PRAXIS: The nervous system

neurology

study of neurological disorders

Neuroanatomy

study of structures of nervous sytem

Neurophysiology

study of function of nervous system

sensory/afferent nerves

give sensory info to brain

motor/efferent nerves

take motor signals away from brain to limbs or whatever

Glial Cells (Neuroglia)

called Schwann Cells/satellite cells in PNS (mostly protect nerve cells)

Called Astrocytes, Oligodendrocytes, Microglia, or Ependymal Cells in CNS (mostly produce myelin sheaths, repair synapses after injury, and support blood brain barrier)

Neurons

Most important nerve cell

transmit info to other neurons

soma

cell body

nucleus

core of neuron

dendrites

receive info from other cells

myelin sheath

wrapped around axon that insulates and makes message go faster

what provides the myelin sheath?

PNS: Schwann Cells

CNS: oligodendroglia

What two neurotransmitters are important to either inhibit or excite a neuron?

Acetylcholine and Dopamine

Afferent neurons

Sensory neurons

Sensory messages from organs to brain

Efferent Neurons

motor neurons

send motor messages away from PNS

interneurons

most common neuron!

links neurons with other neurons which plays an important role in controlling movement or sensation

Where do cranial nerves exit from in the skull?

Foramina (little holes in skull)

CN 1

Olfactory

Smell

Sensory nerve

Originates in nasal cavity

CN II

Optic

sight

sensory

originates in retina

CN III

oculomotor

eye movement

motor

originates in midbrain

CN IV

Trochlear

Eye movement

motor

originates in midbrain

CN V (important for speech)

trigeminal

mixed

Sensory: ophthalmic branch: sensation for nose, eyes, and forehead

Maxillary branch: sensation to nose, upper lip/cheek/teeth, maxilla, palate, and nasopharynx

Mandibular branch: sensation to mandible, lower lip/teeth, tongue, part of external ear, and all senses except taste of anterior 2/3 of tongue

mandibular also has motor fibers for jaw muscles

CN V innervation

innervated bilaterally so unilateral UMN damage doesn’t do much damage

CN VI

abducens

motor

eye movement

CN VII (Important for speech)

facial

mixed

sensory: taste to anterior 2/3 of tongue

motor: muscles for facial expression and speech

damage to CN VII

upper face is bilaterally innervated so upper UMN damage paralyzes only lower face

bilateral damage inhibits facial expressions and facial movements

CN VIII (important for speech!)

Vestibulocochlear

sensory

balance and hearing

Vestib branch: equilibrium/balance

acoustic branch: sensory info to cochlea → primary auditory cortex of brain

CN IX

glossopharyngeal

mixed

sensory: processing taste from posterior 1/3 of tongue and sensation for pharynx, tympanic cavity, Eustachian tube, and soft palate

motor: innervates stylopharyngeus that raises and dilates pharynx as well as pharyngeal plexus which innervates upper pharyngeal constrictors

CN X

Vagus

mixed

motor: heart, lungs, pharynx, larynx, and digestive system

sensory: heart, lungs, pharynx, larynx, digestive system, and epiglottis

also has RLN and SLN

Recurrent Laryngeal Nerve (RLN)

part of Vagus

regulates intrinsic muscles of larynx (not cricothyroid)

damage to this can cause paralysis of VF

courses under heart so can be damaged during heart surgey

pharyngeal branch

Part of Vagus

supplies muscles of pharyngeal constrictors and velum except tensor veli palatini (CN V) and sensory info from base of tongue and pharynx

Superior Laryngeal nerve

Part of Vagus

mixed

internal (sensory) receives info from from larynx above VF

external (motor) innervates cricothyroid (damage here means unable to change pitch)

CN XI

spinal accessory

motor

head and shoulder movements

innervates uvula with CN X

CN XII

hypoglossal

motor

supplies all intrinsic muscles and all extrinsic muscles (except for palatoglossus)

damage here can be tongue paralysis and swallowing problems

Spinal nerves

cervical: C1 - C8

thoracic: T1 - T12

lumbar: L1 - L5

sacral: S1 - S5

coccygeal: Co1

Autonomic nervous system

Part of PNS

sympathetic: fight or flight response, heart increases, blood pressure goes up, et.

Parasympathetic: rest and digest, reset from ^^^

CNS

brain and SC

enclosed in vertebral column

Brainstem

connects to brain via diencephalon

bridge between cerebellum and all CNS structures like SC

has longitudinal fiber tracts, CN nuclei, and reticular formation

notable structures are midbrain, pons, and medulla

Midbrain

aka mesencephalon

superior peduncles help connect brainstem to cerebellum

cerebral aqueduct runs through here

helps with visual reflexes, eye movements, and vestibular generated eye and head movements

has CN nuclei for CN IV and CN III

Pons

aka metencephalon

connects to cerebellum through inferior and middle peduncles

transmits info relative to movement from cerebral hemispheres to cerebellum

pons contains many descending motor fibers and is involved with hearing and balance.

had CN V and VII nuclei

Medulla ***

aka myelencephalon

lowest of brainstem parts

helps with vital automatic functions like breathing, digestion, heart rate, and blood pressure as well as reflexes like sneezing and blinking

had motor fibers that transmit motor input to several CN nuclei

has CN nuclei VII, IX, X, XI, and XII

pyramidal tracts control many muscle movements

Reticular Activating System ***

structure in midbrain, brainstem, and upper portion of SC

integrates motor impulse coming out and sensory input flowing in

alerts various cortexes to incoming impulses

primary mechanism of sleep/wake cycle

Diencephalon

above midbrain and between brainstem/cerebral hemispheres

has thalamus (sensory relay center) (also relays motor impulses from brainstem to motor areas of cortexes) and hypothalamus (emotions)

has third ventricle (has CSF)

basal ganglia ***

structures deep in brain near thalamus and lat ventricles. Gray matter.

highly complex pathways, cortical and subcortical. relay info from frontal lobe to higher centers of brain via thalamus

had globus pallidus, putamen, and caudate nucleus (all together: corpus striatum)

made of extrapyramidal systems which regulate and modify cortically intiated movements (substantia nigra is important here)

damage to basal ganglia

unusual body posture, dysarthria, dyskinesia, that interfere with a person’s ability to walk, speak, etc.

Cerebellum

two hemispheres separated by vermis

“modulates” neural activity

regulates equilibrium, body posture, and coordination of fine motor movements

superior, middle, and inferior peduncles connect with midbrain, pons, and medulla

all efferent (superior peduncles) and afferent fibers (inferior/middle peduncles) from this pass through the peduncles

Purkinje Cells

neurons in cerebellum

release GABA (inhibitor) to regulate coordination of motor movements

only output cells of cerebellum

damage to cerebellum

ataxia (abnormal gait, disturbed balance, and even ataxic dysarthria)

where is there gray matter?

on top of cerebrum and within SC and brainstem

gyrus/gyri

ridge (bumps) in brain

sulcus

small valley

fissures

deep valley in brain

longitudinal fissure

divides brain into R and L hemispheres

central sulcus

runs laterally and divides anterior and posterior brain