REFLEXES AND VISION - PHYSIOLOGY LAB EXAM 2

What is a reflex?

A reflex is a fast, involuntary, unplanned sequence of actions that predictably occurs in response to a particular stimulus.

Transmit impulses from receptors to CNS:

Afferent (Sensory)

Carry impulses neuron to neuron within CNS:

Association (Interneuron)

Transmit impulses from CNS to effectors (muscles/glands):

Efferent (Motor)

What are the five components of a reflex arc?

• Sensory Receptor

• Sensory Neuron

• Integrating Center (spinal cord or brain)

• Motor Neuron

• Effector (muscle or gland)

Describe the pathway from seeing a ruler drop to catching it?

Visual receptors detect the stimulus → afferent neurons send signal to CNS → integration center (brain) processes → efferent neurons send signal to hand muscles (effectors) → muscles contract to catch the ruler.

How is reaction time different from a reflex?

Reaction time is a voluntary response that involves conscious brain processing.

While a reflex is involuntary and travels only through the spinal cord.

What happens in the patellar reflex?

1. Sensory receptor: Muscle spindle in patellar tendon detects stretch

2. Sensory neuron: Sends impulse to spinal cord

3. Integrating center: Spinal cord (no brain involvement)

4. Motor neuron: Sends signal to quadriceps

5. Effector: Quadriceps contract, extending the leg

What happens during the plantar reflex?

Stroking the sole causes the toes to flex (curl down)—a normal response in healthy adults.

What is the Babinski sign?

Dorsiflexion (extension) of the big toe and fanning of other toes; normal in infants, abnormal in adults, indicating neurological damage.

What is the pupillary reflex?

An autonomic reflex in which pupils constrict in response to bright light and dilate in darkness; protects the retina and adjusts light intake.

Skeletal muscles as effectors, direct CNS-motor neuron connection.

Somatic

Smooth muscle, cardiac muscle, or glands as effectors; involve two neurons (preganglionic and postganglionic) in the efferent pathway.

Autonomic

Right body → left brain (typical of spinal nerves).

Contralateral

Right body → right brain (typical of cranial nerves).

Ipsilateral

Touch, pressure, movement—receptors throughout body.

Is what type of sense?

General senses

Vision, hearing, balance, taste, smell—have specialized organs.

Is what type of sense?

Special senses

Summarize the process of vision physiology.

1. Light refracts through the cornea and lens.

2. Photopigments in rods and cones change shape when hit by light.

3. This hyperpolarizes the photoreceptor membrane, stopping inhibitory neurotransmitters.

4. An action potential is sent through the optic nerve to the brain’s visual cortex

What is the autonomic reflex shown in the vision video?

The pupillary light reflex, where pupils constrict in bright light and dilate in darkness to control light entering the eye.

Which photoreceptor detects color?

Cones detect color; they require more light and have a higher threshold for activation than rods.

Is vision a general or special sense? Why?

Special sense because it has a dedicated organ (the eye) specialized for light detection and image processing

What is binocular vision?

The ability of two eyes to produce a single 3D image, allowing depth perception; comes with a tradeoff between field of view and binocular overlap.

What is a blind spot (scotoma)?

An area on the retina with no photoreceptors, corresponding to the optic disc where the optic nerve exits the eye.

What causes the blind spot?

The optic nerve passes through the retina, leaving an area without rods or cones; light falling there is undetected.

What is visual acuity and how is it measured?

Visual acuity measures the sharpness of vision, tested with a Snellen chart at 20 feet (e.g., 20/20 = normal, 20/40 = worse than normal).

Why is binocular vision important in the eye test with the cup and pencil?

Depth perception relies on input from both eyes.

With one eye covered, the brain cannot triangulate distance, making it harder to aim accurately.

What happens during the blind spot test?

When the image of an object falls on the optic disc, it disappears from view because that region lacks photoreceptors.

What does the astigmatism test check for?

Uneven curvature of the cornea or lens; if some lines appear blurred or lighter, astigmatism is present.

What is color blindness?

A vision defect caused by absence or dysfunction of cone photopigments, often inherited; affects perception of red/green hues.

Work in dim light, no color, low threshold.

What does this?

Rods

Work in bright light, color vision, high threshold.

What does this?

Cones