Spinal Nerves, Dermatomes, and Spinal Nerves, Dermatomes, and Cranial NervesCranial Nerves

Handout for Cranial NervesHandout for Cranial Nerves

Spinal NervesSpinal Nerves

1. 31 pairs1. 31 pairs2. spinal canal emergence2. spinal canal emergence3. distribution3. distribution

a. 8 cervicala. 8 cervical b. 12 thoracicb. 12 thoracic c. 5 lumbarc. 5 lumbar d. 5 sacrald. 5 sacral e. 1 coccygeale. 1 coccygeal

Cervical Plexus

Brachial plexus

Lumbar Plexus

Sacral and CoccygealPlexus

Typical Spinal NerveTypical Spinal Nerve

1. mixed nerve1. mixed nerve

2. connective tissues2. connective tissues

a. endoneuriuma. endoneurium

b. perineuriumb. perineurium

-- fascicles-- fascicles

c. epineuriumc. epineurium

DermatomesDermatomes

Cranial NervesCranial Nerves

1. 12 pairs1. 12 pairs

2. motor components -- arise from brain 2. motor components -- arise from brain stem gray matterstem gray matter

3. sensory components -- arise in ganglia 3. sensory components -- arise in ganglia outside brainoutside brain

Cranial NervesCranial Nerves

Cranial Nerves NamesCranial Nerves Namesnamename mnemonicmnemonic

I. olfactory OnI. olfactory On II. optic OldII. optic Old III. oculomotor Olympus'III. oculomotor Olympus' IV. trochlear ToweringIV. trochlear Towering V. trigeminal TopV. trigeminal Top VI. abducens AVI. abducens A VII. facial FinnVII. facial FinnVIII. auditory AndVIII. auditory And IX. glossopharyngeal GermanIX. glossopharyngeal German X. vagus ViewedX. vagus Viewed XI. accessory AXI. accessory A XII. hypoglossal HopXII. hypoglossal Hop

Cranial Nerve FunctionsCranial Nerve Functions name function mnemonicname function mnemonic

I. olfactory sensory Some I. olfactory sensory Some II. optic sensory SayII. optic sensory Say III. oculomotor motor MarryIII. oculomotor motor Marry IV. trochlear motor MoneyIV. trochlear motor Money V. trigeminal both ButV. trigeminal both But VI. abducens motor MyVI. abducens motor My VII. facial both BrotherVII. facial both BrotherVIII. auditory sensory SaysVIII. auditory sensory Says IX. glossopharyngeal both BadIX. glossopharyngeal both Bad X. vagus both BusinessX. vagus both Business XI. accessory motor MarryingXI. accessory motor Marrying XII. hypoglossal motor MoneyXII. hypoglossal motor Money

Nervous IntegrationNervous IntegrationHandout Spinal TractsHandout Spinal Tracts

A. SensationA. Sensation 1. Levels of sensation1. Levels of sensation 2. Modality2. Modality 3. Components of a sensation3. Components of a sensation 4. Generator potentials and4. Generator potentials and receptor potentialsreceptor potentials 5. Adaptation of sensory receptors5. Adaptation of sensory receptors B. General sensesB. General senses 1. Cutaneous sensations1. Cutaneous sensations 2. Proprioceptive sensations2. Proprioceptive sensations C. Physiology of sensory pathwaysC. Physiology of sensory pathways 1. Posterior column-medial lemniscus1. Posterior column-medial lemniscus pathwaypathway 2. Anterolateral (spinothalamic)2. Anterolateral (spinothalamic) pathwayspathways 3. Somatosensory cortex3. Somatosensory cortex D. Physiology of motor pathwaysD. Physiology of motor pathways 1. Direct (pyramidal) pathways1. Direct (pyramidal) pathways 2. Indirect (extrapyramidal) pathways2. Indirect (extrapyramidal) pathways

The three essential functions of The three essential functions of the nervous system are:the nervous system are:

1. sense changes1. sense changes

2. integrate and interpret2. integrate and interpret

3. respond3. respond

How do the various components of the How do the various components of the nervous system cooperate in nervous system cooperate in performing these functions?performing these functions?

Sensation versus PerceptionSensation versus Perception

A sensation may or not be perceived A sensation may or not be perceived (conscious awareness of the stimulus)(conscious awareness of the stimulus)

Modality-the type of stimulus or Modality-the type of stimulus or sensation it produces –vision, hearing, sensation it produces –vision, hearing, taste.taste.

