neural substrates exam 2 (chapters 5-8)

spinal cord form (external)

housed in boney vertebral column

• 5 sections

  • cervical, thoracic, lumbar, sacral, and coccygeal

• spinal nerves emerge from the spinal cord

spinal cord form (internal)

information superhighway conveying motor (efferent) and sensory (afferent) information between brain and body

• 4 fiber types

  • GSE fibers: to skeletal muscles

  • GVE fibers: to smooth muscle, heart and glands

  • GSA fibers: from skin

  • GVA fibers: from lungs and digestive tract

major landmarks of spinal cord

• dorsal ramus

• ventral ramus

• spinal nerve

• dorsal root

• ventral root

• dorsal horn

• ventral horn

• anterior median fissure

• dorsal funiculus

• lateral funiculus

• ventral funiculus

major motor tracts

• lateral corticospinal- contralateal body movement

• anterior (or ventral) corticospinal: trunk muscles

• rubrospinal: flexor tone

• vestibulospinal: extensor tone

major sensory tracts

• dorsal columns: fine touch, pressure, proprioception

• spinothalamic : pain, temperature, crude touch

• spinocerebellar: proprioception

function of the spinal cord

relaying efferent and afferent information between body and brain and mediating reflexes through the reflex arc

paraplegia/paraparesis

involves legs

quadriplegia/quadriparesis

involves arms and legs

spina bifida

neural tube defect that occurs during development in the womb

• multiple severities

• results in lower spinal cord damage

• paraparesis and bowel and bladder issues

myelitis

inflammation of the spinal cord

• can be caused y virus, bacteria, fungi, parasites, and toxic agents

• different types:

  • poliomyelitis: affects gray matter (motor loss)

  • leukomyelitis: affects white matter (sensory loss)

  • transverse myelitis: affects both gray and white matter (motor and sensory loss)

peripheral neuropathy

inflammation of the peripheral nervous system

• results in degeneration of the spinal nerves, typically in the feet

• caused by untreated diabetes, toxins, infections, and nutritional issues

  • paresthesia or anesthesia

function of the brainstem

regulating major life functions, mediating head and neck reflexes via cranial nerve, regulating alertness and wakefulness

ARAS (ascending reticular activation system)

receives fibers from the sensory pathways via long ascending spinal tracts

• alertness, maintenance of attention and wakefulness

• emotional reactions, important in learning processes

• tumor or lesion- sleeping sickness or coma

tegmental regions (brainstem)

reticular formation- consciousness

inferior olivary nucleus- motor movement control/coordination

red nucleus- flexor tone

nontegmental regions (brainstem)

tectum- superior (vision) and inferior (hearing) colliculi

cerebral peduncles

ventral pons- motor movement error correction

“ On Old Olympus Towering Top A Fin And German Viewed Some Hops”

olfactory

optic

oculomotor

trochlear

trigeminal

abducens

facial

vestibulocochlear

glossopharyngeal

vagus

spinal accessory

hypoglossal

motor cranial nerves are composed of 2 major neurons which are:

upper motor neuron and lower motor neuron

olfactory nerve

origin: olfactory bulb

function: smell

problems: anosmia

optic nerve

origin: retina

function: vision

problem(s): visual disturbances and loss of vision

right homonymous hemianopsia

loss of right visual field in both eyes

oculomotor nerve

origin: midbrain

function:

• GSE: moves eyes left and right; control eyelid

• GVE: pupil constrictor

problem: loss of pupillary light reflex; ptosis

trochlear nerve

origin: midbrain

function:

• GSE: moves eyes up and down

problem(s): nystagmus; difficulty moving eyes up and down

trigeminal nerve

origin: pons

function:

• GSA: touch, pain, temp. and vibration for face, anterior 2/3 of tongue

• GSE: muscles of mastication

problem(s): loss of facial sensations (trigeminal neuralgia); difficulty chewing; abnormal jaw-jerk reflex

3 branches:

1. ophthalmic

2. maxillary

3. mandibular

abducens nerve

origin: pons

function:

