BRAIN PART I (A & B): VENTRICLES & MENINGES

Cranial Meninges • Cranial meninges are continuous with spinal meninges • Dura mater:

– inner layer (meningeal layer) – outer layer (endosteal layer) fused to periosteum

• venous sinuses between 2 layers • Arachnoid mater:

– subarachnoid space • Pia mater:

– adhered directly to brain surface Ventricles of the Brain • 4 ventricles

– Lateral ventricles (2) • Septum pellucidum

– Third ventricle • Connects to 4th ventricle via cerebral aqueduct

– Fourth ventricle • Connects to central canal of spinal cord

Cerebral Spinal Fluid • Choroid plexus

– Produces CSF in ventricles • ~500 ml/day

• Arachnoid villi – Reabsorbs CSF, superior cranial region

• Returns CSF to blood in venous sinus • Problems

– Hydrocephaly “watery brain” Cerebral Spinal Fluid Pathway • CSF circulates:

– from choroid plexus – thorough ventricles – to central canal of spinal cord – into subarachnoid space around cauda equina, the spinal cord, and brain – reabsorbed by arachnoid villi around brain

Functions of CSF • Cushions delicate neural structures • Supports brain • Transports nutrients, chemical messengers, and waste products Blood-Brain Barrier • Selective barrier between capillaries and extracellular space around brain • Molecules that can pass freely:

H2O, CO2, O2, glucose Fat soluble substances

• Molecules that are regulated: Ions, pH, neurotransmitters & hormones

• Molecules that do not cross: Large proteins, many medications

Blood Supply to the Brain • Supplies nutrients and oxygen to brain • Delivered by internal carotid arteries and vertebral arteries • Removed from dural sinuses by internal jugular veins

BRAIN PART I (C): VENTRICLE FORMATION

Embryonic Development of the Brain • Neural tube formation

– First month of development – Brain and spinal cord – Lumen becomes ventricles of the brain and central canal if the spinal cord

• Problems – Spina Bifida and Anencephaly

• Detected by alpha (α) fetal protein • Prevented by folic acid

BRAIN

PART II (A): CEREBRUM

Regions of the Brain • Cerebrum • Diencephalon • Brain stem

– Mesencephalon – Pons – Medulla oblongata

• Cerebellum Gray and White Matter • Gray matter:

– in cerebral cortex and basal nuclei

– cell bodies, dendrites, axon terminals

– (where synapses occur) • White matter:

– myelinated axons

Structures of the Cerebrum • Gyri and sulci of neural cortex • Lobes:

– divisions of hemispheres: • Frontal • Parietal • Temporal • Occipital

Divisions of the Cerebrum • Longitudinal fissure:

– separates cerebral hemispheres • Central sulcus divides:

– frontal lobe from parietal lobe • Lateral sulcus divides:

– frontal lobe from temporal lobe • Parieto-occipital sulcus divides:

– parietal lobe from occipital lobe Functional Principles of the Cerebrum • Each cerebral hemisphere receives sensory information from, and sends

motor commands to, the opposite side of body • The 2 hemispheres have different functions although their structures are alike Hemispheric Lateralization • Functional differences between left and right hemispheres • Each cerebral hemisphere performs certain functions not performed by the

opposite hemisphere

Motor and Sensory Areas of the Cortex • Central sulcus separates motor and sensory areas Motor Areas (Frontal Lobe) • Primary motor cortex:

– is the surface of precentral gyrus

• Premotor cortex (somatic motor association area): – coordinates learned

movements • Broca’s area:

– control muscles used in speech

Somatosensory Areas (Parietal Lobe) • Primary somatosensory cortex:

– surface of postcentral gyrus • Proprioception, touch,

pressure, pain, vibration, taste, and temperature

• Somatosensory association area: – Interpretation of sensations

• Gustatory area: – Region for taste sensation

Cerebral Cortex: Sensory Areas • Parietal Lobes: Feel and Taste • Temporal Lobes: Hear and Smell • Occipital Lobes: Vision Hear & Smell (Temporal Lobe) • Primary auditory cortex:

