Exam 1

What are the types of ischemic stroke?

• Thrombus

• Embolism

• Low Systemic Perfusion Pressure

What is a thrombus ischemic stroke?

platelet adhesion and aggregation on plaques with resulting occlusion of artery

What is an embolism ischemic stroke?

composed bits of matter formed elsewhere & released then become lodged in the vessel creating occlusion

What is a low systemic perfusion pressure ischemic stroke?

low blood flow due to blood loss, heart failure, or systemic hypotension

What are the locations of the three types of ischemic strokes?

• Thrombus: on-site (branching/curves of arteries)

• Embolism: off-site (moves through bloodstream to brain)

• Low Systemic Perfusion Pressure: global damage

What are the causes of a thrombus ischemic stroke?

• Atherosclerosis

• Hypertension

What are the causes of an embolism ischemic stroke?

• Sudden occlusion

• Cardiac/vascular source

What are the causes of a low systemic perfusion pressure ischemic stroke?

• Blood loss

• Heart failure

• Systemic hypotension

What is a stroke?

Sudden loss of neuron function caused by interruption of blood flow to the brain

What causes an ischemic stroke?

Interruption of cerebral blood flow due to thrombus or embolus, leading to ischemia and infarction

What causes a hemorrhagic stroke?

Rupture of a blood vessel leading to bleeding into brain tissue (intracerebral or subarachnoid)

What is a TIA?

Temporary interruption of blood flow with no permanent infarction

• symptoms resolve within 24 hours (often <1 hr)

• Warning sign for stroke

What is the pathophysiology of an ischemic stroke?

• Clot blocks/impairs blood flow

• Brain deprived of oxygen/nutrients

• Transitional area around core has viable but metabolic lethargic cells (tissue can still function if blood flow restored) (Ischemic penumbra)

• Accumulation of fluid within brain (cerebral edema)

What are the causes of a hemorrhagic stroke?

• Trauma (injure cerebellar vessels)

• Rupture of cerebellar vessel

• Hypertension

What is the pathophysiology of hemorrhagic stroke?

• Bleeding → ↑ intracranial pressure (ICP)

• Mechanical compression of tissue

• Reduced perfusion to surrounding areas

• Herniation

What differentiates ischemic vs hemorrhagic stroke clinically?

• Ischemic: gradual or sudden focal deficits

• Hemorrhagic: often severe headache, rapid decline, ↑ ICP signs

Which type of stroke is most common?

Ischemic stroke

What populations are at highest risk for stroke?

• Older adults

• Individuals with hypertension

• Those with cardiovascular disease

• Smokers

• Diabetes patients

What sex differences exist in stroke epidemiology?

• Men: higher incidence earlier

• Women: higher lifetime risk (longer lifespan)

What are modifiable risk factors for stroke?

• Hypertension (MOST IMPORTANT)

• Smoking

• Diabetes

• Hyperlipidemia

• Obesity

• Sedentary lifestyle

• Atrial fibrillation

What are non-modifiable risk factors?

• Age

• Sex

• Genetics/family history

• Race/ethnicity

Why is hypertension the most important risk factor?

It contributes to both ischemic and hemorrhagic strokes via vessel damage

Which stroke type generally has the best prognosis?

TIA (no permanent damage)

Which stroke type has the worst prognosis?

Hemorrhagic stroke (higher mortality)

What factors influence stroke prognosis?

• Size/location of lesion

• Time to treatment

• Age

• Comorbidities

What is the primary diagnostic tool for stroke?

• CT scan (rules out hemorrhagic)

• MRI later (diagnosis of acute stroke - structural detail)

What is the medical management for an ischemic stroke?

• 3-4 hrs: tPa (save brain tissue)

• Mechanical thrombectomy (remove clot)

• Permissive HTN: <220/120 (increase blood flow to brain)

• 4+ hrs: supportive care only

What is the medical management for a hemorrhagic stroke?

• Balance BP

• Diuretics to reduce edema

• Often surgery

  • Aneurisms: coil or clip

  • Craniotomy: evacuate clots

What are the supportive cares for stroke?

• Oxygenation

• Maintain BP

• Restore/maintain electrolyte/fluid balance

• Maintain normal glucose levels

• Control intracranial pressures

When should PT initiate care after a stroke?

