A&P Ch 14 The Brain

integrative centers

-*receive info from many association areas* -complex motor activities -complicated analytical functions

substantia nigra

-melanin -> tyrosine -> catecholamines (dopamine) -dopamine inhibits activity of basal nuclei -found in midbrain

epithalamus

-roof of 3rd ventricle -contains *pineal gland,* which secretes *melatonin* (day/night cycles & reproduction)

choroid plexus

-site of CSF production -creates blood-CSF barrier

somatic sensory association area (somatosensory association cortex)

-*monitors* activity in & *integrates* sensory input from the *primary sensory cortex* -produces understanding of object being felt & stores past sensory experiences

prefrontal cortex

-*most complicated* -integrates information from sensory association areas and performs *abstract intellectual functions* -involved with intellect, *cognition*, recall and personality -necessary for the production of abstract ideas, judgment, reasoning, persistence, long-term planning, empathy, conscience, mood -*closely linked with the Limbic System*(emotional part of the brain) -extensive connections with other cortical areas

Parkinson's disease

-*motor system disorder*, result of the loss of *dopamine-producing brain cells* -four primary symptoms are *tremor; rigidity; slowness of movement (bradykinesia); and postural instability*

precentral gyrus

-*primary motor cortex* -contain *pyramidal cells* -motor innervation is contralateral

postcentral gyrus

-*primary sensory cortex* -*receive* info from somatic sensory receptors & proprioceptors -once info is received, neurons identify the body region being stimulated (*Spatial Discrimination*)

auditory cortex

-*receives audio info from inner ear* where its related to pitch, rhythm & loudness

dementia

-Chronic or persistent disorder of the mental processes caused by brain disease or injury -Marked by memory disorders, personality changes and impaired reasoning

basal nuclei

-Involved w subconscious control of sk. muscle tone -Coordination of learned movement patterns and rhythm -Important in starting, stopping and monitoring the intensity of movements executed by the cortex -Inhibit antagonist or unnecessary movements -Disruption to the activity of the basal nuclei results in either too much or too little movements (eg. Parkinson's and Huntington's Chorea) -Activity is inhibited by the *Substantia Nigra* of the midbrain (releases Dopamine)

blood-brain barrier (& breaks)

-Isolates CNS from general circulation -tight junctions between endothelial cells of CNS capillaries -astrocytes release chemicals to control permeability of endothelium Breaks: 1. *Portions of hypothalamus* -Secrete hypothalamic hormones 2. *Posterior lobe of pituitary gland* -Secretes hormones ADH and oxytocin 3. *Pineal gland* -Pineal secretions 4. *Choroid plexus*

purkinje cells

-Large, multipolar branched cells -Found in cerebellar cortex -Receive input from up to 200,000 synapses

medulla oblongata

-coordination of complex autonomic reflexes & visceral functions *Autonomic nuclei:* -*cardiovascular centers*: cardiac (HR & contraction) & vasomotor centers (BV diameter & BP) -*respiratory rhythmicity centers* -*reticular formation:* medulla -> midbrain

CSF functions

-cushion -buoyancy: supports by reducing brain weight -transport

pia mater

-delicate connective tissue that adheres directly to the surface of the brain -anchored by processes of *astrocytes* -follows every fold and groove of the brain -*highly vascularized*

Limbic system

-emotional brain, interacts w prefrontal cortex, but can conflict -evolutionary origins in olfactory cortex -most info is relayed through hypothalamus -*amygdala:*fear response -*hippocampus:* learning & long-term memory -*fornix:* connects hippocampus to hypothalamus

blood-csf barrier

-formed by ependymal cells -surrounds capillaries of choroid plexus

vagus (N X)

-from internal organs -to internal organs

trigeminal (N V)

-from mouth -to jaw muscles

glossopharyngeal (N IX)

-from pharynx -to pharyngeal muscles

facial (N VII)

-from tastebuds -to facial muscles & glands

dural sinus

-gaps between endosteal and meningeal layer of dura mater -an interconnected series of enlarged chambers that collect venous blood from the brain -> internal jugular vein -> heart

gustatory cortex

receives info from taste receptors of tongue & pharynx

CVA (cerebrovascular accident)

