cells of NS - Exam 2

Nervous system

Master controller of body; communicating rapidly via electrical and chemical signals

Sensory input in the nervous system

Receptors monitoring changes externally (environment) and internally (body conditions)

Integration in the nervous system

System processes and interpret sensory signals decide bodies response

Motor output in the nervous system

System sends signals to activate affect organs of the muscle and glands to create response

central nervous system

The brain and spinal cord; functions as central integration and command center

peripheral nervous system

All nerve tissue outside the central nervous system; cranial and spinal nerves; the communication pathway carrying messages to and from the brain

somatic afferent fibers of PNS

Transmit impulses from skin, skeletal muscle and joints to the brain

visceral afferent fibers of PNS

Transmit impulses from internal visceral organs to the brain

sensory division of the PNS

Carry sensory impulse towards CNS

motor division of PNS

Transmit impulses away from CNS to effector organs

somatic nervous system of PNS

Voluntary conscious movement of skeletal muscles

autonomic nervous system of PNS

Involuntary regulate smooth muscle, cardiac muscle and glands

divisions of ANS autonomic nervous system

Sympathetic: fight or flight; parasympathetic: rest and digest

neurons

Excitable cells acting as primary structural and functional units of NS

Long lived and specialized for electrical signaling and cell to cell communication

Increase metabolic rate and is automatic (can't divide)

perikaryon/soma cell body

Biosynthetic center and focal point for neuronal processes outgrowth containing: nucleus and nucleus, organelles, neurofibril, nissle bodies, axon Hillock

dandrites

Highly brands receptive regions that gives large surface area to receive incoming signals

Transmit electrical impulses towards cell body

Always unmyelinated

axon

Transmit nerve impulses away from the cell body towards target cells and ends at axonal terminals, which secrete neurotransmitters

axon transport direction

Anterograde transport: move towards external terminals (vesicles, mitochondria, enzymes)

Retrograde transport: move away from the terminal boutons back towards cell body (recycled/waste)

nuclei

Clusters of cell bodies in the CNS

ganglia

Clusters of cell bodies in the PNS

tracts

Bundles of axons/processes in the CNS

Nerves

Bundles of axons/processes of the PNS

sensory afferent neurons

Transmit impulses towards CNS from sensory receptors

interneurons

shuttle signals through complex pathways within CNS; make up major majority of neurons

motor efforent neurons

Carry impulses away from CNS to affect their organs of muscles and glands

multipolar neurons

Possess many processes of one axon and multiple dendrites

Most common type found in CNS interneurons and motor neurons

bipolar neurons

Possessed two processes, one fuse dandrite, and one axon, extending off opposite sides of the central cell body

Rare found in special sense organs of eyes for vision and nose for smell

unipolar/pseudounipolar neurons

Possess a single process, extending from cell body branching into central and peripheral axon processes

Typical of primary sensory neurons

axonic neurons

Multiple dendrites but no axon

neuroglia

Supporting cells surrounding and wrapping neurons, providing physical support, nourishment, and protection, and metabolic regulation

Conduct electrical signals and maintain essential environment, allowing neurons to function

Astrocytes

Most abundant versatile and highly branched, glial cells and CNS

Release Cleo transmitters glutamate for excitatory, ATP as inhibitory, adenosine and D-serine as modulate neuronal signaling

Helps the blood brain barrier

Microglia

Specialized brain, micro, fridges and serve as primary immune defense of CNS monitor neuron health and phagocytic invading microorganisms, pathogens, and dead cells

When overactive microglia release free radicals leading to oxidative stress

Ependymal cells

Line central cavities of brain, ventricles, and central canal of spinal cord

Form semipermeable barrier, regulating fluid exchange between cerebral spinal fluid and brain nervous tissue

oligodendrocytes

Branch cells with multiple extensions, wrapping around processes of multiple axons within the central nervous system, forming protective and insulating myelin sheets increasing signal conduction speed

Schwann cells (neurolemocytes)

Form PNS Myelin sheaths/neurilemma

A nerve regeneration via neurotrophic factors like NGF, BDNF, neurotrophin-3, to guide axonal regrowth

blood brain barrier

Separates blood-borne substances from neurons

Isolate central nervous system tissues from fluctuations in blood compensation and protecting neurons from harmful substances

Absent in specific brain regions that need to monitor chemical compositions of blood directly such as the hypothalamus and vomiting centers

continuous endothelium with tight junctions of BBB

Preventing solute movement between adjacent cells

thick basil lamina of BBB

Thick basement membrane surrounding endothelial cells that provide secondary physical layer

astrocytes, foot processes of BBB

Perry vascular feet extended by astrocytes, wrapping around outer capillary walls, supporting and maintaining the barrier

substances that diffuse freely

Barrier is in effective at stopping substances that can diffuse directly through plasma membrane without assistance such as lipophilic substances, gases of oxygen and carbon dioxide, alcohol – EtOH

substances requiring special transporter

Water soluble/charge substances can't freely diffuse across lipid membranes and need carrier/transporter proteins to cross BBB

Includes ions, polar molecules, glucose

Myelin sheaths

Provide protection and electrical insulation for axons and increased speed of nerve impulse transmission

is whitish, fatty, lipid protein/phospholipid rich, and segments wrapping surrounding larger and long nerve fibers

myelin generation in PNS

Formed by schwann cells that individually wraps around a single axon segment repeatedly, pushing its cytoplasm and nucleus to outermost layer

Essential for guiding nerve regeneration following in injury

myelin generation and CNS

Formed by oligodendrocytes the extend branched processes to wrap around segments of multiple axons simultaneously

nodes of Ranvier

Gaps occurring at regular intervals in myelin sheets between adjacent myelin forming cells

Contained dense concentration of voltage regulated sodium channels

Saltatory conduction

Myelin sheaths act as electrical insulator, ionic current, can't flow through fatty myelin membranes, forcing it to jump rapidly from the one note of Ranvier to the next along the axon

Drastically increases rate of propagation of nerve impulse