brainstem ----> end of brain & cranial nerves

brainstem

connects cerebrum, diencephalon, and cerebellum to spinal cord

contains ascending and descending tracts

contains autonomic nuclei, nuclei of cranial nerves, and reflex centers

what are the parts of the brainstem top to bottom

midbrain

pons

medulla oblongata

components of the midbrain

cerebral peduncles

superior cerebellar peduncles

medial lemniscus

substantia nigra

tegmentum

cerebral aqueduct

tectum

cerebral peduncles

carry voluntary motor commands from primary motor cortex

superior cerebellar peduncles

connect cerebellum to midbrain

medial lemniscus

bands of ascending, myelinated axons running through the brainstem

substantia nigra

cluster of cells with black appearance due to melanin

houses neurons producing dopamine

- involved in movement, emotions, pleasure and pain response

degeneration causes Parkinson's

tegmentum

involved in postural motor control

contains red nuclei (pigmented) and reticular formation

cerebral aqueduct

connects third and fourth ventricles

surrounded by periaqueductal grey matter

houses nuclei of CN III and IV

tectum

contains four mounds making up the tectal plate

- pair of superior colliculi control visual reflexes & tracking

- pair of inferior colliculi control auditory reflexes

pons

bulging region on anterior brainstem

includes sensory and motor tracts connecting brain to spinal cord

components of pons

middle cerebellar peduncles

pontine respiratory center

superior olivary nuclei

cranial nerve nuclei

middle cerebellar peduncles

transverse axons connecting pons to cerebellum

pontine respiratory center

helps regulate skeletal muscles of breathing

superior olivary nuclei

help with sound localization

cranial nerve nuclei (in pons)

sensory and motor

nuclei for CN V - VIII

- trigeminal, abducens, facial and vestibulocochlear

medulla oblongata

inferior portion of brainstem

continuous with spinal cord inferiorly

includes sensory and motor tracts connecting brain to spinal cord

components of medulla

pyramids

olives

inferior cerebellar peduncles

autonomic nuclei

cranial nerve nuclei

nucleus cuneatus and nucleus gracilis

pyramids

pair of ridges on anterior surface

house corticospinal tracts for motor control

- most tract axons cross at the decussation of the pyramids so each side of cortex controls movement on opposite side of the body

olives

bulges lateral to each pyramid

contain inferior olivary nucleus

relay proprioceptive information to cerebellum

inferior cerebellar peduncles

tracts connecting medulla to cerebellum

autonomic nuclei of medulla

cardiac center

vasomotor center

medullary respiratory center

others for varied functions

cardiac center in medulla

regulates heart's output

vasomotor center of medulla

regulates blood vessel diameter

strong influence on BP (vessel constriction --> increased pressure)

medullary respiratory center

controls breathing rate

contains dorsal and ventral respiratory groups

communicates with pontine respiratory center

other nuclei in the medulla

varied functions

coughing, sneezing, vomiting, salivating, swallowing

cranial nerve nuclei of medulla

nuclei of vestibulocochlear, glossopharngeal, vagus, accessory, and hypoglossal nerves

nucleus cuneatus and nucleus gracilis

receive somatic sensory information

send signals through medial lemniscus to thalamus

cerebellum

2nd largest brain area

4th ventricle

left and right cerebellar hemispheres

each hemisphere has an anterior and posterior lobe separated by a primary fissure

vermis

narrow band of cortex between left and right cerebellar lobes

receives sensory signals regarding torso and balance

3 regions of cerebellum

cerebellar cortex

arbor vitae

deep cerebellar nuclei of grey matter

cerebellar cortex

outer grey matter

arbor vitae

internal region of white matter

nerve tracts that connect cerebellum to brainstem

superior/medial/inferior cerebellar peduncles

functions of cerebellum

coordinates and "fine-tunes" movements

ensures muscle activity follows correct pattern

stores memories of previously learned movements (riding a bike)

regulates activity along voluntary and involuntary motor paths

adjusts movements initiated by cerebrum, ensuring smoothness

helps maintain equilibrium and posture

- receives proprioceptive information from muscles and joints

continuously receives motor plans and sensory feedback

ataxia

drunken walk

loss of balance and posture

inability to detect proprioceptive information

intention tremor

inability to correct plan for muscle movement based on body position and environment

results in tremor/shakes when attempting to move (no tremor when still)

