Nervous Physiology Flashcards
major controlling, regulatory, and communicating system in the body
nervous system
Center of all mental activity including thought, learning, and memory
nervous system
Together with the endocrine system, this system is responsible for regulating and maintaining homeostasis
nervous system
aspect of nervous system that keeps us in touch with our environment, both external and internal
receptors
Composed of brain, spinal cord, nerves, and ganglia
nervous system
Various activities of the nervous system can be grouped together as three general overlapping functions:
sensory
integrative
motor
changes which occur inside and outside the body
stimuli
monitor such things as temperature, light, and sound from the external environment
sensory receptors
Inside the body, the internal environment, receptors detect variations in:
pressure
pH
CO2 concentration
level of various electrolytes
gathered information from receptors, converted into electrical signals
sensory input
electrical signals that are transmitted to the brain
nerve impulses
decisions that are made each moment based on sensory input
integration
muscles and glands, cause an effect in response to directions from the nervous system
effectors
Two main types of cells in nerve tissue:
neuron
neuroglia
actual nerve cell, conducting cell that transmits impulses and the structural unit of the nervous system
neurons
“glial” cell which means nerve glue, nonconductive and provide a support system for the neurons
neuroglia
Special type of connective tissue for the nervous system
neuroglia
carry out the functions of the nervous system by conducting nerve impulses
neurons
Highly specialized and amitotic (cannot be replaced through mitosis
neurons
Each neuron has three basic parts
cell body (soma)
one or more dendrites
axon
similar to other type of cells, it has a nucleus with at least one nucleolus and contains many of the typical cytoplasmic organelles
cell body
Lacks centrioles since it functions in cell division
neuron cell body
cytoplasmic extensions or processes that project from the cell body
dendrites/axon
Sometimes referred to as fibers
dendrites/axon
usually, but not always, short and branching which increases their surface area to receive signals from other neurons
dendrites
▪Number varies
▪Called afferent processes because they transmit impulses to the neuron cell body
dendrites
have only one that projects from each cell body, usually elongated because it
carries impulses away from
the cell body
▪Called an efferent process
axon
infrequent branches of axon
axon collaterals
short branches where axon and axon collaterals terminate
telodendria
end of telodendria that are slightly enlarged to form synaptic bulbs
distal end
surrounds axons, segmented white, fatty substance
myelin
myelinated fibers make up what matter in the CNS
white matter
cell bodies and unmyelinated fibers make up what matter in the CNS
gray matter
unmyelinated regions between the myelin segments
nodes of ranvier
produce the myelin in the peripheral nervous system
schwann cells
Its cytoplasm, nucleus, and outer cell membrane form a tight covering around the myelin and around the axon itself at the nodes of Ranvier (neurilemma)
schwann cells
plays an important role in the regeneration of nerve fibers
neurilemma
produce myelin in the CNS, but there is no neurilemma, which is why fibers within the CNS do not regenerat
oligodendrocytes
Types of neurons according to the direction in which they transmit impulses relative to the CNS
afferent
efferent
carry impulses from peripheral sense receptors to the CNS
afferent
transmit impulses from the CNS to effector organs such as muscles and glands
efferent
Usually have short dendrites and long axons
efferent
located entirely within the CNS in which they form the connecting link between the afferent and efferent neurons
interneurons
Short dendrites and may have either a short or long axon
interneurons
do not conduct nerve impulses, but instead support, nourish, and protect the neurons
neuroglia
Far more numerous than neurons and unlike neurons, are capable of mitosis
neuroglia
benign tumors of the peripheral nervous system which commonly occur in their
sporadic, solitary form in otherwise
normal individuals
schwannomas
Rarely, individuals develop numerous tumors arising from one or many elements of the peripheral nervous system
schwannomas
this problem is a fairly common benign nerve growth and begins when the outer coating of a nerve in your foot thickens
Morton’s Neuroma
