Neuroanatomy: Spinal Nerves Overview

Questions and Answers

What is the primary function of the somatic nervous system?

To conduct sensory and motor impulses (correct)

To prepare the body for emergencies

To facilitate digestion and metabolic processes

To regulate involuntary actions such as heart rate

Which plexus is responsible for providing connections to the thighs and calves?

Cervical plexus

Sacral plexus

Brachial plexus

Lumbar plexus (correct)

Which of the following best describes the role of the sympathetic nervous system?

It aids in digestion and energy restoration

It maintains normal heart rate and blood pressure

It conducts impulses from the CNS to voluntary muscles

It prepares the body for fight or flight responses (correct)

How many pairs of spinal nerves are primarily involved in the PNS?

31 pairs Signup and view all the answers

What is the main difference between voluntary and involuntary actions in the nervous system?

Involuntary actions cannot be controlled consciously Signup and view all the answers

Which nerve is responsible for the sensory function of the lateral half of the anterior forearm?

Musculocutaneous Nerve Signup and view all the answers

What muscle is NOT innervated by the Axillary Nerve?

Biceps Brachii Signup and view all the answers

What sensory function is associated with the Radial Nerve?

Posterior aspect of arm and forearm Signup and view all the answers

Which nerve is primarily affected in Klumpke Palsy?

Ulnar Nerve Signup and view all the answers

What type of hand condition is primarily caused by the impairment of intrinsic hand muscles in Klumpke Palsy?

Claw hand Signup and view all the answers

Which function is NOT lost due to an upper brachial plexus injury (Erb’s Palsy)?

Flexion at the wrist Signup and view all the answers

Which nerve innervates the flexor muscles in the forearm?

Both A and C Signup and view all the answers

Loss of sensation along the medial side of the arm is primarily related to injury to which nerve?

Ulnar Nerve Signup and view all the answers

Which nerve innervates the skin of the anterior scrotum in males?

Genital Branch Signup and view all the answers

What is the primary motor function of the Sciatic Nerve?

Innervates the posterior compartment of the thigh and leg Signup and view all the answers

Which sensory function is associated with the Obturator Nerve?

Innervates skin over the medial thigh Signup and view all the answers

The Superior Gluteal Nerve primarily innervates which muscles?

Gluteus minimus, gluteus medius, and tensor fascia lata Signup and view all the answers

Which nerve provides no sensory functions in the gluteal area?

Inferior Gluteal Nerve Signup and view all the answers

Which nerve innervates the skin on the upper anterior thigh?

Lateral Cutaneous Nerve of the Thigh Signup and view all the answers

What is the primary sensory function of the Common fibular portion of the Sciatic Nerve?

Innervates the anterolateral surface of the leg Signup and view all the answers

Which muscles are innervated by the Femoral Nerve?

Quadriceps femoris and iliacus Signup and view all the answers

What is the primary function of the T6-T12 thoracic nerves?

Assist with balance and posture Signup and view all the answers

Which spinal nerves are responsible for innervating the intercostobrachial nerve?

T2 and T3 Signup and view all the answers

Injury to which thoracic nerves typically results in normal hand and arm function?

T1-T5 Signup and view all the answers

Which lumbar nerve contributes to the iliohypogastric nerve's sensory function?

L1 with contribution from T12 Signup and view all the answers

What body area is affected by injury to T-2 and T-5 thoracic nerves?

Chest muscles Signup and view all the answers

Which nerve innervates the skin on the upper middle thigh?

Ilioinguinal nerve Signup and view all the answers

Which segment of the thoracic nerves is primarily responsible for controlling the rib cage?

T1-T5 Signup and view all the answers

In males, which structure does the ilioinguinal nerve provide sensory innervation to?

Skin over the root of the penis Signup and view all the answers

What key function does the phrenic nerve serve?

Motor innervation for the diaphragm Signup and view all the answers

Which cervical nerves are responsible for sensory innervation to the external ear?

