The Nervous System Name ______

1.  What is primary function of the nervous system?

Master control and communicating system of the body; uses electrical impulses for its signal to cause responses that are almost immediate.

2.  In order to complete its normal role, it has three overlapping functions. List and explain each.

a.  Sensory Input – gathered information from the body monitoring changes inside and outside of the

body called stimuli.

b.  Integration – processing and interpreting sensory input and makes decisions about what needs to be

done at each moment.

c.  Motor Output – effecting a response by activating muscles or glands.

3.  What other body system helps the nervous system along in its quest to maintain homeostasis?

Works closely with the endocrine system because glands are used in motor output.

4.  Scientists organize the nervous system into two primary structural sections. What are they and what do they include?

I.  Central Nervous System – consists of brain and spinal cord in the dorsal cavity.

II.  Peripheral Nervous System – consists of all other parts outside the CNS; mainly the nerves that extend

from the brain and spinal cord.

5.  When considering functional classification, scientists only look at the structures of the: PNS structures, not CNS

6.  What at the two subdivisions of the PNS? Explain each.

a.  Sensory or Afferent Division – nerve fibers that send sensory input from the receptors to the central nervous system. Can be somatic (skin, skeletal, joints) or visceral (visceral organs like heart, liver, stomach, etc.)

b.  Motor or Efferent Division – carries impulses from the CNS to effector organs such as the muscles and glands; called an effect or motor response.

7.  The motor subdivision of the PNS also has two subdivisions. List and explain each.

a.  Somatic Nervous System – allows for conscious or voluntary control of skeletal muscles; sometimes called the Voluntary Nervous System. Not all skeletal muscle actions are controlled by this system.

b.  Autonomic Nervous System – regulates all automatic or involuntary actions of the body such as smooth and cardiac muscle activity or stimulating glands to secrete products. Sometimes called the Involuntary Nervous System. Has two divisions itself: sympathetic and parasympathetic systems.

Supporting Cells

8.  What are neuroglia?

The supporting cells that act as glue (lumped together) and support, insulate, and protect delicate neurons. Each type of glia has a specific function.

  1. What are astrocytes and why are they important?

Most abundant, star shaped glial cells that brace, anchor neurons to their blood capillaries, form a barrier, and play a role in exchanges between blood and neurons. Also protect neurons from bad chemicals, recapture neurotransmitters, and pick up excess ions to maintain chemical environment.

  1. What shape are microglia cells and what do for the human body?

Spiderlike cells that are really phagocytes (engulfers) that dispose of debris such as dead brain cells, bacteria, and other wastes.

c.  Ependymal cells are found where? Lining cavities of brain and spinal cord.

i.  What do these cells do? They use cilia to propel cerebrospinal fluid (CSF) around cavities and form a cushion around the CNS.

  1. What are oligodendrocytes? Why are they important?

Neuroglia that produce the fatty insulating coverings known as the myelin sheaths (only in CNS!).

  1. Neuroglia resemble neurons but can neurgolia transmit nerve impulses? No they cannot
  1. How are neuroglia cells different from neurons?

Cannot transmit impulses and neuroglia never lose their ability to divide (go through mitosis to make new cells).

  1. Most brain tumors are Gliomas
  2. List the two types of supporting cells in the PNS and explain each.

i.  Schwann Cells – cells that form the myelin sheaths in neurons of the PNS.

ii. Satellite Cells – cells that are protective and cushioning in the PNS.

9.  Nerve cells are also called Neurons

  1. These cells have two major regions. List and Explain each.

i.  Cell Body – contains the nucleus, nucleolus, and is the metabolic center of the neuron.

ii. Processes or Fibers – Slender projections that extend from the cell body and can be many different lengths. Examples are axons and dendrites.

b.  Axons – Slender fibers/processes that generate nerve impulses and conduct them away from the cell body.

c.  Dendrites – neuron processes that conduct electrical currents towards the cell body.

Dendr = Tree

d.  Axon terminals – the terminal end of an axon branch where electrical impulse gets conducted towards so neurotransmitters can be released into the synapse.

