Biopsychology Flashcards
What is the nervous system?
Primary internal communication system, transmitting electrical/chemical signals between different parts of the body via a specialised network of nerve cells
What are the 2 main functions of the nervous system?
Collect, process, and respond to information in the environment
Co-ordinate the working of different organs and cells in the body
What are the divisions of the nervous system?
What is the function of the central nervous system?
Controls behaviour and regulates physiological processes
Origin of all complex commands + decisions
What is the purpose of the brain?
Centre of all conscious awareness/psychological processes, including higher order thinking
Interprets + stores info, sending order to muscles/glands
What are the parts of the brain?
3mm outer layer cerebral cortex
2 hemispheres
What is the purpose of the spinal cord?
Extension of the brain via brain stem
Connects brain to PNS so info is transferred between brain and body
responsible for reflex actions
What is the similarity between the brain and spinal cord?
Both control involuntary processes
eg: brain- breathing
eg: spinal cord- reflexes
What are 2 differences between the brain and spinal cord?
Brain is responsible for conscious awareness allowing for higher order thinking BUT spinal cord allows for simple reflex responses
Brain has multiple regions responsible for dif functions BUT spinal cord has 1 main function (to connect brain to PNS)
What is the function of the peripheral nervous system?
Transmits messages via millions of neurons/nerve cells to/from CNS
What does the peripheral nervous system consist of?
All nerves that lie outside of brain and spinal cord
What does the somatic nervous system do?
Sensory neurons recieve info from sensory receptor cells in the sense organs/skin (communication with outside world), transmits messages to CNS
Motor neurons transmit motor signals from CNS to skeletal muscles to produce voluntary muscles movement (under conscious control)
BUT some movement are involuntary, eg: reflex arc
What does the autonomic nervous system do?
Involuntary processes (outside of conscious control) eg: heart rate, blood pressure
Self-regulates internal environment (homeostasis) and controls smooth muscles + glands
Transmits info from internal body organs/glands to CNS and back
What is the similarity between the somatic NS and autonomic NS?
Both respond to external stimuli
eg somatic- sensory neurons to CNS
eg autonomic- fight or flight preparation
What are 3 differences between the somatic NS and autonomic NS?
SNS voluntary (under conscious control) : ANS involuntary (outside of conscious control)
SNS controls skeletal muscles/movement : ANS controls internal body organs/glands/smooth muscles
SNS sensory + motor pathways : ANS only motor pathways
How do the 2 branches of the autonomic nervous system work?
Each branch connected to a number of bodily organs
Works with endocrine system to bring about physiological change
Works in opposition: as activity in one falls, rises in the other
What is the function of the sympathetic nervous system?
Brings about physiological arousal in fight or flight response
Messages travel from SyNS to organs in body to prepare for action in dangerous situations
What is the main neurotransmitter involved in the sympathetic nervous system branch?
Noradrenaline
What is the function of the parasympathetic nervous system?
Calms body to normal state in rest and digest
Maintains body functions under ordinary conditions to save energy
What is the main neurotransmitter involved in the parasympathetic nervous system branch?
Acetylcholine
What are neurons?
Basic building block of nervous system enabling communication via electrical (within) and chemical (between) signals
What do sensory/afferent neurons do?
Carries sensory info (nerve impulses) from sensory receptors to CNS
Then translated into sensations for a reaction
Stimulates reflexes through spinal cord to motor neuron
What do relay/inter-neurons do?
Connects sensory neurons to motor neurons/other relay neurons
Transmits info from one area of CNS to another to analyse sensation + decide how to respond -> relays info to motor neuron
Where are relay neurons found?
Brain, visual system, spinal cord
What do motor/efferent neurons do?
In/voluntary motor response by sending info from CNS to effectors (eg: muscles, glands)
For reflex response, direct response from sensory info via relay neurons
When stimulated, releases NT to bind to muscle receptors for movement, strength of contraction depends on rate of neuron firing
What do dendrites do?
