the brain. some interesting brain facts §brain weighs 3 lbs l however, it is completely immersed in...
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The Brain
Some interesting brain factsBrain weighs 3 lbs
However, it is completely immersed in liquid (cerebrospinal fluid) and, as a result, its effective weight is 3 ounces.
Brain uses 20% of the body’s blood, 20% of its oxygen, and 70% of its glucose.
80% of the human brain is cortex Cortex is virtually absent in fish, reptiles, and birds 1/3 of the cortex is visible Cortex is 1/8” thick and, if spread out flat, is about the size of 1
sheet of newspaper (4 pages of a textbook)Localization of function vs. equipotentiality (mass action)
Broca’s area is in the frontal lobe; when destroyed, patient cannot produce language, but can comprehend language; Broca’s aphasia
Wernicke’s area is in the temporal lobe; when destroyed patient cannot comprehend language, but can produce language; Wernicke’s aphasia
Direction in the brain We are symmetrical around our midline: we have a left arm and a
right arm, a left ear and a right ear, etc. Medial: close to the midline Lateral: farther from the midline; closer to the “side” of the head
Some brain structure terminologySulcus (pl. sulci): any of the shallow grooves separating the
convolutions (bumps, ridges) on the surface of the brainFissure: a very deep groove that, typically, separates major
cortical structuresGyrus (pl. gyri): a convolution (bump, ridge) on the brain
surfaceCommisures: a fiber bundle that interconnects
corresponding regions on each side of the brainWhite matter (mylinated axons) and gray matter (cell
bodies)Cortical structures are specialized parts of the cortex.
Everything else under the cortex, but above the brainstem, is referred to as a subcortical structure.
Some brain organization terminologyHemispheres
The two relatively symmetrical halves of the brain; one on the left and one on the right
Contralaterality The left hemisphere receives sensory input from, and sends motor
messages to, the right side of the body; vice versa for the right hemisphere
Cerebral lateralization (hemispheric specialization) Instances in which one of the hemispheres is more responsible for
a particular cognitive function than the other hemisphere• Left hemisphere specialized for language and analytical thought• Right hemisphere specialized for visual-spatial tasks, music, face
recognition, and emotional statesCerebral dominance
In 90% of human beings, the left hemisphere is specialized for language and these individuals are right-handed; thus, the left hemisphere is said to be the dominant hemisphere
Brainstem Medulla
Vital involuntary functions
Pons Sleep and arousal
Reticular formation
Sleep, arousal, attention
Cerebellum Motor coordination Also involved in
planning, memory, language, and emotion
Another view of the brainstem
Limbic System I: Emotion and motivation
Hypothalamus Regulates
• Glands• Autonomic
system• Eating• Drinking• Sleeping• Sexual activity
Plays a role in emotion
Amygdala Forms learned
associations between objects and emotion, especially fear
Limbic system II: Cognitive functions
Thalamus Sensory relay
station
Hippocampus Formation of new
memories
Basal ganglia Putamen, globus
pallidus, caudate nucleus
Motor behavior Habit learning
Another view of both the limbic system and brain stem
Neglect Syndrome (Hemineglect)
A patient with a stroke in the right hemisphere was asked to copy the model drawings
Typical of neglect syndromes, the left side of the model is almost completely ignored
Primary motor cortex and somatosensory cortex
TheNervousSystem
The Autonomic Nervous System
“Fight or Flight” Restore Calm
The Endocrine System Endocrine system:
Ductless glands that regulate growth, reproduction, metabolism, mood, and some behavior
Hormones: chemical messengers secreted into the bloodstream
Chain of command Hypothalamus
commands the pituitary, which in turn releases hormones that command the other glands to release their hormones
Brain Change Plasticity
A property of the brain that allows it to change as a result of experience, drugs, or injury
Chemical signals guide growing connections. Experience fine-tunes neural connections.
Critical periods Rats in special environments have heavier brains with more synaptic
connections Change in the strength of connections underlies learning
Hebbian learning: “fire together, wire together” Neurogenesis: production of new brain cells in the adult brain Brain reorganization in response to overuse or underuse
Devoting more cortex to information that is pertinent for tasks at hand • Blind people who read Braille have much larger areas of cortex devoted to receiving
input from index fingers than do sighted individuals Brain reorganization in response to brain injury
Much more likely to occur in the young Treatment for brain injury or disease
Neural grafting, using stem cells