M2 Topic 7: Peripheral Nervous System Flashcards
(40 cards)
1
Q
What is the PNS composed of?
A
‘All the rest’ of the nervous system besides the brain and spinal cord
- Includes cranial and spinal nerves which carry fibres from CNS to body
3 parts of the PNS are…
- Autonomic (involuntary) motor nerves
- Somatic (voluntary) motor nerves
- Sensory fibres
2
Q
Nerves
A
Big bundle of axons wrapped in connective tissue coverings only found in the PNS
- Carry info from CNS to body and vice-versa
- Cranial nerves (exiting from skull)
- Spinal nerves (exiting from spine)
3
Q
Nerve structure
A
- Endoneurium = wrapping of each nerve fibres (axons)
- Perineurium = surrounds group of nerve fibres forming a fascicle (bundle of axons)
- Epineurium = covering over entire nerve, dura mater blends into it at intervertebral foramen
4
Q
Cranial nerves
A
- 12 paired nerves in back of brain composed of both sensory and motor fibres
- Innervate face, neck, torso
- Carry sensory info about taste, smell, hearing and sensations
- Motor control of facial expressions
5
Q
Spinal nerves
A
- 31 paired nerves form spinal cord all composed of both sensory and motor fibres
- Formed from dorsal and ventral roots exiting spinal cord
- These then branch into dorsal and ventral rami
- Dorsal rami supply skin & muscles of back
- Ventral ramus form plexuses and supply anterior trunk & limbs
- Transmit sensory, motor, and autonomic signals between spinal cord and body
6
Q
What are the 12 cranial nerves?
A
- Olfactory
- Optic
- Oculomotor
- Trochlear
- Trigeminal
- Abducent
- Intermediate
- Vestibulocochlear
- Glossopharyngeal
- Vagus
- Accessory
- Hypoglossal
7
Q
Which cranial nerves only carry sensory fibres?
A
- Olfactory (I)
- Optic (II)
- Vestibulocochlear (VIII)
8
Q
Which cranial nerves carry both motor and sensory?
A
- Trigeminal (V)
- Glossopharyngeal (IX)
- Vagus (X)
- Intermediate (VII)
9
Q
Which cranial nerves only carry motor fibres?
A
- Oculomotor (III)
- Trochlear (IV)
- Abducent (VI)
- Accessory (XI)
- Hypoglossal (XII)
10
Q
Olfactory (I)
A
Sensory
- Nose
11
Q
Optic (II)
A
Sensory
- Eye
12
Q
Oculomotor (III)
A
Motor
- All eye muscles except those supplied by IV and VI
13
Q
Trochlear (IV)
A
Motor
- Superior oblique muscle
14
Q
Trigeminal (V)
A
Sensory
- Face, sinuses, teeth, etc.
Motor
- Muscles of mastication
15
Q
Abducent (VI)
A
Motor
- External rectus muscle
16
Q
Facial (VII)
A
Motor
- Muscles of the face
- Includes branch called the intermediate nerve
17
Q
Intermediate (VII)
A
Motor
- Submaxillary and sublingual gland
Sensory
- Anterior part of tongue and soft palate
18
Q
Vestibulocochlear (VIII)
A
Sensory
- Inner ear
19
Q
Glossopharyngeal (IX)
A
Motor
- Pharyngeal musculature
Sensory
- Posterior part of tongue, tonsil, pharynx
20
Q
Vagus (X)
A
Motor
- Heart, lungs, bronchi, gastrointestinal tract
Sensory
- Heart, lungs, bronchi, trachea, larynx, GI tract, external ear
21
Q
Accessory (XI)
A
Motor
- Sternocleidomastoid and trapezius muscles
22
Q
Hypoglossal (XII)
A
Motor
- Muscles of the tongue
23
Q
How are the spinal nerves organised?
A
Named & numbered by cord level of origin
- Cervical nerves (C1-C8)
- Thoracic nerves (T1-T12)
- Lumbar nerves (L1-L5)
- Sacral nerves (S1-S5)
- 1 pair of coccygeal nerves
24
Q
Nerve plexuses
A
Proximal segments of peripheral nerves emerging from the spine with interchanging and intermingling axons from different spinal levels that then form individual nerves
- Composed of sensory and motor fibres from merging of ventral rami of spinal nerves to form plexuses (nerve networks)
- Found in neck, arm, low back, & sacral regions
25
What are the four plexuses?
- Cervical
- Brachial
- Lumbar
- Sacral
No plexus in thoracic region
26
Cervical plexus
Head, neck and shoulders
- Ventral rami of nerves C1-C5
- Keeps diaphragm moving
27
Brachial plexus
Chest, shoulders, arms, hands
- Ventral rami of nerves C5-T1
- Flexors of wrist and hand
- Pins and needles in hand
28
Lumbar plexus
Back, abdomen, groin, thighs, knees, calves
- Ventral rami of L1-L4
29
Sacral plexus
Pelvis, buttocks, genitals, thighs, calves, feet
- Ventral rami of L4-L5 & S1-S4
30
Dermatome
Area of skin supplied by one spinal nerve
- Overlap prevents loss of sensation if one damaged
31
Myotomes
Group of muscles supplied by motor fibres of a single spinal nerve
32
Somatic (motor) nervous system
Voluntary part of PNS, composed of motor fibres which control skeletal muscle
- Fibres of somatic nervous system run in spinal nerves and cranial nerves
- Involved in spinal reflexes such as withdrawal (flexor) reflex (a polysynaptic spinal reflex) e.g. pull hand away from hot stove
33
Motor control of the body
Occupies large area of cortex in front of the central sulcus (groove)
- Area contains cortical 'map' of areas they are responsible for
- Bigger areas of cortex dedicated to areas that require fin motor movement (e.g. hands very dexterous)
34
Parts of the brain that control body movement
- Precentral gyrus (cortex in front of centre sulcus) of cerebral cortex
- Basal ganglia
- Cerebellum
35
Precentral gyrus of cerebral cortex
- Initiate and control precise movements
- Neurons are called upper motor neurons
- Map of cortical area need is larger if number of motor units in muscle is high
36
Basal ganglia
Muscle tone & integrate semi-voluntary movements
37
Cerebellum
Smooth movements & maintain posture and balance
38
Somatic motor pathways
- Direct pathway
- Indirect pathway
39
Direct (motor) pathway
Synapses in spinal cord
Upper motor neurons: 1 million in cerebral cortex
- 90% of fibres cross-over in medulla = skilled movements hands and feet, right side of brain controls most left side muscles
- 10% don't cross over = control of neck & trunk muscles
Lower motor neurons
- Connect with muscle, receive input from upper motor neurons via interneurons
Cranial nerves
- Movement of eyes, tongue, chewing, expressions & speech
40
Indirect pathway
Synapses in...
- Basal ganglia
- Thalamus
- Reticular formation
- Cerebellum