Carries functional info towards cell body and receives signals from other neurons
What do myelin sheaths do? Which neurons are these found in?
Protects axon and speeds up electrical transmission
Sensory + motor
What do nodes of Ranvier do?
Speeds transmission of impulse by forcing it to jump across gaps along the axon
What is another word for the cell body? What do these contain
Soma, with nucleus
What does the axon of a neuron do?
Carries nerve impulses in form of electrical signal (action potential) away from cell body to axon terminal
What does the axon terminal do?
Contains NTs and communicates with next neurons across synapse via synaptic transmission
What are the cells called along the axon of sensory/motor neurons?
Schwan cells
What are neurotransmitters?
Chemical messengers that transmit nerve impulses across the synapse
What are the 2 effects neurotransmitters can have when they bind to receptor cells on the post-synaptic neuron?
Excitatory
Inhibitory
How do excitatory neurotransmitters work?
Increases positive charge of post-synaptic neuron
Results in excitatory post-synaptic potential (EPSP)
Post-synaptic neuron more likely to fire
How do inhibitory neurotransmitters work?
Increases negative charge of post-synaptic neuron
Results in inhibitory post-synaptic potential (IPSP)
Post-synaptic neuron less likely to fire
What is 1 example of an excitatory NT?
Noradrenaline
What is 1 example of a purely inhibitory NT?
GABA
How is the neurotransmitter dopamine involved in schizophrenia/Parkinsons?
Responsible for voluntary muscle movement, attention, learning, emotion
What do neurons communicate within?
Neural networks, where each neuron separated by a synapse
Describe the process of synaptic transmission in 5 steps
- Action potential triggers presynaptic neuron to release NTs from synaptic vesicles
- NTs diffuse across synaptic cleft, carrying signal
- NTs bind to post-synaptic receptor sites on dendrite
- Summation of EPSP and IPSP determines whether action potential produces + passed on / how frequently neuron fires (net effect)
- NTs reabsorbed into presynaptic vesicles or broken down chemically by enzymes in synapse
Why can neural messages only be sent in 1 direction?
Synaptic vesicles with NTs only released from pre-synaptic membrane (high concentration)
Receptors for NTs only on post-synaptic membrane
Diffusion of NTs only from high → low concentration, so has to be pre → post
How can drugs affect synaptic transmission? (4 ways)
- Influencing amount of NT produced
- Minimising effect of natural NTs
- Influencing rate of transmission
- Blocking effect of NTs
What is the endocrine system?
Network of glands to secrete chemical messengers (hormones)
What does the endocrine system work alongside?
The nervous system regulates physiological processes at a slower rate
What are the 2 main functions of the endocrine system?
provide a chemical system of communication by secreting required amount of specific hormones from glands into bloodstream, which binds to specific receptors
Regulates activity of cells and organs in body and controls physiological processes
How is the endocrine system regulated?
Feedback, so that stable concentrations of hormones circulate in blood
What happens if there is an imbalance of hormone levels?
Dysfunction
What are glands?
Organs that secrete different hormones to regulate activity of cells and organs in body
What are hormones?
Chemical in bloodstream to target specific cells/organs, with receptors for physiological reactions
What does the hypothalamus do?
Receives info from many sources, helps regulate these functions
Links NS to ES, regulates the endocrine system via pituitary gland
What hormone does the pineal gland secrete? What is its effect?
Melatonin
Helps regulate sleep/wake cycle (important biological rhythm)
What are 3 differences between hormonal communication and neural communication?
Hormonal: hormones travel through blood to target cells BUT neural: direct electrical impulse
Hormonal: effects last longer as broken down slower BUT neural: quick
Hormonal: responses widespread/generalised BUT neural: localised
What hormone does the testes gland secrete? What is its effect?
Testosterone
Development of male physical features eg: male genitalia, facial hair, deep voice
What is the effect of the adrenal gland?
