Week 6: Neuro Flashcards
What are the major functions of each of the four major regions of the brain?
Frontal lobe: primary motor cortex
Parietal lobe: primary somatosensory cortex
Temporal: primary auditory cortex
Occipital: primary visual cortex + visual association cortex to interpret the meaning of visual experiences
What is the primary role of the primary motor cortex?
important for precise movement of hands, feet and phonation (speech)
What is the primary role of the somatosensory cortex?
perceives meaningfulness of integrated sensory inputs
What is the role of the hypothalamus?
controls homeostatic processes in the body - water balance, hunger-satiety cycle, metabolism, temperature
Major functions of the brain stem?
respiratory control center, cardiovascular control center, vasomotor center
What is the role of the reticular activating system (RAS)?
maintains behavioral arousal, consciousness, and motivation
What is the role of the cerebellum?
skeletal muscle activity; balance & equilibrium
How does bone function to protect the CNS?
brain and spinal cord are enclosed in the skull and vertebral column that offer protection
How do the meninges protect the CNS?
three connective tissue membranes that protect CNS structures
What are the three meningeal layers?
Dura mater: double layer membrane surrounding the brain
Arachnoid mater: threadlike extensions span subarachnoid space and attach to the pia mater
Pia mater: clings tightly to the surface of brain and spinal cord
How does CSF protect the CNS?
watery broth in ventricles that provides a cushion
How does the blood brain barrier protect the CNS?
provides separation between blood and neurons - relatively impermeable capillaries
Allows for passage of key nutrients: water, glucose, essential amino acids; excludes unwanted molecules
General organization of nerves in the spinal cord
cervical (C1-C5), brachial (C5-T1), thoracic (T1-T12), lumbar (L1-L4), sacral (L4-S5)
Where do we sample CSF?
L3/L4
Posterior region of the spinal cord contains which tract(s)?
ascending/sensory tracts
Anterolateral sections of the spinal cord contains which tract(s)?
ascending/sensory & descending/motor information
Definition, causes and symptoms of TBI
Head injury and subsequent damage to brain, possibly cranial nerves
Causes: falls, vehicular accidents, violence
Symptoms: dependent on if it is diffuse or local, the severity and the part of the brain involved
Definition and causes of cerebrovascular disease
vascular injuries such as stroke that may present with similar clinical manifestations as TBI
Causes: hypertension and hyperlipidemia
What is the role of the Circle of Willis?
protective circulation system that facilitates blood flow to the brain, allows collateral flow if a portion of the brain is disrupted
Define spinal cord injury
injuries to cranial nerves that often accompany TBIs
What conditions do seizures accompany?
many neuro conditions including TBIs and CVD
Define consciousness
state of awareness and orientation to surroundings, ability to respond to stimuli
determined by the RAS
What tool is used to determine level of consciousness?
Glasgow Coma Scale
Define concussion - injury severity and reversibility, symptoms (5)
caused by sudden movement of brain, most common form of TBI
Severity: Diffuse
Reversibility: Typically reversible
Symptoms: Associated with temporary LOC, change in resp, hypotension, bradycardia and amnesia
What is a contusion and is it reversible?
