Nervous System lecture pt 1 Flashcards
What are the major functions of the nervous system?
- Receiving sensory input- monitoring internal and external environments
- Integrating information- brain and spinal cord
- Controlling muscles and glands- coordination of involuntary and voluntary responses, skeletal muscles interact when stimulated by nervous system
- Maintaining homeostasis
- Establishing and maintaining mental activity
We can consider the nervous system as a __________ system, receiving ______ form sending commands to different areas of the body.
communication, signals
central nervous system (CNS)
brain, spinal cord
sensory processing, motor transmission
higher functions - intelligence, memory, emotion
peripheral nervous system (PNS)
everything coming out of the spinal cord, everything outside of the CNS
- cranial nerves
- spinal nerves
enteric plexuses in small intestine
-sensory receptors in skin
PNS divisions
somatic- skin and cells
automatic- involuntary, move things thru digestive system
enteric- digestive systems
Somatic Nervous system
Transmits action potentials from the CNS to skeletal muscles
Autonomic Nervous System
transmits action potentials from the CNS to cardiac muscle, smooth muscle, and glands
AUTOMATIC
two subdivisions: Sympathetic and parasympathetic
Sensory Division
action potations thru sensory receptors into CNS
Motor Division
Conducts action potentials to effector organs, such as muscles and glands
two function divisions of nervous system
sensory, motor
Enteric Nervous system
Nervous system found only in digestive tract
Neural Tissue- tow different types of cells
neurons and glial cells
Neurons
receive stimuli, conduits action potentials, transmits signals to other neurons or effector organs
Glial cells
no action potentials, supportive and HELPER cells of the CNS and PNS, enhances and supposes neuron function, maintain normal condition within nervous tissues
Action Potential
is a brief electrical impulse that travels along the membrane of a neuron or muscle cell.
Neurons
specialized for nerve impulse conduct can communicate with one another and other cells
Basic structure of neurons
cell body- one nucleus
dendrites- extensions off of cell body, tree branches, gathers incoming info into cell body, receives signals from the other neurons and transmits info into the cell body
Axon- carries signals to the CNS or next cell, muscle fiver, or glands
Myelin sheath, speeds transfer of nerve impulses
Axon terminal- where we find our synapse , bulb-shaped endings
Nissl bodies
formed by Free ribosome’s and RER and gives the tissue a gray color (gray matter)
Axon hillock
area where electrical signals begins
nucleolus
creates ribosome components
CNS Repair- Neuron Regeneration
typical CNS neurons cannot divide, but some neural stem cells are retained in the brain and can divide. Neural stem cells are typically inactive
Most neurons lack
centrioles
a 2016 study showed damaged PNS axons can be repaired by
Schwann cells, triggering formant genes in the nerve (peripheral nervous system)
Multipolar neuron
most common in the CNS and motor neurons, have many dendrites and a single axon
Pseudo-Unipolar neurons
have the cell body off to one side, most abundant in the afferent division, connecting PNS to CNN
Bipolar neurons
have one dendrite and one axon with the cell body in the middle, and are found in sense organ
Afferent neurons aka
sensory neurons
sensory neurons
carry info to the CNS, 10 million plus in average body, receives info from two types of sensory receptors
two types of sensory receptors
somatic sensory receptors and visceral (internal) receptors
two types of somatic sensory receptors
external receptors and proprioceptors
external receptors
monitors external environment
proprioceptors
monitor position and movement of skeletal muscles and joints
visceral(internal ) receptors
monitor the internal organs, provided sensations of distention, deep pressure, and pain
Interneurons aka
association neurons
association neurons
most numerous type in the average body- 20 million
-located in the CNS
-function as links between sensory and motor processes
-have higher function like memory, planning, and learning
Efferent neurons aka
motor neurons
4 types of Glial cells in the CNS
astrocytes
oligodendrocytes
microglia
Ependymal cells
two types of Glial cells in the PNS
satellite cells and Schwann cells
astrocytes
found in blood vessels of the brain, help open and close blood vessel, maintaining blood brain barrier, available around synapses
oligodendrocytes
produce myelin sheaths for CNS
microglia
phagocytic cells, active immune response to bacteria/cell debris
ependymal cells
only found in brain, secrete cerebrospinal fluid
Astrocytes
large, numerous neuralgia in the CNS
- maintains blood-brain barrier by expanding and contracting blood vessels, which regulates blood flow.
