The Brain

What regions of the brain makes up the brainstem?

Midbrain

Pons

Medulla oblongata

Cerebrum

Largest part of adult brain

• conscious thoughts, intellect, memory

Cerebral cortex

Surface layer of gray matter of cerebrum

• Gyrus/ gyri- elevations that increase surface area

• Gyri separated by shallow depressions (sulcus/sulci) and deep grooves (fissures)

Diencephalon

Located under cerebrum and cerebellum

• thalamus

• Hypothalamus

• Epithalamus

Thalamus

Relays and processes sensory info

Hypothalamus

Involved with emotions, autonomic functions, and hormone production

Epithalamus

Involved with melatonin

Pituitary gland

Connected to hypothalamus via infundibulum

Brainstem

Relays info between spinal cord and cerebellum and cerebrum

Midbrain

Processes sight and sound

Pons

Connects cerebellum to brainstem

Connects tracts, relay centers, and nuclei for somatic and visceral motor control

Medulla oblongata

Connects brain to spinal cord

• inferior portion has a narrow central canal

• Regulates autonomic functions- HR, BP, and digestion

Cerebellum

Second largest part of brain

Coordinates repetitive movements

Covered by gray matter (cerebellar cortex)

Embryonic development

Neural tube- develops into CNS

Prosencephalon- (forebrain)

• telencephalon

• Diencephalon

Mesencephalon- (midbrain)

Rhombencephalon- (hindbrain)

• metencephalon

• Myelencephalon

Telecephalon

Forms cerebrum and lateral ventricles

Diencephalon

Diencephalon and third ventricle

Mesencephalon

Midbrain and cerebral aqueduct

Metencephalon

Forms cerebellum, pons, and upper fourth ventricle

Myelencephalon

Forms medulla oblongata and lower fourth ventricle

Neurocoel

Neural tube encloses neurocoel.

Expands to form chambers (ventricles) lined with ependymal cells

Ventricles of the Brain

Cranial Meninges

• Dura mater

• Arachnoid mater

• Pia mater

Dura mater

• meningeal cranial dura- inner fibrous layer

• Periosteal cranial dura- outer fibrous layer

Dural folds

Extensions of meningeal dura into cranial cavity

Contains collecting veins called dural venous sinuses that drain deoxygenated blood and CSF into internal jugular veins

Flax cerebrum

Separates cerebral hemispheres

• Contains superior sagittal sinus and inferior sagittal sinus

Tentorium cerebelli

Separates cerebrum and the cerebellum

• contains transverse sinus and straight sinus

Flax cerebelli

Separates the cerebellar hemispheres

• contains occipital sinus

Arachnoid mater

Covers brain

Attaches to dura mater

Separated by subdural space

Subarachnoid space

Between arachnoid mater and pia mater

CSF fills the space

Pia mater

Attached to brain surface by astrocytes

Choroid plexus

Produces CSF

Removes waste products from CSF

Arachnoid vili

Extensions of arachnoid membrane through meningeal layer of dura mater into superior sagittal sinus

Arachnoid granulations

Large clusters of arachnoid vili

• absorbs CSF into venous circulation

Internal jugular veins and vertebral veins

Removes blood from dural venous sinuses

Blood Brain Barrier

Isolates CNS from circulation

Formed by tight junctions

O2, CO2, steroids, prostaglandins, small alcohols can diffuse

Astrocytes regulate BBB by releasing chemicals that control the permeability of endothelium

Blood CSF barrier

Formed by ependymal cells connected by tight junctions

Gray matter in Cerebrum

In cerebral cortex and basal nuclei

White matter in cerebrum

Seep to cerebral cortex and around basal nuclei

Central sulus

Divides the anterior frontal lobe from the posterior parietal lobe

Precentral gyrus

Forms anterior border of central sulcus of frontal lobe

• directs voluntary movements

• Primary motor cortex is the surface

• → pyramidal cells are the neurons of the primary motor cortex

Postcentral gyrus

Forms posterior border of central sulcus of parietal lobe

• receives somatosensory info (touch, pressure, pain, vibration, taste, temp)

• Primary somatosensory cortex- surface of postcentral gyrus

Lateral sulcus

Separates the frontal lobe form temporal lobe

Insula of Cortex

Lies medial to lateral sulcus

Parieto-occipital sulcus

Separates parietal lobe from occipital lobe

Premotor cortex

Anterior to the precentral gyrus

• Controls learned, repetitious, patterned motor skills

• Also called somatic motor association area

Prefrontal cortex

Most complicated

• coordinates info from sensory association areas

• Performs abstract intellectual activities

• Intellect, recall, personality

Broca’s Area

Anterior to inferior region of premotor area

Directs muscles of tongue

Speech area

Primary somatosensory cortex

Receives somatic sensory info and is capable of spatial discrimination

Wernicke’s area

Understanding written and spoken language

Left hemisphere

Brain regions

Limbic System

Involved in emotional state, linking intellectual functions with unconscious and autonomic functions of brain stem and memory storage

What is the limbic lobe?

