Peripheral nerves system PNS (ch13)

Question 1

What is the peripheral nervous system?

Answer 1

PNS links CNS to body
and to external environment
– Sensory:
* Somatic
* Visceral
– Motor:
* Somatic
* Visceral (Autonomic)

Question 2

Name all the Cranial Nerves I - XII?

Answer 2

• CN I – Olfactory n
• CN II – Optic n.
• CN III – Oculomotor n.
• CN IV – Trochlear n.
• CN V – Trigeminal n.
• CN VI – Abducens n.
• CN VII – Facial n.
• CN VIII – Vestibulocochlear n.
• CN IX – Glossopharyngeal n.
• CN X – Vagus n.
• CN XI – Spinal accessory n.
• CN XII – Hypoglossal n.

Question 3

What is the function of each of the cranial nerves?

Answer 3

• CN I – Olfactory Nerve
  Function: Sensory nerve for the sense of smell.
• CN II – Optic Nerve
  Function: Sensory nerve responsible for vision.
• CN III – Oculomotor Nerve
  Function: Motor nerve controlling most eye movements and pupil constriction.
• CN IV – Trochlear Nerve
  Function: Motor nerve controlling the superior oblique eye muscle.
  -CN V – Trigeminal Nerve
  Function: Mixed nerve with sensory function for the face and motor function for chewing muscles.
• CN VI – Abducens Nerve
  Function: Motor nerve controlling the lateral rectus eye muscle.
  -CN VII – Facial Nerve
  Function: Mixed nerve with sensory functions for taste and motor functions for facial expressions, tear and saliva secretion.
• CN VIII – Vestibulocochlear Nerve
  Function: Sensory nerve for hearing and balance.
• CN IX – Glossopharyngeal Nerve
  Function: Mixed nerve with sensory functions for taste and touch in the back of the tongue and motor functions for swallowing.
• CN X – Vagus Nerve
  Function: Mixed nerve involved in various functions, including speech, swallowing, and autonomic control of visceral organs.
  -CN XI – Spinal Accessory Nerve
  Function: Motor nerve controlling certain neck muscles.
• CN XII – Hypoglossal Nerve
  Function: Motor nerve controlling the muscles of the tongue.

Question 4

What is Anosmia?

Answer 4

• An: without somia: smell
• Anosmia refers to the loss or absence of the sense of smell.

Question 5

What is anopia?

Answer 5

• Definition: Anopia is a medical term referring to the absence or loss of vision in one or both eyes.
  1) Ipsilateral Blindness: Total blindness in one eye. Causes: Damage to the optic nerve or retina on one side.
  2) Bitemporal Hemianopia: Loss of vision in the outer half of both visual fields.
  Cause: Lesions affecting the optic chiasm (optic crossing)

Question 6

CN IV – Trochlear n

Answer 6

Superior oblique m.
– SO4
* Intorsion (medially)
* Depression (inferiorly)
* Abduction

Question 7

CN V – Trigeminal n

Answer 7

Principle sensory n. to face
* Three brr.
– Ophthalmic br. (CN V1)
* sensory
– Maxillary br. (CN V2)
* sensory
– Mandibular br. (CN V3)
* sensory & motor

Question 8

CN VI (Abducens Nerve)

Answer 8

Innervated Muscle: Lateral rectus muscle.
Function: Abducts the eye (moves it laterally).
Mnemonic: “LR6” - Lateral Rectus is innervated by CN VI.

Question 9

CN VI – Abducen n. palsy

Answer 9

Medial Strabismus: Inward deviation of the affected eye.
Diplopia: Double vision due to misalignment of the eyes.
Note: CN VI controls the lateral rectus muscle, responsible for moving the eye outward. Palsy leads to an imbalance in eye muscle function.

Question 10

CN VII (Facial Nerve)

Answer 10

Makes Muscles Move:
Helps you make facial expressions.
Takes care of the parotid gland.
Keeps Things Moist:
Manages the saliva and tears.
Taste and Feel:
Deals with taste on the front part of your tongue.
Takes care of feelings on your ear and around it.

Question 11

CN VIII (Vestibulocochlear Nerve)?

Answer 11

Double Duty Nerve:
Splits into two parts: Cochlear (for hearing) and Vestibular (for balance).
Cochlear Branch:
Responds to sound waves, helping you hear.
Vestibular Branch:
Reacts to body positions, maintaining balance and equilibrium.

Question 12

CN IX (Glossopharyngeal Nerve)

Answer 12

*Motor Functions:
Controls Stylopharyngeus and Superior Pharyngeal Constrictor muscles.
* Parasympathetic Control:
Influences the Parotid Gland.
* Sensory Domains:
Handles various sensory functions in areas like pharyngotympanic tubes, palatine tonsils, oropharynx, and the posterior 1/3 of the tongue.
* Gustatory Sensation:
Involved in taste perception for the posterior 1/3 of the tongue.

