Peripheral Nervous System Overview

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Questions and Answers

How many pairs of spinal nerves are primarily present in the human peripheral nervous system?

40 pairs

31 pairs (correct)

24 pairs

36 pairs

Which division of the autonomic nervous system prepares the body for emergencies?

Sympathetic nervous system (correct)

Parasympathetic nervous system

Somatic nervous system

Voluntary nervous system

What is the primary function of the parasympathetic nervous system?

To increase blood pressure

To initiate reflex actions

To maintain and restore energy (correct)

To enhance muscle efficiency

Which plexus is responsible for providing nerve connections to the arms and hands?

Brachial plexus Signup and view all the answers

Which of the following actions is classified as voluntary?

Picking up a cup Signup and view all the answers

What are the two main types of neurons found in the peripheral nervous system?

Motor and sensory neurons Signup and view all the answers

What part of the body does the cervical plexus primarily connect to?

Head, neck, and shoulder Signup and view all the answers

How does the sympathetic nervous system affect heart rate?

Increases it Signup and view all the answers

What areas of the body does the sacral plexus connect to?

Pelvis, buttocks, and thighs Signup and view all the answers

Which cervical nerve root is primarily responsible for motor innervation of the diaphragm?

C3-C5 Signup and view all the answers

Which of the following nerves provides sensory information to the external ear?

Greater Auricular nerve Signup and view all the answers

What structure serves as the loop of nerves part of the cervical plexus?

Ansa Cervicalis Signup and view all the answers

The cervical plexus primarily provides which type of innervation to the sternocleidomastoid muscle?

Motor Signup and view all the answers

How are the major trunks of the brachial plexus formed?

By the convergence of cervical roots in the neck Signup and view all the answers

Which cord of the brachial plexus is formed by the anterior division of the inferior trunk?

Medial cord Signup and view all the answers

What do the posterior rami of the spinal nerves primarily innervate?

Skin and muscles of the back Signup and view all the answers

The anterior division of which trunks contributes to the lateral cord of the brachial plexus?

Superior and Middle trunks Signup and view all the answers

What is the primary function of the supraclavicular nerves?

Sensation over supraclavicular fossa and upper thoracic region Signup and view all the answers

What muscles are innervated by the musculocutaneous nerve?

Biceps brachii and brachialis Signup and view all the answers

Which nerve is primarily affected in Klumpke Palsy?

Ulnar nerve Signup and view all the answers

What is a major symptom of Erb’s Palsy?

Weakness in shoulder abduction and external rotation Signup and view all the answers

Which description best defines the sensory functions of the median nerve?

Lateral part of palm and lateral 3 ½ fingers on palmer surface Signup and view all the answers

Which nerve innervates the triceps brachii muscle?

Radial nerve Signup and view all the answers

Which function is NOT affected by an upper brachial plexus injury?

Extension of the wrist Signup and view all the answers

What sensory function is lost in Erb’s Palsy?

Sensation in the lateral aspect of the arm Signup and view all the answers

Which of the following nerves does NOT arise from the C5 root of the brachial plexus?

Ulnar nerve Signup and view all the answers

Which thoracic nerves are primarily responsible for affecting the muscles of the upper chest, mid-back, and abdomen?

T1-T5 Signup and view all the answers

Which spinal nerves are associated with the iliohypogastric nerve?

L1 and T12 Signup and view all the answers

Injury to the T1-T5 thoracic nerves primarily affects which part of the body?

Abdomen and legs Signup and view all the answers

What is the function of thoracic nerves T6-T12?

Assist with balance and posture Signup and view all the answers

Where do the medial branches of the upper 6 thoracic nerves reach?

Skin Signup and view all the answers

Which thoracic nerve section is responsible for affecting the hands and fingers?

T1 Signup and view all the answers

What effect does an injury to the T6-T12 thoracic nerves have on bowel and bladder control?

Little or no control Signup and view all the answers

Which of the following muscles does the ilioinguinal nerve innervate?

Transversus abdominis Signup and view all the answers

What area of the body does the genital branch innervate in females?

Skin over mons pubis and labia majora 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

Which of the following muscles are innervated by the Sciatic Nerve?

Muscles in the posterior compartment of the thigh Signup and view all the answers

What is the sensory function of the Femoral Nerve?

Innervates the skin on the anterior thigh and medial leg Signup and view all the answers

Which nerves are included in the sacral plexus?

Superior Gluteal and Inferior Gluteal Nerves Signup and view all the answers

Which muscle is exclusively innervated by the Inferior Gluteal Nerve?

Gluteus maximus Signup and view all the answers

What type of nerve fibers make up the Sacral Nerves?

Both efferent and afferent fibers Signup and view all the answers

Which area is innervated by the Tibial portion of the Sciatic Nerve?

Sole of the foot Signup and view all the answers

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

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

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

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)
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

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

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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.