Nervous System 1

function of sensory components

• detect the environmental changes

• feel the pain

function of integrative components

• process the sensory data coupled with the information stored in memory

function of motor components

• provide for a response to the processed information

• the output, moving away from pain

nervous system function

• a communication network that enables an animal to adjust itself or its parts to changes in the external and internal environments

CNS

• brain

• spinal cord

• myelin is formed by oligodendrocytes

• nodes are broadly exposed to the extracellular space

PNS

• peripheral nervous system

• cranial nerves, spinal nerves

• somatic (voluntary) vs autonomic (involuntary) nervous systems

• outer cytoplasmic processes of adjacent neurolemmocytes overlap to restrict exposure to the extracellular space

  • communicate with Schwann cells at nodes to activate impulse

• autonomic nervous system

autonomic nervous system

• involuntary control

• sympathetic

  • fight/flight

• parasympathetic

  • rest/digest

• enteric

  • gut activity

neurons fuction

• transmit nerve impulses and join with others via synapses

• 100 billion neurons

neurons consist of (7)

• cell body

• dendrites

• axon

• neurilemma

• axolemma

• nodes of ranvier

• telodendritic zone

dendrites

• conducts impulses towards cell body

• provide sites for receiving information from other neurons

• highly branches, large surface area for communication with axons

• many dendrites per neuron

axon

• conducts impulse away from cell body 1 per neuron

• axon + myelin covering = nerve fiber

• arrows indicate direction of impulse conduction

neurilemma

• sheath of schwann

• myelinated axon

axolemma

• plasma membrane of axon

• covers the axon

nodes of ranvier

• regularly spaced intervals by myelin free gaps 

  • interruptions of the sheath

• junctions of adjacent wrappings

• the nerve fiber plasma membrane is directly exposed to fluid

  • exchanges electrolytes and nutrients

  • causes depolarization

• saltatory conduction

  • depolarization action potential jumps from node to node, traveling along myelinated segments

    • faster than unmyelinated

telodendritic zone

• terminal branches/bulbs

glial cells basics

• neuroglia and glia

• provide services to neurons and their environment

  • support, nourishment 

• 10x the amount of neurons

glial cells consist of (5)

• oligodendrocytes

• Schwann cells

• astrocytes

• ependymal cells

• microglia

oligodendrocytes

• myelin sheath formation in the CNS

• cytoplasm is different from Schwann

  • several extensions exist

  • each form wraps around a nerve fiber

• one cell provides a sheath at several axon locations

• axon bulges at the node and is exposed to extracellular space

• wrap around a cell fiber

Schwann cells

• myelin sheath formation in the PNS

• the cytoplasm is wrapped around a nerve fiber many times

• nucleus lied within the cell beneath the neurilemma

• one Schwann cell per axon

astrocytes

• the most numerous

• start shaped

• acts like CT

  • provides support and nourishment

• release excitatory neurotransmitter glutamate in response to stimulation

ependymal cells

• line the ventricles of the brain and the central canal of the spinal cord

• unite with the capillaries to form the choroid plexus

  • where cerebrospinal fluid is produced

microglia

• phagocytic function

• enter the CNS from blood vessels and increases in numbers during inflammatory process or where neuron injury has occurred

polarity of a neuron

• refers to the number of poles or processes that stem from its cell body

bipolar

• one axon and one dendrite extending from the cell body

• found in the retina and olfactory region

multipolar

• many branching dendrites and one axon extending from the cell body

• most neurons in the CNS

nucleus

• a group of nerve cell bodies within the brain for spinal cord

  • CNS

ganglion

• a group of nerve cell bodies outside the brain or spinal cord

  • PNS

tract or a fasciculus

• a bundle of parallel neuron fibers within the brain or spinal cord

  • CNS

nerve

• bundle of neuron fibers outside the brain or spinal cord 

  • PNS

synapse function

• provides continuity from one neuron to the next

• important characteristics

  • one way conduction

  • facilitation

    • repeated impulse provides for easier subsequent transmission

  • greater fatigability than the neuron

    • allows for repetitive impulses to fade

sypase areas (4)

• synaptic gap

• terminal bulb

• synaptic vesicles

• presynaptic neuron and postsynaptic neuron

synaptic gap

• between terminal bulb and dendrite 

• no physical contact of neurons at the synapse

• a space exists between the neurons

• impulses are transmitted by chemical means

  • chemical synaptic transmission

• conductor that facilities information movement

terminal bulb

• swelling at axon end

• fits into the indentation of the postsynaptic cell membrane

• come in close contact with each other but never touch

synaptic vesicles

• inside the terminal bulb

• contain neurotransmitters

myelin

• a white lipid substance that forms a sheath around nerve fibers and serves as an electrical insulator 

  • helps propagate the nerve impulse, insulator 

  • myelinated? faster conduction

• formed by oligodendrocytes in CNS and by Schwann cells

unmyelinated fibers

• uninsulated because they maintain a direct association with extracellular fluid