• GSE: rotates eyes out

problem(s): eye rotates in (strabismus) and diplopia; nystagmus

facial nerve

origin: pons

function:

• GVE: muscles of facial expression

• GVE: salivary glands (sublingual, submandibular) and lacrimal glands (tears)

• GSA: sensation near ears

• SVA: taste in anterior 2/3 of tongue

problem(s): facial paralysis/paresis; taste loss

vestibulocochlear nerve

origin: pons/medulla junction

function:

• SSA: hearing and balance

problem(s): hearing loss; balance problems; acoustic neuroma

glossopharyngeal nerve

origin: pons/medulla junction

function:

• SVE: pharyngeal movement

• GVE: parotid gland (salivation)

• GVA: middle ear, pharynx, posterior 1/3 of tongue

• SVA: taste on posterior 1/3 of tongue

problem(s): absent gag and swallow reflex; loss of taste; loss of pharyngeal movement

SVE

innervates muscles of swallowing

GVE

innervates parotid gland

GVA

middle ear, pharynx, posterior 1/3 of tongue

SVA

taste on posterior 1/3 of tongue

vagus nerve

origin: medulla

function:

• SVE: Supplies the voluntary muscles of the pharynx and most of the larynx, as well as one extrinsic muscle of the tongue.

• GVE: Parasympathetic innervation of the smooth muscle and glands of the pharynx, larynx, and viscera of the thorax and abdomen.

• GSA: Provides general sensory information from the skin of the back of the ear and external auditory meatus, parts of the external surface of the tympanic membrane, and the pharynx.

• GVA: Provides visceral sensory information from the larynx, esophagus, trachea, and abdominal and thoracic viscera, as well as the stretch receptors of the aortic arch and chemoreceptors of the aortic bodies

• SVA: Taste from epiglottis and pharynx

problem: absent gag and swallow reflex; loss of velar movement; loss of voice

3 major branches of the SVE

1. pharyngeal branch

2. superior laryngeal nerve

3. recurrent laryngeal nerve

pharyngeal branch

• Superior constrictor muscle

• Middle constrictor muscle

• Inferior constrictor muscle

• Levator palatini muscle

• Salpingopharyngeus muscle

• Palatopharyngeus muscle

• Palatoglossus muscle (of the tongue)

superior laryngeal nerve

• External Laryngeal Nerve:

  • Inferior constrictor muscle

  • Cricothyroid muscle

• Internal Laryngeal Nerve:

  • Sensory to the larynx

recurrent laryngeal nerve (RLN)

All intrinsic muscles of the larynx (except Cricothyroid)

• These muscles control the movements of the vocal folds.

right RLN

hooks posteriorly around the subclavian artery and also ascends in the groove between the esophagus and trachea.

left RLN

Longer; nerve loops posteriorly around the aortic arch and ascends to enter the groove between the esophagus and trachea.

consequences of LMN (lower motor neuron) damage

• difficulty swallowing

  • inability to elevate soft palate on affected side; paralysis of levator palatini muscle; pharyngeal muscles

  • soft palate droops on affected side and uvula deviates opposite affected side

gag reflex process

Sensory input → Glossopharyngeal nerve → Medulla → Motor output via Vagus nerve → Gag response

• Stimulus: The gag reflex is triggered when something touches the back of the throat, soft palate, or the back of the tongue.

• Afferent Pathway: Sensory receptors in the throat (e.g., pharyngeal and palatal areas) send signals to the glossopharyngeal nerve (CN IX).

• CNS Processing: The signal is relayed to the medulla oblongata (brainstem), which processes the sensory input.

• Efferent Pathway: The motor response is carried via the vagus nerve (CN X) to the muscles of the soft palate, pharynx, and larynx, causing contraction and the reflexive gagging response.