Caused by irritation of branches of the medial and lateral plantar nerves that results when two bones repeatedly rub together
Morton’s neuroma
Two subdivisions of the nervous system
CNS
PNS
brain and spinal cord are the organs of this subdivision of the nervous system
central nervous system
located in the dorsal body cavity and are encased in bone for protection
brain and spinal cord
brain is located in this
cranial vault
spinal cord is located in this canal of the vertebral column
vertebral canal
location where the brain and spinal cord
are continuous
foramen magnum
organs include nerves and ganglia
peripheral nervous system
bundle of nerve fibers, much like muscles are bundles of muscle fibers
nerves
extend from the CNS to peripheral organs such as muscle and glands
cranial nerves
spinal nerves
collections, or small knots, of nerve bodies outside the CNS
Ganglia
further divided into an afferent (sensory) division and efferent (motor) division
Peripheral Nervous System
transmits impulses from peripheral organs to the CNS
Afferent or sensory divison
transmit impulses from the CNS out to the peripheral organs to cause an effect or action
efferent or motor division
also called the somatomotor or somatic efferent nervous system, supplies motor impulses to the skeletal muscles
somatic nervous system
Sometimes called the voluntary nervous system
somatic nervous system
also called the visceral efferent nervous system, supplies motor impulses to cardiac muscle to smooth muscle, and to glandular epithelium
autonomic nervous system
Further divided into sympathetic and parasympathetic divisions
Regulates involuntary or automatic functions, called the involuntary nervous system
autonomic nervous system
consist of the brain and spinal cord, which are localed at the dorsal body cavity
central nervous system
surrounds the brain
cranium
protects the spinal cord
vertebrae
the brain and spinal cord is continuous with each other in this
foramen magnum
in addition to bone, the CNS is surrounded by this connective tissue membranes
meninges
Three layers of meninges around the brain and spinal cord
dura mater
arachnoid
pia mater
outer layer of the meninges, tough white fibrous connective tissue
dura mater
middle layer of meninges which resembles a cobweb in appearance, thin layer with numerous threadlike strands that attach it to the innermost layer
arachnoid
space under the arachnoid, filled with cerebrospinal fluid and contains blood vessels
subarachnoid space
innermost layer of the meninges, thin delicate membrane tightly bound to the surface of then brain and spinal cord and cannot be dissected away without damaging the surface
pia mater
tumors of the nerve tissue covering the brain and spinal cord
meningiomas
Not likely to spread, but physicians treat them as
though they are malignant to
treat symptoms that may develop when a tumor applies pressure to the brain
meningiomas
divided into the cerebrum, diencephalon, brain stem, and cerebellum
brain
largest and most obvious portion of the brain
cerebrum
Divided by a deep longitudinal fissure into two cerebral hemispheres
cerebrum
arching band of white fibers that connects the two hemispheres
corpus callosum
Provides a communication pathway between the two halves of the cerebral hemispheres
corpus callosum
Each cerebral hemisphere is divided into five lobes, four of which have the same name as the bone over them (5)
frontal lobe
parietal lobe
occipital lobe
temporal lobe
insula
lobe of cerebral hemisphere that lies deep within the lateral sulcus
Insula (Island of Reil)
centrally located and is nearly surrounded by the cerebral hemispheres
diencephalon
Includes the thalamus, hypothalamus, and epithalamus
diencephalon
about 80 percent of the diancephalons, consist of two oval masses of gray matter that serve as relay station for sensory impulses EXCEPT for the sense of smell going to the cerebral cortex
thalamus
small region below the thalamus, which plays a key role in maintaining homeostasis because it regulates many visceral activities
hypothalamus
most dorsal portion of the diencephalons, small gland involved in the onset of puberty and the rhythmic cycles in the body (like a biological clock)
epithalamus
region between the diancephalons and spinal cord
brain stem
Consist of three parts: midbrain, pons, and medulla oblongata
brain stem
superior portion of the brain stem
midbrain
bulging middle ;portion of the brain stem, region that primarily consist of nerve fibers that form conduction tracts between
the higher brain centers and
spinal cord
pons
extends inferiorly from the pons, continuous with the spina cord at the foramen magnum
