4.Nervous system and Brain Flashcards
describe the brain vs heart debate
Historical debate sounding whether the heart or brain was responsible for central functions including thought, emotion and behaviour
describe briefly the brain hypothesis
thoughts and feelings are rooted in the brain
describe briefly the heart hypothesis
thoughts and feelings are rooted in the heart
Using specific examples, who supported the brain hypothesis
The greeks
-Alcmaeon was the first recorded person to locate the brain as the source of mental processes
-Pythagoras and Plato were also early supporters of the hypothesis
-Galen also posited the brain hypothesis through observation (most famously of pigs)
using specific examples, who supported the heart hypothesis
the egyptians
-empedocles believed that blood was the place for human cognition and thought, especially the blood around the heart’’
-aristotle also proposed that the heart was responsible for all mental functions
who ‘won’ the brain versus heart debate
thanks to empirical scientific evidence we now know that the brain is responsible for our mental functions, feelings and behaviour.
the mind body problem
The mind body problem concerns the questions of whether our mind and body are distinct separate entities or whether they are the same thing
two sides to the mind body problem
dualism
monism
dualism
The mind (non physical) and body (physical) are two distinct things but interact to produce sensations, thoughts, emotions and other conscious experience.
-descartes
monism
suggests that the mind and body are one and the same thing
Brain ablation
Brain ablation involves disabling, destroying or removing selected brain tissue, followed by an assessment of subsequent changes in behaviour
Pierre Flourens
-credited as introducing brain ablation experiments
-discrediting highly specific localisation of function and phrenology
-developed techniques of damaging or removing small areas of brain tissue to observe the effects on behaviour (used rabbits and pigeons)
-found evidence for neural plasticity (animals could eventually recover loss of movement)
Limitations of Pierre Flourens
-Imprecise surgical procedures
-did not provide detailed reports of findings
Karl Lashley
-used brain ablation on rats, monkeys and chimpanzees to find the location of learning and memory in the brain
Identify two key conclusion proposed by Lashley
Mass action
Equipotentiality
Mass action
Large areas of the brain function as a whole for complex functions
Equipotentiality
healthy part of the cortex can take over the function of the injured part (plasticity)
Moniz
-developed lobotomies
-idea that lobotomised chimpanzees became placid compared to the aggression displayed prior the surgery
lobotomy
-A form of psychosurgery to treat mental illness
-Involves scraping away (via the eye) most of the neural connections in the prefrontal cortex
Symptoms of lobotomies
-reduction in cognitive processes and behaviour
-Lack of emotional expression
-Reduction in interest and energy
-dull and lifeless personalities
Electrical stimulation of the brain (ESB) (EBS)
ESB may be done by placing electrodes on or inside a specific place on a persons head. These electrodes then send an electrical signal to that specific area of the brain, thereby stimulating the activity of neurones in that area
Key figures of ESB
-Fritsch and Hitzig
-Wilder Penfield
Penfield- Mapping the brain
-when the cerebral cortex was exposed, Penfield was able to stimulate different areas using an electrode
-Penfield used tiny numbered tags to mark areas of the cortex that he electrically stimulated as he developed his brain ‘map’.
Findings of a split brain patient
-Visual info in the L visual field is sent to the right hemisphere and vice versa
-Split brain patients were able to recognise and name images projected in the R visual field (sent to the left hemisphere-verbal)
-Split brain patients were able to recognise and detect images in the L visual field (sent to right hemisphere-non verbal) but were unable to verbalise what they saw but could draw it with their left hand
Left hemisphere function
The left hemisphere responsible for the organisation of language expression and comprehension
Why can non split brain patients recognise and verbalise visual images in both visual fields
Information processed in the right hemisphere can be transferred via the corpus callosum to the left hemisphere for language processing.
how does computerised tomography (CT) work?
-neuro-imaging technique that produces a computer enhanced image of a cross section from x rays taken at different angles
Do CT scans show brain structure or function
STRUCTURAL brain abnormalities
advantages of computerised tomography
-provides clear and accurate images
-allows for comparison between ‘normal’ and ‘abnormal’ brains
-relatively non invasive (just an injection called contrast)
what is contrast
a dye (contrast medium) used to make some tissue show more clearly. These dyes are harmless and removed from the blood via urinary system.
limitations of computerised tomography
-only shows structure not function
-pregnant women are not advised to have CT scans as there is risk radiation may cause some damage to the unborn child.
-in rare cases it is possible to have an allergic reaction to the contrast injection
how does positron emission tomography work (PET)?
-tracks blood flow by measuring the use of glucose by neurones in the active area of the brain
-radioactive material (flurodeoxyglucose) is injected into the participants bloodstream. This travels to the brain and emits various levels of radioactive signals. These are detected and processed by the PET computer to produce PET scans.
-Different colours are used to indicate different levels of brain activity
what colours represent various levels of brain activity (PET) scan
least to most activity :
violet, blue,green. yellow and red
advantages of positron emission tomography
-Displays detail colour coded images of a functioning brain
-allows researchers to see how different areas of the brain function together for certain tasks.
-colours make interpretation simple
do PET scans show brain structure or function
provide information regarding FUNCTION and ACTIVITY of brain during tasks
limitations of positron emission tomography
-requires injection (radioactive glucose)
-use of radioactivity means that longitudinal studies are difficult and dangerous
-PET scans require 40s rests between 30s scans, hence may miss rapid changes in brain function
how does magnetic resonance imaging (MRI) work?
uses magnetic fields and radio waves to vibrate the brans neurones and produce an image.
do MRI scans show brain structure or function
used to identify STRUCTURAL abnormalities
advantages of magnetic resonance imaging
-clearer and more detailed images than a CT scan
-non invasive
-no x rays or radioactivity involved
limitations of magnetic resonance imaging
-only shows structure and anatomy
-can not be used on people with internal metallic devices
how does functional magnetic resonance imaging work?