chiari malformation

skull places pressure on the cerebellum and may cause symptoms associated with cerebellar disfunction

cranial meninges

three connective tissue layers

separate and support soft tissue of brain

enclose and protect blood vessels supplying the brain

help contain and circulate cerebrospinal fluid

cranial meninges from deep to superficial

pia matter

arachnoid matter

dura matter

which cranial meninges is touching the skull

dura (dura --> hard --> skull is bone)

which cranial meninges is touching the brain

pia matter

pia matter

innermost of meninges

adheres to brain surface

thin layer of areolar CT

arachnoid matter

lies external to pia matter

made of a web of collagen and elastic fibers

deep to dura matter

arachnoid trabeculae

extend to pia matter through subarachnoid space

subarachnoid space

separates pia matter and arachnoid matter

contains cerebrospinal fluid

subdural space

potential space that can fill with blood if a vein is ruptured

dura matter

tough outer membrane

DICT in 2 layers

- meningeal layer (deep)

- periosteal layer (more superficial)

- forms periosteum on internal surface of cranial bones

layers are usually fused but in some areas they separate to form dural venous sinuses that drain blood from the brain

epidural space

potential space between dura and skull

contains arteries and veins

epidural hematoma

pool of blood in epidural space of brain

usually due to severe blow to the head

adjacent brain tissue distorted and compresses

can lead to severe neurological injury or death unless bleeding stopped and blood removed

subdural hematoma

hemorrhage in subdural space

typically from ruptured beins from fast rotational head movement

compression of brain tissue, occurs more slowly than epidural hematoma

which is worse, subdural or epidural hematoma?

subdural bc bleeding is slower so it's less noticeable immediately

meningitis

inflammation of the meninges typically caused by viral or bacterial infections

symptoms: fever, headache, vomiting, stiff neck

- pain from meninges sometimes referred to posterior neck

may result in brain damage and death if untreated

bacterial meningitis has more severe symptoms

encephalitis

inflammation of the brain, most often from viral infections

symptoms: drowsiness, fever, headache, neck pain, may result in death

cranial dural septa

sheets of dura mater that extend into cranial cavity

form partitions between brain areas; provide support

diaphragma sellae

smallest of dural septa

forms "roof" over sella turcica of sphenoid bone

has small opening for stalk of pituitary gland

ventricles

cavities within the brain

lined with ependymal cells and contain cerebrospinal fluid

connect with each other and with spinal cord's central canal

two lateral ventricles

large cavities in cerebrum

separated by medial partition

- septum pellucidum

third ventricle

narrow space in middle of diencephalon

connected to each lateral ventricle by interventricular foramen

fourth ventricle

sickle shaped space between pons and cerebellum

connected to third ventricle by cerebral aqueduct

opens to subarachnoid space medially and laterally

narrows before merging with central canal of spinal cord

cerebrospinal fluid

clear colorless liquid surrounding CNS

circulates in ventricles and subarachnoid space

functions of CSF

buoyancy

- reduced brain's apparent weight by 95%

protection

- provides a liquid cushion

environmental stability

- transport of nutrients/wastes and protects against fluctuations

CSF formation

formed by choroid plexus lining each ventricle

- layer of ependymal cells and blood capillaries

blood plasma is filtered through capillary and modified by ependymal cells

- compared to plasma CSF has more Na+, Cl- and less K+, Ca2+, glucose

ependymal cell secretions and interstitial fluid from subarachnoid space help make up CSF

continually formed and reabsorbed

differences between ion concentrations in plasma and CSF

CSF has more Na+ Cl-

less K+ Ca2+ glucose

what happens to excess CSF

flows into arachnoid villi and drains into dural venous sinuses

hydrocephalus

pathologic condition of excessive CSF

- usually due to impaired flow/drainage

often leads to brain compression

in young children results in enlarged head with possible neurological damage

can be treated surgically

- implant shunts that drain CSF to other body regions

functions of the blood brain barrier

regulates which substances enter brains interstitial fluid

helps prevent neuron exposure to harmful substances

- drugs, waste, abnormal solute [ ]s

what composes the BBB

specialized capillaries

endothelial cells are connected by many tight junctions

walls have a thick basement membrane

wrapped by perivascular feet (astrocyte extensions)

