Gathering information

• to monitor changes occurring inside & outside the body
• changes = stimuli

To process and interpret sensory input and decide whether action is needed

• A response to integrated stimuli
• The response activates muscles or glands

Consists of organs that interpret incoming sensory info and issue instructions based on past experiences and current conditions

• Brain
• Spinal Cord

Nerves extending from the brain and spinal cord.

• Spinal nerves
• Cranial nerves
• Functions: Serve as a communication lines among sensory organs (brain & spinal cord) and glands or muscles.

Carry impulses to and from the spinal cord

Carry impulses to and from the brain

Nerve fiber that carry info to the central nervous system

Carry info from the skin, skeletal muscles, and joints

Carry info from visceral organs

Nerve fibers that carry impulses away from the central nervous system

• 2 Subdivisions
• Somatic Nervous System
• Autonomic Nervous System

• Voluntary
• Consciously controls skeletal muscles

• Involuntary
• Automatically controls smooth and cardiac muscles and glands
• Further divided into the sympathetic and parasympathetic nervous systems

Nerve glue

Functions:

• Support
• Insulate
• Protect Neurons

Abundant, star-shaped cells

Functions:

• Brace Neurons
• From barrier between capillaries and neurons
• Control the chemical environment of the brain

Spider-like Phagocytes

Functions:

• Dispose of debris

Lines cavities of the brain and spinal cord. Cilia assist with circulation of cerebrospinal fluid.

Wrap around nerve fibers in the central nervous system

• Produce myelin sheaths around axons

Protect neuron cell bodies

Form myelin sheath in the peripheral nervous system

• Form around axons in a jelly-roll like fashion

nerve cells, specialized to transmit messages

Major regions

• Cell body
• Processes

Nucleus and metabolic center of the cell

Fibers that extend from the cell body

Conduct impulses toward the cell body

• Neurons may have hundreds

Conduct impulses away from the cell body

• Neurons have only one, arising from the cell body at the hillock
• End in terminals

Contain vesicles with neurotransmitters, and separated from each other by gaps

Gap between adjacent neurons

Junction between nerves

Whitish, fatty material covering axons

Gaps in myelin sheaths along the axon

Cell bodies and unmyelinated fibers and cell bodies

In the brain: outer layer in the cerebral cortex; composed mostly of cell bodies.

Clusters of cell bodies within the white matter of the central nervous system

Collections of cell bodies outside the central nervous system

Bundles of nerve fibers in the CNS

Bundles of nerve fiber in the PNS

Collections of myelinated fibers (tracts), fiber tracts deep to the gray matter

Carry impulses from the sensory receptors to the CNS

Simpler types of sensory receptors in the skin

Detect stretch or tension

Carry impulses from the central nervous system to viscera, muscles, or glands

Found in neural pathways in the CNS, connect sensory and motor neurons

Many extensions from the cell body

• All motor and interneurons are multipolar
• Most common structure

One axon and one dendrite

• Located in special sense organs (nose and eye)
• Rare in adults

Have a short single process leaving the cell body

• Sensory neurons found in PNS ganglia
• Conduct impulses both toward and away from the cell body

There are fewer positive ions sitting on the inner face of the neuron's plasma membrane than on its outer face

Ability to respond to a stimulus and convert it to a nerve pulse

Ability to transmit the impulse to other neurons, muscles, or glands

The plasma membrane at rest is polarized, as long as the inside is more negative then the outside the cell stays at rest.

Activates the neuron to initiate and transmit a long-distance signal

Rapid, predictable, and involuntary responses to a stimulus

• occur over neural pathways called reflex arcs

Reflexes that stimulate the skeletal muscles.

• Ex: pulling you hand away from a hot object

Regulate the activity of smooth muscles, the heart, and glands

• Ex: Regulation of smooth muscles, heart and blood pressure, glands, digestive system.

Reacts to a stimulus

Carries messages to the integration center

Process info and directs motor output

Carries message to an effector

Is the muscles or gland to be stimulated

Simplest type

• Ex: Patellar (knee-jerk) reflexs

Consists of 5 elements: receptors, sensory neuron, interneuron, motor neuron, and effector

• Ex: flexor (withdrawal) reflex

Divided by fissures (deep grooves)

Sends impulses to skeletal muscles, located in frontal lobe