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Nervous System
Consists of all the nerve cells. It is the body's speed, electrochemical communication system
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Central Nervous System (CNS)
brain and spinal cord
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Peripheral nervous system (PNS)
the sensory and motor neurons that connect the CNS to the rest of the body
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Nerves
consist of neural "cable"containing many axons. They are part of the PNS and connect muscles, glands, and sense organs to the CNS
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Neurons
Basic unit of the nervous system. Allow communication between the brain and sensory organs, internal organs, and muscles.
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Sensory Neurons (Afferent)
Conduct sensory impulses from eyes, ears, and other sense organs to the CNS.
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Motor Neurons(Efferent)
Conduct motor impulse out from the CNS to muscles and organs
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Interneurons
Connect one neuron to an other
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Cell Body
the cell's life support center
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Dendrites
receive messages from other cells
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Axons
passes messages away fro the cell body to other neurons, muscles, or glands
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Neural impulse
action potential electrical signal traveling down teh axon
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Terminal branches of axon
from junction with other cells
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Myelin sheath
covers the axon of some neurons and helps speed neural impulses
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How neurons communicate signals
Electrochemical Process
Electrical-conduction of impulse within neuron
Chemical- transmission of impulse between neurons
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Conduction of Impulse
Threshold
each neuron receives excitatory and inhibitory signals from many neurons. When the excitatory signals minus the inhibitory signals exceed a minimum intensity(threshold) the neurons fires and action potential i.e. electrical impulse passes down the axon with constant intensity
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Conduction of impulse
re polarization
once fires, resting potential returns
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Conduction of impulse
Absolute Refractory Period
brief period of time after firing when neuron won't fire
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Conduction of impulse
all or none law
Neuron either firing with full intensity of resting (resting potential.) Increases in intensity of stimulation don't cause stronger impulse but lead to more rapid firing or to activation of more neurons.
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conduction of impulse
relative refractory period
period of time after firing when neuron will only fire in response to strong stimulation
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Transmission of message
Synapse
small gap between axon of one neuron and the dendrite of another through which chemical messages are transmitted
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transmission of message
Axon terminal
The end of the axon. Contains synaptic vesicles.
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transmission of message
Action potential
causes vesicle to open and release neurotransmitters(chemicals that have specific different shapes) which travel across synapse and bind to matching receptor sites on receiving neuron, thereby influencing it to generate an action potential
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Reuptake
Neurotransmitters in the synapse are reabsorbed into the sending neurons through the process of reuptake.
This process applies the brakes on neurotransmitter action.
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Lock and key Mechanism
Neurotransmitters bind to the receptors of the receiving neuron in a key-lock mechanism
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How some drugs work
Agonist neurotransmitter
the agonist molecule excites. It is similar enough in structure to the neurotransmitter molecule that it mimics its effects on the receiving neuron.
Morphine- mimics the actions of endorphins by stimulating receptors in brain areas involved in mood and pain sensations
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how some drugs work
antagonist neurotransmitter
this molecule inhibits. it has a structure similar enough to the neurotransmitter to occupy its receptor site and block its action, but not similar enough to stimulate the receptor.
curare poisoning- paralyzes its victims by blocking ach receptors involved in muscle movement
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Dopamine pathways
involved in movement, attention, emotion, and learning.
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serotonin pathways
involved with mood, sleep, hunger, and arousal regulation
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Acetylcholine
Enables muscle action, learning, and memory
Alzheimer's desease, ach producing neurons deteriorate
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dopamine
influences movement, learning, attention, and emotion
excess dopamine receptor activity linked to schizophrenia
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serotonine
affects mood, hunger, sleep, and arousal
undersupply linked to depression prozac and some other antidepressant drugs raise serotonin levels
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Norepinephrine
helps control alertness and arousal
undersupply can depress mood
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GABA(gamma-aminobutyric acid)
a major inhibitory neurotransmitter
undersupply linked to seizures, tremors, and insomnia
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Glutamate
a major excitatory neurotransmitter involved in memory
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Endocrine System
The body's slow chemical communication system
Consists of glands distributed around body that release hormones into bloodstream.
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hormones
chemical messengers that influence behavior. ex. epinephrine (adrenaline) increases heart rate & blood pressure during emergency
- Hormones travel longer distances and their effects slower & more prolonged than neurotransmitters (some chemicals can be both.)
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hypothalamus
brain region controlling the pituitary gland
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thyroid gland
affects metabolism
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adrenal glands
sit above kidneys, secrete hormones (epinephrine and norepinephrine) that help arouse the body in times of stress.
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testis
secretes male sex hormones
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ovary
secretes female hormones
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pituitary gland
- secretes many different hormones, some of which affect other glands
- regulates growth.
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parathyroid
help regulate teh level of calcium in the blood
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pancreas
regulates the level of sugar in the blood
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The spinal cord and reflexes
- 1. information is carried from skin receptors along a sensory neuron to the spinal cord. From here it is passes via interneurons to motor neurons that lead to muscles in the hand and arm
- 2. this reflex involves or spinal cord, the hand jerks away from candle flame even before informing it about the event has reached the point of causing the experience of pain
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Computerized Axial Tomography (CT or CAT scan)
a series of x-ray photographs taken from different angles and combined by computer into a 3d composite representation of the brain
- used to detect tumors and stroke damage
- CTs have been useful in identifying schizophrenia patients. In these patients' brains: the ventricles (fluid- filled open spaces), are significantly larger than in normal individuals, which means that they have less brain tissue to process cognitive functions.
- Instead of a flat, two-dimensional X-ray picture, CT scanners produce a series of successive images. Taken as the patient, lying down, moves through a scanning ring, these "slices" can be combined to create the illusion of a 3-D image.