▪Also called medulla
▪All ascending (sensory) and descending (motor) nerve fibers connecting the brain and spinal cord passes through this
medulla oblongata
second largest portion of the brain, located below the occipital lobes of the cerebrum
cerebellum
three paired bundles of myelinated nerve fibers form communication pathways between the cerebellum and other parts of the CNS
cerebral peduncles
series of interconnected, fluid-filled cavities found within the brain
ventricles
fluid found in the cavities of the ventricles of the brain
cerebrospinal fluid
extends from the foramen magnum at the base of the skull to the level of the first lumbar vertebra
spinal cord
Continuous with the medulla oblongata at the foramen magnum
spinal cord
Like the brain, surrounded by bone, meninges, and cerebrospinal fluid
spinal cord
Appears oval in shape (x-section)
spinal cord
Divided into 31 segments with each segment giving rise to a pair of spinal nerves
spinal cord
which end of the cord that have many spinal nerves extending beyond the conus medullaris to form a collection that resembles a horse’s tail (cauda equina)
distal end
the roots of the lumbar and sacral spinal nerves, which form a bundle within the lowest part of the spinal column
cauda equina
Two main functions of the spinal cord:
➢Serving as conduction pathway for impulses going to and from the brain (sensory impulses travel to the brain on ascending tracts on the cord, motor impulses travel on descending tract)
➢Serving as reflex center
functional unit of the nervous system
reflex arc
responses to stimuli that do not require conscious thought and consequently occur more quickly than reactions that require thought processes
reflexes
reflex action withdrawing the affected part before you are aware of the pain
withdrawal reflex
refers to tumors that arise from the support cells of the brain
glioma
cells that support the brain
glial cells
include astrocytoma, ependymomas, and oligodendrogliomas which are the most common primary tumors
brain tumor
consist of the nerves that branch out from the brain and spinal cor
peripheral nervous system
Form communication between the CNS and the body parts
PNS
Further divided into somatic nervous system and autonomic nervous system
PNS
consist of nerves that go to the skin and muscles and is involved in conscious activities
Somatic Nervous System
consist of nerves that connect the CNS to the visceral organs such as the heart, stomach, and intestines, mediates unconscious activities
autonomic nervous system
contains bundles of nerve fibers, either axons or dendrites, surrounded by connective tissue
nerve
contain only afferent fibers, long dendrites of sensory neurons
sensory nerves
have only efferent fibers, long axons of motor neurons
motor nerves
contain both types of fibers
mixed nerves
connective tissue sheath surrounding each nerve
epineurium
each bundle of nerve fibers and is surrounded by a layer of connective tissue
fasciculus
surrounds the fasciculus
perineurium
surrounds each individual nerve fiber with its myelin and neurilemma
endoneurium
May also have blood vessels enclosed in its connective tissue wrappings
endoneurium
twelve pair of these emerge from the inferior surface of the brain
cranial nerves
– all of cranial nerves except this pass through the foramina of the skull to innervate structures in the head, neck, and facial region
vagus nerve
Designated both by name and Roman numerals, according to the order in which they appear on the inferior surface of the brain
cranial nerves
how many cranial nerves are associated with the special senses of smell, vision, hearing, and equilibrium and have only
sensory fiers
three
how many cranial nerves are primarily motor in function but do have some sensory fibers for proprioception
five
is your body’s ability to sense movement, action, and location.
proprioception
remaining nerves consist of significant amounts of both sensory and motor fibers
four
benign fibrous growths that arise from the balance nerve, also called the XIII cranial nerve or vestibulocochlear nerve
acoustic neurons
Non-malignant tumors, location of these is deep inside the skull adjacent to the vital centers in the brain stem
acoustic neurons
As the tumors enlarge, they involve surrounding structures which have to do with vital functions
acoustic neurons
31 pairs of these emerge laterally from the spinal cord
spinal nerves
Each pair of nerves corresponds to a segment of the cord and they are named accordingly
spinal nerves
how many cervical nerves?
