Chapter 13 - Neural Tissue Flashcards
What are the two communication systems?
Nervous system and endocrine system.
What does the nervous system do?
Coordinate all body systems and electrochemical signaling.
What does the endocrine system use for signaling?
Hormones.
What is the general make-up of the nervous system?
CT, BVs, neurons, and neuroglia.
What are the 2 divisions of the nervous system?
Central nervous system (CNS) and peripheral nervous system (PNS).
What comprises the CNS?
Brain and spinal cord.
What comprises the PNS?
Cranial and spinal nerves.
CNS characteristics?
Brain and spinal cord, covered by meninges, starts as a hollow tube, bathed in cerebro spinal fluid, and integration center.
PNS charcteristics?
Consists of cranial and spinal nerves that contain both sensory and motor fibers, connects CNS to muscles, glands & all sensory receptors, and brings info to and from the CNS.
What are the two types of PNS?
Afferent division (sensory) and efferent division (motor).
What are the two divisions of the efferent division?
Somatic division (conscious) and autonomic division (unconscious).
General functions of nervous system?
Receptor: detect stimuli, sensory: afferent PNS, integrative: CNS, motor: efferent PNS, and effector: muscle/gland.
What are the types of nervous tissue?
Neurons and neuroglial cells.
Neuron characteristics?
Structural & functional units, excitable, and amitotic.
Neuroglial cell characteristics?
Accessory cells and act like connective tissue.
What are the three major structures of neurons?
Soma (cell body), dendrites, and axon.
Is the soma mononucleated or multinucleated?
Mononucleated.
What does the soma consist of?
Nissl bodies, axon hillock, perikaryon, and neurofibrils.
Nissl bodies characteristics?
Ribosome clusters; give gray color.
Axon hillock characteristics?
Connects soma to axon.
Perikaryon characteristics?
Region around the nucleus.
Neurofibrils characteristics?
Cytoskeleton that extend into dendrites/axons; gives shape.
Dendrite characteristics?
Respond to neurotransmitters, short, branched, unmyelinated, specialized for contact with other neurons, and conducts impulses toward the cell body.
Axon characteristics?
Only 1/cell, conducts nerve impulses away from soma, can give off collaterals, wrapped in myelin sheath, end in synaptic terminals, produce neurotransmitters.
The axon may contact what?
Another neuron, muscle fibers, and glands.
Another name for axonal transport?
Axoplasmic flow.
What does axonal transport do?
Move cellular materials (not signals) through the axon.
What are the 2 types of axonal transport?
Anterograde and retrograde.
What is anterograde axonal transport?
Away from soma; neurotransmitters, organelles, and nutrients.
What is retrograde axonal transport?
Toward soma; degraded materials to be recycled & extracellular substances
What is the axoplasma?
Cytoplasm of an axon.
What does the axoplasma consist of?
Few organelles and cytoskeletal proteins.
What do cytoskeletal proteins do?
Form cytoskeleton, maintain shape, and generate axonal transport.
What is axolemma?
Plasma membrane of an axon.
What does the axolemma consist of?
Collaterals, telodendria, and synaptic terminal.
What are collaterals?
Side branches.
What are telodendria?
Terminal extensions.
What are synaptic terminals?
Where the neuron contacts the postsynaptic cell.
How are neurons classified?
Based on the number and morphology of dendrites.
What are the types of neurons?
Anaxonic, bipolar, unipolar, and multipolar.
What are anaxonic neurons?
Small neurons and axons cannot be distinguished from dendrites (CNS, especially interneurons that coordinate special senses.)
What are bipolar neurons?
Several small dendrites converge onto one, dendrite and axon separated by soma, and unmyelinated (sensory neurons of special sensory organs).
What are unipolar neurons?
Several small dendrites converge onto one large one, dendrite and axon continuous, and usually myelinated (majority of sensory neurons in PNS).
What is another name for unipolar neurons
Pseudo-unipolar.
What are multipolar neurons?
Many dendrites extend from soma, long axon, myelinated (majority of motor neurons in PNS and spinal interneurons in CNS).
What are the functions of afferent neurons?
Sensory
Characteristics of afferent neurons?
Cell body usually are outside CNS, have receptor ends on dendrites or are associated with receptor cells in sense organs, and carry impulses from peripheral body parts to brain or spinal cord.
What are the receptors of afferent neurons?
Exteroceptors, proprioceptors, and interoceptors
What do exteroceptors do?
Sense touch, temperature, pressure, light, and chemicals.
What do proprioceptors do?
Monitor muscle and skeleton position.
What do interoceptors do?
Monitor internal systems (digestion, respiratory, urinary, etc.).
Where are interneurons found?
Only in CNS.
How are interneurons classified?
Based on effects.
What are the types of classification of interneurons?
Excitatory and inhibitory.
What is the function of efferent neurons?
Motor function.
Characteristics of efferent neurons?
Cell body usually inside CNS and carry impulses from the brain or spinal cord to peripheral body parts.
What are the types of efferetn neurons?
Somatic and autonomic/visceral.
What do somatic neurons do?
Control skeletal muscle.
What do autonomic/visceral neurons do?
Control smooth muscles/glands.
What are the neurgolial cells of the PNS.
Satellite and schwann cells
What are the neuroglial cells of the CNS.
Astrocytes, oligodendrocytes, ependymal cells, and microglia
Astrocytes characteristics?
Largest, most common, and star shaped.
