Nerve Flashcards
Functions of NS
- enable body to respond to changes in external/internal environment
- control & integrate functional activities of organs & control systems
- nerve tissue throughout body = communication network
Two major divisions of nervous system
CNS & PNS
Connections of nerve cell bodies outside the CNS are called ____
Ganglia
Functional divisions of NS
Somatic
Autonomic
What division of the NS exercises conscious control over voluntary functions
Somatic NS
What division of the NS controls involuntary functions, acts on smooth & cardiac muscle & some glands?
Autonomic
2 components of ANS
Sympathetic & parasympathetic
Two principal cell types of NS
neurons & glial cells
Structural & functional unit of the NS
Neuron
Supporting cells of NS
Glial cells
Major functions of neuron
Irritability (excitability) & conductivity
Perikaryon
Cell body (soma)
Nissl substance
Corresponds to a stack of concentrated rER
Neurofilaments
Abundant intermediate filaments with cytoskeletal functions
Dendrites
Long, numerous receptor processes, receive stimuli from other neurons at synapses of the external environment
Synapse
Specialized junctions between neurons that transmit impulses
Axon (nerve fiber)
A single long process ending at synapses specialized to generate & conduct nerve impulse to other cells
Axolemma
Plasma membrane of axon
Axon hillock
Pyramid shaped region where axon originates from the perikaryon
The axon hillock lacks ____ but contains _____
Nissl substance; neurofilaments
Neuron classifications by number of processes
- Multipolar neurons
- Bipolar neurons
- Pseudounipolar (unipolar) neurons
- Anaxonic neurons
Neuropil
Processes of glial cells & neurons
Multipolar neuron
Has one axon, and 2 or more dendrites
Eg. Motor neurons & interneurons
Bipolar neuron
Has one dendrite & one axon
Sometimes receptors for special senses
Pseudounipolar (unipolar) neuron
Has single axon that divides close to the cell body, one branch extends to periphery, other towards CNS
Location of unipolar neurons
Found in all other sensory neurons, located close to CNS
Neuron classification by function
- Sensory
- Interneurons
- Motor neurons
Sensory neuron
Receives stimuli (afferent) from internal or external environment & transmit impulses toward CNS
Interneurons
Act as connectors between neurons in a chain or typically between sensory & motor neurons in CNS
Motor neuron
Conducts impulses (efferent) from CNS to target cells
Peripheral NS neuroglial cells
Schwann cells & satellite cells
Function of Schwann cells
- produce myelin
- form mesaxon
- aid in cleaning up PNS debris, guide regrowth of PNS axons
Schmidt-Lanterman clefts
Small islands of Schwann cell cytoplasm within successive lamellae of myelin
Unmyelinated axons of PNS are enveloped by ____
Schwann cells
Node of Ranvier
Junction between adjacent Schwann cells
Satellite cell function
Maintenance of microenvironment: physical support, repair, insulation
- same as Schwann cells but do not make myelin
Difference between Schwann cells & satellite cells
Satellite cells do not make myelin
CNS neuroglial cells
Astrocytes, oligodendrocytes, microglia, ependymal cells
Function of astrocytes
- Physical & metabolic support for CNS neurons
- form BBB
Protoplasmic astrocytes
Have numerous short branching cytoplasmic processes, prevalent in gray matter of brain
Fibrous astrocytes
Fewer processes that are long & delicate, prevalent in white matter of brain
Oligodendrocytes
Small cells that make & maintain myelin in CNS
Functions of microglia
- migratory & phagocytic
- immune defense (APC)
- inflammation & repair process
What is the cell that makes myelin in CNS?
Oligodendrocytes
What cell makes myelin in PNS?
Schwann cells
Ependymal cells
Epithelial-like columnar (to cuboidal) cells lining ventricles & central canal of spinal cord
Ependymal cells are associated with capillaries to form the _____
Choroid plexus
What apical cell surface projections are present on ependymal cells in some areas of CSF?
Microvilli & cilia
Function of choroid plexus
Produce CSF
CT components of peripheral nerves
Endoneurium
Perineurium
Epineurium
Endoneurium
Loose CT surrounding individual nerve fibers (axon)
Perineurium
CT around bundle of nerve fibers (fascicles)
Epineurium
Dense irregular CT surrounding whole peripheral nerve
Regions rich in perikarya and astrocytes comprise the ____
Gray matter
Regions containing tracts of myelinated axons comprise the ____ (no parikarya)
White matter
Cerebellar cortex functions
Coordinates muscular activity, posture, and balance
Three layers of cerebellum
Molecular layer
Purkinjie cell layer
Granular layer
Molecular layer of cerebellum
Contains much neuropil & scattered neuronal cell bodies
Purkinjie cell layer
Characterized by Purkinjie cells (multipolar neurons)
- body position & proprioception
Purkinjie cells
Efferent neuronal cells, conduct impulses from brain to muscles & glands
Granular layer
Contains various small, densely packed neurons (granule cells) and little neuropil
White matter of cerebellar medulla contains….
Myelinated nerve fibers, fibrous astrocytes and microglia (no neuronal cell bodies)
Cerebral cortex (gray matter) is responsible for…
Cognitive thinking, memory, sensory integration, voluntary motor function
Primary cell type in cerebral cortex (gray)
Pyramidal cells
Pyramidal cells
Efferent multipolar neurons conduct impulses outward from brain
- conscious control of muscle movement
