Ch 14 Brain Cranial Nerves Protection 1 2

Ch 14 - Brain & Cranial Nerves

Protection 1. 2. Bones of the cranium Cranial meninges- Are continuous with spinal meninges • Protect the brain from cranial trauma (head injury resulting from impact with another object) • 3 layers • Pia mater- Innermost layer, Sticks to surface of brain, Anchored by astrocytes • Arachnoid mater- Subarachnoid space separates arachnoid and pia mater, where CSF circulates • Dura mater • 2 layers – outer layer fused to periosteum of cranial bones • Outer and inner layer separated by gap where fluids and BVs are located • Dural folds: Inward folding of inner layer of dura mater • Provides additional stabilization and support (seatbelt) • Falx celebri (separates cerebral hemispheres) • Tentorium cerebelli (protects cerebellar hemispheres) • Falx cerebelli (separates cerebellar hemispheres) • Dural sinuses: large collecting veins within dural folds, includes superior/inferior sagittal sinus and transverse sinus

Severe Head Injuries • Bleeding in cranial cavity can result in: • Epidural hemorrhage- cranial artery breaks and blood is forced between dura mater and cranial cavity = increase in pressure = distortion of brain tissue = loss of consciousness • Cranial vein break = delay in symptoms; fatal if not treated • Subdural hemorrhage: blood enters inner layer of dura mater from small vein/dural sinuses; delay in symptoms • Pool of blood forming outside of damaged vessel = subdural hematoma

Protection 3. Cerebrospinal Fluid • carries oxygen & glucose • mechanical protection- shock absorber, buoys the brain • chemical protection- accurate amount of ion concentration for signals • produced in choroid plexuses-from ependymal cells • circulation- exchange of nutrients & waste, through ventricles/central canal • CSF reaches subarachnoid space and flows around brain, spinal cord and cauda equina • CSF fluid is absorbed into venous circulation at arachnoid granulations and returns to choroid plexus Hydrocephalus- water on the brain • Occurs when too much reabsorption of CSF in infants • Caused by genetics, trauma, meningitis, tumor, or hemorrhage

Ventricles- filled with CSF • 1& 2. Lateral- each side of cerebrum, separated by septum pellucidum • 3. Third- b/w rt. & left sides of thalamus • 4. Fourth- b/w brain stem & cerebellum

• 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 • Blood–Brain Barrier (BBB) • Isolates CNS neural tissue from general circulation- tight junctions • Only lipid-soluble compounds (O 2, CO 2), steroids, and prostaglandins can diffuse into interstitial fluid of CNS • Have to choose a treatment that will cross, ex: tetracycline cannot break through to treat meningitis • Controlled by Astrocytes • 4 breaks (allows hormones to enter): hypothalamus, pituitary gland, pineal gland, choroid plexus • Blood–CSF Barrier • • Formed by special ependymal cells Surrounds capillaries of choroid plexus Limits movement of compounds transferred Allows chemical composition of blood and CSF to differ

A. Brain Stem • 1. Medulla Oblongata-. • pyramids- bulges, largest motor tracts cross over • Relay to thalamus • sensory & motor b/w brain & s. c. • Motor: muscles of pharynx, neck, back, & viscera of thoracic/peritoneal cavity • Autonomic controls: Reticular Formation-from medulla to midbrain • Cardiovascular center (heart rate, blood vessels) & Respiratory rhythmicity center (respiratory pace, reflexes for vomiting, coughing, sneezing)

Brain Stem 2. Pons • Sensory/Motor: jaw, face, eye muscle & internal ear • Respiration: Apneustic & pneumotaxic- monitors medulla • Link cerebellum w/brain stem, cerebrum, spinal cord

Brain Stem 3. Midbrain/Mesencephalon- elevations • Corpora Quadrigemina: • superior colliculi- movements of eyes, head, & neck in response to vision • inferior colliculi-movements of head & trunk in response to hearing • Red nucleus & Substantia Nigra- subconscious muscle activities (posture), • Reticular Activating System- alert & attentive

Cerebellum- 2 nd largest • cerebellar hemispheres (lobes) & central vermis (separates lobes) • evaluates how well movements are being carried out, makes muscle contractions smooth • posture & balance Peduncles-link to brainstem

Problems with Cerebellum • Ataxia- disturbance in muscular coordination • Inability to sit or stand without assistance • From trauma, stroke, drugs (alcohol)

Diencephalon- integration of sensory with motor 1. Thalamus- relay station • sensory impulses (touch, pain, temp, pressure, proprioception (position)) • Influences emotional state • Projects visual & auditory information • Part of limbic system 2. Epithalamus- roof -Pineal gland- melatonin (day-night cycles) 3. Subthalamus- body movements

