Nervous Syste

Central Nervous System (CNS)

Includes the brain and spinal cord, located in the dorsal cavity.

Peripheral Nervous System (PNS)

Consists of the nerves that connect the CNS with the rest of the body, located outside of the CNS.

Sensory Function

Nervous system function that involves gathering information from inside the body and the external environment and transmitting it to the brain.

Integrative Function

Nervous system function that involves interpreting sensory information brought to the CNS.

Motor Function

Nervous system function that conveys information from the CNS to muscles and glands, carrying out plans made by the CNS.

Neuroglia (Glial Cells)

Most abundant nerve cells in the CNS that support, protect, and insulate neurons.

Astrocytes

Star-shaped glial cells that support neurons, cover the surface of the brain, and help form the blood-brain barrier.

Ependymal Cells

Glial cells that line the inside cavities of the brain and assist in the formation of the CNS.

Neuron

Cell within the nervous system that enables communication and forms a vast network.

Sensory Neurons

Neurons that carry information to the CNS.

Motor Neurons

Neurons that carry information away from the CNS.

Interneurons

Neurons found only in the CNS that form connections between sensory and motor neurons and regulate motor activity.

Dendrites

Treelike extensions of a neuron that receive signals from other neurons and transmit signals to the cell body.

Cell Body

Part of a neuron that contains the nucleus and is essential for the life of the cell.

Axon

Long extension of a neuron that transmits signals away from the cell body.

Myelin Sheath

Protective and insulating covering of the axon.

White Matter

Clusters of cell bodies located in the CNS, referred to as nuclei.

Gray Matter

Small clusters of cell bodies located in the PNS, called ganglia.

Nerve Impulse

Electrical signals that convey information along a neuron.

Depolarization

Phase of the action potential where the cell charges from negative to positive.

Repolarization

Phase of the action potential where the inside of the cell becomes negative again.

Synapse

Space between neurons where information is chemically transmitted from one neuron to the next.

Synaptic Cleft

Space in the synapse where the axon terminal of one neuron does not physically touch the dendrite of another neuron.

Neurotransmitters

Chemical substances stored in tiny vesicles in the axon terminal that bind to receptors on the membrane of the postsynaptic neuron.

Limbic System

Functions in emotional states and behavior.

Reticular Formation

Special mass of gray matter that extends throughout the brain and diencephalon, alerting the cerebral cortex and regulating muscle tone.

Memory Areas

Three categories of memory:immediate, short-term, and long-term.

Bone

First layer of protection for the CNS, encasing the brain in the cranium and the spinal cord in the vertebral column.

Meninges

Three layers of connective tissue that surround the brain and spinal cord.

Cerebrospinal Fluid

Fluid that circulates within the subarachnoid space, providing cushioning for the brain and spinal cord.

Blood-Brain Barrier

Barrier that prevents potentially harmful chemicals from entering the CNS, regulated by astrocytes and capillary cells.

Spinal Cord

Located within the spinal cavity, about 17 inches long, gray on the inside and white on the outside.

Gray Matter

Located in the center of the spinal cord, shaped like a butterfly, composed primarily of cell bodies, interneurons, and synapses.

White Matter

Composed of myelinated and unmyelinated axons, grouped into sensory and motor tracts.

Sensory Tract

Carries information from the periphery up the spinal cord towards the brain (ascending tracts).

Spinothalamic Tract

Carries sensory information for touch, pressure, and pain from the spinal cord to the thalamus in the brain.

Motor Tract

Carries information from the brain down the spinal cord towards the periphery (descending tracts).

Decussation

Tracts cross over from one side to another, can result in conditions like quadriplegia or paraplegia.

Reflex

Involuntary response to a stimulus, controlled by the spinal cord.

Reflex Arc

Nerve pathway involved in a reflex, includes sensory receptors, afferent/sensory neurons, efferent/motor neurons, and an effector organ.

Peripheral Nervous System

Consists of nerves and ganglia located outside the central nervous system (CNS).

Cranial Nerves

Exit the brain and supply the head, neck, and shoulder areas.

