Nervous system
4.10 Nervous tissue responds to stimuli and propagates electrical impulses
throughout the body
Nervous tissue is specialized for the propagation (movement) of electrical impulses.
Nervous tissue derived from ectoderm
2 basic types of cells
1. Neurons; transmit information as electrical impulses
o Axon/nerve fibers; conducts (leiden) that information to other cells;
away from cell body
o Dendrite; receive information; to cell body
o Cell body; large cell body with nucleus and nucleolus (bolvormig object
in celkern)
2. Neuroglia/glial cells; several kinds of supporting cells/regulation. They support
and repair nervous tissue and supply (leveren) nutrients to neurons.
Neurons cannot divide, so they have limited ability to repair themselves after injury.
12.1 The nervous system has anatomical and functional divisions
The anatomical divisions (Plaatje pagina 437)
- Central nervous system (CNS); brand and spinal cord
o Includes nervous tissue + blood vessels + connective tissues (support
and protect them)
o Functions; responsible for integrating, processing and coordinating
sensory and motor commands
Sensory; information about conditions inside or outside the body
Motor commands; control or adjust (aanpassen) organs.
- Peripheral nervous system (PNS); nervous tissue outside the CNS and ENS
Sensory; it delivers sensory information to the CNS; afferent
division
Motor commands; carries motor command to peripheral tissues;
efferent division
- Enteric nervous system; network of neurons and nerve in the walls of the
digestive tract.
The functional divisions
- Autonomic nervous system (ANS); regulatie inwendig organen (niet
beinvloeden)
Parasympathetic division; niet actief zijn
Sympathetic divsion (orthosympatisch); actief zijn
- Somatic nervous system (animaal) (SNS); gewilde bewegingen en reflexen
(beinvloeden)
controls skeletal muscle contraction;
Voluntary contraction; conscious (bewust) control
Involuntary contraction; onconscious control; reflexion
Bundels of axons in PNS nerves
, 12.2 Neurons are nerve cells specialized for intercellular communication
Functional characteristics of neurons
Long lived, high metabolic rate, excitable (prikkelbaar, actipotentiaal) plasma
membrane (like skeletal muscle cells). Mitochondria in neurons generate energy
needed by active neuron. They lack centrioles (organelles that organize the
cytoskeleton during mitosis). The neurons cannot divide. Neural stem cells persist in
the adult nervous system but are inactive.
The structure of neurons
- Large cell body (soma); round nucleus with prominent nucleolus.
o Perikaryon; cytoplasm surrounding the nucleus
Contains; Neurofilaments and neurotubules, are in the
cytoskeleton
Neurofibrils; bundels of neurofilaments
Contains; mitochondria generate ATP
Contains; RER and free ribosomes for synthesize proteins. RER
and free ribosomes give grey color found in brain and spinal
cord.
- Short, branched (vertakt) dendrites; play role in intercellular communication
- Single, long axon; long cytoplasmic process. Propagating electrical impulse
action potential
o Axoplasm; cytoplasm of axon. Contains; neurofibirls, neurotubules,
small vesicles, lysosomes, mitochondria and various enzymes.
o Axolemma; plasma membrane of axon
o Initial segment; axon in a neuron joins the cell body at a thickened
region; axon hillock.
o Collaterals; side branches of axon
- Telodendria; terminal branches of axon
o Telodendra; the main axon and collaterals end in series of fine
telondendria
o Terminal; end of an axon; communicate to other cells; synapse
o Axonal transport; movement of materials between the cell body and
axon terminals
Anterograde flow; from cell body to axon carried by kinesin
Retrograde flow; from axon to cell body carried by dynein
Structural classification of neurons
- Anaxonic; Neurons are small and have numerous dendrites NO axons
o Located in brain and special sense organs
- Bipolar neurons; one dendrite and one axon. Cell body between the two.
o Special sense organs
- Unipolar neurons (pseudounipolar neuron); dendrites and axon are
continuous; cell body lies off to one side.
o Most sensory neurons of the peripheral nervous system.