Diencephalon 4. Hypothalamus • Subconscious control of skeletal muscle associated with rage, pleaure, pain, & sexual arousal • control of ANS- contraction of smooth & cardiac muscle • Inhibits or stimulates Pituitary gland- hormones (HGH, LH, FSH, TSH(metabolism)), connected by infundibulum • Secretes 2 hormones • ADH-water balance, blood pressure • Oxytocin- smooth muscle contractions of uterus & mammary glands • Satiety (hunger) & thirst centers • body temperature • circadian rhythms- sleep schedule

Limbic system- “emotional brain” Hypothalamus, pituitary, amygdala, and hippocampus Hippocampus-long term memory Amygdala- emotions (fear, aggression, sex & pleasure) Hypothalamus- hunger, thirst, body temp, pleasure

Charles Whitman • engineering student and retired U. S. Marine • 1966 -He killed his wife and mother before going to the top of the University of Texas tower and opened fire on persons crossing the campus and on nearby streets. He ended up killing 16 people and wounded 31, before being killed by police officers. The shooting spree lasted 96 minutes. • Post-mortem revealed a brain tumor near his amygdala. • http: //www. youtube. com/watch? v=Tt OQn. M 3 LQk. E

Cerebrum- largest • “seat of intelligence”- read, write, speak, memory, imagination • Corpus callosum- division between the hemispheres • divided by lobes-parts of skull bones • Basal ganglia- control automatic movements of skeletal muscle, (swinging arms while walking, laughing), muscle tone

Cerebral Features: • Gyri – Elevated ridges “winding” around the brain. • Sulci – Small grooves dividing the gyri – Central Sulcus (Fissure of Rolando) – Divides the Frontal Lobe from the Parietal Lobe • Fissures – Deep grooves, generally dividing large regions/lobes of the brain – Longitudinal Fissure – Divides the two Cerebral Hemispheres – Transverse Fissure – Separates the Cerebrum from the Cerebellum – Sylvian/Lateral Fissure – Divides the Temporal Lobe from the Frontal and Parietal Lobes

Gyri (ridge) Sulci (groove) Fissure (deep groove) http: //williamcalvin. com/Brain. For. All. Seasons/img/bonobo. LH-human. LH-via. TWD. gif

Specific Sulci/Fissures: Central Sulcus Longitudinal Fissure Sylvian/Lateral Fissure Transverse Fissure

Lobes of the Brain (4) • Frontal • Parietal • Occipital • Temporal * Note: Occasionally, the Insula is considered the fifth lobe. It is located deep to the Temporal Lobe.

The lobes of the cerebral hemispheres Planning, decision making speech Sensory Auditory Vision

Lobes of the Brain - Frontal • The Frontal Lobe of the brain is located deep to the Frontal Bone of the skull. • It plays an integral role in the following functions/actions: - Memory Formation - Emotions - Decision Making/Reasoning - Personality Modified from: http: //www. bioon. com/book/biology/whole/image/1/1 -

Phineas Gage • 1848 - Working on Railroad • Tamping iron sent through skull • Quick recovery but never the same • Before: capable, efficient, best foreman • After: anti-social, liar, grossly profane – WHY? ? • Joins the circus & died 12 years later http: //www. youtube. com/watch? v=9 QXI_Bxl. Y 7 M

Frontal Lobe - Cortical Regions • Primary Motor Cortex (Precentral Gyrus) – Cortical site involved with controlling movements of the body. • Broca’s Area – Controls facial neurons, speech, and language comprehension. Located on Left Frontal Lobe. – Broca’s Aphasia – Results in the ability to comprehend speech, but the decreased motor ability (or inability) to speak and form words. • Orbitofrontal Cortex – Site of Frontal Lobotomies * Desired Effects: - Diminished Rage - Decreased Aggression - Poor Emotional Responses * Possible Side Effects: - Epilepsy - Poor Emotional Responses - Perseveration (Uncontrolled, repetitive actions, gestures, or words) • Olfactory Bulb - Cranial Nerve I, Responsible for sensation of Smell

Primary Motor Cortex/ Precentral Gyrus Broca’s Area Orbitofrontal Cortex Olfactory Bulb Regions Modified from: http: //www. bioon. com/book/biology/whole/image/1/1 -8. tif. jpg

Lobes of the Brain - Parietal Lobe • The Parietal Lobe of the brain is located deep to the Parietal Bone of the skull. • It plays a major role in the following functions/actions: - Senses and integrates sensation(s) - Spatial awareness and perception (Proprioception - Awareness of body/ body parts in space and in relation to each other)

Parietal Lobe - Cortical Regions • Primary Somatosensory Cortex (Postcentral Gyrus) – Site involved with processing of tactile and proprioceptive information. • Somatosensory Association Cortex - Assists with the integration and interpretation of sensations relative to body position and orientation in space. May assist with visuo-motor coordination. • Primary Gustatory Cortex – Primary site involved with the interpretation of the sensation of Taste.

