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Sensory function
sense changes in internal and external environment thru SENSORY receptors
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Integrative function
Analyze SENSORY information, stores some aspects and makes decisions regarding behaviors
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Motor function
respond to stimuli by initiating action
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CNS
central nervous system: consists of brain and spinal cord.
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Ganglia
Mass of nervous tissue outside the brain and spinal cord
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Cranial nerves fxn
- control senses, expressions, movement
- considered PERIPHERAL (it is beneath brain stem)
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cerebrospinal fluid fxns
cushions CNS (runs through brain & spinal cord)
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Nervous System fxns
thoughts, feelings, senses, and movements
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spinal cord fxns
physical movement
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brain fxns
feelings, sexual excitement
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Enteric Nervous system
- involuntary
- controls GI tract
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PNS
- peripheral nervous system: consists of cranial & spinal nerves, contain sensory and motor fibers and receptors that fall off of the CNS.
- Fxn: to receive info and send TO the CNS, and to carry back processed into FROM the CNS
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Somatic Nervous System
- voluntary
- Involves:
- neurons from sensory receptors to the CNS
- Motor neurons to the skeletal muscle tissue
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Autonomic Nervous System
- involuntary
- Involves:
- neurons from visceral organs to the CNS
- motor neurons to the smooth & cardiac muscle
- -sympathetic division: fight or flight
- -parasympathetic division: rest & digest (essential for life)
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Resting Membrane Potential
- -70mV - cell is polarized (more positive extracellular)
- involves more Na outside of cell and more K inside cell
- NEGATIVE ions INSIDE cell membrane..and POSITIVE ions OUTSIDE cell membrane
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What happens during an action potential?
Voltage-gated Na and K channels open in sequence
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Depolarization
- results from a chemical or mechanical stimulus
- Voltage-gated Na channels open and Na rushes into the cell
- -55mV (cell is more positive due to influx of Na)
- Positive feedback process
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Repolarization
- K+ channels open
- -70mV (K releases from cell decreasing its positive charge)
- K channels opening is slower than Na influx
- Na flow influx starts once K channels finally open
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Hyperpolarization
- Too much K+ is released from cell
- -90mV (need to put more K into the cell to go back to -70mV resting potential)
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Refractory Period
involves when a neuron cannot operate another action potential
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Absolute Refractory Period
when even a strong stimulus cannot begin another action potential
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2 types of electric signals
- action potentials (travel long distances)
- graded potentials (localized in brain)
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chemical vs electrical synapses
- Electrical: tissue --> nerve, can also synchronize groups of neurons
- Chemical: nerve --> nerve. Info transfer from presynaptic neuron to a postsynaptic neuron
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Does strength of the stimulus relate to the speed of the nerve impulse?
No, the speed of the impulse is the SAME no matter what strength of stimulus
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Chemical Synapses characteristics
- One-way info transfer
- Action potential reaches end bulb and voltage-gated Ca+2 channels open
- Ca+2 flows inward triggering release of neurotransmitter
- Neurotransmitters cross synaptic cleft and bind to receptors (the more neurotransmitters released the greater change in potential of postsynaptic cleft)
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Result of Ca in BAD neurons
vasorestriction - LACK of blood supply to the area
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Effects of Neurotransmitters
- Excitatory
- Inhibitory
- Both effects present in PNS and CNS
- Same neurons can be both excitatory and inhibitory
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Excitatory effect on neurotransmitter
- occurs during depolarization, this postsynaptic potential is called EPSP
- results from opening of Na channels
- Postsynaptic cell MORE likely to reach threshold
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Inhibitory effect on neurotransmitter
- results from opening of Cl- or K+ channels
- Causes postsynaptic cell to become more Hyperpolarized
- postsynaptic cell LESS likely to reach threshold
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Summation
the release of neurotransmitters at the same time
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Agonist
enhances neurotransmitter effects
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Antagonist
blocks action of neurotransmitters, decreasing their effect
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3 responses
- 1. Small ESPS occurs: potential reaches -56mV ONLY
- 2. impulse is generated: threshold reaches, membrane potential is AT LEAST -56mV
- 3. ISPS occurs: membrane is HYPERPOLARIZED, potential drops BELOW -70mV
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Neural circuits
- network of neurons may contain thousands or millions of neurons
- These circuits are involved in many activities, including:
- breathing
- short-term memory
- waking up
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Regeneration and Repair of Neurons
- PNS can repair damaged dendrites or axons, BUT mostly scar tissue forms instead
- CNS has NO possible form of repair, due to: lack of neurolemma and growth stimulating factors
- due to rapid formation of scar tissue
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