Levels of SensationLevels of Sensation

1. spinal1. spinal

2. brain stem2. brain stem

3. thalamus3. thalamus

4. cerebral cortex4. cerebral cortex

Components of a SensationComponents of a Sensation

1. stimulation1. stimulation

2. transduction2. transduction

3. conduction3. conduction

4. translation4. translation

Generator PotentialsGenerator Potentials

1. always produce depolarization1. always produce depolarization

2. will initiate an action potential in a sensory 2. will initiate an action potential in a sensory neuron if the stimulus is strong enough to neuron if the stimulus is strong enough to form threshold depolarizationform threshold depolarization

3. all receptors except those for vision, hearing,3. all receptors except those for vision, hearing, equilibrium, smell, and taste createequilibrium, smell, and taste create generator generator potentialspotentials

Receptor PotentialsReceptor Potentials

1. may produce depolarization or 1. may produce depolarization or hyperpolarizationhyperpolarization

2. never directly initiate an action potential 2. never directly initiate an action potential in a sensory neuronin a sensory neuron

3. directly regulates release of 3. directly regulates release of neurotransmitter onto a sensory neuron that neurotransmitter onto a sensory neuron that may initiate threshold depolarizationmay initiate threshold depolarization

Types of ReceptorsTypes of Receptors

1. interceptors (visceroceptors)1. interceptors (visceroceptors)2. exteroceptors2. exteroceptors3. proprioceptors3. proprioceptors

____________________________________________________mechanoreceptorsmechanoreceptorsthermoreceptorsthermoreceptorschemoreceptorschemoreceptorsnociceptorsnociceptorsphotoreceptorsphotoreceptors

Adaptation of sensory receptorsAdaptation of sensory receptors

1. fast-adapting (phasic) receptors1. fast-adapting (phasic) receptorsAdapt very quicklySpecialized for signaling changes in a particular stimulusPressure, touch, hot, smell

2. slow-adapting (tonic) receptors2. slow-adapting (tonic) receptorsAdapt slowly, continuing to initiate impulses as long as

stimulus persistsPain, body position, cold, chemical composition of blood

Cutaneous SensationsCutaneous Sensations

1. tactile, thermal, pain1. tactile, thermal, pain

2. receptor locations2. receptor locations

3. receptor distribution3. receptor distribution

Proprioceptive SensationsProprioceptive Sensations

1. proprioceptors1. proprioceptors

2. locations2. locations

3. body position sense3. body position sense

4. adapt slowly4. adapt slowly

Physiology of Sensory PathwaysPhysiology of Sensory Pathways

1. most sensory input decussates1. most sensory input decussates

2. somatosensory cortex2. somatosensory cortex

3. perception3. perception

4. Three neurons are required4. Three neurons are required

a. first-order neurona. first-order neuron b. second-order neuron b. second-order neuron

c. third-order neuronc. third-order neuron

Tracts of the Spinal CordTracts of the Spinal Cord

Posterior Column PathwayPosterior Column Pathway

1. fasciculus gracilis & fasciculus cuneatus2. nucleus gracilis & nucleus cuneatus3. decussation in medulla4. medial lemniscus5. Thalamus6. Somatosensory Cortex

discriminative touchstereognosiskinesthesiavibrationweight, discriminationconscious proprioception

Anteriolateral PathwaysAnteriolateral Pathwayslateral spinothalamiclateral spinothalamic

-Pain, thermal

anterior spinothalamic tractsanterior spinothalamic tracts -Itch,tickle,pressure,crude touch

decussate at gray commissuredecussate at gray commissure

Somatosensory CortexSomatosensory Cortex1. homunculus1. homunculus

2. areas of representation2. areas of representation

3. receptor to cortical 3. receptor to cortical

neuron ratio = 1:1neuron ratio = 1:1

Motor CortexMotor Cortex

1. reflex vs voluntary action1. reflex vs voluntary action

2. homunculus2. homunculus

3. areas of representation3. areas of representation

4. motor neuron to motor 4. motor neuron to motor

unit ratio = 1:1unit ratio = 1:1

5. upper motor neuron5. upper motor neuron

6. lower motor neuron6. lower motor neuron

Direct Pyramidal Motor PathwaysDirect Pyramidal Motor Pathways

1. lateral corticospinal tracts1. lateral corticospinal tracts

-- decussate at medulla-- decussate at medulla

2. anterior corticospinal tracts2. anterior corticospinal tracts

-- decussate at gray commissure-- decussate at gray commissure

3. corticobulbar tracts3. corticobulbar tracts

-- decussate in brain stem-- decussate in brain stem

Indirect (extrapyramidal) pathways for coordinationIndirect (extrapyramidal) pathways for coordination andand control of movementcontrol of movement

cerebral nuclei

thalamus

cerebellum

brainstem gray matter

spinal cord association neurons

lower motor neurons

skeletal muscles

upper motor neurons of the

pyramidal tracts

cerebral cortex

upper motor neurons of the extrapyramidal tracts:

rubrospinaltectospinal

vestibulospinalreticulospinal

INDIRECT (EXTRAPYRAMIDAL) MOTOR PATHWAYS

cerebral nuclei

thalamus

cerebellum

brainstem gray matter

spinal cord association neurons

lower motor neurons

skeletal muscles

upper motor neurons of the

pyramidal tracts

cerebral cortex

upper motor neurons of the extrapyramidal tracts:

rubrospinaltectospinal

vestibulospinalreticulospinal

end