principles of nervous system 2

Question 1

How are spinal nerves organised?

Answer 1

segmentally

Question 2

What is meant by spinal nerves being segmentally organised?

Answer 2

• one pair of spinal nerves at each vertebrae

Question 3

What are the names of the different areas of spinal nerves? How many are there for each?

Answer 3

• 8 cervical
• 12 thoracic
• 5 lumbar
• 5 sacral
• 1 coccygeal

Question 4

Describe how the nerves are organised at the cervical area?

Answer 4

• only 7 cervical vertebrae
• C1-7 exit above vertebrae
• C8+ exit below

Question 5

How do spinal nerves connect to the spinal cord?

Answer 5

via nerve roots

Question 6

Where do nerve roots sit?

Answer 6

within the vertebral canal

Question 7

What are the two roots that connect to the spinal cord?

Answer 7

• ventral root
• dorsal root

Question 8

What type of axons come in through the ventral root?

Answer 8

• efferent
• motor and sympathetic

Question 9

What type of axons come in through the dorsal root?

Answer 9

• afferent
• somatosensory

Question 10

What does it mean that spinal nerves are mixed nerves?

Answer 10

they contain motor, somatosensory and sympathetic axons

Question 11

Where do spinal nerves exit through?

Answer 11

intervertebral foramen

Question 12

What can be said about the length of a spinal nerve?

Answer 12

they are very short

Question 13

What can spinal nerves be divided into?

Answer 13

• dorsal/posterior primary ramus
• ventral/anterior primary ramus

Question 14

What do dorsal primary rami supply?

Answer 14

• skin over paravertebral gutter
• erector spinae muscles
• facet joints of vertebral column

Question 15

What do ventral primary rami supply?

Answer 15

the rest of the body except parts of head/neck

Question 16

How do the sizes of nerves between the ventral and dorsal primary rami compare?

Answer 16

ventral primary rami nerves are much bigger

Question 17

What do ventral primary rami form?

Answer 17

• intercostal nerves
• 4 nerve plexuses

Question 18

What is a nerve plexus?

Answer 18

where ventral primary rami merge to form nerves that contain axons from multiple spinal nerves

Question 19

What are the nerve plexuses important for?

Answer 19

the innervation to limbs (large muscles)

Question 20

What are dermatomes?

Answer 20

individual strip of skin innervated by a single spinal nerve (primary ramus)

Question 21

What is a myotome?

Answer 21

individual muscle group innervated by a single spinal nerve (primary ramus)

Question 22

What do dermatomes and myotomes develop from?

Answer 22

• somites

Question 23

What are somites?

Answer 23

paired blocks of paraxial mesoderm that form in horizontal bands

Question 24

What is the relationship between somites and spinal nerves?

Answer 24

one pair of spinal nerves grows into one pair of somites

Question 25

What are the T1-T11 dermatomes supplied by?

Answer 25

the intercostal nerves (which come from ventral primary rami)

Question 26

What is the significance of the T10 dermatome?

Answer 26

it is where the umbilicus is

Question 27

What does a changed sensation from a dermatome indicate?

Answer 27

injury to the spinal cord, nerve root or spinal nerve

Question 28

How can dermatomes help with viscera pain?

Answer 28

viscera pain can be referred to skin dermatomes as cutaneous pain

Question 29

What are the intercostal muscles supplied by?

Answer 29

the intercostal nerves (T-T11)

Question 30

What is the autonomic nervous system?

Answer 30

the involuntary part of the peripheral nervous system

Question 31

What does the autonomic nervous system do?

Answer 31

- regulates operation of the internal organs - maintains internal environment - innervates smooth muscle, cardiac muscle, glands

Question 32

What are the two main divisions of the autonomic nervous system?

Answer 32

- sympathetic - parasympathetic

Question 33

What does the sympathetic system do?

Answer 33

- fight or flight response - maximises use of metabolic resources

Question 34

What does the parasympathetic system do?

Answer 34

- opposiite to sympathetic - switched on during resting - conserves metabolic resources

Question 35

What is the origin of the parasympathetic system?

Answer 35

- brainstem - sacral spinal cord

Question 36

What is the origin of the sympathetic system?

Answer 36

thoracic spinal cord

Question 37

What is autonomic ganglia?

Answer 37

where preganglionic neurons synapse with postganglionic neurons

Question 38

Are preganglionic and postganglionic neurons myelinated or not?

Answer 38

- preganglionic are myelinated - postganglionic are unmyelinated

Question 39

Describe the anatomy of the autonomic nervous sytem?

Answer 39

- usually two neurons in a circuit 1. preganglionic neuron 2. autonomic ganglia 3. postganglionic 4. effector organ

Question 40

What is the exception to the usual 2 neurons in a circuit structure of the autonomic nervous system?

Answer 40

- sympathetic supply to the adrenal gland - its preganglionic axons only

Question 41

What are some things the sympathetic division controls?

Answer 41

- cardiac muscle - bronchi of lungs - sweat glands - hair follicles - blood vessels - abdomino-pelvic viscera - eye

Question 42

Where are the cell bodies of the preganglionic neurons found in sympathetic division?

Answer 42

the thoracic and lumbar spinal cord (T1-L2)

Question 43

Where do the preganglionic axons exit (sympathetic)?

Answer 43

via ventral roots to enter spinal nerves

Question 44

What is the sympathetic trunk?

Answer 44

- interconnected paravertebral ganglia - extends length of vertebral column

Question 45

Where do the preganglionic axons go after entering the spinal nerves (sympathetic)?

Answer 45

- enter sympathetic trunk - synpase with postganglionic neurons

Question 46

What is the ratio of preganglionic neurons to postganglionic neurons?

Answer 46

1:20

Question 47

Where can the postganglionic axons go from the sympathetic trunk?

Answer 47

- primary rami (to musculoskeletal system) - branches (to heart, lungs or head)

Question 48

What do some preganglionic axons do rather than end at he sympathetic trunk?

Answer 48

- pass through sympathetic trunk - enter splanchnic nerves to prevertebral ganglia in abdomen - here postganglionic axons innervate abdominal/pelvic organs

Question 49

In the cranial parasympathetic, where are the cell bodies of the preganglionic neurons found?

Answer 49

brainstem

Question 50

Where do cranial preganglionic axons go after leaving the brainstem? (to innervate head)

Answer 50

1. pass through cranial nerves to ganglia in head 2. postganglionic neurons innervate structures in head

Question 51

Where do cranial preganglionic axons go after leaving the brainstem? (to innervate thorax/abdomen)

Answer 51

1. preganglionic axons pass through vagus nerve to thorax and abdomen 2. postganglionic axons innervate viscera

Question 52

In the sacral parasympathetic, where are the cell bodies of the preganglionic neurons found?

Answer 52

- sacral spinal cord

Question 53

Where do sacral preganglionic axons go after leaving the sacral spinal cord?

Answer 53

1. pass through pelvic splanchnic nerves 2. post ganglionic axons innervate pelvic viscera

Question 54

What are the pelvic organs?

Answer 54

- bladder - rectum - sexual function