L12: Forebrain

What are the major subdivisions of the brain?

Cerebrum, cerebellum, and brainstem

What is the prosencephalon?

The embryonic forebrain

What are functions of the cerebrum (5)?

Higher cognitive function, conscious perception, voluntary movement, memory, and language

What is the forebrain made of?

Cerebrum and diencephalon

What is the diencephalon made of?

Thalamus, hypothalamus, and epithalamus

What are functions of the diencephalon (3)?

Sensory relay, homeostasis, and autonomic + endocrine regulation

Where is CSF filled space underneath?

Arachnoid mater

What is the falx cerebri?

A fold of dura mater that separates the two cerebral hemispheres

What two layers form the dura mater?

Periosteal dura and meningeal dura

What is gray matter in charge of?

Processing

What is white matter in charge of?

Communication

What does gray matter form?

Cerebral cortex and basal nuclei

What does grey matter contain?

Neuronal cell bodies, dendrites, synapses, and glial cells

What does white matter contain?

Axons (many surrounded in myelin)

What does white matter form?

Inner region in brain that contains nerve fiber tracts

What are pyramidal neurons?

Primary excitatory neurons of cerebral cortex

What does the cerebrum contain (3)?

1. Cerebral cortex

2. Subcortical white matter

3. Deep nuclei

What is cerebral cortex folded into?

Gyri (peaks) and sulci (valleys)

What is subcortical white matter in charge of?

Axon tracts that connect different regions of the CNS

What is deep nuclei made of?

Collections of gray matter found within white matter

What are primary areas?

First cortical regions involved in processing specific sensory info or generating motor output

What are secondary areas?

Complex processing within a specific sensory or motor system

What are association areas?

Integration info from multiple cortical regions

What are the 5 lobes of the cerebrum?

1. Frontal

2. Parietal

3. Temporal

4. Occipital

5. Insula

What are the functions of the frontal lobe?

1. Voluntary motor control

2. Executive functions

3. Speech production (Broca’s area)

Broca’s Area vs Wernicke’s Area?

Broca’s Area= makes and produces speech and language

Wernicke’s Area= understands spoken and written language

What are the functions of the parietal lobe?

1. Touch, pain, temperature, pressure, vibration, and proprioception

2. Sensory integration and spatial awareness

What are the functions of the temporal lobe?

1. Hearing

2. Language comprehension

3. Memory formation and processing

4. Olfactory processing with limbic structures

What is the function of the insula??

1. Visceral sensory processing

2. Taste perception

3. Emotional awareness and salience processing (prioritizing important stimuli)

4. Interoception (interprets signals)

What is the function of blood-brain barrier?

Restricts uncontrolled entry of toxins, pathogens, and many large or hydrophilic molecules

What is allowed in blood-brain barrier?

Small lipid-soluble molecules

Small nonpolar molecules

Essential substances via transport proteins

What is the function of blood-CSF barrier?

Produces CSF, regulates movement of substances from blood into CSF, and helps maintain chemical stability

What is function of brain-CSF barrier?

Prevents uncontrolled exchange between blood and CSF

What is the blood-brain barrier?

Highly selective permeability barrier that separates blood from brain extracellular fluid

What do tight junctions prevent in BBB?

Paracellular diffusion

Features of most brain capillaries?

Continuous and lacks fenestrations

What are the components of BBB?

1. Capillary endothelial cells tight junctions (main barrier)

2. Basement membrane

3. Pericytes

4. Astrocyte end feet

What do pericytes do?

Multi-functional, but especially important for blood flow and maintenance

What are circumventricular organs (CVOs)?

Specialized midline brain structures that allow direct communication between CNS, CSF, and blood

What do CVOs detect?

Hormones, nutrients, toxins, osmolarity

What is choroid plexus?

fenestrated capillaries covered by choroid plexus epithelial cells

What is the function of choroid plexus?

Produces CSF through selective secretion of ions and water from blood

What is blood-CSF barrier formed by?

Tight junctions between choroid plexus epithelial cell

How does blood-CSF work?

Blood flows through fenestrated capillaries in choroid plexus, allowing substances to enter stroma

What needs to happen before substances can enter CSF?

Substances need to pass through choroid plexus epithelial cells

What is the ventricular system?

A network of interconnected cavities that contain CSF and provide pathway for its movement

What cells line ventricles and central canal?

Ependymal cells— their cilia help move and mix CSF

What are the 3 main ventricles?

1. Lateral (one in each cerebral hemisphere)

2. Third ventricle (between thalami)

3. Fourth ventricle (between brainstem ad cerebellum)

What connects the lateral ventricle to third ventricle?

Interventricular foramina

What connects the 3rd ventricle to 4th ventricle?

Cerebral aqueduct

What are the functions of CSF?

• Shock absorption

• Helps maintain chemical environment

• Nutrient transport and waste removal

What is the CSF flow pathway (9)?

1. Lateral ventricles

2. Interventricular foramina

3. Third ventricle

4. Cerebral aqueduct

5. Fourth ventricle

6. Median and lateral apertures

7. Subarachnoid space around brain + spinal cord

8. Arachnoid granulations

9. Drains into dural venous sinuses

How is CSF reabsorbed into the venous system?

Through arachnoid granulations

Where do arachnoid granulations project into?

Dural venous sinuses and allow CSF to enter venous blood

What are dural venous sinuses?

Large venous channels within the dura mater

Where are dural venous sinuses found?

Between periosteal and meingeal layers of dura mater

What fluids does dural venous sinuses collect?

1. Blood from cerebral veins

2. CSF

Where does dural venous sinuses drain?

Internal jugular veins

How are white matter tracts classified?

According to regions they connect

What are the 3 white matter tracts?

1. Association tracts

2. Commissural tracts

3. Projection tracts

What are association tracts?

Connect cortical areas within the same hemisphere

What are short fibers?

Connect adjacent gyri

What are long fibers?

Connects more distant cortical regions, usually in different lobes

What are commissural tracts?

Connects cortical regions across two hemispheres, often corresponding regions

What tracts allows communication between right and left side?

Commissural tracts

What is the corpus callosum?

Largest commissural fiber bundle

What is anterior commissure?

Nerve fibers that connect right and left tract

What are projection tracts?

Connects cerebral cortex with lower brain centers and spinal cord

Carries ascending sensory and descending motor signals

What does epithalamus contain?

Pineal gland

What does pineal gland do?

Regulates circadian rhythm through secreting melatonin

What is the major relay station for sensory info to cerebral cortex?

Thalamus

Where does thalamus relay motor info from and to?

From cerebellum and basal nuclei to motor areas of cerebral cortex

What is basal nuclei function?

Smooth, fine, purposeful movements

What forms third ventricle?

Hypothalamus

What are functions of hypothalamus?

Regulates endocrine function, autonomic nervous system, temperature, hunger, thirst, circadian rhythm

What forms lateral walls of third ventricle?

Thalamus