-shuts off blood to portion of brain -neurons die

subdural space

separates dura mater from arachnoid mater

auditory association area

-*monitors sensory activity in auditory cortex* -permits perception of the sound stimulus (music, thunder, etc) -memories of sounds heard in past stored here

general interpretive area

- not well defined region, but found in parts of temporal, parietal and occipital lobes -receives info from all sensory association areas -only found in one hemisphere (usu. left) -plays an essential role in personality by integrating sensory information and -coordinates access to complex visual and auditory memories -involved in *language and mathematical calculation*

reticular formation

-"on" switch -medulla -> midbrain -Reticular activating system: sensory impulses synapse w RAS neurons, keeping active -filters out white noise -inhibited by sleep centers -severe damage = irreversible coma

midbrain

-*cerebral peduncles* connect primary motor ctx w motor neurons in brain & SC via *corticospinal motor tracts* (white matter) *Corpora Quadrigemina* (gray matter) -*sup. colliculi*: visual reflexes -*inf. colliculi*: auditory reflexes

hypothalamus

-*mamillary bodies:* process olfactory info -*infundibulum:*connects pituitary gland -*tuberal area:* produces hormones that regulate pituitary gland

cerebral cortex

-Surface layer of cerebrum -higher mental functions 1. Contains 4 kinds of functional areas: - Motor Areas - Sensory Areas - Association Areas - Integrative Centers 2. Each hemisphere receives sensory info from, & sends motor commands to, the *opposite* side of the body 3. hemispheres = different functions, similar structures 4. Overlap of regions & functions

pyramidal cells

-allow conscious control of precise or skilled voluntary movement of skeletal muscle -long axons project into spinal cord forming corticospinal tracts -multipolar -found in *primary motor cortex* (pre central gyrus)

Alzheimer's disease

-an irreversible, progressive brain disease that slowly destroys memory and thinking skills, and eventually even the ability to carry out the simplest tasks -most common cause of dementia among older people -symptoms include memory loss, language problems, and unpredictable behavior -involves the formation of many abnormal clumps (*amyloid plaques*) and tangled bundles of fibers (*neurofibrillary tangles*) and the loss of connections between neurons in the brain.

commissural fibers

-bands of fibers *connecting* two hemispheres -*corpus callosum* & *anterior commissure*

epidural hemorrhage

-bleeding between cranium & dura mater -most serious when due to arterial break bc arterial BP is very high, putting pressure on brain -if due to vein damage, symptoms may not be immediate -less common

pons

-bridges cerebellum to rest of brain Projection fibers link higher brain & spinal cord: -*ascending tracts:* medulla -> thalamus -*descending tracts:* higher -> motor nuclei -also has transverse fibers to link pons w cerebellum (via *middle cerebellar peduncle*)

association fibers

-connections *within* a hemisphere *arcuate fibers:* shorter, connect gyri *longitudinal fasciculi:* longer, connect frontal lobe to other lobes in same hemisphere (needed by *integration centers*)

diencephalon

-consists of all gray matter -encloses the 3rd ventricle parts: -epithalamus -thalamus -hypothalamus

ventricles

-continuous w one another and central canal -filled w CSF, lined w ependymal cells

cerebral palsy

-idiopathic, refers to any one of many neurological disorders appearing in infancy/early childhood and permanently affect body movement & muscle coordination -caused by *abnormalities in parts of the brain that control muscle movements* -most common are a *lack of muscle coordination when performing voluntary movements (ataxia); tight muscles and exaggerated reflexes (spasticity); walking with one foot/leg dragging; walking on toes, crouched gait* -small number of children have cerebral palsy as the result of brain damage, brain infections, or head injury

nuclei involved w respiration

-in pons -*apneustic* center: deep, conscious inhalation -*pneumotaxic* center: big, conscious exhalation

Huntington's Disease

-inherited disease that causes certain nerve cells in the brain to *waste away* -*genetic disorder* with symptoms usually don't appear until middle age -early symptoms include *uncontrolled movements, clumsiness, and balance problems*. -later symptoms include the *inability to walk, talk, and swallow and memory disorders, personality changes and impaired reasoning*

visual association area

-interprets results from visual cortex (ex: C A R = car) -uses past info to interpret visual stimuli (visual recognition)

arachnoid villi

-knoblike projections of the arachnoid mater -in adults, clustered together to form Arachnoid Granulation that protrude into the meningeal layer of the dura mater

visual cortex

-largest of all cortical sensory areas -receives visual info from retina (ex: seeing the letters C A R)

projection fibers

-longest, connect cerebrum w *lower areas* -pass through diencephalon -*internal capsule:* collection of projection fibers

premotor cortex (somatic motor association area)

