Ch 11 Nervous System Flashcards
Information gathered by sensory receptors about internal and external changes
Sensory input
Processing and interpretation of sensory input
Integration
Activation of effector organs produces a response
Motor output
Muscles and glands
Effector organs
Divisions of the nervous system
Central and peripheral nervous systems
Brain and spinal cord of dorsal body cavity
Integration and control center(interprets sensory input and dictates motor output)
Central nervous system
Consists mainly of nerves that extend from brain and spinal cord
Spinal and cranial nerves
Peripheral nervous system
To and from spinal cord
Spinal nerves
To and from the brain
Cranial nerves
Two functional divisions of peripheral nervous system
Sensory and motor
Afferent
Sensory
Efferent
Motor
Somatic fibers and visceral fibers
Sensory
Conveys impulses from skin, skeletal muscles, and joints to CNS
Somatic sensory fibers
Convey impulses from visceral organs to CNS
Visceral sensory fibers
Transmits impulses from CNS to effector organs
Somatic and autonomic
Motor
Skeletal muscle(voluntary)
Somatic nervous system
Glands(involuntary)
Autonomic nervous system
Small cells that surround and wrap delicate neurons
Neurolgia
Excitable cells that transmit electrical signals
Neurons
Most abundant neuroglia, versatile, and highly branched
Cling to neurons and synaptic endings
Functions: support and brace neurons,guide migration of neurons, control chemical environment, respond to nerve impulses, influence neuronal functioning
Astrocytes
Small ovoid cells with thorny processes that touch and monitor neurons
Migrate toward injured neurons
Can transform to phagocytize microorganisms and neuronal debris
Microglial cells
Squamous or columnar
May be ciliated(produces and circulates spinal fluid)
Lines the central cavities of brain/spinal column
Ependymal cells
Branched with cells
Processes wrap CNS nerve fibers and form insulating myelin sheaths
Oligodendrocytes
Surround neuron cell bodies in PNS function similar to astrocytes of CNS
Satellite cells
Surround all peripheral nerve fibers and form myelin sheaths in thicker nerve fibers
Vital to regeneration of damaged peripheral nerve fibers
Schwann cells
Structural units of nervous system Large highly specialized cells that conduct impulses Extreme longevity Amitotic High metabolic rate All have cell body and process
Neurons
Lie along nerves in PNS
Ganglia
Clusters of neuron cell bodies in CNS
Nuclei
Biosynthesis center of neuron
Spherical nucleus with nucleolus
Some contain pigments
Plasma membrane is a part of receptive region
Neuron cell body
Bundles of neuron processes in CNS
Tracts
Bundles of neuron processes in PNS
Nerves
Two types of processes
Dendrites and axons
In motor neurons
Receptive region of neuron
Convey incoming messages toward cell body as graded potentials
Dendrites
Appendages with bulbous spiky ends
Dendritic spines
Come shaped area of cell body
Axon hillock
Long axons
Nerve fibers
Occasional branches
Axon collaterals
Distal endings
Axon terminals
Functions of axon:
Conduct region of neuron, generates nerve impulses, transmits them along axolemma to axon terminal, lacks rough ER
Released into extra cellular space
Neurotransmitters
Neuron cell membrane
Axolemma
Composed of myelin. Segmented sheath,
Myelin sheath
Myelination in PNS
Formed by Schwann cells
Myelin sheath gaps between adjacent Schwann cells
Sites where axon collaterals can emerge
Nodes of ranvier
Thin fibers not wrapped in myelin
Surrounded by schwann cells but no coiling
Nonmyelinated fibers
Regions of brain and spinal cord with dense collections of myelinated fibers
Usually fiber tracts
White matter
Mostly neuron cell bodies and nonmyelinated fibers
Gray matter
Toward CNS
Sensory
Away from CNS
Motor
Within CNS
Interneurons
Approx resting membrane potential
-70 mV
Short distance signal
Graded potential
Long distance signal
Action potential
Short lived localized changes in membrane potential
Depolarization or hyperpolarization
Triggered by stimulus that opens gates ion channels
Current flows but dissipates quickly and decays
Graded potentials
Principle way neurons send signals
Principle means of long distance neural communication
Brief reversal of membrane potential with a change in voltage of 100 mV
Do not decay over distance as graded potentials do
Action potential
All gated Na and K channels are closed
Only leakage channels for Na and K are open
Resting state
Depolarizing local currents open voltage gates Na channels
Na influx causes more depolarization which opens more Na channels
At threshold positive feedback causes opening of all Na channels
Depolarizing phase
Na channel slow inactivation gates close
Membrane permeability to Na declines to resting state
Slow voltage gates K channels open
Repolarizing phase
Some K channels remain open, allowing excessive K effkux
This causes a slight dip below resting voltage
Na channels begin to reset
Hyperpolarization
An AP either happens completely or it does not happen at all
The all or none phenomenon
Time from opening of Na channels until resetting of the channels
Ensures that each AP is an all or bone event
Enforces one way transmission of nerve impulses
Absolute refractory period