Reflexes

What Are Reflexes?

A reflex is a quick, automatic movement your body makes. You do it without thinking about it. It’s your body’s way of reacting to something right away.

A common example is when your provider taps your knee during a checkup. Your leg kicks out on its own. You didn’t tell it to move — your body just did it. You might only notice after it happens. Other examples include gagging (to prevent choking), blinking (to prevent eye harm) and shivering (to regulate body temperature).

Reflexes are usually predictable. That means you react in the same way to certain things. You have some that go away when you’re a baby and some that stay with you your entire life. Reflexes have an important role in protecting you and keeping your body working properly.

Sometimes, reflexes don’t work the way they should. If that happens, a healthcare provider can help figure out what’s going on and how to manage it.

Types of reflexes

You have several reflexes in your body. They’re grouped into two categories:

• Somatic: These are automatic in your skeletal muscles.
• Autonomic: These are automatic in your internal organs.

Somatic reflexes protect your body and keep your muscles working properly. Common ones include:

• Deep tendon reflex (stretch reflex): This helps your muscles stay ready and balanced. For example, your doctor taps just below your knee, and your leg kicks out.
• Withdrawal reflex: This keeps you safe by pulling your body away from danger. For example, you touch something hot and quickly pull your hand back.
• Golgi tendon reflex: This protects your muscles from getting hurt when they’re under too much stress. For example, you’re lifting something heavy and your arms suddenly give out.

Autonomic reflexes keep your body’s systems running smoothly. Common ones include:

• Baroreceptor reflex: It keeps your blood pressure steady, especially when you stand up quickly.
• Cardiovascular reflex: It changes your heart rate and blood pressure based on whether you’re resting or active.
• Digestive reflex: It moves food through your stomach and intestines.
• Excretory reflex: It controls the muscles that help you pee and poop.
• Pupillary light reflex: It makes your pupils get smaller in bright light to protect your eyes.

What’s the purpose of a reflex?

Since you’re not thinking about them, you probably aren’t expecting reflexes to have a purpose, but they do have important jobs. These include keeping you:

• Protected: If you’re overusing a specific muscle, some kick in to prevent muscle injury. This stops you from pushing yourself beyond your body’s limit.
• Regulated: Your autonomic nervous system controls things like your heartbeat and body temperature. It works by using reflex circuits that keep your body in balance.
• Safe: Reflexes are your body’s natural lifeguard to get you out of harm quickly. Imagine resting your hand on a hot surface. Your skin picks up the heat and triggers your body to pull away quickly — all without needing to think about it. Without that safety measure in place, you’d get a bad burn.
• Upright: Some reflexes help you balance and keep your posture. This helps you coordinate movements and sit and stand without falling over.

How does a reflex work?

Reflexes happen on a special pathway in your nervous system called a reflex arc. You can think of the arc like a shortcut that lets your body react without needing to think about it. Here’s how it works:

1. A sensor notices something: Special nerve endings in your skin, muscles or tendons detect a change. This could be temperature change, a stretch or pressure.
2. A message travels to your spinal cord: A sensory neuron creates and carries a message toward your spinal cord (or brainstem).
3. Your body decides how to react: Usually decisions take time, but this one happens automatically. Inside your spinal cord, the message connects to a motor neuron. Sometimes, it connects through a helper neuron called an interneuron. These are the decision makers.
4. A motor nerve sends the message out: This nerve carries the new message out to the muscle or organ, telling it what to do.
5. You respond: Your muscle tightens or relaxes. Or you might blink, pull away or kick.

This process skips the thinking part in your brain, which is why it works so quickly. Your brain will eventually get the message, but only after the response happens.

How doctors test reflexes

You’ve probably had these checked at your provider’s office. It’s a common test that helps show how well your nervous system is working.

To do the test, your provider uses a small rubber tool called a reflex hammer. They gently tap on tendons. These connect muscles to bones.

The most common test is the knee-jerk test. Your provider taps just below your kneecap. Your leg should kick out immediately. They may test other areas, too, depending on what they’re looking for.

It’s best to stay relaxed during the test. Take a few deep breaths and try not to focus on where the tapping is happening. That way, your body reacts naturally.

The test doesn’t hurt. It’s very quick.

Other common tests include:

• Corneal reflex test: This test checks if you blink when something lightly touches or comes close to your eye.
• Gag reflex test: Your provider gently touches the back of your throat with a swab to see if it triggers a gag response.
• Plantar reflex test: Your provider runs a reflex hammer along the bottom of your foot to see which way your toes move.
• Pupillary light reflex test: A light shines into your eyes to check if your pupils (the dark centers of your eyes) change size.

What are some reflex disorders?

Sometimes, reflexes don’t work the way they should. They may be overactive (hyperreflexia) or underactive (hyporeflexia). This can cause your muscles to twitch, tighten too much or not move at all when they should. A healthcare provider can help find the cause and recommend treatment.

Some conditions that can affect these include:

1. Amyotrophic lateral sclerosis (ALS)
2. Electrolyte imbalances
3. Low body temperature
4. Low pain tolerance
5. Low thyroid hormone
6. Multiple sclerosis (MS)
7. Nerve damage (peripheral neuropathy)
8. Nervous system injuries
9. Neuropathy
10. Stroke

Reflexes may naturally slow down with aging. This is normal. But if you notice big changes or if your reflexes stop responding like they used to, it’s a good idea to talk to your provider.