“i am a brain, watson. the rest of me is a mere appendix.” ― arthur conan doyle, the adventure...
TRANSCRIPT
“I am a brain, Watson. The rest of me is a mere appendix.”
― Arthur Conan Doyle, The Adventure of the Mazarin Stone
NEUROANATOMYThe Form of the Brain
Directional terms
posteriormedial
lateral
superior
inferioranterior
• Skin• Periosteum = leathery covering of cranial bones
• Cranium = bone w/fixed joints
• Meninges
Protecting The Brain
• Dura mater = tough fibrous tissue covering the brain.• Contains blood vessels that nourish the brain.• Holds in the cerebral-spinal fluid (CSF)
• Arachnoid Space • Pia mater
Meninges
Sub- v. Epidural Hematomas
• Epidural = Inflammation between dura and skull
• Subdural = between arachnoid space and dura
Cerebro-Spinal Fluid (CSF)
• CSF = plasma ultrafiltrate that bathes and protects the CNS.
• Produced by the choroid plexus (tissue in the lateral ventricles & 4th ventricle)
• Hydrocephalus = Inflammation resulting from obstruction of the aqueduct connecting the third & fourth ventricles
Major Regions of the Brain
Cerebrum
Cerebellum
Spinal cord
Cerebral Cortex
• The outer layer of grey matter of the cerebrum
• Grey matter consists of soma (cell bodies)and unmyelinated axons
• White matter consists of myelinated axons
Cerebral Cortex
Axons
Soma
Cerebral Topography
• Gyri – Elevated ridges “winding” around the brain• Cingulate Gyrus – Just above the corpus callossum
• Sulci – Small grooves dividing the gyri• Central Sulcus – 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
Longitudinal Fissure
Transverse Fissure
Sylvian/Lateral Fissure
Central Sulcus
http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg http://www.dalbsoutss.eq.edu.au/Sheepbrains_Me/human_brain.gif
Specific Sulci/Fissures:
Cerebral Lobes
• Frontal • Parietal • Temporal • Occipital
Frontal Lobe• The frontal lobe is located deep to the frontal bone.
• Functions/actions:• Memory formation• Emotions• Decision Making/Reasoning• Personality
• Generally, the left side of the brain controls the right side of the body
Primary Motor Cortex/ Precentral Gyrus
Broca’s Area
Orbitofrontal Cortex
Olfactory Bulb
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Frontal Lobe – Cortical Regions
• Controls movements of the body
• Betz cells alpha motor neurons (spinal cord) muscle fibers
• The motor cortex contains a rough “map” of the body, with controls for the toes (top) to the mouth (bottom) in overlapping regions
Primary Motor Cortex
Motor Homunculus• Proportional model of organs to density of neural tissue devoted to said muscle/structure
Broca’s v. Wernicke’s Area
• BROCA =Located on the right frontal lobe
• Controls facial neurons, speech, and language comprehension
• WERNICKE = located on left temporal lobe
• Controls content of speech and language development
Orbitofrontal Cortex
• One of the least explored and understood regions of the cerebral cortex
• Located just above the orbits (eye sockets), in the frontal lobe
• Involved in adaptive learning and “personality” of an individual
Phineas Gage
Olfactory Bulb
• The most rostral (forward) part of the brain in most vertebrates, but is on the inferior side of the brain in humans
• Olfactory receptor neurons in the nasal cavity receive the smells, and transmit them to the brain
Parietal Lobe
• Where? The parietal lobe of the brain is located deep to the parietal bone of the skull
• What Functions?• Sensory Integration• Proprioception: aware- ness of body/body parts in space and in relation to each other)
Primary Somatosensory Cortex/ Postcentral Gyrus
Primary Gustatory Cortex
Somatosensory Association Cortex
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Parietal Lobe – Cortical Regions
Somatosensory Cortex
• Processing of tactile, temperature, nociceptive (pain), and proprioceptive (spatial) information
• Neurons are also organized according to the type of sensation to which they respond (i.e. pressure, temperature, pain)
Somatosensory Homunculus
• This model shows what a man's body would look like if each part grew in proportion to the area of the cortex of the brain concerned with its sensory perception
Parietal Lobe – Other Cortical Regions
• Somatosensory Association Cortex• Assists with integration/interpretation of sensations relative to body position and orientation in space (kinesthetic awareness) and hand-eye coordination
• Primary Gustatory Cortex• Primary site of interpretation of gustation/taste
Occipital Lobe
• The occipital lobe is located deep to the occipital bone of the skull
• Functions:• Processing, integration, interpretation of vision and visual stimuli
Primary Visual Cortex
Visual Association Area
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Occipital Lobe – Cortical Regions
Occipital Lobe – Cortical Regions• Primary Visual Cortex
• Primary area of brain responsible for sight.• Receives information via the optic nerve
• Visual Association Area• Interprets information acquired through the primary visual cortex
Temporal Lobe
• The temporal lobes are located on the sides of the brain, deep to the temporal bones of the skull
• Functions:• Hearing• Organization/ comprehension of language
• Information retrieval (memory and memory retrieval)
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
Temporal Lobe-
Cortical Regions
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
• Wernicke’s Area• Located on the left temporal lobe• Language comprehension
Cerebellum
• “Little brain”, located inferior
to the cerebrum• Functions:
• Motor control – doesn’t originate movement (i.e. primary motor cortex) but contributes to motor programs
• Attention & language (?)• Regulating fear and pleasure responses (?)
• Composed of highly regularly arranged Purkinje cells (large neurons with many dendritic spines) and Granule cells (small neurons)
Brainstem
• The posterior region of the brain• Continuous tissue with the spinal column• All information relayed between the body and brain must pass through the brainstem
Segments of Brainstem
• The brainstem is composed of three segments:• Medulla oblongata• Pons• Midbrain
Medulla Oblongata
• Lower half of the brainstem• Contains autonomic centers re:
• Cardiac function• Respiratory function• Vomiting• Vasomotor
Pons
• Relay action potentials from the forebrain to the cerebellum
• Deals primarily with:
• Sleep• Respiration• Swallowing• Bladder
control• Hearing• Posture
• Equilibrium• Taste• Eye movement• Facial expressions • Facial sensation
Midbrain
• Located superior to the pons• Associated with:
• Vision• Hearing• Motor Control• Sleep/awake• Arousal (alertness)• Temperature regulation
Limbic System
• Associated with higher order behaviors• Hippocampus: corticosteroid production, spatial relations; long term memory
• Amygdala: reward, fear, mating, response to stress• Limbic cortex: judgment, insight, motivation, mood, • Fornix: relay signals from hippocampus to hypothalamus