bruising of brain tissue, small petechial hemorrhages that leak into brain tissue
Reversibility: Partially reversible, depending on severity of injury
Define closed vs. open injury
Closed injury: skull intact
Open injury: skull fracture
Define primary vs. secondary brain injury
Primary brain injury: structural damage at the moment of trauma to neurons, glial cells, blood vessels
Secondary brain injury: consequence of response to injury: changes to blood flow, edema and subsequent ICP which can lead to cell death or herniation - worsens the primary injury
Definition and major consequence: hypoxia and ischemic injury
result from decreased oxygen availability in the brain tissue
Consequence: reduces availability of glucose and removal of waste products
Cerebral edema: definition and causes (2)
swelling of the brain due to accumulation of fluids
Causes: damage to BBB or inadequate waste removal
Definition and major consequence: increased ICP
results from fluid accumulation due to inflammatory or edematous processes
resultant reduction in tissue perfusion can lead to hypoxia and neuronal death, can lead to herniation (often into brain stem area)
Define epidural hemorrhage
arterial bleed into extradural space between skull and outermost brain layer
Define subdural hemorrhage, common causes
most common meningeal hemorrhage, blood accumulates between dura mater and arachnoid mater
causes: trauma, coagulopathy, alcoholism
Define intracerebral hemorrhage
disruption of cerebral vessels within the parenchyma resulting in neuro deficits, commonly found in frontal and temporal lobes
Define intracerebral hematoma
focal injury involving collection of blood in or around the brain, often caused by hemorrhage
Define transient ischemic attacks, what they are a risk factor for, the causes and s/s (4)
neuro events due to ischemia that are short-lived and resolve completely
Risk factor for stroke
Causes: embolus or thrombus involving any cerebral artery
S/s: transient episodes of contralateral weakness, sensory deficits, visual impairments, aphasia
Define stroke, causes
sudden focal neuro deficit due to vascular disorder. Nontraumatic disruption of blood flow
causes: occlusion of cerebral arteries by ischemia or hemorrhage
Define ischemic stroke
results from obstructed blood flow or systemic hypoperfusion, leading to ischemia, potentially irreversible necrotic process and cerebral infarction
Define hemorrhagic stroke
results from intracranial hemorrhage, deep in the parenchyma or near surface of the brain, often has HTN as underlying cause
Define aneurysm, a defect in ____ can lead to it, major consequence
localized dilation in a blood vessel wall that can rupture and lead to hemorrhage
- tunica media
- rupture can cause aneurysmal subarachnoid hemorrhage, s/s range from mild headache to coma and death
Causes and symptoms of spinal cord injury
Causes: any injury caused by trauma - vehicle accidents, falls, sports injuries, violence
Symptoms: vary depending on site of injury and if nerve roots are damaged
What is the result of a spinal cord transection?
loss of motor, sensory, reflex and autonomic function below the level of injury; can be complete or partial
Differentiate between primary vs. secondary spinal cord injury
Primary SCI: occurs at time of accident and is irreversible
Secondary SCI: follows primary injury and spreads damage
Define meningitis, what are common causes (specific strains)?
infection of the meninges
bacteria: strep pneumonia, Neisseria meningitidis, hameophilus influenzae
Virus: enteroviruses, coxsackie virus, adenovirus, herpes, HIV, Epstein Barr virus, CMV
Define encephalitis, what are common causes (7)
infection and inflammation of brain tissue or spinal cord
Causes: equine encephalitis, west nile, herpes, HIV, cytomegalovirus, rabies, prion diseases (mad cow disease)
Define Parkinson Disease, what is the common cause and s/s
degenerative disease of CNS characterized by movement disorder
Cause: death of dopamine-producing cells in substantia nigra of the basal ganglia
S/s: movement related symptoms (tremor, bradykinesia, rigidity, postural instability), neuropsychiatric sx (dementia & depression)
What is the characteristic of cells death in Parkinson Disease?
Development of alpha-synuclein protein in the brain (Lewy bodies)
Define MS, s/s (5), Tx
autoimmune attack on myelin of CNS neurons that causes formation of plaques and destruction of myelin
S/S: visual changes, muscle weakness, loss of coordination, numbness, mild cognitive impairments
Tx: anti-inflammatory agents (corticosteroids)
Define ALS, S/S, Tx
condition characterized by loss of motor neurons
S/S: Progressive weakness and muscle wasting, death usually within 5 years of dx
Tx: supportive measures only - drugs (riluzole) can suppress glutamate and ameliorate sx
What is usually the cause of mortality in ALS?
Failure of respiratory muscles
What are two pathologic associations with ALS?
May involve excess glutamate in synapses
Mutations in superoxide dismutase gene associated, suggesting oxidative stress may contribute to cell death
What are the basic divisions of the PNS?
Afferent (sensory): detects, transmits and processes environmental information from internal/external sources through a variety of receptors
Efferent (motor): initiates voluntary and involuntary movement
What are the levels of afferent neurons?
