Chapter 13: Neural Tissue Flashcards
what are the two communication systems in neural tissue?
nervous system and endocrine system
What does the nervous system do? How does it accomplish this?
coordinate all body systems
-accomplished by the transmission of signals
(body parts to the central nervous system)
(central nervous system to the body parts.)
what kind of signaling does the nervous system use?
electrochemical signaling
the endocrine system is a (slower/faster) scale than the nervous system. What chemicals in the bloodstream does it use?
slower; hormones
what is in the general make up of the nervous system?
Connective tissues
Blood vessels
Neurons
Neuroglia
what are the two divisions of the nervous system? What makes up each?
Central nervous system (CNS)
-brain and spinal cord
Peripheral nervous system (PNS)
-cranial and spinal nerves
describe the CNS (5 things)
- Brain and spinal cord
- Covered by meninges
- Starts as a hollow tube
- Bathed in cerebrospinal fluid
- Integration center
describe the PNS (3 things)
- consists of cranial and spinal nerves that contain both sensory and motor fibers
- connects CNS to muscles, glands & all sensory receptors
- Brings info to and from the CNS
What are the two divisions of the peripheral nervous system? what are they responsible for?
Afferent Division = sensory
Efferent Division = motor
the efferent division can be broken down into two divisions. What are they?
Somatic Division (conscious) Autonomic Division (unconscious)
What are 5 general functions of the nervous system?
Receptors-detect stimuli Sensory-afferent PNS Integrative-CNS Motor-efferent PNS Effector-muscle/gland
describe neurons
structural & functional units
Excitable
Amitotic
describe neuroglial
accessory cells
act like connective tissue
what are the three major structures of a neuron?
soma dendrite axon
what is the soma?
cell body (mononucelate)
what does the soma consist of? describe *4 things
Nissl Bodies: ribosomes clusters; give gray color
Axon Hillock: connects soma to axon
Perikaryon: region around the nucleus
Neurofibrils: cytoskeleton that extend into dentrites/axons; gives shape
what do dendrites do?
respond to neurotransmitters
are dendrites myelinated?
no
do dendrites conduct impulses away or towards the cell body?
towards
how many axons are there per cell?
1
do axons conduct impulses away or towards the cell body?
away
axons can give off what?
collaterals
many axons are wrapped in a what?
describe what this is
Myelin Sheath: glial cells wrapped around the axon
what is located at the end of an axon?
synaptic terminals
axons produce what?
neurotransmitters
slide 15
does the axon or neurotransmitter contact muscle fibers, glands, and/or other neurons?
what is another name for axonal transport?
what is this?
Axoplasmic flow
Movement of cellular materials (not signals) through the axon
What are the two types of axonal transport?
describe them
Anterograde
-away from soma; neurotransmitters, organelles, nutrients
Retrograde
-toward soma; degraded materials to be recycled & extracellular substances
What is the axoplasma?
cytoplasm of axon
what does the axoplasma consist of?
Few organelles Cytoskeletal proteins -Form cytoskeleton -Maintain shape -Generate axonal transport
what is the axolemma?
plasma membrane of an axon
what does the axolemma consist of?
describe them briefly
Collaterals: side branches
Telodendria: terminal extensions
Synaptic terminal: contains synaptic vesicles; where neuron contacts postsynaptic cell
The structural classification of neurons is based on the number and morphology of_________
dendrites
what are the four structural classifications of neurons?
Anaxonic
Bipolar
Unipolar
Multipolar
describe anaxonic structure
-Small neurons
-Axons can not be distinguished from dendrites
(CNS, especially interneurons that coordinate special senses)
describe bipolar structure
Several small dendrites converge onto one
Dendrite & axon separated by soma
Unmyelinated
(Sensory neurons of special sensory organs)
describe unipolar structure
Also know as pseudo-unipolar Several small dendrites converge onto one large one Dendrite & axon continuous Usually myelinated (Majority of sensory neurons in PNS)
describe multipolar structure
Many dendrites extend from soma Long axon Myelinated Majority of motor neurons in PNS Spinal interneurons in CNS
afferent neurons have ______ function
sensory
describe afferent neurons
cell body location, where impulses are carried to, etc
Cell body usually are outside CNS
Have receptor ends on dendrites or are associated with receptor cells in sense organs
Carry impulses from peripheral body parts to brain or spinal cord
afferent neurons have three receptors. What are they?
exteroceptor
Proprioceptors
Interoceptors:
What are Exteroceptors responsible for?
touch, light, temperature, pressure, chemicals
what do proprioceptors do?
monitor muscle and skeleton position
what do interoceptors do?
monitor internal systems (digestion, respiration, urinary, etc.)
describe interneurons
Only in CNS Classified based on effects -Excitatory -Inhibitory Most abundant -Link 2 or more neurons
efferent neurons have ____ function
motor
for efferent neurons where are the cell bodies normally located? where do they carry impulses?
