lecture 11.1 main points Flashcards
what systems share the responsibility for maintaining homeostasis? what is the objective?
nervous and endocrine systems share the responsibility
objective is to keep controlled conditions within limits that maintain life
how does the nervous system work to maintain homeostasis
rapid responses using AP
how does the endocrine system work to maintain homeostasis
slow response using hormones
main structures of nervous system and their function
brain - central control center ~ 100 billion neurons
spinal chord - connects brain to nerves of the body - about 100 million neurons
nerves - bundles of hundreds to thousands of axons ( each nerve follows a defined path and serves a specific region of the body)
neuron - basic functional unit of the neuron system
structures of the CNS, found in which body cavity
brain and spinal chord, found in the dorsal body cavity
integration and control center
structures of the peripheral nervous system
spinal nerves to and from spinal cord
cranial nerves, to and from brain
found outside the CNS
two major functional divisions of PNS
sensory - afferent
motor - efferent
from what do somatic sensory fibers convey information and where do they send it to
convey impulses from the skin, skeletal muscles, and joints sent to CNS
from what do visceral sensory fibers convey information and where do they send it to
convey impulses from the visceral organs to the CNS
three subdivisions of the PNS
somatic nervous system, autonomic nervous system, enteric nervous system
what is the job of somatic sensory neurons? list examples of areas they relay information from
convey information from somatic receptors in the head, body wall, and limbs to the CNS
includes receptors for senses such as hearing, vision, taste and smell
what is the job of the somatic motor neuron? is this response voluntary or involuntary?
conduct impulses from CNS to skeletal muscles only
this is voluntary
where are the sensory portions of autonomic sensory receptors and autonomic sensory neurons primarily found
primarily in the visceral organs
where do autonomic motor neurons conducts information from and to ? voluntary or involuntary
conducts impulses from the CNS to smooth muscle cardiac muscle, and glands
involuntary control
what are the two subdivisions of the autonomic motor neurons and what is the overall effect?
sympathetic - fight or flight
parasympathetic - rest and digest
what is the enteric nervous system also known as
the brain of the gut
what is the function of the enteric sensory neurons
monitor and communicate conditions of and in the GI tract to the interneurons (integration neurons) of the ENS and to the CNS
what is the function of enteric motor neurons
modify GI propulsion, acid, glandular, and hormonal secretions
what is the function of the enteric interneurons
may process enteric sensory information and decide to modify GI muscle contraction and secretion through enteric motor neurons if neededs
what division of the ANS was the ENS once considered part of? can ANS still affect ENS functioning
parasympathetic nervous system
some actions of ENS can be modified by ANS
describe the composition of nervous tissue
tightly packed, high cell density, little extracellular space
list the two principal cell types of the nervous system and their properties
neurons (nerve cells)- excitable cells that transmit electrical and chemical signals
neuroglia - small cells that support, surround, and wrap delicate cells
list common structures of most neurons
cell body, axon, dendrites, axon terminals
where do neurons gather or receive their information
at dendrites
receive neurotransmitters signals that conducts impulse changes toward the cell body
list other names for the cell body
perikaryon, or soma
what structures are found in the cell body of a neuron
lysosomes, mitochondria, golgi complexes, SER, rough ER (called nissl bodies)
what is the function of an axon
conduct impulses away from the cell body toward another neuron or effector cell
list the three structures found at the beginning of an axon
axon hillock - where axon joins the cell body
initial segment - beginning of axon
trigger zone - junction between axon hillock and initial segment
how do axons transmit signals ? in what form
nerve impulses (action potentials)
what is the name of the axon’s plasma membrane
axolemma
what is the name of the end of an axon
axon terminal - secretory region
what occurs at the axon terminal in response to an AP
neurotransmitters are released at the axon terminal in response to an AP
Do axons always only communicate with one cell? if not, how do they communicate with multiple cells at the same time?
can communicate with many different neurons at the same time through axonal branches
what structures are not present in the axon? how does this affect the healing of a damaged axon?
lacks rough ER and golgi apparatus
if axon is damaged they quickly decay
what are the many fine processes of an axon terminal called? what are the bulb shaped ended of these processes called?
axon terminals (telodendria)
synaptic end bulbs
what is the site of communication between neurons, or neurons and effector cells called?
synapse
what is the term for the gap between the pre and post synaptic cell called
synaptic cleft
what is stored in the end bulb of a presynaptic neuron? what structure are these stored in?
neurotransmitters are stored in the pre synpatic neuron and they are stored within synaptic vesicles
do pre-synaptic neurons contain only one neurotransmitter
no, contains many different neurotransmitters each with a different effect on the post synaptic cell
what cannot propagate across a synaptic cleft of neuronal synpases
electrical impulses (AP)
what is a chemical synapse, why is it necessary for communication if pre and post synaptic cells are not connected by gap junctions
use neurotransmitters to modify electrical activity in the post synaptic cell
neurotransmitters used to communicate at the synapse and re-establish or inhibit an AP in post synaptic cell
what is an electrical synapse?
allows an electrical impulse to directly modify electrical activity in the post synaptic cell
uses gap junctions to allow passage of ions between pre and post synaptic cell
what are the two types of transport systems used to move substances through the axon?
