Reflex Jeopardy

Muscle Spindle

100

Muscle spindles are surrounded by:

Extrafusal muscle fibers

200

Muscle spindles are made up of:

Bundles of small specialized intrafusal muscle fibers

300

The function of extrafusal muscle fibers is to:

Maintain tone and contract muscle

400

• Describe the sensory region

• Central region of intrafusal fibers
• Wound with dendrites of sensory neurons
• Synapses onto gamma motor neurons

500

What are gamma efferents and what are their functions?

• Axons of the motor neurons
• Complete reflex arc that synapses back onto intrafusal fibers
• They are important in voluntary muscle contractions
• Allow CNS to adjust sensitivity of muscle spindles

Reflex Classifications

100

• Reflexes can be classified by:

• Development (innate vs acquired)
• Response (somatic vs visceral (autonomic))
• Complexity of circuit (monosynaptic vs polysynaptic)
• Processing site (spinal vs cranial)

200

What is the difference between a monosynaptic reflex and a polysynaptic reflex?

• Monosynaptic: Sensory neuron synapses directly onto motor neuron
• There is at least one interneuron between sensory neuron and motor neuron

300

What are the two kinds of inborn reflexes and what do they activate?

• Somatic reflexes: activate skeletal muscles
• Autonomic (visceral) reflexes: activate visceral effectors (smooth or cardiac muscles or glands)

400

• Describe inborn (intrinsic) reflexes and learned reflexes. Give examples of each

• Inborn (Intrinsic) reflex: predictable motor response to stimulus; no help from brain. Ex: maintain posture, control visceral activities, spinal reflexes
• Learned reflex: results from practice/repetition. Ex: riding a bike, driving a car, etc.

500

• Name five general characteristics of polysynaptic reflexes:

• Involve pools of interneurons
• Are intersegmental in distribution
• Involve reciprocal inhibition
• Have reverberating circuits which prolong reflexive motor response
• Several reflexes cooperate to produce coordinated, controlled response

Reflex Types

100

Name five different types of reflexes.

• Stretch reflex
• Tendon reflex
• Flexor reflex
• Cross-extensor reflex
• Superficial reflex

200

Describe superficial reflexes

• Caused by gentle cutaneous stimulation
• Depend on upper motor pathways and cord-level reflex arcs

300

Describe the flexor reflex:

• Spinal reflex-brain not involved but can override though
• Withdraw reflex
• Initiated by painful stimulus
• Causes automatic withdrawal of threatened body part
• Ipsilateral and polysynaptic
• Protective

400

Summarize the stretch reflex

• Spinal reflex initiated by stretching muscle spindles
• Causes stretched muscle to contract, relaxes antagonist
• Monosynaptic except antagonist inhibition is polysynaptic (has an interneuron)
• Ipsilateral (same side of body)

500

What is the tendon reflex and why is it important?

• Opposite of the stretch reflex- muscle relaxation and lengthening in response to tension
• Polysynaptic
• Responsible for smooth onset and termination of muscle contraction
• Prevents tear of muscles and tendons

Mixed Bag

100

To smoothly coordinate skeletal muscle, the nervous system must receive information about:

• Length of muscle from muscle spindles
• Amount of tension in muscle from tendon organs
• Proprioceptors

200

What are the steps in a general reflex arc?

• Sensory receptor recognizes stimulus, if stimulated sensory input goes to:
• Sensory neuron which then goes to spinal cord
• Integration center (interneuron) to motor
• Motor neuron
• Effector (muscle contraction)

300

What is reciprocal inhibition? Give example

• Afferent fibers synapse with interneurons that inhibit motor neurons of antagonistic muscles
• If antagonists relax, they cannot resist shortening of stretched muscle caused by main reflex arc
• Ex: in patellar reflex, stretched muscle quads contracts and antagonists hamstrings relax

400

What is the Babinski reflex? What may it indicate if found in an adult?

• a reflex action in which the big toe remains extended or extends itself when the sole of the foot is stimulated
• Normal in infants
• If found in adult may indicate CNS damage

500

• The higher centers in the brain can inhibit spinal reflexes by:

• Stimulating inhibitory neurons
• Creating IPSPs at reflex motor neurons
• Suppressing postsynaptic neurons