Chapter 12- Fundamentals of the Nervous System Flashcards
Functions of the Nervous System
Sensory Reception
Integration
Elicit Response
Divisions of the Nervous System
Central (CNS)- Brain and Spinal Cord
Peripheral (PNS)- Everything else
Divisions of the Peripheral Nervous System
Somatic- Body as a whole
Visceral- Internal organs
Sensory (Afferent)- Toward CNS
Motor (Efferent) Away from CNS
Somatic Sensory Functions
Most sensory experiences
Touch, pain, pressure, vibration, temperature, proprioception
Hearing, equilibrium, vision
Visceral Sensory Functions
State of internal environment
Stretch, pain, temperature, chemical changes, visceral irritation, nausea, hunger
Taste and smell
Somatic Motor Function
Control of skeletal muscles
Visceral Motor Functions
Control smooth and cardiac muscles
Control glands
Autonomic Nervous System
Neurons
Basic communication cell
Dendrites- Receive information
Cell body (Soma)- Control center
Axon- Generate and conduct impulse
Characteristics of Neurons
Conductive
Longevity- Live for a long time
Do not divide
High metabolism
Structural Classifications of Neurons
Multipolar
Bipolar
Unipolar
Multipolar Neurons
Many dendrites with one axon
Motor and interneurons
Bipolar neurons
1 dendrite and 1 axon
Found only in special senses
Unipolar (Pseudounipolar) neurons
One short, singular process
Cell body is on the side of the central process
Sensory Neurons
Functional Classification of Neurons
Sensory (afferent)
Motor (efferent)
Interneurons (Association)
Sensory Neurons
Transmit impulses toward the CNS
Mostly unipolar
Cell bodies found in the PNS in ganglia
Motor Neurons
Transmit impulses away from the CNS; Junction with effector cells
Mostly multipolar
Cell bodies in the CNS in nuclei; Anterior gray matter
Interneurons
Transmit impulses within the CNS
Mostly multipolar
Cell bodies in the CNS in nuclei; posterior gray matter
Action potential
Electrical impulse that forms the basis of neuron communication
Depolarization of the cell
Synapses
Junction between neurons
Types:
Axodendritic- Axon & Dendrite
Axosomatic- Axon & Cell body
Synaptic potentials
Excitatory Synapses- Promotes depolarization and impulse generation
Inhibitory Synapses- Promotes hyperpolarization and restricts impulse generation
Neuroglial cells
Support cells
Non-excitable, maintenance, and insulator cells
Outnumber neurons 10:1
Neuroglia in the CNS
Astrocytes
Microglia
Ependymal cells- Line cavities and circulate cerebrospinal fluid
Oligodendrocytes- Insulatory cell that surrounds many axons
Neuroglia in the PNS
Satellite cells- Surround neuron cell bodies in ganglia
Schwann Cells (neurolemmocytes)- Insulatory cells
Myelin Sheaths
Surround axon to insulate and prevent current leakage
Increases impulse velocity
Multiple Sclerosis
Autoimmune disease that targets oligodendrocytes and myelin in the CNS
Nerves
Cordlike organ in the PNS made of many axons wrapped in connective tissue containing blood supply
Tracts
Nerve equivalents in the CNS
Many axons travelling in a similar direction
Reflex Arcs
Allow for rapid automatic responses
Components:
Receptor, sensory neuron, (interneuron), motor neuron, effector
Monosynaptic- No interneuron
Polysynaptic- With interneuron
Neuronal Circuits
Diverging- One neuron impacts many (Ex- Fight or flight)
Converging- Many neurons act on one (most neurons)
Reverberating- Self-stimulating feedback loop (ex- breathing)
Gray matter
No myelination; Location of cell bodies
Spinal gray matter- Internal
Brain gray matter- External
White matter
Myelinated axons
Spinal white matter- External
Brain white matter- Internal
Neuron regeneration
Only possible in the PNS if the cell body remains intact
Steps:
1) Macrophages invade and destroy axon distal to injury
2) Axon filaments grow into tube formed by Schwann cells
3) Axon regenerates and myelin sheath surrounds axon
