Human Reflexes and Eye Function

Sensory neurons are responsible for transmitting signals from sensory receptors, which are located in the eyes, nose, taste buds, skin, and ears, to the central nervous system (CNS).

Relay neurons, also known as interneurons, are found in the CNS and act as intermediaries between the sensory and motor neurons. They receive signals from sensory neurons and transmit them to motor neurons.

Motor neurons receive signals from the CNS and transmit them to muscles and glands. They initiate voluntary and involuntary movements.

A reflex response is an involuntary, automatic reaction to a stimulus, which occurs without conscious thought. It bypasses the brain and involves a direct route from sensory receptors to motor neurons.

Reflex responses are essential for survival as they allow rapid and automatic reactions to potentially harmful stimuli, minimizing damage to the body. Examples include withdrawing from a sharp object or blinking when an object approaches the eye.

A reflex arc is the pathway that a reflex response takes. It involves sensory neurons, relay neurons, and motor neurons working in sequence.

Voluntary responses involve conscious thought and decision-making. They are initiated by the brain and involve processing information about the situation before taking action. Examples include reaching for a cup of coffee or deciding to go for a walk.

Involuntary responses, also known as reflexes, are initiated without conscious thought. They happen automatically in response to stimuli and do not involve the brain's conscious processing. Examples include blinking, withdrawing from a painful stimulus, and knee-jerk reactions.

The point where the optic nerve connects to the retina. This area lacks light-sensitive cells, resulting in a blind spot.

A reflex that controls the size of the pupil to adjust to different light conditions. In dim light, the pupil dilates (widens) to allow more light in. In bright light, the pupil constricts (narrows) to prevent damage.

Light-sensitive cells found in the retina that detect light. They are responsible for our ability to see in low light conditions.

Light-sensitive cells found in the retina that detect color. They are responsible for our color vision.

The transparent outer layer of the eye that protects the eye and helps focus light.

The colored part of the eye that controls the amount of light entering the eye.

The lens of the eye focuses light onto the retina.

The inner layer of the eye that contains light-sensitive cells (rods and cones) that convert light into electrical signals that the brain interprets as images.

The pupil reflex is the automatic adjustment of the pupil size in response to changes in light intensity.

In dim light, the radial muscles contract, causing the pupil to dilate (expand) and allow more light to enter the eye.

In bright light, the circular muscles contract, causing the pupil to constrict (shrink) and reduce the amount of light entering the eye.

The radial and circular muscles of the iris work antagonistically, meaning they have opposite actions. When one contracts, the other relaxes.

The pupil reflex is a good example of antagonistic muscle action because the radial and circular muscles work together to control the amount of light entering the eye.

The process by which the eye focuses on objects at different distances.

Tiny, elastic fibers that connect the lens to the ciliary muscles. They control the shape of the lens during accommodation.

Circular muscles in the eye that contract or relax to change the shape of the lens.

When the ciliary muscles contract, the suspensory ligaments loosen, allowing the lens to become thicker and refract light more.

When the ciliary muscles relax, the suspensory ligaments tighten, making the lens thinner and refracting light less.

The bending of light as it passes from one medium to another, such as from air to the lens of the eye.

The ability of the lens to change its shape to focus on objects at different distances. It allows us to see clearly both near and far.

Type 1 diabetes is a condition where the pancreas cannot produce insulin, leading to high blood glucose levels.

Insulin is a hormone that helps regulate blood glucose levels by allowing glucose to enter cells for energy.

Glucagon is a hormone that increases blood glucose levels by prompting the liver to release stored glucose.

Glycogen is a complex carbohydrate that stores glucose in the liver and muscles.

People with Type 1 diabetes need to inject insulin to regulate their blood sugar levels.

Symptoms of Type 1 diabetes include excessive thirst, fatigue, blurry vision, weight loss, and even unconsciousness in severe cases.

Maintaining a balanced diet, regular exercise, and monitoring blood sugar are crucial for managing Type 1 diabetes.

Type 2 diabetes, which is linked to lifestyle factors such as obesity, is not covered in the specification.

A plant's response to a stimulus, such as light or gravity, by growing either towards or away from it.

Growth of a plant towards a stimulus, like light.

Growth of a plant away from a stimulus, like gravity.

A plant's response to gravity, causing it to grow either upwards or downwards.

Growth of a plant towards light, usually seen in stems.

Shoots exhibit positive phototropism (grow towards light) and negative gravitropism (grow away from gravity).

Roots exhibit negative phototropism (grow away from light) and positive gravitropism (grow towards gravity).

Placing a plant on its side can demonstrate its gravitropic response. The stem will grow upwards and the roots will grow downwards.