- Multipolar neurons; 2 or more dendrites and single axon. Cell body by the
dendrite.
o Most common neurons in CNS
4.10 Nervous tissue responds to stimuli and propagates electrical impulses
throughout the body
Nervous tissue is specialized for the propagation (movement) of electrical impulses.
Nervous tissue derived from ectoderm
2 basic types of cells
1. Neurons; transmit information as electrical impulses
o Axon/nerve fibers; conducts (leiden) that information to other cells;
away from cell body
o Dendrite; receive information; to cell body
o Cell body; large cell body with nucleus and nucleolus (bolvormig object
in celkern)
2. Neuroglia/glial cells; several kinds of supporting cells/regulation. They support
and repair nervous tissue and supply (leveren) nutrients to neurons.
Neurons cannot divide, so they have limited ability to repair themselves after injury.
12.1 The nervous system has anatomical and functional divisions
The anatomical divisions (Plaatje pagina 437)
- Central nervous system (CNS); brand and spinal cord
o Includes nervous tissue + blood vessels + connective tissues (support
and protect them)
o Functions; responsible for integrating, processing and coordinating
sensory and motor commands
Sensory; information about conditions inside or outside the body
Motor commands; control or adjust (aanpassen) organs.
- Peripheral nervous system (PNS); nervous tissue outside the CNS and ENS
Sensory; it delivers sensory information to the CNS; afferent
division
Motor commands; carries motor command to peripheral tissues;
efferent division
- Enteric nervous system; network of neurons and nerve in the walls of the
digestive tract.
The functional divisions
- Autonomic nervous system (ANS); regulatie inwendig organen (niet
beinvloeden)
Parasympathetic division; niet actief zijn
Sympathetic divsion (orthosympatisch); actief zijn
- Somatic nervous system (animaal) (SNS); gewilde bewegingen en reflexen
(beinvloeden)
controls skeletal muscle contraction;
Voluntary contraction; conscious (bewust) control
Involuntary contraction; onconscious control; reflexion
Bundels of axons in PNS nerves
, 12.2 Neurons are nerve cells specialized for intercellular communication
Functional characteristics of neurons
Long lived, high metabolic rate, excitable (prikkelbaar, actipotentiaal) plasma
membrane (like skeletal muscle cells). Mitochondria in neurons generate energy
needed by active neuron. They lack centrioles (organelles that organize the
cytoskeleton during mitosis). The neurons cannot divide. Neural stem cells persist in
the adult nervous system but are inactive.
The structure of neurons
- Large cell body (soma); round nucleus with prominent nucleolus.
o Perikaryon; cytoplasm surrounding the nucleus
Contains; Neurofilaments and neurotubules, are in the
cytoskeleton
Neurofibrils; bundels of neurofilaments
Contains; mitochondria generate ATP
Contains; RER and free ribosomes for synthesize proteins. RER
and free ribosomes give grey color found in brain and spinal
cord.
- Short, branched (vertakt) dendrites; play role in intercellular communication
- Single, long axon; long cytoplasmic process. Propagating electrical impulse
action potential
o Axoplasm; cytoplasm of axon. Contains; neurofibirls, neurotubules,
small vesicles, lysosomes, mitochondria and various enzymes.
o Axolemma; plasma membrane of axon
o Initial segment; axon in a neuron joins the cell body at a thickened
region; axon hillock.
o Collaterals; side branches of axon
- Telodendria; terminal branches of axon
o Telodendra; the main axon and collaterals end in series of fine
telondendria
o Terminal; end of an axon; communicate to other cells; synapse
o Axonal transport; movement of materials between the cell body and
axon terminals
Anterograde flow; from cell body to axon carried by kinesin
Retrograde flow; from axon to cell body carried by dynein
Structural classification of neurons
- Anaxonic; Neurons are small and have numerous dendrites NO axons
o Located in brain and special sense organs
- Bipolar neurons; one dendrite and one axon. Cell body between the two.
o Special sense organs
- Unipolar neurons (pseudounipolar neuron); dendrites and axon are
continuous; cell body lies off to one side.
o Most sensory neurons of the peripheral nervous system.
- Multipolar neurons; 2 or more dendrites and single axon. Cell body by the
dendrite.
o Most common neurons in CNS
