Pathophysiology - Exam 3

cell body

• also called soma

• filled with cytoplasm and organelles that support the metabolic demands of the cell

dendrites

multiple branched extensions of the cell body that transmit impulses to the cell body

axon

carries impulses away from the cell body

sensory/afferent neurons

carry impulses from receptors in the periphery to the CNS

motor/efferent neurons

carry signals away from the brain and spinal cord to targets in the body that regulate activity

interneuron

• most abundant neuron type

• transmit signals between afferent and efferent neurons

supporting cells

• also called neuroglia

• oligodedrocytes

  • form myelin segments around axons in CNS increasing speed of neuron production

• schwann celles

  • produce myelin on long, single axons in the PNS

• nodes of ranvier

  • rich in sodium channels that assist and promote movement of nerve impulses over long distances

saltatory conduction

nerve impulses travel in a stepwise fashion (node to node)

membrane potential

difference in electrical charge between the inside and outside of the cell

action potential

electrical current that travels along the entire neuron

• allows neurons to communicate

• regulated by membrane potential

• three components → resting membrane potential,  depolarization phase, repolarization phase

resting membrane potential

• membrane potential or state of tension inside the plasma membrane

• nerve cell at rest

depolarization

• rapid movement of sodium into cell through sodium channels in the plasma membrane

• this generates an electrical impulse

• triggers the release of neurotransmitters

repolarization

• initiated by the flow of potassium ions out of the cell

• returns the cell to resting membrane potential

electrical impulse

• passed by current-carrying ions through gap junctions

• fast, direct, and multidirectional mode of transmission

• ex. impulses leading to cardiac contractions

chemical impulses

• impulses stimulated by neurotransmitters

• unidirectional, one-way communication between neurons

neural communication

• neurotransmitters released into the synaptic cleft MUST bind to receptors on the postsynaptic neuron in order to generate an impulse

• if there is an interruption in this process, we may see:

  • reuptake of the neurotransmitter into the presynaptic neuron

  • diffusion of the neurotransmitter out of the synaptic cleft

  • enzymatic breakdown of neurotransmitter in the cleft

  • postsynaptic receptor alteration that imparis the binding process

neural changes with aging

• decrease in number of neurons

• enlargement of ventricle system

• widening of sulci

• decreased brain volume and weight

• sensory changes (cataract development, loss of focus, diminished hearing, smell, and taste)

• decrease in myelin (altered impulses and sensations)

frontal lobe

involved with reasoning, planning, speech, and movement

parietal lobe

involved with conscious perception of touch, pressure, temperature, and pain

temporal lobe

involved with conscious perception of auditory and olfactory stimuli

occipital lobe

involved with vision

hemispheres

these communicate with each other through a bundle of nerve fibers known as the corpus callosum

spinal cord

• the primary pathway for message or impulse communication from the periphery and the brain

• made of white matter (axons and dendrites) and grey matter (cell bodies)

pyramidal motor system

• extends from the sensorimotor areas of the brain to the motor neurons of the ventral horn of the spinal cord

• controls voluntary movement

extrapyramidal system

• functions of this system are associated with the basal ganglia (a brain structure that helps control voluntary movement and establish posture)

• fine-tunes and stabilizes movement, reducing erratic motions and maintain muscle tone and stability

peripheral nervous system

includes somatic and autonomic

somatic

• motor and sensory impulses between the central nervous system and the periphery

• primary functions: coordination of body movement, reception of external stimuli, regulation of activities under conscious control

• components: cranial nerves (I-XII), spinal nerves

autonomic

• controls the involuntary (automatic) functions of organs

• all internal organs are supplied with nerves from the autonomic nervous system (ANS)

• two divisions:

  • sympathetic

  • parasympathetic

sympathetic

fight or flight

• increase HR, contractility, BP, and RR

• bronchial smooth muscle relaxation

• vascular smooth muscle constriction

• decreased bladder tone and decreased peristalsis of GI smooth muscle

• constriction of anal and urinary sphincters

parasympathetic

rest and digest

• decreased HR, contractility, velocity of conduction, BP, and RR

• bronchial smooth muscle constriction

• vascular smooth muscle relaxation

• increased constriction of bladder and peristalsis of GI smooth muscle

• relaxation of anal and bladder sphincter

reflex arc

• withdrawal reflexes (ex. hot stove)

