Lab 11
A reflex arc must involve interneurons for processing in the spinal cord.
False
A reflex arc is termed ______ when the receptor and effector organs of the reflex are one the same side of the spinal cord. For example, this effect occurs when the muscles in your left arm contract to pull your ____ hand away from a hot object.
ipsilateral; left
Alpha motor neurons
large motor neurons controlling the extrafusal muscle fibers
Intrafusal fibers
modified skeletal muscle fibers within a muscle spindle
The simplest reflex; muscles contract in response to a stretch
stretch reflex
The _____________ tract relays proprioceptive information to the cerebellum for processing.
dorsal spinocerebellar
The stretch reflex being demonstrated in the picture is the
(hammer on the inside of the forearm) biceps reflex
Identify the reflex being demonstrated in the picture.
(picture shows a woman with a knee instrument being tapped on the knee) patellar reflex
Predict the normal response to the reflex shown in the picture.
(sharp instrument on the bottom of feet) curling (flexion) of the toes and plantarflexion
Put the following events that occur in a reflex arc in the correct order.
1.A sensory receptor detects a stimulus 2.A sensory neuron conducts action potentials through the nerve to the spinal cord 3. The sensory neuron synapses with an interneuron 4. The interneuron synapses with a motor neuron 5. The motor neuron conducts action potentials through the anterior root and spinal nerve to an effector organ
A simple spinal reflex typically involves how many neurons?
3
Extrafusal fiber contraction
Activates spindle stretch receptors and causes and increased rate of action potentials in the afferent neuron
Sensory stimuli enter the spinal cord via
Afferent Axons
Muscle-spindle stretch receptors
Connective-tissue capsules containing intrafusal muscle fibers and stretch receptors
Damage to the ventral root of a spinal nerve would mean that the sensory input of the reflex arc would be interrupted.
False
Prevents contracting muscles from applying tension to tendons
Golgi tendon reflex
Flexor reflex
Involve ipsilateral excitation of flexors and inhibition of extensors
Crossed-extensor reflex
Marked by actions to stabilize the limb opposite of injurious agents Involve contralateral excitation of extensors and inhibition of flexors
Stretch reflex
Muscle spindles are the receptor Involve ipsilateral excitation of agonists and inhibition of antagonists Initiated by an increase in muscle length
Passive muscle stretch
Results in maintained stretch of the central region of intrafusal fibers and an intermediate rate of action potential firing
Golgi tendon organs
Sensory receptors that monitor changes in muscle tension
Muscle spindle
Sensory receptors that monitor muscle length and the rate of change in muscle length
Interneurons are located in the
Spinal Cord
Tendon reflex
Tendon organs are the receptors Initiated by excessive force in the tendon
Sensory receptors are found
Throughout the body
Simple spinal reflexes occur independent of the brain.
True
Hyperactive reflex
abnormally strong reflex may be accompanied by clonus may indicate damage to the brain
Rhythmic oscillations between flexion and extension when the muscle reflex is tested are called ____________.
clonus
A reflex arc is _______ when the sensory impulses from a receptor organ cross over through the spinal cord to activate effector organs in the _____ limb.
contralateral; opposite
Response to a withdrawal reflex; causes extension of the opposite limb
crossed extensor reflex
Hypoactive reflex
diminished or absent reflex may suggest muscle disease may indicate damage to the neuromuscular junction
Reflexes involving painful stimuli, such as touching hot objects or stepping on sharp objects are
examples of withdrawal reflexes
Alpha-gamma coactivation
removes tension on the stretch receptors and lowers the rate of action potential firing
For example, this occurs when you step on a sharp object with your left foot and then contract the muscles in your ____ leg to maintain balance as you withdraw from the damaging object.
right
Extrafusal fibers
skeletal muscle fibers that form the bulk muscle and generate its force and movement
Gamma motor neurons
small motor neurons controlling the intrafusal muscle fibers
Removes a body part from a painful stimulus
withdrawal reflex