slow axonal transport and fast axonal transport
what is moved using slow axonal transport and in which direction
conveys axoplasm and in one direction only - from cell body toward axon terminals
what is moved using fast axonal transport and in which direction ? anterograde? retrograde?
moves materials in both direction
anterograde - uses motor proteins to move organelles and synaptic vesicles from the cell body toward the axon terminals
retrograde - uses motor proteins to move membrane vesicles and other cellular material from axon terminals to the cell body for degradation or recycling
how can substances taken into the neuron at the axon terminal travel to the cell body
by fast retrograde support
how can harmful agents take advantage of fast retrograde support
can travel back up the axon
does location of the wound matter in regards to fast retrograde support
yes, a short transit time for the harmful substance can be dangerous
list some basic features of how neurons can differ in size and shape
can be as long as a person is tall, pattern of dendritic branching is varied and distinctive for neurons in different parts of NS, can have short axons or no axon
how are neurons classified by structure
based on number of processes (axons on dendrites) extending from the cell body
multipolar neuron description
many processes extend from the cell body, all are dendrites except for a single axon
bipolar neuron descritption
two processes extend from the cell body, one is a fused dendrite and the other is in an axon
unipolar neuron description
one process extends from the cell body and forms central and peripheral processes which together comprise an axon
functional classification of neurons, where they send signals to, type of neuron, where typically found
sensory - send signals from sensory receptors to CNS, almost all unipolar, located in cell bodies in ganglia in PNS
motor - carries impulse from CNS to effectors, multipolar, most cell bodies in CNS
interneurons (association) neurons - typically found between sensory and motor neurons, shuttle signals through CNS pathways, mostly confined to CNS although ENS has some as well
what type of neurons are the neurons of the brain and spinal cord typically
interneurons
what are astrocytes and where are they found ? function?
most abundant and highly branched
star shaped
cling to neurons, synaptic endings, and capillaries
function - support and brace neurons, important role in exchanges between capillaries and neurons
guide migration of young neurons
control chemical enviro around neurons
response to nerve impulses and neurotransmitters
influence neuronal functioning - participate in information processing in the brain
what are microglial cells, where are they found, what is their function
small, ovoid cells with thorny processes that touch and monitor health of neurons
migrate toward injured neurons
can transform to phagocytize microorganisms and neuronal debris in CNS
what are ependymal cells, where are they found, what is their function
range in shape from squamous to columnar, may be ciliated (cilia beat to circulate CSF)
line the central cavities of the brain and spinal column
form permeable barrier between CSF in cavities and tissue fluid bathing CNS cells
what are oligodendrocytes, where are they found, what is their function
branched cells, processes wrap CNS nerve fibers forming insulating myelin sheaths of many neuronal axons
what are satellite cells, where are they found, what is their function
surround neuron cell bodies in PNS, similar to astrocytes in CNS
what are Schwann cells, where are they found, what is their function
surround all peripheral nerve fibers and form myelin sheath around axons of neurons
similar function as oligodendrocytes
vital to regeneration of damage peripheral nerve fibers
what is another name for Schwann cells
neurolemmocytes
what is myelin
a whitish, protein lipid substance
what is another term for a myelinated axon
myelinated fibers
what is the function of myelin
protects and electrically insulates (keep charge from escaping) axon
increases speed and distance of nerve impulse transmission
compare speed of myelinated axons vs un-myelinated
un-myelinated conduct more slowly and not as far
what cells from myelin in the PNS
Schwann cells
how do Schwann cells myelinate axons
wrap around axon in jelly roll fashion
myelin sheath - concentric layers of Schwann cell plasma membrane around axon
outer collar of perinuclear cytoplasm (formerly neurolemma)
-peripheral bulge of Schwann cell containing nucleus and most of cytoplasm
One Schwann cell forms one segment of myelin sheath in PNS
what substances are often missing, or in considerable less amount, on the plasma membrane of a myelin sheath? why is this important to the job of the myelin? what locks the layers together?
less protein, no ion channels or carries
good electrical insulators (keep charge in or out)
interlocking proteins bind myelin membrane layers together as they wrap around the axon
what are myelin sheath gaps, what is the old name?
gaps between adjacent Schwann cells
formerly called Nodes of Ranvier
what axon membrane proteins that are important for AP are found in myelin sheath gaps
high density of ion channels
where do axonal branches emerge from?
the gaps between myelin sheaths
describe non-myelinated fibers in the PNS
thin axons not wrapped in myelin
may be surrounded by Schwann cells but no coiling
describe non-myelinated fibers in the PNS
thin axons not wrapped in myelin
may be surrounded by Schwann cells but no coiling
what cells form myelin sheaths in the CNS
oligodendrocytes
list main anatomical differences in myelination in CNS and PNS
no outer collar of perinuclear cytoplasm since most organelles in the cell body that is not part of the myelin wrap
thinnest fibers in CNS typically unmyelinated - covered by long extensions of adjacent neuroglia
what is CNS white matter
regions of brain and spinal cord with dense collections of myelinated fibers, usually nerve fiber tracts (bundles of axons)
what is CNS grey matter
mostly neuron cell bodies and unmyelinated fibers