8
how many thoracic nerves
12
how many lumbar nerves
5
how many sacral nerves
5
how many coccygeal nervess
1
cell bodies of sensory neurons are located here
dorsal root
cell bodies of motor neurons are located here
gray matter
visceral efferent system which means it sends motor impulses to the visceral organs
autonomic nervous system
functions automatically and continuously without conscious effort to innervate smooth muscle, cardiac muscle, and glands
ANS
concerned with heart rate, breathing rate, blood pressure, body temperature, and other visceral activities that work together to maintain homeostasis
ANS
has two parts: sympathetic division and parasympathetic division
ANS
in this, neurons are enclosed within the skull
brain
connects to brain and enclosed within spinal cavity
spinal cord
bundles of many axons and neurons, can be sensory, motor, or both
nerves
have 12 pairs, emerge from the brain in pairs due to the bilateral division of the body
cranial nerves
31 pairs emerge from the spinal cord
spinal nerves
groups of neuron cell bodies located outside of the brain and spinal cord
ganglia
➢sensory in nature
➢encapsulated neurons for protection
ganglia
networks of neurons in digestive tract, motor in nature
enteric plexuses
monitor changes in internal or external environment
sensory receptors
scattered throughout the body (internal and external), give the ability of proprioception
sensory receptors
described as hypermotility, food passes through the GI tract quicker than normal
diarrhea
equivalent of a cell (muscle cell = muscle fiber)
muscle fiber
not a cell but an extension of the cytoplasm of a neuron
nerve fiber
extension of the cytoplasm of the neuron
axon and dendrites
– group of nerve fascicles
nerve bundle
covers the nerve fiber
endoneurium
rank from smallest to bigest
nerve bundle
nerve trunk
nerve fiber
nerve fiber > nerve bundle > nerve trunk
covers the nerve fascicle
perineurium
covers the nerve trunk
epineurium
carry information into brain and spinal cord
sensory receptors and sensory nerves
information processing (consolidation of information from sensory receptors; further processing)
integration
awareness of sensory input
perception
signal to muscles and glands (effectors)
efferent nerves
response can either be motor or secretory
efferent nerves
principal cells, epitomizes what nervous system is about, considered as terminal cells, cannot be replenished
neurons
can respond to stimuli and convert stimuli to electrical signals (nerve impulses) that travel along neurons
➢fewer than neuroglia
neurons
support, nourish, and protect neurons
neuroglia
means nerve
neuro
means glue in Latin
glia
are mitotic (can multiply and increase their number, can replenish)
neuroglia
critical for homeostasis of interstitial fluid around neurons
neuroglia
existence is crucial for the survival of neurons, monitor the level of CSF in the body
neuroglia cells
transplanting neurons from one patient to another without neuroglia lead to a lower change of survival while transplanting neuroglia with neurons increase its chance
neuroglia
interstitial fluid of the brain and spine
cerebrospinal fluid
amount of CSF that lead to high intercranial pressure
high CSF
intracranial pressure drops (brain can settle down)
low CSF
highly branched structures that carry impulses to the cell body
dendrites
Exclusive, can only be intended to receive a specific stimulus, thus needing it to be multiple
dendrites
conducts away from cell body toward another neuron, muscle, or gland
axon
Only one because the neuron can only generate one response
axon
Emerges at a cone-shaped axon hillock
axon
contain synaptic vesicles that can release neurotransmitters
axon terminals
made up of Lipids, hasten the speed of impulse conduction, insulate axons to prevent touching other actions
myelin
stellate shape
dendrites
discrete clumps of rough endoplasmic reticulum and free ribosomes in nerve cells
nissil’s bodies
each myelin covered axon
internode
– allows ions from outside to enter, pushes impulse faster (has sodium potassium pumps)
node of ranvier
sodium and potassium is involve, describes the way an electrical impulse skips from node to node down the full length of an axon,
saltatory conduction
collective unit of motor neurons and multiple muscles, consist of neuron, axon, and muscle fiber it innervates
motor unit
have several or many dendrites and one axon, most common type in brain and spinal cord
multipolar neuron
