Signals that are carried away from the CNS by nerve fibers of PNS to innervate muscles to contract/or glands to secrete
Motor (efferent) neurons
Signals carried by nerve fibers of PNS to CNS (picked up by sensory receptors throughout the body)
Sensory (afferent) neurons
Basic organs/structures of the CNS
- Brain
- Spinal Cord
Function of the peripheral nervous system
to link all regions of the body to the CNS via nerves
peripheral nerves that extend from the brain and carry signals to and from the brain
Cranial Nerves
peripheral nerves that extend from the spinal cord and carry signals to and from the spinal cord
Spinal Nerves
clusters of neuronal cell bodies located outside of the CNS
ganglia
Basic components of the PNS
- Cranial and Spinal nerves (peripheral nerves)
- ganglia
Excitatory cells, basic structural unit of the nervous system
Neurons
Function of neurons
conduct electrical impulses from one part of the body to another, rapid signals along the plasma membrane in the form of nerve impulses= action potentials
3 main characteristics of neurons
- Extreme longevity
- No mitotic division
- High metabolic rate
components of a cell body
- single nucleus
- cytoplasm
- chromatophilic bodies
- neurofibrils
location of cell bodies
in CNS, except for ganglia
Function of a dendrite
receptive site for receiving signals from other neurons and transmitting signals towards cell body
location where axons arise
axon hillock
relationship between axon diameter and resistance of electrical current
inverse; increased axon diameter= decreased electrical current resistance which results in a faster impulse
function of axon
impulse generator and conductor transmits impulses away from the cell body
structural support components of axons
- neurofilaments
- actin microfilaments
- microtubules
axon branching developed at right angles
axon collaterals
where does axon branching occur?
terminal branches
Where do axons end?
axon terminals
classification of neuron with >2 processes, multiple dendrites (extending from cell body) and 1 axon
Multipolar
examples of multipolar nuerons?
Interneurons (mostly) & motor neurons
classification of neuron with 2 processes, fused dendrite and one axon extend from opposite sides of the cell body
Bipolar
example of bipolar neurons?
specialty sensory organs (e.g. inner ear, olfactory epithelium of the nose, retina of the eye)
classification of neurons with one short single processes near cell body that divides into two branches (central= axon that extends to CNS) and (peripheral=dendrite that extends to periphery receptors)
Unipolar
example of unipolar neurons?
dorsal root ganglia (along spinal cord) and sensory ganglia of cranial nerves
what structural classification are sensory neurons?
unipolar neurons
most abundant glial cell in the CNS
astrocytes
glial cells that wrap around thin axons (unmyelinated) in the CNS
astrocytes
glial cells with radiating processes with bulbous endings cling to neurons and/or capillaries
astrocytes
glial cells that extract blood sugar from capillaries for energy in the CNS
astrocytes
glial cells whose functions are sensing the release of NTs, regulating levels of NTS by increasing uptake, signal increased blood flow in capillaries in active regions of the brain, take up and release ions, develop neural tissue to form synapses tissue to form synapses, produce BDFT (neutral development), progagate calcium signals for memory
astrocytes
glial cells in CNS that wrap around thicker axons
oligodendrocytes
glial cells in CNS that produce myelin sheaths
oligodendrocytes
smallest and least abundant glial cells in the CNS
microglial
glial cells in CNS with elongated cell bodies and processes with pointy projections
microglial
glial cells in CNS with phagocytes and are monocyte derived
microglial
glial cells in CNS that support the maturation of synaptic clefts
microglial
glial cells in CNS that are single epithelium that line central cavity of the brain and spinal cord
ependymal
glial cells in CNS that form a permeable layer btw CSF and tissue fluid to bathe cells and have cilia to circulate CSF
ependymal
disorder of the immune system attacking the myelin around axons in the CNS, woman are affected more, but develops quicker and more devastating in men
multiple sclerosis
function of myelin sheath
insulating layer that prevents leakage of electrical current, and increases speed of impulse connection
glial cells in PNS that surround cell bodies within ganglia
satellite cells
glial cells in CNS that surround axons in the PNS and form myelin sheaths arround thick akons in concentric layers and contain neurilemma and nodes of ranvier
schwann cells
outermost nucleated cytoplasmic layer of Schwann cells external to myelin sheath cells
neurilemma (sheath of schwann)
gaps along the axon btw adjacent Schwann cells
Node of Ranvier
which type of axon conduces impulses more slowly?
thin axons
most common locations of thin axons
autonomic nervous system, sensory fibers
membrane bound sacs that contain NTs
synaptic vesicles
function of increased mitocondria in axon terminal?
provides energy for the secretion of NTs
cable like structures in the PNS that consist of numerous parallel axons wrapped around in connective tissue
Nerves
what are the main structures in a nerve?
