movement sleep (stage five) and non rapid eye movement (1,2,3,4) the cycle repeats itself every 90 minutes. Each stage shows a distinct EEg pattern, as the person enters deep sleep their brainwaves slow and their breathing and heart rate decreases, during the fifth stage eeg is similar to that of an awake person this where dreaming occurs. This it the basic rest activity cycle, this continues even when we are awake, during the day rather than moving through the stages of sleep we move progressively from a state of alertness into a state of physiological fatigue, human mind can focus for 90 minutes before it starts to run out of resources and become fatigued, hungry and loss ofconcentration

Question 56

Evaluation of ultradian rhythm

Answer 56

+ an elite group of violinists had group practice session which were limited to 90 minutes at a time, violinist frequently napped to recover from practice, and those who napped often were better, this is the same amongst athletes , chess player I and writers - there are individual differences in ultradian rhythms which are biologically determined and may even be genetic in origins. Participants were studied for 11 day and night in lab environments. The researchers assessed sleep duration, time taken to fall asleep and the amount of time in each sleep stage. They found differences in all of these characteristics

Question 57

Infradian rhythms

Answer 57

Span over a period of 24 hours, may last weeks, months or years. Ones example is the mestrual cycle which lasts for about a month. There are variation in the length of the cycle with some women expert 23 day cycles whilst others 36 days, average is about 28 days. Hormones regulate the menstrual cycle, ovulation occurs roughly halfway through the menstrual cycle, when oestrogen levels are at their peak and usually lasts for 16-32 hours. After ovulation, progesterone levels increase in preparation for the possible implantation of an embryo in uterus

Question 58

Evaluation of the infradian rhythm

Answer 58

+ infradian rhythms can affect behaviour, women express a preference for feminised male faces when choosing a partner for a long term relationship, however they showed a preference for masculinised faces during ovulation - the menstrual cycle is not only governed by infradian rhythms, where several women of childbearing age live together and do not take oral contraceptive their menstrual cycles synchronism, in one study sample of sweat collected from one group of women and rubbed onto the upper lip of another group women, their menstrual cycles became synchronised (pheromones), these are chemical substances produced and released into the environment by an animal which affect the behaviour of others of the same species

Question 60

Biological rhythms- endo and exogenous zeitgebers

Answer 60

Our internal biological rhythms is finely tuned to stay in keeping with the outside world, in order to achieve this we have endogenous ( body clocks like SCN) and exogenous (light) zeitgebers

Question 61

Endogenous pacemakers

Answer 61

SCN- tiny cluster of nerve cells in the hypothalamus, plays an Importnsnt role in generation of circadian rhythms, acts as a master clock linking other brain regions that control sleep and arousal and controlling all other biological clocks throughout the body. Neurons within the SCN synchronise with each other, so that their target neurons in sites elsewhere in the body receive time-coordinated signals. These peripheral clocks can maintain a circadian rhythm, but not for very long, which is why they are controlled by the SCN. This is possible because of the SCN's built in circadian rhythm, which only needs resetting when external light levels change. The SCN receives information about light levels through the optic nerve. If our biological clock is running slow then morning light shifts the clock. + melatonin

Question 62

Evaluation of endogenous pacemakers

Answer 62

+ study of Kate Aldcoft who spect u25 days in a lab, had no excess to light to reset the SCN, at the end of her investigation she still had s core temperature rhythm of 24 hours so we do not need light to maintain our internal biological rhythms - her sleep wake cycle extended to 30 hours with period sleep as long as 16 hours

Question 63

Exogenous zeitgebers

Answer 63

Environmental events that are responsible for maintaining the biological clock of an organism, usually light. Receptors in the SCN are sensitive to changes in light levels during the day and use this info to synchronise the activity of the body’s organs and glands, light resets the internal biological lock each day keeping it on a 24 hour cycle. A protein in the retina of the eye called melanomas in (sensitive to light) When people move to a night shift or travel to a country with a different time zone their endogenous pacemakers try to impose their inbuilt rhythm of sleep, but this is now out of synchrony with their exogenous zeitgebers of light, leads to disrupted sleep patterns, increased anxiety and decreased alertness and vigilance

Question 64

Evaluation of exogenous zeitgebers

Answer 64

+ The vast majority of blind people who still have light perception have normal circadian rhythms. Blind people without light perception show abnormal circadian rhythms. This shows the vital role that the exogenous zeitgeber of light levels play in maintaining our internal biological rhythms. +exposure to bright light prior to an east-west flight decreased the time needed to adjust circadian rhythms to local time - Studies of individuals who live in Artic regions, where the sun does not set in the summer months, show normal sleeping patterns despite the prolonged exposure to light. This suggests that there are occasions where the exogenous zeitgeber of light may have very little bearing on our internal biological rhythms.