C2 and C3 Signup and view all the answers

What structure is formed by the anterior divisions of the superior and middle trunks in the brachial plexus?

Lateral cord Signup and view all the answers

Which nerve provides sensation to the anterior neck?

Transverse Cervical nerve Signup and view all the answers

Which of the following branches of the cervical plexus innervates the sternohyoid muscle?

Ansa Cervicalis Signup and view all the answers

Which component of the brachial plexus is specifically involved in dividing the roots into different trunks?

Divisions Signup and view all the answers

Which cervical plexus nerve is responsible for providing sensation to the posterosuperior scalp?

Lesser Occipital nerve Signup and view all the answers

How many trunks are formed at the base of the neck in the brachial plexus?

Three Signup and view all the answers

Which part of the cervical plexus supplies the skin of the neck and upper thorax?

Sensory branches Signup and view all the answers

Which structure connects the cervical plexus to the diaphragm?

Phrenic nerve Signup and view all the answers

Which nerve provides sensory innervation to the upper thoracic region and sternoclavicular joint?

Supraclavicular nerves Signup and view all the answers

What is the primary function of the Axillary nerve?

Innervates deltoid and teres minor Signup and view all the answers

Which trunk of the brachial plexus is formed exclusively by the C7 spinal nerve?

Middle trunk Signup and view all the answers

Which nerve is specifically responsible for sensation to the posterosuperior scalp?

Lesser Occipital nerve Signup and view all the answers

Which of the following provides sensation to the external ear?

Greater Auricular nerve Signup and view all the answers

Which muscle is affected by Klumpke Palsy leading to motor impairment?

Subclavius Signup and view all the answers

In Klumpke Palsy, loss of sensation occurs primarily in which area?

Medial aspect of the arm Signup and view all the answers

What is a characteristic position of the arm in Erb's Palsy?

Medially rotated and pronated Signup and view all the answers

Which nerve roots are primarily affected in Erb's Palsy due to excessive neck and shoulder angle?

C5 and C6 Signup and view all the answers

Which of the following best describes the consequence of a lower brachial plexus injury?

Loss of grip strength in the hand Signup and view all the answers

Which of the following correctly describes the formation of the lateral cord in the brachial plexus?

Formed by the anterior divisions of the superior and middle trunks Signup and view all the answers

What is the primary sensory function of the Ulna Nerve?

Anterior and posterior surface of medial 1 ½ fingers and associated palm area Signup and view all the answers

Which of the following nerves innervates the teres minor muscle?

Axillary Nerve Signup and view all the answers

What nerve is primarily affected in an upper brachial plexus injury (Erb's Palsy)?

C5 and C6 nerves Signup and view all the answers

Which trunk is formed solely by the root of C7 in the brachial plexus?

Middle trunk Signup and view all the answers

What are the functions of the Musculocutaneous Nerve?

Innervates flexor muscles in the forearm and provides sensation to the lateral half of the anterior forearm Signup and view all the answers

Which of the following accurately describes the posterior cord of the brachial plexus?

Formed by all posterior divisions of the trunks Signup and view all the answers

What type of nerve injury is Erb's Palsy?

Upper brachial plexus injury affecting C5 and C6 Signup and view all the answers

Which segment of the thoracic nerves is primarily responsible for innervating the abdominal muscles?

T9-T12 Signup and view all the answers

What function do the T6-T12 thoracic nerves primarily assist with?

Balance and posture Signup and view all the answers

Which thoracic nerve injury results in paraplegia with minimal control over bowel and bladder functions?

T6-T12 Signup and view all the answers

Which of the following nerves primarily supplies sensations to the lateral half of the anterior thigh?

Femoral nerve Signup and view all the answers

Which function is NOT affected by an injury to the thoracic nerves T1-T5?

Hands and finger movement Signup and view all the answers

Which lumbar nerve is primarily responsible for innervating the internal oblique and transversus abdominis muscles?

