Nervous Tissue Flashcards
What is the general function of nervous tissue
It provides generation of nerve impulses that communicate w/ an regulate most body tissues.
What are the components of the CNS
Brain and spinal cord
What are afferent neurons
neurons that send a signal to the CNS
What are efferent neurons
neurons that send a signal away from the CNS
What are the 3 general organizations of the nervous system and what do they control.
- Somatic=> sensation from the body, motor control of the skeletal muscle, special senses
- Autonomic=>sensation from internal organs excluding the GI tract
- Enteric=> sensation of the GI tract
What are the 2 parts of autonomic nervous system.
Sympathetic and Parasympathetic divisions
What is an association (bundle) of neuronal axons
In CNS=> tract
In PNS=> nerve
What is a bundle or neuronal cell bodies
In CNS=> nucleus
In PNS=> ganglion
Define Plexus
an extensive network of nerves (axons and cell bodies) found in the PNS
What are the 2 general types of cells in the nervous system.
- Neurons=> produce and transmit impulses (action potentials)
- Neuroglia=> support cells of the neuron, more of these than neurons
What are the 3 basic parts of a neuron
- Dendrites=> (little trees) receiving portion of a neuron
- Cell body=>
- Axon=> propagates impulses,
What is the axoplasm
the cytoplasm of the axon
What is the axolemma
the plasmalemma of the axon
What are Nissl bodies
prominent clusters of rough ER in a neuron
Where do axons arise from in the cell body
Axon hillock
Where do action potentials arise from in the cell body
In the trigger zone which is the junction between the axon hillock and the initial segment of the axon. It integrates excitatory and or inhibitory postsynaptic potentials and if they sum to depolarize and action potential is sent.
What organelles do axons contain
Mitochondria, microtubules, neurofibrils
-thus protein synthesis does not occur
Define telodendria
Divisions at the terminal end of an axon
Define varicosities
small bead like swellings at the terminal end of an axon that transmit impulses to neighboring neurons
Name the 2 types of axonal transports and describe them.
- Slow axonal transports=> 1 way from cell body to axon terminal
- Fast axonal transports=> 2 way transport toward and away from cell body
How are neurons classified
based on the number processes (axons/dendrites) extending from the cell body
What are the 3 neuron types and their general characteristics.
- Multipolar =several dendrites, one axon. (Majority of neurons)
- Bipolar = 1 dendrite, 1 axon, used in special senses (hearing, taste, sight, smell, balance)
- Pseudounipolar= one process that extends from the body and splits into a branch that acts as a dendrite and axon (touch and stretch)
Where is the trigger zone a pseudounipolar neuron
close to the dendrite portion of the central branch
What are the Neuroglia of the CNS and there functions
- Astrocytes=takes up excessive neurotransmitters, regulate composition of CNS fluid and helps form blood brain barrier
- Ependymal cells= line the ventricles, produces CNS fluid, helps w/ blood brain barrier
- Oligiodendrocytes= myelinate CNS axons
- Microglia=Phagocytes of CNS
What are the Neuroglia of the PNS and there functions
- Schwann cells= myelinate PNS axons
2. Satellite cells= provide structural support and regulate exchange of materials between cell bodies and ISF
What cells do Gliomas arise from
Neuroglial cells
What is the role of myelin in the nervous system
insulate axons to speed up nerve impulse conduction
What is a Schwann cell called once it myelinates an axon
neurolemmocyte
What are nodes of Ranvier
gaps between myelin, occurs in PNS and CNS
What does the endoneurium surround
A nerve fiber which consist of the axon plus the myelin sheath
How does the myelination of an axon in the CNS differ from the PNS
CNS it is done by oligodendrocyte, which can myelinate multiples times same or different neurons. There is not a neurolemma
PNS = neurolemma, 1 schwann cell, i myelination
What is white matter primarily composed of
myelinated tract fibers
What is gray matter primarily composed of
Cell bodies, gets its color from Nissl bodies
What are the 2 types of electrical signals used by neurons to communicate
- Action potentials=all or nothing, used for long and short distances
- Graded potentials= used for short distances, are used to affect or effect APs, change in membrane potential is potential to strength of stimuli.
What two features must a nerve cell have to generate AP’s or graded potentials
- resting membrane potential
2. voltage gated ion channels
What is the rest membrane potential of neurons
-70 mV
What are the 4 types of ion channels and how do they function.
- Leakage channels=randomly open and close, slow leaky ions across membrane
- Ligand-gated channels= open or close in reponse to a certain compound
- Mechanically gated channel= open in response to a mechanical stimuli ie tension on plasma membrane
- Voltage gated channels= open and close in response to membrane potential
What accounts for the greatest negative charge intercellularly
organic phosphates, AA, and proteins,
Define hyperpolarization
membrane becomes more negative
Define depolarization
membrane becomes less negative
Describe the action potential phases in regards to ions and gated channels being opened
- Resting state= both Na and K voltage channels closed
- Depolarization threshold of -55mV is meet causing Na channels to open and Na to flood into cell
- Repolarization= Na channels close or start to close, K voltage gated channels open causing K to fluid out of the cell
4 Rest state restore, Na pumped out and K pumped back in
In the relative refractory period what voltage gated channels are open
K voltage gated channels open, Na in resting state
In the absolute refractory period what are Na and K voltage gated channels doing
K voltage channels open
Na voltage channels open and in the process of closing
How do Ca ions affect Na voltage channels
They bind to exterior of Na channel protein and cause the need for higher voltage levels to open the gated channel
What is the movement of a nerve impulse the axon terminals called
Propagation or conduction
What is positive feed back of propagation
part of cell membrane depolarizes d/t Na flowing into that segment of membrane, this in turn allows Na to influx into an adjacent portion of the cell membrane causing it depolarize
What is continuous conduction
the step by step depolarization and repolarization of adjacent membrane segments
What is saltatory conduction
Special mode of conduction only in myelinated neurons, were current is carried by intracellular and extracellular ions from one node of ranvier to the next
-Voltage gated channels concentrated at nodes of Ranvier
What form of conduction is faster and more energy efficient
Saltatory conduction
How do neurons produce the majority of their ATP and what does that mean for the vascularization of the nervous system
Aerobic respiration, so lots of O2 needed, so nervous tissue is highly vascularized
How does the diameter of the axon affect conduction
Larger diameter, faster conduction
What are the 3 sizes of axon diameters
A fibers= largest
B fibers= medium
C fiber= smallest
What 2 mechanisms enable stimuli of differing intensities to be registered differently given nerve impulses are the same size.
Frequency and number of sensory neurons activated
What does an influx of Ca at the varicosities causes
The release of neurotransmitter synaptic vesicles