Sensory unit: afferent neuron and all receptors that send information along it
Dermatome: area of skin supplied by a single spinal nerve transmitting to a dorsal root ganglion and spinal cord segment
Receptive field: area that sends information along a single afferent neuron
Which column do myelinated fibers travel along? Is it ipsilateral or contralateral? Where does it cross?
- Dorsal columns
- ipsilateral
- medulla
Which column do unmyelinated fibers travel along? Is it ipsilateral or contralateral? Where does it cross?
- anterolateral system
- contralateral
- spinal cord at point of entry
What sensory information is carried by fast vs. slow myelinated fibers?
Fast: touch, proprioception, pressure
Slow: touch, temperature, fast pain
What sensory information is carried by unmyelinated fibers?
Slow pain, hot and cold, itch
What are the basic steps in control of voluntary movement? (4)
- Commands initiated in association cortex
- Commands relayed to sensorimotor cortex, cerebellum, and subcortical nuclei
- Initial command broken down into series of smaller motor programs
- Motor programs transmitted through descending motor pathways to carry out commands
Define pyramidal tracts, what are characteristics of diseases of these tracts?
originate in the sensorimotor cortex of the cerebral cortex, descend through the basal ganglia and brain stem, cross or remain uncrossed at the medulla from where they descend the spinal cord
Diseases (eg. Stroke) characterized by spasticity and paralysis
Define extrapyramidal tracts, what are characteristics of diseases of these tracts?
remaining tracts that do not transverse the brainstem
Diseases (eg. Parkinson) result in involuntary movements, muscle rigidity, immobility without paralysis
What is the major role of the ANS?
governs body processes without conscious effort
What are the roles of the two divisions of the ANS?
Sympathetic: mobilizes the body
Parasympathetic: conserves body
Which neurotransmitters are adrenergic?
epinephrine, norepinephrine
Which neurons release norepinephrine?
most sympathetic postganglionic neurons
Which neurotransmitter is cholinergic?
acetylcholine
Which neurons release acetylcholine?
preganglionic neurons
parasympathetic postganglionic neurons
What is the general response of adrenergic receptors?
Alpha-adrenergic: vasoconstriction of blood vessels in skin and viscera, not in airway smooth muscle
Beta-adrenergic: vasodilation of blood vessels in skeletal muscle, increase heart rate and contractility, relaxation of airway smooth muscle, blocked by propranolol
Define pain
unpleasant sensory and emotional experience associated with actual or potential tissue damage
Define nociceptive pain, causes
cutaneous, deep somatic or visceral origins of pain
Causes: mechanical, thermal or chemical damage - trauma, burns, infection, exposure to toxins
Which substance is released from nerve terminals? What is it’s major role?
Substance P
sensitizes nociceptors by causing release of histamine and serotonin from platelets and mast cells that contribute to inflammation
Describe fast pain, which fibers carry it, localization, cutaneous or visceral?
prickling, stabbing
Carried on A-delta fibers (myelinated)
Good localization
Cutaneous: fast pain on the surface
Describe slow pain, which fibers carry it, localization, cutaneous or visceral?
dull ache, burning
Carried by C fibers (unmyelinated)
Poor localization
Visceral: slow pain (chest pain due to myocardial infarction
Define deep somatic pain
fast and slow pain (arthritis or sprained ankle)
Define referred pain
localized to place other than the origin of the pain
Describe Brown-Sequard Syndrome, S/S
SCI that alters functions of the PNS
S/S: loss of voluntary motor function from the corticospinal tract, proprioception loss from ipsilateral side of the body, contralateral loss of pain and temperature sensations from the lateral spinothalamic tracts for all levels below the lesion
Describe Guillan-Barre Syndrome, S/S, causes, consequences
infection that initiates autoimmune destruction of peripheral nerves
s/s: ascending paralysis, weakness in extremities migrating toward the trunk, altered sensations, pain, dysfunction of ANS
Causes: infection with bacteria such as campylobacter jejuni or CMV
Consequences: damage to myelin and can result in paralysis as well as sensory and autonomic disturbances
