1. What is the difference
between a neuron and other
cells? Where does it start
and end?
2. What is the interaction that
neurons have with muscles?
1. Draw a neuron and label
it. Try not to look back
and cheat.
2. What is an action
potential?
Explain this graph. What are the
three most important numbers?
Draw the axon of neuron so that
you can see the inside and the
outside. Now label which side
starts out positive and negative.
Also, label the placement of the
sodium and potassium ions at
resting potential.
1. How do you think your body
registers different amounts of
pain or pressure? How does it
separate out the difference.
Explain your answer.
Neural Control
of Exercising Muscle
Neuron has three major regions:
• Cell body
– Contains nucleus
• Dendrites
– Receiver cell processes
• Axon
– Sender cell process, starts at axon hillock
– End branches, axon terminals store
neurotransmitters in vesicles.
Nervous System Structure
and Function: Nerve Impulse
• Electrical signal for
communication between
periphery and brain
• Must be generated by a stimulus
• Must be propagated down an axon
• Must be transmitted to next cell in
line
Resting Membrane Potential
• Difference in electrical charges
between outside and inside of cell
• −70 mV
• Caused by uneven separation of
charged ions
• Polarized
1. What is depolarizing mean?
What causes it?
2. Why does hyperpolarization
happen? What does it mean?
Resting Membrane Potential
• Why −70 mV?
– High [Na+] outside cell, medium [K+] inside cell
– Inside more negative relative to outside
• Na+ channels closed
– Na+ wants to enter cell but can’t
• K+ channels open
– K+ leaves cell (concentration gradient)
– Offset by Na+−K+ pumps
Depolarization and Hyperpolarization
• Depolarization
– Occurs when inside of cell becomes less
negative,
-70 mV  0 mV
– More Na+ channels open, Na+ enters cell
• Hyperpolarization
– Occurs when inside of cell becomes more
negative, -70 mV  −90 mV
– More K+ channels open, K+ leaves cell
Graded and Action Potentials
• Depolarization and hyperpolarization
contribute to nervous system function
via
– Graded potentials (GPs)
• Help cell body decide whether to pass signal
to axon
• Can excite or inhibit a neuron
– Action potentials (APs)
• Pass signal down axon
• Only excitatory
Graded Potentials
• Localized changes in membrane potential
– Generated by incoming signals from dendrites
– Inhibitory signal = K+ efflux = hyperpolarization
– Excitatory signal = Na+ influx = depolarization
• Strong GP  AP
– How strong? Must depolarize to threshold mV
– AP will be propagated down axon
– AP will be transmitted to next cell
Action Potentials:
Generating an AP
• If GP reaches threshold mV, AP will
occur
– ~−55 mV
– Threshold mV not reached = no action potential
– All-or-none principle
• − 70 mV  +30 mV  − 70 mV again
– − 70 to −55 mV: depolarizing GP, Na+ influx
– − 55 to +30 mV: depolarizing AP, Na+ influx
– +30 to −70 mV: repolarizing AP, K+ efflux
Figure 3.3
Action Potentials:
Refractory Periods
• Absolute refractory period
– During depolarization
– Neuron unable to respond to another stimulus
– Na+ channels already open, can’t open more
• Relative refractory period
– During repolarization
– Neuron responds only to very strong stimulus
– K+ channels open (Na+ closed, could open again)
Action Potentials:
Propagation Down Axon
• Myelin: speeds up signal
– Not continuous (nodes of Ranvier)
– Multiple sclerosis: degeneration of myelin
• Axon diameter: larger = faster
Synapse:
Transmitting APs
• Junction or gap between neurons
– Site of neuron-to-neuron communication
– AP must jump across synapse
• Axon  synapse  dendrites
– Presynaptic cell  synaptic cleft  postsynaptic
cell
– Signal changes form across synapse
– Electrical  chemical  electrical
Figure 3.4
Synapse:
Transmitting APs
• AP can only move in one direction
• Axon terminals contain neurotransmitters
–
–
–
–
Chemical messengers
Carry electrical AP signal across synaptic cleft
Bind to receptor on postsynaptic surface
Stimulate GPs in postsynaptic neuron
Neuromuscular Junction:
A Specialized Synapse
• Site of neuron-to-muscle
communication
– Uses acetylcholine (ACh) as its
neurotransmitter
– Excitatory: passes AP along to muscle
• Postsynaptic cell = muscle fiber
– ACh binds to receptor at motor end plate
– Causes depolarization
Figure 3.5
Neurotransmitters
• 50+ known or suspected
• Two major categories
– Small molecule, rapid acting
– Large molecule neuropeptides, slow
acting
1. Draw the graph in you
notebook and explain the
major steps.
2. How many neurotransmitters
do we know of? Which is
used for muscle contraction?
1. What is the difference between
gray and white matter in the
brain? What do you think
causes the different coloration?
2. Why do you think our brain is
the part of our body we know
least about?
1. What is your opinion of Logan’s
Drake impression?
I am going to show you a
clip and then give you
the warm-up questions.
Get your notebook ready.
1. What causes a concussion?
What are the symptoms?
2. What sports do you think have
the highest concussion rate?
Trailer
1.
2.
What did you think of the results we
saw yesterday with the distractions?
