divisions of the nervous system

cephalization

evolutionary development of rostral (anterior) portion of the CNS

resulted in increased number of neurons

highest level reached in human brain

adult brain regions

cerebral hemispheres

diencephalon

brain stem

cerebellum

brain stem regions

midbrain, pons, medulla

spinal cord composition

gray matter- short nonmyelinated neurons and cell bodies

white matter- myelinated and some nonmyelinated axons

brain stem composition

has additional gray matter nuclei scattered within white matter

cerebral hemispheres and cerebellum composition

outer layer of gray matter- cortex

scattered areas of gray matter nuclei amid white matter

ventricles

fluid filled chambers that are continuous to one another and to central canal of spinal cord

filled with cerebrospinal fluid

lined by ependymal cells (neuroglial)

paired, lateral- large, C-shaped chambers deep in each hemisphere

lateral ventricles

each is connected to the third ventricle via interventricular foramen

large c shaped chambers deep in each hemisphere

third ventricle

lies in diencephalon

connected to fourth ventricle via cerebral aqueduct

continuous with central canal of spinal cord

fourth ventricle

three openings connect it to subarachnoid space that surrounds the brain

connected to third ventricle via cerebral aqueduct

cerebral hemispheres

form superior part of brain- 83% of brain mass

have gyri, sulci, and fissures

each has cerebral cortex, white matter, and basal nuclei

gyri

surface marking on cerebral hemispheres

ridges

sulci

surface markings on cerebral hemispheres

shallow grooves

fissures

surface markings on cerebral hemispheres

deep groves

longitudinal and transverse cerebral

longitudinal fissure

separates the two cerebral hemispheres

transverse cerebral fissure

separates the cerebrum and cerebellum

brain lobes

frontal, parietal, temporal, occipital, insula

insular lobe

buried under portions of temporal, parietal, and frontal lobes

central sulci

separates precentral gyrus of frontal lobe and postcentral gyrus of parietal lobe

parieto-occipital sulcus

separates occipital and parietal lobes

lateral sulcus

outlines temporal lobes

cerebral cortex

site of conscious mind- awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding

specific motor and sensory functions are located in discrete cortical areas called domains

domains

discrete cortical areas

• higher functions are spread over many areas

cerebral cortex composition

thin (2-4mm)

superficial layer of gray matter

composed of neuron cell bodies, dendrites, glial cells, blood vessels

no axons

40% of mass of brain

cerebral cortex considerations

contains three types of functional areas- motor, sensory, and association

each hemisphere is concerned with contralateral side of body

lateralization

conscious behavior involves entire thing in one way or another

lateralization

specialization of cortical function can occur in only one hemisphere

motor areas of the cerebral cortex

located in frontal lobe

control voluntary movement

primary motor cortex in precentral gyrus

premotor cortex anterior to precentral gyrus

broca’s area anterior to inferior premotor area

frontal eye field within and anterior to premotor cortex, superior to brocas area

primary motor cortex

conscious control of precise skilled skeletal muscle movements carried out by pyramidal cells

somatotopy- all muscles of body can be mapped to area originating here

motor homunculi

upside down caricatures represent contralateral motor innervation of body regions

premotor cortex

helps plan movements- staging area for skilled motor activities

controls learned, repetitious, or patterned motor skills

coordinates simultaneous or sequential actions

controls voluntary actions that depend on sensory feedback

broca’s area

present in one hemisphere

motor speech area that directs muscles of speech production

active in planning speech

frontal eye field

controls voluntary eye movements

damage to primary motor cortex

stroke

paralyzes muscles controlled by those areas

paralysis occurs on opposite side of the body from damage

damage to areas of premotor cortex

apraxia

deficits in contralateral fine motor control- performance of complex serial movements

other neurons can be reprogrammed to take over skill of damaged neurons

• requires practice, like initial learning process

apraxia

the inability to carry out skilled actions that could previously be performed

no paralysis

due to damage of premotor cortex

sensory areas of the cerebral cortex

concerned with conscious awareness of sensation

occur in parietal, insular, temporal, and occipital lobes

eight main areas

somatosensory areas of cerebral cortex

primary somatosensory cortex

somatosensory association cortex

visual areas

auditory areas

vestibular cortex

olfactory cortex

gustatory cortex

visceral sensory area

primary somatosensory cortex

receives general sensory information from skin and proprioceptors of skeletal muscles, joints, and tendons

