HCR 240: Neurological System Part 1

what are the two main types of cells in nervous tissue

- neurons: excitable cells that tranmsit electrical or chemical information between other neurons or effector organs
- neuroglia: supporting cells that provide structural support, protection, and nutrition for the neurons and help support neurotransmission

what are the 4 parts of a neuron and describe them

- cell body: contains nucleus of cell
- axon: carry nerve impulses away from cell body
- dendrites: carry nerve impulses towards cell body
- myelin: lipid covering over axons to help transmit nerve impulse

how do nerves communicate

by generating and conducting electrical impulses (action potentials) which travel across the axon to synaptic cleft → at the synaptic cleft, this can spread the electrical impulse to post-synaptic neurons or it can trigger release of neurotransmitters

what happens in nerve injuries that result in cell death

- injuries to nervous tissue that result in cell death are permanent
- mature neurons do not divide and cannot make new neurons
- dead neurons will undergo liquefactive necrosis (turn into fluid or pus-filled cysts)

what happens in nerve injuries that do not result in cell death/neuron death

- neurons that are injured but not dead may slowly repair themselves through axonal reaction
- neurons may also form new connections with other neurons by neural plasticity

what is neural plasticity

neurons forming new connections with other neurons

what does the central nervous system vs peripheral nervous system consist of

- central nervous system: brain and spinal cord and contain relay neurons (interneurons)
- peripheral nervous system: cranial nerves, spinal nerves, and peripheral nerves that contain sensory neurons and motor neurons

what does the forebrain consist of

- frontal lobe: goal-orientated behavior, movement, short-term memory
- parietal lobe: sensory input
- temporal lobe: auditory, speech recognition, long term memory
- occipital lobe: vision

what does the midbrain consist of

- tectum: involved in certain reflex arcs
- cerebral aqueduct: part of cerebrospinal fluid ventricle system
- tegmentum: helps maintain homeostasis
- cerebral peduncles: connect cerebrum to brainstem

what does the hindbrain consist of

- cerebrum: balance, posture, fine motor movements
- pons: respiration
- medulla oblongata: respiration, heart rate, blood pressure, cough/gag swallowing

what is the spinal cord and afferent/efferent 

transmits long motor and sensory tracts that originate in brain and synapse will cell bodies iin the grey matter of spinal cord
- afferent is towards CNS
- efferent is away CNS

what are meninges

covering brain and spinal cord are 3 protective membranes: dura mater, arachnoid, and pia mater

what is meningitis

inflammation of the meninges

what is cerebrospinal fluid (CSF), what does it provide, and how is it produced and reabsorbed

clear and colorless fluid that functions to provided support and nutrients to brain tissue
- provides buoyancy and prevents brain from tugging on meninges, nerve roots, and blood vessels
- produced by choroid plexuses and reabsorbed through arachnoid villi

what is the peripheral nervous system

- 31 pairs of spinal nerves (name correlate with vertebral level from where they exit)
- contains 12 pairs of cranial nerves (olfactory, optic, oculomotor, trochlear, abducens, trigeminal, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal)
- contain peripheral nerve

what is autonomic nervous system

- contains cells from CNS and PNS
- coordinates to maintain steady state among internal organs
- includes sympathetic and parasympathetic

what is sympathetic (part of autonomic nervous system)

- fight or flight
- release of epinephrine and norepinephrine to vasodilate vessels to muscles and vasoconstrict vessels to viscera
- increases blood pressure and heart rate

what is parasympathetic (part of autonomic nervous system)

- rest and digest
- reduced heart rate and blood pressure, increased digestion and visceral function

what is nociception

- the process of harmful stimuli through the nervous system 
- nociception is a critical protective phenomenon to alert you about tissue injury

what are the phases of nociception

1. transduction
2. transmission
3. perception
4. modulation

what is transduction (phase 1 in nociception)

- tissue is damaged by exposure to chemical, mechanical, or thermal noxious stimuli
- stimuli is converted to electrophysiologic activity

what is transmission (2nd phase in nociception)

conduction of pain impulses into the dorsal horn of the spinal cord and eventually to the reticular formation, hypothalamus, thalamus, and limbic system

what is perception and modulation (3rd and 4th phase in nociception)

- perception: conscious awareness of pain
- modulation: process of increasing or decreasing transmission of pain signals throughout the nervous system (modulation is also why you require higher doses for medicine that you take repetitively)

what is acute nociception, how long is pain, and signs/symptoms

- protective mechanism to alert an individual to an injury or condition that is immediately harmful to the body
- pain <3 months
- signs/symptoms: tachycardia, hypertension, diaphoresis, dilated pupils, anxiety

what is chronic nociception

- lasts >3 months
- serves no protective purpose
- ? dysregulation of nociception medulation
- may cause behavioral and psychological changes like depression and anxiety

what are the different types of nociception

- somatic pain
- visceral pain
- referred pain
- neuropathic pain

what is somatic pain (a type of nocicpetion)

