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128 Cards in this Set
- Front
- Back
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What are the functions of the Nervous System?
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communication and homeostasis (sensation, integration, reaction)
-made up of the CNS (brain and spinal cord) and the PNS (Nerves-cranial and spinal) and (Ganglia- sensory and autonomic) |
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What are the divisions of the PNS?
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a. Sensory division
1. visceral sensory division 2. somatic sensory division b. Motor division 1. visceral motor division i. sympathetic division ii. parasympathetic division 2. somatic motor division |
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Viscerosensory
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sensation from internal organs (nausea)
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Somatosensory
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sensation from the surface/skin
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visceromotor
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motor to cardiac muscle, smooth muscle and gland
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somatomotor
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motor to skeletal muscle
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What are some characteristics of a neuron?
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-each neuron is capable of performing the basic functions of the nervous system (sensation, integration, reaction)
-excitability- respond to stimuli (mechanical, chemical, electrical) -conductivity- quickly transmit electrical signals over long distances -secretion- releases a neurotransmitter to affect another cell |
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Where do most neuron cell bodies lie?
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Most are in the CNS
-this is where interneurons are located and all motor/efferent neurons conduct signals from CNS to effectors such as muscles |
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What are the two types of neurons located in the PNS?
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-sensory and autonomic (visceromotor)- neurons that signal from effector to CNS
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What are nissl bodies?
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concentrations of rough endoplasmic reticulum responsible for making proteins of cell
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What are neurofibrils?
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bundles of actin filament that support the cell
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What are the different types of axon segments?
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-initial segment-most sensitive to changes in membrane potential, first to depolarize in action potential
-axon collaterals- branches that allow one neuron to communicate with many -axon terminal- where axons terminate on their targets(muscles, glands..) |
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What is the resting potential? What ion is on the outside of the cell?
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The resting potential is when there is more Na+ on the outside of the cell and the cell is negative, before an action potential
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What is depolarization?
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when neuron stimulated and channels open allowing Na+ to flow in and decrease the polarity across the membrane, if depolarized beyond a threshold level an action potential will pass down the entire length of the axon
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What is repolarization?
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after a fixed amount of time the Na+ channels close, and Na+ exits the cell to reestablish the polarity
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What are the different types of neurons?
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multipolar- many dendrites, most common type, many functions
bipolar-one dendrite, rare, special senses unipolar-one process is both the axon and the dendrite, general sensory neurons in DRG |
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What are the glial and supporting cells of the CNS?
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-astrocytes
-ependymal cells -microglia -oligodendrocytes |
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What are astrocytes?
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take up ions from extracellular fluid, surround blood vessels and form scar tissue when neurons are injured
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What are ependymal cells?
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line the ventricles (fluid filled spaces in the brain) and produce CSF
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What are oligodendrocytes?
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myelinate axons in the CNS
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what are microglia?
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macrophages of the CNS
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What are the glial and supporting cells of the PNS?
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-schwann cells
-satellite cells |
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What are Schwann cells?
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-surround all axons in the PNS, myelinate the largest axons in the PNS
-each Schwann cell myelinates part of a single axon, it takes many cells to cover the entire axon, there are gaps between the adjacent Schwann cells(these gaps called Nodes of Ranvier) -axons larger than a certain diameter are myelinated, the thicker the axon, the thicker the myelin and the faster the action potential Unmyelinated axons in the PNS are protected by Schwann cells, a single Schwann cell surrounds many axons, these axons have ion channels and depolarize along the entire length of their membrane |
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What are Nodes of Ranvier?
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they are gaps between the myelination on the axon where the action potential jumps from one to the next
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What are satellite cells?
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surround cell bodies in the PNS, separate cell bodies from the surrounding tissue, found in ganglia
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What happens at chemical synapses?
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a. action potential reaches terminal
b. Ca++ enters the axon terminal c. synaptic vesicles exocytose neurotransmitter d. neurotransmitter crosses synaptic cleft and binds to receptors |
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What is divergent?
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one neuron branches/diverges to synapse on many neurons, this amplifies the message
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What is convergent?
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many neurons converge on a single neuron this can increase the sensitivity but decrease the ability to localize
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What are the major functions of the Spinal Cord?
