brain and brainstem test 4- riley

rostral

towards the forehead

caudal

toward the spinal cord

cerebrum

83% of brain volume

-gyri, sulci

-longitudinal fissure

-corpus callosum

cerebellum

50% of the neurons

second largest region

- in posterior cranial fossa

brainstem

portion of the brain that includes the midbrain, pons, and medulla oblongata

longitudinal fissure

deep groove that separates cerebral hemispheres

gyri

elevated ridges

sulci

shallow grooves

corpus callosum

thick nerve bundle at bottom of longitudinal fissure that connects hemispheres

gray matter

the seat of neurosomas, dendrites and synapses

- little myelin

-forms surface layer

- forms nuclei deep in brain

white matter

bundles of axons

- deep in gray matter

- color from myelin

- composed of tracts, bundles of axons, connect brain to spinal cord

meninges

three layers of membrane that envelop the brain

- in between nervous tissue and bone

-protect brain and provide structure

meningitis

inflammation of the meninges

- caused by bacterial or viral invasion of the CNS

cranial dura matter

has 2 layers

- outer periosteal

- inner meningeal

- separated by dural sinuses

arachnoid mater

-Transparent membrane over brain surface

-Subarachnoid space separates it from pia mater below

-Subdural space separates it from dura mater above in some places

pia matter

-Very thin membrane that follows contours of brain, even dipping into sulci

-Not usually visible without a microscope

Ventiricles

4 internal chambers within the brain

two lateral ventricles

one in each cerebral hemisphere

- interventricular foramen: tiny pore that connects to 3rd ventricle

third ventricle

narrow medial space beneath corpus callosum

fourth ventricle

small triangular chamber between pons and cerebellum

choroid plexus

spongy mass of blood capillaries on the floor of each ventricle

ependymal

type of neuroglia that lines ventricles and covers choroid plexus

- produces CSF

cerebrospinal fluid CSF

clear, colorless liquid that fills the ventricles and canals of CNS

- produces 500mL/day

functions of CSF

buoyancy: allows brain to attain its size without effected by the weight

protection: from hits

chemical stability: rinses away metabolic wastses

blood flow interruption

10 seconds causes loss of consciousness.

1-2 min can causes significant impairment of neural func

4 min+ causes irreversible brain damage

brain barrier system

regulates what substances can get from bloodstream into tissue fluid of the brain

Blood-Brain Barrier

protects blood capillaries throughout brain tissue

- has tight junctions to form capillary walls

- astrocytes contact capillaries

- anything leaving must pass through the cells and not between them

-endothelial cells prevent harmful substances from passing to the brain tissue

blood CSF barrier

protects brain at choroid plexus

- highly permeabke to H2O glucose and lipid soluble (O2, CO2, alc, caffiene, nic)

BBS and diease

can be an obstacle for delivering meds such as antibiotics and cancer drugs

trauma and inflammation to BBS

circumventricular organs are in 3 and 4th ventricles where the barrier is absent

- enables brain to monitor and response to fluctuations in glucose, pH, osmolarity etc

medulla oblongata

begins at the foramen magnum

- extends 3 cm to below pons

- all asending and descending fibers connecting brain and spinal cord pass through

- houses neurosomas of 2nd order sensory neurons

pyramids of medulla

pair of ridges on anterior surface resembling side by side baseball bats

- carry motor signals to skeletal muscles

olives of medulla

prominent bulges lateral to ech pyramid

- relay center for signals to cerebellum

reticular formation

loose network of nuclei extending throughout medulla, pons and midbrain

pons

anterior bulge in brainstem

-cranial nerves V,VI,VII< VIII

- sensory roles: hearing, equilibrium,taste, facial sensations

-motor roles: eye movement, facial expressions, chewing, swallowing, urination, saliva and tears

RT: sleep respiration and posture

mid brain

short segment of brain stem that connects hindbrain to forebrain

- contains cerebral aqueduct

involved in controlling pain

- motor nuclei of CN III and CN IV

corpa quadrigemina

exhibits 4 bulges

- visual attention, tracking moving objetcs, some reflexes

cerebral peduncles

two anterior midbrain stalks that anchor the cerebrum to the brainstem

tegmentum

Dominated by red nucleus

Pink color due to high density of blood vessels

Connections go to and from cerebellum for motor control

substantia nigra

-Black nucleus pigmented with melanin

-Motor center that relays inhibitory signals to thalamus and basal nuclei preventing unwanted body movement

-Degeneration of neurons leads to tremors of Parkinson disease

somatic motor control

adjust muscle tension to maintain tone, balance, and posture

relay signals from eyes/ears to cerebellum

integrate visual auditory balance and motion stimuli into coordination

gaze centers: eyes to track and fixate

Cardiovascular Control

cardiac and vasomotor centers of medulla oblongata

Pain Modulation

Some pain signals ascend through the reticular formation

Some descending analgesic pathways begin in the reticular formation

They end in the spinal cord where they block transmission of pain signals

sleep and consciousness

Reticular formation plays a central role in consciousness, alertness and sleep

Injury here can result in irreversible coma

Habituation

reticular activating system modulates activity in cerebral cortex so that it ignores repetitive and inconsequential stimuli

cerebellar peduncles

three pairs of stalks that connect the cerebellum to the brainstem

inferior peduncles

connected to medulla oblongata

Most spinal input enters the cerebellum through inferior peduncle

middle peduncles

connected to pons

most input from rest of brain enters through middle

superior peduncles

connected to the midbrain

carries cerebellar output

Cerebellum is important for

moto coordination

locomotor ability

sensory, linuistic, emotional fucntions have recently been discovered

diencephalon

encloses thrid ventircle

most rostral part of brain stem

telencephalon

develops chiefly into cerebrum

thalamus

ovoid mass on each side of the brain perched at the superior end of the brainstem beneath the cerebral hemispheres

