Chapter 14: Nervous Tissue Flashcards
List and describe the 2 structural divisions of the nervous system.
- Central Nervous System (CNS)
- Brain
- Spinal Cord - Peripheral Nervous System (PNS)
- Cranial Nerves (nerves extending from brain)
- Spinal Nerves (nerves extending from spinal cord)
- Ganglia (clusters of neuron cell bodies located outside CNS)
List and describe the 2 functional divisions of the nervous system.
- Sensory Division (afferent)
- receives sensory info from receptors and transmits info TO the CNS (input) - Motor Division (efferent)
- transmits motor impulses FROM the CNS to muscles or glands (output)
List and describe the 3 general functions of the nervous system.
- Collecting Info
- structures int he PNS detect changes in internal and external environment and pass the info to the CNS - Processing and Evaluating info
- CNS determines what response is required, if any - Responding to Information
- CNS initiates impulses to react to environment
List and describe the functions of the 2 types of sensory division of the nervous system.
Somatic Sensory (afferent) - general sense: touch, pain, pressure, vibration, temp, and proprioception
Visceral Sensory (afferent) - transmit nerve impulse from blood vessels/viscera to the CNS (mostly temp and stretch of organ walls)
List and describe the functions of the 2 types of motor division of the nervous system.
Somatic Motor (efferent) - Conduct nerve impulse from CNS to skeletal muscles
Autonomic Motor (efferent) - innervates internal organs, regulates smooth muscle, cardiac muscle and glands
Describe the functions of the following parts of a nerve cell:
Cell Body
Dendrites
Axon
Be able to label the parts of a typical nerve cell. (Diagram Pg. 417) Cell Body Nucleus Dendrites Axon Myeline Sheath Neurofibril node (Nodes of Ranvier) Synaptic knobs
Cell Body:
- neurons control center
- receives, integrates, and sends nerve impulses
Dendrites:
- shorter, smaller processes that extend off the cell body;
- can have 1 or many
- conduct impulses TOWARD cell body (receive input and transfer it to the cell body
- more dendrites a neuron has, the more impulses that neuron can receive
Axon:
- larger, typically longer process coming from the cell body
- usually only 1
- transmits a nerve impulse away from the cell body
Describe interneurons.
- Located entirely within the CNS
- Multipolar
- Most abundant type of neuron
- The facilitate communication between sensory and motor neurons
List the 4 types of glial cells in the CNS and their basic functions.
(Diagrams Pg. 421)
- Astrocytes
- help form blood brain barrier
- regulates tissue fluid composition
- starlike shape
- most abundant type of glial cell in CNS - Ependymal Cells
- form choroid plexus
- produce cerebrospinal fluid (CSF)
- line the ventricles of the brain and central canal of spinal cord - Microglia
- “garbage men of the CNS”
- exhibit phagocytic activity removing cell debris (dead/dying cells) and protecting against pathogens - Oligodendrocytes
- with CNS axons only
- they wrap around axons and produce myelin
- they are small and can touch multiple axons if they are near them
List the 2 types of glial cells in the PNS and their basic functions.
(Diagrams Pg. 421)
- Satellite Cells
- protect and regulate nutrients for cell bodies in ganglia - Neurolemmocytes (Schwann Cells)
- with PNS axons only
- they wrap around axons and produce myelin
(- Like oligodendrocytes but in the PNS)
List and briefly describe the 2 types of nerve cells in the nervous system.
- Neurons
- excitable; initiate and transmit nerve impulses
- high metabolic rate
- extreme longevity
- non-mitotic (be able to discuss implications of this) - Glial Cells
- non-excitable (do not transmit impulses)
- cells support, protect, and help nourish neurons
- form structural network
- replace damaged neurons
- assist neuronal development
- smaller and capable of mitosis
- brain tumors more likely to be caused by these cells because they are mitotic
- far outnumber neurons
Discuss myelination and why it is important in the nervous system.
Myelin sheath
- protective, fatty coating that wraps around axons giving them a glossy, white appearance
- supports, protects and insulates axon
- Allows saltatory conduction: nerve impulse “jumps” over the neurofibril node (node of Ranvier) this means the nerve impulse travels down the axon more quickly
Without the myelin sheath, continuous conduction occurs which means the impulse cannot jump along the axon and must travel the entire length of the axon. Therefore the impulse travels more slowly.
Myelinated axons require less energy.
Unmyelinated axons conduct nerve impulses from pain stimuli.
Discuss regeneration of PNS axons.
A damaged axon can regenerate if at least some neurolemma remains.
Depends on 3 factors:
1. amt of damage
- neurolemmacyte secretion of nerve growth factors to stimulate outgrowth of severed axons
- distance between site of damaged axon and effector organ (closer it is, the more likely it will regenerate)
Discuss Wallerian degeneration. (What is it and briefly describe the 5 step process.)
(Diagram Pg. 426)
It’s the process by which damaged axons in the PNS regenerate.
- Trauma severs the axon.
- Proximal portion axon seals off and swells while the distal portion of axon and myelin sheath degenerate but the neurilemma survives.
- Neurilemma and endoneurium form a regeneration tube.
- Axon regenerates and remyelination occurs.
- Reinnervation to effector by the axon.
* NOTE: this process is very slow; takes a LONG time. (up to 2 years)
Describe the basic structure of a nerve and be able to label it on a diagram.
(Diagram Pg. 427)
- Nerve is a bundle of parallel axons.
- Has 3 connective tissue wrappings:
1. Endoneurium - deepest layer; very delicate
2. Perineurium - middle layer; wraps axons into fascicle bundles
3. Epineurium - superficial layer; thick layer provides protection and support
Define synapse.
Functional contact of a nerve cell with another nerve cell, or effector, or receptor.
