Peripherla Nervius Systme

Question 1

PNS divides into

Answer 1

Somatic and autonomic
Sensory(afferent) carries info towards CNS
motor (efferent) carry info away from CNS

Question 2

How many pairs of cranial and spinal nerves are there

Answer 2

12 cranial
31 spinal

Question 3

What do somatic afferent and efferent nerves convey info from and to?

Answer 3

• Somatic afferent nerves convey info from skin, skeletal muscle and joints
• Somatic efferent nerves convey info to skeletal muscles

Question 4

Dermatomes

Answer 4

An area of skin supplied by single spinal nerve

Question 5

Myotome

Answer 5

A group of muscles innervated by a single spinal nerve

Question 6

• What do visceral (autonomic) nerves convey info from and to?

Answer 6

• Visceral afferent nerves carry info from viscera (thoracic, abdominal and pelvic organs)
• Visceral efferent nerves can be divided into sympathetic and parasympathetic

Question 7

What do sympathetic efferent nerves innervate

Answer 7

The viscera and periphery

Question 8

What do parasympathetic efferent nerves innervate

Answer 8

Viscera only

Question 9

Where do all afferent (somatic and visceral) fibres have their cell bodies?

Answer 9

Spinal ganglia (same as dorsal root ganglion)

Question 10

Where do visceral efferent nerves synapse

Answer 10

Peripheral ganglion

Question 11

Ganglion

Answer 11

Collection of neuronal cell bodies outside of the CNS

Question 12

Nucleus

Answer 12

Collection of cell bodies inside the CNS

Question 13

Plexus

Answer 13

Network of interconnecting nerves

Question 14

How are peripheral nerves arranged at spinal vertebrae

Answer 14

3 layers
1) individual axons have the endoneurium around them
2)the axons bundle together to form a fascicle which is covered in perineurium
3)fascicles bundle together to form the spinal nerve with the epineurium around it

Question 15

How can peripheral nerves be classified

Answer 15

• One based on conduction velocity → uses letters A, B and C (A the fastest)
• One based on axonal diameter (sensory nerves only) → uses Roman numerals I-IV (I the largest diameter)

Question 16

What two properties do faster conducting peripheral nerves have

Answer 16

Myelination
Larger diameter

Question 17

How can sensory receptors be classified

Answer 17

Exteroreceptors respond to external stimuli like pain temp touch and pressure

Propioreceptors and enteroreceptors respond to internal stimuli

Question 18

Chemoreceptors

Answer 18

Detect molecules which bind to receptor in olfactory

Question 19

Photoreceptors

Answer 19

Detect light in retina

Question 20

Thermoreceptors

Answer 20

Temp in skin

Question 21

Mechanoreceptors

Answer 21

Mechanical opening of ion channels eg touch receptors in skin

Question 22

Nociceptors

Answer 22

Tissue damage interpreted as pain

Question 23

Where are proprioreceptors located

Answer 23

Muscle spindles are small sensory organs that detect whether muscle has been stretched

Golgi tendon organs detect changes in tension in tendons

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

Question 24

Neuromuscular joints

Answer 24

Specialized synapse between a motor neurone and muscle fibre

Question 25

Motor units

Answer 25

A single motor neurone with all muscle fibres it innervates Humans have 420k motor neurone and 259 mil skeletal muscle fibres

Question 26

Reflex action

Answer 26

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

Question 27

Reflex action when tendon hammer hits patella ligament

Answer 27

1. Stretching stimulates **sensory receptor** (muscle spindle) 2. **Sensory neurone** activated 3. Sensory neurone activates **motor neurone** within the spinal cord (integrating centre) 4. **Motor neurone** is activated 5. Effector (**quadricep muscle of thigh**) contracts -

Question 28

Which cranial nerves do visceral sensory neurones run into

Answer 28

IX - Glossopharyngeal Nerve X - Vagus Nerve Relay painn fullness and bp

Question 29

What do the visceral motor neurones control?

Answer 29

Pupils, sweat glands, salivary glands, heart muscle, airways -thoracolumbar and craniosacral outflow Cranial nerves 3,7,9,10

Question 30

Where is the sympathetic system said to have its outflow and what is this outflow known as?

Answer 30

Thoracolumbar region of spinal cord So cells only emerge from T1 to L2 Thoracolumbar outflow

Question 31

Where is the parasympathetic system said to have its outflow and what this outflow also known as?

Answer 31

Pre-ganglionic neurones emerge from the brain stem and sacral portion of spinal cord Craniosacral outflow

Question 32

Where does visceral motor synapse

Answer 32

For sympathetic if going to head or skin it synapses in sympathetic chain and elsewhere it synapses to pre aortic ganglia For parasympathetic it synapses in ganglia

Question 33

Sympathetic outflow to periphery

Answer 33

Sympathetic nerves arise from thoracic and lumbar region forming sympathetic chain Form the symmetric chain post ganglionic fibres project to target tissues in periphery Controls blood vessel diameter and pilo erection

Question 34

Anatomy of sympathetic outflow to heart

Answer 34

Sympathetic nerves innervate cardiac plexus . Post ganglionic fibres release noradrenaline onto cardiac plexus

Question 35

Sympathetic outflow to heart

Answer 35

Cervical chord have no preganglionic neurons s they have no lateral horn T1-T4 have preganglionic neurones which go into sympathetic chain which synapse or go into another chain and synapse Sympathetic nerves going to heart have preganglionic chord which go into chain synapses at the same level or else where

Question 36

Sympathetic outflow to viscer

Answer 36

To the heart synapse in sympathetic chain To skin synapse in sympathetic chain Other organs synapses at other gangli at the front of the aorta All start in preganglionic neurons of throacolumbar chord. They synapse at pre aortic ganglia synapse