Study Guide Chpt. 7 Jenna Kozlowski
Terms in this set (70)
What is the nervous system?
The nervous system is the master controling and communicating system of the body.
What are the three overlapping functions of the nervous system?
1. It uses its millions of sensory receptors to monitor changes occurring both inside and outside the body (changes are called stimuli and the gathered info is called sensory input)
2. It processes and interprets the sensory input and decides what should be done at each moment (called integration)
3. It then effects, or causes, a response by activating muscles or glands (effectors) via motor output
How is the nervous system organized?
There are structural and functional classifications
What are the two divisions of the structural calssification?
Central nervous system (CNS) and the peripheral nervous system (PNS)
What makes the cnetral nervous sustem different fromt he peripheral nervous system?
The CNS consists of the brain and spinal cord, and act as the integrating and command centers of the nervous system; the PNS is part of the nervous system outside the CNS; the PNS consists of spinal nerves, which carry impulses to and from the spinal cord and cranial nerves which carry impulses to and from the brain
What are the subdivisions of the functional classification?
Concerns only the PNS:
-The sensory (Afferent) division consists of nerves that convey impulses to the CNS from sensory receptors located in various parts of the body; somatic sensory fibers deliver impulses from the skin, skeletal muscles, and joints; visceral sensory fibers transmits impulses from the visceral organs
-the motor (efferent) division carries impulses from the CNS to efferent organs, the muscles, and glands
How are the sensory and motor divisions different?
The sensory division consists of nerves that convey impulses to the CNS from sensory receptors located in various parts of the body and the motor division carries impulses from the CNS to efferent organs, the muscles, and glands
What are the two subdivisions of the motor division?
-the somatic nervous system: allows us to voluntarily control our skeletal muscles
-the autonomic nervous system: regulates the events that are involuntary, such as the activity of smooth and cardiac muscles and glands. There are two parts, the sympathetic and parasympathetic
What is neuroglia?
They are supporting cells of the CNS; they support, insulate, and protect the delicate neurons
Name and define the supporting cells of the nervous system.
-astrocytes: abundant star cells that account for nearly half of the neural tissue
-microglia: spiderlike phagocytes that monitor the health of nearby neurons, and dispose of debris
-ependymal cells: glial cells that line the central cavities of the brain and the spinal cord
-oligodendrocytes: gila cells that wrap their flat extensions (processes) tightly around the nerve fibers, producing fatty insulating coverings called myelin sheath
What are schwann cells?
A Schwann cell is a supporting cell for the PNS
What do Schwann cells form?
The form the myelin sheaths around nerve fibers
Describe the structure of a neuron.
Neurons are highly specialized to transmit messages from one part of the body to another; cell body is the metabolic center of the neuron, its rough ER are called nissl bodies and neurofibrils are abundant; neuron processes that convey incoming messages toward the cell are dendrites while those that generate nerve impulses away from the cell body are axons; neurons may have hundreds of dendrites, but it will have only one axon arising from a conelike region called the axon hillock; at the end of the axon, thousAnds of axon terminals are found
What are myelin sheaths?
Most long nerve fibers are covered with a whitish, fatty material called myelin, which has a waxy appearance; myelin protects and insulates the fibers and increases the transmission rate of nerve impulses; the schwann cells create the myelin sheath
What is the neurilemma?
The part of the schwann cell that is external to the myelin sheath
How are nuclei different from ganglia?
When in the CNS, clusters of cell bodies are known as nuclei while in the PNS small collections of cell bodies are called ganglia
What is the difference between tracts and nerves?
Bundles of nerve fibers running through the CNS are called tracts, while in the PNS they are called nerves
What is the difference between white and gray matter?
White matter consists of dense collection of myelinated fibers, and gray matter contains mostly unmyelinated fibers and cell bodies
Describe the functional classification of nerves.
Functional classification groups neurons according to the direction the nerve impulse is traveling relative to the CNS
What are the three types of nerves?
Sensory (afferent) neurons carry impulses from sensory receptors to the CNS, cell bodies are always found in a ganglion
Dendrites are endings of the sensory neurons are usually associated with specialized receptors that are activated by specific changes occurring nearby
Cutaneous sense organs are sensory receptors in the skin
Proprioceptors are found in muscle and tendons and detect the amount of stretch in skeletal muscles, tendons and joints
Pain receptors are actually bare nerve endings and are the most numerous, but least specialized
Neurons carrying impulses from the CNS to the viscera and muscles and glands are motor (Efferent) neurons, their cell bodies are always located in the CNS
Interneurons (associated neurons) connect motor and sensory neurons in neural pathways, their cell bodies are alway located int he CNS
What are the 3 structural classification of nerves?