Controls sympathetic nervous system, causes physiological change associated with arousal
What are the 2 glands that make up the adrenal gland? What hormones do they secrete? What is their effect?
Adrenal medulla -> adrenaline + noradrenaline
Fight or flight response
Adrenal cortex -> cortisol
Long-term stress response, stimulates release of glucose whilst suppressing immune system
What is the fight or flight response?
Innate sequence of activity triggered when responding to threats
Acute (immediate) response, optimisies body functioning through ANS and ES working together to sustain arousal
What is the pathway where the fight or flight response occurs?
Sympathomedullary pathway (SAM)
Describe in 5 steps the fight or flight response for acute stress via the sympathomedullary pathway (SAM)
- Threat: stressor perceived and amygdala sends distress signal to hypothalamus (command centre)
- Acute: hypothalamus triggers activity in sympathetic branch, sends immediate + fast signal to adrenal medulla
- Medulla: releases adrenaline + noradrenaline, allows release of energy for immediate action
- Adrenaline: triggers physiological arousal for F/F response
- PaNS: once threat passed, body returns to resting state by reducing activity
What are the general effects of adrenaline?
Prepare the body for F/F via physiological changes
1. ↑ blood supply + oxygen to skeletal muscles (physical action)
2. ↑ oxygen to brain (rapid response planning)
What are 3 examples of the direct effects of adrenaline?
↑ heart rate (speeds blood flow for oxygen + spreads adrenaline)
Constriction of blood vessels (speeds blood flow)
Pupil dilation (improves vision)
Evaluation: what are negative consequences of F/F response?
- modern-day stresses dif to ancestors
- less physical activity so response doesn’t help with our stresses
- physiological damage to us if repeatedly activated eg: ↑ blood pressure -> vessel damage -> heart disease
No longer an adaptive mechanism, leads to illness
Evaluation: why doesn’t the F/F response explain the full story?
Initial ‘freeze’ in response to threat
- adrenaline promotes alertness/hyper-vigilent state/attention on sensory inputs
Freeze has adaptive advantage as can find new info to make best response
Evaluate: what are the gender differences in the stress response?
Tend and befriend for females
- evolved as primary caregivers so can’t leave children
- T&B protects themselves + kids through nurturing behaviours and creating alliances
- caregiver hormone oxytocin reduces F/F response
Biological basis to sex differences in stress response
What is the brain studied in terms of?
Structure (anatomy)
Function (physiology)
What are the 3 parts of the brain?
Cerebellum
Brainstem
Cerebrum (whole) / cortex (outer surface)
What does the cerebellum do?
Coordinates muscle movement
Maintains posture + balance
What does the brainstem do?
Relay centre connected brain to spinal chord
Performs many automatic functions
How thick is the cortex?
3mm
What is the cerebrum?
Largest part of human brain associated with higher brain functioning
How is the cerebrum divided?
2 hemispheres, connected by the corpus callosum (bundle of nerves)
What is the importance of the corpus callosum?
Acts as a communication pathway so hemispheres can exchange info
Important because some functions only lie in 1 hemisphere
What is the word for one side of the brain dealing with the otehr side of the body?
Contralateral
Are eyes contralateral?
Yes, but each eye has a right/left visual field, controlled by the opposite side of the brain
What is another word for localisation of function?
Cortical specialisation
How was the brain viewed historically?
Holistic theory: all parts involved in processing thought/action
Which psychologists argued for localisation in the 19th century?
Broca + Wernicke
What is localisation?
Theory that different areas of the brain are responsible for specific behaviours/processes/activity
Label the 4 lobes of the brain
A = frontal
B = parietal
C = temporal
D = occipital
What is the frontal lobe responsible for?
Personality
Behaviour
Emotions
Problem solving
Self awareness (higher order thinking)
Speech
Voluntary muscle movement
What is the parietal lobe responsible for?
