Chapter 11 Flashcards
Nervous Tissue
Master in controlling and communicating system for the body
Cells will communicate via electrical and chemical signals (rapid and specific; immediate response)
Nervous system
- Sensory Input
- Integration
- Motor Output
3 Overlapping Functions of NS
Information gathered by sensory receptors about internal and external changes
Sensory input
Processing and interpretation of sensory input
Integration
Activation of effector organs (muscles and glands) –>
Produces response
Motor output
Brain and spinal cord of dorsal body cavity; Integration and control center
Interprets sensory input and dictates motor output
Central Nervous System (CNS)
Communication between CNS and rest of body
Consists of mainly spinal nerves (into and away from spinal cord) and cranial nerves (into and away from brain)
Peripheral Nervous System (PNS)
Conducts impulses from receptors to the CNS
Made of somatic and visceral sensory nerve fibers
Somatic - Convey impulses from skin, skeletal muscles, and joints to the CNS
Visceral - Convey impulses from visceral organs to CNS
Sensory afferent division
Conducts impulses from CNS to effectors (muscles and glands)
Made of motor nerve fibers
Motor efferent division
Subdivision of motor efferent division
Conducts impulses from CNS to skeletal muscle
Voluntary nervous system
Uses somatic motor nerve fibers
Somatic nervous system
Subdivision of motor efferent division
Conducts impulses from CNS to smooth muscle, cardiac muscle, and glands
Involuntary nervous system
Uses visceral motor nerve fibers
Autonomic nervous system
Subdivision of autonomic nervous system; mobilized body systems during activity
Sympathetic nervous system
Subdivision of autonomic nervous system; promotes housekeeping functions during rest, reserves energy
Parasympathetic nervous system
Excitable cells that transmit electrical signals
Nerve cells
Neurons
Cells that surround and protect delicate neurons
Glial cells
Neuroglia
Most abundant CNS glial cells; versatile and highly branched; Cling to neurons, synaptic endings, capillaries
Function: support and brace neurons, play role in exchanges between capillaries and neurons
Astrocytes
Small, ovoid cells with thorny processes that touch and monitor neurons
Migrate towards injured neurons in CNS
Phagocytize microorganisms and neuronal debris
Microglial cells
Line the central cavities of the brain and spinal column; May be ciliated
Involved information and circulation of cerebrospinal fluid (CSF)
Ependymal cells
Branched cells; Processes wrap around more than one CNS axon, forming myelin sheaths
Oligodendrocytes
PNS glial cell; surrounds neuron cell body
Function similar to astrocytes of CNS
Satellite cells
PNS glial cell; surrounds all peripheral nerve fibers and form myelin sheaths in thicker nerve fibers
Similar function to oligodendrocytes
Vital to regeneration of damaged peripheral nerve fibers
Schwann cells
Excitable cells that transmit electrical signals
Large, highly specialized to conduct impulses
Characteristics: extreme longevity, amitotic, high metabolic rate
Have a cell body with one or more processes
Neurons
A.k.a Perikaryon/soma
Biosynthetic center of neuron
Contains nucleus/nucleolus/rough ER
Plasma membrane is part of the receptive region which receives input info from other neurons
Cell body
Clusters of neuron cell bodies in CNS
Most are located in CNS
Nuclei
Clusters of neuron cell bodies in PNS
Ganglia
Short, tapering, diffusely branched processes
Receptive (input) region on neuron
Convey incoming messages toward cell body as short signals (graded potential)
Dendrites
Appendages with bulbous or spiky ends on dendrites
Dendritic spines
Conducting region of neuron
Axon
Cone shaped start of axon
Axon hillock
Long axon
Nerve fiber
Axons with occasional branches
Axon collaterals
Axons branch profusely at their end
Terminal branches
Axon endings; Secretes neurotransmitters which can excite or inhibit a neighbor neuron
Axon terminals/terminal buttons
Neuron cell membrane; Nerve impulses run down and are transmitted along
Axolemma
Two types: anterograde or retrograde
When molecules and organelles are moved along axons by motor proteins and cytoskeletal elements
Axonal transport
Axonal transport away from cell body
——->
Anterograde
Axonal transport toward cell body
<——-
Viruses, bacterial toxins, and prions damage neural tissue by this process
Retrograde
Bundles of axons in CNS
Tracts
Bundles axons in PNS
Nerves
Composed of myelin, a whiteish, protein-lipid substance covering nerve fiber
Myelin sheath
Protects and electrically insulates axon
Increase speed of nerve impulse transmission
Myelin
Segmented sheath surrounds most long or large diameter axons
Conduct nerve impulses rapidly
Myelinated fibers
NO sheath; Conduct impulses more slowly
Still surrounded by Schwann cells but not coiled multiple times
Nonmyelinated fibers
PNS myelin sheath; wraps around axon in jelly roll fashion
Plasma membrane has less proteins
Schwann cells
Gaps between adjacent Schwann cells
“Nodes of Ranvier”
Myelin sheath gaps
Myelin sheath gaps present
No outer collar of perinuclear cytoplasm
Thinnest fibers are usually unmyelinated
Myelination in CNS
Regions of brain and spinal cord with dense collections of myelinated fibers
White matter
Mostly neuron cell bodies and nonmyelinated fibers
Gray matter
Three or more processes on neuron; 1 axon with dendrites, most abundant type in CNS
Multipolar neuron
Two processes on neuron; 1 axon, 1 dendrite
Rare, found in special sense organs
Bipolar neuron
One process, T shaped; 1 axon with peripheral process and central process
A.k.a pseudounipolar
Mainly in PNS
Sensory neurons
Unipolar neuron
Transmit impulses from sensory receptors towards CNS
Most are unipolar; cell bodies are located in ganglia in PNS
Sensory neurons
Carry impulses from CNS to effectors
Multipolar
Motor neurons
Association neurons; Lie between motor and sensory neurons
Shuttle signals through CNS pathways
Most are multipolar
Interneurons