• Action: This causes a rapid contraction of the muscles, leading to a gagging sensation, which helps expel or prevent the object from entering the airway.

spinal accessory nerve

origin: medulla and spinal cord

function:

• GSE: neck and shoulder muscles

problem(s): droopy shoulder; movement of neck

hypoglossal nerve

origin: medulla

function:

• GSE: muscles of tongue

• UMN innervate predominantly the contralateral hypoglossal nuclear

• problem(s): loss of tongue movement; tongue fasciculations, tongue atrophy

consequences of UMN and LMN damage

deviated tongue

cerebellum functions

motor

• planning, monitoring, and correction of motor movement using sensory feedback

• fine motor activity

• monitors head and body position

• learning new motor skills

linguistic

• perception of speech/language, verbal working memory, verbal fluency, grammar processing, writing, and reading

cerebellar peduncles

superior cerebellar peduncle: connects cerebellum to midbrain

middle cerebellar peduncle: connects cerebellum to pons

inferior cerebellar peduncle: connects cerebellum to medulla

ataxia

discoordinated, “clumsy” movements

dysmetria

over- or under- shooting touching a target

disdiadokinesia

inability to perform rapid, alternating movements of hand or mouth

nystagmus

fast involuntary eye movements (side-side, up-down)

ataxic dysarthria

“scanning speech” (syllable by syllable)

hypotonia

reduced muscle tone and reflexes

intention tremor

tremor that is worse with movement and attenuates with rest

diencephalon substructures

• thalamus: sensorimotor relay station

• epithalamus: autonomic motor functions

• sub thalamus: motor functions

• hypothalamus: autonomin functions

thalamus

two lobes connected by mass intermedia

• GREAT relay station between cortical and subcortical structures

3 functions of the thalamus

1. channeling projections of sensation information (pain, taste, temperature, audition, and vision) to specific cortical areas

2. integration of sensorimotor information before the projection to the primary and premotor cortices

3. regulation of assertional cortex as well as cortically mediated cognitive functions

nuclei groups

• specific relay: from cortex

• sensory relay: somatosensory, hearing, vision

• motor really: basal ganglia and cerebellum

• association (multimodal): receive indirectly via other thalamic nuclei

• nonspecific: arousal and consciousness

thalamus afferents

• basal ganglia

• cerebellum

• sensory body

• sensory head and face

• sensory optic

• sensory hearing

thalamus efferents

• motor cortex

• prim motor cortex

• prim sensory cortex

• prim sensory cortex

• occipital lobe

• auditory cortex

dorsomedial nucleus

functions: reverberating circuits:

• development emotion, judgment, reason, memory, language, cognitive function, sensory and motor learning

afferents:

• prefrontal cortex, hippocampus, centromedianus nucleus, and orbital cortex

efferents:

• prefrontal and orbitofrontal cortices and limbic structures

lesions:

• memory loss (Wernicke-Korsakoff syndrome) and altered personality

• surgical lesions- amelioration of anxiety-related disorders

reticular nucleus

origin: part of the ventral thalamus that forms a capsule around the thalamus laterally

function: integration and regulation of thalamic neuronal activity

thalamic problems

• thalamic pain syndrome

  • hemiparesis/hemiplegia

  • dysesthesia (pain)

  • slight ataxia

  • cognition, speech, and language intact

• thalamic aphasia

  • fluent verbal output with semantic paraphasia

  • mild auditory comprehension issues

  • mild to normal repeating skills

hypothalamus

origin: in the pituitary gland

function:

• autonomic nervous system control

• metabolism

• water balance

• sleep-wake mechanism

• body temperature

• food intake regulation

• secondary sex characteristics

pituitary gland problems

Cushing disease:

• endocrine hormone disorder caused by tumor on pituitary gland

• causes high cortisol levels

• symptoms:

  • moon facies

  • emotional disturbances

  • hypertension

  • osteoporosis

  • buffalo hump

  • obesity

  • amenorrhea

  • muscle weakness

  • abdominal stripes

Acromegaly:

• “extreme largeness” caused by pituitary tumor

• causes the pituitary gland to produce too much human growth hormone

• symptoms:

  • large stature

  • large nose and jaw

  • large hands

  • hypertension

  • peripheral neuropathy

epithalamus

connects limbic system to forebrain and other parts

structures:

