BioPsych P2 Flashcards
Divisions of the nervous system
-Human nervous system splits into the central nervous system and the peripheral nervous system.
The central nervous system is made up of brain & spinal cord
the peripheral nervous system divides into the autonomic nervous system and the somatic nervous system.
The autonomic nervous system divides into the sympathetic and parasympathetic nervous system
Features of nervous system
- Specialise network of cells
- Primary communication system
- Based on electrical and chemical signals.
- Functions: 1 - to collect, process and respond to information in the environment, 2 - to co-ordinate the working of different organs and cells in the body
CNS
-Made of brain & spinal cord
Brain: Concsious awareness, outer layer ‘cerebral cortex’ is highly developed in humans - differentiates our higher mental functions from animals, divided into two hemispheres
Spinal Cord: extension of brain, reflex actions, passes messages towards/away from brain, connects nerves to Peripheral nervous system (PNS).
Peripheral Nervous system
- Transmits messages via neurons to and from the nervous system.
- Autonomic ns: governs vital body functions such as breathing, heart rate and stress responses. Divides further into sympathetic and parasympathetic ns.
- Somatic ns: governs muscle movement and receives information from sensory receptors
Sympathetic Vs Parasympathetic
S: increases heart rate, breathing rate, dilates pupils, inhibits digestion, inhibits saliva production, contracts rectum. Responsible for Fight or Flight response.
PS: decreases heart rate, breathing rate, constricts pupils, stimulates digestion & saliva production, relaxes rectum. Responsible for Rest & Digest
Endocrine system
- Works alongside nervous system to control vital functions through action of hormones.
- More slow than nervous system - still has widespread & Powerful effects.
Glands
-organs which produce hormones
e.g. Pituitary gland aka ‘master gland’ controls the release of hormones form all other endocrine glands in the body.
Thyroid -> produces thyroxine, regulates body metabolism, brain development etc..
Pineal gland -> Produces Melatonin (sleep hormone)
Adrenal -> adrenaline
Hormones
- Secreted into bloodstream
- affect any cell in the body that has a receptor for a particular hormone
Ex. Thyrhoxine produced by thyroid affects cells in the heart and throughout body which increase metabolic rates -> increases growth rates.
Fight or Flight
- Acute stress response
- Shows endocrine and nervous system work together
SAM pathway:
Amygdala activates the hypothalamus -> activates sympathetic nervous system -> triggers adrenal medulla to release adrenaline & noradrenaline (neurotransmitter) -> facilitates the fight or flight response (increase in HR, breathing rate, dilate pupils)
HPA Axis: - chronic stress, longer lasting.
Activated by hypothalamus -> triggers pituitary gland -> release ACTH -> activates adrenal cortex which releases cortisol.
Sympathetic
- increases heart rate
- Increase breathing rate
- Dilate pupils
- Inhibits digestion
Parasympathetic
- decrease heart rate
- decreases breathing rate
- constricts pupils
- stimulates digestion
Neurons
- 100 billion nerve cells in human nervous system, 80% located in the brain
- Transmits signals electircally & chemicallly -> primary means of communication
3types of neurons; Sensory -> relay -> Motor
Sensory neurons
- carry messages from the PNS to CNS
- Long dendrites & Short axons
- Located in PNS in clusters -‘ganglias’
Relay Neurons
- connect sensory neurons to motor or other relay neurons
- Short dendrites & short axons
- 97% of neurons are relay & in the brain and visual system.
Motor Neurons
- Connect the CNS to effectors such as muscles and glands
- Short dendrites and long axons
- Cell bodies are in CNS but long axons form part of PNS
Neuron structure
- Cell body - nucleus → genetic material of cell
- Dendrites → branch like, carry nerve impulses from neighbouring nerves towards cell body
- Axon → carries electrical impulse away from cell body & down neuron: Covered in fatty layer → ‘myelin sheath’, gaps in axon → ‘nodes of ranvier’ speed up rate of transmission
- Terminal buttons → communicate with the next neuron across synapse
Electrical transmission
a neuron is resting the cell is negatively charged
When neuron activates, cell becomes positively charged → action potential occurs
Creates an electrical impulse
A Synapse
each neuron separated from the next by a tiny gap → ‘synapse’
Chemical transmission
signals across a synapse are chemically transmitted
when the electrical impulse meets end of pre synaptic neuron, it triggers release of neurotransmitters from synaptic vesicles.
Once the neurotransmitter crosses the gap, it is taken up by a post synaptic receptor site on the neuron (can only travel one direction)
Chemical message is converted back into electrical impulse → electrical transmission begins
Neurotransmitters
- chemicals which diffuse across the synapse to next neuron
- each has it’s own molecular structure which is specific, fits perfectly with receptor site (lock &key)
- Acetylcholine (ACH) found where a motor neuron meets a muscle, causes contraction
- Serotonin - mood & social behaviour, implicated as a cause of depression
Excitation & Inhabitation
Neurotransmitters can have a excitatory or inhibitory affect on next neuron
- Adrenaline - excitatory, increases positive charge, transmission will fire
- Serotonin - inhibitory, increasing negative charge, transmission is less likely to fire
- Dopamine - can be both
Summation
Excitatory and Inhibitory influences are summed up
- must reach a certain threshold for action potential to be triggered in post synaptic neuron.
