Biopsychology

structure of the nervous system

central nervous system

• brain

• spinal cord

coordinator of everything

receives information from the environment

processes, makes decisions and makes these actually happen

• brain: decision maker

• spinal cord: major connection to the peripheral. does reflex actions

peripheral nervous system

millions of neurons transmit messages to and from the CNS

then subdivided into the autonomic and the somatic

somatic nervous system

voluntary, conscious, deliberate actions

muscle coordination and info from sensory receptors

autonomic nervous system

involuntary, unconscious actions

e.g. breathing, HR, digestion

sympathetic and parasympathetic (antagonistic pair)

sympathetic

gut: slows digestion

salivary glands: inhibits production

heart: increases rate

eye: dilates pupil

lungs: dilates bronchi

parasympathetic

increases digestion

increases saliva

decreases HR

constricts pupil

constrict bronchi

flight or fight response

1. the hypothalamus identifies a threat and instructs the sympathetic system to act.

2. stress hormone adrenaline is released from the adrenal glands into the blood stream

3. adrenaline prompts a number of physical changes in the body to prepare for fight or flight

4. following the fight or flight response the parasympathetic nervous system is activated to return the body back to a normal resting rate e.g. slows HR, breathing rate, reduces blood pressure

evaluating the fight or flight response

useful in evolutionary terms. when we need energy to deal with the situation it prepares us to have the energy to run away or stay and fight.

→ not useful for stressers that do not require physical activity e.g. modern ones like debt. these bodily changes can be unhelpful and lead to illness.

research in this area of flight and fight is gender biased (alpha- androcentric). the research is only done on male Ps then generalised to females as well. females are more likely to show tend and befriend response. produces less adrenaline so gather together and support more. 

the endocrine system (glands and their use)

• pituitary

• thyroid

• adrenal

• ovaries

works alongside the nervous system to control glands which release hormones into the bloodstream.

→ pituitary (base of brain under hypothalamus)

• stimulated other endocrine glands e.g. controls growth, blood pressure, water levels

• oxytocin (childbirth and breastfeeding), vasopressin (balances salt and water)

- thyroid (front of neck)

• controls speed of metabolism,breathing, temperature, brain development

• thyroxine

- adrenal (top of kidneys)

• regulates metabolism, blood pressure, development of sexual characteristics

• cortisol: controls body’s use of fats, proteins, carbs and the blood pressure

• adrenaline: flight or fight- increases HR etc

- ovaries (either side of uterus)

• produces and stores eggs

• oestrogen- breasts, wide hips, thickens uterine lining

• progesterone- thickens uterine linings, breasts to produce milk

types of neurons

sensory: carries messages from PNS to CNS. long dendrites and short axons.

relay: connect sensory to motor (or other relay). short dendrites and short axons

motor: connect CNS to affects like muscles and glands. short dendrites and long axons

structure of a neuron

cell body with nucleus that contains genetic material

dendrites → axon → terminal buttons

myelin sheath protects and speeds up impulse. has nodes of ranvier to force it to ‘jump’

reflex arc 

uses relay neurons in spinal cord to produce automatic response to environmental issues which need a quick response e.g. moving hand from heat

1. detected by sense organs in PNS which convey message along sensory neuron

2. message researches CNS → relay neuron → motor neuron

3. then carries messages to effectors such as a muscle

electrical transmission (done within neurons)

in a resting state the inside of the neuron is negatively charged compared to the outside

when activated by a stimulus, the inside becomes positively charged for a split second causing an action potential to occur creating an electrical impulse

this travels down the axon towards the end of the neuron (and triggers the release of neurotransmitters)

chemical transmission (done between neurons)

each neuron is separated from the next by a tiny gap called a synapse

signals between neurons are transmitted chemically

• neurotransmitters are released from tiny sacs called synaptic vesicles.

