Nervous System Functions and Tissues

• The nervous system is a network of billions of nerve cells.
• Nerve cells are linked together in a highly organized way.
• The nervous system is the body's rapid control center.

Basic Functions of the Nervous System

• Sensation monitors changes and events inside and outside the body.
• Stimuli are the changes/events monitored by cells, which are called receptors.
• Integration is the parallel processing and interpretation of sensory to determine appropriate response.
• Reaction is motor output.
• Reaction is the activation of muscles or glands via neurotransmitter release.

Nervous Tissue

• Nervous tissue is highly cellular and has 2 cell types.
• Neurons are functional, signal conducting cells.
• Neurons do not divide, are long lived, have high metabolic activity, and are electrically excitable.
• Neuroglia supports, nourishes, and protects neurons.
• Neuroglia can divide.
• There are smaller cells that greatly outnumber neurons by about 5-50.
• There are 6 types of supporting cells.
• 4 supporting cells are found in the CNS, and 2 in the PNS.
• A nerve is a bundle of neurons carrying multiple signals.
• A neuron transmits electrical impulses (AP).
• Nerves carry motor or sensory stimuli.

Functional Classification of Neurons

• Sensory neurons sends sensory information towards the brain from receptors
• Association neurons (interneurons) are located between sensory and motor neurons
• Motor neurons sends motor signals towards muscles and glands from the brain

White vs. Gray Matter

• White matter consists of aggregations of myelinated and unmyelinated axons.
• Gray matter contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia.
• Nerves are bundles of processes in the PNS.
• Tracts are bundles of processes in the CNS; there is no connective tissue present.
• Ganglion is a cluster of nerve cell bodies in the PNS.
• Nucleus is a cluster of nerve cell bodies in the CNS surrounded by white matter.
• If not surrounded (Cortex).White matter: in the spinal cord is out, and in the brain is in.
• White matter contains myelinated and unmyelinated axons and has some cell bodies, but not neuronal.
• Gray matter: in the spinal cord is in, and in the brain is out.
• Gray matter contains myelinated and unmyelinated axons.
• Gray matter contains neuronal cell bodies and dendrites.
• A bundle of processes in the PNS is a nerve.
• Within a nerve, each axon is surrounded by an endoneurium.
• Groups of fibers are bound together into bundles.
• Bundles (fassicles) are bound by a perineurium.
• All the fascicles of a nerve are enclosed by an epineurium.

Organization of the Nervous System

• Anatomical divisions
• The central nervous system is the brain and the spinal cord.
• The central nervous system is the center of integration and control.
• The peripheral nervous system is the nervous system outside of the brain and spinal cord.
• The peripheral nervous system consists of 31 pairs of spinal nerves which carry information to and from the spinal cord.
• The peripheral nervous system consists of 12 pairs of cranial nerves which carry information to and from the brain

The Brain

• The brain is divided into the forebrain, midbrain and hindbrain.
• Forebrain (prosencephalon): Cerebrum (telencephalon) and Diencephalon (thalamus, Hypothalamus, Epithalamus and subthalamus).
• Midbrain (mesencephalon).
• Hindbrain (rhombencephalon): Pons, Medulla oblingata and Cerebellum.
• Brain stem = mid brain + hind brain - Cerebellum.