The Nervous system
The nerve cell is the basic unit of communication in the vertebrate nervous system
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Components of the Nervous System
Figure 11.1
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Three Classes of neurons
The Neural circuit consists of Sensory neurons
receptor for stimulus Interneuron (CNS)
integrate signals Motor neuron
transfer signal to effector (muscle)
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Types of Neurons in the Nervous System
Figure 11.2
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Anatomy of a Neuron
Cell body: functional portion
Dendrites: short extensions that receive signals
Axon: long extension that transmits impulses
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How does a neuron hold and move info?
A neuron at rest has a voltage difference across the plasma membrane called a resting voltage potential
An action potential (AP) is when this charge across the membrane is briefly switched
The action potential moves down the membrane at a rapid pace.
Ap can move faster over mylenated portions is called saltatory conduction
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Myelinated Neuron
Figure 11.7a
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Maintenance of the Resting Membrane Potential
Figure 11.3
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Resting Membrane Potential, Graded Potentials, and an Action Potential
Figure 11.4
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The Nerve Impulse Is a Bioelectrical Signal
The sodium-potassium pump uses ATP to transport sodium ions out and potassium ions in
The inside of a resting neuron has a negative charge relative to the outside
An action potential is a reversal and restoration of the charge difference across the membrane
The sodium-potassium pump restores the original distribution of ions Action potentials are all-or-none events A neuron cannot fire during the refractory period
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How does a signal move from one neuron to another?
A synaptic cleft divides 2 neurons The AP will not move across the synaptic cleft Neuro transmitters are released by the signal
cell to the receiver cell Move by diffusion
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Transfer of Information from Neuron to Target
Synaptic transmission: Release of neurotransmitter: graded potential achieved
Effects of neurotransmitter: Excitatory: depolarize postsynaptic cell Inhibitory: hyperpolarize postsynaptic cell
Role of postsynaptic neuron: integrate and process information
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Types of chemical synapse
Acetylcholine: neuromuscular junctions, glands, brain and spinal cord
Norepinepherine: affects brain regions concerned with emotions, dreaming
From table 11.1
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The nervous System
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Paths of information flow
Signals between the brain and spinal cord move to the body regions by nerves
Sensory nerves move a signal towards the brain and spinal cord
Motor neurons move a signal from the brain or spinal cord to the body
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Divisions of the nervous System
Central nervous system
CNS
Is the brain and spinal cord
Peripheral nervous system
PNS
all nerves that carry signals to and from the CNS
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Parts of the PNS
Sensory Division carries info to the brain and spinal cord.
Motor Division carries info from the brain to the bodies effectors (things that do the work)
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The Motor division of the PNS has 2 divisions
Somatic nerves relay commands to and from skeletal muscle
Voluntary control
Autonomic nerves send signals to and from smooth muscles
Involuntary control
Sympathetic Parasympathetic
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The autonomic divisions
Parasympathetic
slow down the body activity when the body is not under stress
Rest and digest
Sympathetic
increase overall body activity during times of stress, excitement or danger
fight or flight response
hormone epinephrine
Fig 11.12
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Sympathetic and Parasympathetic
Are Antagonistic Work towards the automatic, subconscious
maintenance of homeostasis.
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Parts of CNS
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Components of the CNS
Spinal cord 31 pair of spinal nerves Grey matter White matter Controls some reflex
actions like bladder emptying
Brain parts Hindbrain
medulla oblongata cerebellum pons
Midbrain Forebrain
cerebrum thalamus hypothalamus
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Ventricles of the Brain and Circulation of Cerebrospinal Fluid
Figure 11.13
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Brain: Major Divisions
Hindbrain: coordinates basic, automatic, vital functions
Medulla oblongata: controls automatic functions of internal organs
Cerebellum: coordinates basic movements Pons: aids flow of information Midbrain: coordinates muscles related to vision
and hearing
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Brain: Processes and Acts on Information
Forebrain: receives and integrates information concerning emotions and conscious thought
Hypothalamus: helps regulate homeostasis Thalamus: receiving, processing, and transfer center Limbic system: neuronal pathways involved in emotions
and memory Cerebrum/cerebral cortex: higher functions
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Sleep
Sleep center: reticular activating system (RAS)
Stages: based on electroencephalograms (EEGs): Stage 1: transitional, random small waves on
EEG Stage 2: skeletal muscles relax, little eye or body
movement, EEG shows sleep spindles
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Sleep (cont.)
Stage 3: heart and respiration slower, EEG shows slow wave sleep
Stage 4: difficult to awaken, heart and respiration slowest, body temperature decreased
REM (rapid eye movement) sleep: dreaming, EEG same as awake
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Limbic System: Emotions of Fear, Anger, Sorrow, Love
Figure 11.19
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Memory: Storing and Retrieving Information
Short term: working memory, information from previous few hours
Long term: information from previous days to years
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Other parts of the CNS
The two cerebral hemispheres communicate through the corpus collosum left verbal skills right nonverbal skills such as music math, abstract
Brain cavities and Canals cerebrospinal fluid surrounds and fills in cavities in the
brain Blood Brain barrier- controls what moves into the brain.
Will prevent infections.
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Our state of consciousness
The CNS governs sleeping, dozing, daydreaming and full alertness
neurons of the reticular activating system RAS control the changing levels of consciousness by releasing serotonin.
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Memory
Association is the linkage of information to structural and chemical changes
short term- few bits lasts a couple of hours
Long term- permanent and limitless
The most important info goes rapidly into long term storage
memory is stored in a form resistant to degradation
Possibly caused by changes in synapses.
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Tips on studying
Concentrate on what you study. Minimize interference. Study takes time. Break material into smaller portions. Rephrase materials in your own words. Test yourself to see what you know.
Primary somatosensory and motor areas of cerebral cortex
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Disorders of the nervous system
Trauma Infections Transmission and synaptic defects. Abnormal growth Headache Tumors Stroke
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Psychoactive Drugs
Action: affects higher brain functions Psychological dependence: user craves the
feeling associated with the drug Tolerance: takes more of the substance to
achieve the same affect Addiction: the need to continue obtaining and
using a substance; no free choice Withdrawal: physical symptoms that occur upon
stopping the drug
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Know what the parts of the brain do
Brain parts medulla oblongata cerebellum pons cerebrum thalamus hypothalamus
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seratonin
Just a reminder to talk about drugs that interact with brain.
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