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Intro to Nervous System
n/a
44
Anatomy
Undergraduate 3
10/01/2012

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Term
Functions of NS:
Definition
Master control of Communication system
-3 overlapping functions
Term
What are the 3 overlapping functions of NS?
Definition
1. sensory receptors monitor changes inside and outside body
2. Processes and interprets sensory input
3. Dictates a response by activating effector organs
Term
1. sensory receptors monitor changes inside and outside body
-What are the changes/gathered info?
Definition
Change= stimulus
Gathered info= sensory input
Term
2. Processes and interprets sensory input
-What makes decisions?
Definition
integration
Term
3. Dictates a response by activating effector organs
-What is a response?
Definition
motor output
Term
What are the basic divisions of the NS?
Definition
Central NS
and
Peripheral NS
Term
What does the CNS include? and functions?
Definition
Brain and spinal cord, integrating and command center
Term
What does the PNS include? and functions?
Definition
Outside the CNS, nerves extending from brain and spinal cord (cranial and spinal nerves)
-peripheral nerves link all regions of the body to the CNS
Term
Classify neurons:
Definition
1. Afferent
2. Efferent
3. Interneurons
Term
What are afferent neurons?
Definition
info toward CNS
-sensory neurons
-cell bodies outside of CNS in sensory ganglia
-central processes enter dorsal aspect of spinal cord
Term
What are efferent neurons?
Definition
infor away from CNS
-motor neurons
-axons exit the ventral aspect of spinal cord
Term
What are interneurons?
Definition
located totally within CNS
-synapse with sensory neurons
Term
How are sensory signals picked up?
Definition
by sensory receptors
-carried by afferent nerve fibers of PNS to CNS
Term
What do motor/efferent signals do when carried away from CNS?
Definition
-innervate muscles and glands.
Term
How are sensory input and motor output divided?
Definition
according to region they serve
-somatic body region= outside ventral body cavity
-visceral body region= inside ventral body cavity
Term
What does the divisions of the sensory input and motor output result in?
Definition
4 main subdivisions:
1. somatic sensory
2. visceral sesnory
3. somatic motor
4. visceral motor
Term
Functions of Somatic sensory:
Definition
Modality- something sensed
1. general somatic senses- receptors are widely spread (touch, pain, vibration, pressure, temperature)
2. Special somatic senses- receptors are restricted to head (hearing, balance, vision, smell)
3. Proprioceptive senses- detect stretch in tendons and muscle (body sense- position and movement of body in space)
Term
Functions of Visceral sensory:
Definition
1. General visceral senses- stretch pain, temperature, nausea, hunger (widely felt in digestive and urinary tracts/reproductive organs)
2. Special visceral senses- taste
Term
Functions of somatic motor:
Definition
General somatic motor- signals contraction of skeletal muscles
-voluntary control
-aka "voluntary nervous system"
Term
Functions of visceral motor:
Definition
Regulates contraction of smooth and cardiac muscle, secretion of glands
Makes up the autonomic nervous system
Controls functions of visceral organs
Often called involuntrary nervous system
Term
How many neurons in human body?
Definition
millions
Term
What is a neuron?
Definition
a specialized cell that conducts electrical impulses along the plasma membrane- action potentials
Term
What is the longevity of a neuron?
Definition
can live and function for a lifetime
Term
When do neurons divide?
Definition
they do not divide- fetal neurons lose their ability to undergo mitosis; neural stem cells are an exception
Term
What do neurons require?
Definition
An abundant oxygen and glucose supply- they have a high metabolic rate
Term
What do neurons form?
Definition
synapses- sites of communication between cells.
Term
What are synapses?
Definition
elaborate cell junctions
signals pass across synapse in one direction
Term
Neurotransmitteres are:
Definition
chemical messengers
Term
Presynaptic neuron:
Definition
conducts signal toward a synapse
Term
Postsynaptic neuron:
Definition
transmits electrical activity away from synapse
membranes have receptors for NT
Term
What are the types of Synapses?
Definition
Axodendritic
Axosomatic
Axoaxonic
Term
What is an axodendritic synapse?
Definition
Between axon terminals of one neuron and dendrites of another
-most common type
Term
What is an axosomatic synapse?
Definition
between axons and neuronal cell bodies
Term
What is an axoaxonic synapse?
Definition
uncommon types
Term
What and where are synaptic vesicles?
Definition
On presynaptic side:
-membrane bound sacs containing NT
-Mitochondira abundant in axon terminals
Term
What is the synaptic cleft?
Definition
seperates the plasma membrane of the two neurons
Term
How do synapses work?
Definition
NT released into synaptic cleft; diffuses to second neurons; binds to receptors on membrane of second neuron
Term
How are signals carried by neurons?
Definition
plasma membranes of neurons conduct electrical signals
Resting neuron membrane is polarized
Inner, cytoplasmic side is negatively charged
Stimulation of the neuron= depolarization
Impulse travels the length of axon
Electical signals= Action Potentials
Term
What is the basic function of NS?
Definition
Reflexes
Term
What is a reflex arc?
Definition
rapid, automatic response
-can be viseceral or somatic
-visceral include smooth muscle, cardiac muscle, and glands
-somatic include skeletal muscle
Term
5 components of Reflex arc:
Definition
1. receptor (site where stimulus acts)
2. sensory neuron (transmits afferent impulses to CNS
3. Integration center (one or more synapses in CNS)
4. Motor Neuron (conducts efferent impulses from integration center to an effector)
5. Effector- muscle or gland cell (Contracting or secreting)
Term
Types of reflexes:
Definition
Monosynaptic reflex
Polysynaptic reflex
Term
What is a monosynaptic reflex?
Definition
simplest of all reflexes
-just one synapse
-fastest
-ex: knee-jerk
Term
What is a polysnaptic reflex?
Definition
More common type
-most have single interneuron between the sensory and motor neuron
-ex: withdrawl reflexes
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