Movement orientation
Recognition
Touch/pressure/pain/temperature (senses)
What is the temporal lobe responsible for?
Understanding language
Hearing
Memory
What is the occipital lobe responsible for?
Visual processing (colour/light/movement)
Label the 6 cortexs
A = Broca’s area
B = Motor cortex
C = Somatosensory cortex
D = Visual cortex
E = Wernicke’s area
F = Auditory cortex
Are all functions localised?
Some functions more localised than others eg: motor, somatosensory
Other functions more widely distributed eg: lang system in left frontal and temporal lobe
Where is the motor cortex located?
Back of frontal lobe (pre-central gyrus)
Regions logically arranged
What is the function of the 2 motor centres?
Motor cortex: complex voluntary muscle movement by sending messages to brain via brain stem and SC
Premotor cortex: plans movement prior to execution
Where is the somatosensory cortex located?
Front of parietal lobe (post-central gyrus)
What is the function of the somatosensory cortex?
Detects sensory events arising from different parts of body: amount of area devoted to particular body part denotes sensitivity
Why are the motor and somatosensory cortex close to each other? What are they seperated by?
Good communication
Central sulcus
What is the function of the visual cortex?
Retina picks up light
Nerve impulses from retina transmitted to brain via optic nerve to the visual cortex or to areas for circadian rhythms
What is the function of the auditory cortex?
Processes sound based info
Both conscious sound and auditory imagery
What are the 2 language centres of the brain located?
Lateralised to left hemisphere only
Broca’s area: posterior position of frontal lobe
Wernicke’s area: temporal lobe
What is Broca’s area important for?
Speech production and fluency
How did Broca discover his area?
Patient Tan (only word he could say) understood language but couldn’t speak or write
What is Wernicke’s area important for?
Understanding language + accessing words
Enables meaningful speech
What will happen when one has damage to the motor cortex?
Loss of control over fine movements and motor coordination
What will happen when one has damage to the somatosensory cortex?
Numbness/tingling
Hard to detect temperature
Hard to identify object by touch (tactile agnosia)
What will happen when one has damage to the visual cortex?
Blindness in opposite visual field for both eyes
What will happen when one has damage to the auditory cortex?
Hearing loss
What will happen when one has damage to Broca’s area?
Broca’s/expressive aphasia
Slow/slurred speech, lacks fluency, words not properly formed
What will happen when one has damage to Wernicke’s area?
Wernicke’s/receptive/sensory aphasia
Fluent but meaningless speech, nonsense words
What is a strength of localisation theory?
Brain scans support localisation
- Peterson et al: Broca’s active during reading task, Wenicke’s during listening task
- Tulving et al: PET scans show episodic localised to right PFC, semantic to left PRC
- objective, reliable methods with high spacial resolution
Clearly shows localisation of function
What are 2 weaknesses of localisation theory?
Higher cognitive functions holistic, not localised
- Lashley removed 10-50% of areas of cortex in rats learning a maze
- no area seen as more important to learn route: learning requires whole brain
Simple functions may be localised but strict localisation impossible as more holistic
BUT: must generalise with caution
Plasticity: when one part damaged, other take over
- EB had most of LH removed from tumour at 2 1/2, lang abilities disappeared
- RH compensated and he recovered with just mild dyslexia
Localisation/lateralisation not strictly adhered to, rather holistic brain functioning
BUT: not all brains compensate at same standard, still some localisation
What points are made for AO1 hemispheric lateralisation?
Cerebrum divided into left + right hemispheres
Joined by the corpus callosum
Brain is contralateral
What is hemispheric lateralisation?
2 hemispheres are functionally different and certain mental processes/behaviours are mainly controlled by one hemisphere
Broadly, what is the role of the left and right hemisphere?
Left: analyser
Right: synthesiser
What is the left hemisphere for?
