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57 terms

Ch. 7: The Nervous System

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Nervous system - organization
CNS: brain, spinal cord
PNS: nerves
Somatic: conscious, voluntary
Autonomic: automatic, involuntary
Nervous system - functions
Sensory/afferent: impulses to CNS from receptors
Motor/efferent: impulses from CNS to effector organs
Central nervous system
Brain and spinal cord
Integrating and command centers
Interpret incoming sensory information and issue instructions
Peripheral nervous system
Nerves
Communication lines
Link all parts of the body by carrying impulses
Astrocytes
Star-shaped with swollen ends
Protect neurons from harmful substances in blood
Help control chemical environment in brain
CNS
Microglia
Spiderlike phagocytes
Dispose of debris and dead brain cells
CNS
Ependymal cells
Circulate cerebrospinal fluid
Protective cushion around CNS
Line cavities of brain and spinal cord
Oligodendrocytes
Flat extensions
Produce myelin sheaths
Wrap around nerve fibers
CNS
Schwann cells
Form myelin sheaths
PNS
Satellite cells
Protective, cushioning cells
PNS
Neurons
Cell body, nucleus, one or more processes
Transmit messages
White matter
Dense myelinated fibers
Gray matter
Unmyelinated fibers and cell bodies
Cerebrum
Most superior
Gyri: elevated ridges
Sulci: shallow groves
Fissures: deeper grooves
Cerebrum - parietal lobe
Somatic sensory area
Posterior to central sulcus
Interprets impulses from sensory recetpros
Recognize pain, coldness, touch
Cerebrum - occipital lobe
Visual
Cerebrum - temporal lobe
Auditory
Olfactory
Borders lateral sulcus
Cerebrum - frontal lobe
Primary motor area
Anterior to central sulcus
Conscious movement of skeletal muscles
Cerebrum - Broca's area
Speech
Base of precentral gyrus
Diencephalon
Interbrain
Sits atop brain stem, enclosed by cerebral hemispheres
Diencephalon - thalamus
Encloses third ventricle
Relay station for sensory impulses
Diencephalon - hypothalamus
Under thalamus
Regulates body temperature, water balance, metabolism
Center for drives and emotions
Pituitary gland: produces hormones
Mammilary bodies: reflex centers
Diencephalon - epithalamus
Roof of third ventricle
Pineal body
Choroid: forms CSF
Brain stem - midbrain
Mammillary bodies to pons inferiorly
Reflex centers for vision and hearing
Brain stem - pons
Rounded structure below midbrain
Mostly fiber tracts
Control of breathing
Brain stem - medulla oblongata
Most inferior of brain stem
Controls heart rate, blood pressure, breathing, swallowing, vomiting
Posterior to pons and medulla, anterior to cerebellum
Cerebellum
Dorsally from occipital lobe
Timing for skeletal muscle activity
Controls balance and equilibrium
Cerebrospinal fluid
Watery broth
Contains less protein, more vitamin C
Watery cushion protects nervous system from blows and trauma
Blood-brain barrier
Least permeable capillaries in body
Separates neurons from bloodborne substances
Useless against fats, respiratory gases, fat-soluble molecules
Meninges - dura mater
Tough mother
Outermost layer
Surrounds brain, attached to inner surface of skull
Meninges - arachnoid mater
Cobweb
Middle layer
Meninges - pia mater
Gentle mother
Innermost layer
Clings tightly to surface of brain and spinal cord
Reflexes - reflex arc
Sensory receptor reacts to stimulus
Effector organ eventually stimulated
Sensory and motor neurons connect the two
Integration center: synapse between sensory and motor neurons
Reflexes - somatic
Stimulate skeletal muscles
Pulling hand away from hot object
Reflexes - autonomic
Activity of smooth muscles, heart, glands
Digestion, elimination, blood pressure, sweating
Secretion of saliva, changes in size of eye pupil
I. Olfactory
Fibers arise from olfactory receptors in nasal mucosa and synapse with olfactory bulbs.
Carries impulses for sense of smell.
II. Optic
Fibers arise from retina of eye and form optic nerve. The two optic nerves from optic chiasma by partial crossover of fibers.
Carries impulses for vision.
III. Oculomotor
Fibers run from the midbrain to the eye.
Supplies motor fibers to four of the six muscles that direct the eyeball, to the eyelid, and to the internal eye muscles controlling lens shape and pupil size.
IV. Trochlear
Fibers run from the midbrain to the eye.
Supplies motor fibers for one external eye muscle.
V. Trigeminal
Fibers emerge from the pons and form three divisions that run to the face.
Conducts sensory impulses from the skin of the face and mucosa of the nose and mouth; also contains motor fibers that activate the chewing muscles.
VI. Abducens
Fibers leave the pons and run to the eye.
Supplies motor fibers to the lateral rectus muscle, which rolls the eye laterally.
VII. Facial
Fibers leave the pons and run to the face.
Activates the muscles of facial expression and the lacrimal and salivary glands; carries sensory impulses from the taste buds of anterior tongue.
VIII. Vestibulocochlear
Fibers run from the equilibrium and hearing receptors of the inner ear to the brain stem.
Vestibular branch transmits impulses for the sense of balance, and cochlear branch transmits impulses for the sense of hearing.
IX. Glossopharyngeal
Fibers emerge from the medulla and run to the throat.
Supplies motor fibers to the pharynx that promote swallowing and saliva production; carries sensory impulses from taste buds of the posterior tongue and from pressure receptors of the carotid artery.
X. Vagus
Fibers emerge from the medulla and descend into the thorax and abdominal cavity.
Fibers carry sensory impulses from and motor impulses to the pharynx, larynx, and the abdominal and thoracic viscera; most motor fibers are parasympathetic fibers that promote digestive activity and help regulate heart activity.
XI. Accessory
Fibers arise from the medulla and superior spinal cord and travel to muscles of the neck and back.
Mostly motor fibers that activate the sternocleidomastoid and trapezius muscles.
XII. Hypoglossal
Fibers run from the medulla to the tongue.
Motor fibers control tongue movements; sensory fibers carry impulses from the tongue.
Spinal nerve plexuses - cervical
C1-C5
Phrenic: diaphragm and muscles of shoulder and neck
Spinal nerve plexuses - brachial
C5-C8 and T1
Axillary: deltoid muscle of shoulder
Radial: triceps and extensor muscles of forearm
Medial: flexor muscles of forearm and some muscles of hand
Spinal nerve plexuses - lumbar
L1-L4
Femoral: lower abdomen, buttocks, anterior thighs, skin of anteromedial leg and thigh
Obturator: adductor muscles of medial thigh and small hip muscles, skin of medial thigh and hip joint
Spinal nerve plexuses - sacral
L4-L5 and S1-S4
Sciatic: lower trunk and posterior surface of thigh
Common fibular: lateral aspect of leg and foot
Tibial: posterior aspect of leg and foot
Superior and inferior gluteal: gluteus muscles of hip
Tract
Collection of nerve fibers in CNS having the same origin, termination, and function
Nucleus
Dense central body in most cells containing genetic material of cell
Ganglion
Group of nerve cell bodies located in PNS
Nerve
Bundle of neuronal processes (axons) outside CNS
ANS - sympathetic
Fight-or-flight
Pounding heart, rapid breathing, cold skin, prickly scalp, dilated eye pupils
Increase heart rate, blood pressure, blood glucose levels
ANS - parasympathetic
Resting-and-digesting
Housekeeping
Normal digestion, elimination of feces and urine, conserving body energy