Lab 12 Histology Questions (UNIT 4)

What are nerves?

collections of axons surrounded by CT; only in the PNS

What is the tissue subtype of the endoneurium?

loose areolar CT

What does the endoneurium surround?

individual axons

What is the tissue subtype of the perineurium?

specialized dense CT

What does the perineurium surround?

fascicles (bundles of axons)

What is the tissue subtype of the epineurium?

dense irregular CT

What does the epineurium surround?

All the fascicles (forms the nerve)

What is a node of Ranvier?

non-myelinated constrictions along the length of an axon

What is the role of the myelin sheath?

Acts as an electrical insulator and speeds conduction of nerve impulses

What types of ion channels are located in the nodes of Ranvier?

voltage-gated Na+

What types of ion channels are located in dendrites?

chemically-gated Na+

What types of ion channels are located in the cell body?

chemically-gated Na+

What types of ion channels are located in the axon hillock?

voltage gated Na+

What types of ion channels are located in the axon?

voltage-gated Na+

What types of ion channels are located in the axon terminal?

voltage-gated Ca2+ and Na+

What is the structural classification of pyramidal neurons?

multipolar

What is the functional classification of pyramidal neurons?

motor

What is the structural classification of Purkinje nuerons?

multipolar

What is the functional classification of Purkinje neurons?

motor

Which horn contains more motor neurons?

ventral horn

What are the two divisions of the nervous system?

central nervous system and peripheral nervous system (CNS, PNS)

What makes up the CNS?

brain and spinal cord

What makes up the PNS?

cranial and spinal nerves, ganglia, enteric plexus (small intestine), and sensory receptors (in skin)

What are Schwann cells?

any cell that forms myelin sheath around axons in PNS

What is myelin?

a mixture of proteins and phospholipids forming a whitish insulating sheath around axons, increasing the speed at which nerve impulses are conducted

What does the nodes of Ranvier do?

speeds up process of transmitting nerve impulses between CNS adn sensory receptors or effector muscles

How do nodes of Ranvier increase the speed of nerve impulses?

because the myelin sheath is absent at nodes, nerve impulses jump from node to node (Saltatory conduction)

Where do nerves typically keep their cell body and axons?

Cell bodies are kept in the CNS and axons extend out into the PNS

What is a ganglion?

A cluster of neuron cell bodies in the PNS

What is gray matter?

unmyelinated axons and many neuron cell bodies

What is white matter?

myelinated axons