where is the BBB reduced and why

choroid plexus needs to produce and move CSF

hypothalamus and pineal gland need to secrete hormones to other areas of the body

limbic system

the emotional brain

composed of multiple cerebral and diencephalic structures that process and experience emotions

lymbic system components

cingulate gyrus

parahippocampal gyrus

hippocampus

amygdaloid body

olfactory bulbs/tracts/cortex

fornix

nuclei interconnecting to other parts of the limbic system

cingulate gyrus

in sagittal plane above corpus callosum

parahippocampal gyrus

associated with hippocampus

cortical tissue in temporal lobe

hippocampus

superior to parahippocampal gyrus (temporal lobe)

helps form long-term memories

amygdaloid body

involved in many aspects of emotion and emotional memory

ESPECIALLY FEAR

olfactory bulbs/tracts/cortex

process odors that can provoke emotions

fornix

thin white tract connecting hippocampus with other limbic structures

reticular formation

loosely organized grey matter of brainstem

motor and sensory components

motor component of reticular formation

regulates muscle tone via spinal cord connections

assists in autonomic functions through brainstem connections

sensory component of reticular formation

RETICULAR ACTIVATING SYSTEM

processes sensory information, sends signals to cortex to bring about alertness (ex: response to sound of alarm clock)

altertness helps bring about awareness (of sensations, movements, and thoughts) which is necessary for highest states of consciousness

fainting

brief loss of consciousness

often signals inadequate cerebral blood flow due to low blood pressure/sugar

stupor

arousable only to extreme stimuli

accompanies some metabolic disorders, liver or kidney disease, brain trauma, or drug use

coma

deep and profound unconsciousness; nonresponsive

causes include severe head injury, metabolic failure, CVA, very low blood sugar, drugs

persistent vegetative state

lack of thought and awareness but noncognitive brain functions continue

some spontaneous movements possible

higher order mental functions

learning memory and reasoning

involve multiple brain regions

both conscious and unconscious processing involved

where do higher order mental functions occur

within the cortex of cerebrum

CNS development

processing abilities become complex w maturation

CNS axon myelination increases speed of processing

brain growth is rapid in early childhood

- 95% complete by age 5

beyond early childhood, processing is more complex and refined

- new connections made and others are pruned

some CNS axons are still myelinated during adolescence

- PNS axons keep myelinating past puberty

when are axons myelinated?

most CNS axons during first 2 years of life

CNS axons in prefrontal cortex during adolescence

PNS continue past puberty

insomnia

difficulty in falling asleep or staying asleep

more common w age

sleep apnea

breathing interruptions during sleep

frequent awakenings ---> lack of sleep

treated with CPAP mask

cognition

mental processes of awareness, knowledge, memory, perception, and thinking

association areas of the cerebrum are responsible

agnosia

inability to recognize of understand meaning of stimuli

location of lesion determines nature of loss

ex: lesion in temporal lobe may lead to inability to recognize meaning of sounds/words

alzheimer's disease

leading cause of dementia in developed world

slow, progressive loss of higher intellectual function

usually starts after age 65

changes in mood/behavior

- eventual loss of memory and personality

underlying cause is unknown

- significance of beta amyloid plaques and tau tangles is debated

no cure, some medications help

identifiable with PET

loss of smell may be an early sign

amnesia

partial of complete loss of memory

usually temporary and affecting only a portion of experiences

caused by psychological trauma or direct brain injury

degree of recovery depends on where the brain was damaged

damage to thalamus and limbic structures, ESPECIALLY HIPPOCAMPUS, disrupts/prevents formation of new memories

brain regions involved in emotion

emotions are interpreted by limbic system

expression is controlled by prefrontal cortex

amygdaloid body and hippocampus

- if damage or artificially stimulated, emotions are deadened or exaggerated and learning is impaired

language areas of the brain

wernicke area interprets language

broca's area initiates motor speech program

primary motor cortex signals motor neurons to produce speech

speech and the hemispheres of the brain

categorical hemisphere analyzes the literal meaning of speech

- includes wernicke's area

representational hemisphere analyzes emotional context

aprosodia

dull emotionless speech

caused by lesion to right hemisphere opposite wernicke's area

apraxia

motor disorder

person is aware of what they want to say but cannot speak properly

aphasia

difficulty understanding of producing speech

may not produce comprehensible speech

- might not realize it

often due to head injury or stroke