11.3, 11.4 The Central and
Peripheral Nervous System
Monday, 6 January, 14
December 19, 2013.
The Spinal Cord
carries sensory nerve messages from receptors to the brain
and relays motor nerve messages from the brain to the
muscles, organs and glands.
• CNS (central nervous system) is made of spinal cord and brain
• spinal cord is protected by vertebrae in backbone and
cerebrospinal fluid which acts as a shock absorber and
transports wastes/nutrients
• fluid can also be used to diagnose bacterial/viral infections
• made of grey matter (interneurons, unmyelinated) and white
matter (myelinated)
• dorsal nerves bring sensory info into spinal cord
• ventral nerve sends motor info to the muscles/organs
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The Spinal Cord
nucleus
nucleus
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The Brain
• in humans, the brain gives us higher/more complex functions like
intellect/reasoning
• composed of forebrain, midbrain, hindbrain
• FOREBRAIN: olfactory lobes (smell), cerebrum (coordinating
centre)
๏ the cerebral cortex is made of grey matter
๏ cerebrum is divided into left (verbal skills) and right (patterns,
spatial recognition) hemispheres
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The Brain
๏ each hemisphere is divided into 4 lobes: frontal (voluntary
muscles, memory, behaviour), temporal (vision, hearing
memory, speech, emotional response), occipital (touch,
temperature, emotions, colour), parietal (speech interpretation,
cognition, pain and touch sensation, spatial orientation)
• motor sections are larger for more complex/delicate movements
(mouth, tongue have largest brain area)
• MIDBRAIN: relay centre for eye/ear reflexes
• HINDBRAIN: cerebellum (limb movement, balance, muscle tone),
pons (relay system between cerebrum, cerebellum, medulla),
medulla oblongata (involuntary muscle control)
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The Brain: Forebrain, Midbrain, Hindbrain
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The Brain: Lobes (in right and left hemispheres)
http://www.youtube.com/watch?v=HVGlfcP3ATI&feature=related
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Left Brain-Right Brain
• functions that are equally distributed: recognition of faces,
consciousness, sense of time, recognizing emotions
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The Blood-Brain Barrier
• the cells that form the capillaries do not let as many molecules
through as capillaries in other parts of the body do
• levels of various types of substances in the blood (sugar, H+,
etc) vary and the barrier allows a more stable composition of
the cerebrospinal fluid
• this barrier also provides protection from viruses, bacteria, and
other toxic substances that could be found in the blood
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Brain Mapping
• much of what we know about which regions of the brain
control what was learned from stroke patients (restricted
blood flow to area of brain)
• Wilder Penfield (40’s/50’s) discovered the two brain
hemispheres had different roles, different processes in
different areas
http://www.youtube.com/watch?v=kNdM9JhTPJw
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The Peripheral Nervous System
• Somatic: conscious, voluntary, carries signals from the CNS
to the skeletal system
• Autonomic: regulate the organs of the body without
conscious control
•autonomic nerves act to restore homeostasis - maintains
the internal environment of the body by adapting to the
external environment
•made up of the sympathetic (prepares the body for
stress) and parasympathetic nervous system (restores
normal balance)
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Some Effects of the Autonomic Nervous System
Organ
Sympathetic
Parasympathetic
heart
increases heart rate
decreases heart rate
digestive
decreases peristalsis
increases peristalsis
liver
increases the release of
glucose
stores glucose
eyes
dilates pupils
constricts pupils
bladder
relaxes sphincter
contracts sphincter
skin
increases blood flow
decreases blood flow
adrenal gland
causes release of
epinephrine
no effect
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Some Effects of the Autonomic Nervous System
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Neurotransmitters as Natural Painkillers
•examples: endorphins and enkephalins
•pain is interpreted by specialized cells (SG) in the spinal cord
•when stimulated, these cells produce a neurotransmitter that
“informs” the injured organ or tissue of the damage
•when endorphins or enkephalins attach to the receptor sites on
the SG cells instead, the pain signal is blocked
•opiates such as heroine, codeine, and morphine work like
endorphins
• drugs that are depressants (valium, librium) enhance the action of
inhibitory synapses
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Lie Detectors and the Autonomic Nervous System
• http://videos.howstuffworks.com/discovery/6833-human-body-howpolygraph-tests-work-video.htm
•http://videos.howstuffworks.com/discovery/6527-mythbusters-liedetector-test-video.htm
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