thalamus function

gateway to the cerebral cortex;

major relay station for most sensory inputs;

invloved in memory and emotion functions of the limbic system

hypothalamus

forms part of the walls and floor of the thurd ventricle

- extends to optic chasm and mammllary bodies

-ESSENTIAL role in homeostatic regulation of all body systems

mammillary body

contain 3-4 mammillary nuclei

- relay signals from limbic system to the thalamus

infundibulum

stalk attaching pituitry to hypothalamus

hypothalamic nuclei

controls antertior pituitary, and regulates growth, metabolism, reproduction, and stress

produces pituitary hormones for labor

autonomic: integrating center for autonomic nervous system, influences heart rate, bp, motility, etc

hypothalamic functions

thermoregulation

food and water intake

sleep

memory

emotional behavior

sexual response

epithalamus

very small mass of tissue

pineal gland: endocrine

habenula: relay from limbic to midbrain

thin roof over third ventricle

gyri and sulci

increase amount of cortex in the cranial cavity allowing more info processing capability

projection tracts

extend vertically between higher and lower brain and spinal cord centers

association tracts

connect different regions of the cerebral cortex within the same hemisphere

- long fibers connect different lobes, short fibers connect gyri within lobe

commissural tracts

cross from one hemisphere to the other while allowing communication between 2 sides of cerebrum

neural integration

is carried out in the gray matter of the cerebrum

cerebral cortex

covers surface of hemispheres

- 2-3 mm thick

- 40% of brain mass

stellate cells

-have spheroid somas with dendrites projecting in all directions

-receive sensory input and process information on a local level

pyramidal cells

-tall, and conical, with apex toward the brain surface

-a thick dendrite with many branches with small, knobby dendritic spines

-include the output neurons of the cerebrum

-only neurons that leave the cortex and connect with other parts of the CNS

limbic system

important center of emotion and learning

cingulate gyrus

arches over corpus callosum in frontal and parietal lobes

hippocampus

in medial temporal lobe w memory functions

amygdala

immediately rostral to hippocampus

basal nuclei

masses of cerebral gray matter buried deep in the white matter, lateral to the thalamus

- receive input from midbrain and motor aeras

-sends signals back

-involved in motor control

corpus striatum

caudate nucleus

putamen

globus pallidus

(p+g= lentiform nucleus)

primary sensory cortex

sites where sensory input is first received and one becomes conscious of the stimulus

primary visual cortex

is bordered by visual association areas, make cognitive sense of visual stimuli

multimodal association areas

receive input from multiple sense and integrate this into an overall perception of our surroundings

special senses

limited to the head and employ relatively complex sense organs (vision, hearing, equilibrium, taste, smell)

vision

- visual primary cortex in far posterior region of occipital lobe

- visual association area: anterior and occupies all remaining occipital lobe

hearing

primary auditory cortex in superior region of temporal love and insula

auditory association area: temporal lobe deep nd inferior to primary

equilibrium

signals for balance and sense of motion project mainly to cerebellum and brainstem nuclei concerned with heead and eye movements

- association cortex in the roof of the lateral sulcus near lower end of central sulcus

taste and smell

-Gustatory (taste) signals received by primary gustatory cortex in inferior end of the postcentral gyrus of the parietal lobe and anterior region of insula

-Olfactory (smell) signals received by the primary olfactory cortex in the medial surface of the temporal lobe and inferior surface of the frontal lobe

general senses

distributed throughout the body

- touch pressure stretch movement heat cold pain

thalamus and senses

processes the input from contralateral side

- relays signals to postcentral gyrus of parietal lobe

somestheic association area

caudal to the post central gyrus and in roof od lateral sulcus

- makes cognitive sense of stimulus

sensory homunculus

diagram of the primary somesthetic cortex which resembles an upside-down sensory map of the contralateral side of the body

- shows receptors in lower limbs

- shows receptors from face

Somatotopy

point-to-point correspondence between an area of the body and an area of the CNS

precentral gyrus

primary motor area

- most posterior gyrus of frontal lobe

-these neurons send signals to brainstem and spinal cord leading ultimately to muscle contractions

- also has somatotopy

motor control

cerebellum

basal nuclei

pyramidal cells

precentral gyrus

Dyskinesias

movement disorders caused by lesions in the basal nuclei

Wernicke's area

posterior to lateral sulcus

permits recognition of spoken and written language

Broca's area

inferior prefrontal cortex

- motor program for muscles in larynx, tounge, cheeks, and lips for speaking

affective language area

usually in right hemisphere

Lesions produce aprosody—flat emotionless speech

Aphasia

impairment of language, usually caused by left hemisphere damage either to Broca's area (impairing speaking) or to Wernicke's area (impairing understanding).

Nonfluent (Broca) aphasia

-lesion in Broca area

-slow speech, difficulty in choosing words, using words that only approximate the correct word

Fluent (Wernicke) aphasia

Lesion in Wernicke area

Speech normal and excessive, but uses senseless jargon

Cannot comprehend written and spoken words

Anomic Aphasia

can speak normally and understand speech, but cannot identify written words or pictures

cerebral lateralization

the difference in the structure and function of the cerebral hemisphere

left hemisphere

usually the categorical hemisphere

Specialized for spoken and written language

Sequential and analytical reasoning (math and science)

Breaks information into fragments and analyzes it

right hemisphere

usually the representational hemisphere

Perceives information in a more integrated way

Seat of imagination and insight

Musical and artistic skill

Perception of patterns and spatial relationships

Comparison of sights, sounds, smells, and taste