What are functions of the nervous system?
Sense and respond to environmental changes; communicate/coordinate organ systems; establish homeostasis in the body; work closely with the endocrine system to achieve and maintain homeostasis
Central Nervous System
Division of the nervous system that consists of the brain and spinal cord (aka CNS)
Peripheral Nervous System
Division that connects the central nervous system to the rest of the body; includes all sensory and motor neurons; divided into somatic nervous system and autonomic nervous system (aka PNS)
Neural "cables" containing many axons. These bundled axons, which are part of the peripheral nervous system, connect the central nervous system with muscles, glands, and sense organs
Groups of nerve cell bodies that coordinate incoming and outgoing nerve signals; swelling in nerve
Where does the CNS receive stimuli from?
How does the CNS work?
Brain and spinal cord receive stimuli from receptors; they then process and relate to past experience; this initiates impulses to muscles to contract and for glands to secrete
The nerves that sense organs that bring information to the CNS; part of the peripheral nervous system
Somatic (Afferent System)
Signals from skeletal muscles, skin, bones and joints
Visceral (Afferent System)
Signals from organs of thoracic and abdominal cavities
The nerves that dispatch information out from the CNS; part of the PNS
Signals to skeletal muscles; voluntary control
Signals to glands, cardiac muscles and smooth muscles; involuntary control
Visceral/Autonomic NS is further divided into what?
Sympathetic and parasympathetic nervous systems
Sympathetic Nervous System
Arouse body for action
Parasympathetic Nervous System
Calming effect on body
What is another name for a nerve cell?
Fundamental properties of Neurons include what?
Excitability, conductivity and secretion
Irritability; respond to an environmental change called a stimulus
Stimulus to electrical signal to cells
Electrical signal to release of neurotransmitters
What are the three functional classes of neurons?
Sensory (afferent), interneurons (association), and motor neurons (efferent)
Respond to pressure changes in the walls of blood vessels and digestive, reproductive, and urinary tracts
Respond to water-soluble and lipid-soluble substances that are dissolved in the surrounding fluid. They monitor the chemical composition of body fluids
Respond to osmotic pressure
Neurons that carry incoming information from the sense receptors to the central nervous system
Central nervous system neurons that internally communicate and intervene between the sensory inputs and motor outputs; make decision to determine body's response
Neurons that carry outgoing information from the central nervous system to regulate muscle contraction and glandular secretion
Describe the maintenance of homeostasis as it pertains to the nervous system
Quick to respond; effect - short duration
Describe the maintenance of homeostasis as is pertains to the endocrine system
Slow to respond; effect - long duration
Cell that carries messages throughout the nervous system
How many neurons are in the body?
Around 10 trilion
Known as glial cells: connective tissue that supports,nourishes, protects, insulates and organizes neurons; outnumber neurons 50:1; mitotically active; type determines function
Most abundant; support framework for nerve tissue; protection - blood/brain barrier; communication; promotes neuron growth
Produce myelin sheath in CNS; do not produce neurolemma therefore no regeneration in CNS
A fatty substance that helps insulate neurons and speeds the transmission of nerve impulses
Also neurilemma; the sheath encasing the axon of a nerve fiber
Act as phagocytes, eating damaged cells and bacteria, act as the brains immune system; clusters in areas of infection, trauma, and stroke
Forms myelin sheath in PNS; assists in regeneration of damaged nerve fibers; produces neurolemma -> regeneration
Brain tumor arising from glial cells (glial cells are mitotically active throughout life)
Mass of rapidly dividing cells
Grow rapidly, highly malignant; poor treatment due to blood/brain barrier
The cell body and control center of a neuron; it contains the nucleus and much of the chemical machinery common to most cells
The bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body
The extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands; neuron has only on axon
Swelling of the soma, the point where the axon begins
An axon that has divided into several branches allowing a single nerve cell to influence a wide array of other cells
An extensive complex of fine branches- each branch ends in a synaptic knob and contains synaptic vesicles full of neurotransmitters
Where neurotransmitters are, location of synaptic vessicles (membranous sacs with biochemicals), end of axons; distal tips of axon, info passes over to next neuron
A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next
Nodes of Ranvier
Gaps in the myelin sheath of the axons of peripheral neruons. Action potentials can 'hump' from node to node, thus increasing the speed of conduction (saltatory conduction)
Myelin [oligodendrocyte/schwann cell] covered segment from one node to the next
Can nerve fibers in CNS regenerate?
Can nerve fibers in PNS regenerate?
Yes; IF soma is intact and some of the neurolemma remains
What are the steps of nerve regeneration?
1. Once nerve is cut -> fibers distal to trauma cannot survive; degenerates
2. Soma swells; axon stump sprouts growth processes; distal end continues to regenerate, muscle fibers atrophy
3. Near injury, Schwann cells and neurilemma form regeneration tube
4. One growth process finds way into tube, others retract
5. Regeneration tube guides growing sprout back to original target cell -> reestablishes synaptic contact
6. Soma shrinks, reinnervated muscle fiber begins to regrow