1. The Reflex Arc
Reflexes are an automatic and rapid response to a particular stimulation
If the command centre for the reflex is located in the brain – cerebral reflex
If the command centre for the reflex is located in the spinal cord – spinal reflex

2. Autonomic and Somatic Reflexes
Autonomic reflexes are mediated by the autonomic division of the nervous system
Involve activation of smooth and cardiac muscles as well as glands
Regulate bodily functions such as digestion, elimination, blood pressure, salivation, and sweating
Somatic Reflexes involve stimulation of skeletal muscles

3. The Reflex Arc
The name given to the pathway along which the initial stimulus and the corresponding response message travel

4. There are 5 parts to a reflex arc:
1. Receptor: receives the initial stimulus i.e. A loud noise, pinprick to the skin)‏
2. Sensory nerve: carries the impulse to the spinal column or brain (aka afferent nerve)‏
3. Intermediate nerve fibre: interprets the signal and issues and appropriate response

5. Cont...
4. Motor nerve: carries the response message from the spinal cord to the muscle or organ (aka efferent nerve)‏
5. Effector organ: carries out the response (i.e. Skeletal muscle – moving your hand away from danger)‏

7. Proprioceptors and the Control of Movement
Proprioceptors – specialized receptors found in tendons, muscles, and joints
Provide sensory information about the state of muscle contraction, the position of limbs, and body posture and balance
This feedback is provided primarily by afferent (sensory) input from two sensory receptors: tendon organs and muscle spindles

8. Golgi Tendon Organs (Tension Reflex)‏
Sensory receptors that terminate where tendons joint to muscle fibres
Since they are aligned with muscle, any stretching of the muscle also stretches the GTO
The job of GTO is to detect increased tension exerted on the tendon

9. GTO cont...
When a change in tension is detected an impulse is sent along afferent (sensory) neurons to the CNS
The efferent (motor) neurons transmit an impulse causing the muscle to relax
This prevents injury

10. Muscle Spindles Lie parallel to the muscle fibre
Send constant signals to the spinal cord
Help maintain muscle tension
Unlike GTO, they are sensitive to changes in muscle length rather than tension

11. Muscle Spindles cont...
Contains two afferent and one efferent nerve fibres
Two sensory nerves explains high level of sensitivity as well as the critical role they play in regulating muscle contraction
Responds to changes in length by sending a message to the spinal cord
Resulting contraction allows the muscle to maintain proper muscle tension or tone (i.e. Erect posture)‏

12. The Stretch Reflex Simplest spinal reflex
Depends only on the single connection between primary afferent fibres and motor neurons of the same muscle
i.e. Knee-jerk test

13. 1. The receptor muscle senses the action of the hammer against the patella 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 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
5. The motor units contract (knee-jerk to accomodate additional stretch)‏

14. Reciprocal Inhibition
During a reflex, the opposing muscle group is simultaneously stimulated
In a knee-jerk reflex the quadriceps contract to extend the knee while the hamstrings are inhibited in a slightly delayed response (they do not flex)‏

15. Polysynaptic Reflexes
With other spinal reflexes, one or more interneurons lie between the primary sensory fibres and the motor neurons
The more interactions involved, the more complex and slow the reflex

16. The Withdrawal Reflex
The withdrawal of a body part from a painful stimulus
Reflex action involves transferring the impulse from a sensory neuron to a motor neuron through a connecting interneuron in the spinal cord
Extremely rapid, brain doesn't have time to interpret information