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Questions and Answers
What is the primary function of the peripheral nervous system (PNS)?
Which statement is true about spinal nerves?
How many pairs of spinal nerves are connected to the spinal cord?
Which of the following is the correct breakdown of the 31 pairs of spinal nerves?
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Which part of the nervous system facilitates the movement and sensory input throughout the body?
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Which part of the nervous system is involved in controlling involuntary actions like heart rate?
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Which type of nerves are responsible for transmitting signals from the CNS to muscles?
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What physiological state does the sympathetic nervous system induce?
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In which situation would the parasympathetic nervous system be most active?
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Which type of nerve would convey sensory information from the skin to the CNS?
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What is a characteristic effect of the sympathetic nervous system on the body?
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Which nervous system is primarily responsible for voluntary movements?
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What is the role of efferent nerves in the nervous system?
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Which part of the nervous system primarily regulates involuntary bodily functions such as breathing and heartbeat?
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What is the primary distinction between afferent and efferent nerves?
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Which of the following best describes the function of the parasympathetic nervous system?
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What physiological changes occur in the body as a result of sympathetic nervous system activation?
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Which nervous system specifically involves the transmission of signals responsible for voluntary muscle movement?
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In response to a stressful situation, the sympathetic nervous system does which of the following?
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Which of the following actions is primarily controlled by the somatic nervous system?
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What role do efferent nerves play within the nervous system?
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Which spinal nerves constitute the lumbar plexus?
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What regions does the brachial plexus primarily supply with nerves?
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The sacral plexus connects to which of the following body parts?
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Which of these spinal nerves form the cervical plexus?
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Which plexus is responsible for nerve connections to the upper limbs?
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What is the total number of cervical vertebrae present in adults?
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Which cervical nerve is positioned differently by emerging below its corresponding vertebra?
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What specific group of cervical nerves contributes to the formation of the cervical plexus?
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What is the main function of the sensory group within the cervical plexus?
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What is the primary role of the cervical plexus in the human body?
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How many cervical vertebrae and cervical nerves are present in the human body?
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Which nerve emerges below the C7 vertebra?
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What is the function of the suboccipital nerve (C1)?
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Which nerve provides sensation to the back of the scalp?
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What is the primary function of the third occipital nerve (C3)?
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What area does the anterior distribution of the cervical plexus (C1-C4) primarily affect?
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Which plexus extends from C5 to T1 and supplies nerves to the chest, shoulders, arms, and hands?
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Which nerve supplies motor innervation to muscles at the base of the skull?
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Which nerve primarily innervates the muscles located at the back of the scalp?
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Which nerve is incorrectly paired with its function?
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Which of the following statements about the cervical plexus is true?
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Which nerve originates from the upper cervical region and is primarily motor in function?
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Which nerve does not play a role in sensory innervation to the scalp?
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Which statement best describes the location of the C1 nerve?
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Which of the following is not directly associated with the cervical plexus?
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Which function is primarily attributed to the phrenic nerve?
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Where are the motor branches of the cervical plexus situated in relation to the sensory branches?
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What is a primary role of the phrenic nerve?
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Which cervical spinal nerves give rise to the phrenic nerve?
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What effect does the phrenic nerve have on breathing?
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Which function is not associated with the motor branches of the cervical plexus?
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Which statement accurately describes the role of the phrenic nerve in respiration?
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Which of the following best describes the anatomical position of the cervical plexus motor branches?
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What is the primary innervation target of the phrenic nerve?
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Which muscle is primarily responsible for depressing the larynx?
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What anatomical feature does the sternohyoid muscle specifically affect?
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What is the historical name of the Ansa Cervicalis?
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Which muscles are primarily innervated by the Ansa Cervicalis?
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What does the term 'Ansa Cervicalis' translate to in English?
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Which structure does the hyoid bone articulate with?
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What role does the sternohyroid muscle play in vocalization?
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Which nerve group is primarily responsible for innervating the muscles involved in tongue movement?
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Which cervical nerves are responsible for innervating the sternocleidomastoid muscle?
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Identify the cervical nerves that innervate the trapezius muscle.
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Which muscle is primarily innervated by the C3-C4 cervical nerves?
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Which of the following functions is linked to the trapezius muscle?