Functions of astrocytes?
Structure and repair, metabolism, regulate ions and nutrition, guide neurons to target, and form blood-brain barrier.
Oligodendrocytes characteristics?
Like astrocytes but smaller.
Functions of oligodendrocytes?
Form myelin in CNS and sequester debris.
Microglia characteristics?
Smallest, least common, and derived from myeloid cells.
Functions of microglia?
Help support neurons, phagocytosis, and increase in number during injury or disease.
Ependymal cell characteristics?
Columnar/cuboidal, microvilli on luminal surface, and joined by gap junctions.
Functions of ependymal cells?
Help produce cerebrospinal fluid (CSF), form porous layer, and monitor CSF composition.
Satellite cell characteristics?
Associated with soma.
Functions of satellite cells?
Assist with exchange of nutrients and isolates neuron from extraneous stimuli.
Schwann cell characteristics?
Produce myelin in PNS and encloses axons of longer peripheral nerves.
Functions of schwann cells?
Support neurons, prevent contact, and myelinate large PNS axons.
Unmyelinated axon characteristics?
Appear gray, many axons associate with a single schwann cell, and CNS; no glial cells (rarely are PNS axons without ANY covering.).
Myelinated axon characteristics?
Appear white, CNS; oligodendrocytes myelinate part of several axons, and PNS; schwann cell meylinates part of one axon.
Myelin structure?
Myelin, neurilemma, and nodes of ranvier.
What is myelin?
Plasma membrane of schwann cell wrapped around axon.
What is neurilemma?
Part of schwann cell that contains cytoplasm.
What are nodes of ranvier?
Gaps in myelin sheath.
When does the myelination process start and end?
Starts at week 14 and completed by age 2-3 years.
What are the functions of myelin?
Isolate axons and increase rate of action potential.
Can PNS fibers regenerate?
Yes, but only a fraction of the axon.
What is regeneration of the PNS fibers called?
Wallerian degeneration.
What happens when the axon separates from the cell body?
Distal portion of axon will deteriorate along with myelin sheath, macrophages clean up, some schwann cells remain, get thin basement membrane and layer of CT around schwann cell, hollow tube forms, proximal end sprouts, remain schwann cells produce new myelin.
How much does an axon grow per day?
3-4 mm.
Repair in CNS?
Is more limited, degeneration occurs after injury, oligodendrocytes do not proliferate, proximal end sprouts but has no tube to folow, and astrocytes produce scar tissue an chemicals blocking regrowth.
Nerve impulse types?
Irritability, excitability, action potential, and nerve impulse.
What is irritability?
Abilitiy to respond to stimuli.
What is excitability?
Ability to transmit an impulse.
What is the action potential?
An electrical impulse changing the permeability of a membrane.
What is the nerve impulse?
AP moving down an axon.
When do impulses travel faster?
Axon is myelinated and has a larger diameter.
Synapse characteristics?
Functions as control/transmission point and site of communication.
What do synapse communicate with?
Sensory structure and neuron, neuron and effector, 2 neurons, and any two cells with gap junctions.
What are the types of synapses?
Electrical and chemical.
Electrical synapse characteristics and example?
Gap junctions cause the exchange of charged ions between two cells. Intercalated disk in cardiac muscle.
Chemical synapse characteristics and examples?
Chemicals are release by one cell and travel to another. Neuromuscular junction and neuron-neuron contact.
Chemical synapse characteristics?
Synaptic vesicles house neurtransmitter, only exist in the presynatpic cell, release neurotransmitter into the synaptic cleft, receptors on post synaptic membrane register neurotransmitter, proliferates AP from one cell to the next, and communication in one direction only.
What are the steps at chemical synapse?
AP reaches synaptic knob of presynaptic neuron, neurotransmitter released, neurotransmitter crosses cleft and binds to receptors in post synaptic membrane, get change in permeability, and neurotransmitter is then removed from synaptic cleft.
Neuronal pool characteristics?
Recieve impulses from afferent fibers (input), impulses carried away on efferent fibers (output), and afferent fibers can branch many times as they enter a pool.
What are the types of neuronal pools?
Convergence, divergence, serial processing, parallel processing, and reverberation.
What are serial processing neuronal pools?
One neuron to another in series.
What are divergence neuronal pools?
When impulses leaves a pool, it may spread into several output fibers and allows impulse to be amplified.
What are convergence neuronal pools?
Single nerve in pool may receive impulses from 2 or more incoming fibers, if lead to same nerve; they are said to converg, and allows summation of impulses from different sources.
What are parallel processing neuronal pools?
Processing information from several neurons at once.
What are reverberation neuronal pools?
Positive feedback continues activity of circuit.
What is facilitation?
One neuron may receive either excitatory and inhibitory stimuli from multiple neurons, the net effect of all this input results in a net charge, and if charge is positive enough it will result in an AP.
What is the AP produced called.
Threshold.
What happens in facilitation if neuron is below threshold?
No impulse, but nerve is more excitable to next impulse, nerve is said to be facilitated.
What does facilitation allow?
Multiple sources to manage the nervous system.
CNS structures?
Nuclei, center, and tracts
What is the nuclei?
Collection of neuron cell bodies.
What is the center?
Collection of neuron cell bodies working together.
What are the tracts?
Bundles of axons.
PNS structures?
Ganglia and nerves.
What are ganglia?
Collection of neuron cell bodies.
What are nerves.
Bundles of axons.