- Detects such things as tumors & stroke damage.
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Electroencephalogram(EEG)
- - An amplified recording of the electrical waves sweeping across the brain’s surface, measured by electrodes placed on the scalp.
- - Brain activity is plotted as a line (Brain wave).
- - Used in sleep and other kinds of brain research.
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MRI Scan Magnetic Resonance Imaging
- - Uses magnetic fields and radio waves to produce computer-generated images that distinguish among different types of brain tissue.
- - Allows us to see structures within the brain - Used for diagnosing tumors and epilepsy.
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FMR
- measures brain function. It tracks brain activity by monitoring changes in how much oxygen the brain cells are consuming. That serves as an indicator of how much blood is flowing to various brain regions, which in turn shows how active the neurons are.
- •Typically, fMR subjects are placed in an MRI machine and asked to perform a mental task such as remembering and repeating words presented to them.
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Postion Emission tomography PET
- - A visual display of brain metabolic activity.
- - Detects where a radioactive form of glucose travels while the brain performs a given task.
- - Useful for identifying changes in mental activity & in blood flow.
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Brain Lessons
- A naturally or experimentally caused destruction of brain tissue.
- Researchers study change in behaviors after such destruction.
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Reticular Formation
Brain stem
Attention, arousal, wakefulness
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Medulla
Brain stem
Heartbeat, breathing, digestion, and vital reflexes (sneezing, vomiting, swallowing, coughing, etc.)
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Thalamus
Brain stem
Sensory hub. Processes most sensory info to sensory areas in cortex, and transmits replies to cerebellum and medulla.
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Cerebellum
- Coordination
- The “little brain” attached to the rear of the brainstem
- Helps coordinate voluntary movements and balance, ex. playing the piano, kicking, throwing
- Also coordinates cognitive processes
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The Limbic System: Emotions & Drives
Doughnut-shaped system of neural structures at border of brainstem and cerebrum
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Hypo (i.e. below) thalamus
- regulates maintenance activities (ex. sleep, body temperature, hunger, thirst, circadian rhythm, salt & water balance) and sexual behavior.
- Helps govern hormone secretion by endocrine system via pituitary gland.
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Amygdala
involved in emotional responding (fear, anger). Reads emotional significance of input from all senses. Output influences such functions as heart rate, adrenaline release. If damaged, hard to identify emotion from facial expressions
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Hippocampus
involved in forming new memories
As the teens got older, the center of activity shifted more toward the frontal cortex which governs reason and analysis and away from the cruder amygdala which governs emotional “gut” reactions
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Lateralization
- Two Cerebral Hemispheres identical in appearance & work together but have somewhat differing
- functions
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Right hemisphere
Nonverbal, spatial, perceptual, holistic & emotional functions.
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Left hemisphere
Linguistic,mathematical, analytical functions.
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Contra-lateral Arrangement
cross over in spinal cord
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Corpus Callosum
: connects 2 hemispheres • Lateralization is never 100%
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Cerebral Cortex
- Most advanced, complex functions
- Outer wrinkled part. Body’s ultimate control center.
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corpus callosum
axon fibers connecting the two cerebral hemispheres
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thalamus
relays messages between lower brain centers and cerebral cortex
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hypothalamus
- controls maintenance functions such as eating
- helps govern endocrine system
- linked to emotion and reward
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pituitary
master endocrine gland
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reticular formation
helps control arousal
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medulla
controls hearth beat and breathing
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spinal cord
- pathway for neural fibers
- traveling to and from brain
- controls simple reflexes
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cerebellum
coordinates voluntary movements and balance and supports memories of such
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cerbral cortex
ultimate control and information processing center
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amygdala
linked to emotion
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hippocampus
linked to memory
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Splitting the Brain
- A procedure in which the two hemispheres of the
- brain are isolated by cutting the connecting fibers (mainly those of the corpus callosum) between them.
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Split brain patients
With the corpus callosum severed, objects (apple) presented in the right visual field can be named. Objects (pencil) in the left visual field cannot.
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The four lobes of the cortex
Each brain hemisphere is divided into 4 lobes separated by prominent fissures
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Frontal Lobe
movement (motor cortex) & thinking
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Parietal Lobe
Touch & movement sensations (sensory cortex)
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Temporal Lobes
hearing (auditory cortex), emotion, memory
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Occipital Lobes
visual cortex
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Motor cortex
controls voluntary movements.
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Sensory Cortex
receives information from skin surface and sense organs.
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Visual Function
The functional MRI scan shows the visual cortex is active as the subject looks at faces.
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Language areas
Aphasia is an impairment of language, usually caused by left hemisphere damage either to Broca’s area (impaired speaking) or to Wernicke’s area (impaired understanding). understanding).
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Visual cortex
recieves written words as visual stimulation
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angular gyrus
transforms visual representation sinto an auditory code
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wernicke's area
interprets auditory code
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Broca's area
controls speech muscles via the motor cortex
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motor cortex
word is pronounced
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Association Areas
More intelligent animals have increased “uncommitted” or association areas of the cortex.
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hearing words
auditory cortez and Wernick's area
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seeing words
visual cortex and angular gyrus
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speaking words
broca's area and motor cortex
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The brains placidity
- The brain is sculpted by our genes but also by our experiences.
- Plasticity refers to the brain’s ability to modify itself after some types of injury or illness.
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Somatic nervous system
The division of the peripheral nervous system that controls the body’s skeletal muscles.
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Autonomic Nervous system
Part of the PNS that controls the glands and other muscles.
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(ANS) Sympathetic NS
arouses the body, mobilizing its energy in stressful situations (fight-or- flight)
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Parasympathetic NS (ANS)
calms the body, conserving its energy (rest and digest)
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