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Questions and Answers
How many pairs of spinal nerves are primarily present in the human peripheral nervous system?
How many pairs of spinal nerves are primarily present in the human peripheral nervous system?
Which division of the autonomic nervous system prepares the body for emergencies?
Which division of the autonomic nervous system prepares the body for emergencies?
What is the primary function of the parasympathetic nervous system?
What is the primary function of the parasympathetic nervous system?
Which plexus is responsible for providing nerve connections to the arms and hands?
Which plexus is responsible for providing nerve connections to the arms and hands?
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Which of the following actions is classified as voluntary?
Which of the following actions is classified as voluntary?
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What are the two main types of neurons found in the peripheral nervous system?
What are the two main types of neurons found in the peripheral nervous system?
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What part of the body does the cervical plexus primarily connect to?
What part of the body does the cervical plexus primarily connect to?
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How does the sympathetic nervous system affect heart rate?
How does the sympathetic nervous system affect heart rate?
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What areas of the body does the sacral plexus connect to?
What areas of the body does the sacral plexus connect to?
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Which cervical nerve root is primarily responsible for motor innervation of the diaphragm?
Which cervical nerve root is primarily responsible for motor innervation of the diaphragm?
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Which of the following nerves provides sensory information to the external ear?
Which of the following nerves provides sensory information to the external ear?
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What structure serves as the loop of nerves part of the cervical plexus?
What structure serves as the loop of nerves part of the cervical plexus?
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The cervical plexus primarily provides which type of innervation to the sternocleidomastoid muscle?
The cervical plexus primarily provides which type of innervation to the sternocleidomastoid muscle?
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How are the major trunks of the brachial plexus formed?
How are the major trunks of the brachial plexus formed?
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Which cord of the brachial plexus is formed by the anterior division of the inferior trunk?
Which cord of the brachial plexus is formed by the anterior division of the inferior trunk?
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What do the posterior rami of the spinal nerves primarily innervate?
What do the posterior rami of the spinal nerves primarily innervate?
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The anterior division of which trunks contributes to the lateral cord of the brachial plexus?
The anterior division of which trunks contributes to the lateral cord of the brachial plexus?
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What is the primary function of the supraclavicular nerves?
What is the primary function of the supraclavicular nerves?
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What muscles are innervated by the musculocutaneous nerve?
What muscles are innervated by the musculocutaneous nerve?
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Which nerve is primarily affected in Klumpke Palsy?
Which nerve is primarily affected in Klumpke Palsy?
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What is a major symptom of Erb’s Palsy?
What is a major symptom of Erb’s Palsy?
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Which description best defines the sensory functions of the median nerve?
Which description best defines the sensory functions of the median nerve?
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Which nerve innervates the triceps brachii muscle?
Which nerve innervates the triceps brachii muscle?
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Which function is NOT affected by an upper brachial plexus injury?
Which function is NOT affected by an upper brachial plexus injury?
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What sensory function is lost in Erb’s Palsy?
What sensory function is lost in Erb’s Palsy?
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Which of the following nerves does NOT arise from the C5 root of the brachial plexus?
Which of the following nerves does NOT arise from the C5 root of the brachial plexus?
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Which thoracic nerves are primarily responsible for affecting the muscles of the upper chest, mid-back, and abdomen?
Which thoracic nerves are primarily responsible for affecting the muscles of the upper chest, mid-back, and abdomen?
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Which spinal nerves are associated with the iliohypogastric nerve?
Which spinal nerves are associated with the iliohypogastric nerve?
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Injury to the T1-T5 thoracic nerves primarily affects which part of the body?
Injury to the T1-T5 thoracic nerves primarily affects which part of the body?
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What is the function of thoracic nerves T6-T12?
What is the function of thoracic nerves T6-T12?
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Where do the medial branches of the upper 6 thoracic nerves reach?
Where do the medial branches of the upper 6 thoracic nerves reach?
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Which thoracic nerve section is responsible for affecting the hands and fingers?
Which thoracic nerve section is responsible for affecting the hands and fingers?
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What effect does an injury to the T6-T12 thoracic nerves have on bowel and bladder control?
What effect does an injury to the T6-T12 thoracic nerves have on bowel and bladder control?
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Which of the following muscles does the ilioinguinal nerve innervate?
Which of the following muscles does the ilioinguinal nerve innervate?
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What area of the body does the genital branch innervate in females?
What area of the body does the genital branch innervate in females?
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Which nerve innervates the skin on the upper anterior thigh?
Which nerve innervates the skin on the upper anterior thigh?
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Which of the following muscles are innervated by the Sciatic Nerve?
Which of the following muscles are innervated by the Sciatic Nerve?
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What is the sensory function of the Femoral Nerve?
What is the sensory function of the Femoral Nerve?
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Which nerves are included in the sacral plexus?
Which nerves are included in the sacral plexus?
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Which muscle is exclusively innervated by the Inferior Gluteal Nerve?
