Download Exercise Science

Introduction to Kinesiology
The Nervous System and the Control of
Movement
An Introduction to Health and Physical Education
Ted Temertzoglou
Paul Challen
ISBN 1-55077-132-9
“An organ system of specialized cells (neurons) that coordinate
the actions of an animal by transmitting different signals between
parts of the body.”
It has 3 main roles:
• Assemble information about conditions external and
internal to the body
• Analyze information
• Initiate response that may be necessary to satisfy
certain needs of the body
The Nervous System and Control of Movement:
There are two major components to the human nervous system:
1.Central Nervous System (CNS)
1.Brain and spinal cord
2.Accepts and coordinates information from all parts of the body
3.Has nerves going to and from it, which comprise the second
major component of the human nervous system- PNS
2.Peripheral Nervous System (PNS)
1.Responsible for the beating of the heart and digestive system,
and all other voluntary and involuntary neuromuscular controls
2.Think of it as a massive road network carrying traffic
(information) in and out of the CNS
3.Contains the autonomic and somatic divisions
Even though there are 2 major components to this system, they are interconnected
Central Nervous
system
Brain
Spinal
Cord
Peripheral Nervous
System
Central Nervous System (CNS)
• Brain and spinal cord
Main control centre for almost all body’s activities
Receives and interprets signals  commands
-main information pathway
-spinal nerves branch off cord
reaching different organs and
tissues
-named after where exit
Even though there are 2 major components to this system, they are interconnected
Central Nervous
system
Brain
Spinal
Cord
Peripheral Nervous
System
Autonomic
Nervous System
Somatic
Nervous System
Peripheral Nervous System (PNS)
• “Roadway” carrying all information towards and away
from the CNS
• Contains 12 pairs of cranial and 31 pairs of spinal nerves
2 roots:
1)
Motor Pathway (efferent)
2)
Sensory Pathway (afferent)
Autonomic Nervous System
• “Automatic” –involuntary contraction of cardiac muscle and the smooth muscles of our
internal organs is regulated by the ANS
•This subsystem is comprised of two branches; sympathetic and parasympathetic systems,
which act as opposing systems.
Sympathetic
Parasympathetic
• Localized bodily adjustments- sweating
• Returns body to normal state
• Prepare for emergencies – this involves the release of
• Decrease HR, rest, digest…
adrenaline from the adrenal gland, an increased HR,
widening of BV’s, and similar “fight or flight” responses to
deal with immediate danger.
Somatic Nervous System
• Provides us with our awareness of the external
environment- and the corresponding motor activity allowing
us to cope with it
•Contains both afferent and efferent nerve fibres
1.
Afferent
2.
Efferent
Afferent nerves send information to the CNS ex. Touch,
pain, heat, cold, balance, body position
Efferent nerves carry/send information from the CNS to
muscles/organs (skeletal muscles)
Through this system, the PNS receives and processes information from
receptors in the skin, in voluntary muscles, tendons, and joints, and gives us
the sensations of touch, pain, heat, cold, balance, body position, and muscle
action.
Autonomic and Somatic Nervous Systems
Reflexes, Proprioception, and
Movement:
 Reflexes are an important part of all physical
movement
 They are automatic and rapid responses to a
particular stimulus. Ex. Pain or the threat of pain
 If the command centre for the reflex is located in the
brain= cerebral reflex
 If the control centre is located in the spinal cord=
spinal reflex
Cont… Two types of Reflexes
 Autonomic Reflexes mediated by the autonomic
division of the nervous system and usually involve the
activation of smooth muscle, cardiac muscle, and glands
 These reflexes regulate bodily functions such as; digestion,
elimination, sweating, salivation, blood pressure
 Somatic Reflexes involve stimulation of skeletal
muscles by the somatic division of the nervous system.
 Include such reflexes as the stretch and withdrawal
 Reflex contraction of skeletal muscle is not dependent on
conscious intervention by higher centres of the brain but
are a way in which our bodies respond to unexpected
stimulus.
The Reflex Arc?
