peripheral nervous system

Question 1

describe nervous system

Answer 1

coordinates voluntary and involuntary actions and transmits signals between different parts of the body

includes all neural tissue in body
basic functional units called neurons

supporting cells called neuroglia = seperate and protect neurons, provide supportive framework

Question 2

anatomical divisions of NS I

Answer 2

CNS - brain and spinal cord
responsible for integrating, processing and coordinating sensory data and motor commands
responsible for higher functions such as intelligence, memory, learning and emotion

Question 3

anatomical divisions of PNS

Answer 3

consists of all neural tissue except brain and spinal cord

PNS delivers sensory info to CNS and carries motor demands to peripheral tissues and systems

functionally divided into afferent and efferent divisions

Question 4

afferent vs efferent

Answer 4

afferent - brings sensory info to the CNS from receptors in peripheral tissues and organs

efferent = carries motor commands from CNS to muscles and glands

Question 5

functional divisions of the NS I

Answer 5

somatic = innervates musculoskeletal structures and sense organs of the skin.
efferent functions under voluntary control

autonomic = innervates smooth muscles and glands. maintains at constant level an internal environment of body

Question 6

sympathetic vs parasympathetic NS

Answer 6

have opposing effects

sympathetic division - active during periods of exertion, stress or emergency (fight or flight)

parasympathetic division- under resting conditions (rest and digest)

Question 7

spinal cord

Answer 7

spinal cord continuous with the lowermost part of the brainstem, medulla oblongata

passes down the vertebral canal and terminates as a cone shaped swelling, conus medullaris

terminates at approx level of L1-2

spinal nerves continue to branch out diagonally forming cauda equina

slender strand of fibrous tissue extends from inferior tip of spinal cord to attach to sacrum called filum terminale

Question 8

gross anatomy of spinal cord I

Answer 8

spinal cord and brain consist of 2 types of nervous tissue:

• grey matter = contains cell bodies, dendrites and proximal parts of axons of neurons
• white matter = contains abundance of myelinated axons which run in tracts carrying signals from one part of the CNS to another

Question 9

gross anatomy of spinal cord II

Answer 9

grey matter
butterfly or H shaped in cross section

two posterior horns = receive sensory information

two anterior horns = cell bodies of motor neurons

lateral horn only present in thoracolumbar regions as these contain cell bodies of sympathetic NS

grey mater greatest in cervical and lumbar regions, sensory and motor control of limbs is greatest giving rise to cervical and lumbar enlargements

Question 10

gross anatomy of spinal cord III

Answer 10

white matter :

• surrounds grey matter
• contains axons that course up and down cord
• bundles arranged in 3 pairs called columns
• posterior, lateral and anterior

each column consist of subdivisions called tracts. ascending tracts conduct motor impulses down cord

Question 11

components of PNS

Answer 11

consists of:

cranial nerves = 12 pairs, arise from brain and brainstem

spinal nerves = 31 pairs, arise from spinal cord

Question 12

spinal nerves

Answer 12

31 pairs

first pair between skull and C1
cervical region there are 8 spinal nerves and only 7 cervical vertebrae

rest pass through intervertebral foramen so:
12 thoracic 
5 lumbar 
5 sacral 
1 coccygeal

Question 13

distribution of typical spinal nerve

Answer 13

dorsal ramus = to muscles and skin in region of back

ventral ramus = to anterior and lateral muscles and skin of trunk
gives rise to nerves of limbs

Question 14

dermatomes and myotomes

Answer 14

spinal nerves have motor fibres and sensory fibres

skin area supplied by sensory fibres of a single nerve root is known as a dermatome

group of muscles primarily innervated by motor fibres of a single nerve root is known as myotome

Question 15

nerve plexuses

Answer 15

ventral rami of adjacent spinal nerves merge, to form nerve plexuses

contain sensory as well as motor fibres

5 spinal plexuses:

• cervical plexus
• lumbar plexus
• sacral plexus
• brachial plexus
• coccygeal plexus

Question 16

brachial plexus I

Answer 16

innervates pectoral girdle and upper limb
nerves originate from:
- roots, trunks, cords and branches

Question 17

musculocutaneous nerve

Answer 17

spinal segments C5,6,7

penetrates the coracobrachialis muscle and passes between the biceps brachia and brachialis muscle

innervates all three flexor muscles in anterior compartment of the arm

Question 18

median nerve

Answer 18

spinal segments C5,6,7,8 and T1

passes through arm and into forearm through cubital fossa

innervates most of muscles in anterior compartment of forearm

except: flexor carpi ulnas and medial half of flexor digitorum profundus muscle

continues to hand via carpal tunnel

Question 19

radial nerve

Answer 19

spinal segments C5,6,7,8 ans T1

enters arm by crossing the inferior margin of the term major muscle through triangular interval

in arm passes diagonally from medial to lateral through posterior compartment

passes anteriorly through lateral inter muscular septum and enters anterior compartment of forearm

Question 20

radial nerve II

Answer 20

bifurcates into:

deep - mostly motor
superficial
sensory

continues laterally and posteriorly to enter hand

innervates all muscles in posterior compartment of arm and forearm

sensory innervation to skin on posterior aspect of arm and forearm and dorsal lateral surface of the hand

Question 21

ulnar nerve I

Answer 21

spinal segment C7,8 & T1

passes through arm and posterior to medial epicondyle of humerus and into anterior compartment of forearm

Question 22

ulnar nerve II

Answer 22

passes down medial side of forearm between flexor carpi ulnas and flexor digitorum profundus

innervates these muscles

passes into hand superficial to flexor retinaculm

Question 23

femoral nerve

Answer 23

L2,3,4

leaves abdomen under inguinal ligament to enter the anterior compartment of the thigh

innervates all muscles in anterior compartment

innervates skin over anterior thigh, anteromedial Side of knee, medial side of leg, medial side of foot

Question 24

sciatic nerve I

Answer 24

largest nerve of body

L4 to S3

leaves pelvis through greater sciatic foramen into gluteal region

enters posterior compartment of thigh

divides into two branches
= common fibular and tibial

Question 25

sciatic nerve II

Answer 25

innervates:

all muscles in posterior compartment of thigh

part of adductor Magnus

all muscles of leg

all muscles of foot

skin on lateral side of leg and lateral side and sole of foot

Question 26

spinal meninges

Answer 26

spinal cord. protected by vertebral column

delicate neural tissues must be protected from bony walls of vertebral canal

series of specialised membranes surrounding spinal cord called spinal meninges

dura mater
arachnoid mater
pia mater

at foramen magnum, spinal meninges are continuous with cranial meninges

blood vessels within layers provide nutrients to spinal cord

Question 27

dura mater

Answer 27

tough, fibrous outermost covering

between dura mater and walls of vertebral canal lies the epidural space

contains areolar tissue, blood vessels and adipose tissue

target for anaesthetics in epidural block

does not have extensive attachments along vertebral canal

attached superiorly to occipital bone

inferiorly blends with filum terminal to form coccygeal ligament

Question 28

arachnoid mater

Answer 28

consist of arachnoid membrane and arachnoid trabecular

delicate network of collagen and elastic fibres extend to outer surface of pia mater

Question 29

pia mater

Answer 29

firmly bound to underlying neural tissue

blood vessels servicing the spinal cord run along the surface of the pia mater within subarchanoid space

ligaments extend from pia mater through archanoid to dura mater along length of spinal cord called denticulate ligaments