– Receives information about pitch and volume • Auditory association area:

– Interpretation of sounds • Wernicke’s area: (different from text)

– Understanding (interpreting) words we hear • Olfactory cortex:

– Region for smell sensation • Medial (deep) portion of temporal lobe

Vision (Occipital Lobe) • Primary visual cortex:

– Receives information about light, dark, shape, and color • Visual association area:

– Interpretation of visual stimuli • recognition

Higher-Order Thinking • Prefrontal cortex of frontal lobe:

– integrates information from association areas – performs abstract intellectual activities

• predicting consequences of actions • decision making • planning and future comprehension

General Interpretive Area • (NOT called Wernicke’s area ) • Complex, learned reflexes Language Integrative Areas Left side • Broca’s area:

– speech formation (motor control of muscles) • Wernicke’s area:

– speech comprehension (understanding words) Right side • Affective Language area for Broca’s

– put emotion into speech/words • Affective Language area for Wernicke’s

– understand emotion in other’s speech/words

BRAIN PART II (B): ELECTROCENCEPHALOGRAM

What are the origins and significance of the major categories of brain waves seen in an electroencephalogram? Monitoring Brain Activity • Electroencephalogram (EEG):

– patterns of electrical activity are monitored 4 Categories of Brain Waves • Alpha (α) waves:

– healthy, awake adults at rest • Beta (β) waves:

– adults concentrating or mentally stressed • Theta waves:

– found in children – found in intensely frustrated adults – may indicate brain disorder in adults

• Delta waves: – during sleep – found in awake adults with brain damage

BRAIN

PART III (A): DIENCEPHALON

What are the main components of the diencephalon and their functions? The Diencephalon • Epithalamus • Thalamus • Hypothalamus

Epithalamus, Thalamus and Hypothalamus • Epithalamus:

– melatonin secretion via pineal gland • Thalamus:

– relays and processes sensory information • Hypothalamus:

– hormone production – emotion – autonomic function – connected to pituitary gland via infundibulum

The Hypothalamus • Lies below thalamus • Mamillary bodies:

– process olfactory and other sensory information

– control reflex eating movements • Infundibulum:

– connects hypothalamus to pituitary gland

Hypothalamus Functions (some) • Controls ANS functions

– Blood pressure, heart rate, peristalsis, etc. • Emotional response

– Pain, pleasure, fear, rage, libido • Body temperature • Food intake and satiety • Water balance and thirst • Sleep-wake cycle timing • Controls pituitary gland

BRAIN PART III (B): LIMBIC SYSTEM

What are the main components of the limbic system, their locations, and functions?

The Limbic System • Conscious functions of cerebral cortex with autonomic functions of brain stem • Memory storage and retrieval • Connects smell, memory, emotions Specific Parts of the Limbic System • Amygdaloid body:

– interfaces limbic system, cerebrum, sensory systems (smell), emotions • Hippocampus:

– short-term to long-term memory

BRAIN PART IV: BRAIN STEM & CEREBELLUM

Brain Stem • Mesencephalon (midbrain) • Pons • Medulla oblongata Structures of the Mesencephalon • 2 pairs of sensory nuclei (corpora quadrigemina):

– superior colliculus (visual) – inferior colliculus (auditory)

• cerebral peduncles: – nerve fiber bundles – contain:

• descending fibers to cerebellum • motor command fibers

• reticular activating system (allow or block sensory input, see ANS chapter)

The Pons • Nuclei involved with respiration:

– apneustic center, pneumotaxic center – Work with respiratory center in medulla oblongata

The Medulla Oblongata Links spinal cord to brain • Coordinates complex autonomic functions:

– Cardiovascular center • Cardiac (HR, contractility) • Vasomotor (peripheral blood flow)

– Respiratory rhythmicity center • Motor and sensory nerve tracts cross over • Reticular formation

– Alertness Functions of the Cerebellum • Adjusts postural muscles • Fine-tunes conscious and subconscious movements • Pathology:

• Ataxia:ffrom trauma or stroke • disturbs muscle coordination

• Arbor vitae