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