6. Spinal Reflexes Flashcards
What is a reflex?
Response that occurs automatically without conscious effort
What are the functions of reflexes?
Rapid withdrawal from painful stimuli Protection against over-stretching Empty pelvic organs Balance and movement Learned
What are the 3 types of sensory receptors?
Interoceptors
Proprioceptors
Exteroceptors
What stimuli are detected by interoceptors?
Pain
Stretching
What stimulus is detected by proprioceptors?
Position in space
What stimuli are detected by exteroceptors?
Temperature
Pressure
What do somatic reflexes act on?
Skeletal muscle
What are the two types of somatic reflexes?
Monosynaptic
Polysynaptic
Which reflex is monosynaptic?
Myotactic reflex
What two types of receptors are used in the myotactic reflex?
Muscle spindles
Golgi tendon organs
What do muscle spindles detect?
Rate of change in length of muscle
What do golgi tendon organs detect?
Rate of change of tension in muscle
What are the primary regulators of muscle tone?
Muscle spindles
y-neurons continuously send info to brain and cerebellum
What neurons are efferent from golgi tendon organs?
1b
What effect does an increase in tension have?
Reflex inhibition of motor neuron
What are the steps in the knee jerk reflex?
- Tapping on the patellar ligament stretches the quads
- Stretch of muscle spindles
- Increased firing 1A sensory nerves
- Increased activity of motor neuron to quads
- Quads contract
What conditions can cause hyporeflexia?
Polio
Muscular dystrophy
Lower motor neuron lesions
What conditions can cause hyperreflexia?
Stroke
Brain tumour
Damage to motor area of cerebral cortex
Upper motor neuron lesion
What is reciprocal innervation?
In stretch reflexes, the antagonist muscle must relax to allow the protagonist to contract
Stretch reflex in the antagonist is inhibited by an interneuron
What kind of reflexes are polysynaptic?
Withdrawal reflexes
Which sensory fibres cause a withdrawal reflex?
A-delta
How are spinal reflexes controlled?
Can be overrided by higher brain centres
IPSPs to flexor and EPSPs to extensor
What is the crossed extensor reflex?
Eg. Stepping on a sharp object
Simple reflex arc in leg that was hurt
Interneuron from hurt leg crosses into opposite
Activates motorneuron on opposing side to allow planting of foot