have one dendrite and one axon, found in the retina of the eye and inner ear
bipolar neuron
have fused dendrite and axon, sensory neurons of spinal nerves
unipolar neuron
Can differ with the shape with the bipolar neuron
unipolar neuron
Are not present in the human body, only present in primitive organisms
unipolar neuron
Basic neuron types
unipolar
bipolar
multipolar
pyrimidial cell
should be describe as pseudounipolar neuron, presumed to be one polarity due to convergence of the attachment to the cell body
unipolar
neurons that convey impulses to CAN (brain or spinal cord)
sensory
convey impulses from brain or spinal cord out through the PNS to effectors (muscles or glands)
motor
most are within the CNS but they transmit impulses between neurons such as between sensory and motor neurons
interneurons
cells smaller but much more numerous than neurons
neuroglia
Can multiply an divide and fill in brain areas
neuroglia
brain tumors derived from neuroglia
gliomas
Do not conduct nerve impulses but support, nourish, protect neurons
neuroglia
Different types of Neuroglia: (6)
astrocytes
oligodendrocytes
microglia
ependymal cells
schwann cells
satellite cells
help form blood brain barrier
astrocytes
make the blood vessel restrictive, another wall around the blood vessel
blood brain barrier
drugs that can cross blood brain barrier should be made out of this
lipid soluble
produces myelin in CNS
oligodendrocytes
Can myelinate multiple nerve fibers as long as it is in the immediate vicinity
oligodendrocytes
protect CNS cells from disease
microglia
▪Pierces the parasite like a spear hence its shape and appearance
microglia
form CSF in ventricles
ependymal cells
Cuboidal, epithelial cells
ependymal cells
produce myelin around PNS neurons; help regenerate PNS axons
Schwann cells
support neurons in PNS ganglia
Satellite cells
are covered with a myelin sheath
axons
many layers of lipid and protein; insulates neurons and increase speed of nerve conduction
myelin sheath
Appears white (in white matter
myelin sheath
gaps in the myelin sheath, which are important for rapid signal conduction
nodes of ranvier
is a condition that happens when the immune system attacks the brain and spinal cord.
can destroy myelin
multiple sclerosis
rare genetic disorder passed from parents to child. It’s caused by the absence of an enzyme that helps break down fatty substances. These fatty substances, called gangliosides, build up to toxic levels in the brain and spinal
cord and affect the function of
the nerve cells.
can destroy myelin
Tay-Sachs
Clusters of neuron cell bodies:
Ganglion
Nucleus
cluster of cell bodies in PNS
Ganglion
cluster of cell bodies in CN
Nucleus
bundle of axons in PNS
Nerve
bundle of axons in CNS
Tract
primarily myelinated axons
white matter
cell bodies, dendrites, unmyelinated axons, axon terminals, neuroglia
gray matter
Location of gray and white matter
spinal cord
brain
white matter (tracts) surround centrally located gray matter “H” of “butterfly”
what location of white metter
spinal cord
spinal cord part that is – sensory in nature
dorsal root
spinal cor dpart that is motor in nature
dorsal root
represent the color of myelin, can also have a lot of axons
white matter
gray matter in thin cortex surrounds the white matter (tracts)
what location of CNS
brain
neurons are housed in this in the voluntary and autonomic branches of the PNS
ganglion
Usually damaged first (because they do not have the protection of the bone) leading to sensory paralysis
ganglion
axons and dendrite in the PNS can be repaired if cell body is intact and Schwann cells are functional
regeneration of PNS neurons
form a regeneration tube and grow axons or dendrites if scar tissue does not fill the tube
Schwann cells
Central Nervous System (CNS) structures
brain
spinal cord
Peripheral nervous system structures
cranial nerves and branches
spinal nerves and branches
ganglia
sensory receptors
Peripheral Nervous System (PNS) divisions include
somatic
autonomic
sensory neurons from head, body wall, limbs, special sense organs while motor neurons to skeletal muscle; voluntary
somatic
sensory neurons are from viscera, motor neurons to viscera (cardiac muscle, smooth muscle, glands): involuntary
autonomic
“fight or flight”
sympathetic
“rest-and-digest”
parasympathetic
“brain of the gut” – sensory neurons monitor chemical changes and stretching of GI wall, motor neurons regulate contractions, secretions, and endocrine secretions (involuntary)
enteric nervous system