Cerebrum

• cingulate gyrus

• Dentate gyrus- hyppocampus storage and retrieval of long term memory

• Parahyppocampus gyrus

• Amygdala

What is in the Diencephalon?

Thalamus and hypothalamus

What is hemispheric lateralization?

Functional differences between the left and right hemispheres

What is the left hemisphere responsible for?

Reading, writing, math, logic

What is the right hemisphere responsible for?

Analyzes sensory info

Recognizes faces and voices

Insight, visual-spatial skills, artistic skills

What is an EEG?

Observes electrical patterns of brain

Alpha waves

Normal resting

Beta waves

Accompany intense concentration

Theta waves

Seen in children and frustrated adults

Delta waves

Occurs in deep sleep

Association fibers

Interconnect cortical areas within the same hemisphere

Arcuate fibers

Interconnect gyri within a lobe

Short fibers

Longitudinal fascicle

Interconnects the frontal lobes with other cerebral lobes

Longer bundles

Commissural fibers

White matter of Bands of fibers connecting the two hemispheres

Corpus callosum

White matter that Connects the two hemispheres

Anterior commissaries

White matter that connects hemispheres

Posterior commissure

White matter that connects the hemispheres

Projection fibers

White matter that links cerebral cortex to Diencephalon, brainstem, cerebellum, and spinal cord.

Passes through Diencephalon

Internal capsule

All ascending and descending projection fibers

Basal nuclei

Masses of gray matter embedded in the white matter of the cerebrum

Directs subconscious activities

What are the parts of the basal nuclei?

• caudate nucleus

• Lentiform nucleus→ putamen and globes pallidus

• Claustrum

What causes the symptoms of Parkinson’s?

Increased activity of basal nuclei

What is the function of the basal nuclei?

Subconscious control of skeletal muscle and coordination of learned movement patterns (walking, lifting)

What are the parts of the Diencephalon?

Epithalamus, thalamus, hypothalamus

What is the function of the Epithalamus?

Contains pineal gland which secretes melatonin for sleep

What is the function of the thalamus?

Relays ascending sensory info

Where is the third ventricle located?

Separates left and right sides of thalamus

What are the parts of hypothalamus?

• mammillary bodies

• Infundibulum

• Tuber cinereum

What do mammillary bodies do?

Controls reflex eating movements (licking, swallowing)

What does the infundibulum do?

Connects hypothalamus to pituitary gland

What does the tuber cinereum do?

Lies between infundibulum and mammillary bodies

Produces hormones that affect pituitary gland

What does the hypothalamus secrete?

ADH and oxytocin

Regulates body temp

Control satiety and thirst

What are the corpora quadrigemina?

Two pairs of sensory nuclei in midbrain

Superior colliculi function

Receives visual input from lateral geniculate bodies of thalamus

Inferior colliculi function

Receives auditory signals form pons and medulla oblongata and passes through medial geniculate body of thalamus

Red nucleus function

Receives info from cerebrum and cerebellum and is responsible for subconscious muscle adjustments

Substantial migration function

Releases dopamine and inhibits activity of basal nuclei

Cerebral peduncles

Contains descending fibers to cerebellum and motor command fibers

RAS increases alertness and attention

Pons contains

Motor and sensory nuclei of cranial nerves V, VI, VII, VIII

• involved in respiration→ apneustic center and pneumotaxic center: processes info in respiratory rhythm centers of medulla oblongata

Transverse pontine fibers

Axons link nuclei of pons with opposite cerebellar hemisphere

Reticular formation

Gray and white matter with embedded nuclei

Regulates autonomic functions

Medulla oblongata cranial nerves

VIII, IX, X, XI, XII

Gracile nucleus and cuneate nucleus

Pass somatic info to thalamus

Decussation of pyramids

Crossing over site of gracile nucleus and cuneate nucleus

Solitary nuclei

Receives visceral sensory info from spinal and cranial nerves

Inferior olivary complex

Relay info to the cerebellar cortex

Folia

Folds in cerebellar cortex

Anterior and posterior lobes of cerebellum is separated by

Primary fissure

Vermis of the cerebellum

Separates cerebellar hemispheres at midline