1. Chapter 12: Nervous System
UNIT B
Chapter 12: Nervous System
Chapter 12: Nervous System
In this chapter, you will learn about the structure and function of the nervous system.
How might a researcher study the effects of frequent head trauma?
How might one determine which part of the brain has been affected by repeated blunt impacts?
Given the available information about CTE, what steps do you feel should be taken to prevent its occurrence (if any)?
Sport-Related Head Trauma and Brain Function. Neurosurgeon Dr. Robert Cantu has studied the brains of many deceased athletes, including hockey and football players. He has found that these players often suffered from chronic traumatic encephalopathy (CTE), a degenerative brain disease caused by repeated blunt impact to the head.
Chapter opener figure background:
Former NHL players Rick Rypien, Wade Belak, and Derek Boogaard had something in common; they were all “enforcers.” They were expected to
fight during hockey games.
There is another similarity among these men. They are all dead. Each died of causes that increasingly seem tied to their activities on the ice. Neurosurgeon Dr. Robert Cantu has studied the brains of many deceased athletes, including hockey and football players. He has found that these players often suffered from chronic traumatic encephalopathy (CTE), a degenerative brain disease caused by repeated blunt impact to the head. CTE seems to manifest itself in addiction, depression, and anxiety, conditions suffered by some or all of the deceased players.
Dr. David Goldbloom, senior medical adviser at Toronto’s Centre for Addiction and Mental Health, thinks it is important not to assume that the deaths of the players were all the result of the same thing. Each was an individual and each had his own mental health history. Rypien and Belak had battled depression, and Boogaard was still recovering from previous concussions. Goldbloom feels that attributing the deaths to CTE is an oversimplification, but he does think further study in this area is worth pursuing.
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2. UNIT B
Chapter 12: Nervous System
Section 12.1
Nervous Tissue
The nervous system coordinates and regulates the functioning of the body’s other systems.
The nervous system consists of two major systems:
Central nervous system (CNS): brain and spinal cord
Peripheral nervous system (PNS):
nerves that carry sensory messages CNS
Nerves that carry motor commands from the CNS to the muscles and glands
nervous system: a type of organ system consisting of the brain, spinal cord, and associated nerves; allows us to respond to external and internal stimuli
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3. ANS: Digestion, breathing, Heartbeat
Parasysympathetic –Rest and Digest
Sympathetics – fight/flight

5. The nervous system contains two types of cells:
UNIT B
Chapter 12: Nervous System
Section 12.1
The nervous system contains two types of cells:
Neurons (Nerve Cells):
transmit nerve impulses between parts of the nervous system
Neuroglia (Glial Cells):
support and nourish neurons,
maintain homeostasis,
form myelin that surrounds neurons,
aid in signal transmission,
destroy and remove the carcasses of dead neurons (clean up).
neurons: a specialized cell that transmits nerve impulses between parts of the nervous system; contained within nervous tissue
neuroglia: cells that support and nourish neurons, maintain homeostasis, form myelin, and may aid in signal transmission
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6. Neuronal Structure
they have a long fibre (axon) which is insulated by a fatty sheath
they have tiny branches (dendrons) which branch further as dendrites at each end.
Nerve: a whitish fiber or bundle of fibers that transmits impulses of sensation to the brain or spinal cord, and impulses from these to the muscles and organs.

7. Most Neurons have three parts:
UNIT B
Chapter 12: Nervous System
Section 12.1
Most Neurons have three parts:
Cell body: contains the nucleus and other organelles
Dendrites: extensions leading toward the cell body that receive signals from other neurons and send them to the cell body
Axon: conducts nerve impulses away from the cell body toward other neurons or effectors
cell body: the part of a neuron that contains the nucleus, as well as other organelles
dendrites: part of the neuron; extensions leading toward the cell body that receive signals from other neurons and send them on to the cell body
axon: part of a neuron; conducts nerve impulses away from the cell body toward other neurons or effectors
Figure 12.2 Types of neurons.
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8. 3 Types of Neurons: UNIT B
Chapter 12: Nervous System
Section 12.1
3 Types of Neurons:
Sensory neurons: detect changes in the environment, take messages to the CNS;
Interneurons: receive input from sensory neurons and other interneurons in the CNS
Motor neurons: take messages away from the CNS to an effector (an organ, muscle fibre, or gland);
Effectors carry out responses to environmental changes
sensory neuron: a type of neuron that takes messages to the central nervous system
interneuron: a type of neuron that receives input from sensory neurons and other interneurons, and then communicates with motor neurons
motor neuron: a type of neuron that takes messages away from the central nervous system to an effector such as an organ, muscle fibre, or gland
Figure 12.2 Types of neurons.
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9. Flow of Information from Receptors to Effectors of Nervous System
Receptors detect a change in the environment (stimulus) and produce electrical impulses in response. Sense organs contain groups of receptors.
Effectors are parts of the body - such as muscles and glands - that produce a response to a detected stimulus. For example:
a muscle contracting to move an arm
muscle squeezing saliva from the salivary gland
a gland releasing a hormone into the blood

10. Reflex Arc: nerve pathway followed by a reflex action
Receptor in the skin detects a stimulus (the change in temperature).
Sensory neurone sends impulses to relay neurone.
Motor neurone sends impulses to effector.
Effector produces a response (muscle contracts to move hand away).
simple reflex action: stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector.

