Biology coordination and response

What are the three main components of a response system?

Sense organs, coordinators, effectors.

What is the function of the nervous system?

To carry fast electrical impulses (1-120 m/s) allowing quick reactions to environmental changes.

What makes up the Central Nervous System (CNS)?

The brain and the spinal cord.

What is the Peripheral Nervous System?

All the nerves and ganglia outside of the brain and spinal cord.

What is a neuron?

A specialized cell that carries information as electrical impulses.

What is a nerve?

A bundle of hundreds or thousands of neurons.

What is the function of a sensory neuron?

To carry impulses from receptors to the CNS.

What is the function of a relay neuron?

To transfer messages between sensory and motor neurons within the CNS.

What is the function of a motor neuron?

To carry impulses from the CNS to effector organs.

What is the pathway of a nervous response?

Stimulus to the Receptor to the Sensory Neuron to the CNS (Relay Neuron) to the Motor Neuron to the Effector to the Response.

What is a reflex action?

A rapid, involuntary (automatic) response to a stimulus that does not involve conscious thought.

Why are reflex actions important?

They provide a fast, protective response to prevent injury.

What is a synapse?

The gap between two neurons.

How is an impulse transferred across a synapse?

Electrical impulse triggers release of neurotransmitters. 2) Chemicals diffuse across the gap. 3) They bind to receptors on the next neuron. 4) This stimulates a new electrical impulse.

Why are synapses important? (Two reasons)

They ensure impulses only travel in one direction. 2) They allow integration from many neurons (lots of axon terminals can signal to one neuron).

What is the function of the retina?

It contains light-sensitive receptor cells (rods and cones) that convert light into electrical impulses.

What is the function of the optic nerve?

To carry impulses from the retina to the brain.

What is the blind spot?

The point where the optic nerve leaves the retina; it has no receptor cells.

What is the fovea?

The area of the retina with a high concentration of cone cells, providing sharp, color vision.

What are rod cells and what is their function?

Receptor cells sensitive to low light intensity (night vision); they detect black and white.

What are cone cells and what is their function?

Receptor cells sensitive to high light intensity and color; they provide color vision.

Which structure refracts (bends) light into the eye?

The cornea (and the lens).

Which structure controls the amount of light entering the eye?

The iris (by adjusting the size of the pupil).

What happens to the pupil in dim light?

It dilates (gets larger). Radial muscles contract, circular muscles relax.

What happens to the pupil in bright light?

It constricts (gets smaller). Circular muscles contract, radial muscles relax.

What is the term for changing the shape of the lens to focus on near or far objects?

Accommodation.

How does the eye focus on a near object?

Ciliary muscles contract, suspensory ligaments slacken, lens becomes more rounded and thick.

How does the eye focus on a distant object?

Ciliary muscles relax, suspensory ligaments pull tight, lens becomes stretched thin and flat.