Did you think it would make that big of
a difference? Why or why not?
This is a homunculus, what do you
think it is representing?
1.
This is different a homunculus, what do
you think it is representing?
1. What did you think was the
cause of you being able to feel
the two points closer together?
2. What was your most sensitive
area and what was your least?
Figure 3.1
Brain: Cerebrum
• Left and right hemispheres
– Connected by corpus callosum, which
allows interhemisphere communication
• Cerebral cortex
– Outermost layer of cerebrum
– Gray matter (nonmyelinated)
– Conscious brain (mind, intellect,
awareness)
Cerebrum: Five Lobes
• Four superficial (outer) lobes
– Frontal: general intellect, motor control
– Temporal: auditory input, interpretation
– Parietal: general sensory input,
interpretation
– Occipital: visual input, interpretation
Cerebrum: Regions of Interest for
Exercise Physiology
• Primary motor cortex (frontal lobe)
– Conscious control of skeletal muscle movement
• Basal ganglia (cerebral white matter)
– Help initiate sustained or repetitive movements
– Walking, running, posture, muscle tone
• Primary sensory cortex (parietal lobe)
Brain: Cerebellum
• Coordinates timing, sequence of
movements
• Compares actual to intended movements
and initiates correction
• Accounts for body position, muscle
status
• Receives input from primary motor cortex
Figure 3.6
Spinal Cord
• Tracts of nerve fibers permit
two-way conduction of nerve
impulses
–Ascending afferent (sensory) fibers
–Descending efferent (motor) fibers
Peripheral Nervous System
• Connects to brain and spinal cord
– Both types directly supply skeletal
muscles
• Two major divisions
– Sensory (afferent) division
– Motor (efferent) division
Sensory Division
• Transmits information from periphery to
brain
• Major families of sensory receptors
– Mechanoreceptors: physical forces
– Thermoreceptors: temperature
– Nociceptors: pain
– Photoreceptors: light
– Chemoreceptors: chemical stimuli
Motor Division
• Transmits information from brain to
periphery
• Two divisions
– Autonomic: regulates visceral activity
– Somatic: stimulates skeletal muscle
activity
Motor Division:
Autonomic Nervous System
• Controls involuntary internal functions
• Exercise-related autonomic regulation
– Heart rate, blood pressure
– Lung function
• Two complementary divisions
– Sympathetic nervous system
– Parasympathetic nervous system
Autonomic Nervous System:
Sympathetic
• Fight or flight: Prepares body for
exercise
• Sympathetic stimulation
–  Heart rate, blood pressure
–  Blood flow to muscles
–  Airway diameter
–  Metabolic rate, glucose levels, FFA levels
–  Mental activity
Autonomic Nervous System:
Parasympathetic
• Rest and digest
– Active at rest
– Opposes sympathetic effects
• Parasympathetic stimulation includes
–  Digestion, urination
– Conservation of energy
–  Heart rate
–  Diameter of vessels and airways
1. What is the difference between
gray and white matter in the
brain? What do you think
causes the different coloration?
2. Why do you think our brain is
the part of our body we know
least about?
Sensory-Motor Integration
• Process of communication and interaction
• Five sequential steps
1. Stimulus sensed by sensory receptor
2. Sensory AP sent on sensory neurons to CNS
3. CNS interprets sensory information, sends out
response
4. Motor AP sent out on a-motor neurons
5. Motor AP arrives at skeletal muscle, response
occurs
Figure 3.7
Sensory-Motor Integration:
Sensory Input
• Can be integrated at many points in CNS
• Complexity of integration increases with
ascent through CNS
– Spinal cord
– Lower brain stem
– Cerebellum
– Thalamus
– Cerebral cortex (primary sensory cortex)
Figure 3.8
Sensory-Motor Integration:
Motor Control
• Sensory input can evoke motor response
regardless of point of integration
– Spinal cord
– Lower region of brain
– Motor area of cerebral cortex
• As level of control moves from spinal
cord to cerebral cortex, movement
complexity 
Sensory-Motor Integration:
Reflex Activity
• Motor reflex
– Instant, preprogrammed response to a
given stimulus
– Response to stimulus identical each time
– Occurs before conscious awareness
• Impulse integrated at lower, simple
levels
Sensory-Motor Integration:
Muscle Spindles
• When stretched, muscle spindle sensory
neuron
–
–
–
–
Synapses in spinal cord with an a-motor neuron
Triggers reflex muscle contraction
Prevents further (damaging) stretch
Stretch reflex
Sensory-Motor Integration:
Golgi Tendon Organs
• Sensory receptor embedded in tendon
– Associated with 5 to 25 muscle fibers
– Sensitive to tension in tendon (strain gauge)
• When stimulated by excessive tension,
Golgi tendon organs
– Prevent excessive tension in muscle/tendon
– Reduce potential for injury
Figure 3.9
Motor Response
• a-Motor neuron carries AP to muscle
• AP spreads to muscle fibers of motor unit
– Fine motor control: fewer fibers per motor unit
– Gross motor control: more fibers per motor unit
• Homogeneity of motor units
– Fiber types not mixed within a given motor unit
– Either type I fibers or type II fibers
– Motor neuron may actually determine fiber type