Neurophysiology Intro

Divisions of the Nervous System

Central Nervous System

Peripheral Nervous System

Central Nervous System (CNS)

Everything covered by meninges

Brain, spinal cord, CNI, CNII, retina

Peripheral Nervous System (PNS)

Divided into sensory and motor

Communication between CNS and body

PNS sensory division

Afferent

Somatic (body) and special senses (head)

PNS motor division

Efferent

Divided into somatic motor and autonomic motor

Somatic motor system

Controls voluntary skeletal muscle movement

Autonomic motor system

Sympathetic and parasympathetic divisions

Regulates involuntary movements (smooth/cardiac muscle and glands)

Gray matter

Cell bodies

White matter

Myelinated axons

Wiring connecting neurons together

Where is gray matter in the brain?

Cortex on the surface or basal ganglia interiorly

Where is gray matter in the spinal cord?

Dorsal and ventral horns interiorly

Where is white matter in the brain?

Interiorly

Made of tracts, fasciculi, or other fibers

Where is white matter in the spinal cord?

On the surface

Tracts run up and down

Types of white matter fibers

Projection, commissural, association

Projection fibers

Project up and down spinal cord

Ascending tracts - Sensory

Descending tracts - Motor

Commissural fibers

Axons that cross midline to coordinate activity

Brain: Connect two hemispheres (corpus callosum and anterior commissure)

Spinal cord: Anterior commissure

Corpus callosum

Commissural fibers

Connect superior R and L hemispheres

Anterior commissure

Commissural fibers

Connects inferior R and L hemispheres

Association fibers

Connect nuclei within a hemisphere

Arcuate fibers

Association fibers

Connect adjacent nuclei within the same hemisphere

Longitudinal fibers

Association fibers

Connect nuclei from sensory domains of the brain with the decision making part of the brain

Spinal cord segments

Cervical, thoracic, lumbar, sacral

Spinal cord functions

Convey sensory and motor info to and from brain

Integrates sensory and motor info for reflexes (reflex arc)

Spinal nerves

31 pairs, part of PNS

Dorsal root and dorsal root ganglia (DRG) - Sensory

Ventral roots - Motor

Dermatome

Spinal nerve that is responsible for sensory/motor info on an area of skin

Cervical enlargement

Sensory input and motor output for arms

Lumbar enlargement

Sensory input and motor output for legs

Fissure

Deep furrow

Sulcus

Valley

Gyrus

Hill or ridge

Parietal lobe function

Somatosensory

Body sensations

Occipital lobe function

Visual processing

Temporal lobe function

Sound

Frontal lobe function

Decision making, personality, motor

Majority of the brain is…

Sensory (always in the back)

Limbic system

Group of nuclei with special functions

Amygdala, hippocampus, thalamus, hypothalamus

Amygdala

Emotions, especially fear and anger

Hippocampus

Memory formation and retrieval/learning

Closely located near amygdala and olfaction

Thalamus

“Union Station”

All sensory information comes in and gets distributed here

Hypothalamus

Stress response and regulation of BP and hormones

Brodmann Areas

51 per hemisphere, mapped areas based on cortical thickness of 6 layers

Overlap with function

Thalamus primary sends info to layer…

4

Which layers are larger in motor areas?

Layers 5 and 6

Lobe and cortex pairings

Parietal lobe - Somatosensory cortex

Occipital lobe - Visual cortex

Temporal lobe - Auditory cortex

Frontal lobe - Prefrontal and motor cortex

Association cortices

Cortical areas that integrate information from other cortical regions

Higher level thinking

Parietal association cortex

Combines sensory information

Somatotopic map (sensory)

Map of the body in the sensory cortex

Sensory homunculus

Retinotopic map

Map of visual field in visual cortex

Somatotopic map (motor)

Map of body muscles in motor cortex

Motor homunculus

Tonotopic map

Map of sound in auditory cortex

Based on tones

Somatosensory cortex

Sensory homunculus is distorted based on volume of sensory fibers from a particular area

Genitals, feet, hands, face

Lesions to somatosensory cortex

Paresthesia: Abnormal sensation (pins and needles)

Anesthesia: Loss of sensation

Visual cortex

L VF goes to R hemisphere, R VF goes to L hemisphere

Superior VF goes to lingual, inferior VF goes to cuneus

Dorsal stream

Visual where and how

Project to parietal association cortex

Ventral stream

Visual who and what

Project to parietal association cortex

Lesions to visual cortex

Agnosia: Don’t know what they’re looking at

Auditory cortex

Most sounds stay ipsilateral for sound location

Cochlea

The deeper the tone, the deeper into the cochlea it is registered

Mimicked in primary auditory cortex

Lesions to auditory cortex

No presentation if only 1 hemisphere is affected

Central deafness: Both hemispheres affected, can hear but not process sounds

Flaccid paralysis

Limp, no control

Spastic paralysis

Increased muscle tone

Stiff muscles, involuntary spasms

Motor cortex

Motor homunculus mirrors sensory homunculus

Lesions to motor cortex

Paresis: Weakness or poor control

Paralysis: Loss of movement control

Lateralization

Some functions/processes are specialized in one hemisphere

Language functions depend on…

Hemispheric dominance

If a patient is R handed they are…

L hemisphere dominant

If a patient is L handed they are…

R hemisphere dominant

Dominant hemisphere in language

Broca’s area and Wernicke’s area

Non-dominant hemisphere

Necessary for emotional tone, context, humor, sarcasm, non-verbal communication

Frontal lobe: Emotion into language

Parietal lobe: Interpreting context

Broca’s Area

BA 44+45, in posterior part of inferior frontal gyrus

Responsible for language expression

Wernicke’s Area

BA 22, in superior temporal gyrus

Language comprehension

Broca’s Aphasia

Difficulty expression language but can understand

Wernicke’s Aphasia

Difficulty comprehending language but can express language (meaningless)

Global Aphasia

Both Wernicke and Broca’s damaged

Cannot communicate or understand

Visual field attention

L parietal lobe: R world

Right parietal lobe: R+L world

Hemispatial neglect

Lesion in R hemisphere causes pt to ignore L visual world