Biopsychology

What are the divisions of the Nervous System

human nervous system: Body wide system of nerve cells that collect information from the world, processes then takes action by directing organs and muscles via transmission of electro chemical messages.

Central nervous system: Complex processing

Spinal cord: receives and transmits, reflex processing

Sympathetic: increased heart rate, sweat breathing noradrenaline release, activates fight/flight

Homeostasis: Internal environment is balanced between sympathetic and parasympathetic systems.

Peripheral nervous system (PNS): Messenger Nerones: Sensory (afferent) and motor (efferent)

Autonomic (ANS): Controls actions of internal glands, involuntary system

Somatic (SNS): Controls skeletal muscles, voluntary system

Parasympathetic: decreased heart rate, sweat, breathing, Acetylcholine release, activates rest/digest

Structure and function of neurones

• The sensory neurone detects sensations at sensory receptors, an action potential travels along the myelinated axon.

• The electrical signal is converted into a chemical signal at the synapse.

• The relay neurone detects the signal and forms a new action potential, sending signals to both the CNS and motor neurone.

• The motor neurone detects the signal from the relay neuron (synaptic transmission) and this signal travels down its own myelinated axon

• The signal reaches an effector, this could be a muscle group in an arm (moving it away from the source of pain)

Synaptic transmission

• The synapse: located at the end of a nerve cell (neurone), it allows communication between neuron’s by transmitting chemical signals.

• Neurotransmitters: The chemical messengers released from neurones. These either make the development of an action potential in the post synaptic cell more likely to form (excitatory) or less (inhibitory).

• Process: Action potential travels down the axon of the presynaptic neuron. Vesicles release neurotransmitters into the synaptic cleft, they are detected by receptors on the post synaptic neurones membrane. Summation is the combined effect of excitatory/ post-synaptic neurone and the message has been passed on. The neurotransmitters detach from the receptors and transport proteins return the neurotransmitters to the presynaptic cell via reuptake.

The Endocrine system

• collection of glands that release hormones that regulate bodily functions and psychological factors.

• Pituitary (master gland): ACTH: controls the release of other hormones.

• Pineal: Melatonin: modulates sleep

• Pancreas: insulin: regulates sugar levels

• Testis: testosterone: secondary s*xual characteristics and linked to aggression.

• Adrenal: see fight or flight

fight or flight response

• evolutionary survival threat response

• Stressor is detected by hypothalamus, triggers the endocrine system releasing cortisol and the sympathetic ANS releasing adrenaline.

• Psychological effects of adrenaline: increased anxiety, attention and alertness. Physical: increased blood flow to brain and muscles (quick thinking/reactions), dilated pupils, increased breathing rate. decreased blood flow to skin and digestive and immune systems.

• Maladaptive to demands of the modern world.

Localisation of function in the brain

• Localisation of the function is the belief that functions of the brain are performed in distinct areas

• Hemispheric lateralisation: each hemisphere is specialised. E.g. language centres in the left and visuospatial tasks are best performed by right.

• Motor cortex: voluntary muscle movements contralateral. Damage = on opposite side… if mild: muscle weakness, if severe: paralysis on opposite side.

• Somatosensory cortex: receives sensations from opposite side of body, damage leads to a loss of sensation/numbness.

• Broca’s area: left frontal lobe only, for speech production, damage can lead to expressive apashia (difficulty producing fluent speech)

• Wernickes area: left temporal lobe only. Speech comprehension, damage can lead to receptive aphasia (difficulty understanding speech)

• Auditory cortex: In both hemispheres. Contralateral, receives and processes sound info. Damage on one side can lead to difficulty isolating locating sound, damage on both sides can lead to cortical deafness

• Visual cortex: Occipital lobe, both sides. visual processing of opposite visual field

Localisation of function in the brain AO3

• Large numbers of clinical case studies demonstrate loss of functions if damage to a particular brain location. E.g. Broca and Wernickes case studies (aphasia) and Clive Wearing (amnesia = severe damage to hippocampus)

• Modern FMRI studies support case studies using healthy brains

• The historical use of case studies in location of function research Is seen as unscientific as damage often covers multiple areas.

• There are many brain functions that appear not to be localised like consciousness and memory storage

Plasticity and functional recovery

• Plasticity: the brain adapts in function and structure due to change in the environment. Damage/learning

• Functional recovery: undamaged areas take over functions that used to be performed by damaged areas.

• Synaptic pruning: Synapses that are used frequently get stronger, unused synaptic connections are lost.

• Denervation super sensitivityL Remaining axons in a pathway become more sensitivity: Remaining axons in a pathway become more sensitive to compensate for lost axons.

• Factors affecting recovery, children and women recover better.

