Organization of the Nervous System and Nervous tissue

Nervous system

The master control and communication system of the body.

Sensory input

Uses its millions of sensory receptors to monitor changes occurring both inside and outside the body. These changes are called stimuli, and the gathered information is called _____

Central nervous system

Consists of the brain and spinal cord

Integrating and command centers of the nervous system

Interpret incoming sensory information and issue instructions based on past experience and current conditions

Peripheral nervous system

Includes all parts of the nervous system outside the CNS

Spinal nerves carry impulses to and from the spinal cord

Cranial nerves carry impulses to and from the brain

Sensory/Afferent Division

Consists of nerves that convey impulses to the central nervous system from sensory receptors located in various parts of the body

Somatic sensory fibers

From the skin, skeletal muscles, and joints

Visceral sensory fibers

From the visceral organ

Motor efferent division

Carries impulses from the CNS to effector organs, the muscles, and glands

Somatic nervous system

Allows us to consciously/voluntarily control our skeletal muscles

Autonomic nervous system

Regulates events that are autonomatic/involuntary

Astrocytes

Star-shaped cells that help protect the neurons from harmful substances that might be in the blood

Also control the chemical environment in the brain

Microglia

Spider-like phagocytes that monitor the health of nearby neurons and dispose of debris, such as dead brain cells and bacteria

Ependyma cells

Neuroglia that line the central cavities of the brain and the spinal cord

Helps circulate the cerebrospinal fluid and forms a protective watery cushion

Oligondendrocytes

Not able to transmit nerve impulses and nerve lose their ability to divide

Form most brain tumors

Myelin sheaths

Neuroglia that wrap their flat extensions (process) tightly around the nerve fibers, producing fatty insulating coverings called _______

Schwann cells

Form the myelin sheath around nerve fibers in the PNS

Satellite cells

Act as protective, cushioning cells for peripheral neuron cell bodies

Cell body

The metabolic center of the neuron

Dendrites

Convey incoming messages (electrical signals) toward the cell body

Axons

Generate nerve impulses and typically conduct them away from the cell body

Axon hillock

Cone-like region where axon arises

Neurotransmitters

Chemicals contained in the tiny vesicles of axon terminals

Synaptic cleft

Tiny gap of each axon terminal

Synapse

Site/Junction where an impulse is transmitted from one neuron to another

Myelin

Whitish, fatty material covering of most long nerve fibers, which protects and insulates the fibers and increases the transmission rate of nerve impulses

Neurilemma

Outermost nucleated cytoplasmic layer of Schwann cells that plays an important role in fiber regeneration

Nodes of Ranvier

Gaps between the myelin insulation of Schwannn cells which insulates the axon of a neuron, and allows the generation of a fast electrical impulse

Multipolar neuron

With several number of processes

Consists of all motor and association neurons

Bipolar neuron

Neurons with two processes - 1 axon & 1 dendrite

Rare in adults, found only in some special sense organs where they act in sensory processing as receptors cells

Unipolar neuron

Has a single process emerging from the cell body

The process is very short and divides almost immediately into proximal (central)/axon and distal (peripheral) processes/dendrites

Receptors

Reacts to the stimulus by transducing environmental signals into a cellular response that directly or indirectly produces action potential along a sensory neuronn

Sensory neuron/ CNS Afferent

Carry action potentials, resulting from receptor activation, the Central Nervous System. They enter the spinal cord through the dorsal roots, or enter the brain via cranial nerves.

Integration center

It is the synapse in the CNS where information is processed.

Motor neuron /CNS Efferent

Carries action potential from the CNS toward the synapse with the target organ

Effector

Causes the reflex response. This can be a muscle or gland stimulated