The Brain and The Nervous System Flashcards
List the approaches over time to understanding the role of the brain
Brain versus heart debate
Mind-body Problem
Phrenology
Brain versus Heart Debate
Is our brain or our heart the source of all our thoughts, feelings and behaviours?
Brain Hypothesis
Thoughts and feelings are rooted in the brain
Alcmaeon = first person to locate brain as the source of mental processes (experiments on animals and location of optic nerve)
Galen = treated head injuries of gladiators = determined that the brain was at the centre of mental processes
Heart Hypothesis
Thoughts and feelings are rooted in the heart
Egyptians = believed that the heart held the mind and the brain had no relevance (heart remained in body and brain was removed and discarded)
Empedocles = blood was the means in which we all think and feel. Heart pumps blood around body therefore the centre of mental processes
Mind-body Problem
concerns the question of whether our mind and body are distinct and separate entities or whether they are the same thing
relates to whether or not the mind (soul or non physical entity) is linked to the body or if it is separate
List the two sides of the Mind-Body Problem debate
Dualism
Monism
Dualism
Suggests the mind (non physical) and body (physical) are two distinct and distinguishable entities but interact to produce sensations, thoughts, emotions and other conscious experiences
Monism
Suggests that the mind and body are one and the same
Cartesian/Descartes’ Dualism
Suggests that we are composed of two separate substances: the physical and the mental (which includes the mind and the soul)
Phrenology
Gall’s phrenology explored the relationship between the skull’s surface features and an individual’s personality characteristics
based on anecdotal evidence = pseudoscience
legacy = localising particular functions to certain parts of the brain
Brain Ablation Experiments
Brain Ablation involves disabling, destroying or removed selected brain tissue, followed by an assessment of subsequent changes in behaviour
For obvious reasons, experiments using brain ablation are considered unethical on humans (causes irreversible brain damage)
Key Figures in Brain Ablation Experiments
Pierre Flourens
Karl Lashley
Moniz
Brain Ablation - Pierre Flourens
Developed techniques of damaging or removing small areas of brain tissue to observe the effects on behaviour
Found evidence for neural plasticity
Limitations = imprecise surgical procedure, not detailed report of findings
Brain Ablation - Karl Lashley
Used brain ablation on rats, monkeys and chimpanzees to find the location of learning and memory in the brain
Failed to produce amnesia of recently learned tasks
What were the two proposed conclusions of Lashley’s research
Mass Action - large areas of the brain function as a whole for complex functions (if part of the brain is destroyed, loss of function will depend on amount of destroyed cortex)
Equipotentiality - healthy part of the cortex can take over the function of an injured part (plasticity)
Moniz
Developed lobotomies - form of psychosurgery to treat mental illnesses
Involves scraping away (via the eyes) most of the connections in the prefrontal cortex
Consequences of Moniz surgeries
Reduction in cognitive processes and behaviour
Lack of emotional expression
Reduction in interest and energy
Personalities appeared dull and lifeless
Electrical Stimulation of the Brain
Electrodu\es on or inside a person’s head send an electrical signal to specific part of brain and stimulate the activity of neurons in that area, which causes behaviour to be made
Inferences made about what different areas of the brain do based on how they respond to stimulation
Assumption = if electrical stimulation of a particular brain region triggers a response, that region is involved in that function
Key Figures involved in EBS
Fritsch and Hitzig (discovered contralateral control of limb movement)
Wilder Penfield
Penfield - Mapping the Brain
When the cerebral cortex was exposed, Penfield was able to stimulate different areas of the brain using an electrode and asking his patients to report their experiences
Penfield used tiny numbered tags to mark the areas of the cortex that he electrically stimulated as he developed his brain map. Then he recorded the responses of his awake and alert patients.
Split Brain Experiments
Split Brain Surgery involves cutting the band of nerve tissues (corpus callosum) connecting the two hemispheres
Disconnecting the two hemispheres reduces the severity of seizures
Testing a Split Brain
Participants were asked to focus on the dot and images were flashed to the left or the right
Visual info in the left visual field is sent to the right hemisphere and vice versa
Split brain patients could recognise and name images projected in the right visual field but could not when the image was presented in the left visual field
Participants were able to locate the pencil with their left hand despite not being able to verbalise what they saw
Sperry and Gazzangiga Results
The left hemisphere is responsible for the organisation of language expression and comprehension and when images are not processed in this hemisphere, they cannot be verbally stated
This is bc info processed in the right hemisphere could not be transferred to the left hemisphere via the corpus collosum
The right hemisphere is involved in language comprehension and the left hemisphere is dominant in language expression
What does CT stand for
Computerised Tomography
What does a CT do
Neuroimaging technique that produces a computer enhanced image of a cross section from x-rays taken at different angles
Used to locate structural brain abnormalities
What is contrast
A dye that may be used to make some tissues show up more clearly. These dyes are harmlessly removed from the blood by the kidney and passed out in the urine
Advantages of a CT scan
- provides clear and accurate images
- allows for comparison between ‘normal’ and ‘abnormal’ brains
- relatively non invasive (only contrast injection)
Limitations of a CT scan
- only shows brain structure not function
- pregnant women advised not to as radiation can cause some damage to unborn child
- rarely, it is possible to have an allergic reaction to the contrast injection
What does PET stand for
Positron Emission Tomography
What does a PET scan do
- provides info regarding the function and activity of brain during tasks
- tracks blood flow by measuring the use of glucose by neurons in the active area of hte brain
