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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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
fluid.
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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!
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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 carries
the neural impulse toward the terminal
branches.
- the
“senders”. They contain chemicals that
neurons use to communicate with each
other.
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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.
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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!
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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. 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. 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
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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.
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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. 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.
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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.
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18. The Cerebral Cortex
 Occipital lobes:
 Contain the primary visual cortex, which is responsible
for vision.
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19. Basal Ganglia
 A set of structures buried deep inside the brain that
help to control movement.
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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. 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.
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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. 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.
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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.
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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
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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.
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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 Biological
Origin of Human Values (1977)
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