Speech, language, comprehension processing
Analysis + calculations
Processes detail
Time and sequencing
Recognition of words/letters/numbers
What is the right hemisphere for?
Recognising emotions in others
Creativity
Processes overall patterns
Spatial relationships
Recognition of faces/places/objects
What are 2 strengths of hemispheric lateralisation?
Brain scan evidence
- Peterson et al: Broca’s area active during reading task, Wernicke’s area during a listening task
- Fink et al: PET scales RH more active when participants looked at global elements of a picture, LH more active for finer detail
High spatial resolution confirms brain processes are lateralised
Split brain patients demonstrates functional difference
- can’t name stimulus when shown to RH as lateralised to left
- can’t draw/recognise face when shown to LH as lateralised to right
Strong evidence
What is a weakness of hemispheric lateralisation?
Simplistic to assume hemispheres work in isolation
- in constant communication to form highly integrated system
- EB: RH compensated for loss of language
Cortical mapping suggests lateralisation not strictly adhered to
Who researched into split brain research?
Sperry
What was the aim of Sperry’s split brain research?
To investigate how each hemisphere specialises for certain functions
What was the sample for Sperry’s split brain research?
Those with corpus callosum removed to treat epilepsy
Control: those with a corpus callosum and without epilepsy
What was the procedure of Sperry’s split brain research?
Participants fixate on dot on screen
Image/word projected for 1/10 of a second to left/right visual field
Participants asked what they saw
What were the findings of Sperry’s research when participants were asked to describe what they see?
Could describe if disputed to RVF as language processed in left hemisphere
If on LVF, reported nothing/couldn’t describe as no language centre in right hemisphere
What were the findings of Sperry’s research for touch recognition?
Could select object from a grab bag with left hand: right hemisphere understood
What were the findings of Sperry’s research when participants were presented composite words (2 simultaneously to RVF/LVF)?
Could write/draw what was to LVF
Would say out loud what was to RVF
What was the conclusion of Sperry’s research?
Certain functions lateralised
Left = language
Right = visuospatial processing
What is a strength of research into split-brain patients?
High internal validity
- specialised + standardised + controlled procedures
- eg: image flashed for only 1/10 of a second to prevent participants moving eye to spread info to both visual fields and thus both sides of the brain
Researchers WERE measuring the extent to which the 2 hemispheres were specialised
What are 2 weaknesses of of research into split-brain patients?
May actually have low internal validity
- control had no corpus callosum AND no epilepsy
- not a valid comparison group: epilepsy acts as a CV
Hard to establish causal relationship as findings may be due to epilepsy, not split brain
Low population validity
- unique sample of 11 participants with a history of epileptic seizures
- findings based on this sample
Hard to generalise to wider population
What are 2 other terms for plasticity?
Neuroplasticity
Cortical remapping
What is plasticity?
Brain’s ability to adapt to new experiences by modifying structure and function
At what age does plasticity occur?
Throughout a lifetime
But children’s brain more adaptable: babies have 2x more synaptic connections
When are new neural connections created?
During new experiences -> brain develops
What happens if neural connections are frequently used/rarely used?
Frequently- strengthened/changed via learning
Rarely- weakened/deleted via synaptic pruning
What is functional recovery?
Form of plasticity where unaffected brain areas adapt + compensate after damage
When does functional recovery happen?
Quickly after trauma (spontaneous recovery)
Slows after time, may need rehabilitative therapy
What are 3 methods of functional recovery?
Neural unmasking: dormant synapses activate + open up connections
Axonal sprouting: growth of new nerve endings + opens up connections
recruitment of homologous areas: opposite side of brain carries out a specific task
What are 2 strengths of plasticity/functional recovery?
Clinical evidence
- EB has tumour removed at 2
- lost language abilities but RH compensated
Supports idea of plasticity + functional recovery
RW application: neurorehabilitation
- understanding of axonal sprouting allows constraint induced movement therapy
- eg for a stroke: repeated practice using affect body parts whilst unaffected constrained
Helps to have medical professionals intervention -> work, contribute to the econ
What are 2 weaknesses of plasticity/functional recovery?