Question 13

CN X (Vagus Nerve)

Answer 13

• Sensory Neurons: Monitors sensations in the inferior pharynx, larynx, thoracic organs, and visceral organs.
• Somatic Motor Neurons: Controls muscles of the soft palate, pharynx, and intrinsic laryngeal muscles.
• Visceral Motor Neurons: Influences the function of vital organs like the heart, esophagus, stomach, small intestine, large intestine, and gallbladder.

Question 14

CN XI (Accessory Nerve)

Answer 14

• Cranial Component:
  *Travels with CN X (Vagus Nerve).
  *Innervates muscles of the larynx involved in speech.
• Spinal Component:
  *Controls the sternocleidomastoid and trapezius muscles.

Question 15

Overview of cranial nerves

Answer 15

Only sensory neurons
– Olfactory (I)
– Optic (II)
– Vestibulocochlear (VIII)
* Primarily motor neurons
– Oculomotor (III)
– Trochlear (IV)
– Abducen (VI)
– Accessory (XI)
– Hypoglossal (XII)
* Both sensory & motor
neurons
– Trigeminal (V)
– Facial (VII)
– Glossopharyngeal (IX)
– Vagus (X)

Question 16

Musculocutaneous Nerve

Answer 16

• Origin: Lateral cord
• Innervates:
  Coracobrachialis muscle
  Biceps brachii muscle
  Brachialis muscle

Question 17

Median Nerve

Answer 17

• Origin: Medial and lateral cords
• Motor:
  *Flexor muscles of forearm and digits
  *Some muscles of the hand
  Sensory:
  *Anterior thumb
  *Anterior 2nd, 3rd, and 4th (lateral half) digits
  *Palm of the hand

Question 18

Ulnar Nerve?

Answer 18

Origin: Medial cord
Motor:
Flexor muscles of the forearm
Most intrinsic hand muscles
Sensory:
5th digit
4th (medial half) digits

Question 19

Radial Nerve

Answer 19

Origin: Posterior cord
Motor:
- Triceps brachii muscle
- Brachioradialis muscle
- Extensor muscles of the forearm and digits

Question 20

Radial nerve

Answer 20

Origin: Posterior cord
Motor:
Triceps brachii muscle
Brachioradialis muscle
Extensor muscles of the forearm and digits
Sensory:
Posterior arm
Posterior forearm
Posterior thumb, 2nd, 3rd, and 4th (lateral half) digits

Question 21

Axillary Nerve

Answer 21

Axillary Nerve Location: Surgical neck of the humerus
Innervates:
Teres minor muscle
Deltoid muscle

Question 22

What are the Sacral Plexus?

Answer 22

• Sciatic n. (large nerves in body, thigh, leg, and foot)
• Pudendal n. ( external genitalia and surrounding areas)
• Superior gluteal n. (hip movement and stabilization)
• Inferior gluteal n. (hip extension and external rotation)

Question 23

Sensory Receptors?

Answer 23

• Exteroceptors – detect stimuli originating from outside body
• Interoceptors – detect stimuli originating from within body itself
• Mechanoreceptors – respond to chemicals in taste and smell and in internal changes.
  – depolarize in response to anything that mechanically deforms tissue where receptors
  are found.

Question 24

more Sensory Receptors?

Answer 24

• Photoreceptors – special sensory exteroceptors found
  only in eye
  – depolarize in response to light
• Nociceptors – usually slowly adapting exteroceptors
  – depolarize in response to noxious stimuli
• Thermoreceptors: detect temp

Question 25

CNS to PNS neurons?

Answer 25

*Upper Motor Neurons (UMNs): Originate in the primary motor cortex. Make decisions to move and initiate movements. Not in direct contact with muscle fibers. * Lower Motor Neurons (LMNs): Receive messages from upper motor neurons. In direct contact with skeletal muscle fibers. Release acetylcholine onto muscle fibers to initiate contraction.

Question 26

Lower Motor Neurons 3 types?

Answer 26

- Motor Neuron Pools: Groups of LMNs innervating the same muscle. - Large Motor Neurons (Alpha): Stimulate skeletal muscle fibers for contraction. - Smaller Motor Neurons (Gamma): Innervate intrafusal fibers, part of stretch receptors.

Question 27

significance of Amyotrophic Lateral Sclerosis (ALS)?

Answer 27

Also known as Lou Gehrig's disease. - Gradual loss of motor neurons, leading to muscle weakness and atrophy.