NERVOUS SYSTEM Flashcards
what are the functions of the nervous system
receiving sensory input
integrating information
controlling muscles and glands
maintaining homeostasis
establishing and maintaining mental activity
two major divisions of the nervous system
central nervous system (CNS)
peripheral nervous system (PNS)
consists of the brain and spinal cord
CNS
consists of all the nervous tissue outside CNS including nerves and ganglia
PNS
the communication link between CNS and the various parts of the body ; carries information about the different tissues of the body to the CNS and delivers commands
PNS
PNS can be divided into 2 parts
sensory division or afferent (toward)
motor division or efferent (away)
conducts action potentials from sensory receptors to the CNS
sensory division
conducts action potentials from the CNS to effector organs such as muscles and glands
motor division
the neurons that transmit action potentials from the CNS toward the periphery are called the
motor neurons
the effectors controlled by motor division include
muscle tissue and glands
components of motor division
somatic nervous system
autonomic nervous system
transmits action potentials from the CNS to skeletal muscles
somatic nervous system
transmits action potentials from the CNS to cardiac muscle, smooth muscle, and glands
autonomic nervous system
divisions of autonomic nervous sytem
sympathetic divison
parasympathetic division
a unique part of the peripheral nervous system ; has both sensory and motor neurons contained wholly within the digestive tract
enteric nervous system (ENS)
two types of cells that make up the nervous system
neurons
glial cells
type of cell that receives stimuli, conduct action potentials, and transmit signals to other neurons or effector organs
neurons or nerve cells
3 parts of a neuron
cell body
dendrites and axons (2 types of processes)
contains a single nucleus
cell body
each neuron has an _, a single long cell process extending from the neuron cell body
axon
the area where the axon leaves the neuron cell body is called the
axon hillock
an axon may remain unbranched or may branch to form
collateral axons
axons can be surrounded by a highly specialized insulating layer of cells called the
myelin sheaths
axons of __ conduct action potentials towards the CNS
sensory neurons
axons of __ conduct action potentials away from the CNS
motor neurons
3 categories of neurons based on the arrangement of their processes
multipolar neurons
bipolar neurons
pseudo-unipolar neurons
have many dendrites and a single axon
multipolar neurons
has two processes– one dendrite and one axon ; located in some sensory organs such as the retina of the eye and nasal cavity
bipolar neurons
have a single process extending from the cell body ; this process divides into two extensions a short distance from the cell body
psuedo-unipolar neurons
are the supportive cells of the CNS and PNS, meaning these cells do not conduct action potentials instead carry out different activities that enhance neuron function and maintain normal conditions within nervous tissue
glial cells or neuroglia
4 types of glial cells in the CNS
astrocytes
ependymal cells
microglia
oligodendrocytes
2 types of glial cells in the PNS
schwann cells
satellite cells
type of glial cells in the CNS that serve as the major supporting cells ; can stimulate or inhibit the signaling activity of nearby neurons ;
astrocytes
astrocytes participate with blood vessel endothelium to form a permeability barrier called the __ between the blood and the CNS
blood-brain barrier
type of glial cells in the CNS that line the fluid-filled cavities (ventricles and canals) ; some produce cerebrospinal fluid or help move the fluid
ependymal cells
type of glial cells in the CNS that acts as immune cells ; they help protect the brain by removing bacteria and cell debris
microglia
type of glial cells in the CNS that provide insulating material that surrounds axons
oligodendrocytes
type of glial cells in the PNS that provide insulating material around axons
schwann cells
type of glial cells in the PNS that are found around the cell bodies of certain neurons of the PNS ; these cells provide support and nutrition to the neurons from heavy-metal poisons such as lead and mercury
satellite cells
are specialized layers that wrap around the axons of some neurons ; formed by the processes of oligodendrocytes in the CNS and schwann cells in the PNS
myelin sheaths
axons with these myelin sheaths are called
myelinated axons
gaps in the myelin sheath are called __ that occur about every millimeter between the myelinated areas
nodes of ranvier
nervous tissues exist as what colors
gray and white matter
this type of matter consists of groups of neuron cell bodies and their dendrites where there is little myeline
gray matter
in the CNS, gray matter on the surface of the brain is called the
cortex
in the CNS, clusters of gray matter located deeper within the brain are called
nuclei
in the PNS, a cluster of neuron cell bodies is called a
ganglion
type of matter that consists of parallel axon with their myelin sheath which are whitish in color
white matter
white matter of the CNS forms _ which propagate action potentials from one area of the CNS to another
nerve tracts of conduction pathways
white matter of the PNS consists of bundles of axons and associated connective tissue that form
nerves
two basic types of ion channels
leak channels
gated channels
