Nervous system

1. What is the function of the nervous system:

Organs of the nervous system

2 principal divisions

1.

2.

Cells of nervous system

  1. neurons
  1. neuroglia –

Neurons – consist of 3 parts, list and describe

1.

2.

3.

3 types of neurons – classified according to the direction in which they transmit impulses:

  1. sensory neurons
  1. motor neurons

3. interneurons –

Draw a Neuron: Label the structures below

Function:

  • Myelin
  • Schwann cells
  • Nodes of Ranvier
  • Neurilemma –

Neuroglia – GLIA

  • Function:
  • glioma-
  • 3 types of Glia:
  1. Astrocytes
  1. Microglia –

3. Oligodendroglia –

Disorders of nervous tissue –

  • Multiple sclerosis –
  • Tumors –
  • Multiple neurofibromatosis –

Nerve – a group of peripheral nerve fibers (axons) bundled together like the strands of a cable.

  • Called white matter of PNS because usually have myelin covering
  • In CNS, bundle of axons are called tracts, may also be myelinated
  • Gray matter – bundle of cell bodies and unmyelinated axons and dendrites

Figure 8-5

  • Endoneurium – thin wrapping of fibrous connective tissue that wraps around axons
  • Fascicles – groups of wrapped axons
  • Perineurium – thin fibrous covering of the fascicles
  • Epineurium – tough, fibrous sheath that covers the whole nerve

**Nerve impulses are very fast and travel all over the body via neuron routes aka neuron pathways.

Reflex arc – specialized neuron pathway, important to the nervous system functioning.

  • Like 1 way streets – allow impulse conduction in only 1 direction
  • Two neuron arc –(simplest type)consists of only 2 types of neurons: sensory and motor
  • 3 neuron arc- consists of all three kinds of neurons, sensory, motor and interneuron.

Impulse conduction usually starts in receptors

Receptors are the beginnings of dendrites of sensory neurons, usually located away from spinal cord in tendons, skin or mucous membranes.

Knee jerk - 2 reflex arc

  1. hammer hits patellar tendon
  2. nerve impulse travels length of sensory neurons dendrite to cell body, located in the posterior (dorsal) root ganglion, near another dendrite in gray matter.
  3. Ganglion is a group of nerve-cell bodies located in the PNS
  4. nerve impulse stops at synapse (space between neurons)
  5. chemical signals are sent across the gap
  6. impulse then continues along the dendrites, cell body and axon of the motor neuron
  7. motor neuron forms a synapse with an effector (muscles or glands) and that organ puts the nerve signal into effect (quadriceps moves)
  8. the response to impulse conduction over a reflex is called a reflex

3 neuron arc consists of interneuron – between sensory and motor, usually called withdrawal reflex, has two synapse as opposed to 1

motor neuron’s dendrite and cell body is in gray matter, axon in muscle.

Nerve impulses – a self propagating wave of electrical disturbance that travels along the surface of a neuron’s plasma membrane.

  • Must be initiated by a stimulus (pressure, temperature and chemical changes)
  • Slight + charge outside and – inside due to Na+ excess on outside
  • When section stimulated, Na+ rushed in creating + inside, - outside.
  • If the traveling impulse reaches a section of membrane covered in myelin, it jumps around the myelin – salutatory conduction – very fast

Synapse –a place where impulses are transmitted form one neuron (presynaptic neuron) to another neuron (postsynaptic neuron)

3 structures make up synapse

1. synaptic knob – tiny bulge at end of a terminal branch of a presynaptic neuron’s axon

1