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Which cervical nerve group innervates the scalenus medius muscle?
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Which muscle is involved in lateral neck flexion and elevates the first rib during forced inspiration?
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Which of these muscles is innervated by the C2-C3 nerve roots?
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What is the primary function of the sternocleidomastoid muscle?
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What is the entry point where sensory branches of the cervical plexus enter the skin?
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The sensory branches of the cervical plexus supply which areas?
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Where is Erb’s point located?
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Which of the following areas is not supplied by the sensory branches of the cervical plexus?
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The sensory branches that supply the ear emerge from which location?
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Which landmark is known for the emergence of sensory nerves in the neck?
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From which cervical spinal nerves do the sensory branches that supply the skin of the neck originate?
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What is the primary function of the sensory branches of the cervical plexus?
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What area does the greater auricular nerve provide sensation to?
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Which nerve is responsible for sensation in the posterosuperior scalp?
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What is the primary sensory area innervated by the transverse cervical nerve?
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Which of the following nerves provides sensation to the supraclavicular region?
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Which cervical nerves contribute to the origination of the greater auricular nerve?
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Which nerve primarily innervates the area over the parotid gland?
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Sensation in the anterior neck is primarily supplied by which nerve?
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Which nerve supplies the supraclavicular fossa along with the upper thoracic region?
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Which sensory nerve of the cervical plexus provides sensation over the parotid gland?
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What area does the lesser occipital nerve (C2) primarily provide sensory innervation to?
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Which nerves are responsible for sensory input to the supraclavicular fossa?
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Which nerve primarily supplies sensation to the anterior neck?
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If a patient loses sensation of the external ear, which nerve is most likely affected?
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Which joint does the supraclavicular nerves (C3, C4) innervate?
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Which nerve would be primarily involved if there is reduced sensation over the parotid gland?
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Damage to which nerve could lead to loss of sensation in the anterior neck region?
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Which spinal nerves are responsible for the roots of the brachial plexus?
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What structure of the brachial plexus directly connects the roots to the divisions?
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In which area does the brachial plexus primarily pass through to reach the upper limbs?
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What mnemonic is used to remember the order of the parts of the brachial plexus?
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How many main parts is the brachial plexus organized into?
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What is the primary function of the brachial plexus?
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What is the correct order of parts in the brachial plexus?
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Which part of the brachial plexus is situated nearest to the spinal cord?
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What is the primary function of the anterior rami of C5-T1?
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What is the initial pathway of the roots of the brachial plexus?
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Which statement correctly describes the region innervated by the posterior rami?
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Which option best describes a function of the cervical plexus?
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What anatomical feature is characteristic of the brachial plexus pathway?
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From which spinal nerves do the roots of the brachial plexus originate?
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Where do the roots of the brachial plexus exit the spinal cord?
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After exiting the spinal cord, what do the roots of the brachial plexus do?
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Which rami of the spinal nerves contribute to the formation of the brachial plexus?
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What do the posterior rami of the spinal nerves primarily innervate?
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What is the primary function of the posterior rami?
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What describes the initial pathway that the roots of the brachial plexus take?
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Which statement about the posterior rami of the spinal nerves is true?
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How many main trunks are formed at the base of the neck by the roots of the brachial plexus?
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Which roots contribute to forming the superior trunk of the brachial plexus?
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What is the structure formed by each trunk of the brachial plexus?
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Which division of the trunks is primarily responsible for innervating the extensors of the upper limb?
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What comprises the inferior trunk of the brachial plexus?
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Which structures do the divisions of the trunks contribute to forming?
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Where do the divisions of the brachial plexus trunks pass through?
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Which two branches does each trunk of the brachial plexus divide into?
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How many main cords are formed in the axilla by the divisions of the brachial plexus trunks?
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The cords of the brachial plexus are named based on their position relative to which structure?
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Which cord of the brachial plexus is formed by the anterior division of the superior and middle trunks?
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The posterior cord of the brachial plexus is formed by:
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Which cord is formed solely by the anterior division of the inferior trunk?
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What structure do the cords of the brachial plexus surround as they pass through the axilla?
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Which of the following correctly describes the lateral cord's formation?
