Chapter 13 - Spinal Reflexes

What do Visceral Reflexes control and what do they include?

- Controls actions of smooth and cardiac muscles and glands

What do Somatic Reflexes control and what do they include?

- Controls skeletal muscle contractions - Includes superficial and stretch reflexes

Monosynaptic = ... Polysynaptic = ...

- One synapse - Multiple synapses

What are examples of Acquired Reflexes?

- Riding a bike - Pressing on breaks when someone cuts you off in traffic

What are examples of Visceral Reflexes?

- Smooth, cardiac muscle - Glands - Adipose tissue

What are examples of the Ipsilateral Reflex Arc?

- Stretch reflex - Tendon reflex - Withdrawal reflex

What are examples of Somatic Reflexes?

- Superficial reflexes of skin, mucous membranes like corneal reflex and gag reflex - Stretch or deep tendon reflexes

What are examples of Innate Reflexes?

- Withdrawal from pain - Chewing - Suckling - Tracking objects with eyes

What are the 5 steps in a Neural Reflex?

1. Arrival of stimulus, activation of receptor 2. Activation of sensory neuron 3. Information processing by postsynaptic cell 4. Activation of motor neuron 5. Response of peripheral effector

Reflexes can be classified by...

1. Development 2. Type of motor response 3. Complexity of circuit 4. Processing site of information

Reflex development can either be what 2 types?

1. Innate reflex (genetically determined) 2. Learned reflex

What are the 2 types of Reflex Arcs?

1. Ipsilateral reflex arc 2. Crossed extensor reflex arc

Reflex Complexity of Circuit can either be what 2 types?

1. Monosynaptic 2. Polysynaptic

Reflex response can either be what 2 types?

1. Somatic reflexes 2. Visceral (autonomic) reflexes

Reflex Processing Site can either be what 2 types?

1. Spinal reflexes 2. Cranial reflexes

Monosynaptic Reflexes are usually completed in how long?

20-40 msec

What is an example of a Monosynaptic Reflex?

A stretch reflex

What are Postural Reflexes

A type of stretch reflex that maintains normal upright posture

The 4th step in a Neural Reflex includes an ______________ _______________ generation in _______________ neurons.

Action potential; motor

Can Gamma Efferents allow voluntary muscle contractions?

Allows voluntary muscle contractions without triggering reflex

The Tendon Reflex also stimulates ______________________ muscle contraction to reduce ________________ on tendon.

Antagonistic; stress

What is the process of a Polysynaptic Reflex?

At least one interneuron between sensory neuron and motor neuron (involves more than one synapse)

What are Reflexes?

Automatic responses coordinated within spinal cord through interconnected sensory neurons, motor neurons and interneurons

Stretched muscles ______________________ maintains _____________________.

Automatically; balance

What are Visceral Reflexes?

Autonomic reflexes that control systems other than muscular system

What are Gamma Efferents?

Axons of the gamma motor neurons

What are Innate Reflexes?

Basic neural reflexes formed before birth

Where does the Reflex Arc begin and end?

Begins at receptor and ends at peripheral effector

What are Intrafusal Muscle Fibers?

Bundles of small, specialized fibers found inside

Sensory Neuron Axons enters ____________ in ______________ ______________.

CNS; dorsal root

How many spinal segments are involved in Spinal Reflexes?

Can involve a single spinal segment or multiple segments

What is the "Sensory Region" of Spinal Reflexes?

Central region of intrafusal fibers wound with dendrites of sensory neurons

Stretched muscles responds by ___________________________.

Contracting

Crossed Extensor Reflex Arc involves a ______________________ Reflex Arc.

Contralateral

What is detected by the Sensory Region of Spinal Reflexes?

Detects the stretchWajay of the intrafusal muscle

The Tendon Reflex prevents skeletal muscle from...

Developing too much tension

Polysynaptic Reflexes can produce ___________ or ________________ at _______________ ________________ ___________________ motor nuclei.

EPSPs; IPSPs; central nervous system

Alpha Motor Neurons are ultimately the _____________ of the reflex.

End

What is an example of a Withdrawal Reflex?

Ex. Flexor Reflex - pulling hand away from a hot stove

What happens if Reciprocal Inhibition does not occur?

Flexion will cause stretching of antagonistic muscle and cause reflex contraction of that muscle and extension occurs

Give an example of how Crossed Extensor Reflexes work simultaneously with Flexor Reflexes?

Flexor reflex causes leg to pull up and crossed extensor reflex straightens other leg to receive body weight

The Reflex Arc generally opposes what?

Generally opposes original stimulus through negative feedback

The 2nd step in a Neural Reflex is ______________ __________________ that leads to _________________ _______________.

Graded depolarization; action potential

Spinal Reflexes range in __________________ order of complexity.

Increasing

The greater the tension on the tendon...the greater the...

Inhibitory effect on the muscle, preventing muscle contraction

Reciprocal Inhibition inhibits what and how does it do it?

Inhibits the stretch reflex of antagonistic (extensor) muscle by using interneurons in spinal cord

What are Intrafusal Muscle Fibers innervated by?

Innervated by sensory and motor neurons

What are Polysynaptic Reflexes?