• represents the process of receiving and interpreting stimuli leading to a stimulated response

• illustrates communication between various segments of the nervous system, specifically between the receptor, spinal cord, and target organ

cerebrovascular circulation

• supplies oxygen and nutrients for optimal metabolism and functioning

• arterial supply to the brain includes vertebral, basilar, and carotid arteries

• drainage occurs via the jugular veins

• preferred energy source of the brain is glucose

blood-brain barrier

• protects the brain from foreign substances, hormones, and neurotransmitters in the systemic circulation,

• compromised by tumors or meningitis

cerebrospinal fluid

• CSF

• provides a cushion for the brain structures, reduces pressure on brain structures, removes harmful substances, transports hormones to remote sites in the brain

• too much leads to hydrocephalus

meninges

three protective membranes that surround the CSF

CNS injuries

1. trauma

2. ischemia

3. excitatory response

4. pressure

trauma

• traumatic brain injury (TBI)

  • ex. falls, motor vehicle accident, head trauma

• traumatic spinal injury

  • ex. motor vehicle accident, falls, violence, recreational injury

ischemia

• impaired perfusion to neurologic tissue resulting in impaired oxygenation

• impaired blood flow for longer than a few minutes results in issue infarction

• ex. thrombosis (stroke)

excitatory response

• prolonged action potential that stimulates damage to neurons

• may result from the inability to meet the metabolic demands of the cells

• can happen with prolonged ischemia

• ex. seizure

pressure

• increased intracranial pressure (ICP) may result in neuronal injury and cell death

  • S&S of ICP: headache, vomiting, papilledema, mental deterioration

• ex. excessive CSF volume, cerebral edema, or space-occupying lesions

• brain herniation is a major concern

motor dysfunction

• may result from peripheral nerve injury that alters reflex circuits

• causes:

  • excessive inhibitory or excitability response in nervous tissue that control functions such as coordination and proprioceptions

  • neurotransmitters excess or deficiency

  • altered neural transmission

ataxia

inability to coordinate movement

athetosis

• involuntary movements of flexion and extension

• pronation and supination of hands, feet, and toes

• slow, writhing-type movements

ballismus

jerking, swinging, sweeping motions of the proximal limbs

brady/hypokinesia

decrease in spontaneity and movement, slow movement

chorea

• irregular, spasmodic, involuntary movements of the limbs or facial muscles

• often accompanied by hypotonia

cogwheel rigidity

• resistance to movement

• rigidity decreasing to stiffness after movement begins

dystonia

• abnormal tonicity

• difficulty maintaining posture

hyperkinesis

excessive motor activity

tic

• repeated, habitual muscle contractions

• movements that can be voluntarily suppressed for short period only

tremor

• oscillating, repetitive movements of whole muscles

• irregular, involuntary contractions of the opposing muscle

processes of neural injury

• chomatolysis

  • swelling of a neuron because of injury

• atrophy

  • decrease in neuron size

• neuronophagia

  • phagocytosis and inflammatory responses caused by a dead neuron damaging neighboring cells

• intraneuronal inclusions

  • distinctive structures formed in the nucleus or cytoplasm

emotions

• feelings

• fluid

• quickly changing

• moving

mood

• internal subjective psychological state

• falls between emotions and temperament

temperament

• personality

• stable representation of outlook

• less likely to change

hypothalamus

involved in autonomic control in emotions

prefrontal cortex

involved in judgement, decision making

amygdala

involved in emotionally charged memories and senses danger

hippocampus

involved in long-term memories

anterior cingulate cortex

involved in empathy and impulse

cingulate gyrus

involved in emotional memories

limbic system

circuit that connects one’s cognitive activity, emotions, and behavior

neurotransmitters

chemical messengers for mood regulation

ex. serotonin, dopamine, norepinephrine

attention

this is both a cognitive process and a behavior that involves different areas of the brain (RAS control, frontal lobe, basal ganglia)

five types of attention

• focused → noticing and responding to one specific stimulus

• sustained → prolonged concentration with vigilance over time

• selective → noticing and responding to a stimulus while filtering distractions

• alternating → moving between tasks having different cognitive requirements

• divided → responding simultaneously to multiple tasks or demands

behavior

• how people respond and act in a given situation

• regulated by the frontal lobe which integrates the following aspects of behavior