There are 3 types of neurons(transmit information to each other through a
series of connections that form a circuit) in the human body;
1. Sensory neurons detect or sense information from the outside
world. i.e. light, sound, touch, and heat
2. Motor neurons send signals away from the CNS and elicit a
response i.e. movement of a leg or arm
3. Interneuron's form interconnections between other neurons in
the CNS
One example of this simple circuit is the REFLEX ARC:
• allows a pathway long which the stimulus and response messages
travel
• Basic arrangement of the reflex arc involves a;
•1. receptor
•2. adjustor
•3. effector
The Reflex Arc
 Five parts to a reflex arc:





Receptor
Sensory (or afferent) nerve
Intermediate nerve
fibre/adjustor
Motor (or efferent) nerve
Effector organ
5 Components of a Reflex Arc (Exercise Workbook 6.3)
Receptor
Sensory (afferent)
nerve
Area of body that receive initial stimulus (often
skin)
Carries sensory impulse to spinal column or
brain
Interneuron
Adjustor  interprets signal and issues
(intermediate nerve response
fibre)/adjustor
Motor (efferent)
nerve
Carries response impulse from spinal cord to
muscle or organ
Effector Organ
-Area of body that carries out response (often
muscle)
Key to a reflex  it is not the brain that sends the motor signal
to the effector.
We already discussed how a sensory impulse can cause a muscle to contract....
NOW consider; what determines the extent to which a muscle contracts? The
moment when a muscle relaxes? How muscles coordinate with other muscles and
with other muscle groups? Answer lies in specialized receptors located within
tendons, muscles, and joints.
Proprioceptors:
“Provide constant sensory information about the state of muscle contraction,
the position of body limbs, and body posture and balance”
•This all-important feedback, along with control over muscles, is provided
primarily by the afferent (sensory) input from TWO SENSORY RECEPTORS:
1. Tendon Organs
2. Muscle Spindles
Tendon organs and muscle spindles continuously monitor muscle actions and
are essential components of the neuromuscular system.
 They “TELL” the nervous system about the state of muscle contraction, act as
a kind of safely device, and allow the nervous system to respond accordingly
1. Muscle Spindles- sensory receptors- proprioceptors
• play an essential role in all physical movement, they are the means by which muscles
constantly and automatically adjust to the demands placed on them
•Lie parallel to the main muscle fibre and send constant signals to the SPINAL CORD
•Consists of specialized muscle fibres, intrafusal muscle fibres, that run the length of the
muscle
• Help maintain muscle tension and are sensitive to changes in muscle LENGTH
• Contains TWO AFFERENT and ONE EFFERENT nerve fibre
• Spindle detects changes in the muscle fibre length and responds to it by
sending a message to the spinal cord, leading to the appropriate motor
responses
•The resulting contraction allows the muscle to maintain proper muscle tension
or tone i.e. an erect posture.
-video
The Muscle Spindle
Sensory neuron
(two branches within)
Motor neuron
Muscle spindle
within muscle fibre
(magnified)
Muscle fibres
Muscle spindles are responsible for one of the most recognizable reflexes . . .
The Stretch Reflex (Knee –Jerk)
• Monosynaptic reflex  depends only on the single connection between sensory
and motor neurons of the same muscle- extremely quick and automatic
•Knee-Jerk is used to demonstrate this type of reflex and is the simplest spinal
reflex
•A tap below the kneecap stretches the patellar tendon and acts as a stimulus,
initiating a reflex arc that causes the exterior muscle on top of the thigh to
contract
•As the tendon and muscle fibre are stretched, information is sent to the spinal
cord
•These nerve signals act directly on motor neurons that then quickly proceed to
contract the quadriceps femoris, the extensor muscle that serves to extend the
lower leg.