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The medial cord of the brachial plexus is positioned:
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Which nerve is responsible for innervating the biceps brachii and brachialis muscles?
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What sensory function does the axillary nerve provide?
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Which of the following muscles is NOT innervated by the median nerve?
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Which nerve innervates the triceps brachii muscle?
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What area does the radial nerve provide sensory information to?
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Which nerve is responsible for providing motor innervation to both the teres minor and deltoid muscles?
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Which muscles does the ulnar nerve NOT innervate?
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Which area does the sensory function of the ulnar nerve cover?
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Which nerve is primarily responsible for motor innervation to the thenar muscles and the index and middle fingers?
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Damage to which nerve is most likely to impair the ability to flex the elbow?
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The axillary nerve provides sensory innervation primarily to which area of the body?
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Which nerve is crucial for motor control of the triceps brachii muscle?
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Sensory loss in the posterolateral aspect of the hand most likely indicates damage to which nerve?
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The ulnar nerve is primarily associated with which muscle group?
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Damage to the median nerve may lead to difficulty in what specific function?
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Which nerve is responsible for sensory innervation to the anterior and posterior surfaces of the medial 1½ fingers?
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What is the range of spinal nerves that form the roots of the brachial plexus?
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The medial cord of the brachial plexus is formed by which of the following?
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From which cord does the axillary nerve arise?
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How many trunks are formed by the roots of the brachial plexus?
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Which nerve is primarily associated with the lateral cord of the brachial plexus?
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Which nerves contribute to the formation of the median nerve?
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What major nerve arises from the posterior cord of the brachial plexus?
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How many divisions are created when the trunks of the brachial plexus split?
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Which nerve roots are primarily affected in Erb’s Palsy?
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Which of the following muscles is not typically paralyzed in Erb’s Palsy?
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What motor functions are especially affected in Erb’s Palsy?
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The typical appearance of the arm in Erb’s Palsy is commonly referred to as what?
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Where is loss of sensation typically observed in Erb’s Palsy?
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Which nerves are associated with sensory loss in Erb’s Palsy?
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Which characteristic defines the ‘waiter’s tip’ position in Erb’s Palsy?
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What is a common cause of Erb’s Palsy?
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Which nerve root is primarily affected in Klumpke Palsy?
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Which nerves are primarily impacted in Klumpke Palsy?
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What is the typical posture of the hand seen in Klumpke Palsy?
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Which muscles become paralyzed in Klumpke Palsy, resulting in a ‘claw hand’ posture?
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Which loss of function leads to extension at the metacarpophalangeal (MCP) joints and flexion at the interphalangeal (IP) joints?
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In which area of the arm is sensory loss typically experienced in Klumpke Palsy?
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Which mechanism is most commonly associated with the onset of Klumpke Palsy?
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Which statement accurately describes the effects of Klumpke Palsy?
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How many thoracic spinal nerves are there?
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Which thoracic nerves form the intercostal nerves that run between the ribs?
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What is the last thoracic nerve that runs below the twelfth rib known as?
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Which thoracic nerves contribute to the formation of the intercostobrachial nerve?
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What does the anterior division of the thoracic nerves include?
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The posterior division of the upper six thoracic nerves gives rise to what?
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What is the primary function of the intercostal nerves?
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What does the intercostobrachial nerve primarily provide sensory innervation to?
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Which nerve is identified as the last intercostal nerve?
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The intercostal nerves primarily help with what physiological function?
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Which thoracic nerves are specifically involved in sensory innervation to the skin over the upper arm and chest?
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What is the primary role of the anterior divisions of the thoracic nerves?
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Which thoracic nerve branch is associated with connecting to the autonomic nervous system?
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How do the intercostal nerves contribute to sensory information?
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Where do the medial branches of the upper six thoracic nerves primarily penetrate?
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What distinguishes the subcostal nerve from the intercostal nerves?
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What type of nerve fibers do intercostal nerves contain?
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What role do the T6-T12 thoracic nerves play in relation to core strength?
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Which of the following best describes the primary function of the thoracic nerves T6-T12?
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In what manner do the T1-T5 thoracic nerves differ from the T6-T12 nerves concerning core stability?
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Which statement about the T6-T12 thoracic nerves is accurate?
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What is one of the key functions of the thoracic nerves in relation to respiratory mechanics?