• Early mobility: within 24-72 hrs

• Wait 24 hrs to treat

Where are the locations of a traumatic hemorrhage?

• Epidural Hematoma

• Subdural Hematoma

• Subarachnoid Hemorrhage

• Intracerebral Hemorrhage

What is an epidural hematoma?

During trauma bleed between skull bone & periosteum

What is a subdural hematoma?

Tearing of bridging veins between brain surface & dural sinus (blood accumulates in dural space)

What is a subarachnoid hemorrhage?

Bleed into space between arachnoid & pia that surrounds the brain

What is the function of the dorsal horn?

• Initial processing center for sensory info received from the body

• Processes somatosensory information

• Houses sensory synapses & interneurons

What is the function of the ventral horn?

• Contains large MN & interneurons that send signals to muscle

• Controls voluntary & reflex movements (mediate motor function)

What is the function of the lateral horn?

• Houses autonomic neurons & interneurons

• Mediates sympathetic division of ANS (fight or flight)

• Controls involuntary processes (HR, blood vessel constriction)

What is the function of the dorsal and ventral roots?

• Dorsal: carry sensory info from the body to the brain

• Ventral: transmits motor commands from the brain (SC) to the body

• Come together to form spinal segmental nerve

What is the function of the dorsal column of the spinal cord?

• Carry sensory info signals to and from the brain

What is the function of the lateral column of the spinal cord?

• Carry motor and sensory info signals to and from the brain

What is the function of the ventral column of the spinal cord?

• Carry motor (primary) and sensory info signals to and from the brain

What is the function of the meninges of the CNS?

• Protect CNS from trauma by acting as a shock absorber

• Anchor brain to prevent it from moving in the skull

• Provide support system for blood vessels by delivering blood to CNS tissues, nerves, lymphatics, and cerebrospinal fluid

What are the three layers of meninges?

• Dura mater - outermost tough connective tissue layer

• Arachnoid mater - middle spider web-like layer

• Pia mater - thin covering on surface of CNS

What is the function of the lumbar enlargements of the SC?

• More cell bodies & interneurons located within

• Innervate legs (lower extremities)

What is the function of the cervical enlargements of the SC?

• Increased neurons cell bodies & interneurons

• Innervate upper extremities

What is the function of the conus medullaris?

• Cone-shaped sacral cord

• Serves as transition area between central & peripheral nervous systems

• Provide sensory/motor innervations to LE

• Give rise to spinal nerves to help w/ bowel/bladder function

What is the function of the cauda equina?

• Bundle of segmental nerves that provide motor/sensory innervation to LE & pelvic organs

• Contains filum terminale: cord that connects last bit of spinal cord to sacrum

  • keeps SC in place

What is a reflex?

A stereotyped, involuntary movement elicited by a peripheral stimulus that does not require conscious processing

Can reflexes be influenced by higher brain centers?

Yes—reflexes can be modulated or inhibited by higher centers (cortex, brainstem)

What defines a simple reflex?

• Monosynaptic or few synapses

• Occurs at one spinal level (segmental)

• Example: stretch reflex

What defines a complex reflex?

• Polysynaptic

• May involve multiple spinal segments (intersegmental) and/or supraspinal structures

• More functional and coordinated responses

What are the three categories of reflexes based on circuitry?

• Segmental spinal reflexes

• Intersegmental spinal reflexes

• Supraspinal reflexes

What characterizes a segmental spinal reflex?

All processing occurs within one spinal cord level

What characterizes an intersegmental reflex?

Involves multiple spinal cord segments, allowing coordinated multi-joint responses

What is an example of an intersegmental reflex?

Asymmetrical tonic neck reflex (ATNR)

What defines a supraspinal reflex?

Reflex that involves both spinal cord and higher brain centers

Example of a supraspinal reflex?

Startle reflex (Moro reflex in infants)

What inputs trigger the startle reflex?

• Auditory

• Tactile

• Vestibular

What is the circuitry of a segmental spinal reflex?

At a single spinal cord segment/level

What is the circuitry of a inter-segmental reflex?

