01:119:116 Lecture Notes - Lecture 19: Sympathetic Nervous System, Ependyma, Hindbrain
11 Mar 2016
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Lecture 19
Nervous System II
Ch. 49.1-49.3
The ability to be able to response of stimuli increases the chance of survival and so you could
then reproduce and be all happy yay
I. Comparison of different types of nervous systems (how they are organized)
A. Cnidarians ex) Hydra
1. simplest animals that have a nervous system
2. no central control organ
a) no brain
3. instead, they are characterized by a nerve net
a) interconnected nerve cells
4. Impulses are conducted in both directions and spread throughout the
nerve net
B. Sea Star (echinoderm)
1. organization where nerves are formed from the axons of multiple neurons
a) we have a bundle of axons from several neurons
2. there is a structure called a nerve ring
a) it is a central control structure
3. there are radial nerves
a) the function is to receive information from the nerve ring and to
send appropriate signals to the muscles
C. Bilaterally symmetrical animals (more complex)
1. Planarian (platyhelminthes)
a) simplest clearly defined central nervous system
b) brain and also an eyespot (to detect stimuli)
(1) found at the anterior end of the organism
c) they have a ladder type nervous system
(1) there are 2 longitudinal nerve cords
(2) there are also many transverse nerves that connect the 2
longitudinal nerve cords
2. Annelids and Arthropods
a) seeing increasing complexity
b) brain is more complex
c) they are characterized by ganglia
(1) clusters of neurons
(2) they occur in repeated patterns (segmentally arranged)
(3) Figure 49.2- Nervous system organization
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D. Lifestyle (The complexity of the nervous system usually correlates with the
lifestyle of the organism)
1. Chiton (mollusc)
a) slow-moving
b) simple
2. Squid (mollusc)
a) active-predator
b) have more complex nervous system
c) Figure 49.2- compare chitin and squid
E. Vertebrates (increasing complexity)
1. characterized by brain and spinal cord which comprise the CNS
2. also nerves and ganglia (cluster of neurons) which comprise the PNS
3. Figure 49.2- you’ll see a salamander which has a vertebrate
II. Glial Cells (Support cells within the nervous system)
A. Several types
1. Ependymal cells (one type of glial cells)
a) found lining the cavities of the CNS
b) characterized by cilia
(1) cerebrospinal fluid
2. Astrocytes (one type of glial cells)
a) CNS
b) dilate blood vessels that are located near active neurons
(1) neurons that are actively engaged
(2) more oxygen, more glucose and supporting them in their
activity
c) astrocytes are involved in the composition of the CNS fluids
(1) they remove excess K+ and neurotransmitters
d) astrocytes also stimulate endothelial cells in the blood vessels to
form tight junctions
(1) the endothelial cells are the lining of the blood vessels
(2) tight junctions are found in the CNS
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(a) tight junctions means cells are tightly fitted together
so nothing can pass through
(3) you have the formation of the blood/brain barrier
(a) important because you don’t want anything that
doesn’t belong in your brain… protects the brain
3. Oligodendrocytes (one type of glial cells)
a) found in the CNS
b) their plasma membrane is rich in myelin (a lipid)
c) form the myelin sheath around axons
(1) electrical insulation
(2) saltatory conduction
4. Microglia (one type of glial cells)
a) found near blood vessels in CNS
b) function as immune cells
(1) specifically they are phagocytic cells
(a) phagocytic cells eat other cells
(i) any cellular debris from infection or injury,
these microglia cleans it up!
5. Schwann Cells (one type of glial cells)
a) located in the PNS
b) their plasma membrane is rich in myelin
c) producing the myelin sheath around axon
(1) electrical insulation
(2) Figure 49.3
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The ability to be able to response of stimuli increases the chance of survival and so you could then reproduce and be all happy yay. Comparison of different types of nervous systems (how they are organized: cnidarians ex) hydra, simplest animals that have a nervous system, no central control organ, no brain. 3. instead, they are characterized by a nerve net a) interconnected nerve cells. Impulses are conducted in both directions and spread throughout the nerve net: sea star (echinoderm, organization where nerves are formed from the axons of multiple neurons, we have a bundle of axons from several neurons. 2. there is a structure called a nerve ring a) it is a central control structure. 2: all of the newly formed neurons are going to migrate from the neural tube. Care of by the spinal cord: brain, there are ventricles, cavities, gray matter (no myelin, surrounds white matter, cerebrospinal fluid.
