Neuro – A & P, Assessment, DiagnosticsChapter 41

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Grey’s Anatomy Quote

• The brain is the human body's most mysterious organ. It learns. It changes. It adapts. It tells us what we see. What we hear. It lets us feel love. I think it holds our soul. But no matter how much research we do, no one can really say how all that delicate gray matter inside our skull works. And when it's hurt, when the human brain is traumatized, well... that's when it gets even more mysterious.

Nervous System

• What does it do?

• How does it do it?

ANATOMY

Neurons

• Initiate and transmit impulses• High metabolic rate• Longevity• Typically non-mitotic• Variety of shapes and sizes• Comprised of a cell body, dendrites and

axons

Sensory vs. Motor

• Sensory Neurons (afferent)

– Transmit information to the CNS

• Motor Neurons (efferent)

– Transmit information away from the CNS

Impulse Conduction

Reflex Arc

– Functional unit that provides the pathways for the nerve impulses

– The passage of the impulses is called• Reflex act or Reflex

– Process of Reflex Arc

• Neural impulses

Anatomy

Neuroglial Cells– Four types

• Capable of mitosis and replacing damaged neurons

• Aid in neuronal development• Do not transmit nerve impulses• Protect, nourish and provide support for

the neurons

Anatomy

Action Potentials– Movement of an electrical charge thru an

impulse along the axon membrane– Allows for communication with neurons and

body cells– Initiated by a stimulus– Propagated by rapidly charged ions thru the

cell membrane– Faster in myelinated fibers

Anatomy

Neurotransmitters• Synaptic Transmission

– One way communication that link the neurons by a chemical synapse

– Either inhibitory or excitatory– Chemical neurotransmitters

• Acetylcholine• Norepinephrine• Dopamine• Histamine• GABA (gamma aminobutyric acid)• Serotonin

Factors Effecting Neurotransmission

• Distance

• Strength of Stimulus– Inhibition– Inadequate transmitter substance– ECF changes

• pH• O2

• Medications

PHYSIOLOGY

Physiology

• Central Nervous System (CNS)

– Brain

– Spinal Cord

Brain Parts and Function

• Bone• Meninges• Cerebrum• Brainstem• Circle of Willis

Brain

Table 41-1 General Functions of the Four Regions of the Brain

Figure 41–3 Lobes of the cerebrum and functional areas of the cerebral cortex.

Table Functions of Lobes of the Cerebrum and Areas of the Cerebral Cortex

CSF

• Clear and Colorless• From blood plasma – 99% water

– Contains protein, sodium, chloride, potassium, bicarbonate and glucose

• 80 – 200 mL total volume– Replaced several times per day

• Cushion for the brain and spinal column• Provides nourishment and removes

waste

Circulation and the BBB

Circulation• 750 mL of blood per minute• Uses 20% of the total O2

– Needed for the metabolism of glucose – sole source of energy.

BBB• Allows lipids, glucose, some amino acids,

water, CO2 and O2

• Other substances are prevented from crossing

Figure 41–5 Major arteries serving the brain and the Circle of Willis.

Spinal Cord

• Center for conducting messages to and from the brain and a reflex center

• 33 vertebrae– 7 cervical– 12 thoracic– 5 lumbar– 5 sacral– 4 fused which form the coccyx

Function

Ascending tracts- start in spinal cord and end in the brain• Spinothalamic• Spinocerebellar

Descending tracts - start in the brain and end in the spinal cord

Physiology

• Peripheral Nervous System (PNS)

– 12 pairs of Cranial nerves

– 31 pairs of Spinal nerves

– Autonomic nervous system• Sympathetic system• Parasympathetic system

• Cranial Nerve Song

Dermatones

• Area of skin that is innervated by cutaneous branches of a single spinal nerve

• Provide anatomic landmarks to locate neurologic lesions

Autonomic Nervous System

Regulates involuntary activity (cardiovascular, respiratory, metabolic, body temps etc)

• Sympathetic (SNS)

• Parasympathetic (PNS)

Autonomic Nervous SystemArea Affected Sympathetic Parasympathetic

Pupil Dilates Constricts

Bronchi Dilates Constricts

Heart Increases Rate Decreases Rate

GI Inhibits peristalsisStimulates sphincter

Stimulates peristalsisInhibits sphincter

Adrenal Glands Increases secretion of EN and NE

Bladder Relaxes Bladder muscleConstricts sphincter

Contracts bladder muscleRelaxes sphincter

Neurological Assessment

History• Family history/genetic risks• Personal history• Current health problems• Social history

Mental Assessment

• Mental status• Memory• Attention• Language/Copying• Cognition

Cranial Nerve Assessment

• Done to establish a baseline for future comparison to rule out deterioration

Sensory Function Assessment

• Completed on patients with problems affecting spinal cord or spinal nerves: trauma, intervertebral disk disease, infections

• Evaluate: pain, temperature touch

Figure 41–12 Testing two-point discrimination.

Assessment of Motor Function

• Muscle strength• Cerebral/brainstem integrity

• Pronator Drift

Assessment of Cerebellar Function

• Coordination• Gait and equilibrium

Figure 41–13 Heel-to-shin test.

Assessment of Reflex Activity

• Deep tendon reflexes• Cutaneous (Superfical) reflexes• Abnormal findings

Box 41-1 Abbreviated Neurologic Assessment (Neuro Check)

Table 41-5 Glasgow Coma Scale

Diagnostic Assessment

• Laboratory–CSF

• Lumbar Puncture

Diagnostic Assessment

• Radiographic–Cerebral Angiography–CT–PET–SPECT–Cerebral Blood Flow Evaluation–Brain Scan

Diagnostic Assessment

• Other–MRI–EEG–EMG–Transcranial Doppler