1. Multipolar neuron
2. Bipolar neuron
3. Unipolar neuron
Explain how the processes extend fromt he cell body in each of the structural classification.
1. multipolar: several processes coming from the cell body, most common type
2. Bipolar: one dendrite and one axon, rare in adults, found in special sense organs (eye, nose)
3. Unipolar: a single process emerging from the cell body, found in PNS ganglia
Explain how an electrical impulse travels along a nerve.
the plasma memnrane of a resting neuron is polarized, which means that there are fewer positive ions sitting on the inner face of the neuron's plasma membrane than on the outer face. The neuron is stimulated in some way causing the permeability properties of the cell's plasma membrane to change for a very brief period. Depolarization of the neuron's membrane occurs when sodium ions rich into the cell. The inside its now more positive, and the outside is less positive, creating an electrical situation called a graded potential. Nerve impulse is an all or none response; it is either send over the entire axon, or not at all. Repolarization occurs when the sodium ions are once again blocked and potassium ions are allowed to diffuse out of the neuron into the tissue fluid
What is a reflex?
Reflexes are rapid, predictable, and involuntary responses to stimuli. Once a reflex begins, it always goes in the same direction
How do somatic and autonomic reflexes differ?
Somatic reflexes include all reflexes that stimulate the skeletal muscles; autonomic reflexes regulate the activity of smooth muscles, the heart, and glands
Describe the parts of the brain.
There are 4 major regions the cerebral hemispheres, diencephalon, brain stem, and cerebellum
What is a gyri?
The entire surface of the cerebral hemispheres exhibit elevated ridges of tissue called gyri, separate by shallow grooves called sulci
What is the difference between sulci and fissures?
Sulci separate elevate ridges of tissue called gyri; fissures separate large regions of the brain; most gyri and fissures are anatomical landmarks
How is the cerebrum divided into sections?
The cerebral hemispheres are separated by a single deep fissure, the longitudinal fissure; each cerebral hemisphere has three basic regions:
1. A superficial cortex of gray matter
2. An internal area of white matter
3. The basal nuclei, islands of gray matter situated deep within the white matter
How are the lobes of the cerebrum named?
Other fissures divide the cerebral hemisphere into lobes, named for the cranial bones that lie over them
What is the corpus callosum?
It sonnets the cerebral hemispheres
Describe the purpose of the diencephalon.
The diencephalon, also known as the interbrain, sits atop the brain stem and is enclosed by the cerebral hemispheres
What are the major structures of the diencephalon?
Thalamus, hypothalamus, and epithalamus
What are the structures of the brain stem?
Midbrain, pons, and medulla oblongata
Explain the funtions of the structures of the brain stem.
The midbrain has four rounded protrusions called the coropora quadrigemina, which are reflex centers involved with vision and hearing. The pons is the rounded structure that protrudes just below the midbrain. It is mostly fiber tracts, but it does help control breathing. The medulla oblongata is the most inferior part of the brain stem. It merges with the spinal cord. The medulla contains many centers that control heart rate, blood pressure, breathing, swallowing, and vomiting.
Where is the cerebellum?
Projects dorsally from under the occipital lobe of the cerebrum
What is the function of the cerebellum?
It provides the precise timing for skeletal muscle activity and controls our balance and equilibrium; body movements are smooth and controlled because of the cerebellum
What protects the CNS?
The brain and spinal cord are protected by being enclosed by bone, membranes and a watery cushion. The blood brain barrier protects the brain from harmful substances in the blood
What are the 3 types of meninges?
Dura mater, arachnoid mater, and pia mater
Desribe where each meninges is found.
The dura mater is the outer most layer and is a leathery, double-layered membrane; one side is attached to the skull forming the periosteum; the other forms the outer most covering of the brain and continues as the dura mater of the spinal cord; the middle layer is the weblike arachnoid mater; the arachnoid mater thread like extensions spans the subarachnoid space and attach it to the inner most pia mater; the pia mater clings tightly to the surface of the brain and spinal cord
What is meningitis?
It is an inflammation of the meninges
What is encephalitis?
It is an inflammation of the brain
Describe cerebrospinal fluid.