Interneurons that control more than one muscle group

Once Gamma Motor Neurons starts the reflex, it synapses back onto...

Intrafusal fibers to contract them

What are the receptors in stretch reflexes of Muscle Spindles?

Intrafusal muscle fibers

What are Somatic Reflexes?

Involuntary control of nervous system

Gamma Efferents are important in ______________ ______________ contractions.

Involuntary muscle

What are Extrafusal Muscle Fibers?

Large skeletal muscle fibers found on the outside

What is an example of a Postural/Stretch Reflex?

Leaning forward causes stretching of calf muscles which then reflexively contracts and pulls you back to keep you from falling forward

What are Acquired Reflexes?

Learned motor patterns that are rapid and automatic

Monosynaptic Reflexes have the _____________ delay between _____________ input and _______________ output.

Least; sensory; motor

What do Extrafusal Muscle Fibers maintain?

Maintains tone and contract muscle and contracts when stimulated at greater levels

What is the function of Muscle Spindles?

Monitors the stretching of muscle

Polysynaptic Reflexes are _____________ complicated than Monosynaptic Reflexes.

More

What are Withdrawal Reflexes?

Moving body part away from stimulus like pain or pressure

What is the receptor of Monosynaptic Reflexes?

Muscle spindle

Neural Reflexes are basic building blocks of _____________ _______________.

Neural function

What are Alpha Motor Neurons?

Neurons that contract extrafusal fibers and reduces muscle spindle stretching

The 3rd step in a Neural Reflex is triggered by __________________________ released from the ___________________ cell.

Neurotransmitters; presynaptic

The 5th step in a Neural Reflex is triggered by _____________________________ to cause _____________ _________________ contraction.

Neurotransmitters; skeletal muscle

Where do Cranial Reflexes occur?

Occurs in brain

Where do Spinal Reflexes occur?

Occurs in spinal cord

Where does Ipsilateral Reflex Arc occur?

Occurs on the same side of the body as the stimulus

Where does Crossed Extensor Reflex Arc occur?

Occurs on the side of the body opposite of the stimulus

One Neural Reflex produces __________ _______________ ______________.

One motor response

The 1st step in a Neural Reflex could have ______________ or ______________ changes.

Physical; chemical

What is an example of the Reflex Arc?

Presence of a hot stimulus touching your skin causes you to reflexively jerk away from the stimulus, thus removing the stimulus from your skin

What do Reflexes preserve and how?

Preserves homeostasis by making rapid adjustments in the function of organs/organ systems

Why are Spinal Reflexes very rapid?

Rapid because the more time it takes could result in more room for injury to occur

What are Neural Reflexes?

Rapid, automatic responses to specific stimuli

What are Spinal Reflexes?

Rapid, autonomic nerve responses triggered by specific stimuli

What is a required for a Flexor Reflex to work?

Reciprocal inhibition

Gamma Efferents complete the ______________ _________.

Reflex arc

Crossed Extensor Reflexes are maintained by __________________ ________________.

Reverberating circuits

What is the process of a Monosynaptic Reflex?

Sensory neuron synapses directly onto motor neuron (only 1 synapse involved)

The Tendon Reflex has ________________ __________________ unlike ________________ _____________ or ______________________.

Sensory receptors; muscle spindles; proprioceptors

Reflexes produce _______________ and _____________ reflexes.

Simple; complex

Crossed Extensor Reflexes occur _________________________ and is coordinated with _______________ _____________.

Simultaneously; flexor reflex

The more synapses, the _________________ the reaction.

Slower

Spinal Reflexes are controlled by what?

Spinal cord alone, not the brain

Gamma Motor Neurons ultimately ______________ the reflex.

Starts

What does a Stretch Reflex protect?

Stretch reflex protects muscles from over stretching

What can many Stretch Reflexes be?

Stretch reflexes are postural reflexes

What stimulates Alpha Motor Neurons?

Stretching of muscle spindle stimulates sensory neuron to generate action potentials which stimulate Alpha Motor Neurons

What are Muscle Spindles surrounded by?

Surrounded by extrafusal muscle fibers

After Sensory Neuron Axons enters into the CNS in the dorsal root what happens?

Synapses onto motor neurons (gamma motor neurons) in anterior gray horn of spinal cord

Too much tension in skeletal muscles can cause...

Tearing or breaking tendons

What does a Tendon Reflex protect?

Tendon reflex protects muscles from over contraction

The Tendon Reflex monitors _________________ in tendon.

Tension

The strength and extent of the Withdrawal Reflex response depends on what?

The intensity and location of the stimulus

Each time a particular reflex is activated, it produces ________ ______________ motor response.

The same

What is the Reflex Arc?

The wiring of a single reflex

Gamma Efferents are important in involuntary muscle contractions by allows Central Nervous System to do what? Via what?

To adjust sensitivity of muscle spindles via gamma efferents

What are Intersegmental Reflex Arcs?

When many segments interact and produce highly variable motor responses

What is an example of a Crossed Extensor Reflex Arc?

You step on a lego with your left foot on your left side, so you lift your foot and shift your balance to your right foot