L1 Signup and view all the answers

The medial branches of which thoracic nerves pierce the rhomboid and trapezius muscles?

T1-T3 Signup and view all the answers

Which thoracic nerve segments primarily affect the chest muscles?

T2-T5 Signup and view all the answers

Which portion of the Sciatic Nerve innervates the short head of the biceps femoris?

Common fibular portion Signup and view all the answers

What sensory area does the tibial portion of the Sciatic Nerve cover?

Skin on the posterolateral and medial surfaces of the foot Signup and view all the answers

Which nerve innervates the external urethral sphincter?

Pudendal Nerve Signup and view all the answers

Which of the following areas is innervated by the posterior femoral cutaneous nerve?

Skin of the posterior surface of the thigh and leg Signup and view all the answers

Which muscle group is NOT innervated by the tibial portion of the Sciatic Nerve?

Muscles in the anterior compartment of the leg Signup and view all the answers

Study Notes

Spinal Nerves

Peripheral Nervous System (PNS) connects the CNS to the body, conducting impulses.
Comprises 31 pairs of nerves:
- 8 cervical nerves
- 12 thoracic nerves
- 5 lumbar nerves
- 5 sacral nerves

Voluntary & Involuntary Actions

Voluntary (somatic): Actions like picking up objects.
Involuntary (autonomic): Includes bodily functions such as heart rate and digestion.
Sympathetic Nervous System: Responsible for 'fight or flight' response, increasing blood flow to muscles, heart rate, and blood pressure.
Parasympathetic Nervous System: Promotes 'rest and digest' functions, directing blood flow to digestion and maintaining lower heart rates.

Plexuses

Cervical plexus: Nerve connections to head, neck, and shoulder.
Brachial plexus: Supplies skin and musculature of upper limbs.
Lumbar plexus: Supplies the back, abdomen, and lower limbs.
Sacral plexus: Innervates pelvis, buttocks, and lower legs.

Cervical Nerves

7 cervical vertebrae but 8 cervical nerves (C1-C8); C8 emerges below C7.
Cervical plexus (C1-C4) consists of:
- Motor branches: Innervate neck and diaphragm muscles.
  - Phrenic nerve (C3-C5): Crucial for diaphragm innervation.
- Sensory branches: Provide sensation to neck, upper thorax, scalp, and ear.

Brachial Plexus

Comprises roots (C5-T1), trunks, divisions, cords, and branches.
Superior trunk: C5-C6; Middle trunk: C7; Inferior trunk: C8-T1.
Major branches include:
- Musculocutaneous Nerve: Innervates biceps and brachialis.
- Axillary Nerve: Innervates deltoid and teres minor.
- Median Nerve: Innervates flexor muscles and sensation to lateral palm.
- Radial Nerve: Innervates triceps and sensory to posterior arm.
- Ulnar Nerve: Innervates hand muscles and provides sensation to medial fingers.

Injuries

Upper brachial plexus injury (Erb's Palsy): Affects C5-C6, impairing shoulder and arm movements.
Klumpke Palsy: Involves T1 root, causing hand muscle paralysis and sensory loss on medial arm.

Thoracic Nerves

12 spinal nerves (T1-T12) control upper chest, mid-back, and abdomen.
Anterior division: Intercostal nerves for rib control.
Posterior division: Medial branches innervate upper back skin.

Lumbar Nerves

5 spinal nerves (L1-L5) form the lumbar plexus.
Contains nerves like:
- Iliohypogastric and Ilioinguinal: Innervate abdominal muscles and skin in the pelvic regions.
- Genitofemoral: Innervates the cremasteric muscle and skin of the thigh.
- Femoral: Supplies quadriceps and provides sensation to the anterior thigh.

Sacral Nerves

5 pairs of nerves, including the sciatic nerve, which is crucial for lower limb movement and sensation.
Major branches include:
- Superior Gluteal Nerve: Innervates gluteus minimus and medius.
- Sciatic Nerve: Tibial portion innervates posterior thigh muscles, while the common fibular portion innervates lateral and anterior leg muscles.

