1. The Nervous System
-Reflexes

2. What is a reflex? What signals a reflex?
Automatic and rapid responses to particular stimulation
-pain or the threat of pain
2 types of reflexes:
1. Autonomic
2. Somatic
-stimulation of skeletal muscle
What signals a reflex?
Reflex arc: the pathway along which the stimulus and response messages travel
Composed of a(n): 1) receptor
2) adjustor
3) effector

3. Reflex Arc

4. -area of body that receive initial stimulus (often skin)
Receptor
-area of body that receive initial stimulus (often skin)
Sensory (afferent) nerve
-carries sensory impulse to spinal column
Interneuron (intermediate nerve fibre)
-adjustor  interprets signal and issues response
Motor (efferent) nerve
-carries response impulse from spinal cord to muscle
Effector
-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.

5. Reflex Arc
-video

6. Proprioceptors 1. Golgi Tendon Organs (GTO)
We already discussed how a sensory impulse can cause a muscle to contract
But how does that muscle fibre know when, how much and who to contract with?
Proprioceptors
“Provide constant sensory information about the state of muscle contraction”
-specialized sensory receptors found in tendons, muscles and joints
There are 2 we will be looking at:
1. Golgi Tendon Organs (GTO)
-in series where muscles and tendons meet
-when muscles stretch GTO’s stretch
-therefore detect TENSION changes
-protect muscle from excessive tension (damage)
-development of power and strength
-overcome GTO’s
( )

7. Golgi Tendon Organs (GTO’s)
Change in tension  impulse sent along sensory (afferent) neuron to spinal cord 
synapse with interneuron  motor (efferent) neuron sends impulse  muscle
relaxes (preventing injury)

8. 2. Muscle Spindles -video
-smaller more specialized muscles fibres (intrafusal) running parallel to the main muscle fibres
-help maintain muscle tension (eg. standing erect)
-detect changes in muscle LENGTH
Change in muscle length  sensory impulse to spinal cord (x2)  motor
response  muscle contracts (remains in proper tension)
-video

9. 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

10. The Stretch Reflex (Knee –Jerk)
Muscle spindles are responsible for one of the most recognizable reflexes . . .
The Stretch Reflex (Knee –Jerk)
Monosynaptic reflex  only one connection between sensory and motor neuron
Tapping petallar tendon
 Pulls on quad femoris  excites spindles (length change)  sensory to spinal cord  motor to contract quad femoris  knee-jerk
Sudden increase in carrying weight?
1. Stimulus
2. Receptor
Reciprocal Inhibition
3. Sensory impulse
4. Motor impulse
5. Muscle contracts

12. Polysynaptic Reflex Withdrawal Reflex (Pain –sharp/hot)
But we’re missing something. What did we say was the key to a reflex?
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)

13. 3. Interneuron synapse in spinal column
1. Stimulus from skin in form of heat (receptor)
2. Sensory impulse generated
3. Interneuron synapse in spinal column
4. Motor impulse generated by interneuron (others to brain = pain)
5. Impulse to proper muscle causing contraction
6. Removal of stimulated area

14. But why do we still feel pain when we place our hand over a flame?
There is still a sensory impulse sent to the brain, but it only reacts to make us feel pain.
Because it is further away and contains more interneurons it is a slower process

15. 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

16. The Nervous System
-Control of Movement
-video

17. The Nervous System It has 3 main roles:
“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

18. "Nervous Breakdown" Central Nervous system Peripheral Nervous System
Even though there are 2 major components to this system, they are interconnected
"Nervous Breakdown"
Central Nervous system
Peripheral Nervous System
Brain
Spinal Cord

19. Central Nervous System (CNS)
Brain and spinal cord
-main control centre for almost all body’s activities
-receives and interprets signals  commands
-the brain consists of 6 main parts (determine the function of each part –pg 95)
-main information pathway
-spinal nerves branch off cord reaching different organs and tissues
-named after where exit
Ex. L3  innervates the rectus femoris (extend knee)
Cerebrum
Cerebellum
Brain stem
Diencephalon
Limbic system
Reticular activating system

20. "Nervous Breakdown" Central Nervous system Peripheral Nervous System
Even though there are 2 major components to this system, they are interconnected
"Nervous Breakdown"
Central Nervous system
Peripheral Nervous System
Autonomic Nervous System
Somatic Nervous System
Brain
Spinal Cord
Sympathetic System
Parasympathetic System

21. Peripheral Nervous System (CNS)
“roadway” carrying all information towards and away from the CNS
Contains 12 pairs of cranial and 31 pairs of spinal nerves
2 roots:
Motor (efferent)
Sensory (afferent)
Autonomic Nervous System
“automatic” –involuntary contraction
-cardiac muscles, muscles organs
2 opposing branches
Sympathetic
localized bodily adjustments
prepare for emergencies (fight or flight)
adrenaline, increased HR
Parasympathetic
returns body to normal state
decrease HR, rest, digest, etc

22. "Nervous Breakdown" Central Nervous system Peripheral Nervous System
Even though there are 2 major components to this system, they are interconnected
"Nervous Breakdown"
Central Nervous system
Peripheral Nervous System
Autonomic Nervous System
Somatic Nervous System
Brain
Spinal Cord
Motor
Sympathetic System
Sensory
Parasympathetic System

23. Look at example on page 97 (fig. 6.2)
Somatic Nervous System
awareness to external environment
motor movements to cope
Afferent
2. Efferent
-info from skin, joints, muscles  touch, pain,
heat, cold, balance, body position
voluntary movements to respond to stimuli
Look at example on page 97 (fig. 6.2)