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Which muscles are primarily affected by the T1-T5 thoracic nerves?
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What specific function is primarily associated with the T1-T5 thoracic nerves?
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The T6-T12 thoracic nerves primarily affect which muscles?
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What is the primary role of the T6-T12 thoracic nerves?
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Which function is associated with the T6-T12 thoracic nerves?
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The thoracic nerves from T1 to T5 are crucial for which aspect of human function?
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Damage to which section of thoracic nerves would most likely impair coughing?
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The functions of the T1-T5 thoracic nerves include which of the following?
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What is a likely impact of an injury to the T1-T5 thoracic nerves?
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Which aspect of bodily function is most likely to be impaired following a T6-T12 nerve injury?
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Injuries to the T9-T12 thoracic nerves primarily affect which muscle group?
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What is one consequence of injury to the T1 thoracic nerve?
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Which statement is correct regarding T6-T8 thoracic nerve injuries?
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Following an injury to the T1-T5 nerves, which function is least likely to be affected?
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Which of the following injuries would most affect abdominal function?
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Which is a result of injury to T2-T5 thoracic nerves?
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Study Notes
Peripheral Nervous System (PNS)
- The PNS is responsible for transmitting information between the central nervous system (CNS) and the rest of the body.
Spinal Nerves
- Spinal nerves contain both motor and sensory neurons, allowing for communication between the CNS and the body.
- There are 31 pairs of spinal nerves connected to the spinal cord.
- The 31 pairs of nerves are broken down into the following:
- 8 Cervical
- 12 Thoracic
- 5 Lumbar
- 5 Sacral
- Spinal nerves facilitate movement and sensory input throughout the body.
Nervous System Function and Divisions
- Somatic Nervous System: Controls voluntary movements, such as picking up a cup.
- Autonomic Nervous System: Controls involuntary actions such as heartbeat.
- Afferent Nerves: Carry sensory information to the central nervous system (CNS).
- Efferent Nerves: Send signals from the CNS to muscles for movement.
- Sympathetic Nervous System: Prepares the body for "fight or flight" responses by increasing blood pressure, heart rate, and breathing rate.
- Parasympathetic Nervous System: Promotes energy conservation and normal body functions like digestion, often described as the "rest and digest" system.
Nervous System Divisions
- The somatic nervous system controls voluntary movements, such as picking up a cup.
- The autonomic nervous system regulates unconscious bodily functions.
- The central nervous system (CNS) is made up of the brain and spinal cord.
- The sympathetic nervous system prepares the body for "fight or flight" responses - increasing heart rate, blood pressure, and breathing rate.
- The parasympathetic nervous system is responsible for "rest and digest" functions, promoting energy conservation and normal body functions.
Nerve Types
- Afferent nerves carry sensory information from the body to the CNS.
- Efferent nerves send signals from the CNS to muscles for movement.
Autonomic Nervous System Actions
- Involuntary actions, such as heartbeat, are controlled by the autonomic nervous system.
- Emergency situations activate the sympathetic nervous system, leading to increased heart rate, blood pressure, and breathing rate, preparing the body to respond to threats.
Spinal Nerves and Plexuses
-
Cervical Plexus
- Formed by spinal nerves C1 to C4
- Provides nerve connections to the head, neck, and shoulder
-
Brachial Plexus
- Formed by spinal nerves C5 to T1
- Supplies nerves to the chest, shoulders, upper arms, forearms, and hands
-
Lumbar Plexus
- Formed by spinal nerves L1 to L4
- Responsible for nerve connections to the thighs and knees
-
Sacral Plexus
- Formed by spinal nerves L4 to S4
- Provides nerve connections to the pelvis, buttocks, genitals, thighs, calves, and feet
Cervical Vertebrae and Nerves
- There are seven cervical vertebrae in the human body, labeled C1 to C7.
- There are eight cervical nerves, labeled C1 to C8.
- C8 is unique, it emerges below its corresponding vertebra (C7).
Cervical Plexus
- The cervical plexus is formed by the first four cervical nerves (C1 to C4).
- The cervical plexus is responsible for motor and sensory innervation to the neck and parts of the head and shoulders.
- The cervical plexus is divided into two main groups:
- Muscular group: Provides motor control to certain neck muscles.
