Biopsych Flashcards
Divisions of the nervous system
Nervous system
Central nervous system Peripheral nervous system
>spinal cord Somatic NS Autonomic NS
>brain >sympathetic NS
>parasympathetic NS
The central nervous system
The CNS comprises of the brain and the spinal cord. It has two main functions – the control of behaviour and the regulation of the bodies physiological processes.
The spinal cord
The main function of the spinal-cord is to relay information between the brain and the rest of the body. This allows the brain to monitor and regulate bodily processes, such as digestion and breathing, and to coordinate voluntary movements.
The brain
The brain can be divided into four main areas – the cerebrum, cerebellum, diencephalon and brainstem.
The cerebrum is the largest part of the brain, and is further divided into four different lobes each of which has a different primary function. The cerebrum is split down the middle into 2 halves called cerebral hemispheres. Each hemisphere is specialised for particular behaviours, and they communicate with each other through the corpus collosum.
The cerebellum sits beneath the back of the cerebrum. It is involved in controlling a persons motor skills and balance, coordinating the muscles to allow precise movements.
The diencephalon live beneath the cerebrum and on top of the brainstem. Within this area are two important structures, the thalamus and the hypothalamus.
The brainstem is responsible for regulating automatic functions that are essential for life.
The peripheral nervous system
There are two main divisions of the peripheral nervous system, the somatic nervous system and the autonomic nervous system.
The autonomic nervous system
Subdivides into the sympathetic and parasympathetic nervous system. Both of these divisions tend to regulate the same organs but have opposite effects.
The sympathetic nervous system.
Primarily involved in responses that help us deal with emergencies (the fight or flight response), such as increasing heart rate and blood pressure and dilating blood vessels in the muscles. It slows bodily processes that are less important in emergencies, such as digestion and urination.
The parasympathetic nervous system
The parasympathetic nervous system is responsible for relaxing the body once the emergency has passed. The PNS slows the heartbeat down and reduces blood pressure. It also restarts digestion. Because the PNS is involved with energy conservation and digestion, it is sometimes referred to as the bodies rest and digest system.
The structure and function of neurons
Neurons are cells that are specialised to carry neural information throughout the body. Neurons can be one of three types – sensory neurons, relay neurons or motor neurone.
Sensory neurons.
Sensory neurons carry nerve impulses from sensory receptors to the spinal-cord and the brain. When impulses reach the brain, they are translated into sensations so that the organism can react appropriately.
Relay neurons.
These are the most common type of neurons in the CNS. They allow sensory and motor neurons to communicate with each other.
Motor neurons.
Motor neurons form synapses with muscles and control their contractions. When stimulated the motor neurone releases neurotransmitters that bind to receptors on the muscle and trigger a response which leads to muscle movement.
Synaptic transmission
Once an action potential has arrived at the terminal button at the end of the axon, it needs to be transferred to another neuron or tissue. To achieve this it must cross the gap between the presynaptic neuron and the postsynaptic neuron. As the action potential reaches the synaptic vesicles , It causes them to release their contents through a process called exocytosis. The released neurotransmitter defuses across the gap between the pre-and the post synaptic cell, where it binds to specialised receptors on the surface of the cell that recognise it and are activated by that particular neurotransmitter. Once they have been activated, the receptor molecules produced either excitatory or inhibitory effects on the post synaptic neuron. This whole process is synaptic transmission.
Excitatory and inhibitory neurotransmitters.
Neurotransmitters can be classified as either excitatory or inhibitory in their action. Excitatory neurotransmitters such as noradrenaline and Aceytlcholine, are the nervous system is ‘on switches’. These increase the likelihood that an excitatory Signal is sent to the post synaptic cell, which is then more likely to fire. Inhibitory neurotransmitters such as serotonin and GABA, are the nervous systems ‘off switches’, in that they generally decrease the likelihood of that neuron firing.
EPSP = Excitatory post synaptic potential = more likely to fire. IPSP = inhibitory post synaptic potential = less likely to fire.
The strength of an EPSP can be increased in two ways. In spatial summation A large number of EPSPs are generated at many different synapses on the same post synaptic neuron at the same time. Temporal summation A large number of EPSPs are generated at the same signups by a series of high-frequency action potentials.
The fight for flight response to stress
The amygdala and the hypothalamus.
When an individual is faced with a threat, and area of the brain called the amygdala is mobilise. The amygdala associate sensory signals with emotions associated with fight or flight such as fear or anger. The amygdala then sends the stress signal to the hypothalamus which functions like a command centre in the brain communicating with the rest of the body through the sympathetic nervous system. The bodies response to stressors involves two major systems one for acute stressors and the other for chronic stressors.
