Transcript Nervous System

Nervous System
Roles
• Monitors changes
– What are the changes?
• Processes and interprets sensory input
• Effects a response
Organization
• CNS
– Organs?
• PNS
– Organs?
PNS
• Sensory (afferent) - delivers messages from
the sensory receptors toward the CNS
• Motor (efferent) - delivers messages from the
CNS to organs
– Somatic nervous system - messages sent to
muscles
– Autonomic nervous system - messages sent to
smooth muscle, cardiac muscles, and glands.
– Which would be considered the involuntary
nervous system? Why?
Nervous Tissue
• Neuroglial cells of CNS
– Astrocytes - form a barrier between capillaries and
neurons
– Microglia - phagocytes
– Ependymal - use cillia to circulate cerebrospinal
fluid
– Oligodendrocytes - form myelin sheath
• Neuroglial cells of PNS
– Schwann cells - form myelin sheath
– Satellite cells
• Neurons
Neurons
• Cell body
– What is all here?
• Dendrites - receive incoming electrical
stimulus
– Neurons have hundreds of dendrites
• Axons - send out electrical stimulus
– Neurons only possess one
– mm to m in length. Where could an axon a meter
in length be found?
Axons
• Possess hundreds or thousands of axon
terminals
• Terminals contain hundreds of vesicles
– What are found in the vesicles (think about
the axon innervating the muscle)?
– Why are these chemical messengers
needed?
Axons
• Most nerve fibers are covered with
myelin
– It is a fatty material. Function?
• What cells make up the myelin sheath?
• Gaps between cells are called nodes of
Ranvier
Neuron classification
• Afferent (sensory neuron)
– Examples?
• Efferent (motor neuron)
• Interneurons
– What do you think these do?
Neuron Physiology
• Based on balance of what ions?
• Threshold stimulus
• All-or-none response
Neuron Physiology
• Resting membrane potenial (polarized)
• Na+ is highly concentrated outside the
cell
• K+ is highly concentrated inside the cell
Neuron Physiology
• Stimulus initiates an action potential
• Causes Na+ channels to open
– What will this cause?
– Depolarization
• Once a small area is depolarized it
stimulates adjacent areas
– Creates an action potential
Neuron Physiology
• After depolarization, K+ channels open
– What will this cause?
– Repolarization
• What has to happen in order to get back
to resting potential?
Neuron Physiology
• Myelin sheath speeds up the
propagation of the action potential
• The impulse can travel at speeds up to
120 m/sec
• How does the nerve impulse get from
one neuron to the next?
Reflex
• Rapid, predictable, involuntary motions
• What would a reflex be called that stimulates
a skeletal muscle? Smooth muscles, heart,
glands?
• Reflex arcs
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Sensory receptor
Effector organ
Sensory neurons
Motor neurons
Integration center (CNS)
Central Nervous System
Protection
• Meninges - connective tissue
membranes
– Dura mater
– Arachnoid mater
– Pia mater
• What do you think meningitis is?
Central Nervous System
Protection
• Blood Brain Barrier
– There are not spaces between cells in the
brain capillaries
– Significance?
– What glial cells help form tight junctions
between epithelial cells?
– Lipid soluble molecules can easily pass.
What types of molecules would not pass?
Central Nervous System
Protection
• Blood Brain Barrier
– Glucose is water soluble. How does it
cross the BBB
– The BBB is weaker in the emetic center of
the brain. Why?
Central Nervous System
Cerebrospinal Fluid
• Colorless liquid similar to blood plasma
• Surrounds the brain and spinal cord
• Role?
Central Nervous System
Brain
• Cerebrum - most superior portion of the
brain
– Gyri - ridges
– Sulci - grooves
– Fissures - deeper grooves
– These separate the lobes of the cerebrum
Cerebrum
• Motor areas, sensory areas, association
areas
• Each hemisphere is concerned with the
functions of the opposite side of the
body.
• Hemispheres are not equal in function
• No functional area works alone
Cerebral lobes
• Parietal - somatic sensory (primary and
association) area
– Impulses travel to and from sensory receptors
(pain, cold, touch)
– Sensory pathways are crossed
• Occipital - visual (primary and association)
area
• Temporal - auditory association area
– olfactory
Cerebral Lobes
• Frontal - primary motor area (patways
are crossed)
– Intellectual reasoning
– Social acceptability
– Complex memories (shared with temporal)
– Language comprehension
Cerebral Hemispheres
• Gray matter - outermost (cerebral
cortex)
• White matter - inner
– Consists of fiber tracts - bundles of nerve
fibers that carry impulses to and from the
cortex
– Corpus callosum - connects the two
hemispheres and allows for communication
Central Nervous System
Diencephalon
• Thalamus - sensation is determined pleasant
or unpleasant
• Hypothalamus - regulation of body
temperature, water balance, metabolism
– Thirst, appetite, pain, pleasure, and sex centers
– Regulates pituitary
• Pituitary Gland - major hormone producer
Central Nervous System
Brain Stem
• About the size of a large thumb
• Midbrain - involved with vision and
hearing
• Pons - breathing center
• Medulla Oblongata - controls vital
visceral activities
– Like what?
Central Nervous System
Cerebellum
• Coordinates muscle movement
• Monitors cerebrums intentions with
actual performance
• Contains the arbor vitae
Spinal Cord
• Extends from _________ to _________
• What are the layers of protection?
Fluid?
• Two way conduction
• Major reflex center
• Where would be a good location for
CSF testing?
• Cauda equina
Peripheral Nervous System
Nerves
• Axon, fascicle, and nerve
• endoneurium, perineurium, and
epineurium
• How would you describe the structure of
a nerve?