Cervical Nerves

Greater Auricular nerve (C2, C3): Provides sensation to the external ear and parotid gland.
Transverse Cervical nerve (C2, C3): Responsible for sensation to the anterior neck.
Lesser Occipital nerve (C2): Supplies sensation to the posterosuperior scalp.
Supraclavicular nerves (C3, C4): Convey sensation over the supraclavicular fossa and the upper thoracic region, including the sternoclavicular joint.

Brachial Plexus

Consists of roots (C5-T1), trunks, divisions, cords, and branches, supplying the skin and musculature of the upper limb.
Roots converge to form three trunks: Superior (C5-C6), Middle (C7), and Inferior (C8-T1).
Trunks divide into anterior and posterior divisions within the posterior triangle of the neck, passing through the axilla.

Brachial Plexus Cords

Three cords named for their position relative to the axillary artery:
- Lateral cord: Formed by anterior divisions of the superior and middle trunks.
- Posterior cord: Formed by posterior divisions of all three trunks.
- Medial cord: Formed by the anterior division of the inferior trunk.

Major Branches of Brachial Plexus

Musculocutaneous Nerve (C5, C6, C7): Innervates biceps brachii and brachialis; sensory to lateral anterior forearm and a portion of the posterior forearm.
Axillary Nerve (C5, C6): Innervates deltoid and teres minor; sensory to the inferior region of the deltoid ("regimental badge").
Median Nerve (C6, C7, C8, T1): Supplies flexor muscles of the forearm and sensation to the lateral palm and lateral 3.5 fingers.
Radial Nerve (C5, C6, C7, C8, T1): Innervates triceps and extensors of the wrist and fingers; sensory to the posterior arm and forearm.
Ulnar Nerve (C8, T1): Innervates hand muscles; sensory to anterior and posterior surfaces of medial 1.5 fingers.

Brachial Plexus Injuries

Erb's Palsy (Upper Brachial Plexus Injury): Affects C5-C6; leads to shoulder and arm movement impairments. Typical presentation includes "waiter's tip" position.
Klumpke's Palsy (Lower Brachial Plexus Injury): Affects T1; causes hand muscle paralysis and sensory loss in the medial arm.

Thoracic Nerves

Comprised of 12 spinal nerves (T1-T12) controlling the upper chest, mid-back, and abdomen.
Anterior division forms intercostal nerves for rib control, and the posterior division innervates the upper back skin.

Functions of Thoracic Nerves

T1-T5: Affect upper chest, mid-back, and abdominal muscles; control rib cage, lungs, diaphragm.
T6-T12: Affect abdominal and back muscles; assist with balance, posture, coughing, and expulsion from airways.

Lumbar Nerves

Formed by five spinal nerves (L1-L5) with branches innervating abdominal muscles and skin in pelvic regions.
Lumbar Plexus: Includes important nerves, such as Iliohypogastric (L1), Genitofemoral, and Femoral nerves which innervate specific muscles.

Sciatic Nerve

Comprised of Tibial (L4, L5, S1, S2, S3) and Common Fibular portions; innervates the posterior thigh muscles and provides sensory innervation to the foot.
Sciatica refers to pain associated with dysfunction of the sciatic nerve.

Posterior Femoral Cutaneous and Pudendal Nerves

Posterior Femoral Cutaneous (S1, S2, S3): Provides sensory functions to the posterior thigh and leg and perineal skin.
Pudendal Nerve (S2, S3, S4): Innervates perineal skeletal muscles, external urethral and anal sphincters, and provides sensation to genitalia and perineum.

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Description

This quiz focuses on the structure and function of spinal nerves within the peripheral nervous system (PNS). It discusses the role of spinal nerves in conducting impulses to and from the central nervous system (CNS) and highlights the significance of motor and sensory neurons. Test your knowledge on the 31 pairs of spinal nerves and their connections.