-uses magnetic fields and radio waves to vibrate the brains neurones and produce an image
-detects changes in oxygen levels and blood to show level of functioning neurones
do fMRi scans show brain structure or function
brain FUNCTION
advantages of functional magnetic resonance imaging
-no exposure to radiation
-detailed images of brain functioning
-shows a combination of brain structure and function
-detects changes in function in rapid succession
limitations of functional magnetic resonance imaging
-expensive and limited access
-can not be used on people with internal metallic devices
how does an electroencephalograph (EEG) work
detects, amplifies and records general patterns of electrical activity within the brain
-electrodes are placed along the scalp
does an EEG show brain structure or function
function
advantages of an electroencephalograph
-provides overall information about the brain without being invasive
-used to study patterns of activity over long periods of time eg sleep
-it shows different brain waves for different activity and is useful to study hemispheric specialisation
limitations of an electroencephalograph
-doesn’t provide detailed information regarding structures of the brain
-difficult to pin point specific areas of activity
-unable to distinguish a response from ‘background noise’ neural activity
-only provides a summary of neural activity
what is the central NS composed of
-composed of the brain and spinal chord
Central NS function
-processes sensory information to activate appropriate actions
spinal chord function
-connects the brain to the rest of the body
-send information from sensory neurones in various parts of the body to the brain
-relays motor commands back to muscles and organs via motor neurones
what does the Peripheral NS consist of
The peripheral NS consists of all the nerves outside the Central NS (ie brain and spinal chord)
Peripheral NS function
The Peripheral NS carries sensory information from the body to the Central NS, and motor information from the Central NS to the body
subdivisions of the Peripheral NS
Somatic NS
Autonomic NS
Two major divisions of the Nervous System
Central NS
Peripheral NS
Function of the Somatic NS
-The somatic NS transmits sensory information to the CNS and carries out its motor commands
-The somatic NS is involved in voluntary muscle movements
other name for somatic NS
voluntary nervous sytem
subdivisions of the somatic NS
sensory information and voluntary skeletal muscles
Function of autonomic NS
-responsible for AUTOMATIC responses
-carries information to internal bodily structures (eg heart, lungs and glands) that carry out basic life functions
-responsible for any life giving responses eg pumping blood
subdivisions of the Autonomic NS
Sympathetic and Parasympathetic NS
Function of Sympathetic NS
-readies the body for a fight or flight response when exposed to threats
-instantaneous reaction
-short term
-speedy/rapid
-involuntary
physiological changes by the Sympathetic NS
-slows digestion
-increases Heart rate
-dilates pupils
-diverts blood away from the stomach to muscles (which may need it more)
-decreased bladder control
Function of Parasympathetic NS
-supports more routine activities that maintains the bodys store of energy (eg regulating blood glucose levels)
-once a threat has passed the parasympathetic NS resumes control from the sympathetic NS
physiological changes by the parasympathetic NS
-Heart rate lowers
-Increased digestion
-blood pressure lowers
-stop sweating
-bladder control increases
-pupils constrict
subdivisions of the central NS
brain and spinal chord
what is the neural message within neurones
electrical impulse
what is the neural message between neurones
chemical messages (neurotransmitters)
dendrite function
receive input from other neurones
cell body/soma function
includes a nucleus which controls the neurone
axon function
transmits information to other neurones
myelin sheath function
-‘fatty covering’ that insulates the axon from chemical and physical stimuli that might interfere with the transmission of nerve impulses
-helps in speeding up the neural impulse
terminal buttons function
sends signals from a neurone to adjacent cells (release neurotransmitters)
synapse function
the space between neurones where transmission occurs
axon terminals function
branch like extensions from the axon that carries message to terminal buttons
another name for terminal buttons
synaptic knobs
difference between synapse and synaptic gap
synapse-pre synaptic terminal buttons + synaptic gaps + post synaptic dendritic spines
whereas
synaptic gap-only the gap
identify types of neurones
sensory neurons
interneurons
motor neurons
sensory/? neurons
sensory/ afferent neurons
motor/? neurons
motor/ efferent neurons
where are sensory neurones found
PNS
where are motor neurones found
in the lower brainstem and spinal chord
where are interneurons found
CNS (only)
what do sensory/afferent neurones do
-transmit information from sensory cells in the body (called receptors) to the brain (either directly or by the way of the spinal chord)
-sense the external world and monitor changes within our bodies
-some sensory neurones transit information directly to the spinal chord whereas others transmit info to the brain via the spinal chord
-sensory neurones have specialised functions depending on where they are found
what do motor/efferent neurones do
-also called effectors and motor neurones
-carry messages from the CNS to cells in skeletal muscles, organs and glands to simulate activity
what do interneurons do
-act as a link between sensory and motor neurones, relaying information from one neurone to another (this is because sensory and motor neurones are rarely directly connected)
-enable simple reflexes in spinal chord and complex functions in the brain
what do glial cells do
provide the structural framework that enable a network of neurones to remain connected
identify CNS glial cells
Astrocytes
Microglia
Oligodendroglia
identify PNS glial cells
Schwann cells
satellite cells
astrocytes functions
Provide physical and nutritional support for CNS neurones