Brain expanded

Limbic system: definition and main structures

Regulates emotion, memory, appetite, autonomic, and visceral processes

includes hypothalamus, amygdala, hippocampus, nucleus accumbens, and olfactory tubercle

Hypothalamus: role in the limbic system

Where the emotive brain and cognitive brain operate together (reasoning behind the emotions)

Nucleus accumbens and olfactory tubercle

Reward circuit; called the "limbic-motor interface"; influence dopamine levels

Amygdala: what does it regulate and lobe?

processing emotions (anxiety, aggression,fear) between prefrontal temporal and hypothalamus

Hippocampus: role and damage results in and lobe?

memory and decision making

Impaired short-term memory and inability to form new memories (anterograde amnesia)

Temporal

Three phases of memory

Registration, storage, and retrieval

Cerebellum: key anatomy

Inferior to the occipital lobes; hemispheres divided by the vermis; outer gray matter is the cerebellar cortex, inner white matter is the arbor vitae

Cerebellum: side controlled and neuron share

Controls the ipsilateral side; holds 80% of the brain's neurons

Cerebellum and basal ganglia: input and output

Receive input from the motor cortex and project back to the cortex via the thalamus

Cerebellum: functions

Regulation of movement, fine motor movements, coordination, balance and position sense, and emotions

Cerebellar arteries: origin and supply

Superior, anterior, posterior

Superior cerebellar artery (off basilar) supplies midbrain

anterior interior cerebellar artery (off basilar) supplies pons

posterior inferior cerebellar body (off vertebral) supplies medulla

PICA: key facts

Largest and most tortuous branch of the vertebral artery; supplies the lateral medulla

PICA occlusion causes

Wallenberg syndrome (lateral medullary syndrome); most common posterior circulation stroke

Crania nerve related symptoms

Cerebellar venous drainage

Superior and inferior cerebellar veins drain into sinuses, which drain into the internal jugular vein

Ataxia

Disturbance of voluntary movements

Dysdiadochokinesia

Impaired rapidly alternating movements

Nystagmus

Rhythmical oscillation of the eyes ("ataxia of the eyes")

Cerebellar dysarthria

Slurred speech with syllables separated by long pauses ("scanning speech")

Intention tremor

shaking

Hypotonia

Muscles lose resistance to palpation

Dysmetria

Inability to judge distance (finger to nose)

Pronator drift

With eyes closed, hand drifts down into pronation; indicates cerebrospinal tract involvement

Midbrain: cranial nerves

location of CN III and IV

Pons: cranial nerves and clinical significance

Origin of CN V through VIII; site of infarction, tumors, or demyelinating disorders

Medulla oblongata: key facts

Most inferior part, connects to spinal cord; cardiovascular-respiratory regulation; origin of CN IX through XII; motor neurons cross here

Midbrain: functions

Most eye movements, processing vision and hearing, dopamine (substantia nigra)

Pons: function

Sleep-wake cycle

Medulla: functions

Coughing, sneezing, swallowing, vomiting, balance; pyramidal decussation (motor crossover); vagal trigone

Reticular activating system

Brainstem network projecting to the hypothalamus and limbic system and thalamus; filters out unimportant information

Reticular activating system: clinical links

Concussion; addiction (overactive arousal); PTSD (overactive startle)

Cerebellopontine angle: location and contents

Between pons, cerebellum, houses CN V, VI, VII, VIII and Anterior inferior cerebellar artery

Cerebellopontine angle syndrome

Speech impediments, unilateral hearing loss, disequilibrium, dizziness, tremor

Brainstem lesions: symptoms

Insomnia, difficulty breathing, HR and BP dysregulation, nausea, dizziness, dysphagia, CN disorders; can lead to coma and death

Cerebral perfusion pressure and what regulates?

60 to 150 mmHg

BP, nervous, blood gas info

Hypoperfusion vs hyperperfusion

Hypoperfusion causes ischemic stroke; (low)

Hyperperfusion causes hemorrhagic stroke, seizures, headaches, encephalopathy (high)

Two sources of blood to the brain

which is anterior / posterior and branch off of?

Internal carotids (anterior; off common carotids)

vertebrals (posterior; off subclavians)

Internal carotid artery: supply and branches

Supplies cortex, basal ganglia, thalamus, internal capsule; gives posterior communicating,

then splits into anterior cerebral artery and middle cerebral artery

Middle cerebral artery: key facts

Largest terminal branch of the ICA; most commonly affected vessel

MCA M1and M2 superior vs inferior trunk

Beginning branch

Superior trunk lesion causes Broca's aphasia (commonly left); (frontal lobe)

inferior trunk lesion causes Wernicke's aphasia (temporal)

What happens if main branch of MCA is impacted?

contralateral paralysis of arms, legs, and face

Right MCA stroke

Hemineglect with anosognosia, apraxia, and hemispatial neglect

Basilar artery: formation

Left and right vertebrals join at the level of the pons (vertebrobasilar system)

Where does PICA branch off?

Superior region of the vertebral arteries

Where does AICA branch off?

At the junction where the vertebral arteries join to form the basilar artery

Where does the SCA branch off?

Just before the basilar artery splits into the posterior cerebral arteries

Circle of Willis

Anastomosis joining anterior and posterior circulation at the brain's base; Posterior communicating artery bridges ICA and PCA; preserves supply if occlusion occurs

Ischemia vs hemorrhage

Ischemia is loss of supply (hypotension, thrombus, emboli)

hemorrhage is blood loss from vessel (AVM, aneurysm, trauma, hypertension)

ACA stroke

Leg affected more than arm or face; minimal sensory changes

MCA stroke

Face and arm affected more than leg; sensory loss; most common type

PCA stroke

Acute vision loss or visual field deficits, confusion, double vision, dizziness, memory loss

Cerebral venous system: key fact

Drains into internal jugulars veins

Cortical bridging veins what are they and causes?

between skull and brain to help drainage meninges

Rupture causes subdural hematoma: headache, confusion, unilateral weakness, speech changes, nausea, dizziness

Cavernous sinus: contents and location

CN III, IV, V1, V2, VI, and internal carotid artery

deep in brain

Meninges: layers and spaces from bone inward and function

Bony border, Epidural space, dura, subdural space, arachnoid, subarachnoid space (CSF), pia

Cover CNS to protect brain and spinal cord

Epidural space

Arteries and veins run here; only exists if something is wrong

CSF: functions and composition

Nourishment, shock absorption, waste removal; 99% water

CSF: production

80% by choroid plexus (mainly lateral ventricles); about 500 mL per day, 150 mL normal volume

CSF flow pathway

Lateral ventricle, then third, then fourth, then surface of brain and spinal cord (subarachnoid), then venous system

CSF leak

80% from craniofacial trauma; positional headache, neck stiffness, nausea; treated with epidural blood patch, surgery, or caffeine

Lumbar puncture

Removes CSF for testing; done at L3/L4 or L4/L5 into the subarachnoid space

ANS: three divisions

Sympathetic (fight, flight, freeze), parasympathetic (rest and digest), enteric (independent, digestive)

Sympathetic nervous system

Originates T1 to L3; increases HR, respiration, blood to muscles, glucose; dilates pupils; slows GI

Parasympathetic nervous system origin and functions

Originates cranial and sacral CN III, VII, IX, X and S2 to S4; lowers HR, BP, and RR; constricts pupils; increases digestion