Response to acute stressors. SAM
When the SNS is triggered it begins the process of preparing the body for the rapid action necessary for fight or flight. The SNS sends a signal through to the adrenal medulla which responds by releasing adrenaline into the blood.
Adrenaline - as it circulates through the body it causes a number of physiological changes. The heart beats faster pushing blood to the muscles heart and other vital organs. Blood pressure increases and breathing becomes more rapid in order to take in as much oxygen as possible with each breath. Adrenaline also triggers the release of blood sugar and fats to supply energy to parts of the body associated with the fight or flight response.
The parasympathetic nervous system- when the threat has passed The parasympathetic branch of the ANS dampen down the stress response. It reverses the effects of the sympathetic branch and also ensures that digestion begins again.
Response to chronic stressors (HPA AXIS)
H- hypothalamus- The hypothalamus releases a chemical messenger, corticotrophin releasing hormone (CRH), which is released into the bloodstream in response to the stressor.
P-pituitary gland- on arrival at the pituitary gland CRH causes the pituitary to produce and release ACTH. This is then transported in the blood stream to its target site in the adrenal glands.
A- adrenal glands- ACTH stimulates the adrenal cortex to release various stress related hormones including cortisol. Cortisol is responsible for several of fat in the body if you’re important in the F or F response. Some of these are positive e.g. a quick burst of energy, where as others are negative e.g. lowered immune response.
Localisation of function
MOTOR AND SOMATOSENSORY AREAS
The motor cortex.
Responsible for the generation of voluntary motor movements. It is located in the frontal lobe of the brain. Both hemispheres of the brain have a motor cortex, with the motor cortex on one side of the brain controlling the muscles on the opposite side of the body.
The somatosensory cortex.
This is the text sent three events arising from different regions of the body. Using sensory information from the skin the somatosensory cortex produces sensations of touch, pressure, pain and temperature which it then localised to specific body regions. As with the motor cortex both premises have a somatosensory cortex, with the cortex on one side of the brain receiving sensory information from the opposite side of the body.
VISUAL AND AUDITORY CENTRES.
Visual centres.
The primary visual centre in the brain is located in the visual cortex in the occipital lobe of the brain. However visual processing actually begins in the retina at the back of the eye where light enters and straight the photoreceptors. Nerve impulses from the retina and then transmitted to the brain by the optic nerve. The visual cortex spans both hemispheres with the right hemisphere receiving it input from the LHS of the visual field while the visual cortex in the left hemisphere receiving it input from the RHS of the visual field.
Auditory centres.
The auditory centre in the brain is concerned with hearing. Most of this area lies within the temporal lobes on both sides of the brain where we find the auditory cortex.
LANGUAGE CENTRES
Broca’s area
This area is named after Paul Broca The French neurosurgeon who discovered this area of the brain after treating a patient who he referred to as Tan because that was the only syllable this particular patient had expressed. After studying eight other patients Who had similar language defects he found lesions in the left frontal hemisphere. Which led him to the discovery of this area. This Area is responsible for the production of language.
Wernicke’s area.
Discovered shortly after Broca discovered his area. Whereas Broca’s patient could understand language but not speak, patients with a lesion in Wernickes area could speak but were not able to understand language and therefore what they were saying made little sense. This area is responsible for the processing of spoken language.
Lateralisation and split brain research.
Hemispheric lateralisation.
Refers to the fact that some mental processes in the brain are mainly specialised to either the left or right hemisphere. For example, researchers found that the left hemisphere is dominant for language and speech. However this raises an important question of language is located in the left hemisphere how can we talk about things that experience in the right hemisphere such as face recognition. The answer is that the two hemispheres are connected therefore allowing information to be sent to the other hemisphere through the corpus callosum.
The way to investigate this is through:
Split brain research
SPERRY AND GAZZINGA (1967)
They took advantage of The fact that information from the LVS goes to the right hemisphere and information from the RVS goes to the left hemisphere. Because the corpus callosum is cut in split brain patients, the information presented to one hemisphere has no way of travelling to the other hemisphere and can only be processed in the hemisphere that received it. In a typical study the split brain patients would fixate on a dot in the centre of the screen while information was presented to either the L or the R Visual field. They would then be asked to make responses with either the left hand or the right hand or verbally without being able to see what their hands were doing. For example if the patient was flashed a picture of a dog to the RVS and asked what they had seen they would say dog, however if they were shown a picture of a cat in the LVS when asked what they had seen they would say nothing but when asked to draw it they could. This provides strong proof for lateralisation of the brain.