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a. conduction- carries info in ascending and descending pathways
b. locomotion- coordinates repetitive motions like walking c. reflexes- mediates quick reactions to stimuli via a simple loop of afferent and efferent fibers |
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Where does the spinal cord end?
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It ends at L1/L2 as the medullary cone
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Where and why are there enlargements in certain parts of the spinal cord?
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there are enlargements in the cervical and lumbar regions due to more neurons needed to innervate the limbs
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Where do spinal nerves exit from the vertebral column?
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-cervical nerves exit above the vertebra with the same number
-thoracic, lumbar, and sacral nerves exit below the vertebra with the same number -the nerve roots are longer as you descend the vertebral column |
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What is the cauda equina?
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although the spinal cord ends at vertebra L1/L2 the area below this isn’t “empty”, the roots for more caudal spinal nerves descend within the vertebral canal before exiting through the correct intervertebral foramina, these roots collectively called the cauda equina
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What are the three different spinal meninges?
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1. dura mater
2. arachnoid 3. pia mater |
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What are the denticulate ligaments and what layer do they originate in?
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They prevent the spinal cord from moving side to side and are located in the pia mater
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Where is the large subarachnoid space located?
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it is located between L2 and S2
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What is a lumbar puncture and what is it used for?
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a needle is inserted into the large subarachnoid space to withdraw CSF to test for meningitis
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How far down the spinal cord does the pia mater extend?
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a piece of it extends into the medullary cone
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How far do the pia mater and arachnoid layer go?
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they both continue to vertebral level S2
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Where is the white matter located in the spinal cord and what functions does it have?
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The white layer is located on the outside of the spinal cord and contains only axons that organized into tracts
-allows the brain and brainstem to communicate with the spinal cord -allows for communication between distant levels of the spinal cord -dorsal columns, lateral columns, ventral columns |
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What is the gray matter of the spinal cord, where is it located and what does it do?
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the gray matter is at the center of the cord and contains all the nerve cell bodies
-cell bodies are separated by function and organized in nuclei -dorsal horn, lateral horn, ventral horn |
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What does the dorsal horn contain?
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it contains all sensory cell bodies
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What does the lateral horn contain and where is it located?
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the lateral horn contains visceromotor neurons and is present from T1-L2 and S2-S4
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What does the ventral horn contain?
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contains somatomotor neurons for skeletal muscles
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What is the Dorsal Root Ganglia?
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-the DRG contains cell bodies for all sensory info coming in at this level
-contains unipolar cells with peripheral and central processes incoming sensory info has two options - |
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What are the two options for incoming sensory info at the DRG?
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it can either ascend to the brain
or it may synapse on the spinal cord to form a reflex |
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What are the different connective tissues of the nerve?
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-epineurium
-perineurium -endoneurium |
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What does the epineurium do?
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it encloses the entire nerve and all its axons
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What does the perineurium do?
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it wraps around bundles and fasicles of axons
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what does the endoneurium do?
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it wraps around individual axons
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What are the components of a reflex arc?
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-a receptor
-a sensory neuron -a motor neuron -an effector |
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What is the simplest kind of reflex?
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a monsynaptic stretch reflex-(the muscle is stretched, a receptor in the muscle senses the stretch and sends a signal to the somatomotor neurons causing a reflex
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What do motor neurons do?
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-they cannot fire without input
-two sources for input: 1. incoming sensory input for a reflex 2.descending input from higher brain centers |
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What are the ascending tracts of the spinal cord?
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they are all sensory tracts
-dorsal columns -anterolateral system/ lateral spinothalamic tract -dorsal spinocerebellar tract |
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What is the descending tract of the spinal cord?
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these are motor tracts
-lateralcoritcospinal tract |
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What information do the dorsal columns carry?
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-fine touch
-sensory modalities -vibration -conscious proprioception |
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What kind of neurons do the dorsal columns use?
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-highly specialized sensory receptors
-unipolar sensory neurons -dendrite is directly continuous with the axon -cell body NOT between them, cell body in DRG |
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Where do axons ascend within the dorsal columns?
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-there are two subdivisions within the dorsal columns where the axons ascend through the fasciculus gracilis (S5-T7)
and fasciculus cuneatus (T6-C2) |
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What is the first order neuron for all ascending tracts?
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the DRG!!
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What do the FG and FC go to?
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they ascend to the brain so you are conscious of it
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where does the second order neuron go in the dorsal columns?
