purpose of nervous system maintaining homeostasis using rapid nerve impulses (action potentials)...
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Purpose of nervous system maintaining homeostasis using rapid nerve
impulses (action potentials) movement memories behavior
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functions: Sensory function: afferent (sensory) neurons
detect internal and external stimuli and carry message to brain
Integrative function: processes sensory information
Motor function: produces a motor response after processing sensory information. Efferent (motor) neurons carry information to effectors (muscles and glands)
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Organization of nervous system 2 main subdivisions: central (CNS) – brain
and spinal cord - and peripheral (PNS) – nervous tissue outside CNS.
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Further subdivisions PNS: somatic (voluntary) nervous system and
autonomic (involuntary) nervous system Somatic: sensory neurons (to the brain) and
motor neurons (from the brain – cranial and spinal nerves - to skeletal muscles)
Autonomic: sensory neurons (to brain from visceral organs) and motor neurons (from brain to smooth muscle, cardiac muscle, and glands)
Motor part of ANS: sympathetic (“fight or flight”) and parasympathetic (“rest and digest”)
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Peripheral Nervous System
A look at its two branches: somatic and autonomic
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Somatic nervous system Controls skeletal muscles
Cranial nerves Spinal nerves/plexuses
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Cranial nerves 12 pairs
Assigned roman numeral (indicate order from anterior to posterior) and a name (designate nerve’s distribution or function)
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Ex: Olfactory (I) nerve
and
Optic (II) nerve
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Spinal nerves/plexuses - 31 pairs form complex
network of nerves serving the limbs = plexus
Important plexuses: cervical, brachial, lumbar and sacral
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Cervical plexus
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Brachial plexus Important nerves:
Axillary Median Ulnar Radial
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Lumbar plexus Originates L1-L4
Important nerves: Femoral Obdurator
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Sacral plexus Originates L4-L5;S1-
S4
Important nerve: sciatic
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ASSIGNMENT CREATE A CHART (TREE) THAT
CLASSIFIES ALL THE DIVISIONS OF THE NERVOUS SYSTEM
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Neuron physiology
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Neuron physiology Background:
inactive neuron – polarized (more + in extracellular space).
Extracellular: mainly Na+
Intracellular: mainly K+
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Inactive until excited by stimulus (threshold = generator potentialgenerator potential) EX. 1: light, sound, touch EX. 2: neurotransmitters
stimulus causes: Open Na+ gates Diffusion of Na+ Charge (polarity) changes – depolarization. A
situation called a graded potential (inside more positive)
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Neuron transmits an action potential (nerve impulse) – a long distance signal.
Na+ gates close; K+ diffuses out: Returns cells to beginning electrical conditions (repolarization)
Activation of sodium-potassium pump (uses ATP)
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Propagation of action potential in neurons with myelin sheaths:
Impulses jump from node to node
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Myelin sheath: covering on some neurons that increases the speed of nerve impulse conductions
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Neuron speed related to its anatomy Myelin sheath: covering on some neurons
that increases the speed of nerve impulse conductions Amount increases from birth to maturity. (a baby
is not as coordinated as adult)
Nodes of Ranvier: gaps in myelin sheath
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How neurons transmit a message Neurotransmitters Extracellular space: Synaptic cleft
(synapse) Repeat in subsequent neurons
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Reflexes Rapid, predictable, and involuntary
responses Occur over neural pathways called reflex
arcs Types: somatic (stimulate sk. muscles) and
autonomic (smooth muscles, heart, glands) Indicate health of nervous system
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Parts: reflex arc1. Sensory receptor –
reacts to stimulus
2. Sensory neurons:
3. Integration center: synapse between sensory/motor neurons
4. Motor neurons:
5. Effector organ – muscle/gland that responds (the reflex)
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Neurotransmitters Acetylcholine: excitatory at NMJ Dopamine: active in emotional responses,
addictive behaviors, pleasurable experiences, contraction of some sk. muscle
Serotonin: control of mood, appetite, and the induction of sleep.
Nitric oxide: causes vasodilation. Lowers bp and causes erection in penis. (viagra enhances the effect of NO)
Endorphins: natural painkillers, feelings of euphoria
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Modifying the effects of neurotransmitters
Stimulated or inhibited by drugs. EX: Parkinson patients take a drug to boost
dopamine production in brain Botulinum toxin blocks release of acetylcholine
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Neurotransmitter receptors can be activated or blocked. EX: Isuprel- drug to treat asthma attack – it
binds to receptor and mimics/enhances natural neurotransmitter effect
Neurotransmitter removal can be stimulated or inhibited. EX: cocaine blocks dopamine reuptake
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Parkinson's disease: degeneration of neurons that release dopamine causing involuntary skeletal muscle contractions