- Sensory group: Provides sensory input from areas of the neck and skin.
Cervical Vertebrae and Nerves
- There are 7 cervical vertebrae (C1-C7) in the human body.
- There are 8 cervical nerves (C1-C8).
- Cervical nerves C1 to C7 emerge above their corresponding vertebra.
- Cervical nerve C8 emerges below vertebra C7.
Cervical Plexus
- The cervical plexus is formed by the first four cervical nerves (C1-C4).
- It supplies motor and sensory innervation to the neck region.
- The cervical plexus contains two main groups of nerves:
- Muscular (motor) group: controls muscles in the neck.
- Sensory group: responsible for sensation in the neck, scalp, and shoulders.
Suboccipital Nerve (C1)
- The suboccipital nerve (C1) is a motor nerve.
- It supplies muscles at the base of the skull.
Greater Occipital Nerve (C2)
- The greater occipital nerve (C2) is a sensory nerve.
- It provides sensation to the back of the scalp.
Third Occipital Nerve (C3)
- The third occipital nerve (C3) is a sensory nerve.
- It provides sensation to the lower part of the scalp and neck.
Brachial Plexus
- The brachial plexus, formed from the spinal nerves C5-T1, supplies nerves to the chest, shoulders, arms, and hands.
- It is not part of the cervical plexus.
Other Key Points
- The phrenic nerve, essential for breathing, originates from the cervical plexus (C3-C5).
- The radial nerve is part of the brachial plexus and is responsible for extending the elbow and wrist.
- The cervical plexus does not extend to the arms and hands.
- The lumbar plexus is a different plexus responsible for innervating the lower limbs.
Cervical Plexus Motor Branches
- Located deeper than the sensory branches of the cervical plexus.
- Primarily responsible for motor innervation of muscles in the neck, back, and diaphragm.
Phrenic Nerve
- Most notable motor branch of the cervical plexus.
- Originates from cervical spinal nerves C3 to C5.
- Responsible for motor innervation of the diaphragm, enabling diaphragmatic contraction for breathing.
Importance of the Phrenic Nerve
- Crucial for breathing as it controls the diaphragm's contraction.
Sternohyoid muscle
- Innervated by C1, C2, and C3 nerves
- Acts on the hyoid bone, located below the mandible
- Primary function: Depresses the larynx
- Works alongside the sternohyoid muscle to depress the hyoid bone
Ansa Cervicalis
- A loop of nerves that is part of the cervical plexus (C1-C3)
- Translates to "Handle of the neck" in Latin
- Historically referred to as Ansa hypoglossi
- Innervates the sternohyoid, sternothyroid, and omohyoid muscles
Sternothyroid muscle
- Contributes to controlling vocal pitch and volume
Neck muscles
- Innervated by C1 to C3 nerve group, which also innervates muscles involved in tongue movement and swallowing
Cervical Nerve Innervations
- C1-C2: Primarily involved in innervating the prevertebral muscles, which are responsible for neck flexion and stabilization.
- C2-C3: Innervate the sternocleidomastoid muscle, which aids in neck flexion, rotation, and lateral flexion. They also innervate the prevertebral muscles.
- C3-C4: Innervate both the levator scapulae and trapezius muscles. The levator scapulae assists in elevating the scapula, while the trapezius helps with scapular movement, rotation, and stabilization. They also innervate the scalenus medius muscle.
- C4-C5: Play a role in the innervation of the trapezius muscle.
- C4-T1: The trapezius muscle, which supports scapular movement, is primarily innervated by the C4-T1 nerves.
- Scalenus Medius: This muscle assists in lateral neck flexion and elevates the first rib during forced inspiration. It is innervated by the C3-C4 nerves.
- Sternohyoid and Omohyoid: These muscles play a role in depressing the hyoid bone and are innervated by the C1-C3 nerve roots.
- Sternothyroid: Depresses the larynx and is innervated by the C2-C3 nerve roots.
- Scalenus Anterior: Assists in elevating the first rib during forced inspiration and is innervated by the C4-C5 nerve roots.
Muscle Functions
- Trapezius: Its primary function is to move, rotate, and stabilize the scapula.
