The Nervous System

Question 1

Cell Body (Soma):

Answer 1

-where soma are concentrated, they form ganglia

1. Nucleus and nucleolus
2. Chromatophilic substance (clusters of ribosomes)
3. neurofibrils: microtubules extending into axon
4. mitochondria

Question 2

dendrites:

Answer 2

short, highly branched extensions of the cell body that carry impulses toward the cell body

Question 3

Axon:

Answer 3

long, slender extension of cell body that carry impulses away from cell body, which are insulated by neuroglia

Question 4

terminal filaments:

Answer 4

1. when joined to a dendrite of another neuron=synapse

2. when joined at a muscle cell=neuromuscular junction

Question 5

Neuroglia:

Answer 5

1. Schwann cells:
   - wrapped around peripheral neurons
   - provide support and axon insulation(myelination)
   - improve speed of nerve impulse conduction
2. Nodes of Ranvier:
   - gaps between schwann cells serve as relay points for nerve impulses
3. Oligodendrocytes:
   - wrapped around central neurons that provide myelination similar to schwann cells
4. Astrocytes:
   - crowded among central neurons that support and link neurons to blood capillaries regulate diffusion; contribute to blood-brain barrier

Question 6

Neuron functional types:

Answer 6

1. Sensory (afferent): impulses travel toward brain from sensory receptors in skin and organs
2. Motor (efferent): impulses travel away from brain into effectors such as muscles or glands
3. Association (interneurons): transmit impulses between neurons in CNS; help in analysis of sensory input and coordination of motor output

Question 7

Neuron structural types:

Answer 7

1. Multipolar: multiple (short) dendrites, one (long) axon usually motor in function.
2. Unipolar: one process splits near cell body usually sensory in function.

Question 8

Nerve bundles:

Answer 8

• groups of mixed nerves located peripherally (outside the CNS)
  1. Epineurium: outermost, dense irregular connective tissue provides strength and allows for some stretch.
  2. Perineurium: dense irregular connective tissue sheath surrounds neurons of similar origin or destination; forms and encloses axons into fasciculi.
  3. Endoneurium: loose connective tissue between single nerve fibers
• adipose: outside fasciculi within epineurium.
• veins and arteries: outside and throughout fasciculi.

Question 9

Synapses:

Answer 9

-junctions that facilitate or inhibit the transmission of electrical signals between neurons.

1. Presynaptic neuron: reacts to arriving impulses.
2. Synaptic vesicle: contain/release neurotransmitters
3. Synaptic cleft: narrow gap between nerve cells
4. Postsynaptic neuron: reacts (+/-) to neurotransmitters

presynaptic impulses-> rupture of synaptic vesicle-> release of neurotransmitter-> new, postsynaptic impulse

Question 10

Organization of the Nervous System:

Answer 10

1. Central Nervous System (CNS):
   - nerve tissue within cranial and spinal cavities
   - Brain
   - Spinal Cord
2. Peripheral Nervous System:
   - nerve bundles leading to/from the brain and spinal cord
3. afferent= sensory division
4. efferent= motor division
   a. somatic N.S.: serves skeletal muscles
   b. autonomic N.S.: serves heart and smooth muscles