Plasticity and functional recovery of the brain.
PLASTICITY
Refers to the brains ability to modify its own structure and function as a result of experience.
Plasticity as a result of life experience
As people gain new experiences nerve pathways that are used frequently develop strong connections whereas neurons that are rarely or never used eventually die. This developing new connections and pruning away weak ones shows the brain is able to constantly adapt to a changing environment. However this can decline with age. Boyke found evidence of brain plasticity in 60-year-olds taught a new skill of juggling. They found increases in grey matter in the visual cortex although when practising stopped these changes were reversed.
Video games.
Playing video games makes many different complex cognitive and motor demands.Kuhn et al compare to control group with the video game training game that was trained for two months for at least 30 minutes per day on the game Super Mario. They found a significant increase in grey matter in various brain areas including the cortex, hippocampus and cerebellum. This increase was not evident in the control group. The researchers concluded that video game training had resulted in new synaptic connections in the brain areas.
Meditation.
Researchers working with Tibetan monks have been able to demonstrate that meditation can change the inner workings of the brain. Davidson impaired eight practitioners of Tibetan meditation with 10 student volunteers who had no previous meditation experience. They were both fitted with electrical sensors and asked to meditate. The electric picked up a greater activation of gamma waves in the monks. The researchers concluded that meditation not only changes The workings of the brain but may also produce permanent changes.
FUNCTIONAL RECOVERY AFTER TRAUMA
refers to the recovery of abilities and mental processes that have been compromised as a result of brain injury or disease.
Mechanisms for recovery.
Neuronal unmasking.
Wall first identified what he called dormant synapses in the brain. These are synaptic connections that exist but the function is blocked. The unmasking of dormant synapses can open connections to regions of the brain that are not normally activated. Giving way to the development of new structures.
Stem cells.
Unspecialised cells have the potential to give rise to different cell types but carry out different functions, including the characteristics of nerve cells. There are a number of years on house themselves might work to provide treatment for the brain damage caused by injury or neurodegenerative disorders. The first view is that stem cells implanted into the brain would directly replace dead or dying cells. The second possibility is that transplanted stem cells secrete growth factors that somehow rescue the injured cells. The third possibility is that transplanted cells for manual network which links in an injured brain site where new stem cells are made with the damage region of the brain.
Ways of studying the brain
Post mortem
Way of examining the brains of people who have shown particular psychological abnormalities prior to their death in an attempt to establish the possible neurobiological cause for this behaviour. For example Tan, who had a lesion in his Broca’s area.
SCANNING TECHNIQUES
Functional magnetic resonance imaging (FMRI)- A technic for measuring brain activity. It works by detecting changes in blood oxygenation and flow that indicate increased neural activity. If a particular area of the brain becomes more active there is an increased demand for oxygen in that area therefore there is an extra demand for bloodflow in that area. As a result of these changes in bloodflow, research is able to produce maps showing which areas of the brain are involved in a particular mental activity.
Electroencephalogram- A method of recording changes in the electrical activity of the brain using electrodes attached to the scalp. When electrical signals from the different electrodes and graphs over a period of time the resulting representation is called an EEG. And EEG can be used to detect various types of brain disorder or diagnose other disorders that influence brain activity.
Event – related potentials (ERPs)- A technic that takes raw EEG data and uses it to investigate cognitive processing of a specific event. It achieves this by taking multiple readings and averaging them in order to filter out all brain activity that is not related to the appearance of the stimulus.
Circadian rhythms
A circadian rhythm is a pattern of behaviour that occurs or recurs every 24 hours, and which affect and reset by environmental light levels.
An example of this is the sleep wake cycle.
The circadian rhythm not only dictates when we should be sleeping, but also when we should be awake. Light and darkness are the external signals that determine when we feel the need to sleep and when to wake up. The rhythm also dips and rises at different times of the day, so our strongest sleep drive usually occurs in 2 dips between 2 to 4 AM and between 1 to 3 PM. The sleepiness we experience do during these circadian dips is less intense if we have had sufficient sleep and more intense when we are sleep deprived.
It is also determined due to homoeostatic control. When we been awake for a long period of time homoeostasis tells us that the need for sleep is increasing because of the amount of energy used up during wakefulness, this increases throughout the day. Therefore the circadian system keeps us away as long as there is daylight, prompting us to sleep as it becomes dark. The internal circadian clock is described as free running i.e. it will maintain a cycle of about 24 to 25 hours even in the absence of external cues, however it is intolerant of any major changes e.g. shiftwork because this causes the biological clock to become completely out of balance.