Which muscle is exclusively innervated by the Inferior Gluteal Nerve?
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What type of nerve fibers make up the Sacral Nerves?
What type of nerve fibers make up the Sacral Nerves?
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Which area is innervated by the Tibial portion of the Sciatic Nerve?
Which area is innervated by the Tibial portion of the Sciatic Nerve?
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Study Notes
Peripheral Nervous System (PNS)
- Conducts impulses to and from the Central Nervous System (CNS)
- Contains both motor and sensory neurons
- Consists of 31 pairs of nerves connected to the spinal cord
- 8 Cervical
- 12 Thoracic
- 5 Lumbar
- 5 Sacral
Voluntary and Involuntary Actions
- Voluntary (somatic) actions are controlled by the somatic nervous system, which consists of afferent (sensory) and efferent (motor) nerves
- Examples: picking up a cup
- Involuntary (autonomic) actions are controlled by the autonomic nervous system
- Examples: heart beating, digestion
- The autonomic nervous system is divided into 2 branches:
- Sympathetic nervous system - "Fight or Flight"
- Prepares the body for emergencies by shunting blood to muscles and increasing blood pressure, heart rate, and breathing rate
- Parasympathetic nervous system - "Rest & Digest"
- Maintains and restores energy by directing blood to the digestive tract and maintaining a low blood pressure, heart rate, and breathing rate
- Sympathetic nervous system - "Fight or Flight"
Plexuses
- The PNS contains four major nerve plexuses that provide connections to different parts of the body:
- Cervical plexus
- Connects to head, neck, and shoulder
- Brachial plexus
- Connects to chest, shoulders, upper arms, forearms, and hands
- Lumbar plexus
- Connects to back, abdomen, groin, thighs, knees, and calves
- Sacral plexus
- Connects to pelvis, buttocks, genitals, thighs, calves, and feet
- Cervical plexus
Cervical Plexus
- Consists of 8 nerves (C1-C8), though there are only 7 cervical vertebrae
- Nerve C8 emerges below C7 vertebrae
- Consists of motor and sensory branches
- Motor branches innervate the muscles of the neck, back, and diaphragm
- Phrenic nerve (C3-C5) supplies motor innervation to the diaphragm
- Sensory branches innervate the skin of the neck, upper thorax, scalp, and ear
- Greater Auricular nerve (C2,C3): Sensation to external ear and over the parotid gland
- Transverse Cervical nerve (C2.C3): Sensation to anterior neck
- Lesser Occipital nerve (C2): Sensation to posterosuperior scalp
- Supraclavicular nerves (C3,C4): Sensation over supraclavicular fossa, upper thoracic region, and sternoclavicular joint
- Motor branches innervate the muscles of the neck, back, and diaphragm
Brachial Plexus
- A network of nerves that supplies skin and musculature of the upper limb
- Begins in the neck, passes through the axilla to the upper extremities
- Divided into 5 parts: roots, trunks, divisions, cords, and branches
- Roots: Each pair leave the spinal cord through intervertebral foramina
- Trunks: At the base of the neck, the roots converge to form 3 trunks:
- Superior trunk (C5 and C6 roots)
- Middle trunk (C7 roots)
- Inferior trunk (C8 and T1 roots)
- Divisions: Each trunk divides into 2 branches (anteriorly and posteriorly), passing through the axilla
- Cords: Once in the axilla, the branches recombine to form 3 cords, named according to their position to the axillary artery:
- Lateral cord (anterior division of the superior trunk and anterior division of the middle trunk)
- Posterior cord (posterior division of the superior trunk, posterior division of the middle trunk, and posterior division of the inferior trunk)
- Medial cord (anterior division of the inferior trunk)
- Branches: 5 major branches:
- Musculocutaneous Nerve (C5, C6, C7): Innervates brachialis and biceps brachii muscles; Sensory functions: Lateral half of anterior forearm and small portion of posterior forearm
- Axillary Nerve (C5, C6): Innervates teres minor and deltoid muscles; Sensory functions: Inferior region of deltoid ("regimental badge" area)
- Median Nerve (C6, C7, C8, T1): Innervates flexor muscles in forearm, thenar muscle, index and middle fingers; Sensory functions: Lateral part of palm, lateral 3 ½ fingers on palmer side of hand
- Radial Nerve (C5, C6, C7, C8, T1): Innervates triceps brachii, extensors wrist and fingers; Sensory functions: Posterior aspect of arm and forearm, posterolateral aspect of hand
- Ulnar Nerve (C8, T1): Innervates muscles of the hand; Sensory functions: Anterior and posterior surface of medial 1 ½ fingers and associated palm area
Injury to Brachial Plexus
- Upper brachial plexus injury (Erb’s Palsy): Affects C5 and C6
- Muscles paralysed: Supraspinatus, infraspinatus, subclavius, biceps brachii, brachialis, coracobrachialis, deltoid, and teres minor
