CNS
consists of brain and spinal cord - processes incoming sensory information and is the source of thoughts, emotions and memories - nerve impulses that stimulate muscles to contract and glands to secrete originate in this system
types of nervous tissue
neurons and neuroglia
neurons
processes electrical excitability: ability to respond to a stimulus and convert it into an action potential
parts of neuron
cell body, dendrites, and an axon
cell body
soma- contains single nucleus surrounded by cytoplasm- contains typical organelles (rough ER called nissl bodies)
dendrites
multiple processes extending from cell body that receive impulses/info from another neuron or sensory receptor
axon
single extension from cell body that propagates an impulse away from cell body toward another neuron, muscle fiber of gland cell
structural classification of neurons
according to the number of processes extending from the cell body
multiple neurons
have several dendrites and one axon - most neurons in brain and spinal cord are this type
bipolar neurons
have one main dendrite and one axon - found in retina, inner ear and olfactory area of the brain
unipolar neurons
have dendrites and one axon that fuse together to form a continuous process that emerges from cell body - dendrites function as sensory receptors that detect sensory stimuli such as touch pressure, pain or temp. - cell bodies are located in the ganglia or
functional classification of neurons
according to the direction in which the nerve impulse is conveyed with respect to the CNS
sensory
afferent neurons - contain sensory receptors at their distal ends - once stimulus activates a sensory receptor, the sensory neuron forms an action potential which is conveyed into the CNS through cranial or spinal nerves - most unipolar
motor neurons
efferent neurons - convey action potential away from the CNS to effectors (nucleus and glands) in the periphery through cranial or spinal nerves - most are multipolar
interneurons
association neurons - located within the CNS between sensory and motor neurons - processing incoming sensory info from sensory neurons and elicit a motor response by activating appropriate motor neurons - most are multipolar
neuroglia
support, nurture and protect neurons and maintain the interstitial fluid that bathes them - make up half the volume of the CNS - smaller than neurons but 5-50 times more numerous - do not generate or propagate action potentials - can multiply and divide i
neuroglia of the CNS
classified on the basis of size, cytoplasmic processes and intracellular organization inot 4 types: astrocytes, oligodendrocytes, microglia, ependymal cells
brain
conisists of 4 major parts: brain stem, cerebellum, diencephalon, cerebrum
brain stem
continuous with the spinal cord and consists of the medulla oblongta, pons, and midbrain
cerebellum
posterior to the brain stem
diencephalon
superior to the brain stem and consists of thalamus, hypothalamus and epithalamus
cerebrum
largest part of the brain
protective covering of the brain
the cranium (skull) and the meninges surround and protect the brain
cranial meninges
the outer dura mater - the middle arachnoid mater - the inner pia mater
cerebrospinal fluid
contributes to homeostasis in 3 main ways: mechanical protection (shock-absorbing) - chemical protection (optimal environment) - circulation (allows exchange of nutrients and wastes between blood and nervous tissue
flow of CSF
flows through the lateral ventricles -into 3rd ventricle where more CSF is added - flows through the aqueduct of the midbrain into 4th ventricle where more CSF is added - enters the subarachnoid space - then into the central canal of the spinal cord - gra
medulla oblongata
forms inferior part of brain stem - contains all sensory tracts and motor tracts that extend between the spinal cord and other parts of the brain - contains several nuclei which control vital body functions: heartbeat, blood vessel diameter, normal breath
pons
consists of nuceli, sensory and motor tracts - contains nuclei that relay nerve impulses from cerebral cortex to cerebellum, vestibular nuclei for equilibrium; nuclei that help control breathing; nuclei of origin for cranial nerves 5-8
midbrain
contains 4 rounded elevations called colliculi
superior colliculi
coordinates movement of head, eyes and trunk in response to visual stimuli
inferior colliculi
coordinates movement of head, eyes and trunk in response to auditary stimuli
functions of cerebellum
evaluate how well movements instiated by motor areas in the cerebrum are actually being carried out : corrects errors from cerebral cortex to smooth and coordinates contractions of skeletal muscles - regulates posture and balance - non-motor functions suc
thalamus
contributes to motor functions by transmitting info from the cerebellum to the primary motor area of the cerebral cortex
intermediale mass
gray matter that joints left and right halves of hte thalmaus - there are 7 groups of nuclei on each side of thalamus
functions of hypthalamus
control of the ANS, production of hormones, regulation of emotional and behavioral pattern, regulation of eating and drinking, control of body temp, regulation of ciricadian rhythms and state of consciousness
epithalamus
superior and psoterior ot the thalamus - consists of pineal gland and habenular nuclei
cerebral cortex
regions of gray matter that forms an outer rim of the cerebrum
fissures
deepest grooves between gyri
longitudinal fissure
seperates cerebrum into right and left halves
corpus callosum
white matter that connects the 2 hemispheres
cerebral white matter
consists of myelinated axons in 3 types of tracts: assoication tracts, commissural tracts, projection tracts
functions of basal ganglia
helps initiate and terminate movements of the body - supports unwanted movement and regulate muscle tone
spinal cord
continuous with the brain and together at brain stem, make up CNS. external anatomy consists of 2 enlargements: cervical and lumbar enlargements
cervicle enlargement
where nerves exit for the upper limbs
lumbar enlargement
wherer nerves exit for the lower extremity
conus medullaris
where the spinal cord beings to taper; from the 12th thoracic vertebrae and 2nd lumbar vertebrae
spinal nerves
31 pairs - named for the vertebral segment that they exit
internal anatomy of spinal cord
regions of white matter that surround an inner core of gray matter
gray matter
shaped like a butterfly and consists of dendrites, cell bodies of neurons, unmyelinated axons and neuroglia
horns
gray matter divided into sub-categories
posterior gray horns
contain interneurosn (between motor and sensory neurons)
anterior gray horns
somatic motor nuclei
lateral gray horns
autonomic motor nuclei
white matter
consists of bundle of myelinated axons of neurons