- pain is typically sharp and well localized but sometimes can be dull, throbbing, and poorly localized
- muscles, bones, joints, and skin
(*ex: paper cut - pain is sharp, in musculoskeleton, you will definitely know where the pain is)

what is visceral pain (a type of nocicpetion)

- pain is dull, aching, and poorly localized; oftentimes radiates or is referred
- organs and bodily cavities
(*neurons cannot tell exactly where the pain is)

what is referred pain (a type of nocicpetion)

pain that is felt distant to the point of origin due to convergence on the same spinal neurons
(*pain travels somewhere else)

what is neuropathic pain (a type of nocicpetion)

- nervous system dysfunction from improper modulation
- hyperalgia (mildly painful) and allodynia (stimuli becomes incredibly painful)

what is temperature regulation, the normal range and what controls it

- normal body temperature is achieved through precise balancing of heat production, heat conservation, and heat loss
- normal range is 36.2 to 37.7 C (97.2 to 99.9 F) and this process is controlled by hypothalamus, which receives input from peripheral thermoreceptors and triggers heat conservation/production or heat loss

what does the hypothalamus also trigger in temperature regulation and its physiological and pathological components

- hypothalamus may also trigger a fever (>100.5 F or 38 C)
- may be physiological: benefits of stimulating a fever is killing microorganisms, derives bacteria of food source
- may be pathological: trauma or stroke causing injury to hypothalamus

describe heat loss in temperature regulation (need to know)

- radiation (heat escaping through radiation like feeling heat through a computer)
- conduction: loss of heat through direct contact
- convection: loss of heat through gasses or liquids (movement of gas that take heat away)
- evaporation (like sweating)
- vasodilation (blood vessels get bigger)
- decreased muscle tone (muscles don’t want to do anything)
- increase pulmonary ventilation (dogs panting to cool down)
- voluntary mechanisms (staying in ac)

describe heat conservation/production in temperature regulation (need to know)

- vasoconstriction (blood vessel get smaller)
- skeletal muscle contraction: movement, shivering
- chemical thermogenesis (fight or flight, epinephrine or norepinephrine)
- chemical reactions of metabolism (thyroid hormone)
- voluntary mechanisms (jackets or staying indoors)

what is altered levels of consciousness (ALOC)

- consciousness requires arousal (wakefulness) and awareness (content of thought)
(*to be considered conscious, patient must be awake and not be confused/aware)

what bigger problems does altered levels of consciousness typically sign

- neurologic: stroke, seizures, trauma, tumor, intracranial infection, progressive neurological disease…
- metabolic: infection, organ failure, hypoglycemia, drug interactions or overdoses…
- psychogenic: underlying psychiatric illness

what are the different levels of altered consciousness

- confusion
- disorientation
- lethargy
- obtundation
- stupor
- light coma
- coma
- deep coma

what is confusion and disorientation of the levels of altered consciousness

- confusion: impaired judgement and decision making; cannot think rapidly or clearly (they act differently from how they normally are)
- disorientation: considered the beginning of loss of consciousness → test orientation to person, place, and time

what is lethargy and obtundation of the levels of altered consciousness

- lethargy: mild decrease in arousal; awakens upon light stimulation but limited spontaneous movement (you must put in effort to wake patient but patient will coorporate)
- obtundation: moderate decrease in arousal; falls asleep unless repeatedly stimulated (very drowsy and you must keep engaging with the patient)

what is stupor of the levels of altered consciousness

- stupor: severe decrease in arousal; may open eyes in response to vigorous or noxious stimulus (like a pinch or sternum rub)
(patient has consciousness but hard to stay in that level of consciousness)

what is light coma, coma, and deep coma of the levels of altered consciousness

- light coma: unresponsive but with purposeful movement upon stimulation; eyes may be closed or open (not conscious/awake but patient interacts if stimulated)
- coma: no response to external environment except upon noxious stimulation (require aggressive stimulus)
- deep coma: unresponsive with no response to any stimuli

what is acute encephalopathy and treatment

- general term encompassing acute confusional states
- patients present with sudden onset deficits in arousal and awareness - may have fluctuating symptoms of hallucinations, delusions, restlessness/agitation
- treatment: identifying cause, pharmacological and nonpharmacologic supportive measures