Primary Somatosensory Cortex/ Postcentral Gyrus Somatosensory Association Cortex Primary Gustatory Cortex Modified from: http: //www. bioon. com/book/biology/whole/image/1/1 -8. tif. jpg

Lobes of the Brain – Occipital Lobe • The Occipital Lobe of the Brain is located deep to the Occipital Bone of the Skull. • Its primary function is the processing, integration, interpretation, etc. of VISION and visual stimuli.

Occipital Lobe – Cortical Regions • Primary Visual Cortex – This is the primary area of the brain responsible for sight -recognition of size, color, light, motion, dimensions, etc. • Visual Association Area – Interprets information acquired through the primary visual cortex.

Primary Visual Cortex Visual Association Area

Lobes of the Brain – Temporal Lobe • The Temporal Lobes are located on the sides of the brain, deep to the Temporal Bones of the skull. • They play an integral role in the following functions: - Hearing - Organization/Comprehension of language - Information Retrieval (Memory and Memory Formation)

Temporal Lobe – Cortical Regions • Primary Auditory Cortex – Responsible for hearing • Primary Olfactory Cortex – Interprets the sense of smell once it reaches the cortex via the olfactory bulbs. (Not visible on the superficial cortex) • Wernicke’s Area – Language comprehension. Located on the Left Temporal Lobe. - Wernicke’s Aphasia – Language comprehension is inhibited. Words and sentences are not clearly understood, and sentence formation may be inhibited or non-sensical.

Primary Auditory Cortex Wernike’s Area Primary Olfactory Cortex (Deep) Conducted from Olfactory Bulb Modified from: http: //www. bioon. com/book/biology/whole/image/1/1 -8. tif. jpg Regions

• Arcuate Fasciculus - A white matter tract that connects Broca’s Area and Wernicke’s Area through the Temporal, Parietal and Frontal Lobes. Allows for coordinated, comprehensible speech. Damage may result in: - Conduction Aphasia - Where auditory comprehension and speech articulation are preserved, but people find it difficult to repeat heard speech. Modified from: http: //www. bioon. com/book/biology/whole/image/1/1 -8. tif. jpg

Fusiform gyrus in Temporal Lobe 1. processing of color information 2. face and body recognition 3. word recognition

The Cerebral Cortex • Frontal (Forehead to top) Motor Cortex • Parietal (Top to rear) Sensory Cortex • Occipital (Back) Visual Cortex • Temporal (Above ears) Auditory Cortex

Sensory Areas – Sensory Homunculus

Hemispheric Lateralization Left • Reading, writing, math • Decision making • Speech & language • Detail • Literal meaning Right • Senses • Recognition (faces, voice) • Overall picture • Spatial perception • Emotional • Musical

Contra-lateral division of labor • Right hemisphere controls left side of body and visual field • Left hemisphere controls right side of body and visual field

Problems with the Brain • Contusion- bruise • Concussion- temporary loss of consciousness & some amnesia • Aneurysm- balloon of vessel • Embolism-something carried to a spot it shouldn’t be (fat) • Stroke-lack of brain functions because of cut off blood supply • Alzheimer’s- loss of Ach, causes plaques • Apraxia- don’t know what to do with something • Ex: comb hair with a fork • Parkinson’s- decrease in dopamaine • resting tremors, loss of voluntary movement

Imaging- Electroencephalogram (EEG) • Monitors brain activity • Typical brain waves • Alpha waves: occur in brains of healthy, awake adults resting with eyes close • Beta waves: occur during intense concentration, stress, psychological tension • Theta waves: occur during sleep in normal adults, children, frustrated adults • Delta waves: seen during deep sleep, infants and awake adults when tumor, vascular blockage, inflammation has caused damage Seizure • Is a temporary cerebral disorder • Changes the electroencephalogram • Symptoms depend on regions affected

Imaging • MRI- Radio waves & magnetic fields to distinguish brain tissue • Positron Emission Tomography/PET- 3 D image of functional processes in the brain, (not just the structure) • uses glucose to develop a visual display of brain activity https: //www. youtube. com/watch? v=qab. Tdk 928 e. Q&list=PLw 2 f LCAn. U 7 j 7 Xr_9 sl 6 XEGW 2 Myyfw. M 0 Kb&index=1

• Brains from Humans • https: //www. youtube. com/watch? v=_3 g. KVOe. Xpx. U&list=UUdofq 4 h. H b. T 3 ZDzg. YUqs. Dd 1 A&index=36 • https: //www. youtube. com/watch? v=b. N 8 o. YVilps&index=34&list=UUdofq 4 h. Hb. T 3 ZDzg. YUqs. Dd 1 A

Sheep Brain Dissection • https: //www. youtube. com/watch? v=YRHS 0 DSox 8 Y