Peripheral Nervous System

Question 1

Composition of PNS

Answer 1

Cranial and Spinal nerves and ganglia outside brain and spinal chord
Sensory Afferent
Motor Efferent division: Somatic NS + Autonomic NS (sympathetic and parasympathetic division)

Question 2

Where do sensory and motor nerves carry info with regards to CNS?

Answer 2

Sensory nerves carry info towards the CNS

Motor nerves carry info away from the CNS

Question 3

Number of nerves in brain and spine

Answer 3

12 pairs of cranial nerves

31 pairs of spinal nerves

Question 4

Where do somatic afferent nerves convey info from?

Answer 4

Skin
Skeletal muscles
Joints

Question 5

Where do somatic efferent nerves convey information to?

Answer 5

Skeletal muscles

Question 6

Dermatome

Answer 6

Area or skin that is supplied by a single spinal nerve

Question 7

Myotome

Answer 7

Group of muscles innervated by a single spinal nerve

Question 8

Describe the types Visceral nerves

Answer 8

Visceral afferent nerves:
Carry info from the viscera (thoracic/ abdominal/ pelvic organs)
Visceral efferent nerves:
Divided into sympathetic and parasympathetic efferent nerves
Sympathetic - innervate the viscera (organs) and periphery (vasculature+sweat glands)
Parasympathetic - innervate the viscera (organs) only

Question 9

Ganglion vs Nucleus vs Plexus

Answer 9

Ganglion: collection of cell bodies outside CNS
Nucleus: collection of cell bodies inside CNS
Plexus: network of interconnecting nerves

Question 10

Where are the cell bodies of afferent fibres located?

Answer 10

Spinal ganglia

Question 11

Where do visceral efferent nerves synapse?

Answer 11

In a peripheral ganglion

Question 12

Describe the structure of peripheral nerves

Answer 12

Arranged in fasciculi
Three layers of connective tissue present:
External vascular layer - epineurium
Individual fascicles covered in perineurium
Individual axons covered in endoneurium

Question 13

Classification of peripheral nerves

Answer 13

Two classification systems:

1. Based on Conduction velocity (uses ABC) - A is the fastest
2. Based on Axonal diameter sensory only (uses I-IV) - I is largest diameter

Question 14

Sensory receptors

Answer 14

Detect external/internal info 
Can be classified by source of stimulus or by mode of detection
External: exteroceptors
Internal: proprioceptors/enteroceptors
Chemo/Photo/Thermo/Mechanoreceptors

Question 15

Nociceptors

Answer 15

Detect tissue damage, interpreted as pain

Question 16

Proprioceptors

Answer 16

Found in joints, muscles + golgi tendon organs
Muscle spindle - detect change in muscle length
Golgi tendon organs - detect changes in tension in tendons
Join receptors - found in joint capsule and detect start and end of movement

Question 17

Neuromuscular junction

Answer 17

Specialised synapse between a motor neurone and a muscle fibre

Question 18

Motor unit

Answer 18

Single motor neurone together with all the muscle fibres that it innervates
Smallest functional until with which to produce force
Stimulation of one motor until causes contraction of all the muscle fibres in that unit

Question 19

Reflex action

Answer 19

Involuntary coordinated pattern of muscle contraction and relaxation elicited by peripheral stimuli
Eg: (hammer on knee)
Stretching stimulates sensory receptor (muscles spindle)
Sensory neurone activated
Sensory neurone activates motor neurone within Integrating Centre (spinal chord)
Motor neurone activated
Effector contracts and relieves stretching

Question 20

ANS

Where are sympathetic and parasympathetic neurones situated on spinal chord

Answer 20

Parasympathetic - from brain stem, cranial nerves III VII IX X down to S2-S4 spinal segments
Sympathetic - T1 to L2 spinal segments

Question 21

ANS

Visceral Sensory Neurones

Answer 21

Relay sensory info from the core
Detect pain, fullness, BP
situated T1-L2, S2-S4 and cranial nerves IX and X

Question 22

ANS

Visceral Motor Neurones

Answer 22

Outflow to core and body wall
Controls pupils, sweat glands, salivary glands, heart muscle, airways
T1-L2 (thoracolumbar) and cranial nerves III VII IX X (craniosacral outflow)