2.3: Functional Organization of the Nervous System

What are neurons?

Neurons are cells that receive and transmit information across the body.

They receive sensory input from external stimuli, send motor commands to muscles, and transform and relay electrical signals.

What are the key parts of a neuron?

Dendrites, cell body (soma), nucleus, axon, myelin sheath, axon terminals

What are components of the central nervous system (CNS)?

The brain and the spinal cord

What do sensory (afferent) neurons do?

Process external stimuli by sending information to the CNS

What do motor (efferent) neurons do?

Take the information from the CNS to the muscles and glands to stimulate a reflex.

What do inter (association) neurons do?

Carries sensory information and regulates motor activity.

Which type of neuron carries information from the body’s tissues to the brain and spinal cord?

Sensory (afferent) neurons.

What is the purpose of a cell body?

Helps keep the cell alive and functioning.

What is the purpose of the dendrite?

Carries information inside from outside of the cell.

What is the purpose of an axon?

Passes information along to other nerve cells, muscles, or glands.

What is the purpose of a nucleus?

Stores and protects the cell’s genetic material (DNA), and regulates genetic expression.

What is the purpose of the myelin sheath?

Insulates the communication and transmission of electrical impulses along the axon.

What do neurons work through?

The use of electrical signals and neurotransmitters.

What are neurotransmitters?

Neurotransmitters are chemical molecules stored in vesicles in the axon terminal.

What are vesicles?

Vesicles are the node-like sacs at the end of an axon terminal?

How does communication with neurotransmitters work?

Communication happens across the synaptic gap—the space between two neurons.

What happens to any remaining neurotransmitters left between the synaptic gap?

The chemical is broken down or absorbed back into the neuron—that is called “reuptake”.

What does serotonin affect?

Mood, emotional states, and sleep.

What does dopamine affect?

Attention, movement, and pleasure.

Agonist

Increases neural activity flow and effect.

Antagonist

Decreases neural activity flow and effect.

What does the brain and spinal cord control?

Reflexive behavior

What does CNS rely on?

Sensory, motor, and interneuron communication.

What is the CNS protected by?

Cerebrospinal fluid.

Peripheral nervous system

Connects the brain and spinal cord to the rest of the body.

Somatic nervous system

Carries information from muscles, sense organs, and skin to the CNS.

Autonomic nervous system

Controls internal environment of the body, i.e. automatic breathing and swallowing—glands, organs, and some muscle.

Sympathetic nervous system

Prepares you for action—constricted muscles, dilated pupils, heart rate, sweat.

Parasympathetic nervous system

Calms you down after sympathetic—relaxed muscles, regular pupils, calm heart rate.