Transcript The Nervous System

The Nervous System
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Do Now:
 Contract a K-W-L chart on loose-leaf
 List everything you already Know about the
Nervous System in the K-column
 List everything you Want to know in Wcolumn
Functions
 Monitors internal and external environments
 Integrates sensory information
 Coordinates voluntary and involuntary
responses of other organ systems
 2 subdivisions:
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CNS – brain and spinal cord
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Intelligence, memory, emotion
PNS – all other neural tissue
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sensory, motor
Receptors and Effectors
 Receptors – receive sensory info
 Afferent division – carries info from sensory
receptors to the CNS
 Efferent division – carries info from CNS to PNS
effectors (muscles, glands, adipose)
 Somatic Nervous System (SNS)
 Controls skeletal muscles (voluntary)
 Autonomic Nervous System (ANS)
 Controls involuntary actions
 Sympathetic Division (increase heart rate)
 Parasympathetic Division (decreases heart rate)
Neurons
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Communicate w/other neurons
Soma-Cell body
Dendrites - receive info
Axon- sends signal to synaptic
terminals (terminal buds)
 Synapse – site of neural
communication (gap)
 Myelin – fatty insulation of
axon(Schwann cells produce in PNS)
 Node of Ranvier – exposed axon
between myelin
 3 structural types:
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Multipolar – multiple dendrites &
single axon (motor neurons)
Unipolar – continues dendrites &
axon, cell body lies to side
(sensory neurons)
Bipolar – one dendrite and one
axon w/cell body between them
(special senses)
Types of Neurons
 3 functional types
 Sensory – afferent division
 info about surrounding environment
 position/movement skeletal muscles
 digestive, resp, cardiovasc, urinary, reprod, taste, and
pain
 Motor – efferent division (response)
 skeletal muscles
 cardiac and smooth muscle, glands, adipose tissue
 Interneurons
 Brain and spinal cord - memory, planning, and
learning
Neuroglia
 Regulate environment around
neurons; actively divide
 Functions in CNS:
 maintains the blood-brain
barrier(Astrocytes)
 create myelin (lipid) to coat
axon(Oligodendrocytes)
 Nodes of Ranvier – gaps
between myelinated
sections
 Internodes – areas
covered in myelin
 Phagocytic cells(Microglia)
View Action Potential
Remember:
•Discuss each question and answer
with your group
•Use the information from the models
to support your responses
Membrane Potential
 Cells are polarized (measured in volts)
 Resting potential of neuron -70mV
 Remains stable due to Na+/K+ Pumps
Leak channels – always open (K+ diffuses out)
Na+
Cl-
K+
Proteins-
Net - charge
Gated channels – open/closed under specific
circumstance
Changes in Membrane Potential
 Depolarization
Stimulus opens Na+ gated
channels
 increase +charge of cell towards
0mV
 Action Potentials
 Affects entire surface of cell
membrane
 (+) feedback as nerve impulse
continues
 Hyperpolarization
 Stimulus opens K+ gated
channels
 Increases –charge (from -70mV
to -80mV)
 Restores resting potential
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Action Potential:
All or Nothing Principal
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Only skeletal muscle fibers and neuron
axons have excitable membranes
Graded potential increases pressure
until sufficient enough to reach action
potential
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Continuous Propagation
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Resting potential (-70mV)
Reaches Threshold (-60mV)
Refractory Period – cell cannot
respond to stimulation
 Depolarization
 Repolarization
chain rxn until reaches cell memb
Unmyleinated – 1m/s (2mph)
Salatory Propagation
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Myelinated (blocks flow of ions
except at nodes)
Action potential jumps from node to
node
18-40m/s (30-300mph)
Neural Communication
 Nerve impulse – info moving
in the form of action potentials
along axons
 At end of axon the action
potential transfers to another
neuron or effector cell by
release of neurotransmitters
from synaptic terminal (only
occur in 1 direction)
 Activity of neuron depends on
balance between:
 Excitatory
neurotransmitters depolorization
 ACh & Norepinephrine
 Inhibitory
neurotransmitters hyperpolarization
 Dopamine, Seratonin,
GABA
Reflexes
 Reflex – involuntary response to
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stimulus w/o requiring the brain
Reflex arc- sensory neuron
Interneuron motor neuron
(opposes initial stimulus)
Ex. Knee jerk reflex
Babinski reflex (infants only)
 Stroke sole of foot  toes fan
out
Plantar reflex (adults only)
 Stroke sole of foot toes curl
Signals sent to brain by
interneurons allow for control
 Ex. Toilet training, gag, blink