Involves multiple segments of spinal cord

What is the circuitry of a supraspinal reflex?

Involves spinal cord & higher brain centers

What is the pathway of a supraspinal reflex?

Input → brainstem processing → spinal cord activation → motor response

What is the function of the flexion withdrawal reflex?

• Protective response

• Withdraws limb from noxious stimulus

What type of stimulus triggers the flexion withdrawal reflex?

Noxious stimulus via A-delta fibers

Describe the ipsilateral circuitry of the flexion withdrawal reflex.

• Excites flexor α-motor neurons

• Inhibits extensor α-motor neurons

• Uses interneurons

• Demonstrates reciprocal inhibition

What occurs simultaneously with the flexion withdrawal reflex?

Crossed extension reflex

What is the function of the crossed extension reflex?

Maintains postural stability and weight support on the opposite limb

Describe the contralateral circuitry of the crossed extension reflex

• Excites extensors

• Inhibits flexors

• Uses multiple interneurons

What is unusual about motor unit recruitment in the withdrawal reflex?

• Reversal of size principle

• Large motor neurons recruited first

What is response spread?

• Low stimulus → localized response

• High stimulus → spreads across joints or limbs

What triggers the extensor thrust reflex?

Pressure on foot (or palm) during weight bearing

What is another name for the extensor thrust reflex?

Positive support reflex

What stimulus triggers the contact placing response?

Contact on the dorsal surface of a limb

What is the contact placing response?

• Flex limb to clear obstacle

• Extend to place on surface

What is the response/functionality of the contact placing response?

• Lifts limb over obstacle (flexion)

• Places (extends) limb so that plantar surface contacts supporting surface

• Helps w/ obstacle negotiation during gait

What are the 3 primary embryonic brain vesicles/divisions?

• Prosencephalon (forebrain)

• Mesencephalon (midbrain)

• Rhombencephalon (hindbrain)

What does the prosencephalon develop into?

• Telencephalon → Cerebral cortex, basal ganglia, limbic system

• Diencephalon → Thalamus, hypothalamus

What does the mesencephalon become?

Midbrain (remains largely unchanged)

What does the rhombencephalon develop into?

• Metencephalon → Pons + cerebellum

• Myelencephalon → Medulla

What are the major adult brain divisions?

• Cerebrum

• Brainstem (midbrain, pons, medulla)

• Cerebellum

What are the 4 primary lobes of the cortex and their functions?

• Frontal → Motor control, judgment

• Parietal → Sensory processing

• Temporal → Hearing, memory

• Occipital → Vision

What is a gyrus?

A ridge on the cortex

What is a sulcus?

A shallow groove

What is a fissure?

A deep groove separating major regions

What does the central sulcus separate?

Frontal and parietal lobes

Function of the insular cortex?

• Emotion

• Autonomic control

• Taste (gustation)

What is the function of the thalamus?

Major sensory and motor relay center

What is the function of the hypothalamus?

• Homeostasis

• Endocrine control

• Hunger, thirst, reproduction

What is the function of the basal ganglia?

• Modulation of movement

• motor control

• executive function

What structures are part of the basal ganglia?

• Caudate

• Putamen

• Globus pallidus

• Substantia nigra

• Subthalamic nucleus

What is the function of the limbic system?

Emotion and memory

Key limbic structures and functions?

• Hippocampus → Memory formation

• Amygdala → Fear, emotion

• Cingulate gyrus → Emotional processing

What is the corpus callosum?

Commissural fiber tract connecting hemispheres

What are the 3 parts of the brainstem?

Midbrain, pons, medulla

Key structures in the midbrain?

• Superior colliculi → visual reflexes

• Inferior colliculi → auditory processing

• Substantia nigra → dopamine (motor control)

• Red nucleus → motor coordination

Main function of the pons?

• Relay to/from cerebellum

• Sleep, alertness (reticular formation)

Key functions of the medulla?

• Cardiovascular control

• Respiratory regulation

• Swallowing

What are the pyramids in the medulla?

Corticospinal tract fibers

What is the primary function of the cerebellum?

• Coordination of movement

• Error correction

• Balance and posture

What inputs does the cerebellum receive?

• Spinocerebellar tracts

• Motor cortex