• they mostly diffuse across the synapse to the next neuron

• (or are broken down by enzymes or reabsorbed into vesicles)

• once a neurotransmitter crosses the gap it is taken up by the receptor sites and converted back into electrical impulses.

• each neurotransmitter has its own specific molecular structure that fits to receptor site (lock and key)

  

excitation

neurotransmitter increases the positive charge of the post synaptic neuron which increases the likelihood that the post synaptic neuron will pass on the electrical impulse e.g. adrenaline

inhibition

neurotransmitter increases the negative charge of the post synaptic neuron which decreases the likelihood that the post synaptic neuron will pass on the electrical impulse e.g. serotonin

summation

whether a postsynaptic neuron fires

• sum of excitatory and inhibitory influences

• net effect either excitatory or inhibitory

Localisation

specific areas of the brain are associated with particular physical and psychological functions (rather than holistic- the brain working as a whole)

Lateralisation

dominance of one hemisphere of the brain for particular physical and psychological functions e.g. language areas are only found on the left. (mostly 2 hemispheres are quite similar)

3 concentric layers

1. central core

Central core/ brain stem

• regulated most primitive and involuntary behaviours e.g. breathing, sleeping, sneezing

• includes structures like the hypothalamus in the mid brain

• regulates eating, drinking and the endocrine system to maintain homeostasis (how the body keeps a constant physiological state)

3 concentric layers

2. limbic system

• controls our emotions

• interconnected with the hypothalamus

• contains structures like hippocampus which is associated with memory

3 concentric layers

3. cerebrum

• regulates our higher intellectual processes

• outermost layer, cerebral cortex: appears grey due to location of cell bodies ‘ grey matter’

• each sensory system sends messages to and from cerebral cortex

• middle of left and right hemispheres connected by corpus callosum: can convey messages to both left and right

• each hemisphere then further divided into four lobes

temporal lobe

• auditory

location for auditory ability and memory acquisition

auditory centres

1. cochlea: sound waves converted to nerve impulses

2. auditory nerve

3. brain stem- decodes duration and intensity of sound

4. thalamus- further processing

5. auditory cortex- recognises and generates an appropriate response

Occipital lobe

• visual

location for vision

1. light enters and strikes photoreceptors (rods and cones) in retina

2. nerve impulses to optic nerve

3. nerve impulses to thalamus

• some to other areas to coordinate circadian rhythms

4. visual cortex- contains areas that process different types of visual information such as colour, shape and movement. 

right receives input from left hand side of the visual field and vice versa

Parietal lobe

• somatosensory

location for sensory information and coordination

somatosensory cortex: detects sensory events from different regions in the body. uses sensory information from the skin to produce sensations such as touch, pressure and pain.

cortex on one side of the brain receives information from opposite side of the body

Frontal lobe

• Motor

awareness of interactions with environment, consciousness and motor cortex

motor cortex: responsible for voluntary motor movements. in the right hemisphere the cortex controls muscles on left and vice versa. different parts control different parts of the body, and is arrange logically (part that controls foot near part that control leg)

• damage to this area results in impaired movements

Language centres

• Broca’s

Paul Broca, French Neurosurgeon

• treated a patient who was only able to say ‘tan’ but did understand language

• also studied 8 other patients who h\d similar language deficits along with lesions in their left frontal hemisphere (people with damage on right did not have the same issues)

• identified language centres in back portion on left frontal lobe that is critical for speech production

near where the mouth, tongue and vocal cords are controlled

Neuroscientists found when people do cognitive tasks (unrelated to language) their Broca’s area is active 

• Federonka: 1 part involved in language and 2 responds to demanding cognitive tasks like maths problems

Language centres

• Wernicke’s

German neurologist

• back left temporal lobe

• patient with legion’s on Wernicke’s area could speak but could not understand language

• sensory area- responsible for auditory and visual input processing

neural loop runs between Wernicke’s and Broca’s

Evaluating localisation of the brain

evidence from neurosurgery- damage to areas of brain linked to mental disorders

• neurosurgery treats mental disorders by targeting specific areas of the brain that may be involved.