Plasticity has negative behavioural consequences
- adaptation to prolonged drug use decreases cognitive functioning + increases risk of dementia
- 60-80% of amputees suffer phantom limb syndrome due to cortical reorganisation in somatosensory cortex: unpleasant painful sensations of the missing limb
Not always beneficial
Education level influences recovery rate
- Schneider et al Lund for a disability free recovery…
- 40% >16y
- 10% <12y
Some less likely to fully recover
BUT just a correlation
What are the 4 ways to study the brain?
Post-mortems
Functional magnetic resonance imaging
Electroencephalograms
Event related potentials
What are post-mortems?
Invasive procedure where brain analysed after death to determine whether certain observed behavioural changes are correlated to structural abnormalities/damage
How do post-mortems work?
Establishes neurobiological cause of rare disorders/mental processes
Compared with neurotypical brain to see differences
Who did Broca do a post-mortem on?
Tan: had lesion in an area now called Broca’s area
What is a strength of post-mortem examinations?
More detailed examination, invasive, examines deeper regions eg: hypothalamus to gain deeper understanding
What are 2 weaknesses of post-mortem examinations?
Issue of causation
- observed damage may be linked to other trauma/decay eg: time between death and PM
CVs reduce internal validity
Ethics: consent
- eg: HM
- requires special permission so decreased sample size decreases population validity
What are fMRIs?
Measures brain activity indirectly + noninvasively by detecting changes in blood oxygenation and flow from neural activity
As when brain is more active, consumes more O2 / blood flow directed to area to meet demand (haemodynamic response)
What do participants do to produce an fMRI?
Alternate between tasks to compare brain areas with matching pattern of change
Produces 3d activation maps showing which part of the brain involved in particular mental processes
What are 2 strengths of fMRIs?
High spatial resolution
- detects picture by the mm
Clear picture of localisation of brain activity
Non-invasive
- no insertion of instruments (like PM)
- no harmful radiation (like PET)
Behaviours investigated risk free
What are 2 weaknesses of fMRIs?
Poor temporal resolution
- 5 second time lag between neuron firing and image
Not truly objective, so hard to pinpoint exact areas of brain function
Expensive
- training + cost of using the machine
- decreased sample size
- picture only clear if person still
- issue for those with claustrophobia / metal devices (eg: pacemaker)
Not the most efficient way to investigate behaviour
What are EEGs?
Direct measure of tiny electrical impulses produced by the brain’s activity
What is measured in an EEG?
Electrodes on skull records general brain activity
4 brainwave patterns: alpha, beta, delta, theta
How are EEGs used as a diagnostic tool?
For arrhythmic patterns of activity (eg: epilepsy)
What are 2 strengths of EEGs?
High temporal resolution of a millisecond: accurate measure of brain activity
Cheaper = larger sample = increased population validity
What is a weakness of EEGs?
Poor spatial resolution
- generalised info cannot pinpoint exact source of neural activity
Cannot distinguish between activities originating in different, but adjacent, areas of the brain
What are ERPs?
Direct measure of very small voltage changes in the brain (electrophysiological response) triggered by specific stimuli
How are ERPs carried out?
Electrodes placed on scalp, target stimuli presented many times
Statistical averaging techniques averages EEG recording and filters out extraneous neural activity, leaving responses that relate to a specific task
What are 2 types of ERPs?
Sensory ERPs: first 100 milliseconds → initial response to stimulus
Cognitive ERPs: after 100 milliseconds → evaluation of stimulus
What are 2 strengths of ERPs?
Much more specific measure of neural processes than EEG
High temporal resolution as derived from EEG: more accurate
What are 2 weaknesses of ERPs?
