1. The Nervous System The Spinal Cord & Spinal Nerves
Chapter 9

2. Parts of the nervous system are grouped according to structure or function
Structural Divisions
Central Nervous System (CNS):
Brain
Spinal Cord

3. Peripheral Nervous System (PNS):
Cranial Nerves – carry impulses to and from the BRAIN
Spinal Nerves – carry messages to and from the SPINAL CORD
**Together, the CNS & PNS include all of the nervous tissue in the body

4. Functional Divisions
Functionally, the nervous system is divided according to whether control is voluntary or involuntary
A tissue or organ that carries out a command from the nervous system is called an EFFECTOR
Effectors are our muscles and glands

5. The Somatic Nervous System
Controlled voluntarily (by conscious will) and all the effectors are skeletal muscles

6. The Autonomic Nervous System
Is an involuntary system and controls:
Smooth muscle
Cardiac Muscle
Glands

7. Neuroglia
Cells of the nervous system that serve to support & protect. Types with specialized functions include:
Protection of nervous tissue
Supporting nervous tissue & binding to other structures
Aiding in the repair of cells
Acting as phagocytes to remove pathogens
Regulating fluids in between & around cells
**Neuroglia continue to multiply throughout life (unlike typical nerve cells)
**Disadvantage is the potential of tumor growth

8. Neurons Functional cells of the nervous system
Highly specialized cells
Main portion (cell body) contains typical nucleus & other organelles
Distinguishing feature NOT found in any other cells:
Long, threadlike fibers that extend out from the cell body & carry impulses across the cell called AXONS & DENDRITES

9. Types of Neurons
Sensory Neurons – conduct impulses TO the spinal cord and brain
Motor Neurons – carry impulses from the Central Nervous System to the muscles and glands

10. The Synapse Neurons do not work alone
Impulses must be transferred between neurons to convey information
The synapse becomes the “point of junction” or “gap” where impulses are transferred

11. Neurotransmitters Chemicals contained in the end of the axon
They are released into the synapse to stimulate the next cell

12. The Reflex Arc A complete pathway through the nervous system
Basic parts include:
Receptor – detects a stimulus
Sensory neuron – transmits the impulse TO the CNS
CNS – impulses are coordinated & a response is organized
Motor neuron – carries the impulse AWAY from the CNS
Effector – a muscle or gland that carries out a response
**The Patellar Reflex or “Knee-Jerk” Reflex

13. The Myelin Sheath
An insulating layer that forms around nerves

14. Disorders Involving the Spinal Cord
Multiple Sclerosis (MS) –
Myelin sheath is damaged
Fibers degenerate
Although not fully understood, strong evidence indicates a person’s own immune system attacks the myelin sheath:
Prior viral or bacterial infection
Genetic make-up
Environmental factors
Different rate of progression
Episodes of relapse or remission

15. Tumors Commonly found in tissue in or around the spinal cord
Symptoms caused by pressure on the cord and spinal nerves
Symptoms include: pain, numbness, weakness and loss of function
Diagnosed through the use of MRI
Treated by surgery and/or radiation (for malignant tumors)

16. Amyotrophic Lateral Sclerosis (ALS)
Also known as “Lou Gherig’s Disease”
Motor neurons are destroyed
Progressive destruction that causes muscle atrophy and loss of motor control
Eventually, the person is unable to swallow, talk or breathe
Death follows soon after

17. Poliomyelitis (Polio)
Viral disease of the nervous system
Occurs commonly in children
Gastrointestinal tract infection passes the virus into the bloodstream – eventually spreading to the CNS
Virus multiplies in motor neurons within the spinal cord
Leads to paralysis and death, if left untreated
Vaccines have eliminated the disease in many countries – Jonas Salk (1954)

18. Spinal Cord Injuries
Occur when vertebrae are broken or dislocated (car accidents, diving accidents, etc.)
Because brain & spinal tissue cannot repair itself, severing of the spinal cord causes paralysis of all muscles supplied by nerves BELOW the level of the injury

20. Paraplegia
Loss of sensation and movement in the lower portion of the body

21. Quadriplegia
Loss of sensation and movement from the neck down