• DOUGHERTY: 44 people who had had cingulotomy (isolate cingulate gyrus involved in OCD) after 32 weeks: 30% had successful response, 14% partial response

• behaviours in mental disorders are localised.

evidence from brain scans. 

• PETERSON: used brain scans to demonstrate how Wernicke’s area was active during listening task and Broca’s during a reading task. 

• BRACKNER + PETERSON: semantic and episodic memories reside in different parts of the prefrontal cortex. 

• confirms localised areas for everyday behaviours. 

→ LASHLEY: removed areas of cortex (10%-50%) in rats learning route through maze. no area was proven to be more important than any other area in terms of rat’s ability to learn the route. more about the process of learning and needing more of the cortex. more holistic as emphasises involvement of the whole brain. 

When the brain has been damaged and a function has been impacted the rest of the brain helps to recover it. Law of equipotentiality- surviving brain circuits chip in so the same function can be achieved e.g. stroke victim’s recovery- learning relies on the whole brain. 

Language not just localised to Broca’s and Wernicke’s area

• only 2% of researchers believe it is completely controlled by these areas.

• advances in brain imaging e.g, fMRI means neural processes can be studied with more clarity.

• language function distributed more holistically in brain e.g. language streams across cortex- brain regions in right hemisphere, thalamus. 

• holistic so contradicts localisation

lateralisation

and how stimuli is processed

the 2 hemispheres of the brain are functionally different and certain mental processes and behaviours are mainly controlled by 1 hemisphere rather than the other

→ most stimuli is processed contralaterally meaning if stimuli enters on the left it is processed in the right hemisphere and vice versa. 

analyser and synthesiser for language

analyser: left is dominant in language e.g. broca’s and wernicke’s 

synthesiser: right hemisphere can only produce basic words and phrases but provides emotional context.

commissurotomy

the corpus callosum is severed

• often for people with severe epilepsy 

• the main communication line between each hemisphere is removed

• so the information can not be conveyed from 1 hemisphere to the other. (cannot generate whole picture)

split brain research, sperry

image usually projected on Ps right visual field is processed by the left hemisphere and then vice versa.

for people with a commissurotomy the information cannot be conveyed between each hemisphere.

therefore sperry could see extent to which 2 hemisphere were specialised for certain functions and whether the hemispheres performed certain tasks individually. 

→ investigated hemispheric lateralisation with 11 split brain patients

Sperry’s research methods 

• describe what you see

• recognition by touch

describe what you see

• picture presented to the left visual field (processed by right): patient COULD NOT describe what was shown or said nothing was present. 

• picture presented to the right visual field (processed by left); patient COULD describe what they saw. 

recognition by touch

• object placed in the left hand (processed by right): COULD NOT describe what they felt but could identify by selecting similar appropriate object from a group of objects. 

• object placed in right hand (processed by left): COULD describe what they felt and could also identify object by selecting similar appropriate objects from a group of objects. 

evaluating sperry’s research

even in connected brains the 2 hemispheres process information differently

• FINK: used PET scans to identify which brain areas were active in visual processing task

• Ps were asked to look at big elements of an image (e.g. whole forest) and right hemisphere was much more active.

• when focusing on finer details (e.g. individual trees), specific areas of the left hemisphere were more dominant

→ for visual processing, there is lateralisation

scientific methodology due to high control: presented visual stimulus for short amount of time to ensure only one hemisphere was receiving at a time high internal validity.

lacking generalisability as Ps were compared to neurological control group where none had epilepsy. this is a major confounding variable as differences/ cognitive abilities may be due to epilepsy not split brain

there is an exaggerated difference between hemispheres, when a situation requires it e.g. damage from illness or trauma, function can be effectively performed by another hemisphere (plasticity)