-memory bank for skilled motor activities -coordination of learned movements -communicates w primary motor cortex to allow movement

dura mater

-most external layer -strongest meninx

brain stem

-produce programmed, automatic behaviors for survival -nuclei associated w 10 of 12 cranial nerves Parts: -*midbrain* -*pons* -*medulla oblongata*

dural fold

-provide additional stabilization and support to the brain by limiting excessive movement of the brain within the cranium -created by meningeal layer of dura mater

Broca's area (speech center)

-regulates patterns of breathing & vocalization needed for normal speech (directs muscles) -present in one hemisphere (usually the left) -motor commands are adjusted by feedback from the auditory association area (receptive speech area) -responsible for *language-based skills* (motor speech area + general interpretive area)

thalamus

-relay center: afferent impulses from all senses (except smell) communicate w at least one of the thalamic nuclei, info is then sent to specific association area -also funnels all other inputs going to cerebral cortex -contains most of the neural tissue in diencephalon -held together by intermediate mass

subdural hemorrhage

-separation of and bleeding between endosteal & meningeal layers of the dura mater -blood from small vein or dural sinus -less pressure exerted on brain compared to epidural -distortion & effects are gradual

4 regions

1. Cerebrum 2. Diencephalon (epithalamus, thalamus, hypothalamus) 3. Brain stem (midbrain, pons, medulla oblongata) 4. Cerebellum

Hypothalamus Functions (8)

1. Subconscious control of sk. muscle 2. Autonomic function (HR, BP, resp, dig, etc) 3. Coordinates nervous & endocrine (via production of regulatory hormones) 4. Secretes hormones ADH & OT 5. Emotions & behavioral drives (hunger, thirst) 6. Coordinates voluntary & autonomic functions 7. Regulates body temp 8. Circadian rhythms

3 regions (of cerebrum)

1. cerebral cortex (superficial gray matter) 2. white matter (internal) 3. basal nuclei (islands of gray matter within)

Spinal cord vs Brain stem structure

Both have gray surrounded by white, but brain stem also has nuclei of gray matter embedded in white

Cerebellum

Responsible for: 1. Adjusting Postural Muscles of the Body 2. Programming and Fine-Tuning Movements at the Conscious and Subconscious Levels

synchronization

Synchronizes electrical activity between hemispheres Brain damage can cause Desynchronization

seizure

Temporary cerebral disorder Changes the electroencephalogram (EEG) Symptoms depend on regions affected Clinical conditions characterized by seizures are knows an Epilepsies

concussion

a brain injury often caused by a hit to the head that may result in a bad headache, altered levels of alertness, loss of memory or unconsciousness

olfactory cortex

afferent fibers from smell receptors in the superior nasal cavities send impulses along the olfactory tract that are relayed to the olfactory cortex giving us conscious awareness of different odors -found in small area of *temporal lobe*

internal jugular

carries blood *FROM brain* to heart

internal carotid

carries blood *TO brain* from heart

white matter

composed primarily of axon fibers, myelinated

gray matter

composed primarily of cell bodies, unmyelinated

meningeal layer (of dura mater)

continues caudally in the vertebral canal as the dural sheath of the spinal cord

frontal eye field

controls voluntary eye movements i.e.: scan lines when reading

subarachnoid space

filled w CSF and Arachnoid Trabeculae (series of cells and fibers that form web-like extensions secure arachnoid mater to pia mater)

vestibulocochlear (N VIII)

from inner ear

olfactory (N I)

from olfactory receptors

optic (N II)

from retina of eyes

endosteal layer (of dura mater)

fused to the periosteum of the cranial bones (no epidural space)

decussation

part of medulla where crossover occurs

cerebellar peduncles

superior: midbrain to cerebellum middle: pons to cerebellum inferior: medulla to cerebellum

abducens (N VI)

to eye muscles

oculomotor (N III)

to eye muscles

trochlear (N IV)

to eye muscles

accessory (N XI)

to neck and back muscles

hypoglossal (N XII)

to tongue muscles