Cell body usually are inside CNS
Carry impulses from the brain or spinal cord to peripheral body parts
what is the difference between somatic and autonomic efferent neurons?
somatic controls skeletal muscle and autonomic controls smooth muscles/glands
what are the 2 neuroglial cells in the PNS?
Satellite and Schwann
what are the 4 neuroglial cells in the CNS?
Astrocytes
Oligodendrocytes
Ependymal cells
Microglia
describe astrocytes
the largest and most common neuroglial cell it is star shaped
what are the functions of astrocytes ?
Structure and repair Metabolism Regulate ions and nutrition Guide neurons to targets Form blood-brain barrier
Oligodendrocytes are like ______ but smaller
What are there 2 functions?
Like astrocytes but smaller
Functions:
Form myelin in CNS
Sequester debris
describe microglia and their functions
Smallest & least common Derived from myeloid cells Functions: Help support neurons Phagocytosis Increase in number during injury or disease
describe ependymal and their functions
Columnar/cuboidal Microvilli on luminal surface Joined by gap junctions Functions: Help produce cerebrospinal fluid (CSF) Form porous layer Monitor CSF composition
describe satellite cells
Associated with soma
Assist with exchange of nutrients
Isolates neuron from extraneous stimuli
what do schwann cells do and what are their functions?
Produce myelin in PNS Encloses axons of longer peripheral nerves Functions: Support neurons Prevent contact Myelinate large PNS axons
compare and contrast myelinated and unmyelinated axons
Myelinated
-appear white
-CNS; Oligodendrocytes myelinate part of several axons
-PNS; Schwann cell myelinates part of one axon
Unmyelinated
-appear gray
-Many axons associate with a single Schwann cell
(Note: rarely are PNS axons without ANY covering)
CNS; no glial cells
what is the myelin?
plasma membrane of Schwann cell wrapped around axon
what is the Neurilemma?
part of Schwann cell that contains cytoplasm
gaps in the myelin sheath are called what?
nodes of Ranvier
the myelination process starts at week______ and ends at year ______-______
14; 2-3
what is the function of myelin?
increase rate of action potential and isolate axons
describe regeneration of nerve fibers
:)
slides 40-44
how is the repair in the CNS different than the repair in the PNS?
More limited
Degeneration occurs after injury
Oligodendrocytes do not proliferate
Proximal end sprouts but has no tube to follow
Astrocytes produce scar tissue and chemicals blocking regrowth
what is irritability?
ability to respond to stimuli
what is excitability ?
ability to transmit an impulse
what is an action potential?
an electrical impulse changing the permeability of a membrane
what is a nerve impulse?
action potential moving down an axon
impulses travel faster when….
axon is myelinated
larger diameter
Synapses are a site of communication between …
Sensory structure and neuron
Neuron & effector
2 neurons
Any two cells with gap junctions
what are the two types of synapses?
electrical and chemical
describe an electrical synapse and give an example
Gap junctions cause the exchange of charged ions between two cells
Ex. Intercalated disks in cardiac muscle
describe a chemical synapse and give an example
Chemicals are release by one cell and travel to another
Ex. Neuro-muscular junction
Ex. Neuron-neuron contact
______ house neurotransmitter
Synaptic vesicles
chemical synapses only exist in the ________
presynaptic cell
chemical synapses release neurotransmitter into the….
synaptic cleft
Receptors on ____________ register the neurotransmitter
post-synaptic membrane
true or false: chemical synapses communicate in only 1 direction
true
only axons have synaptic vesicles
what are the steps that occur at a chemical synapse?
slides 51-52
neuronal pools receive impulses from ________. These impulses are carried away on______
afferent fibers (input) efferent fibers (output)
what are the five types of neuronal pools?
Convergence Divergence Serial processing Parallel processing Reverberation
serial processing is….
one neuron to another in series
describe Divergence
- When impulse leaves a pool, it may spread into several output fibers
- Allows impulse to be amplified
describe Convergence
- Single nerve in pool may receive impulses from 2 or more incoming fibers
- If lead to same nerve; they are said to converge
- Allows summation of impulses from different sources
parallel processing….
processes information from several neurons at once
In Reverberation…
positive feedback continues activity of circuit
One neuron may receive either ________ & _______ stimuli from multiple neurons. The net effect of all this input results in a _________. If this charge is positive enough it will result in an _______.
excitatory, inhibitory, net charge, action potential
The point where an action potential can be produced is known as the what?
threshold
If a neuron is excited, but still below threshold…….
no impulse, but nerve is more excitable to next impulse. The nerve is said to be facilitated
this whole system of facilitation allows for the (multiple/singular) source/s to manage the nervous system
multiple (slide 60)
What three structures are found in the CNS? briefly describe what they are
Nuclei: collection of neuron cell bodies
Center: collection of neuron cell bodies working together
Tracts: bundles of axons
What two structures are found in the PNS? briefly describe what they are
Ganglia: collection of neuron cell bodies
Nerves: bundles of axons