A03 Plasticity and functional recovery

• Maguire: MRI 16 taxi drivers who took “the knowledge” had significantly larger posterior hippocampi than controls.

• Danelli: Case study: at 2 yo, EB has a left side hemispherectomy removing Broca and Wernickes. EB recovered language ability in 2 yrs.

• Practical applications: Constraint induced therapy stopping clients using coping strategies makes them improve (functional reorganisation)
  Mathia meta analysis, not everyone has high levels of plasticity, some P’s have high levels of cognitive reserve (TQ and education are correlated)

Split brain research

• The brain is contralateral, each hemisphere controls the opposite side of the body. The hemispheres are connected by the corpus collosum. 200-300 million nerve fibres. Cutting this was a treatment for epilepsy.

• Sperry studied 11 “split brain” P’s who had a corpus callosotomy. Showing a different image to each visual. (sending info to opposite hemisphere.) P’s were asked to say what they had seen/draw/select.

• Sperry FOUND only info presented to left hemisphere could be spoken (location of the speech centre) right hemisphere could select items.

• This suggests both hemispheres are capable of independent awareness and action. Additionally language centres are on left Hem.

• Gazzanigas’s split-brain research each hemisphere shown faces. FOUND right hemisphere is specialised for facial recognition.

Split brain research AO3

• Small sample size: P’s had varying amount of connection cut and had all taken drug therapy and the control group were not epileptic.

• Experimental procedure was unusual the p’s lived normal lives, moving their heads from side to side so both hemispheres had the same visual info

• This research has had a large impact on psychology and philosophy as it challenges ideas about the unity of consciousness and identity.

Ways of studying the brain + AO3

• FMRI: detects blood flow in the brain, as more active areas need more blood they can be compared to low activation areas when P’s are doing tasks.

• Good spatial resolution (1mm), non invasive and safe

• Poor temporal resolution, one image every few seconds.

• EEG: 22-34 electrodes attached to a cap. Read out is sum of activation under the electrode. Displays brain waves

• Good temporal resolution 9ms), cheaper than FMRI

• Poor spatial resolution and can’t see deep activation

• Event-related potentials (ERP): same equipment as EEG, but presents stimulus multiple times, creating smooth curve of activation by statistical averaging (removing background noise

• Can isolate and study individual cognitive processes, good temporal resolution

• Poor spatial resolution, some processes cannot be presented multiple times.

• Post mortem examinations: Brains are precisely cut after treatment (to give firm texture). The structure of unusual brains (trauma/mental illness) are compared to healthy brains. E.g. Brocas area was identified by post mortem,

• High spatial resolution, down to microscopic brain structures/ neuronal level.

• Not on living brain so no activation, damage and behaviour is correlational

Biological rhythms - Circadian rhythms

• Circadian rhythm lasts around 24 hours (e.g. sleep/wake, release of hormones, body temperature and blood pressure) Endogenous pacemakers are internal body clocks that keep biological processes to time. Exogenous zeitgebers (EZ) are external cues that set internal body clocks.

• In the sleep wake cycle, the EP is the suprachiasmatic nucleus, when it detects light it sends a signal to the pineal gland, stopping the production of melatonin.

• Social cues and clocks may also be EZ’s.

• Siffre: lived in a cave for 6 months (no natural light). Body clock maintained a cycle of around 25 hours. Evidence for EP

• Vetter FOUND workers exposed to blue light shifted the timing of their CR, this could lead to practical applications, understanding blue lights could help

• Lights may have acted as an EZ, disrupting the EP, studies that controlled for articial light found 24 hour cycle

Biological rhythms - Infradian rhythm

• Infradian rhythm lasts longer than 24 hours (e.g. Seasonal affective disorder and the menstrual cycle.

• In the 28 day menstrual cycle the levels of hormones, oestrogen and progesterone act as EP’s. It is argued the pheromones of other women can act as EZ’s

• Stern and McClintock 20 women wiped pads from armpits of other women on their top lip (daily), lengthened/shortened their cycles to match, supporting pheromones as EZ’s.

• Trevathan: co-habiting lesbians didn’t match cycles.

Biological rhythms - Ultradian rhythm

Ultradian rhythms last less than 24 hours.

The stages of sleep: 90 mins /3-5 times per night. N1 easy to wake and sudden body movements, N2 harder to wake, body relaxed heart rate body temp decreased. N3 deepest, very difficult to wake, REM = dreams, body is paralysed (brain EEG is very active)

• Dermot and Kleitman: EEG of 33 P’s while sleeping. Brain waves followed cyclic pattern, body relaxed in low wave sleep (N3) and high activation in REM. Supports stages

• Significant individual differences newborns spend 80% of sleep in REM

• Longest part of REM sleep matches lowest point of circadian body temp cycle, they may not be different cycles but use the same EP the SCN.