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A grade Psychology Summary - Biological
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a short and detailed summary of Unit 3 Biological psychology from the edexcel board, covering every point on the specification.
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BIOLOGICAL PSYCHOLOGYCentral nervous system
● Brain : processes incoming information from senses and controls behavior resulting
from this information
● Spinal cord : extension of brain, transporting messages from to+from brain to peripheral
nervous system
● Central processing + control point for human behavior
A neuron is cell in nervous system that conducts electrical impulses and receives / transmits
messages
● Cell body : contains nucleus that houses genetic material for neuron + mitochondria to
provide energy for neuron
● Dendrites extend from cell body; receive messages from other neurons and carry
electrical impulses towards cell body
● Axon : extension of neuron that carries impulses away from cell body towards axon
terminals
● Axon hillock : at top of axon attaching to cell body; where the nerve impulse is triggered
from
● Covered by fatty layer of myelin sheath that provides an insulating layer to speed up the
rate of message transmission
, ● Breaks in between are nodes of Ranvier
Action potentials travelling down axon “jump” from node to node, speeding up
transmission
● Axon terminals + Terminal buttons at ends of neuron : pass nerve impulses from cell
body to parts of body that they control / activate
● Contain vesicles that store neurotransmitters (chemical messengers acting between
neurons)
● Gilial cells repair + remove waste products from brain
ACTION POTENTIAL
Nerve impulse (triggered by change in electrical potential of neuron ) passes down the
axon to stimulate the release of neurotransmitters
- Inside neuron : slight negative charge
Chemical message from another neuron received, stimulates either :
- excitatory postsynaptic potential, slightly depolarising the neuron and reducing
its charge = action potential fired
- inhibitory postsynaptic potential, hyperpolarising neuron, increasing its charge
= action potential not fired
More excitatory messages than inhibitory ones that are strong enough to reach neuron :
action potential triggered which sends an impulse along axon towards axon terminals
SYNAPTIC TRANSMISSION
Action potential (small electrical impulse at axon) reaches terminal button and turns
into a chemical message that is passed to other neurons across the synaptic gap (space
between dendrite - terminal button where chemical messages pass)
● Presynaptic : neuron sending message
● Postsynaptic : neuron receiving message
At axon terminal :
● Calcium channels open , flooding terminal button with Ca 2+ ions
, ● Vesicles released + travels down outer membrane of terminal button
● Vesicle fuses with membrane
● Releasing neurotransmitter into synaptic gap / cleft
● Receptors on postsynaptic neuron bind to + absorb specific neurotransmitter /
● Destroyed by enzymes in synaptic gap /
● Absorbed by presynaptic neuron (reuptake) that will be destroyed by enzymes to
turn off the neuron to prepare for future action potential
STRENGTHS
Jovanovic (2008) : synaptic transmission relates to mood by looking at serotonin system
of women with PMDD (low mood, depression) that showed differences in their serotonin
receptors compared to control group after scanning before + after ovulation
= synaptic receptors have role in PMDD
Human brain scanning produces actual brain activity + structure at work
- Scientific credibility
- Reliability : +1 person analyses scans to check results
WEAKNESSES
Simplistic explanation of how messages pass in the brain
, - Allen & Stevens (1994) : less than ½ of neurotransmitters in transmission in
hippocampus arrived from presynaptic neuron are picked up by postsynaptic
neuron = synaptic transmission is more complex
- Cause and effect : genes cause abnormal levels of neurotransmitters + exhibiting
behavior or begins when neurochemical activity changes = can’t be measured
- Evidence from lesions in animals lacks generalisability + credibility to humans as
they have consciousness and more emotional functioning
NEUROTRANSMITTERS
ACETYLCHOLINE
- Stimulates muscle contraction
- Motor control
- Attention + alertness
- Expressing anger
NORADRENALINE
- Mood control
- Sleeping, dreaming
- Learning
DOPAMINE
- Emotion
- Control of movement + posture
- Reinforcement in learning
- Dependency (addictions)
- Hormonal regulation
SEROTONIN
- Mood control in in limbic system (drives, emotions + mood)
- Feeling pain
- Regulating body temperature
- Sleep
- Hunger
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