Lack of methodology standardisation in research: hard to establish reliability
Hard to establish pure data
- as have to eliminate extraneous background noise
Hard to examine and needs the large trials for meaningful data
What are 6 comparison points between the brain scans?
Invasive/non-invasive
Physiology/indirect/direct measure of brain activity
Sample size
Temporal resolution
Spatial resolution
Causation
What are biological rhythms?
Regular, distinct cyclic changes in the level of bodily chemicals or activity, controlling many physiological/behavioural responses
What are biological rhythms influenced by?
Endogenous pacemakers and exogenous zeitgebers
What are the 3 types of biological rhythms?
Circadian rhythms: approx 24 hours
Infradian rhythms: more than 24 hours
Ultradian rhythms: more than once in 24 hours
What are 2 examples of circadian rhythms?
Sleep wake cycle
Core body temperature
Describe the endogenous part of the circadian sleep wake cycle
Suprachiasmatic nucleus lies above the optic chiasm and receives messages from the eyes about light levels
Sends to the pineal gland to regulate melatonin production
Describe the exogenous part of the circadian sleep wake cycle
Light entrains sleep-wake cycle by setting the body clock to the correct time: but intolerant of major alterations in schedules
Bar the suprachiasmatic nucleus and light, what else regulates the sleep wake cycle?
Homeostasis
Being awake for a long time uses energy, so homeostatic drive for sleep increases throughout the day
How does core body temperature vary throughout the day?
36ºc at 4am
38ºc at 6pm
What 2 things does core body temperature influence?
Mental abilities: warmer = higher cognitive processing
Sleep: cooler = strong sleep drive
What are 2 strengths of circadian rhythms?
Case study evidence for the free running circadian rhythm
- Siffre cave in Texas for 6 months with no exposure to natural light to entrain rhythms
- internal circadian rhythm adapted to 25 hour cycle
Rhythms naturally governed by EP, but EZ entrain to 24h cycle
BUT: lacks internal validity → used an artificial light (CV), just a case study
RW application to benefit individual and economy
- Kelley school start at 10am, results up and illness down
- surgery not planned at night as reduced concentration (circadian trough), accidents less likely
- melatonin to reduce jet lag
Educational attainment improves, helps NHS, can work after travel → boosts economy
What is a weakness of circadian rhythms?
Individual differences
- cycle varies from 13h-65h
- larks wake early sleep early
- owls wake late sleep late
- teens circadian rhythms begin 2 hours after adults
Research just shows averages, doesn’t account for innate differences: generalise with caution
What are 2 examples of infradian rhythms?
Menstrual cycle
Seasonal Affective disorder (SAD)
How long does the menstrual cycle last?
Time between first day of period and when womb lining begins to shed again
28 days (varies 24-35)
Describe the endogenous part of the menstrual cycle
Oestrogen: causes ovaries to develop + release an egg
Progesterone: helps lining grow thicker for pregnancy
If no pregnancy: egg absorbed and lining broken down → menstrual flow
Describe the exogenous part of the menstrual cycle
Synchronisation of women being together
What is seasonal affective disorder and how long does it last?
Persistent low mood + lack of interest that comes and goes in a seasonal pattern
Circannual rhythm (yearly)
Describe the endogenous and exogenous part of seasonal affective disorder?
Daylight hours are shorter (exogenous) which impacts melatonin secretion (endogenous) → affects serotonin production
What is a strength and counterpoint for infradian rhythms?
Evidence for exogenous zeitgebers in synchronisation study
- Stern + McClintock
- gathered pheromones from armpits at different stages of cycle, rubbed onto lips of other women
- 68% had a change in the cycle closer to their ‘odour donor’
Shows influence of exogenous zeitgebers on menstrual synchronisation
BUT:
- small sample of 29
- other CVs may affect cycle (stress, exercise changes)
- failed replications
What are 2 other strengths of infradian rhythms?