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the second axon crosses the midline, ascends to the thalamus and synapes on the third order neuron third order neuron
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where is the third order neuron and where is it going?
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third order neuron ascends to the cerebral cortex (postcentral gyrus)
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What are some deficits from a Dorsal Column lesion?
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-ipsilateral loss of:
-fine touch -vibration sense -conscious proprioception |
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What information does the anterolateral system/spinothalamic modalities carry?
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-pain
-temperature |
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Where is the first order neuron of the Anterolateral system?
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it is in the DRG
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Where is the second order neuron in the anterolateral system?
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synapse immediately on 2nd order neurons in the dorsal horn
-they then cross to contralateral side then ascend in the spinothalamic tract |
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What do axons in the spinothalamic tract synapse on?
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they synapse on third order neurons in the thalams which ascend to the cerebral cortex
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Lesions of the spinal cord in the dorsal horn would cause what type of damage?
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ipsilateral loss of pain and temperature
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Lesions of the spinothalamic tract would cause?
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contralateral loss of pain and temperature
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What type of information does the dorsal spinocerebellar tract carry?
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-carries info from sensory receptors in skeletal muscles
-information involved in reflexes and supplies the cerebellum with info about the muscle -unconscious proprioception |
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Where are the three neurons located?
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first order neuron located in DRG
synapse on second in Clarkes column in the dorsal horn second axon ascends in the DSCT and terminates in the cerebellum entirely ipsilateral |
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Lesions of the DSCT cause what type of damage?
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deficits are always ipsilateral
incoordination |
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What happens with dorsal root damage?
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loss of all sensation and reflexes
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How many Cervical, Thoracic, Lumbar, and Sacral Nerves are there?
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8 cervical
12 thoracic 5 lumbar 5 sacral 1 coccygeal nerve |
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What does the dorsal ramus innervate?
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it innervates the deep back muscles and the skin of back
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What does the ventral ramus innervate?
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innervates everything else- the rest of the body wall and the limbs
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What are dermatones?
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the area of skin innervated by a single spinal nerve
C2- back of the head T4- nipple line T10- umbilicus S1- lateral foot S4/5- perianal region |
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What is the clincial relevance/diagnosis reason for dermatones?
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-can tell the level of a spinal cord lesion
-level of a herniated disc -level to anesthetize -level involved in shingles |
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Where does shingles lie dormant?
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-lies dormant in the dorsal root ganglia
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What are plexuses?
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spinal nerves do not travel separately to targets, plexus is formed when mutliple ventral rami come together
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What nerves are involved in the Brachial Plexus?
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-axillary nerve:innervates shoulder muscle (deltoid)
-musculocutaneous nerve- innervates anterior arm muscle (biceps brachii) -median nerve: innervates anterior forearm -radial nerve: innervates posterior arm, forearm and hand (triceps) -ulnar nerve: innervates anterior forearm |
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What nerves are involved in the Lumbar Plexus?
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- femoral nerve: supplies anterior thigh muscles (quadriceps femoris)
-obturator nerve: supplies medial thigh muscles |
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What nerves are involved in the Sacral Plexus?
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the sciatic nerve splits into:
-tibial nerve: posterior thigh, leg, foot, hamstring, soleus, gastroenemius -common fibular: anterior leg and foot, tibialis anterior |
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What is the grey and white arrangement of the brain?
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-gray is external
-white is internal |
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What are the three cranial meninges or protective coverings?
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-dura mater
-arachnoid -pia mater |
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What is the dura mater?
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-tough outer layer and is made up of two layers
-periosteal layer -meningeal layer |
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What is the arachnoid layer?
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-middle layer that is just outside the subarachnoid space and contains CSF
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What is the pia mater?
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-innermost delicate layer that follows all contours of brain
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Why are there no epidural spaces on the Cranial dura mater?
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-it is fused to the surface of the skull
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What is a dural reflection?
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-stabilize brains position to prevent it from moving too much from a blow to the head
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What are dural sinuses?
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-collect venus blood from brain and return CSF back to vascular system
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What do the Arachnoid Villi do?
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allow CSF to drain from subarachnoid space into the blood
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What is a epidural hematoma?
