chapter 12 the nervous system
TRANSCRIPT
CHAPTER 12: A GLANCE AT THE
NERVOUS SYSTEM
By Shawna Miller
FUNCTIONS AND ORGANS The functions of the nervous system are
to coordinate and control body functions.Receives sensory outputMakes decisionsOrders body responses
The organs of the nervous system are:BrainNervesSpinal cord
NERVOUS TISSUE Consists of two cell types
Neurons- individual nerve cells Dendrite- branched projections, receive impulses Nerve cell body- contains nucleus/other organelles Axon-projection from the nerve cell body, conducts
electrical impulses to destination The point which the axon of one neuron meets the
dendrite of another neuron is called a synapse. The gap between two neurons is called a synaptic cleft. The electrical impulses need help from chemical
messengers caller neurotransmitters. Different neuroglial cells are in nervous tissue
Some produce myelin-a fatty substance which acts like insulation for axons
They do not conduct electrical impulses
CENTRAL NERVOUS SYSTEMReceives impulses from all over the body.The system is made of grey and white matter.Grey matter is uncovered cell bodies and dendrites.White matter is myelinated nerve fibers.The myelin sheath makes the nervous tissue look white.Tracts are bundles of nerve fibers that connect parts of the CNS.Meninges are what the CNS is encased and protected by. There are three of these membranes.
THE BRAIN One of the largest organs in the body.
Center for thought, judgement, memory, and emotion.
Four sections: Cerebrum- largest section in the upper part of the brain. It processes problem solving, language,
thoughts, and memory. It has an outer layer called the cerebral cortex which is made up of folds of grey matter.
Diencephalon- below the cerebrum contains the thalmus and hypothalmus Thalmus- center for relaying impulses for eyes, ears, and skin to the cerebrum. What our pain
perception is controlled by.
Hypothalmus- below thalmus, controls body temperature, sleep appetite, and emotions.
Cerebellum- second largest section, beneath the posterior part of the cerebrum. Helps to maintain body movements and maintain balance.
Brain stem : has three parts Mid brain- acts as pathway between brain and spinal cord
Pons- connects the cerebellum to rest of brain
Medulla oblongata- most inferior portion of the brain; it connects the brain to the spinal cord
A vital are that controls respiration, heart rate, and blood pressure
Site where nerve tracts cross
The brain has four interconnected cavities called ventricles. There is one in each hemisphere of the brain
They contain CSF(cerebral spinal fluid) that protects the brain from shock/sudden movement to brain and spinal cord
A VIEW OF THE BRAIN
SPINAL CORD The spinal cord’s function is to
provide a pathway for impulses traveling to and from the brain
A column of nervous tissue that goes from the medulla oblongata down to the second level of the lumbar vertebra in the vertebral column
Goes down to the center of the spinal cord in the central canal
Outer portion is myelinated white matter- can be either ascending tracts(carrying sensory info to the brain) or descending tracts( carrying motor commands from the brain to a peripheral nerve
MENINGES Three layers of connective
tissue membranes that surround the brain and spinal cord
External to internal: Dura mater(tough mother)- tough
fibrous sac around the CNS Subdural space- actual space
between the dura mater and arachnoid layers
Arachnoid layer(spiderlike)- thin, delicate layer attached to the pia mater by weblike filaments
Subarachnoid space- space between the arachnoid and pia mater layers. It contains cerebrospinal fluid which cushions the brain from the outside
Pia mater(soft mother)- innermost membrane layer which is applied directly to the spinal cord and surface of the brain
PERIPHERAL NERVOUS SYSTEM Includes 12 pairs of cranial nerves and 31 pairs of spinal
nerves Where the nerve originates determines if it is cranial or
spinal The point where either type is attached to the CNS is called
the nerve root Afferent neurons(sensory neurons)- carry sensory info
from a sensory receptor to the CNS Efferent neurons(motor neurons)- carry activity
instructions from the CNS to muscles/glands out in the body Nerves of the peripheral nervous system are subdivided
into two areas: the autonomic nervous system(ANS) and somatic nerves which each serve a different part of the body
The nerve cell bodies of the neurons are grouped together in a knot-like mass, called a ganglion
AUTONOMIC NERVOUS SYSTEM
Involved with control of involuntary or unconscious bodily functions
May increase or decrease activity of smooth muscles
Is divided into two divisions Sympathetic branch- control the
“fight or flight” reaction during stress or crisis. These nerves increase heart rate, dilate airways, increase blood pressure, inhibit digestion, and stimulate adrenaline production
Parasympathetic- counterbalance for sympathetic, the “rest and digest” reaction. They lower heart rate, decrease blood pressure, and stimulate digestion
Somatic nerves- serve the skin and skeletal muscles. Mainly involved with the conscious/voluntary activities of the body. Largest ones found in dermis of skin like touch, pressure and pain. Also carry motor commands to skeletal muscles
COMMON TERMSCerebrospinal, meningitis, analgesia, aphasia, dysphasia, quadriplegia, neuropathy, encephalitis, electroencephalogram
DEFINITIONS Cerebrospinal- pertaining to the
cerebrum and spine Meningitis- meninges inflammation Analgesia- absence of pain or
sensation Aphasia- lack of speech Dysphagia- difficult speech Quadriplegia- paralysis of four Neuropathy- nerve disease Electroencephalogram(EEG)- record
of brain’s activity
TESTS Brain scan-image of the
brain taken after an injection of radioactive isotopes into the circulation
Echoencephalography- record of the ultrasonic echoes of the brain
Myelography- injection of radiopaque dye into the spinal cord
Positron emission tomography- use of positive radionuclides to reconstruct brain sections
TREATMENTSNerve block- injection of regional anesthetic to stop the passage of sensory/pain impulses along a nerve pathLaminectomy- removal of a portion of a vertebra in order to relieve pressure on the spinal nerveTractotomy- surgical interruption of a nerve tract in the spinal cord
MEDICATIONS
Analgesics- non narcotics to treat pain(aspirin, tylenol, aleve, ibuprofen)
Anesthetics- drug that produces a loss of sensation or loss of consciousness( propofol, novocain, lidocaine, nembutal)
Hypnotic- drug that promotes sleep(restoril, seconal, temazepam)
Sedative- drug that has a relaxing or calming effect(amytal, butisol, amobarbital)