Synchrony explained from an evolutionary perspective
- allows women to give birth at same time
- babies who lose mums have access to breast milk, increases survival
Synchronisation is adaptive
RW application in treatment for SAD by understanding impact of melatonin on mood
- phototherapy: light box stimulates strong light in morning and evening to reset melatonin levels
- 60% had symptom reduction (although side effects eg; eye strain)
Effective treatment for most
What is the ultradian rhythm? How long does it last?
Stages of sleep
5 stages altogether 90min
Repeats 5x/night
How is each stage of the sleep cycle characterised?
By different brain activity (monitored on an EGG)
What are the 5 stages of sleep in their non-linear sequence?
What is sleep stage 1 + 2?
Light sleep
Alpha waves (high frequency, short amplitude)
Sleep spindles in stage 2 (random changes in patterns)
What is sleep stage 3 + 4?
Deep sleep
Delta waves (low frequency, high amplitude)
Rhythmic breathing and limited muscle activity
What is rapid eye movement (REM)?
Theta waves
Paralysed
Dreaming
Breathing is rapid + shallow
What is a strength of ultradian rhythms?
Improved understanding of age related sleep changes
- slow wave sleep (deep sleep) decreases with age as slow wave sleep is when growth hormones are produced
- explains issues in age eg: reduced alertness from sleep deficit
- application to increase SWS eg: meditation
Practical value
What is a weakness of ultradian rhythms?
Individual differences
- Tucker: differences in duration of stages, particularly 3/4
- differences are biologically determined
Hard to generate universal theory of normal sleep
As done in a lab: good control, but lacks external val
What is a discussion point regarding ultradian rhythms?
Further research done into the rhythm
- actually continues into the day as a 90min Basic Rest Activity Cycle (BRAC)
- hunger + loss of concentration by the end of the cycle
- actually forms a continuum with circadian rhythms
Altered understanding of ultradian rhythms
What are endogenous pacemakers?
Internal body clock that regulates the sleep wake cycle
What is the suprachiasmatic nucleus?
Bundle of nerve cells located in the hypothalamus, located above the optic chiasm
What is the optic chiasm?
Where nerve fibres connecting to eyes cross on the way to L/R visual area of the cerebral cortex (occipital lobe)
What are exogenous zeitgebers?
External factors in the environment that entrains the sleep wake cycle
What are 2 examples of exogenous zeitgebers in the SW cycle?
Light
Social cues
How is light an exogenous zeitgeber in the SW cycle?
Resents SCN
Retinal cells contain protein called melanopsin, which is sensitive to natural light, carries signals to SCN
What other bodily processes does light have an indirect effect on?
Hormone secretion
Blood circulation
What are social cues, and how are they an exogenous zeitgeber in the SW cycle?
Routines eg: mealtime, bedtime
By 15w, babies’ rhythms are entrained by schedules imposed
What are 2 strengths of endogenous pacemakers and exogenous zeitgebers in the sleep wake cycle?
Evidence for EP
- DeCoursey et al
- lesioned SCN connection in brain of 30 chipmunks
- more were killed by predators (awake making noise, so vulnerable)
Important role of SCN in SW cycle
BUT: hard to generalise as humans more complex
Practical application by resetting biological clock to avoid jetlag
- taking melatonin
- fasting before travel and eating at new time zones
People more productive when travelling → boosts economy
What are 2 weaknesses of endogenous pacemakers and exogenous zeitgebers in the sleep wake cycle?
Role of EZ overstated
- case study of a blind man: couldn’t adjust from 24.9hr cycle despite social cues
- Arctic regions have little light in winter, little darkness in summer, but Inuit people have similar sleep patterns all year round
Sleep wake cycle primarily controlled by EP, EZ not effective in resetting rhythms
Hard to study in isolation
- Siffre used artificial light, so not a total isolation study
- in real life, EP and EZ interact and work as an interactionist system
Isolation research has low validity