- control synapse function
- communicates with many neurons
- sends signal waves (calcium spikes) to other parts of the brain
sheaths are formed by _____ _____ in the PNS
Schwann cells
Myelin Sheath
insulating membranous wrappings around the axons of some neurons
myelinated
neurons wrapped with this myelin sheath
sheaths are formed by ___ in the CNS
oligodendrocytes
nodes of Ranvier
gaps in the myelin sheath
ion movement
can only occur at the nodes of Raniver directs the action potential to move along the axon at specific intervals
multiple sclerosis
a disease of the myelin sheath that causes loss of muscle function, oligodendrocytes in the CNS disappear
ALS
oligondendrocytes in the CNS disappear
microglial cells
smallest and least numerous, defenders, main form of active immune defense in the CNS , protective function such as engulfing pathogens and cellular waste, act as phagocytic cells, derived from white blood cells
ependymal cells aids in
producing and circulating cerebrospinal fluid(CSF) around the CNS
satellite cells
similar to astrocytes
Schwann cells
produce myelin sheaths around axons for PNS
white matter is composed primarily of
myelinated axons
gray matter
containing neuronal cell bodies, dendrites, and axon terminals of neurons, unmyelinated axons, and glial cells
in the _____ ______ , ____ forms an H-shaped inner core that is surrounded by white matter
spinal chord, gray
white matter transmits info ___
faster, less consciously aware
grey matter transmits info
slower, more consciously aware
in the ____, a thin, outer layer of ____ matter covers the cerebrum and cerebellum
brain, gray
ependymal cells
type of endothelial cell that lines the fluid-filled central canal and spinal cord and the ventricles of the brain
tracts
bundles of myelinated axons, in spinal cord and form larger groups called columns
pathways
link centers of brain with rest of body , sensory pathways ascend and carry info to CNS
Motor pathways descend, carry info away from CNS
ganglia
where collections of neurons cell bodies (gray matter) are located, outside of spinal cord
nerves
bundles of axons , both desdonry and motor components , contains myeline sheath (white matter)
two categories of nerves
31 spinal nerves- connected to the spinal cord
12 cranial nerves- connected to the brain
membrane potentials
focus on the protein channels that go thru cell membrane, gated (specific chemical to open) and leak protein channels.
gated channels are generally _____ but can be opened due to ____ or specific chemicals ____
closed, voltage ligands
leak channels are always
opened, potassium ions
ligands
specific chemicals
leak channels
always open, resting membrane has a greater permeability to K+ than Na+ , K+ is the greatest contribution to the resting membrane potential
gated channels
alway closes unless opened by ligands or specific signals or neurotransmitters, voltage-gated channels are opened when ions move, responsible for action potential
resting potential
always negative
nerve impulses
neurons communicate with one another by means of nerve action potentials
resting potential for muscles
-70
nervous resting potential
-90 to -40
generating of action potentials depends on the existence of a ____ ____ _____ and the presence of voltage-gated channels for Na+ and K+
resting membrane potential
resting membrane potential forms
by an unequal distribution of ions on either side of the plasma membrane due to a higher membrane permeability to K+ than to Na+
depolarization for muscles
-50 to -40
depolarization for nerves
-60 to -55, has to fire before muscles
the level of ___ is higher ___
K+ inside
the level of ______ is higher ___
Na+ outside
K+ diffuses out faster than Na+ enters due to
leak channels
during _____ _____, voltage-gated NA+ and K+ channels open in sequence
action potential
depolarization
opening of voltage-gated NA+ channels (-70mV to +30 mV)
threshold potential
level of depolarization required to intake an action potential, once this is reached, the action potential move along the membrane, generating an electrical impulse that is transmitted down the axon
opening of voltage-gated K+ channel allows
repolarization
repolarization
recovery of the membrane potential to the resting level
all or none principle
stimulus is strong enough to reach threshold, the action potential will occur
refractory period
another action potential cannot be generated. this limits the number of neurons that can respond to a stimulus at any given moment
propagation of action potentials
begins with local changes in the membrane in one site
continuous conduction
nerve impulse conduction that occurs as a step-by-step process along an unmyelinated axon
salutary conduction
a nerve impulse leaps from one node of Ranvier to the next along a myelinated axon
Axons with _____ diameters conduct impulses ____ than those with _____ diameters
larger, smaller
myelinated axons conduct impulses _____ than unmyelinated axons
faster
myelin
excellent insulator that prevents almost all ion movement across the cell membrane
myelination of an axon ______ the speed and efficiency of _____ _____ generation along the axon
increases, action potential
