| A | B |
|---|
| action potential | temporary change in a neutron's polarity that moves an electrical current through a neuron |
| autonomic system | two groups of nerves, sympathetic and parasympathetic, that control many reflexes |
| axon | part of a neuron that conducts impulses away from the cell body |
| central nervous system | the brain and one, or more, nerve cords in bilaterally symmetrical animals |
| cerebellum | motor area of the brain |
| cerebrum | part of the brain that controls speech, reasoning, emotions and personality |
| cone cells | photoreceptor cell that distinguishes colors |
| cornea | front surface of the eye; it admits light |
| dendrite | portion of a neuron that transmits impulses toward the cell body |
| interneuron | neuron that carries impulses from sensory to motor neurons |
| lens | eye structure that focuses light on the retina |
| medulla oblongata | central part of the brain that controls heart rate |
| motor neuron | specialized cell that carries impulses from the brain or spinal cord to an effector |
| nerve | bundle of neuronal axons |
| neuron | specialized nerve cell |
| neurotransmitter | chemical agent that conducts nerve impulses across the synapse |
| peripheral nervous system | the sensory and motor neurons connected to the CNS |
| reflex | involuntary or automatic response to a stimulus |
| reflex arc | the path a nerve impulse takes during a reflex action |
| resting potential | unequal distribution of ions across the cell membrane that polarizes a neuron |
| retina | innermost layer of the eye |
| rod cells | type of photoreceptor cell that works in very dim light but does not distinguish colors |
| sensory neuron | specialized cell that transmits impulses from receptors to the brain or spinal cord |
| sensory-somatic system | part of the human peripheral nervous system that controls both conscious and involuntary responses |
| synapse | small, fluid filled space between neurons across which impulses are transmitted |