- Motor functions lost or weakened: Abduction at shoulder, lateral rotation of arm, supination of forearm, and flexion at shoulder
- Sensory functions lost: Lateral aspect of arm (sensory innervation of the axillary and musculocutaneous nerves)
- Lower brachial plexus injury (Klumpke Palsy):
- Affects nerves derived from the T1 root: ulnar and median nerves
- Muscles paralysed: All the intrinsic hand muscles (flexor muscles in the forearm are also supplied by the ulnar and median nerves)
- Primary symptom: "Claw hand" due to unopposed action of finger extensor muscles; paralysis of lumbrical muscles creates extension of the metacarpophalangeal joints and flexion of the interphalangeal joints
- Sensory function lost: Medial side of arm
Thoracic Nerves
- 12 spinal nerves that emerge from the thoracic vertebrae (T1-T12)
- Branches also connect directly to the paravertebral ganglia of the Autonomic Nervous System (ANS)
- Anterior division:
- Intercostal nerves (T1-T11)
- T2 and T3 branch to intercostobrachial nerve
- Subcostal nerve (T12)
- Intercostal nerves (T1-T11)
- Posterior division:
- Medial branches (upper 6 thoracic nerves) pierce the rhomboid and trapezius muscles to reach the skin, called the medial cutaneous ramus
Function of Thoracic Nerves
- T1-T5: Affect muscles of the upper chest, mid-back, and abdomen
- Function: Control rib cage, lungs, and diaphragm
- T6-T12: Affect abdominal and back muscles
- Function: Assist with balance and posture, help with coughing and expelling foreign objects from airways
Injury to Thoracic Nerves
- Injury to T1-T5: Usually affects abdominal, lower back, and legs
- Paraplegia
- Hand and arm function are usually normal
- Injury to T6-T12: Usually results in paraplegia
- Little or no control of bowel and bladder
Lumbar Nerves
- 5 Spinal nerves (L1-L5)
- Lumbar plexus
- Iliohypogastric Nerve (L1, with contribution from T12)
- Motor Functions: Innervates internal oblique and transversus abdominis
- Sensory Functions: Innervates posterolateral gluteal skin in the pubic region
- Ilioinguinal Nerve (L1):
- Motor Functions: Innervates internal oblique and transversus abdominis
- Sensory Functions: Innervates the skin on the upper middle thigh; also supplies the skin over the root of the penis and anterior scrotum (males) or over mons pubis and labia majora (females)
- Genitofemoral Nerve (L1, L2):
- Motor Functions: Genital branch innervates the cremasteric muscle
- Sensory Functions: Genital branch innervates the skin of the anterior scrotum (males) or the skin over mons pubis and labia majora (females); femoral branch innervates the skin on the upper anterior thigh
- Lateral Cutaneous Nerve of the Thigh (L2, L3):
- Motor Functions: None
- Sensory Functions: Innervates the anterior and lateral thigh down to the knee
- Obturator Nerve (L2, L3, L4):
- Motor Functions: Innervates obturator externus, pectineus, adductor longus, adductor brevis, adductor magnus, and gracilis muscles
- Sensory Functions: Innervates the skin over the medial thigh
- Femoral Nerve (L2, L3, L4):
- Motor Functions: Innervates illiacus, pectineus, sartorius, and all muscles of quadriceps femoris
- Sensory Functions: Innervates the skin on the anterior thigh and the medial leg
- Iliohypogastric Nerve (L1, with contribution from T12)
Sacral Nerves
- 5 pairs of nerves that begin at the cauda equina, descending into the sacrum
- Sacral plexus and lumbosacral plexus
- Supply much of the hip, thigh, leg, and foot
- Include efferent and afferent fibers
- Provide sensory perception and movement of the lower body
Sacral Plexus
- Superior Gluteal Nerve (L4, L5, S1):
- Motor Functions: Innervates gluteus minimus, gluteus medius, and tensor fascia lata
- Sensory Functions: None
- Inferior Gluteal Nerve (L5.S1, S2):
- Motor Functions: Innervates gluteus maximus
- Sensory Functions: None
- Sciatic Nerve (L4, L5, S1, S2, S3):
- Motor Functions:
- Tibial portion: Innervates muscles in the posterior compartment of the thigh (excluding short head of biceps femoris), hamstring component of adductor magnus, all muscles in the posterior compartment of the leg and sole of the foot
- Common fibular portion: Innervates short head of biceps femoris, all muscles in the anterior and lateral compartments of the leg and extensor digitorum brevis
- Sensory Functions:
- Tibial portion: Innervates the skin on the posterolateral and medial surfaces of the foot as well as the sole of the foot
- Common fibular portion: Innervates the skin on the anterolateral surface of the leg and the dorsal aspect of the foot
- Motor Functions:
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Description
This quiz covers the structure and functions of the Peripheral Nervous System (PNS), including its components, types of nerves, and the distinction between voluntary and involuntary actions. Explore how the somatic and autonomic systems operate in everyday activities and emergency situations.
