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Psych 101 - Introduction to Psychology - Lecture 3


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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.

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Psych 101 - Introduction to Psychology - Lecture 3

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  2. 2. The Human Brain The adult brain weighs about 3 pounds. The brain is soft – feels like a ripe pear. Protected by the skull, the meninges and cerebrospinal
  3. 3. Neurons: The Brain’s Communicators The 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!
  4. 4. Structure of a Typical Neuron – the “receivers”. They receive stimulation from other neurons – contains the nucleus and is responsible for the life processes of the cell – a long, narrow tube that carriesthe neural impulse toward the terminalbranches. - the “senders”. They contain chemicals that neurons use to communicate with each other.
  5. 5. Communication Within Neurons When 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.
  6. 6. Communication Within Neurons When 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!
  7. 7. 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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  10. 10. The Divisions of the Nervous System The 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.
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  12. 12. The Central Nervous System The central nervous system can be divided into different sections:  Brain  Cerebral cortex  Basal ganglia  Limbic system  Cerebellum  Brain stem  Spinal cord
  13. 13. The Cerebral Cortex The 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.
  14. 14. The Cerebral Cortex The 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:  Frontal  Parietal  Temporal  Occipital
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  16. 16. The Cerebral Cortex Frontal 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.
  17. 17. The Cerebral Cortex Parietal 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.
  18. 18. The Cerebral Cortex Occipital lobes: Contain the primary visual cortex, which is responsible for vision.
  19. 19. Basal Ganglia A set of structures buried deep inside the brain that help to control movement.
  20. 20. Limbic System A 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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  22. 22. The Brain Stem Consists 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 dreaming  Medulla – controls vital functions, such as breathing, heart rate and blood pressure.
  23. 23. The Spinal Cord Extends 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.
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  25. 25. The Peripheral Nervous System The 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.
  26. 26. The Peripheral Nervous System 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.
  27. 27. Neuroplasticity Refers 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
  28. 28. 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.
  29. 29. “If the human brain were so simple that we could understand it, we would be so simple that we couldn’t”-Emerson Pugh, The BiologicalOrigin of Human Values (1977)