what are the different types of acute encephalopathy

- may be toxic metabolic: caused by disorders of body leading to disruptions in brain function (illicit drug use, overdose, drug interactions, metabolic disorders)
- may be neurological in origin: trauma, cerebral edema, meningitis/encephalitis, seizures, stroke

what is delirium

- can be considered a type of acute encephalopathy/acute confusional state
- reversible acute state of brain dysfunction (reversible since you just need to fix underlying issue)
(*nothing is wrong with brain, the problem is the body

what is delirium caused by and commonly seen in

- typically caused by metabolic disorders (drugs, dehydration, infection, sleep deprivation)
- more commonly seen in older adults but greatest risk factor is severity of illness (how sick are you?)

where is delirium often seen in and treatment

- often seen in the intensive care unit or post-operatively; tends to develop after 2-3 days
- treatment: supportive care including gentle reorientation, correction of disrupted sleep-wake cycle, review of medications, antipsychotics (*basically high quality nursing care)

what is the hallmark sign of delirium and what is hyperactive and hypoactive delirium

- hallmark sign is waxing and waning symptoms
- hyperactive delirium: agitation, aggression, restlessness
- hypoactive delirium: drowsiness, confusion, apathy

what is dementia, etiologies, and onset of symptoms

- progressive non-reversible failure of cerebral functions that causes impairment to arousal and awareness (patient will get worse)
- etiologies may include degeneration of neurons, compression of brain tissues, atherosclerosis of cerebral vessels, trauma, genetics…
- onset of symptoms is typically gradual and becomes worse with time but exact symptoms and progression pattern varies based on type

what is alzheimer’s disease

- the most common type of dementia
- full pathophysiology is unknown, risk increases with age and positive family history
- tends to have build up of cerebral amyloid protein plaques and tau protein bundles (these proteins building up causes neuron death)
- progresses from mild short-term memory deficits and culminates in a total loss of cognition and executive functions

what are seizures, causes, and symptoms

- uncontrolled electrical activity in the brain that leads to disruption of neuronal activity
- seizures may have many different causes and are typically symptoms of underlying disorder
- symptoms of seizures will depend on location of uncontrolled electrical activity and how far it spreads

what are the etiologies of seizures and what are recurrent seizures called

- etiologies: genetic disorders, metabolic disorders (drug intoxication or overdose, hypoglycemia, hypo or hypernatremia), brain tumor, trauma, infection, strokes, intracranial hemorrhage, or idiopathic 
- epilepsy is used to describe condition of recurrent seizures

how do you describe seizures based on location of abnormal electrical activity

- generalized: abnormal electrical activity encompasses both hemispheres of the brain; patient loses consciousness
- focal (partial): abnormal electrical activity is restricted to only one hemisphere; patient remains conscious

how do you describe seizures based on movement

- tonic-clonic: rhythmic periods of muscle contraction with increased muscle tone followed by relaxation
- other types of movement: tonic, atonic (patient lost tone and drops to floor), clonic (jerking movement), myoclonic (one particular muscle group is twitching)

what are atypical seizures

absence seizures (unique to pediatric), aggression (frontal lobe), sensory hallucinations (parietal), visual hallucinations (occipital lobe), auditory hallucinations (temporal lobe), aphasia (can’t talk)

what happens after a seizure

- many patients will enter a postictal state including confusion, drowsiness, headache, memory loss, weakness… as the brain tries to recover
- postictal states typically last several minutes to hours

what is status epilepticus and treatment

- seizures lasting 5 minutes or longer, or more than 1 seizure within a 5 minute period without the patient returning to baseline
- life-threatening condition, patient need emergency medical treatment 
- treatment: seizure abortive medications (benzodiazepines, anti-seizure medications), and supportive care

what is cerebral edema, what is it caused by, and symptoms

- swelling of brain tissue
- can be caused by traumatic brain injuries, intracranial lesion (tumors and strokes), or excessive CSF
- symptoms: agitation, confusion, drowsiness, coma

what can cerebral edema lead to

leads to increased intracranial pressure
- decreased cerebral perfusion and injury to surrounding brain tissue
- eventually brain herniation if left untreated

what is brain herniation of cerebral edema

- life threatening condition that requires emergency treatment
- pressure inside the skull causes part of brain to push against other structures

what is hydrocephalous, what can it lead to, and describe type of symptoms for acute and chronic hydrocephalous