• pineal gland: produces melatonin

• habenula

• stria medullar is

functions: sleep-wake cycle, olfactory reflexes

sub thalamus

origin: under thalamus

function: connects basal ganglia to motor cortex; more related to basal ganglia than thalamus

damage to sub thalamus can cause hemiballismus

basal ganglia

structures:

• globus pallidus

  • external

  • internal

• putamen

• caudate nucleus

• sub thalamic nucleus

• substantia nigra

function: regulates complex motor functions

symptoms:

• hypokinetic: limited movement

  • rigidity

  • dystonia

  • bradykinesia

  • hypokinesia

  • resting tremor

• hyperkinetic- excessive movement

  • tremors

  • athetosis

  • chorea

  • ballismus

  • tics

Parkinson Disease (PD) (“shaking palsy”)

a progressive idiopathic neurological disease first described by Dr. James Parkinson in 1817

• caused by degeneration of midbrain’s substantia nigra and loss of dopamine to BG

Parkinson Disease (PD) facts (maybe extra credit)

• effects 20 million worldwide

• effects 1 million people in the US

• every year 600,000 people are diagnosed

• greater in males (1.2-1.5x)

• 41/100,000 get it in their 40s

• 1,900/100,000 get it 80s+

• may triple in 5 years

• costs the US $25 billion per year

• meds cost $2500 per year

• surgery costs $100,000

Parkinson Disease (PD) risk factors

• aging

• genetics

• environmental

Parkinson Disease (PD) symptoms

• rest tremor

• rights

• bradykinesia

• hypokinesia

• postural instability

• masked face

• shuffling gait

• hyperkinetic dysarthria

• reduced voice volume

• dysphagia

• depression/anxiety (40-50%)

• dementia (15-32%)

Parkinson Disease (PD) Treatment (medicine)

• levodopa/carbidopa meds

  • Sinemet

  • Parcopa

  • Stalevo

• dopamine agonists

  • mirapex

  • equip

  • parlodel

• anticholinergics

  • Artane

  • cognetine

• MAO_B inhibitors

  • eldepryl

  • zelapar

• COMT inhibitors

  • comtan

  • tasmar

Parkinson Disease treatment (surgical)

• deep brain stimulation (DBS): surgical insertion of a brain pacemaker ate stimulates the subthalamic nucleus, reducing PD limb rotor symptoms, detrimental effects speech

• pallidotomy: cells in the globes pallid us are selectively destroyed using a heated probe reducing the PD symptoms

hyperkinetic disorders

• Involuntary Movements: abnormal often bizarre, rhythmic or irregular and unpredictable, rapid or slow

• likely caused by too much dopamine

types of hyperkinetic disorders

• DYSKINESIA

  • abnormal, uncontrollable, involuntary movements. There are many different types of dyskinesia each with different causes

  • typically, it is associated with brain injury, antipsychotic medications (Tardive Dyskinesia), or the long-term use of levodopa (PD dyskinesia)

• TICS, TOURETTE’S

  • Rapid, stereotyped coordinated or patterned movements under partial voluntary control associated with irresistible urge to perform them

  • Tourette’s most common form

• CHOREA

  • Rapid, involuntary, purposeless movements of a body part. Present at rest, during sustained postures and voluntary movement

  • Inflammatory or infectious (Sydenham’s chorea, encephalitis) Degenerative (Huntington’s)

• Athetosis

  • Slow writhing purposeless movements that tend to flow into one another

  • Considered a major category of Cerebral Palsy

• Dystonia

  • Slow involuntary abnormal postures resulting from excessive co-contraction of antagonistic muscles

  • Can affect one body part, or generalized

ventricles

function:

• cerebral spinal fluid circulation and storage

• central nervous system protection during excessive accelerating and decelerating head movements

anatomy:

• 2 lateral ventricles, 1 third ventricle, 1 fourth ventricle

• each ventricle contains choroid plexus that produces cerebral spinal fluid

cereal spinal fluid (CSF)

• produced by choroid plexus

• origin:

  • brain ventricles

  • arachnoid space: brain and spinal cord

• functions:

  • protections

  • buoyancy

  • removes waste

  • transports nutrients and hormones

• production

  • 500mL is generated every day, 25 mL an hour

  • 125-150 mL is present at any one time

• reabsorption

  • CSF return to the vascular system by entering the dural venous sinuses via arachnoid granulations

hydrocephalus

“water on the brain”

• accumulation of CSF caused by an imbalance in production and drainage of fluid

• symptom: large head

meninges

a three layered membrane that surround the brain and spinal cord and act as a barrier

• dura matter: most outer layer

• arachnoid: middle layer

• pia mater: inner layer

dura mater

most outer layer

• strong thick and dense membrane

• surrounds the Venus channels carrying blood from brain to heart

• 3 septa:

  • falx cerebri: lies between the two hemispheres of the brain

  • tentorium cerebelli: gives a strong membranous roof over the cerebellum

  • falx cerebelli: projects downward from the tentorium cerebelli between the two cerebellar hemispheres

arachnoid

“middle layer”

• thin transparent membrane

• large number of filaments (arachnoid trabecular) pass from arachnoid through the subarachnoid space to blend with tissue of Pia mater

• arachnoid subspace contains blood vessels CSF

pia matter

“inner most layer”

• thin me brane that adheres to surface of brain and spinal cord (covering gyri and descending into suli)

• pierced by blood vessels that travel to the brain and spinal cord

meningitis

acute inflammation of the meninges

• causes:

  • bacterial causes: pneumonia, streptococcus, etc.

  • viral causes: echovirus, poliovirus, and coxsackie

• treatment

  • bacterial: antibiotics/antinflammatory products and vitamins; vaccine

  • viral: no specific treatment but antivirals are helpful

• complications

  • bacterial: hearing loss, brain damage, learning disability; untreated can be fatal; spreads through fluid contact from nose or mouth

  • viral: rare to have complications but can occur in patients with diseases or weak immune systems; spreads through saliva or stool

blood brain barrier (BBB)

• coordinated by physical, transport, and metabolic properties possessed by the endothelial cells that form the walls of the blood vessels

• Protects CNS from toxins, pathogens, inflammation, injury, and disease.

• Tightly regulates CNS homeostasis

• Provides an obstacle for drug delivery to the CNS

• Loss of some, or most, of these barrier properties during neurological diseases including stroke, multiple sclerosis (MS), brain traumas, and neurodegenerative disorders, is a major component of the pathology and progression of these diseases

The Circle of Willis

feeds the brain oxygen through:

• anterior cerebral artery

• middle cerebral artery

• posterior cerebral artery

cerebral vascular accident (CVA)

3 types:

• ischemic: occlusion of blood vessels

  • thrombosis: narrowing of arterial lumen due to focal and gradual accumulation of lipids, platelets, calcium deposits, & fatty particles

  • embolism: A broken plaque away from a thrombus; Blocking of distal and smaller arteries; Occurring during period of activity

  • transient ischemic attack (TIA): Temporary blood interruptions resolving in minutes to hours’ Occurring during inactivity; Indicative of larger stroke in progress; Sites of arterial bifurcation or at sites with injury

hemorrhage

ruptured blood vessel caused by high blood pressure

Arteriovenous Malformations (AVM)

congenital or fetal circulatory vascular malformation involving tangled dilated arteries or veins; blood bypasses brain tissue

ischemic CVA

ischemic penumbra idle cells die within 20 minutes without collateral circulation

• survival is 6-8 hours

hemorrhagic CVA

intraaxial: hemorrhage inside the brain

extraaxial: hemorrhage outside the brain

CVA symptoms

• Anterior Cerebral Artery:

  • Paralysis of legs & feet

  • Prefrontal lobe symptoms

    • reduced thinking, reasoning, & impaired planning

• Middle Cerebral Artery:

  • Contralateral hemiplegia

  • Impaired sensory functions

  • Aphasia (dominant hemisphere)

  • Temporal-visual-spatial deficit (non-dominant)

  • Homonymous hemianopia,

  • Involuntary movements (lenticulostriate arteries)

• Posterior Cerebral Artery:

  • Homonymous hemianopia

  • Pontine & cerebellar symptoms

  • Cortical blindness and visual agnosia (bilateral occipital lesions)

modifiable and non-modifiable risk factors of a stroke

modifiable: high blood pressure, heart diseases, diabetes, medications, smoking, drinking

non-modifiable: age, gender, family

stroke facts (maybe extra credit)

-4^th cause of death in U.S. 1^st cause of disability worldwide

-Prevalence in U.S.

roughly 3% of the adult population, ~7 million individuals

someone dies of a stroke every 4 minutes in the U.S.