  1. Contain vesicles that contain Neurotransmitters.
  2. Axon terminals are separated from other neurons by a tiny gap called:

Synaptic Cleft

  1. What is a Synapse – The whole functional junction between axon terminal and the next neuron. Synaptic cleft, axon terminals, processes of other neuron, neurotransmitter are all part of the synapse.
  1. Myelin – Whitish, fatty material that protects and insulates the fibers and increases the transmission of nerve impulses (makes them faster).

Nerve Fiber Coverings:

10.  Schwann Cells - (Be Specific in your answer)

Cells on the outside of the axons outside of the CNS that produce the myelin sheath by wrapping themselves tightly around the axon in a jelly-roll like fashion.

Related to Schwann cells are three other structures of a neuron.

  1. Myelin Sheath – Myelin cover that encloses the axon
  2. Neurilemma – part of outermost Schwann cell cytoplasm that is external to myelin sheath
  3. Nodes of Ranvier – Gaps/indentations in the myelin sheath that are at regular intervals along the axon.

11.  Myelin insulation is very important to nerve transmission. What happens in people who have multiple sclerosis?

The myelin sheaths are gradually destroyed and are converted to hardened sheaths instead called scleroses. The electrical current is then short-circuited and the person loses the ability to control his or her muscles and becomes increasingly disabled over time. MS is an autoimmune disorder where the body attacks the protein used to myelin sheaths. A drug called interferon has helped in recent days.

Classification of Neurons:

Functional classification

12.  List the three functional groups of neurons. Briefly explain each.

a.  Sensory or Afferent Neurons – Neurons that carry impulses towards the CNS and are responsible for keeping our bodies informed of changes inside + outside of the body. Found in ganglion outside CNS.

b.  Motor or Efferent Neurons – neurons that carry impulses from the CNS to the viscera (internal organs), muscles, and/or glands. Cell bodies of Efferent neurons are always in the CNS.

c.  Association neurons – neurons that connect motor and sensory neurons in neural pathways. Their cell bodies are also always in the CNS too.

13.  Inside the sensory neurons are specialized receptors:

  1. In the skin, they are called Cutaneous Receptors
  2. In the muscles and tendons, they are called Proprioceptors
  3. They detect what type of stress? Stretching + tension of skeletal muscles, tendons and joints.

14.  Association neurons are also known as Interneurons

Structural Classification

15.  List and explain each of the three types of structural neurons.

a.  Multipolar neuron – neuron with many processes extending from the cell body. Most common type because all motor and association neurons are this multipolar.

b.  Bipolar neuron - neuron with two processes extending from the cell body; one axon and one dendrite. Rare in adults.

c.  Unipolar neuron with a single process extending from the cell body.

16.  What are the two functional properties of neurons?

a.  Irritability – ability to respond to stimulus and convert it to nerve impulse

b.  Conductivity – ability to transmit the impulse to other neurons, muscles, or glands.

17.  When the plasma membrane is resting or inactive, it is said to be polarized.

a.  This means what?

This means that there are fewer positive ions sitting on the inner side of the neuron’s plasma membrane that on the outer side in the tissue surrounding neuron. (K+ inside cell, Na+ outside)

18.  What is an action potential? What is another name for it?

Electrical current generated by depolarization that is transmitted; all or nothing response.

19.  The faster type of impulse propagation occurs in myelinated fibers and is called Saltatory conduction.

20.  List a few of the factors that can impair the conduction of impulses.

Alcohol, sedatives, and anesthetics reduce permeability of Na+ ions.

Cold and continuous pressure can hinder impulse conduction because blood supply is cut off (no oxygen or nutrients for the neurons)

21.  What are reflexes?

Rapid, predictable, and involuntary responses to stimuli that continue in the same direction.

22.  Reflexes occur over pathways called Reflex Arcs

·  direct route from a sensory neuron, to an interneuron, to an effector

23.  What are autonomic reflexes? Provide examples of these.

Regulate the activity of smooth muscles, the heart, and glands. Secretion of saliva during first stages of digestion (salivary reflex) and the change in size of the pupil (papillary reflex). Think Pavlov’s dog for you psychology students.

  1. What do these help regulate? Digestion, elimination, blood pressure, and sweating.

24.  What are somatic reflexes?

All reflexes that stimulate skeletal muscle such as when you remove your hand quickly from a hot stove.