Is a watery "broth" similar in make up to blood plasma; it is formed continually formed from blood; is in and around the brain and spinal cord to form a watery cushion that protects the fragile nervous tissue from blows and other trauma
What is hydrocephalus?
If CFS begins to accumulate and exert pressure on the brain hydrocephalus occurs
Describe the blood-brain barrier. What is its function?
It is composed of the least permeable capillaries in the body; only water, glucose and essential amino acids pass easily through the walls of these capillaries; the blood-brain barrie is useless against fats, respiratory gases and other soluble membranes; this is why alcohol, nicotine, and anesthetics can affect the brain
What is the difference between concussion and contusions?
A concussion occurs when the brain injury is slight; no permanent brain damage occurs; a brain contusion is the result of marked tissue destruction
Waht is a cerebrovascular accident (CVA)?
Are the 3rd leading cause of death in the united states; occur when blood and circulation to a brain area is blocked , and vital brain tissue dies
What is the common name for a CVA?
Hoe does a transient ischemic attack (TIA) differ from a CVA?
CVAs are strokes and TIAs are incomplete strokes; TIAs last from 5 to 50 minutes and are characterized by symptoms such as numbness, temporary paralysis and impaired speech
Where does the spinal cord begin and end?
The spinal cord extends from the foramen magnum of the skill to the skull to the first or second lumbar vertebra
How many spinal nerves arise from the spinal cord?
What is the cauda equina?
The collection of spinal nerves at the inferior end of the vertebral canal
Explain the gray matter of the spinal cord. What does it look like?
The gray matter of the spinal cord looks like a butterfly or the letter H; the posterior projections are the dorsal (posterior) horns' the two anterior projections are the ventral (anterior) horns; the gray matter surrounds the central canal of the cord which contains CSF; neurons with specific functions can be located in the gray matter; dorsal horns contain interneurons; ventral. Horns contain cell bodies of motor neurons of the somatic nervous system; dorsal and ventral roots fuse to form the spinal nerves
How is the hwite matter of the spinal cord divided?
Into three regions- the dorsal, lateral, and vertebral columns; all tracts in the dorsal column are ascending tracts that carry sensory input to the brain; the lateral and ventral tracts contain both ascending and descending (motor) tracts
Describe the PNS
The peripheral nervous system (PNS) consists of nerves and scattered groups of neuronal cell bodies (ganglia) found outside the CNS.
Explain the layering of a nerve from inner to outer covering.
Each fiber is surrounded by a connective tissue sheath, an endoneurium. Groups of fibers are bound by a coarser connective tissue wrapping, the perineurium, to form fiber bundles, or fascicles. All the fascicles are bound together by a tough fibrous sheath, the epineurium, to form the cordlike nerve.
What are mixed nerves?
Mixed nerves carry both sensory and motor fibers; all spinal nerves are mixed nerves.
How many cranial nerves do humans have?
How are cranial nerves numbered and named?
Cranial nerves are numbered in order, and their names reveal the most important structures they control
How are spinal nerves named?
Spinal nerves are named for the regions of the spinal cord from which they arise
What are dorsal and ventral rami?
Each spinal nerve divides into dorsal and ventral rami, making each nerve only about half an inch long/ the rami contain contain both motor and sensory fibers. The dorsal rami serve the skin and muscles of the posterior body trunk. The ventral rami of spinal nerves form complex networks of nerves called plexuses, which serve the motor and sensory needs of the limbs.
What is a plexus?
The ventral rami of spinal nerves form complex networks of nerves called plexuses, which serve the motor and sensory needs of the limbs.
Describe the autonomic nervous system.
The autonomic nervous system (ANS) is the motor subdivision of the PNS that controls body activities automatically. The ANS is composed of a specialized group of neurons that regulate the cardiac muscle, smooth muscles, and gland.
What are the two divisions of the ANS?
The autonomic nervous system has two branches, the sympathetic and parasympathetic.
Which division is responsible for the "fight or flight" response?
What is the neurotransmitter parasympathetic fibers release?
Parasympathetic fibers, called cholinergic fibers, release Acetylcholine
What is the neurotransmitter the sympathetic fibers release?
Sympathetic fibers, called adrenergic fibers, release norepinephrine
When is the parasympathetic nervous system most active?
It is most active when he body is at rest and not threatened in any way
What functions does the parasympathetic regulate?
It is concerned with promoting normal digestion, conserving body energy, and decreasing demands on the cardiovascular system
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