Lecture 1: Nervous System 1

Question 1

What are simple pattern reflexes?

Answer 1

automated, unlearned, and predictable reflexes which involve spinal cord circuits only (do NOT require cortical input)

Question 2

What are complex postural (reflex movements) adjustments?

Answer 2

are not predictable reflexes, instead they are flexible and goal-oriented reflexes -> mostly coordinate their action with voluntary movements, hence require cortical input (spinal cord and supraspinal centres)

Question 3

What do voluntary movements involve?

Answer 3

involve spinal cord, brainstem and motor cortex (more CNS areas involved)

Question 4

What is the hierarchy of motor neurons?

Answer 4

upper motor neurons -> lower motor neurons

motor cortex / brainstem -> spinal cord -> skeletal muscles

Question 5

What are some examples of upper motor neurons?

Answer 5

cortical motoneurons of the motor cortex (pyramidal tract)

motor neurons of brainstem nuclei (red nucleus, tectum, reticular formation, and vestibular nuclei)

Question 6

What are some examples of lower motor neurons?

Answer 6

alpha and gamma motor neurons of the spinal anterior horn

motor neurons of cranial nerves in the brainstem

Question 7

Where do upper motor neurons always remain?

Answer 7

within the CNS, their axons do not depart to the PNS

Question 8

Where are cell bodies and axons of lower motor neurons located?

Answer 8

cell bodies are located in the CNS but their axons project out into the PNS to target the skeletal muscles that they innervate

Question 9

What is a motor unit?

Answer 9

a group of muscle fibers which is innervated by a motor neuron

Question 10

What is the size of motor units in muscles used for precise contraction?

Answer 10

small

Question 11

What is the size of motor units in power-generating muscles, which do not necessarily need precise contraction?

Answer 11

large

Question 12

What is the neuromuscular junction?

Answer 12

a synapse or junction between an axon terminal of a motor neuron and muscle fibers

Question 13

What are nerves?

Answer 13

collections of thousands of individual axons within a common external connective tissue sheath (epineurium) -> in the periphery

Question 14

What are the fascicles into which nerve axons are sub-grouped?

Answer 14

the epineurium, perineurium and endoneurium -> all surrounded by a perineurial sheath

Question 15

How many nerves are there for each part of the spine?

Answer 15

cervical: 8 pairs
thoracic: 12 pairs
lumbar: 5 pairs
sacral: 5 pairs
coccygeal: 1 pair

Question 16

What are the two different types of peripheral nerve axons?

Answer 16

efferent nerve axons which carry motor signals from the CNS and afferent nerve axons which carry sensory signals to the CNS

Question 17

Where are efferent and afferent axons segregated? How do sensory and motor axons join the CNS?

Answer 17

at the point just before they contact the CNS (spinal cord or brainstem)
sensory axons join the CNS via a dorsal root and motor axons join the CNS at a ventral root

Question 18

What is a dermatome?

Answer 18

an area of skin that is mainly supplied by a single spinal nerve

Question 19

What is a myotome?

Answer 19

the group of muscles that a single spinal nerve innervates

Question 20

What can a peripheral nerve be often comprised of?

Answer 20

multiple spinal nerves, i.e. several spinal segments contribute axons to a single peripheral nerve (nerve plexus)

Question 21

What are some examples of nerve plexuses?

Answer 21

cervical plexus (head, neck, diaphragm)
brachial plexus (upper limbs)
lumbosacral plexus which is made up of the lumbar and sacral plexus (lower limbs)

Question 22

Which nerves are found in the brachial plexus?

Answer 22

musculocutaneous (lateral)
median (lateral/medial)
ulnar (medial)
radial and axillary (posterior)

Question 23

What is the autonomic nervous system?

Answer 23

an effector system in the CNS and PNS mediating unconscious homeostatic control of organ and body physiology

Question 24

What are the two main divisions of the autonomic nervous system? Specify the type of outflow of each of these divisions.

Answer 24

sympathetic (thoracolumbar outflow) and parasympathetic (craniosacral outflow)

Question 25

Which cranial nerves are parasympathetic?

Answer 25

oculomotor nerve: narrows pupils and focuses lens
facial nerve: tear, nasal and salivary glands
glossopharyngeal nerve: parotid salivary gland
vagus nerve: viscera as far as proximal half of colon
cardiac, pulmonary, and esophageal plexus

Question 26

What is the purpose of ventral (anterior) and dorsal (posterior) rami?

Answer 26

allows for innervation of tissues on the front of our body and the back of our body

Question 27

What are rami?

Answer 27

branches of spinal nerves

Question 28

What is the equivalent of upper and lower motor neurons in the autonomic nervous system as opposed to the somatic nervous system?

Answer 28

preganglionic and postganglionic neurons

Question 29

Are parasympathetic postganglionic neurons closer to the spinal cord or the periphery?

Answer 29

closer to the periphery

Question 30

Are sympathetic postganglionic neurons closer to the spinal cord or the periphery?

Answer 30

closer to the spinal cord