Nervous tissue

• nervous system overview• NS organization • terminology• anatomy of a neuron• neuroglial cells• myelin sheath• synapse anatomy

An overview of the nervous system

PNS

CNS

Sensory Motor

Visceral Somatic

Sympathetic Parasympathetic

CNS = brain and SCPNS = everything else

Nervous systemdivisions

1

3

2

Peripheral NSCentral NS

Muscles

1 = sensory (afferent) neuron2 = interneuron (CNS)3 = motor (efferent) neuronSomatic Nervous System

1

3

2

Visceral Nervous System

1 = sensory neuron2 = interneuron (CNS)3 = motor neuron

Peripheral NS Central NS

Nucleus

Axons or Dendrites

Cell body

Neuroglial cells

Nervous system = neurons and glia

Typical neuron dendrites

Axon hillock

axon

Myelin sheath

TerminalArborizationswith synaptic knobs

Blue = axon

Multipolar Neurons

bipolar

Unipolar or pseudounipolar

Neuroglia

• CNS– Astrocytes (green)– Microglia (purple) – Oligodendrocytes (blue)– Ependymal (pink)

• PNS– Schwann– Satellite cell

• Neuroglia can undergo mitosis (for better or worse)• gliomas (ependymoma, astrocytoma, oligodendroglioma)

Formation of the myelin sheath - PNS

Schwann cell

neurilemma

Myelinsheath

Fig. 13.7a(TE Art)

Oligodendrocyte

Nerve fiberMyelin

Myelin sheath in the CNS

CNS

PNS

oligodendrocyteSchwann cell

• Schwann cell helps damaged nerve fibers grow back to target• Oligodendrocyte does not• Nerve regeneration in PNS not CNS

axons

S

Multiple sclerosis• myelin sheath in CNS deteriorates • replaced by scar tissue• Symptoms? Signs?

Postsynaptic neuron

Synaptic vesicles

Synaptic cleft

Neurotransmitterreceptor

Presynaptic neuron

Synapses

Neurotransmitters• chemical signals

Synaptic vesiclescontaining ACh (acetylcholine)

Motor endplate

Neurotoxins: botulism, curare, tetanus toxin

Neuromuscular junction

AChE – breaks down ACh

Excitatory NT’sGlutamate – brainAspartate – SC

Inhibitory NT’sGABA – brainGlycine - SC