occurs when the membrane potential of a specific cell rapidly rises and falls
action potentials
Require a membrane potential (charge difference across cell membrane = polarization)
action potentials
Ion channels that allow to move by diffusion from ____ to ____ concentration
high
low
– allow ions to leak through membrane; there are more for K+ than Na+
leakage channels
channels that open and close on command, respond to changes in membrane so can generate and conduct action potentials
gated channels
typical resting membrane potential
-70mV
side of resting membrane potential that is more negative than its counterpart
inside
negativity of the inside of the membrane potential is due to the presence of this
ions
inside membrane is more negative due to this having many negative ions (too large to leak out), amino acids (in cellular proteins), and phosphates (as in ATP
cytosol
more positive due to few negative ions, Na+ does not leak out of cell: few Na+ channels and membrane pumps that quickly pump out that does leak (diffuse) into the cell
interstitial fluid
series of events that activate cell membrane in neuron or muscle fiber
action potential
An initial event (stimulus) is required which triggers resting membrane to become more permeable to Na+, causing enough Na+ to enter cell so that cell membrane reaches threshold of (~-55mV)
action potential
will spread along neuron or muscle fiber when the membrane reaches threshold
action potential
phase wherein Na+ channels open -> more Na+ enters cell and membrane potential rises becoming positive (-70>0>+30mV)
depolarizing phase
phase wherein K+ channels open, more K+ leave cell, membrane potential is returned to resting value (+30 > 0 > -70 mV)
depolarizing phase
overshooting of polarizing phase
hyperpolarizing phase
typical depolarization and repolarization take place in what time
1 millisecond
– levels of ions back to normal by action of Na+/K+ pump
recovery
brief period even with adequate stimulus, cell cannot be activated
refractory period
if a stimulus is strong enough to cause depolarization to threshold level
, the impulse will travel the entire length of the neuron at a constant and maximum strength
what principle
all or none
each section triggers the next locally as even more Na+ channels are opened (like row of dominoes)
nerve impulse conduction
Types of conduction
continuous conduction
saltatory conduction
in unmyelinated fibers, there is slower form of conduction
continuous conduction
– in myelinated fibers; faster as impulses leap between nodes of Ranvier
saltatory conduction
Factors that increase rate of conduction
myelin
large diamter
warm nerve fibers
Similar sequence of events occurs at (3)
synapse
neuromuscular junction
neuroglandular junction
neuron to neuron
synapse
(neuron-muscle fiber junction)
neuromuscular junction
(neuron-gland junction)
neuroglandular junction
triggered by action potential (nerve impulse) which includes sending neuron, space between neurons, and receiving neuron
synaptic transition
neuron that releases neurotransmitter
presynaptic neuron
space between neurons
synaptic cleft
receiving neuron
postsynaptic neuron
Synaptic transmission includes the following
Action potential arriving at presynaptic neuron’s end bulb
➢Opens voltage gated Ca2+ channels > Ca2+ flows into presynaptic cytosol
➢Increased Ca2+ concentration > exocytosis of synaptic vesicles
➢Neurotransmitter (NT) released into the cleft, serve as the trigger of ion channels
➢NT diffuses across cleft and binds to receptors in the postsynaptic membrane
➢Postsynaptic cell membrane may be depolarized or
hyperpolarized depending on
the type of NT and type of postsynaptic cell
➢1000+ neurons converge on synapse so the sum of all their NTs determine the effect
➢If threshold reached, then postsynaptic cell action potential results
transmission is only in this method because only presynaptic cell release NT and postsynaptic cell have receptors for NT binding
one way
Three possible mechanisms to remove NT from the cleft
➢Diffusion out of cleft
➢Destruction of enzymes such as acetylcholinesterase in cleft
➢Transport back (recycling) intro presynaptic cell
common in PNS which have stimulatory capabilities on skeletal muscles while inhibitory capabilities on cardiac muscle
acetylcholine
include glutamate, aspartate, gamma amino butyric acid (GABA), glycine
amino aicds
include norepinephrine (NE), dopamine (DA), and serotonin
modified amino acids
include endorphin
neuropeptides
