Chapter 2: BRAIN, BODY, AND BEHAVIOUR

THE BIOLOGICAL BASIS OF BEHAVIOUR

www.whatispsychology.biz1The Human BrainThe adult brain weighs about 3 pounds.

Protected by the skull, the meninges and cerebrospinal fluid.The brain is soft feels like a ripe pear.

www.whatispsychology.bizNeurons: The Brains 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!

www.whatispsychology.biz3Structure of a Typical Neuron

Dendrites the receivers. They receive stimulation from other neuronsCell body contains the nucleus and is responsible for the life processes of the cellAxon 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.www.whatispsychology.bizCommunication 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.

www.whatispsychology.bizCommunication 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 NeuronsWhen 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.www.whatispsychology.biz7

www.whatispsychology.bizDIVISIONS OF THE NERVOUS SYSTEM www.whatispsychology.bizThe 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.

www.whatispsychology.bizTHE CENTRAL NERVOUS SYSTEM www.whatispsychology.bizThe Central Nervous SystemThe central nervous system can be divided into different sections:BrainCerebral cortexBasal gangliaLimbic systemCerebellumBrain stemSpinal cordwww.whatispsychology.bizThe 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.

www.whatispsychology.bizThe 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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www.whatispsychology.bizThe 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.www.whatispsychology.bizThe 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.www.whatispsychology.bizThe Cerebral CortexOccipital lobes:Contain the primary visual cortex, which is responsible for vision.www.whatispsychology.bizBasal GangliaA set of structures buried deep inside the brain that help to control movement.

www.whatispsychology.bizLimbic 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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www.whatispsychology.bizThe Brain StemConsists of several structures, including:Reticular activating system plays a role in arousalCerebellum plays a role in balance and coordinationPons involved in sleep and dreamingMedulla controls vital functions, such as breathing, heart rate and blood pressure.

www.whatispsychology.bizThe 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.www.whatispsychology.bizTHE PERIPHERAL NERVOUS SYSTEM www.whatispsychology.bizThe 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.www.whatispsychology.bizThe 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 Systemwww.whatispsychology.bizNeuroplasticityRefers to the brains 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 axonsSynaptogenesis: formation of new synapsesPruning: death of certain neurons and removal of connections that arent useful.Myelination: formation of the myelin sheath

www.whatispsychology.bizBrain Plasticity (Neuroplasticity)2 Through adulthood: whenever something new is learned and memorized.

3 In case of brain injury: to compensate for lost functions or maximize remaining functions.

www.whatispsychology.bizIf the human brain were so simple that we could understand it, we would be so simple that we couldnt

-Emerson Pugh, The Biological Origin of Human Values (1977)

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