somatosensory association cortex

posterior to primary somatosensory cortex

integrates sensory input from primary somatosensory cortex for understanding of object

visual areas

primary visual (striate)

visual association area

primary visual area

located on extreme posterior tip of occipital lobe

receives visual information from retinas

damage to the primary visual cortex results in functional blindness

visual association area

surrounds primary visual cortex

uses past visual experiences to interpret visual stimuli

ability to recognize faces

damage - can see but cant comprehend what you’re looking at 

auditory areas

primary auditory cortex

auditory association area

primary auditory cortex

superior margin of temporal lobes

interprets information from inner ear as pitch, loudness, and location

auditory association area

located posterior to primary auditory cortex

stores memories of sounds and permits perception of sound stimulus

vestibular cortex

posterior part of insula and adjacent parietal cortex

responsible for conscious awareness of balance

position of head in space

olfactory cortex

medial aspect of temporal lobes

involved in conscious awareness of color

gustatory cortex

in insula, deep to temporal lobe

involved in perception of taste

visceral sensory area

in insula, posterior to gustatory cortex

conscious perception of visceral sensations

upset stomach, full bladder

multimodal association areas

receive inputs from multiple sensory areas

send output to multiple areas

allows us to give meaning to information received, store in memory, tie to previous experience, decide on actions

sensations thoughts emotions become conscious

divided into three parts

division of multimodal association area

anterior, posterior, and limbic

anterior association area

prefrontal cortex

most complex cortical region

involved with intellect, cognition, recall, personality

contains working memory needed for abstract ideas, judgement, reasoning, persistence, and planning

development depends on feedback from social environment

inhibition of anterior association area

tumors or lesions may cause mental and personality disorders

loss of judgement, attentiveness, inhibitions

affected individual may be oblivious to social restraints- become careless abt personal space, take risks

posterior association area

large region in temporal, parietal, and occipital lobes

plays role in recognizing patterns and faces

localizes us in space

involved in understanding written and spoken language- wernickes areas

inhibition of the posterior association area

problems arise for individuals with lesions in the part that provides awareness of self in space

may refuse to wash or dress the side of the body opposite to lesion because “that doesn’t belong to me”

limbic association area

part of limbic system

involves cingulate gyrus, parahippocampal gyrus, hippocampus

provides emotional impact that makes a scene important to us and helps establish memories

lateralization of cortical functioning

divides labor between hemispheres

hemispheres not identical

cerebral dominance

hemispheres communicate instantaneously via fiber tracts and functional integration

cerebral dominance

hemisphere that is dominant for language

90% of right handed humans have left sided dominance

70% of left handed humans have left sided dominance

left hemisphere

controls language math and logic

right hemisphere

visual spatial skills, intuition, emotion and artistic and musical skills

cerebral white matter

responsible for communication between cerebral areas and between cortex and lower CNS

consists of myelinated fibers bundles into large tracts- classified according to direction they run

association, commissural, and projection fibers

association fibers of cerebral white matter

horizontal running fibers that connect different parts of same hemisphere

commissural fibers of cerebral white matter

horizontal fibers that connect gray matter of two hemispheres

projection fibers

vertical fibers that connect hemispheres with lower brain or spinal cord

basal nuclei (ganglia)

basic region of cerebrum

includes a caudate nucleus, putamen, globus pallidus

disorders of it include parkinson’s and huntington’s disease

striatum

caudate nucleus and putamen

basal nuclei functions

influence muscle movements

play role in cognition and emotion

regulate intensity of slow or stereotyped movement

filter out incorrect/inappropriate responses

inhibit antagonistic/unnecessary movements

dicephalon

three paired gray matter structures

thalamus, hypothalamus, epithalamus

thalamus

contains several bilateral nuclei

acts as relay station for information coming to cortex

sorts edits and relays ascending input

• impulses from hypothalamus for regulating emotion and visceral function

• impulses from cerebellum and basal nuclei to help direct motor cortices

• impulses for memory or sensory integration

acts to mediate sensation, motor activities, cortical arousal, learning, and memory