- schwann cells
- endoneurium
- nerve fascicles
- epineurium
- blood vessels
layer of connective tissue covering schwann cells in a nerve
Endoneurium
groups of axons bundled by a perineurium in a nerve
nerve fascicles
tough, fibrous sheath surroundin nerves
epineurium
location of gray matter
hollow central cavities of the CNS
what is gray matter composed of?
- clusters of neuron cell bodies
- dendrites
- short unmyelinated axon of interneurons
- neuroglia cells
what does the dorsal half of gray matter contain?
cell bodies of interneurons
what does the ventral half of gray matter contain
cell bodies of motorneurons
what gives white matter its color?
myelin
what is white matter composed of?
bundles of myelinated axons
2 main differences btw white and gray matter
- gray matter has neural cell bodies and white matter lacks them
- gray matter predominately unmyelinated and white matter has mostly myelianated axons
function of gray matter interneurons
- process and receive sensory information
- direct information to specific CNS regions and or to cell bodies of motor neurons in ventral spine
- initiate appropriate motor response
function of white matter interneurons
transport information (sensory and motor) from one area of the CNS to another
simple chains of neurons
reflex arcs
rapid voluntary automatic motor response to stimuli
reflex
two types of reflexes
- somatic (skeletal muscle)
- visceral (smooth muscle, cardiac and glands)
component of a reflex arc that is the terminal end of sensory nerve and where the stimulus acts
receptor
component of a reflex arc that transmits afferent impulse to CNS
sensory neuron
component of a reflex arc in which one or more synapses in gray matter (CNS) and is monosynaptic
integration center
component of a reflex arc that conducts efferent impulses to an effector
motor neuron
component of a reflex arc that is a muscle or gland that responds to efferent impulses by contraction or secretion
effector
order of the reflex arc
- receptor
- sensory neuron
- integration center
- motor neuron
- effector
reflex composed of one sensory neuron + motor neuron + synapse
(no interneuron) and is fast
monosynaptic reflex
example of a monosynaptic reflex?
stretch reflexes–knee jerk
function of knee jerk reflex?
helps maintain equalibrium and upright posture
reflex composed of one or more interneurons part pathway between sensory neurons and motor neurons
polysynaptic relfex
example of a simple polysynaptic reflex?
withdrawal reflex
how many interneurons, synapses and neurons does the withdrawal reflex have?
- 1 interneuron
- 2 synapses
- 3 neurons
neural circuit in which one presynaptic neuron synapses with multiple other neurons
Diverging Circuit
neural circuit in which neurons synapse on a single postsynaptic neuron and a single motor neuron may receive both excitatory and inhibitory messages
Converging circuit
neural circuit in which one neuron in the circuit receives feedback from another neuron in the same circuit
Reverberating circuit
examples of what circuit are motor neurons that innervate the stretch muscles and stimulate contraction, interneurons that inhibit the activity of the antagonistic muscle groups, and interneurons that project sensory information to the brain
Diverging circuit
example of reverberating circuits?
rhythmic activities e.g. breathing
input processing in which neurons pass a signal to a specific destination in sequence along a single pathway from one neuron to the next
serial processing
examples of serial processing
- reflex arcs
- long chain of interneurons carrying a sensory signal to the brain
path of the withdrawal reflex
- nerve impulse travel to spinal white matter
- extends as a ascending pathway to brain
- integration in gray matter
- voluntary motor response
input processing in which single sensory stimulus results in multiple perceptions, single neuron is sent along two or more parallel pathways, sense multiple perceptions at once
parallel processing
example of parallel processing
withdrawal reflex