Peripheral Nervous System

Question 1

How can the peripheral nervous system be divided?

Answer 1

Sensory (afferent) and motor (efferent)

The motor can be divided Into autonomic and somatic

The autonomic can be divided into sympathetic and parasympathetic

Question 2

How many cranial nerves are there?

Answer 2

12

Question 3

How many spinal nerves are there?

Answer 3

31

C (8)

T(12)

L(5)

S(5)

Co(1)

Question 4

Where do somatic nerves convey information from?

Answer 4

Afferent: from skin, skeletal muscle and joints

Efferent: to skeletal muscles

Question 5

What are dermatomes and myotomes?

Answer 5

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

Myotome: a group of muscles innervated by a single spinal nerve

Question 6

What are visceral nerves?

Answer 6

Carry info from the thoracic, abdominal and pelvic organs

Autonomic

Question 7

What can visceral efferent nerves be divided into?

Answer 7

Sympathetic and parasympathetic

Fight or light and rest and digest

Question 8

What is a ganglion

Answer 8

A collection of cell bodies outside the CNS

Question 9

What is a nucleus?

Answer 9

A collection of cell bodies inside the CNS

Question 10

What is a plexus?

Answer 10

A network of interconnecting nerves

Question 11

Where do all afferent fibres have their cell bodies?

Answer 11

Spinal ganglia

Question 12

Where do all efferent nerves synapse?

Answer 12

In a peripheral ganglion

Question 13

How are peripheral nerves arranged?

Answer 13

In fasiculi (bundle)

Surrounded by three layers of connective tissue (endoneuroum, perineurium, epineurium)

Question 14

How are peripheral nerves classified?

Answer 14

Two systems

Conduction velocity: classed into A,B,C (A being the fastest)

Axonal diameter: sensory only. Uses Roman numerals I-IV (I being the largest diameter)

Myelinated with a large diameter have the fastest conducting velocities

Question 15

What are the types of sensory receptors?

Answer 15

Detect external or internal info

External: exteroceptors (pain, temperature, touch, pressure)

Internal: proprioceptors (movement,joint position) enteroceptors (movement through gut, blood pH)

Or can be classified by mode of detection (chemoreceptors, photoreceptors, thermoreceptors, mechanoreceptors, nociceptors)

Question 16

What are the types of proprioceptors?

Answer 16

Muscle spindles: detect changes in muscle length

Golgi tendon organs: detect changes In tension in tendons

Joint receptors: found in joint capsules, detect start and end of movement

Question 17

What are the synapses of motor neurones?

Answer 17

Between a motor neurone and a muscle fibre : neuromuscular junction

Question 18

What is a motor unit?

Answer 18

A single motor neurone along with al lure muscle fibres that it innervates. It is the smallest functional unit with which to produce force

Humans have approx 420000 motor neurones and 250 mil skeletal muscle fibres

So on average each motor neurone supplies 600 muscle fibres

Stimulation of one motor unit causes contraction of all the muscle fibres in that unit

Question 19

What is a reflex?

Answer 19

An involuntary coordinated pattern of muscle contraction and relaxation elicited by peripheral stimuli

Bypasses the conscious brain

Question 20

What are the neurotransmitters used in the autonomic nervous system?

Answer 20

Acetylcholine in pre ganglionic

Noradrenaline (S) and acetylcholine (P) in post ganglionic

Question 21

Where do sympathetic and parasympathetic nerves emerge from the spinal cord?

Answer 21

Sympathetic: thoracolumbar section (T1-L2)

Para: craniosacral outflow (cranial nerves III, VII, IX,X) and (S2-S4)