- Sternocleidomastoid: Facilitates flexion, rotation, and lateral flexion of the neck.
Cervical Plexus
- The cervical plexus is a network of nerves that emerge from the spinal cord in the neck region.
- The sensory branches of the cervical plexus are responsible for supplying sensation to the skin of the neck, upper thorax, scalp, and ear.
- Erb’s point, also known as the nerve point of the neck, is a crucial landmark located at the posterior border of the sternocleidomastoid muscle.
- Sensory branches of the cervical plexus emerge from Erb’s point to innervate the skin of the neck, upper thorax, scalp, and ear.
- The sensory branches that supply the ear also emerge from Erb’s point.
- The sensory branches responsible for supplying the skin of the neck arise from spinal nerves C2-C4.
- The sensory branches of the cervical plexus do not innervate the diaphragm.
Cervical Plexus Sensory Innervation
- The greater auricular nerve (C2, C3) provides sensation to the external ear and the parotid gland.
- The transverse cervical nerve (C2, C3) supplies sensation to the anterior neck.
- The lesser occipital nerve (C2) provides sensory input to the posterosuperior scalp.
- The supraclavicular nerves (C3, C4) supply sensation to the supraclavicular fossa, upper thoracic region, and sternoclavicular joint.
- The greater auricular nerve originates from cervical nerves C2 and C3.
- The supraclavicular nerves provide sensory input to the supraclavicular fossa and sternoclavicular joint.
Cervical Plexus Sensory Innervation
- Greater Auricular Nerve (C2, C3): Provides sensation to the parotid gland, external ear, and skin over the mastoid process.
- Lesser Occipital Nerve (C2): Supplies sensory innervation to the posterosuperior scalp.
- Transverse Cervical Nerve (C2, C3): Provides sensation to the anterior neck region.
- Supraclavicular Nerves (C3, C4): Involved in sensory innervation of the supraclavicular fossa, upper thoracic region, and the sternoclavicular joint.
Brachial Plexus Overview
- The brachial plexus is a network of nerves that originates from the spinal cord and supplies the upper limb.
- It emerges from spinal nerves C5-T1.
- The plexus is responsible for providing sensory and motor innervation to the upper limb.
- It passes through the axilla (armpit) to reach the upper extremities.
- The brachial plexus is divided into five main parts: roots, trunks, divisions, cords, and branches.
Parts of the Brachial Plexus
- Roots: Formed by spinal nerves C5-T1
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Trunks: Three trunks are formed by the roots.
- Superior trunk: C5-C6 roots
- Middle trunk: C7 root
- Inferior trunk: C8-T1 roots
- Divisions: Each trunk divides into anterior and posterior divisions.
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Cords: The divisions converge to form three cords:
- Lateral cord: Anterior divisions of the superior and middle trunks
- Posterior cord: Posterior divisions of all three trunks
- Medial cord: Anterior division of the inferior trunk
- Branches: The cords give rise to numerous branches which innervate specific muscles and structures of the upper limb.
Mnemonic for Ordering
- "Read That Damn Cadaver Book" can help remember the order: Roots, Trunks, Divisions, Cords, Branches
Brachial Plexus Location
- The brachial plexus starts at the neck, passes through the axilla (armpit), and descends into the upper limb.
Key Functions
- Sensory: Receives sensory information from the skin and structures of the upper limb.
- Motor: Controls the movement of muscles in the upper limb.
Brachial Plexus Roots
- The brachial plexus is formed by the anterior rami of spinal nerves C5-T1.
- These roots exit the spinal cord through the intervertebral foramina.
- After exiting, the roots divide into anterior and posterior rami.
- The anterior rami are responsible for forming the brachial plexus.
- The posterior rami innervate the muscles and skin of the back.
Brachial Plexus Pathway
- The brachial plexus roots exit the spinal cord through the intervertebral foramina.
- They then divide into anterior and posterior rami.
- The anterior rami are responsible for forming the brachial plexus.
- The posterior rami innervate the muscles and skin of the back.
Function of the Brachial Plexus
- The brachial plexus provides sensory and motor innervation to the upper limb.
- It is responsible for controlling the movement of the arm, hand, and fingers.
- It also provides sensory input from the skin and muscles of the upper limb.