- if net affect is inhibitory =less likely to fire
- if net affect is excitatory =more likely to fire
Process of synaptic transmission
- Electrical impulse travels down the neuron to the terminal buttons
- The charge in the cell becomes positive → fires action potential down to terminal button
- Vesicle sacs bind with end of terminal button to release neurotransmitters
- Triggers Neurotransmitters to diffuse across synaptic cleft.
- NT reach next neuron and bind with the receptor sites
- Produce a excitatory or inhibitory affect through summation
Localisation of the brain - area info
Motor Area - in frontal lobe, responsible for voluntary movement, in both hemisphers
Somatosensory - Parietal lobe, receives sensory info, both hemispheres, L → RH R → LH
Visual Area - occipital lobe, receives and processes visual information, L → RH, R → LH
Auditory area - temporal lobe, analyses & processes acoustic info, LE → RH, RE →LH
Broca’s area - left frontal lobe, Speech production, damage → Broca’s aphasia ( slow speech, lacking in fluency)
Wernicke’s area - left temporal lobe, language comprehension, damage → produce fluent but meaningless speech .
Localisation of function (brain)
Specific areas of brain are linked with specific physical and psychological functions, if damaged the function of area is affected.
Lateralisation = some physical and psychological functions are controlled by a particular hemisphere.
Left side, left visual field etc is controlled by right hemisphere
opposite for right side of body
cerebral cortex covers the brain, is 3mm thick and highly developed (separates us from animals) ‘gray matter’
Limitation of Localisation of functions
Language localisation models has been questioned:
- Dick & Tremblay 2016, few researchers still believe language is only in broca’s and Wernicke’s area.
Advanced techniques e.g. FMRi have identified regions in the right hemisphere and the thalamus.
This suggests that language may be organised more holistically within the brain, contradicting this theory.
Strengths of Localisation - Support form neurosurgery
-Neurosurgery is used to treat mental disorders e.g. cingulatomy involves isolating the cingulate gyrus - disfunction may cause OCD.
Dougherty 2002, studied 44 ppl with OCD who had a cingulotomy. 30% met criteria for successful response & 14% for partial response.
The success of the procedure suggests that behaviours associated with mental disorders may be localised.
Strength of localisation - brain scan evidence
Petersen 1988, used brain scans to show activity in Wernicke’s area during a listening task and in Broca’s area during a reading task.
Tulving et al - Long term memory, revealed semantic and episodic memories are located in different parts of the prefrontal cortex.
→Many sophisticated & objective methods of measuring activity in the brain, providing good scientific evidence of localisation of function.
Lashley removed areas of cortex in rats learning the route through a maze. Learning required all of the cortex rather than a particular area. This suggests that higher cognitive processes aren’t localised but distributed in a more holistic way in the brain.
Hemispheric lateralisation
the brain is lateralised e.g. 2 hemispheres
some functions are localised, appear in both hemispheres.
RH produces rudimentary words but provides emotional context, LH is the analyser, RH = synthesiser
Contralateral
in motor area, the right hemisphere controls the left side of the body
the left hemisphere controls the right side of the body.
The left visual field for both eyes is connected to the RH, the right visual field for both eyes in connected to the LH. → enables visual areas to compare the different perspective from each eye & aids depth perception. same for auditory areas.
Hemispheric lateralisation limitation
the idea of the analyser vs the synthesiser brain may be wrong.
-there may be different function in the RH and LH but research suggests ppl don’t have a more dominant side, creating a different personality.
Nielsen 2013, analysed 1000 brain scans, finding ppl used certain hemispheres for certain tasks but no dominance.
→ this suggests that the notion of right or left brained people is wrong.
Hemispheric lateralisation evaluation strength
+ (evidence of lateralised brain functions in ‘normal brains’)PET scans show when normal ppt’s attend to global elements of an image, the RH is more active. When required to focus on finer details the specific areas of LH dominate (Fink 1996).
→ This suggests that hemispheric lateralisation is a feature of the normal brain as well as split brain
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Split brain Procedure - Sperry 1968
split brain = 2 hemisphere’s surgically separated by cutting connections → corpus callosum
- treat severe epilepsy → reduce electrical storm across hemispheres
- 11 split brain ppt’s shown word/image to RVF and image shown to LVF - information couldn’t be conveyed across one hemisphere to another
Sperry 1968 findings
- Object show to RVF, ppt can describe what is seen as language centres are in LH
- Object shown to LVF: can’t name, can select matching object using left hand, can select objects associated with picture
pinup picture shown to LVF, ppt giggled but saw nothing
Sperry 1968 conclusions
-demonstrates how certain functions are lateralised in the brain, shows that LH is verbal and RH is ‘silent’ & emotional
