Lecture 14

Question 1

PNS

Answer 1

31 pairs of spinal nerved, 12 pairs of cranial nerves and ganglia. Ganglia doesn’t directly connect to CNS. Cranial nerves attach to brainstem except for 2 that attach to diencephalon and cerebrum. Senses change in internal and external environment (delivers to CNS) and delivers motor commands from CNS (muscles and glands)

Question 2

Myelinated CNS neurons

Answer 2

oligodendrocytes can myelinate many axons. Lots of mlyelin in white matter, some in grey. White is where travelling axons are congregating therefore, have axonal tracts.

Question 3

Myelinated PNS neurons

Answer 3

Schwaan cell myelinates a single neuron and they line up along the axon. They coil their membrane around axons forming multiple concentric layers and there’s little cytoplasm between. Microanatomy supports function as Nodes of Ranvier have voltage-gates Na channels that are crucial for the propagation of electrical impulse.

Question 4

Neurilemma

Answer 4

Outermost nucleated cytoplasmic layer of S.C

Question 5

Internode

Answer 5

Areas of myelin on axon. What insulates axon membrane

Question 6

Node of Ranvier

Answer 6

Small unmylinated areas on the axon. Contain voltage gates K+ and Na+ channels.

Question 7

Unmyelinated neurons and relationship to schwann cells

Answer 7

Do not have concentric wrapping, but are still associated with them as they provide metabolic cells (same with oligodendrocytes in CNS)

Question 8

Peripheral nerves

Answer 8

Each peripheral nerve has multiple axons in it and they bundle together to form fasicles.

Question 9

Endoneurium

Answer 9

Myelin and CT surrounding peripheral nerve axon

Question 10

Perineurium

Answer 10

Cellular layer that has tight junctions creating barrier between axons and extra fascicular cells.

Question 11

Epineurium

Answer 11

CT that glues multiple fascicles together. may also have adipose tissue and vasculature.

Question 12

Somatic motor neurons integration

Answer 12

somatic mn come out of ventral horn of spinal cord. But, there are somatic mn in brainstem that leave through cranial nerves and send axons to skeletal muscle where axon terminals synapse at NMJ

Question 13

Spinal nerves

Answer 13

Nerves that interact directly with sc. Dorsal rootlets contain sensory axons of dorsal root ganglion neurons of primary somatosensory neurons. Ventral roots contain mn axons. Ventral and dorsal roots come together to form spinal nerves. They then split and branch to make PNS structures.

Question 14

Organisation of cranial nerves

Answer 14

Interact directly with brain. Most attach to brainstem and these are involved in sensory/motor innervation of head and neck. Vagus nerve originates from brainstem and innervates viscera therefore exception to most. Unlike spinal nerves, also carry special sensory info (spinal only visceral, somatosensroy and sumpathetic and somatic motor) i.e taste, smell, vision, hearing and balance). 2 cranial nerves interact with cerebrum and diencephalon directly (come from olfactory mucose and occipital lobe).