Brachial Plexus Trunks & Divisions
- The brachial plexus originates from the ventral rami of spinal nerves C5-T1.
- The roots of the brachial plexus converge to form three trunks:
- Superior trunk: Formed by the convergence of C5 and C6 roots.
- Middle trunk: Formed by the C7 root.
- Inferior trunk: Formed by the convergence of C8 and T1 roots.
- Each trunk then divides into two divisions:
- Anterior division: Primarily innervates the flexor muscles of the upper limb.
- Posterior division: Primarily innervates the extensor muscles of the upper limb.
- The divisions of the trunks then converge to form three cords which ultimately give rise to the terminal branches of the brachial plexus.
- The divisions of the trunks pass through the axilla (armpit area).
Brachial Plexus Cords
- The brachial plexus is a network of nerves that arise from the spinal cord and supply the upper limb.
- The brachial plexus is formed by the ventral rami of spinal nerves C5-T1.
- The brachial plexus is divided into:
- Roots
- Trunks
- Divisions
- Cords
- Branches
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Three main cords are formed in the axilla by the divisions of the brachial plexus trunks:
- Lateral cord - formed by the anterior divisions of the superior and middle trunks
- Posterior cord - formed by the posterior divisions of the superior, middle, and inferior trunks
- Medial cord - formed solely by the anterior division of the inferior trunk
- The cords of the brachial plexus are named based on their position relative to the axillary artery.
- The lateral cord is positioned lateral to the axillary artery.
- The medial cord is positioned medial to the axillary artery.
- The posterior cord is positioned posterior to the axillary artery.
- The posterior cord contributes to the formation of the radial nerve.
Brachial Plexus and Nerves
- The brachial plexus is a network of nerves that innervates the upper limb.
- It is formed from the ventral rami of spinal nerves C5-T1.
- The brachial plexus is divided into five major branches: the axillary, musculocutaneous, median, radial, and ulnar nerves.
Axillary Nerve (C5, C6):
- Motor function: Innervates the deltoid and teres minor muscles.
- Sensory function: Provides sensation to the inferior region of the deltoid, also known as the "regimental badge" area.
Musculocutaneous Nerve (C5-C7):
- Motor function: Innervates the biceps brachii, brachialis, and coracobrachialis muscles, primarily responsible for elbow flexion.
- Sensory function: Provides sensation to the lateral half of the anterior forearm and a small portion of the posterior forearm.
Median Nerve (C5-T1):
- Motor function: Innervates most of the flexor muscles in the forearm, including the pronators, and the thenar muscles of the hand.
- Sensory function: Provides sensation to the lateral 3½ fingers on the palmar surface of the hand.
Radial Nerve (C5-T1):
- Motor function: Innervates the triceps brachii, brachioradialis, and extensor muscles of the wrist and fingers.
- Sensory function: Provides sensation to the posterior aspect of the arm and forearm, as well as the posterolateral hand.
Ulnar Nerve (C7-T1):
- Motor function: Innervates the flexor carpi ulnaris, most of the intrinsic muscles of the hand, and some finger flexors.
- Sensory function: Provides sensation to the medial 1½ fingers (including associated palm area) on both the anterior and posterior surfaces of these fingers.
Brachial Plexus and Innervation
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Median Nerve:
- Innervates thenar muscles, index, and middle fingers
- Involved in opposing the thumb
- Provides sensory innervation to lateral palm and 3 1/2 fingers on the palmar side
-
Musculocutaneous Nerve:
- Responsible for elbow flexion
- Originates from C5, C6, and C7 roots
-
Radial Nerve:
- Provides sensory innervation to posterolateral aspect of the hand
- Innervates the triceps brachii muscle
- Responsible for wrist extension
-
Axillary Nerve:
- Provides sensory innervation to the inferior deltoid ("regimental badge" area)
- Innervates deltoid and teres minor muscles
-
Ulnar Nerve:
- Innervates most hand muscles, excluding thenar muscles
- Provides sensory innervation to medial 1 1/2 fingers and associated palm area
- Necessary for finger abduction and adduction
-
Nerve Damage and Symptoms:
- Median Nerve Damage: Difficulty opposing thumb
- Musculocutaneous Nerve Damage: Weakness in elbow flexion
- Radial Nerve Damage: Weakness in wrist extension, sensory loss in dorsal hand
- Axillary Nerve Damage: Sensory loss in the deltoid region
- Ulnar Nerve Damage: Weakness in hand, sensory loss in medial fingers
Brachial Plexus Formation
- The brachial plexus is a network of nerves that arises from the ventral rami of spinal nerves C5-T1.