  • personality, perception, planning, self-awareness, judgement, mood, attention, memory, motivation, sexuality, expressive language, social/emotional intelligence

traumatic brain injury

• TBI

• can lead to prefrontal cortex injury

  • impacts social responsibility, concentration, abstract thinking, problem solving, emotional response

• can damage the amygdala

  • fear, aggression, social intelligence

dopamine

• low: apathy, inattentiveness, motor deficits (bradykinesia)

  • low in parkinson’s

• high: agitation, restlessness, psychosis

  • high in schizophrenia

serotonin

• low: anxiety, depression, obsessions, compulsions

psychotherapy

• conducted with a mental health professional to explore thoughts, feelings, and behaviors

• methods include:

  • CBT, exposure therapy, eye movement desensitization and reprocessing (EMDR)

pharmacotherapy

• drug therapy to manage symptoms of mood, attention, and behavioral disorders

  • ex. antidepressants, antipsychotics, stimulants

counseling

• facilitates stress reduction, lifestyle changes, and access to community resources

support groups

• individual or family-based groups offering:

  • shared experiences

  • a common goal for recovery or coping

  • spiritual or faith-based support

somatosensory processing

• this depends on recognition, identification, and interpretation of stimuli and the receptors ability to detect an impulse

• primary processing is in the thalamus

• final interpretation is in the somatosensory cortex

acuity

the ability to locate the site where the stimulus was initiated

5 types of stimulus receptors

1. mechano → mechanical forces (vibration, acceleration, sound)

2. thermo → temperature

3. nociceptors → pain, itch

4. photo → light, vision

5. chemo → taste, smell

first order neuron

communicate sensory information from the periphery to the CNS

second order neuron

relay sensory information from reflex pathways and sensory pathways to the thalamus

third order neurons

communicate sensory information from the thalamus to the primary somatosensory cortex

nociceptive pain

• pain that originate outside of the nervous system (skin, muscles, joints, organs)

• often responds to NSAIDs/opioids

neurogenic pain

• pain that originates within the nervous system (nerve injury, demyelination, abnormal firing)

• often requires anticonvulsants/antidepressants

strabismus

• misalignment/crossed eyes

• treatment: glasses, patch, surgery

amblyopia

• “lazy eye“

• reduced vision in one eye

• treatment: patching stronger eye, corrective lenses, sometimes surgery

diplopia

• double vision from muscle or nerve imbalance

• treatment: prisms, patching, therapy, surgery

nystagmus

• involuntary oscillation of eyes (may be from vestibular/neurologic disorder)

• treatment: address underlying cause, sometimes medication or surgery

lens

• bends to focus light on the retina

• responsible for fine-tuning eye focus

• alterations:

  • cataracts (clouding from protein clumping, often age-related) → blurry vision, glare sensitivity, decreased acuity

retina

• contains rods (dim/nighttime vision) and cones (color, bright/daytime vision, acuity) to convert light to neural signals

• alterations

  • macular degeneration (MD) → central vision loss, difficulty reading/recognizing faces

  • diabetic retinopathy → vision loss, hemorrhage

  • color blindness

viral conjunctivitis

• usually affects only one eye

• associated with excessive eye watering and a small amount of discharge

bacterial conjunctivitis

• usually affects both eyes

• associated with heavy discharge

allergic conjunctivitis

• usually affects both eyes

• associated with itching, redness, and excessive tearing

sensorineural hearing loss

often permanent, resulting from disease, trauma, or genetic inheritance of a defect in the cochlear nerve cells (damage to the little hairs)

conductive hearing loss

localized to the outer or middle ear, and it may be temporary or permanent

mixed hearing loss

a combination of both sensorineural and conductive hearing loss

central auditory processing disorder

a disorder involving altered auditory signal processing in the brain

validate patient symptoms

nurses who do this promote trust, adherence, and reduce stigma

eustachian tubes

children are at higher risk of developing otitis media (ear infections) because this anatomical structure is shorter, straighter, and more horizontal, making drainage poor

pain

this symptom of otitis media is due to increased pressure on the tympanic membrane

fever

this symptom of otitis media is due to a systemic infection response

hearing loss

this symptom of otitis media is due to fluid blocking sound conduction and hair cell damage from pressure

complications of otitis media

tympanic membrane rupture, mastoiditis, meningitis, permanent hearing loss