Transcript Nervous System

Control Systems
(PB Lecture 17 – Spring 2008
Althoff Ch. 34)
• Nervous system
Systems of Control:
ENDOCRINE & NERVOUS
• BOTH “SYNTHESIZE” MESSENGER CHEMICALS
THAT ARE RELEASED INTO EXTRACELLULAR
SPACES
Hormones
Distance to impact
Approach Target
Duration of impact
Nerve cells
Functions
• Messenger (receive stimuli)
• Communicator (process stimuli)
• The critical “network” for maintaining
homeostasis…for advanced animals, this
means they are “wired” for quick response
Nervous System:
CNS = _____________________
(central nervous system)
vs.
PNS = all nerves & ganglia ________ the CNS
(peripheral nervous system)
______
______
CNS
• Brain & spinal
cord
• __________
sensory input,
__________
response
PNS
• Nerves: carries
sensory info to
CNS and motor
commands from
CNS
• ______ to
muscles & glands
Nerves
Bundles of nerve fibers outside the
CNS, most notably the axon and
dendrite(s) portion of neurons.
Cell Types
• ___________--conducts nerve impulses
• ___________--supports and services
neurons. Supplies nutrients, provides
protection, and gets rid of waste
Neuron Structure
CELL BODY
DENDRITE
AXON
AXON ENDINGS (= axon terminals)
MYELIN
Neuron Structure
• CELL BODY --nucleus & most organelles
• DENDRITE--receive incoming information
(i.e., stimulus)
• AXON--carry information away from cell
body
• AXON ENDING --makes contact with other
neurons, muscles, glands
• MYELIN--covering on some neurons
3 Types of Neurons
 __________ NEURON
 __________ NEURON
 _________________
(association neurons)
•Not all neurons look alike
•Not all neurons carry the same
type of information
Types of Neurons…con’t
• Consider types relative to CNS
• Collectively, they are the electronic
communications network of the body….
…know these types as well as their
relationship to one another!
 SENSORY NEURON
• Carry ________ info from periphery to CNS
(i.e., PNS  CNS)
• Both dendrite and axon are myelinated
• ____________ is in the PNS
• Examples: pain, pressure, touch, hot, cold,
light, sound, blood pressure, blood CO2,
bladder stretch, etc.
 MOTOR NEURON
• Carry ___________________ from CNS to
muscles or glands (i.e., CNS  PNS)
• Skeletal muscles - causes contraction
Smooth muscles - “
“
Adrenal gland - secrete hormone
• Cell body is in the CNS, therefore, axon is
usually ______
 INTERNEURONS
(association neurons)
• Found _____ inside the CNS
• Connects ___________ (sensory to motor
and vise versa)
• Typically short dendrites and either long or
short axons
Hand
moves
PNS
CNS
PNS
Nerve Impulse
A small ___________________ that
occurs across the plasma membrane of
neurons and then conducted along the
axon/dendrite of the neuron
RESTING POTENTIAL
NEURON AT REST
RESTING POTENTIAL
OUTSIDE
+40mV
-65mV
INSIDE
_________________
NEURON AT REST
__________
__________
RESTING to __________________
Na+
in
K+
out
During ACTION POTENTIAL, _____ channels open first,
Na+ rushes in resulting in depolarization…then _____
channels open, K+ rushes out.
Summary
RESTING POTENTAIL
• Maintained at about -65mV by sodiumpotassium pump (i.e., Na-K pump)
• _____ always diffusing back and forth
because of ___________________
• Na+ higher outside an axon, K + higher
inside the axon resulting in the axon
having a negative charge
ACTION POTENTIAL
• A rapid change in polarity across the
plasma membrane as the nerve impulse
occurs
• It is an “____________” phenomenon
• If it causes depolarization to a certain
level, it is called a ____________ and
an “action potential” occurs
ACTION POTENTIAL…con’t
• Strength of an action potential does ____
change…
• …but an intense stimulus can cause the
axon to fire at a ______________
• Requires two types of GATED CHANNELS:
one for ____ and one for _____ . The Na+
channel opens first
ACTION POTENTIAL…con’t
• During this process, Na+ moves to the inside
of the axon during the depolarization phase
(-65mV  +40mV)
• K + moves to the outside of the axon during
the repolarization phase.
(+40mV  -65mV)
• Review Fig. 34.5, pages 651 in Johnson and Losos
Propagation of an
Action Potential
• As action potential travels down the axon,
each successive portion of the axon
undergoes depolarization, followed by
repolarization
• Like a _________________
• As the action potential moves on, previous
portion goes through refractory period--Na+
channels are shut, then K + channels are shut
Propagation of an
Action Potential…con’t
• With refractory period (i.e., Na+ gate closed),
the action potential _________________
______________….just forwards
• At “nodes”, the action potentials jump from
node-to-node. At nodes, voltage-sensitive
Na+ channel gates are numerous. Speeds
of _____ meters/second (_____ miles/hour)
have been recorded along a motor neuron
Synapse Structure & Function
• Where “signal” is transmitted from ____
_____________________
• Axon bulb  synaptic cleft 
postsynaptic neuron
• ___________________--molecules that
transmit the signal across the synaptic
cleft
Synapse
(synaptic cleft)
Presynaptic
neuron
Postsynaptic
neuron
Put graphic from text
here
Neurotransmitters
• ____+ known substances or suspected to
be neurotransmitters
• Acetylcholine (ACh) and Norephinephrine
(NE) best known
• Acetylcholinestrease (AChE) is an
enzyme that breaks down ACh
Neurotransmitters
• Others include:
dopamine
serotonin
opioids (endorphin)
• Many drugs either _________________
________________________________
Integration
• Neurons handle “excitatory” and
“inhibitory” signals
• Each neuron sums up the two signal
types in a process known as
INTERGRATION
• Result: neuron either “fire” signal down
axon…or not “fire signal