Lecture 11&12 - ORGANIZATION OF NERVOUS SYTEM & NERVOUS TISSUE

how do the effects of the nervous and endocrine systems differ?

nervous system - immediate but brief effect (chemical signals are neurotransmitters)

endocrine system - slower but longer lasting effect (chemical signals are hormones)

what are the 2 primary divisions of the nervous system?

central nervous system and peripheral nervous system

what structures are apart of the central nervous system?

the brain and spinal cord

what structures are apart of the peripheral nervous system?

nervous tissues outside of the CNS (central nervous system), these nerves leading to/from the brain and spinal cord

what are the two types of nervous tissue? what is the function of each?

-neurons

• function: responsible for the transmission of signals/information within the nervous system

-neuroglia

• function: involved in the support, protection, maintenance, and isolation of neurons

what are the general characteristics of neurons?

-have a high metabolic rate

-extreme longevity (can live as long as we do)

-non mitotic (do not divide)

what is the general structure of a neuron? which direction does the impulse travel?  make sure that you can draw and label a neuron

-general structures of neurons include:

• the cell body

• dendrites

• axon

-the axon carries impulses away from the cell body (toward the target)

what is the difference between ganglia and nuclei? how are they similar?

-ganglia are in the Peripheral Nervous System

-nuclei are in the central nervous system

-both are formed by clusters of the soma (cell body)

what are the 3 cell junctions/synapses discussed in class? know what structures form each junction (i.e. neurons, muscle, etc)

-synapse: between two neurons (typically between an axon and dendrite)

-neuromuscular junction: between axon and muscle

-neuroglandular junction: between axon and gland

what are the 3 structural classifications of neurons? how do they differ? what type of information does each carry?

3 STRCUTURAL CLASSIFICATIONS

• multipolar

multiple short dendrites

single, long axon

typically motor in function

most abundant type

• bipolar

single dendrite (may be branching)

long single axon

found in specialized sensory organs like ear, nose, eye

• unipolar

contain one process that splits near the cell body (called a neurite+consists of both dendrites and the axon)

usually sensory in function

what are the 3 functional classifications of neurons? which direction does the impulse travel in each?

3 FUNCTIONAL CLASSIFICATIONS

• sensory (afferent) neurons

carry impulses toward the CNS from sensory receptors in the organs

most are unipolar neurons

cell bodies are located outside the CNS (form ganglia)

• motor (efferent) neurons

carry impulses away from the CNS towards effectors (effectors=muscles/glands)

most are unipolar neurons with cell bodies in the CNS

• interneurons

transmit information between neurons

found within the CNS
most are unipolar

what are effectors?

muscles/glands

know the various neuroglia discussed in class. what is the function of each? where is each found (CNS or PNS)

3 TYPES OF NEUROGLIA IN THE CNS

• astrocytes

most abundant glial cells

crowded amongst neurons in the CNS

functions: maintain the blood barrier, create a 3 dimensional framework for the CNS, and recapture and recycle released neurotransmitters

• oligodendrocytes

wrap around axons in the CNS

functions: produce myelin (forms “white matter” of CNS), protective sheath around axons

• microglia

phagocytic macrophages of the CNS (engulf invading microorganisms and injured/dead neurons)

functions: immune defenders in the CNS, clearing dead cells and pathogens

know the various neuroglia discussed in class. what is the function of each? where is each found (CNS or PNS)

3 TYPES OF NEUROGLIA IN THE PNS

• schwann cells

wrap around PNS neurons

functions: support and insulate the axon, produce myelin

what are myelin sheaths? how do they increase the speed/rate of transmission?

-myelin: lipid-protein complex that forms concentric circles that surround the axon

-improves the speed of nerve impulses

-forms the nodes of ranvier

• gaps in between myelin sheaths on the axon

• allows for regeneration of the action potential—→speeds up the rate of transmission

be able to draw and label a synapse. for reference, use the synapse from lecture. know the sequence of events in impulse transmission.

SEQUENCE OF EVENTS IN IMPULSE TRANSMISSION

• presynaptic electrical impolses—>

• rupture of synaptic vesicles —→

• release of neurtransmitters across the cleft —→

• neurotransmitters binds to postsynaptic membrane, changing its electrical charge —→

• new postsynaptic impulse