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-skull fractures can tear arteries that travel between periosteal dura and the skull causing bleeding into the epidural space
- high pressure bleed and demands immediate attention |
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What is a subdural hematoma?
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-occurs when a vein that drains into the sinuses are torn
-these are low pressure bleeds |
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What function do ependymal cells serve?
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-line ventricles of brain
-produce CSF |
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What are ventricles of the brain?
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-spaces in brain lined by ependymal cells and filled with CSF
-lateral (2)-third and fourth -openings in 4th ventricle allow CSF to pass into subarachnoid space |
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Where do cranial nerves I and II not go?
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-they dont go into the brainstem
-CN I- olfactory CN II- optic |
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Which Cranial nerves pass through the midbrain?
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CN III, IV
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What does CN I do?
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-olfactory
-sensory -smell |
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What does CN II do?
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-optic
-vision -sensory |
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What does CN III do?
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-oculomotor
-motor -somatomotor- moves extraocular muscles of eye -visceromotor-sphinctor of pupil and cilliary muscle |
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How does the sphincter of the pupil work?
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-when circular muscles of iris contracts, the pupil constricts
-occurs when we are in bright conditions -parasymp stimulation causes circular muscles to contract -symp causes radial muscles to contract |
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How does the cilliary muscle work and what does it control?
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-contraction changes shape of the lens, so you can focus on nearby objects
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What are the different types of extraocular muscles and what type of movement do they cause?
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-6 muscles move the eye
-4 rectus muscles - medial, superior, lateral, inferior -2 obliques- superior and inferior elevation-superior rectus aduction-medial rectus depression-inferior rectus abduction-lateral rectus |
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What does CN IV do?
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-trochlear Nerve
-motor -controls superior oblique |
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Which nerves are located in the pons?
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V, VI, VII, VIII
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What does CN V do?
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-trigeminal
-sensory from skin of the face and teeth -motor to muscles of mastication (involves temporalis, lateral ptyerigoid, medial pterygoid, masseter) |
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What does CN VI do?
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-abducens
-abducts eye Lateral rectus muscle -motor |
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What does CN VII do?
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-facial nerve
-motor to muscles of facial expression (obicularis oculi, zygomaticus major, obicularis oris, buccinator) -taste of anterior tongue -visceromotor to almost all glands of head both sensory and motor |
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What does CN VIII do?
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-vestibulocochlear nerve
-innervates inner ear -sensory |
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Which cranial nerves are in the Medulla?
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-contains centers for HR and respiration
-nucleus cuneatus and nucleas gracilus of dorsal columns -pyramids of corticospinal fibers -CN IX, X, XI, XII |
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What does CN IX do?
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-glossopharyngeal
-both special sensation (taste) and general sensation from posterior tongue -general sensation from pharynx -salivary gland secretion parotid gland |
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What does CN X do?
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-Vagus
-innervates skeletal muscle of larynx, pharynx, and palate -smooth muscle of thoracic and abdominal organs and glands |
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What does CN XI do?
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Accessory nerve
-originates in spinal cord -innervates two muscles in neck -trapezius -sternocleidomastoid |
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What does CN XII do?
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hypoglossal
motor to skeletal muscles of tongue |
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What kind of incoordination does cerebellar damage result in?
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ipsilateral
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What sensory info does not pass through the thalamus?
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olfactory
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What are thalamic projections?
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-CN form comparable tracts that synapse in thalamus
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What function does the hypothalamus serve?
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-"homeostasis"
-food intake body weight control water balance autonomic nervous system control endocrine functions via pituitary memory |
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Where are the language areas in the brain located?
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in the left hemisphere
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What function does Wernickes area serve?
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-in sensory cortex
-receives input from both auditory and visual cortex -allows you to understand speech or written word |
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What function does Brocas area serve?
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-in motor cortex
-allows you to formulate words |
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What is nonfluent aphasia?
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-understand words but cant respond well
-brocas area not working |
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What is fluent aphasia?
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-dont understand but speak words
-wernickes not working |
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What are cortical tracts?
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-bundles of axons that allow cerebral cortex to communicate with other areas of CNS
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What function do association tracts have?
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allow cortical areas in one hemisphere to communicate (like wernikes and brocas_
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What function do projection tracts have?
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-allow cortex to communicate with lower areas
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What do commissural tracts allow?
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-communication between the two hemispheres (corpus callosum)
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