nuclei in thalamus

project and receive fibers from cerebral cortex

input sorted by thalamus

impulses from hypothalamus for regulating emotion and visceral function

impulses from cerebellum and basal nuclei to direct motor cortices

impulse for memory or sensory integration

hypothalamus

below thalamus

main visceral control and regulating center- vital to homeostasis

controls autonomic nervous system 

initiates physical response to emotions

regulates- body temp, hunger and satiety, water balance and thirst, sleep wake cycles

how the hypothalamus regulates hunger and satiety

responds to nutrient blood levels or hormones

infundibulum

in the hypothalamus

stalk that connects to pituitary gland

controls endocrine system functions

• secretions of anterior pituitary gland

• production of posterior pituitary hormones

hypothalamus role in autonomic nervous system

blood pressure, rate and force of heartbeat, digestive tract motility, pupil size

hypothalamus role in physical response to emotions

part of limbic system

perceives pleasure, fear, rage, biological rhythms, and drives (sex)

hypothalamus disturbances

severe body wasting

obesity

sleep disturbances

dehydration

emotional imbalances

damage caused by tumors, radiation, surgery, or trauma

epithalamus

most dorsal portion of diencephalon

contains pineal gland

regulates sleep-wake cycle

pineal gland

secretes melatonin that helps regulate sleep-wake cycle

brain stem

has three parts

similar structure to spinal cord but contains nuclei embedded in white matter

controls automatic behaviors necessary for survival

contains fiber tracts connecting higher and lower neural centers

nuclei are associated with 10 of the 12 pairs of cranial nerves

three parts of brain stem

midbrain, pons, medulla oblongata

midbrain

located between diencephalon and pons

contains cerebral peduncles, cerebral aqueduct, periaqueductal gray matter, and substantia nigra

cerebral peduncles

in the midbrain

two ventral bulges that contain pyramidal motor tracts

cerebral aqueduct

in the midbrain

channel running through midbrain that connects third and fourth ventricles

periaqueductal gray matter

in the midbrain

nuclei that play a role in pain suppression and fight or flight response

substantia nigra

in the midbrain

functionally linked to basal nuclei

degeneration of this area- parkinson’s disease

pons

located between midbrain and medulla oblongata

composed of conduction tracts

• longitudinal fibers

• transverse/ dorsal fibers

some nuclei play role in reticular formation, some help maintain normal rhythm of breathing

longitudinal fibers in pons

connect higher brain centers and spinal cord

transverse/ dorsal fibers in pons

relay impulses between motor cortex and cerebellum

medulla oblongata

blends into spinal cord and foramen magnum

contains fourth ventricle, pyramids, decussation of the pyramids, olives, vestibular and cochlear nuclei

fourth ventricle

continuation of central canal of spinal cord

contains choroid plexus- capillary rich membrane that forms cerebral spinal fluid

pyramids

in medulla oblongata

two ventral longitudinal ridges from by pyramidal tracts from motor cortex

decussation of the pyramids

in medulla oblongata

point where pyramidal tracts cross over to opposite side of body

olives

swellings caused by underlying inferior olivary nuclei that relay stretch information from muscles and joints to cerebellum

functions of medulla oblongata

autonomic reflex center

• many functions overlap with hypothalamus

• hypothalamus relays instructions through this

functional groups include

• cardiovascular center

• respiratory center

• reflexes

medulla oblongata function in cardiovascular center

cardiac center adjusts force and rate of heart contraction

vasomotor center adjusts blood vessel diameter for blood pressure regulation

medulla oblongata function in respiratory centers

generates respiratory rhythm 

controls rate and depth of breathing (with pontine centers)

medulla oblongata role in reflexes

vomiting, hiccupping, swallowing, coughing, sneezing

cerebellum

11% of brain mass

processes sensory input from cortex, brain stem and sensory receptors to provide precise coordinated movements of skeletal muscles

plays a major role in balance

cerebellar hemisphers connected by wormlike vermis

cerebellar anatomy

folia

contains thin cortex of gray matter with distinctive treelike pattern of white matter= arbor vitae

purkinje fibers