BIOL 203 Lecture 12 - Forebrain

prosencephalon

embryonic forebrain

cerebrum and diencephalon

what two major regions does the prosencephalon give rise to

cerebrum

higher cognitive functions, conscious perception, voluntary movement, memory, and language

diencephalon

comprised of the thalamus, hypothalamus, and epithalamus

diencephalon

sensory relay, homeostasis, autonomic and endocrine regulation

cerebrum

what is the top arrow pointing to?

diencephalon

what is the bottom arrow point to?

scalp, skull, periosteal dura, meningeal dura, arachnoid, subarachnoid space, pia, brain

list the anatomical layers protecting the brain from superficial to deep

dura mater

the tough outer meningeal layer

arachnoid mater

middle meningeal layer (thin)

pia mater

thin, delicate meningeal layer; follows the contours of the gyri and sulci

subarachnoid space

actual CSF-filled space underneath arachnoid mater; trabeculae cross the space

falx cerebri

a fold of dura mater that separates the two cerebral hemispheres

gray matter

gray or white matter: processing

white matter

gray or white matter: communication

gray matter

contains many neuronal cell bodies, dendrites, synapses, and glial cells

gray matter

major site of information processing and integration

gray matter

in the cerebrum, forms the cerebral cortex

white matter

contains bundles of axons, many surrounded by myelin

white matter

carries signals between different CNS regions

white matter

in the cerebrum, lies mainly deep to the cerebral cortex

white matter

its lighter appearance is largely due to lipid-rich myelin

cerebral cortex (outer layer) and basal nuclei (deep gray matter structures)

what does gray matter form?

inner region containing nerve fiber tracts

what does white matter form?

pyramidal neurons

the principal excitatory projection neurons of the cerebral cortex

gray matter

central H-shaped region containing neuron cell bodies

white matter

outer region containing ascending and descending tracts

cerebral cortex, subcortical white matter, deep nuclei

three main components of the cerebrum

cerebral cortex

outer layer of gray matter; folded into gyri and sulci

subcortical white matter

axon tracts connecting different regions of the CNS

deep nuclei

collections of gray matter located within the white matter; include the basal nuclei

cerebral cortex

what is the top arrow pointing to?

subcortical white matter

what is the middle arrow pointing to?

deep nuclei

what is the bottom arrow pointing to?

primary area

functional area of cerebral cortex that is involved in processing specific sensory information or generating voluntary motor output

primary area

functional area of cerebral cortex that has the primary visual cortex, primary somatosensory cortex, and primary motor cortex

secondary area

functional area of cerebral cortex that performs more complex processing within a specific sensory or motor system

secondary area

functional area of cerebral cortex that has visual association areas and the premotor cortex

association area

functional area of cerebral cortex that integrates information from multiple cortical regions

association area

functional area of cerebral cortex that supports planning, reasoning, language, memory, attention, and decision-making

frontal, temporal, parietal, occipital, and insula

name the five lobes of the cerebrum

frontal lobe

what lobe is responsible for voluntary motor control, executive functions (planning, decision-making), and speech production (Broca’s area)

temporal lobe

what lobe is responsible for hearing (primary auditory cortex), language comprehension (Wernicke’s area), memory formation/processing, and olfactory processing

parietal lobe

what lobe is responsible for somatosensory processing: touch, pain, temperature, pressure, vibration, proprioception and sensory integration/spatial awareness

occipital lobe

what lobe is responsible for the primary visual cortex (visual processing and interpretation)

insula

what lobe is responsible for visceral sensory processing, taste perception (gustatory cortex), emotional awareness and salience processing, and interoception (internal body state)

blood-brain barrier (cerebral vasculature)

present in most brain capillaries; restricts uncontrolled entry of toxins, pathogens, and many large or hydrophilic molecules; allows selective passage of small lipid-soluble molecules (O2 and CO2), small nonpolar molecules, and essential substances (glucose, amino acids) via transport proteins

blood-CSF barrier (choroid plexus)

produces CSF; regulates movement of substances from blood into the CSF; helps maintain chemical stability of the CNS

brain-CSF barrier (pia arachnoid)

prevents uncontrolled exchange between blood and CSF

tight junctions

_____ _____ prevent paracellular diffusion in the BBB

capillary endothelial cells joined by tight junctions; basement membrane; pericytes; astrocyte end-feet

what are the four main components of the blood-brain barrier

choroid plexus

this contains the fenestrated capillaries covered by specialized epithelial cells; located within the lateral, third, and fourth ventricles; produces the most CSF through selective secretion of ions and water from the blood

blood-CSF barrier

formed primarily by tight junctions between choroid plexus epithelial cells; separates the blood/stroma from the CSF; the underlying capillaries are fenestrated and relatively permeable

blood flows through fenestrated capillaries in the choroid plexus, allowing substances to enter the surrounding stroma

what is the first step of the blood-CSF barrier

before reaching the CSF, substances must pass through choroid plexus epithelial cells, and these cells are connected by tight junctions, which control what can enter the CSF

what is the second step of the blood-CSF barrier

ventricular system

the _____ _____ is a network of interconnected cavities that contain CSF and provide a pathway for its movement

ependymal cells

_____ _____ line the ventricles and central canal; their cilia help move and mix CSF

lateral ventricles, third ventricle, and fourth ventricle

what are the main ventricles

between the thalami

where is the third ventricle located

between the brainstem and cerebellum

where is the fourth ventricle located

lateral ventricles

what is the light orange section called

third ventricle

what is the dark orange section called

fourth ventricle

what is the green section called

interventricular foramina (of Monro)

what is the connection between the lateral and third ventricle called (top arrow)

cerebral aqueduct (of Sylvius)

what is the connection between the lateral and fourth ventricle called (bottom arrow)

mechanical protection (shock absorber), helps maintain a stable chemical environment, nutrient transport and waste removal

what are the functions of CSF

lateral ventricles

first step of CSF flow pathway

interventricular foramina

second step of CSF flow pathway

third ventricle

third step of CSF flow pathway

cerebral aqueduct

fourth step of CSF flow pathway

fourth ventricle

fifth step of CSF flow pathway

median and lateral apertures

sixth step of CSF flow pathway

subarachnoid space around brain and spinal cord

seventh step of CSF flow pathway

passes through arachnoid granulations

eigth step of CSF flow pathway

drains into dural venous sinuses, mainly the superior sagittal sinus

ninth step of CSF flow pathway

arachnoid granulations

how is CSF reabsorbed into the venous system

dural venous sinuses

large venous channels within the dura mater; found between periosteal and meningeal layers of the dura mater; collect blood from cerebral veins and receive CSF; eventually drains into the internal jugular veins

association tracts

connect cortical areas within the same hemisphere

short

_____ fibers connect adjacent gyri (U-fibers)

long

_____ fibers connect more distant cortical regions, often in different lobes

commissural tracts

connect cortical regions across the two cerebral hemispheres, often corresponding regions; allow communication between the left and right sides of the brain

corpus callosum

largest commissural fiber bundle

projection tracts

connect the cerebral cortex with lower brain centers and the spinal cord; carry ascending sensory and descending motor signals

thalamus

lies superior to the brainstem and forms the lateral walls of the third ventricle; major relay station for most sensory information traveling to the cerebral cortex; relays motor information from the cerebellum and basal nuclei to motor areas of the cerebral cortex

epithalamus

contains the pineal gland

hypothalamus

inferior to the thalamus; forms the floor of the third ventricle; maintains homeostasis; regulates autonomic nervous system activity; regulates body temperature, hunger, thirst, and circadian rhythm; regulates endocrine function through the pituitary gland