- flurodeoxyglucose is injected into blood stream, travels to brain and emits radioactive signals that are detected and processed
- different colours are used to indicate different levels of brain activity (easy to interpret)
- least to most activity colours :violet, blue, green, yellow, red
Advantages of a PET scan
- displays detailed, colour coded images of a functioning brain
- allows researcher to see how different areas of the brain function together for certain tasks
- colours make interpretation simple
Limitations of a PET scan
- requires injection (radioactive glucose)
- use of radio activity means that longitudinal studies are difficult and dangerous
- PET scans need 40sec rest between each 30sec scan so can miss rapid changes in brain function
What does a MRI stand for
Magnetic Resonance Imaging
What does an MRI do
Uses magnetic fields and radio waves to vibrate the brains neurons and produce an image
Primarily used for identifying structural abnormalities
Advantages of a MRI scan
- clearer and more detailed images than a CT scan
- non-invasive
- no x-rays or radio activity involved
Limitations of a MRI scan
- only shows structure and anatomy, not function
- cannot be used on people with internal metallic devices
What does a fMRI stand for
Functional Magnetic Resonance Imaging
What does a fMRI scan do
Detects changes in oxygen levels and blood to show brain function
Technique is like a standard MRI but blood and oxygen flow are recorded to show level of functioning of neurons
Colour changes indicate activity levels whilst performing a task
Applied in hemispheric specialisation studies
Advantages of a fMRI scan
- no exposure to radiation
- detailed images of brain functioning
- combination of structure and function
- detect changes in function in rapid succession
Limitations of a fMRI scan
- expensive and limited access
- cannot be used on people with internal metallic devices
What does an EEG stand for
Electroencephalograph
What does an EEG scan do
Detects, amplifies and records general patterns of electrical activity within the brain
Electrodes placed along the scalp
Advantages of an EEG scan
- provides overall info about brain without being invasive
- used to study patterns of activity over a long length of time (eg. while sleeping)
- it shows different brain waves for different activity and useful for studying hemispheric specialisation
Limitations of an EEG scan
- doesnt provide detailed info 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
The Nervous System
The human nervous system is a hierarchical structure that reacts to changes both outside and inside the body. It receives and processes sensory information form the environment and transmits motor information around the body, that, in turn, determines our reaction to environmental stimuli
Draw the diagram of the Divisions of the Nervous System
Refer to notes when correcting
The Central Nervous System
Is composed of the brain and spinal cord. It processes sensory information to activate appropriate actions
The spinal cord connects the brain to the rest of the body
State the 2 functions the spinal cord serves
It sends information from sensory neurons in various parts of the body to the brain
It relays motor commands (actions/change) back to muscles and organs via motor neurons
This process occurs extremely rapidly and continuously
The Peripheral Nervous System
Is connected to the spinal cord and consists of all the nerves outside the CNS (brain and spinal cord)
It carries sensory info from the body to the CNS and motor info from the CNS to the body
Consists of the Somatic NS and the Autonomic NS
The Somatic Nervous System
Transmits sensory info to the CNS and carries out its motor commands
The Somatic NS is involved in voluntary muscle movements so it is often called the ‘voluntary nervous system’
Two components: Sensory information (Afferent), Voluntary Skeletal Muscles (Efferent)
The Autonomic Nervous System
Is responsible for Automatic responses (life-giving responses) (breathing is the exception)
It carries info to internal bodily structures (eg. heart, lungs, glands) that carry out basic life functions
Divided into two main systems: Sympathetic NS (Fight/flight response) and Parasympathetic NS (Homeostasis)
The Sympathetic Nervous System
Readies the body for the fight or flight response when its exposed to threats
Sympathetic is speedy - fast reaction, instantaneous, short term
List four examples of the Sympathetic Nervous System
Dilates pupils
Increases heart rate
Relaxes bronchi
Slows digestion
The Parasympathetic Nervous System
Supports more routine activities that maintain the body’s store of energy
When a threat has passed, the parasympathetic NS resumes control from the Sympathetic NS
List four examples of the Parasympathetic Nervous System
Heart rate decreases
Pupils constrict
Digestion increases
Blood pressure lowers
Neurons
Carry info/ messages in the form of an electrical impulse to the appropriate part of the nervous system. They also assist the brain in interpreting messages that they have received to enable a motor response
List the components of a neuron
Dendrites Cell Body/Soma Axon Myelin Sheath Terminal Buttons/ Synaptic Knobs Synapse Axon Terminals
Dendrites
Receive input from other neurons
Cell Body/Soma
Includes a nucleus which controls the neuron
Axon
Transmits information to other neurons
Myelin Sheath
‘fatty covering’ that insulates the axon from chemical and physical stimuli that might interfere with the transmission of neural impulses and increase the speed of transmission
Terminal Buttons/Synaptic Knobs
Send signals from a neuron to adjacent cells (release neurotransmitters)
Synapse
The space between neurons where transmission occurs
Includes pre-synaptic terminal buttons, synaptic gap, post-synaptic dendritic spines/receptor sites
Axon Terminals
Branch-like extensions from the axon that carries message to terminal button
Neural Messages
Within neurons = electrical impulse
Between neurons = chemical messages (neurotransmitters)
Draw a neuron
Correct using workbook
List the types of neurons
Sensory/Afferent Neurons - PNS
Interneurons - CNS
Motor/Efferent Neurons - PNS
Sensory/ Afferent Neurons
Transmit info from sensory cells in the body (called receptors) to the brain (either directly or by the way of the spinal cord)
Main role = sense the external world and monitor changes within our bodies
There are different types of sensory neurons, specialised to respond to a particular stimulation