- accumulation of cerebrospinal fluid in brain
- may lead to cerebral edema and increased intracranial pressure
- acute hydrocephalous may have acute symptoms similar to cerebral edema
- chronic hydrocephalous may have more mild symptoms

how do you do a neurological assessment (what do you ask)

neurological assessment for wakefulness and consciousness would include evaluation of mental status:
- is the patient awake → if the patient is not awake, can they awaken to stimulus → once awaken do they stay awake or do they require repeated stimulus
- is the patient orientated to person, place, and time? does the patient know why they are being evaluation
- how is the patient’s speech and understanding → does the patient follow commands, is the patient able to communicate, is the patient able to read/write

how do you test for a patient’s neurological status if they are in a stupor, light coma, coma, or deep coma

- check for wakefulness - some patients will awaken from comatose states
- check patterns of breathing 
- check eye opening
- evaluate motor response
- check cranial reflexes: pupillary reflex, corneal reflex, oculocephalic eyes, occulovestibular reflex, cough/gag reflex

what are Cheyne strokes respirations

abnormal breathing pattern characterized by periodic hyperventilation, hypoventilation, and then apnea

what is Cheyne strokes respirations caused by, stimulated by, and described as

- caused by bilateral injury to cerebral structures
- ventilation is only stimulated once PaCO2 is abnormally increased, slows down, and then stop once PaCO2 drops
- described as crescendo-decrescendo pattern

what can injury to pons or medulla cause in Cheyne strokes respirations

injury to pons or medulla oblongata may cause hyperventilation, apnea, and agonal breathing patterns

how do you evaluate for motor response

- purposeful movements: localization or withdrawal
- posturing: decorticate (flexion) or decerebrate (extension) (all neurologic injury)
- absent

what are the categories of purposeful movements in evaluating motor response

- localization: movement towards noxious stimuli
- withdrawal: movement away from noxious stimuli

what are pupillary reflex

pupillary changes can be an indication of brainstem function
- cranial nerves II (optic) and III (occulomotor)
- normal pupils should be symmetrical in size and shape and respond to light
- abnormal pupillary responses may be asymmetrical pupils, abnormal construction or dilation, or lack of response to light
- sudden changes to pupil shape and fixed/dilated pupils should be a red flag

what are occulocephalic reflex

- also called doll’s eyes reflex
- tests CN III, VI, VIII, and brainstem
- turn head from side to side and watch direction of pupils → normal if pupils stay focused on midline and not normal if pupils follow the same direction as the head is turned

what is occulovestibular reflex

- also called cold caloric testing
- tests CN III, VI, VIII, and brainstem
- cold water is inserted into ear canal while examiner watches direction of pupillary movements and nystagmus (patient MUST be uncounscious to do)
→ vestibulocochlear reflex if present if patient looks towards side of cold water and nystagmus is in opposite direction; it is absent if patient’s eyes do not move and there is no nystagmus

what is brain death

the complete and irreversible cessation of all brain activity including brainstem and cerebellum
- brain death means you are legally declaring the patient as dead and a death certificate is created

what is the strict diagnosis that must be met to be declared brain death

1. absence of confounding variables (no severe underlying metabolic disturbances, no CNS depressant drugs or paralytics, normal core body temperature, normal blood pressure)
2. clinical exam consistent with brain death (no movement, no sign of brainstem activity/absent cranial reflexes, no spontaneous respirations)
3. apnea tests consistent with brain death
4. ancillary tests as desired (EEG, transcranial doppler ultrasound, HMPOA SPECT)
5. is any criteria are not met, then brain death cannot be declared

what is brain death confusion

- spinal reflex arcs may still be present: Lazarus sign
- patient may continue to have cardiovascular function after they are declared brain dead → many patients become hemodynamically unstable and patients that “survive'“ are dependent on life-sustaining measures like ventilators, artificial nutrition, and certain medications from IV drips
- causes in which brain dead is incorrectly diagnosed are extremely rare and often sensationalized or incorrectly reported

is brain death the same as cerebral death

No, brain death is NOT the same as cerebral death
- cerebral death refers to the cessation of cerebral (telencephalon or forebrain) functioning
- in cerebral death, the midbrain and hindbrain are still intact
- patient is not considered legal death

what do patients typically progress to in cerebral death

- persistent vegetative state: spontaneous eye opening without regaining consciousness, cannot follow commands, cannot voluntarily move, dependent on artificial nutrition
- minimally conscious state: occasional brief periods of consciousness and limited movement

what is locked-in syndrome of cerebral death

- not brain death
- inability to communicate either through speech or body movement
- CN I-IV are typically preserved (able to blink and move eyes)
- conscious and cognitive function are intact
- caused by pontine injuries (central pontine myelinolysis or pontine infarcts)
(*you are conscious, awake, and know what’s happening but can’t interact with environment)