are always open ; ions can leak across the membrane down their concentration gradient
leak channels
are closed until opened by specific signals
gated channels
are opened by specific chemicals
chemically gated channels
are opened by a change in the electrical property of the cell membrane
voltage-gated channels
inside of most cell membrane is _ charged while the outside is _ charged
negatively:positively
this uneven charge distribution across the cell membrane means that the membrane is
polarized
in an unstimulated cell, we refer to this as the
resting membrane potential
in neuron communication, these changes can lead to _ which are electrical signals that are conducted along the cell membrane from one region of the cell to another
action potentials
on stimulation, chemically gated channels are opened and initiate
local potentials
if sufficiently strong, the local potentials activate voltage gated channels to initiate an _ potential
action
action potentials occur in an
all-or-none fashion
the pattern of action potential conduction along a neuron cell membrane may occur in one of two ways
continuous conduction
saltatory conduction
in unmyelinated axons, _ conduction occurs ; action potential in one part of a cell membrane stimulates local currents in adjacent parts of the cell membrane
continuous
in myelinated axons, _ conduction occurs ; action potential at one node of ranvier causes a local current to flow through the surrounding extracellular fluid and through the cytoplasm of the axon to the next node
saltatory
is a junction where the axon of one neuron interacts with another neuron or with cells of an effector organs such as a muscle or gland
synapse
3 major components of synapse
presynaptic terminal
postsynaptic terminal
synaptic cleft
the end of axon forms __
presynaptic terminal
the membrane of dendrite or effector cell is the
postsynaptic membrane
the space separating the presynaptic and postsynaptic is the
synaptic cleft
chemical substances called __ act as chemical signals
neurotransmitters
neurotransmitters are stored in __ in the presynaptic terminal
synaptic vesicles
if K+ or Cl- channels open, the inside of the postsynaptic cells tend to become more negative or __ and an action potential is inhibited from occurring
hyperpolarized
of the many neurotransmitters or suspected neurotransmitter substances, the best known are
acetylcholine and norepinephrine
in synapses where the acetylcholine is the neurotransmitter, such as in the neuromuscular junction, an enzyme called __ breaks down the acetylcholine
acetylcholinesterase
the two simplest pathways in the CNS are
converging pathway
diverging pathway
in this pathway, two or more neurons synapse with the same postsynaptic neuron ; allows information transmitted in more than one neuronal pathway to converge into a single pathway
converging pathway
in this pathway, the axon from one neuron divides and synapses with more than one other postsynaptic neuron ; this allows information transmitted in one neuronal pathway to diverge into two or more pathways
diverging pathway
many presynaptic action potentials are needed in a process called __ ; allows integration of multiple subthreshold local potentials
summation
two types of summation
spatial summation
temporal summation
type of summation that occurs when the local potentials originate from different locations on the postsynaptic neuron
spatial summation
type of summation that occurs when local potentials overlap in time ; can occur from a single output rapidly which allows the resulting local potentials to overlap briefly
temporal summation
the nerves of the PNS can be divided into how many groups
2 groups: 12 pairs of cranial nerves and 31 pairs of spinal nerves
collects information from numerous sources both inside and on the surface of the body and relays it by way of sensory neurons to the CNS
PNS
extends from the foramen magnum at the base of the skull to the second lumbar vertebra ; communicate between the spinal cord and the body
spinal cord
the inferior end of the spinal cord and the spinal nerves exiting there resemble a horse’s tail and are collectively called
cauda equina
the white matter consists of
myelinated axons
the gray matter consists of a
collection of neuron cell bodies
the white matter in each half of the spinal cord is organized into three columns
dorsal column
ventral column
lateral column
consists of axons that conduct action potentials toward the brain
ascending tracts
consists of axons that conduct action potentials away from the brain
descending tracts
the gray matter is shaped like a letter
H
components of gray matter
dorsal horns and ventral horns
exist in the levels of the spinal cord associated with the autonomic nervous system
small lateral horns
the ventral rootlets combine to form a
ventral root
is a fluid filled space in the center of the spinal cord
central canal
dorsal roots combine to form
dorsal root
it contains the cell bodies of pseudo-unipolar sensory regions
dorsal root ganglion
an involuntary reaction in response to a stimulus applied to the periphery and transmitted to the CNS
relfex
is the neuronal pathway by which a reflex occurs ; the basic functional unit of the nervous system
reflex arc
the simplest reflex is the __ ; is a classic example of the stretch reflex involving the spinal cord
knee-jerk reflex or patellar reflex
type of reflex that involves removing a limb or another body part from painful stimulus ; sensory receptors are pain receptors
withdrawal reflex