Case study
Siffre. On several occasions he subjected himself for long periods of time living on the ground in order to study his own circadian rhythms. While living on the ground he had no external cues to guide his rhythms, he simply woke, eight and slept when he felt it was appropriate to do so. The only thing influencing his behaviour was his internal body clock. After his first underground state of 61 days in the southern alps he resurfaced on the 17th of September leaving the date was the 20th of August. On his final underground say he was interested in the effects of ageing on circadian rhythm is and found that his body clock ticked more slowly compare to when he was younger man.
Other circadian rhythms:
- Core body temperature.
- hormonal production.
Ultradian and infradian rhythms
ULTRADIAN RHYTHMS
Cycles the last less than 24 hours, such as the cycle of sleep stages that occur throughout the night.
Sleep stages.
The ultradian rhythm found in human sleep follow the pattern of alternating REM and nREM sleep, which consists of stages 1 through to 4. This cycle repeats itself about every 90 to 100 minutes throughout the night. With different stages having different durations. Most of what we know about these different stages of sleep comes from the recording of electrical activities of the brain with each stage showing a distinct EEG pattern.
Stage 1: 4-5% light sleep, muscle activity slows down, occasional twitching.
Stage 2: 45-55% breathing pattern and heart rate slows. Slight decrease in body temperature.
Stage 3: 4-6% deep sleep begins. Brain begins to generate slow delta waves.
Stage 4: 12-15% very deep sleep. Rhythmic breathing. Limited muscle activity. Brain produces delta waves.
Stage 5: 20-25% R.E.M. Brainwaves speed up and dreaming occurs. Muscles relax and heart rate increases. Breathing is rapid and shallow.
The basic rest activity cycle (BRAC)
Kleitman referred to the 90 minute cycle found during sleep as the BRAC. However, he also suggested that this 90 minute ultradian rhythm continues during the day even when we are awake. The difference is that during the day rather than moving through sleep stages we move progressively from a state of alertness into a state of physiological fatigue every 90 minutes. Research suggests that the human mind can focus for a period of about 90 minutes and towards the end of these 90 minutes the body begins to run out of resources resulting in a loss of concentration fatigue and hunger. For example at 10:30 AM coffee break allows workers to divide the 9 AM to noon morning session into 2 90 minute phases.
INFRADIAN RHYTHMS
Rhythms that have a duration over 24 hours, may be weekly, monthly or even annually.
Weekly rhythms- there are obvious differences in human behaviours that conform to a weekly cycle. For example male testosterone levels are elevated at weekends and young couples report more sexual activity on weekends then on weekdays.
Monthly rhythms- The women’s reproductive cycle is known as a menstrual cycle because it lasts about one month. However there are considerable variations in the length of this cycle. The average is around 28 days. It is regulated by hormones which either promote ovulation or stimulate the uterus for fertilisation.
Annual rhythms- in most animals and you rhythms are related to the seasons but in humans the calendar-year appears to influence behaviour regardless of changes in temperature. Research suggests that seasonal variation in mood and human, especially women, with some people becoming severely depressed during the winter months (SA.D.). The winter is also associated with an increase in heart attacks. In fact there is a robust annual rhythm in human deaths with most deaths occurring in January.
ENDOGENOUS pacemakers and exogenous zeitgebers
ENDOGENOUS PACEMAKERS
Mechanisms within the body that govern the internal, biological bodily rhythms.
The suprachiasmatic nucleus (SCN).
In mammals the main endogenous pacemaker is the SCN which lies in the hypothalamus. The SCN plays a role in generating the bodies circadian rhythms, it acts as the master clock which links to other brain region that controls sleep and arousal and has control over other biological clock throughout the body.
The pineal gland.
The scn send signals to the pineal gland directing it to increase production and secretion of the hormone melatonin at night and to decrease it is light levels increase in the morning. Melatonin in Jesus sleep by inhibiting the brains mechanism that promotes wakefulness. The pineal gland and SCN function jointly as indulge in a pacemakers in the brain.
EXOGENOUS ZEITGEBERS
An environmental cue, such as light, that helps to regulate the biological clock in an organism.
Light.
Receptors in the SCN are sensitive to changes in light levels during the day and use this information to synchronise the activity of the bodies organs and glands. Light reset the internal biological clock each day keeping it on a 24 hour cycle. Rods, cones and a protein called Melanopsin detect light and critical for resetting the biological clock.
Social cues.
Social stimuli, such as mealtimes and social activities, may also have a role as zeitgebers. Aschoff showed the individual is that able to compensate for the absence of zeitgebers such as natural light by responding to social zeitgebers instead.
