Nervous System Flashcards
Afferent
Carry or move inward or toward a central structure
Blood-brain barrier
Protective mechanism that blocks specific substances found in the bloodstream from entering delicate brain tissue
Efferent
Carry or move away from a central structure
Limbic system
Complex neural system located beneath the cerebrum that’s controls basic emotion s and drives and plays an important role in memory
Neurilemma
Additional external myelin sheath that is formed by schwann cells and found only on axons in the peripheral nervous system.
Ventricle
Organ chamber or cavity that receives or holds fluids
Neurons
One of the two principal cell types that composed the nervous system
Along with neuroglia constitute the tissue of the body
Transmit impulses
Identified by the direction impulses travel, afferent— toward and efferent— away from the brain or spinal cord
3 major structures of the neuron are
1. Cell body, 2. Axon, 3. Dendrites
Cell body
Is the enlarged structure of the neuron that contains the nucleus of the cell and various organelles
Dendrites
Branching cytoplasm projection
Carry impulses to the cell body
Resemble tiny branches on a tree, providing additional surface area for receiving impulses from other neurons
Axons
Carry impulses from the cell body
Are threadlike extensions of nerve cells that transmit impulses to dendrites or other neurons as well as muscles and glands
Posses a white, lipoid covering myelin sheath
Myelin sheath
A white lipoid covering in the axons of the neuron.
Covering acts as an electrical insulator that reduces the possibility of an impulse stimulating adjacent nerves
Also accelerates impulse transmission through the axon
Schwann cell
A Neuroglial cell that forms the myelin sheath in the peripheral nervous system that wraps tightly around the axon.
Neurilemma
Neurolemma
The exterior surface of the Schwann cell forms a thin tube called neurilemma
Does not disintegrate after an axon has been crushed or severed (remains intact)
Intact sheath provides a pathway for possible neuron regeneration after injury
Nodes of ranvier
Short, unmyelinated spaces between adjacent segments of the myelin sheath
Help speed the transmission of impulses down the axon because an impulse jumps across the nodes at a faster rate than it’s able to travel through the myelinated axon.
Synapse
Functional connection between two neurons or between a neuron and it’s effector organ (muscle or gland) is a gap space called a synapse l
Neuroglia
One of the two principal cell types that composed the nervous system
Along with neurons constitute the tissue of the body
Cells that support neurons and bind them to other neurons or other tissues of the body
Don’t transmit impulses but provide a variety of activities essential to the proper functioning of neurons
Neuroglia means nerve glue
They supply nutrients and oxygen to neurons and assist in other metabolic activities
Four major types of neuroglia are
1.astrocytes, 2. Oligodendrocytes, 3. Microglia, 4. Ependyma
Astrocytes
Are star-shaped neuroglia
Provide three-dimensional mechanical support for neurons and form right sheaths around a the capillaries of the brain
Perform mildly phagocytic functions in the brain and spinal cord
Oligodendrocytes
Also called oligodendroglia
Responsible for developing myelin on axons of neurons in the central nervous system
Microglia
Smallest of the neuroglia
Possess phagocytic properties and may become very active during times of infection
Ependyma
Ciliates cells that line fluid-filled cavities of the central nervous system especially the ventricles of the brain
Assist in the circulation of cerebrospinal fluid (CSF)
Central nervous system (CNS)
Major division part of the nervous system
Consists of the brain and spinal cord
It’s nervous tissue is classified as white matter or gray matter
Bundles of axons with their white lipoid myelin sheath constitute white matter
Unmyelinated fibers, dendrites, and nerve cell bodies make up the gray matter of the brain and spinal cord
Peripheral nervous system (PNS)
Major division part of the nervous system
Consists of 12 pairs of cranial nerves and. 31 pairs of spinal Nerves
Composed of all nervous tissue located outside the spinal column and skull
Cerebrum
The largest uppermost portion of the brain
Consists of two hemispheres divided by a deep longitudinal fissure, or grove
Corpus callosum
Joins the hemispheres of the cerebrum permitting communication between the right and left sides of the brain
Major functions include: sensory perception and interpretation, language, voluntary movement, and memory
Limbic system
Located beneath the cerebrum also known as an emotional brain
Is essential for survival and works in conjunction with the thinking brains
Controls such behaviors as rage, fear, and anger and the emotional aspects such as food enjoyment and sexual behavior
Cerebellum
The second largest structure of the brain
Occupies the posterior portion of the skull
Most functions involve movement, posture, or balance
Cerebrum initiates muscular movement while the cerebellum coordinates and refined it
Diencephalon
Also called interbrain
Composed of many smaller structures including the thalamus and hypothalamus
Thalamus receives all sensory stimuli except olfactory and processes and transmits them to the appropriate centers in the cerebral cortex
Hypothalamus regulates involuntary activities such as heart rate, body temperature, and fluid balance. Also controls many endocrine functions
Brainstem
Completes the last major section of the brain
Composed of three structures:
1.midbrain: called mesencephalon which separated the cerebrum from the brainstem
- medulla: attaches to the spinal cord
- Pons: “bridge”; connects the midbrain to the medulla
Brainstem is a pathway for impulse conduction between the brain and spinal cord. Also is the Origin of 10 of the 12 pairs of cranial nerves and control respiration, blood pressure, and heart rate
Is the site that controls the beginning and end of life.
Spinal cord
Transmits sensory impulses from the body to the brain and motor impulses from the brain to muscles and organs of the body.
Meninges
The brain and spinal cord receive limited protection from three coverings called meninges which are dura mater, arachnoid, and pia mater
Beneath the dura mater is a cavity called the subdural space which is filled with serous fluid
Dura mater
The outermost covering of the brain and spinal cord.
It’s rough, fibrous, and dense and composed primarily of connective tissue
Because of its thickness this membrane is also called pachymeninges
Arachnoid
The middle covering and has a spider-web appearance
Fits loosely over the underlying structures
Called the leptomeninges
Cerebrospinal fluid
A colorless fluid that contains proteins, glucose, urea, salts, and some white blood cells
Circulated around the spinal cord and brain and through ventricles located within the inner portion of the brain
Hydrocephalus
A collection of cerebrospinal fluid in the brain caused by an interference in the absorption of the fluid
Pia mater
The innermost meninges
Directly attached to the brain and spinal cord
Contains numerous blood vessels and lymphatics that nourish the underlying tissues
Called the leptomeninges
Cranial nerves
Originate in the base of the brain and emerge through openings in the base of the skull
May be sensory, motor, or a mixture of both
Sensory nerves
Are afferent
Receive impulses from the sense organs, including eyes, ears, nose, tongue, and skin and transmit them to the CN
Motor Nerves
Are efferent
Conduct impulses to muscles and glands
Mixed nerves
Composed of sensory and motor fibers
Example: facial nerve
Acts in a motor capacity by transmitting impulses for smiling or frowning.
Acts in a sensory capacity by transmitting taste impulses from the tongue to the brain
Spinal nerves
Emerge from the intervertebral spaces in the spinal column and extend to various locations of the body
All 31 pairs of spinal nerves are mixed nerves
Anterior root contains motor fibers
Posterior root contains sensory fibers
Both roots untied to form the spinal nerve that has afferent and efferent qualities
Somatic & autonomic nervous systems
Somatic- motor impulses transmitted to muscles under conscious control (walking and talking)
Autonomic- motor impulses transmitted to glands and muscles not under conscious control (heart rate, respiration, digestion, pupil diameter, and so forth)