11. UNIT B Chapter 12: Nervous System Section 12.1
The sensory neurons of the peripheral nervous system take nerve impulses from sensory receptors to the central nervous system (CNS), and motor neurons take nerve impulses from the CNS to muscles and glands.
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14. The nervous system contains two types of cells:
Neurons:
transmit nerve impulses between parts of the nervous system
Neuroglia (Glial Cells):
support and nourish neurons,
maintain homeostasis,
form myelin that surrounds neurons,
aid in signal transmission,
destroy and remove the carcasses of dead neurons (clean up).

15. Neuroglia is found in both CNS and PNS
Glial Cells in CNS Glial Cells in PNS
Oligodendrocytes Satellite Cells
Astrocytes Schwann cells
Microglia
Ependymal Cells

16. Neuroglia Glial Cells of CNS
Oligo - support and insulation to axons, myelin sheath, which is 80% lipid and 20% protein.
Astrocytes -most numerous, regulate the transmission of electrical impulses within the brain. axon guidance and synaptic support, control of the blood brain barrier and blood flow. Different kinds.
Microglia -mediate immune responses in CNS by acting as macrophages, clearing cellular debris and dead neurons from nervous tissue through the process of phagocytosis
Ependymal Cells - line the CSF-filled ventricles in the brain and the central canal of the spinal cord

17. Glia of CNS
Oligodendrocytes - support and insulate axons Astrocytes -regulate transmission of electrical impulses in brain. Microglia -mediate immune responses in CNS by acting as macrophages, clearing cellular debris and dead neurons from nervous tissue through the process of phagocytosis Ependymal Cells - line the CSF-filled ventricles in the brain and the central canal of the spinal cord

18. Glial Cells of PNS
Satellite Cells – cover the surface of nerve cell bodies
Schwann cells – produce myelin in PNS

19. Glial Cells of PNS
Satellite Cells – cover the surface of nerve cell bodies Schwann cells – produce myelin in PNS

20. Myelin Sheath UNIT B Myelin:
Chapter 12: Nervous System
Section 12.1
Myelin Sheath
Some axons are covered by a protective myelin sheath.
Myelin:
proteins and phospholipids forming a whitish insulating sheath around many nerve fibers,
increase the speed at which impulses are conducted.
myelin sheath: a protective covering on axons
Schwann cells: a type of neuroglia that forms a myelin sheath around axons in the peripheral nervous system
nodes of Ranvier: gaps in the myelin sheath covering the axon
Figure 12.3 Myelin sheath. a. In the PNS, a myelin sheath forms when Schwann cells wrap themselves around an axon. b. Electron micrograph of a cross section of an axon surrounded by a myelin sheath.
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21. Myelin Sheath

22. UNIT B
Chapter 12: Nervous System
Section 12.1
Myelin in the PNS
produced by Schwann cells by wrapping around axon and laying down many layers of plasma membrane
Each Schwann cell myelinates only part of an axon, leaving gaps called nodes of Ranvier
The myelin sheath plays an important role in nerve generation in the PNS
If an axon is severed, the myelin sheath remains and serves as a passageway for new fibre growth
oligodendrocytes: a type of neuroglia that produces myelin in the central nervous system
MS disease degenerative. Lesions develop and become hardened scars (plaques) interfere with normal conduction of impulse  neuromuscular symtoms
Long axons have myelin sheaths short don’t. grey matter doesn’t because short tracts of interneiruons. Surface of brain is gray matter white matter lies deeper. Central part of SC is gray )ooposite) white on outside.
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23. Myelin in the CNS: produced by oligodendrocytes
Nerve regeneration does not occur to any significant degree in the CNS

24. 2 Types of Nervous tissue in the CNS:
UNIT B
Chapter 12: Nervous System
Section 12.1
2 Types of Nervous tissue in the CNS:
Grey matter
Contains neurons with short, non-myelinated axons
Found in the surface layer of the brain and the central part of the spinal cord
White matter
Contains myelinated axons that run together in bundles called tracts
Found deep within the grey matter of the brain and surrounds the grey matter in the spinal cord
grey matter: a type of nervous tissue making up the central nervous system; contains neurons with short, nonmyelinated axons
white matter: a type of nervous tissue making up the central nervous system; contains myelinated axons that run together in bundles called tracts
tracts: bundles of myelinated axons in white matter in the central nervous system
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25. Brain

27. Check Your Progress UNIT B
Chapter 12: Nervous System
Section 12.1
Check Your Progress
Identify the three classes of neurons, and describe their relationship to each other.
Describe the three parts of a neuron.
Distinguish the cell types that form the myelin in the PNS versus the CNS.
Review the structure of grey matter and white matter, and describe where each is found in the CNS and the PNS.
ANSWERS
1. Sensory neuron: Take messages from a sensory receptor to the central nervous system
Interneuron: Sum up messages from sensory neurons and other interneurons and communicate with motor neurons
Motor neuron: Take messages away from the CNS to the effector organs, muscles, or glands
2. Most neurons contain dendrites (signal-receiving extensions leading to the cell body), a cell body containing a nucleus and other organelles, and an axon, which conducts nerve impulses from the cell body to other neurons or effectors.
3. Myelin is formed by Schwann cells in the PNS and by oligodendroglial cells in the CNS.
4. Grey matter contains nonmyelinated neurons; in the white matter the nerve fibres are myelinated. The brain (CNS) has grey matter on the surface and white matter in the deeper tissue. In the spinal cord (CNS) the grey matter forms a butterfly shape in the centre and the white matter surrounds this. In the PNS the long extensions of neurons (dendrites in the sensory neurons and axons in the motor neurons) are myelinated.
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28. UNIT B
Chapter 12: Nervous System
Section 12.1
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29. UNIT B
Chapter 12: Nervous System
Section 12.1
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