This is a detailed and comprehensive note on introduction to brain disease, the nervous system, structure of the brain, and memory for Psy 1004F.
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Neuropsychology
Study of the function of the brain, by looking at the effects of brain damage on bodily function
Concerned with integration of psychological observations of behaviour + mind with neurological
observations of brain + nervous system.
Fairly new and rising field of psychology.
Roles of neuropsychologists
Diagnosis of neurological disease
Organic vs non-organic disease
Differentiation of normal aging
Hospital work and rehabilitation
Academic research
Private practise and medico-legal work
Causes of brain damage
Vascular strokes (brain + blood supply)
Tumours (can impact functions or cause damage upon removal)
Degenerative diseases (eg: Alzheimer’s)
Infectious diseases (eg: HIV/AIDS)
Trauma (brain injuries)
Epilepsy (transient loss of consciousness)
Diagnosis
Can infer behavioural changes from brain injuries (using scans)
Can determine brain injuries from behavioural changes
If there are physical changes in the left side of the body, it means the right hemisphere of the brain
has been effected.
Organic Disease
Observable causes in the brain of changed behaviour
Traumatic brain injury (leads to bruising and swelling)
The frontal lobe of the brain is more vulnerable
Medulla oblongata: regulates heart rate and breathing
Brain stem: controls the body’s vital functions
Degenerate brain diseases
Eg: Parkinson’s, Dementia of Alzheimer’s
Chronic Traumatic Encephalopathy (repeated concussions suffered by football players and
boxers)
Non-organic Disease
Pseudodementia: suddenly comes on due to an event. For example, depression caused by
bereavement and / or drugs.
Psychogenic non-epileptic seizures (not reflected in brain scans)
, Can be caused by: Malingering (for insurance claims, for personal gain) ; Psychological
conversion disorder (traumatic mental event reflects outwardly but not in the brain)
Types of Dementia
Dementia of Alzheimer
Vascular dementia: sudden drop in functioning, followed by a recovery. Little strokes over
time that start to compound.
Dementia with Lewy bodies
Dementia of frontotemporal lobes
Phineas Gage: a classic case
US railway worker who made a mistake when planting dynamite charge.
Blew a steel rod through his head. Showed quick recovery + no discernible cognitive damage.
BUT a complete personality change took place.
Normal aggressive behaviour etc
The Nervous System
Divided into CNS + peripheral nervous system (PNS)
Autonomic further divided into sympathetic and parasympathetic nervous systems
Controls glands, organs + involuntary muscles
- Sympathetic: activation or arousal function. Gets the body ready to deal with stress.
- Parasympathetic: slows down the body, maintains homeostasis (delicately balanced
internal state) Is normally active.
Somatic further divided into afferent (sensory) and efferent (motor) pathways
Controls skeletal muscles / voluntary movement + senses
Communication in the nervous system
Hardware
Neurons – communication
- Dendrites: receive info from other neurons
- Soma: cell body
- Axon: transmit info away
Neurons aren’t the only cells in the brain, there are also glial cells: serve as a structure on which
neurons can develop / hold neurons in place / get nutrients for neurons / insulation. Produce myelin
(fatty substance).
- Myelin sheath: speeds up transmission of electrical transmissions and insulates axon (prevents
dissipation of electrical signal). Demyelination disrupts transmission of neural impulse.
, - (axon) Terminal button: end of axon. Secretes neurotransmitters.
- Neurotransmitters: chemical messengers (serotonin, dopamine etc)
- Synapse: point at which neurons connect
Neural Impulses
Fluids both inside and outside the neuron (carry electrically charged particles / ions)
Neuron at rest: negative charge on inside compared to outside
Negative protein ions are too big to fit through ion channels in neural cell membrane.
Resting potential = -70 millivolts
Neural cell membrane is semi-permeable.
Outside neuron: positively charged.
Positively charged sodium ions outside neuron cluster around the membrane.
Difference in charges creates an electrical potential.
Neuron dendrites becomes stimulated. Membranes open.
Influx of positively charged sodium ions into the neuron.
Outside of neuron thus becomes more negatively charged, and the inside positive.
Shift in electrical charge travels along the axon.
Reversal of electrical charge is known as the Action Potential.
Sodium ion channels close as soon as the action potential has passed.
Cell membrane pumps the positive sodium ions out of the cell again.
Small positively charged potassium ions also move from inside the neuron to the outside to help
return the neuron to a negative electrical charge.
Neuron is now capable of ‘firing off’ again (dependent on sum of excitatory + inhibitory
messages received by the cell)
Action Potential follows the ‘all-or-non law’: either fires at full strength or not at all.
Absolute refractory period: the time during which another stimulus given to the neuron (no matter
how strong) will not lead to a second action potential.
Neurons receive some neurotransmitters that are aimed at causing it to fire, and others that are
aimed at preventing it from firing. The neuron adds together the effects of these messages.
A strong stimulation: will cause the neuron to fire repeatedly and causes more neurons to fire.
What happens at the synapse:
Presynaptic neuron: has synaptic vesicles containing neurotransmitters.
Postsynaptic neuron: ion channels that have receptor sites (proteins that allow only
particular molecules of a certain shape to fit into it).
Charge travels along axon to button.
Release of neurotransmitters into the synaptic cleft when electrical charge reaches the
synaptic vesicles.
Receptor sites on postsynaptic neurons only bind with corresponding neurotransmitters (lock
and key system).
This unlocks the ion channels so the positive sodium ions can enter the post-synaptic cell.
Remaining neurotransmitters either get inactivated by enzymes, drift away, or reabsorbed by
presynaptic neuron.
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