Muscle Spindles at Work
1. The receptor muscle senses the action of the hammer against the patellar ligament through the
muscle spindle’s sensory neuron
2. The message is transmitted along the afferent (sensory) nerve axon to the spinal cord
3. The afferent neuron then synapses with the efferent pathway (motor neuron) of the same
muscle
4. An impulse is transmitted along the efferent pathway (motor neuron) to the muscle fibre
5. The motor unit contract simultaneously, which in turn brings about a knee-jerk action to
accommodate the additional stretch
Sensory neuron
(two branches within)
Motor neuron
Muscle
fibres
Polysynaptic Reflex
• A reflex with one or more interneurons between the primary sensory
fibres and motor neurons
More = more complex = slower
Withdrawal Reflex (Pain –sharp/hot)
1. Stimulus is detected by receptors i.e. skin
2. Receptors initiate nerve impulses in the sensory neurons leading
from the receptors
3. Impulses travel into the spinal cord where the
sensory nerve terminals synapse with
interneurons
4. Some of the interneuron's synapse with motor neurons that
travel out from the spinal cord to the effectors organ
5. The arm flexors withdrawal the arm/hand from the danger
zone;
6. Other sensory neurons synapse with interneurons that affect
motor neurons in the opposing arm/leg and cause these muscles
to come into action- see next example
Polysynaptic Reflexes – cont’d
 Crossed-Extensor Reflex:
 Observed when one leg or arm automatically compensates for a reflex
action in opposing leg or arm
 Involves multiple synapses and muscle groups
2. Golgi Tendon Organs (GTO)
•Are sensory receptors found at the end of muscle fibres that merge into
the tendon itself and that detect changes in muscle tension.
•Are aligned in series with the muscle, such that any muscle stretching
also stretches the GTO receptor
•Specifically positioned to detect increased tension exerted on the
tendon
•Serve as a tension detection device for the muscle system.
•Help protect the muscle from excessive tension that would otherwise
result in damage to the muscle or the joint or even BOTH.
•Provide feedback to the CNS regardless of magnitude of the tensionthus play an important role in strength and power, since in order to be
able to exert a greater force, you must overcome the obstacles
presented by the Golgi tendon organ itself.
Golgi Tendon Organs
Golgi Tendon Organs (GTO’s)
1)Change in tension 2)impulse sent along sensory (afferent) neuron to spinal cord 
3)synapse with interneuron 4)motor (efferent) neuron sends impulse 5)muscle
relaxes (preventing injury) (Fill in Workbook Exercise 6.4)
Golgi Tendon Organs & Muscle Spindles
Golgi Tendon Organs
Muscle Spindles
Location
Where tendon meets muscle
fibre
In belly of muscle fibre
Position
In series with muscle fibre
Parallel to muscle fibre
Respond to
Changes in muscle/tendon
tension
Changes in muscle length
Sensory
neurons
1
2
Workbook:
Pg. 118-119
Consider:
1.What is the role of sensory receptors found in muscles,
tendons, and joints in producing physical movement?
MAIN IDEAS:
1.Proprioception is a person’s ability to sense the position,
orientation, and movement of the body. This body system
plays an indispensable role in physical movement
2.Specialized sensory receptors, called proprioceptors , are
located within tendons, muscles, and joints
3.These receptors i.e. muscle spindles and golgi tendon
organs – provide sensory information about the state of
muscle contraction, the position of body limbs, and body
posture and balance.
Spinal Cord and Head Injuries
 Spinal cord injuries:
 Damage to the spine can result in
©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material.
This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook.
© iStockphoto.com/”caracterdesign”
an inability to send impulses to
body parts
 Nerves above injury keep working,
nerves below may not
 Paraplegia:
 Injury prevents use of legs but
not arms
 Quadriplegia:
 Injury prevents movement of
both arms and legs
Spinal Cord and Head Injuries

©Thompson Educational Publishing, Inc. 2003. All material is copyright protected. It is illegal to copy any of this material.
This material may be used only in a course of study in which Exercise Science: An Introduction to Health and Physical Education (Temertzoglou/Challen) is the required textbook.
© iStockphoto.com/”AlexKalina”
Head injuries:
 Most common head injury is a
concussion:
 Occurs when brain literally
hits the skull; often
involves injury to nerve
fibres
 Ranges from mild to
severe
 Symptoms can include:
headaches, fatigue,
memory problems, or
slurred speech