Spinal Nerves

Attached to the spinal cord, divided into cervical, thoracic, lumbar, sacral, and coccygeal nerves.

Dermatome

Sensory area of skin innervated by a specific spinal nerve.

Autonomic Nervous System

Supplies organs, smooth muscle, and glands, divided into sympathetic and parasympathetic divisions.

Sympathetic Nervous System

Activated during periods of stress, prepares the body for fight or flight.

Parasympathetic Nervous System

Most active during nonstressful conditions, regulates digestion and reproductive function.

Cholinergic Receptors

Activated by acetylcholine, include muscarinic receptors (located on target organs) and nicotinic receptors (located within ganglia).

Adrenergic Receptors

Activated by norepinephrine, include alpha and beta adrenergic receptors located on target organs of sympathetic nerves.

Sensory System

Acts as a warning system, includes receptors for pain, touch, pressure, temperature, and proprioception.

Pain Receptors

Nociceptors, stimulated by tissue damage or distention, distributed throughout the body.

Touch and Pressure Receptors

Mechanoreceptors, respond to movement, pressure, or deformation of tissue, located in the skin.

Temperature Receptors

Thermoreceptors, respond to changes in temperature, located throughout the body.

Proprioception

Sense of orientation or position, relies on proprioceptors located in muscles, tendons, and joints.

Proprioceptors

Sensory receptors found in the inner ear that function in balance or equilibrium.

Cerebellum

A part of the brain that coordinates skeletal activity and receives sensory information from receptors.

Special Senses

Smell, taste, sight, hearing, and balance.

Sense of Smell

The Nose:Olfaction associated with sensory structures located in the upper nose.

Sense of Taste

The Tongue:Taste receptors located on the tongue, with different areas sensitive to different tastes.

Sense of Sight

The Eye:Study of the eye is called ophthalmology. The eye has various accessory organs and layers.

Eyebrows

Patches of hair located above the eyes that perform a protective role.

Eyelids

Protect the eyes and have four layers.

Conjunctiva

A thin mucous membrane that lines the inner surface of the eyelids.

Lacrimal Apparatus

Responsible for secretion, distribution, and drainage of tears.

Extrinsic Eye Muscles

Muscles that move the eyeball in its bony orbit.

Eyeball

Spherical shape, composed of three layers:sclera, choroid, and retina.

Sclera

Tough fibrous connective tissue that covers the outer surface of the eyeball.

Choroid

Middle layer of the eye that provides the retina with a rich supply of blood.

Retina

Innermost layer of the eyeball that contains photoreceptors (rods and cones).

Cavities and Fluids

Posterior and anterior cavities in the eyeball, filled with aqueous humor.

Muscles of the Eye

Extrinsic and intrinsic eye muscles that move the eyeball and structures within the eyeball.

Intrinsic Eye Muscles

Smooth muscles located in the eyeball, including the muscles of the iris and ciliary muscle.

Pathway of Light

The route that light waves take to enter the eye and focus on the retina.

Stimulation of Photoreceptors

The process of stimulating the rods and cones in the retina for vision.

Night Vision

Rods are more abundant in the periphery of the retina, allowing for better vision in low light conditions.

Color Vision

Cones are the photoreceptors responsible for color vision and are most abundant in the central portion of the retina.

Visual Pathway

Nerve impulses travel along optic nerves and optic tracts to the occipital lobe of the brain for visual processing.

Structure of the Ear

Divided into three parts:external, middle, and inner ear.

External Ear

Composed of the auricle and external auditory canal, allowing sound waves to enter the ear.

Middle Ear

Small air-filled chamber located between the tympanic membrane and the bony wall, containing the tympanic membrane, tiny bones, and the eustachian tube.

Inner Ear

Consists of the vestibule, semicircular canals, and cochlea. Responsible for hearing and equilibrium.

Sense of Balance

The Ear:The inner ear contains receptors for balance, located within the semicircular canals and vestibule.

Static Equilibrium

The ability to maintain a steady position of the head and body in gravity.

Dynamic Equilibrium

The ability to detect sudden movements of the head and maintain posture while moving or rotating.