28.1 – How a Nerve Carries a Message
• A neuron is called a nerve cell. It consists
of the cell body, dendrites, and an axon.
• When not conducting an impulse, the neuron has a resting
potential that is more negative on the inside.
• When conducting a nerve impulse, the inside becomes
more positive temporarily.
• Myelin sheaths around axons insulate it and help impulses
to move faster.
• Neurotransmitters carry impulses from one neuron to
another across a gap known as a synapse.
• Many drugs, including opium and alcohol, interfere
with the function of neurotransmitters.
• Some neurotransmitters travel from nerves to muscles,
where they trigger muscle contraction.
28.2 – The Nervous System
• Central nervous system – brain & spinal cord
• The brain is made up of the cerebrum, the cerebellum,
and the brain stem.
• The cerebrum is the control center.
• The cerebellum coordinates muscle activity.
• The brain stem regulates involuntary actions.
• The spinal cord transmits impulses to and from the
brain.
• The peripheral nervous system consists of all the nerves
outside the CNS. It contains 2 types of nerves: sensory and motor.
• A reflex is an involuntary response to a stimulus.
• Autonomic nervous system – controls involuntary functions
28.3 – The Sense Organs
• Sensory neurons in the inner ear enable a person to
hear, maintain balance, and monitor orientation in space.
• Sensory neurons in the eye enable a person to see colors,
fine details, and minute movements.
• In the retina, you have rods to detect B&W and
cones to detect color.
• Sensory neurons in the tongue enable a person to distinguish
between sweet, sour, bitter and salty tastes.
• Smell and taste are examples of chemical reception. |