psych 101 - introduction to psychology - lecture 3
DESCRIPTION
This lecture provides an overview of the physiology and complexity of the human brain and the nervous system. We will briefly examine the biological basis of behavior.TRANSCRIPT
THE BIOLOGICAL BASIS OF BEHAVIOUR
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The Human Brain
The adult brain weighs about 3 pounds.
Protected by the skull, the meninges and
cerebrospinal fluid.
The brain is soft – feels like a ripe pear.
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Neurons: The Brain’s CommunicatorsThe brain contains about 100 billion neurons,
or neural cells.There are more than 15 times as many
neurons in the brain as there are people on Earth!
Each neuron receives, processes, and transmits messages to thousands of others.
There are about 160 trillion neural connections in the human brain!
Structure of a Typical Neuron
Dendrites – the “receivers”. They receive stimulation from other neurons
Cell body – contains the nucleus and is responsible for the life processes of the cell
Axon – a long, narrow tube that carries the neural impulse toward the terminal branches.
Terminal branches/buttons - the “senders”. They contain chemicals that neurons use to communicate with each other.
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Communication Within NeuronsWhen a neuron is at rest, there is an uneven
distribution of ions across the cell membrane.There are more negative ions inside than
outside the neuron.The difference in charge is about -70
millivolts.When a neuron is sufficiently stimulated, a
tiny wave of electricity (an action potential) is generated and travels along the axon to the terminal branches.
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Communication Within NeuronsWhen an action potential occurs we can
describe it as the neuron “firing.”During an action potential, positively charged
particles flow rapidly into the neuron and then just as rapidly flow out.
Neurons can fire as rapidly as 100 to 1000 times per second!
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Communication Between Neurons• When the action potential reaches the terminal
button, it triggers the release of chemicals known as neurotransmitters into the synapse.
• The neurotransmitters bind to specific receptor sites on neighbouring neurons, stimulating them.
• Different receptor sites recognize different types of neurotransmitters.
• Communication between neurons is halted by reuptake of neurotransmitters.
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DIVISIONS OF THE NERVOUS SYSTEM
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The Divisions of the Nervous SystemThe nervous system can
be divided into two parts:
The central nervous system (CNS) - made up of the brain and spinal cord.
The peripheral nervous system (PNS) – consists of neurons that lie outside the CNS.
THE CENTRAL NERVOUS SYSTEM
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The Central Nervous SystemThe central nervous system can be divided
into different sections:Brain
Cerebral cortex Basal ganglia Limbic system Cerebellum Brain stem
Spinal cord
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The Cerebral CortexThe uppermost and largest area of the
brain is the cerebrum.The outer surface of the cerebrum is
the cerebral cortex.The cortex is divided into two halves known as cerebral hemispheres.The two hemispheres are connected by the corpus callosum.
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The Cerebral CortexThe cerebral cortex is the part of the brain
primarily responsible for processes such as thinking, remembering, planning and analyzing sensory information.
Each hemisphere of the cerebral cortex is divided into four regions called lobes:FrontalParietalTemporalOccipital
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The Cerebral CortexFrontal lobes:
Assist in movement, speech production and memory.
They oversee and organize most other brain functions.
Contain the primary motor cortex which controls movements, and the prefrontal cortex, which is responsible for thinking, planning and language.
The prefrontal cortex also contributes to mood, personality and self-awareness.
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The Cerebral CortexParietal lobes:
Contain the primary somatosensory cortex which processes information related to touch.
Integrate vision and touch
Temporal lobes:Contain the primary auditory cortex which is
responsible for hearing.Allows us to understand language.Stories memories of our past.
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The Cerebral CortexOccipital lobes:Contain the primary visual cortex, which is
responsible for vision.
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Basal GangliaA set of structures buried deep inside the
brain that help to control movement.
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Limbic SystemA set of interconnected brain regions devoted
to emotion, motivation, smell and memory.Included in the limbic system are the
amygdala and hippocampus.The amygdala plays a role in fear, anger and
excitement.The hippocampus plays a role in memory,
especially spatial memory, and helps us to convert short term memories to long term memories.
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The Brain StemConsists of several structures, including:
Reticular activating system – plays a role in arousal
Cerebellum – plays a role in balance and coordination
Pons – involved in sleep and dreamingMedulla – controls vital functions, such as
breathing, heart rate and blood pressure.
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The Spinal CordExtends from the brain stem to the lower
back.Conveys information between the brain and
the rest of the body.Made up of sensory neurons which carry
information toward the brain and motor neurons which carry motor commands from the brain to the body.
The spinal cord also consists of interneurons which connect sensory and motor neurons.
THE PERIPHERAL NERVOUS SYSTEM
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The Peripheral Nervous SystemThe peripheral nervous system is divided
into:The somatic nervous system – controls
voluntary movement.The autonomic nervous system – controls
involuntary actions of our internal organs and glands.
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The autonomic nervous system, in turn, consists of two divisions:The sympathetic nervous system – mobilizes
the fight-or-flight response.The parasympathetic nervous system – active
during rest and digestion.
The Peripheral Nervous System
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NeuroplasticityRefers to the brain’s ability to change throughout
life.Neuroplasticity occurs:1– During the early stages of life: when the
immature brain organizes itself.The network of neurons in the brain changes in
four primary ways: Growth of dendrites and axons Synaptogenesis: formation of new synapses Pruning: death of certain neurons and removal of
connections that aren’t useful. Myelination: formation of the myelin sheath
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Brain Plasticity (Neuroplasticity)2– Through adult hood: whenever something
new is learned and memorized.
3– In case of brain injury: to compensate for lost functions or maximize remaining functions.
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“If the human brain were so simple that we could understand it, we would be so simple that we couldn’t”
-Emerson Pugh, The Biological Origin of Human Values (1977)