The Nervous System Part 1

The Nervous System

The body’s primary control and communication network that coordinates movements, processes sensory information, and regulates internal functions

Neurons

These are nerve cells.

Nerve

These are made up of bundles of neuron connecting the brain and spinal cord with other parts of the body.

Tract

A bundle of nerve fibers actually within the brain and spinal cord.

Ascending Nerve Tracts

Carry nerve impulses toward the brain.

Descending Nerve Tracts

Carries nerve impulses away from the brain.

Ganglion

A nerve center made up of a cluster of nerve cell bodies outside the central nervous system.

Plexus

A network of intersecting spinal nerves.

Innervation

Refers to the supply of nerves to a specific body part.

Receptors

Are sites in the sensory organ (eyes, ears, skin, nose, and taste buds) that receive external stimulation.

Stimulus

Anything that excites or activates a nerve and causes the electrical impulse to move along the nerve.

Reflex

An automatic, involuntary response to some change, either inside or outside of the body.

Neuron Cell Body

The main part of this cell. It holds the nucleus, mitochondrion, and other cell structures just like any other cell.

Dendrites

These are the processes that receive impulses and conduct them toward the cell body.

Axon

These are the processes that conduct impulses AWAY from the nerve cell.

Myelin Sheath

Made of Schwann cells and protects many axons.

The Central Nervous System

This is made up of the brain and spinal cord. They are protected by the meninges, which is a system of membranes.

What are the three layers of the meninges?

Dura Mater, Arachnoid membrane, and Pia Mater.

Dura Mater

This is the very thick, tough, outermost membrane. It lines the inside of the cranium and vertebral column.

Epidural Space

The space between the bone and the dura mater.

Arachnoid Membrane

This is the middle layer of the meninges that looks like a spiderweb.

Pia Mater

The innermost layer of meninges. It contains a rich supply of blood vessels nourishing the membranes and nerve tissue.

Cerebral Spinal Fluid

Produced by capillaries in the brain. It is clear, colorless, and watery and flows throughout the brain and around the spinal cord. It functions to cushion the structures. It also provides nourishment to the brain and spinal cord.

Brain

Controls the functions of the body. It is divided into many area and structures. Each area of the brain controls a specific set of functions for the body.

Cerebrum

Largest part of the brain. Responsible for controlling and integrating voluntary motor functions and sensory functions in the body.

Cerebral Cortex

Made up of gray matter. It is the outer layer of the cerebrum and is made up of elevated folds (gyri) and deep fissures (sulci).

Cerebral Hemispheres

Brain is divided into left and right. The left controls the functions of right side of the body while the right controls the left side of the body.

Lobes of the Brain

Each cerebral hemisphere is subdivided into lobes and is named for the bone directly underneath the brain area.

Frontal Lobe

This lobe controls skilled motor functions, memory, and behavior.

Parietal Lobe

This lobe receives and interprets nerve impulses to form sensory receptors in the tongue, skin, and muscles.

Occipital Lobe

This lobe controls eyesight.

Temporal Lobe

This lobe controls hearing and smell as well as the ability to create, store, and access new information.

Thalamus

Located below the cerebrum. It relays sensory stimuli from the spinal cord and midbrain to the cerebral cortex.

Hypothalamus

It performs many regulatory functions for the body.

Brain Stem

This is a stalk-like structure that connects the cerebral hemispheres with the spinal cord. it is made up of the midbrain, pons, and medulla oblongata.

Spinal Cord

A long, tube-like structure beginning at the brainstem in the brain and ending at the bottom of the spinal column. It contains all the nerves that control the limbs and lower part of the body.

Peripheral Nervous System

Consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves extending from the spinal cord. These nerves control the functions of body part and muscles away from the spinal column and brain.

What are the three types of specialized peripheral nerves?

Autonomic Nerve Fibers, Sensory Nerve Fibers, and Somatic Nerve Fibers.

Peripheral Spinal Nerves

These nerves are grouped together and name based on the region of the body they innervate. Within each region, the nerves are referred to by number:

• Cervical nerves: C1-C8

• Thoracic Nerves: T1-T12

• Lumbar Nerves: L1-L5

• Sacral Nerves: S1-S5

What are the two divisions of the autonomic nervous system?

Sympathetic Nerves and Parasympathetic Nerves.

Sympathetic Nerves

These nerves prepare the body for emergencies and stress. They increase respiratory rate, heart rate, and blood flow to the muscles.

Parasympathetic Nerves

These nerves return the body to normal after the stress response.

Neurotransmitters

These are chemical substances that make it possible for messages to be transmitted from one neuron to another and to the target receptor. There are 200 to 300 neurotransmitters at work in the body.

Acetylcholine

This neurotransmitter is released at some synapses in the spinal cord and at neuromuscular junctions. It is involved in the impulses of muscle action.

Dopamine

This neurotransmitter is released in the brain. Too much or too little leads to serious disorders.

Epinephrine

This neurotransmitter is released in the brain and in the adrenal glands. Also called adrenal.

Norepinephrine

This neurotransmitter impacts arousal and alertness by increasing blood pressure, heart rate, and respiration. Also produced by the adrenal gland.

Serotonin

This neurotransmitter is released in the brain and impacts hunger, pleasure, and sleep.

Cranial Nerves

A set of 12 nerves that send electrical signals between your brain and different parts of your head, face, neck and torso. These signals help you see, smell, taste, hear and move your facial muscles.

Peripheral Nerves

There are 31 pairs of peripheral spinal nerves grouped together into cervical, thoracic, lumbar, and sacral divisions. Each pair controls specific organs and areas of the body.