-Incidence in U.S.:

Approximately 800,000 primary (first-time) or secondary (recurrent) strokes occur each year, majority being primary strokes (roughly 600,000)

  Rapidly increases with age, doubling for each decade after age 55

    In adults ages 35 to 44, incidence is 30 - 120 / 100,000 per year

    In adults ages 65 to 74, incidence is 670 - 970 / 100,000 per year

-Geography:

Higher rates in the Southeastern U.S. (the so-called “Stroke Belt”), especially along the coasts in Georgia and the Carolinas (so-called “Stroke Buckle”).

-Race/Ethnicity

2- to 4-fold higher among African Americans and occur at an earlier age

2-fold higher among Hispanics and occur at an earlier age

-Cost

The estimated direct and indirect cost of stroke for 2007 is $62.7 billion 

6.4 million stroke survivors living in the U.S.

stroke treatment

ischemic blood clot: clot busting drug given through vein to break up blood flow and maintain blood flow

• must be given within 3-6 hours of stroke to be helpful

• must have CT R/O hemorrhage or stroke could worsen

• types of blood thinners: heparin, warfarin, aspirin, clopidogrel

hemorrhage: surgery to remove blood around the brain and to fix damage blood vessels

waste removal: moves deoxygenated blood away from the brain

• removed through 4 sinuses in meninges

  • superior sagittal transverse

  • occipital sigmoid

• superficial and deep cerebral veins then remove waste

major layers of the cerebrum

surface gray matter: cerebral cortex, neuron somas

white matter: axons

deep gray matter: thalamus, basal ganglia

ventricles: 4 ventricles

features of cerebral cortex

• gyri

• sulci

• fissures (deep sulci)

  • longitudinal

  • central sulcus (Rolandic fissure)

  • lateral sulcus (Sylvian fissure)

cortical cellular organization

• Three major types of cells in cortex:

  • Pyramidal (with descending projections)

  • Granular/Satellite (with projections to association cortex)

  • Interneurons (local circuits to facilitate or inhibit information)

Brodmann’s Areas

frontal lobe

• primary motor cortex

  • 4

• premotor cortex

  • 6, 8

• cognitive association cortex

  • 9-11

• frontal association language cortex; Broca area

  • 44, 45

parietal lobe

• primary sensory cortex

  • 1, 2, 3

• somatosensory association cortex

  • 5, 7

• reading and writing

  • 41, 42

temporal lobe

• posterior association language cortex: Wernickes area

  • 22

• primary auditory cortex

  • 41, 42

occipital lobe

• primary visual cortex

  • 17

• visual association cortex

  • 18, 19

types of connection of Cortical White Matter

• association fibers: connect gyro in same hemisphere

• commissural fibers connect gyro in opposite hemispheres

• projection fibers: connect cerebrum with other parts of brain and spinal cord

association fibers

• Long Association Fibers:

  • Superior Longitudinal Fasciculus: Connects frontal, occipital, parietal, & temporal lobes

  • Inferior Longitudinal Fasciculus: Connects occipital lobe to temporal pole

  • Arcuate Fasciculus: Connects gyri in frontal lobe (Broca’s area) to temporal lobe (Wernicke’s area)

  • Uncinate Fasciculus: Connects frontal lobe to temporal lobe

  • Cingulum: Connects frontal & parietal lobes to para-hippocampal gyrus & adjacent temporal gyri

• Short Association Fibers: Connect adjacent gyri

commissural fibers

• Corpus Callosum

  • Large bundle of axons that connect the two hemispheres, except the Temporal lobe which are connected by the anterior commissure