- The roots (C5-T1) merge to form three trunks: superior, middle, and inferior.
- The superior trunk is formed by the combination of C5 and C6 roots.
- The middle trunk is formed by the single C7 root.
- The inferior trunk is formed by the combination of C8 and T1 roots.
- Each trunk then splits into an anterior and posterior division, resulting in six divisions.
- The anterior divisions of the superior and middle trunks combine to form the lateral cord.
- The posterior divisions of all three trunks combine to form the posterior cord.
- The anterior division of the inferior trunk forms the medial cord.
Major Nerves of the Brachial Plexus
- The lateral cord gives rise to the musculocutaneous nerve.
- The medial cord gives rise to the ulnar nerve.
- The posterior cord gives rise to the axillary and radial nerves.
- The median nerve is a combination of branches from both the lateral and medial cords.
Key Innervations
- The musculocutaneous nerve innervates the anterior compartment muscles of the arm and provides sensory innervation to the lateral forearm.
- The axillary nerve innervates the deltoid and teres minor muscles and provides sensory innervation to the skin over the deltoid and lateral shoulder.
- The radial nerve innervates the posterior compartment muscles of the arm and forearm and provides sensory innervation to the posterior arm and forearm.
- The median nerve innervates the anterior compartment muscles of the forearm and provides sensory innervation to the palmar aspect of the thumb, index, middle, and radial half of the ring finger.
- The ulnar nerve innervates the flexor carpi ulnaris and medial half of the flexor digitorum profundus muscles in the forearm, as well as the intrinsic hand muscles, and provides sensory innervation to the palmar and dorsal aspects of the little finger and medial half of the ring finger.
Location and Relationship to Axillary Artery
- The cords of the brachial plexus are named based on their position relative to the axillary artery.
- The lateral cord is located lateral to the axillary artery.
- The medial cord is located medial to the axillary artery.
- The posterior cord is located posterior to the axillary artery.
Erb's Palsy
- Nerve Roots Affected: Erb's Palsy involves injury to the C5 and C6 nerve roots of the brachial plexus.
- Muscles Affected: The muscles typically paralyzed in Erb's Palsy include supraspinatus, teres minor, and subclavius, but not the triceps brachii.
- Motor Function Impairment: Individuals with Erb's Palsy experience difficulty with abduction at the shoulder, lateral rotation of the arm, supination of the forearm, and flexion at the shoulder.
- Characteristic Appearance: The characteristic arm position in Erb's Palsy is known as the "waiter's tip" position, which is marked by medial rotation of the arm, pronation of the forearm, and weak wrist flexion.
- Sensory Loss: Sensory loss in Erb's Palsy typically occurs down the lateral aspect of the arm, affecting the axillary and musculocutaneous nerves.
- Common Cause: Erb's Palsy is frequently caused by excessive stretching or trauma to the shoulder during birth or due to shoulder trauma in adults.
- Muscle Involved in Supination: The biceps brachii muscle, responsible for supination of the forearm, is affected in Erb's Palsy.
- Shoulder Abduction: The deltoid muscle, which plays a crucial role in shoulder abduction, is paralyzed in Erb's Palsy, significantly impacting this movement.
Klumpke Palsy
- Nerve roots affected: Primarily T1, but C8 can also be involved.
- Nerves affected: Ulnar and median nerves.
- Hand posture: Characteristic "claw hand" posture.
- Cause of claw hand: Paralysis of all intrinsic hand muscles.
- Muscle responsible for the claw hand: Lumbrical muscles.
- Function of the lumbrical muscles: Flexion at the metacarpophalangeal (MCP) joints and extension at the interphalangeal (IP) joints of the fingers.
- Affected muscle groups: Intrinsic muscles of the hand.
- Sensory loss: Medial side of the arm.
- Common cause: Excessive abduction of the arm, such as catching oneself on a branch during a fall.
- Key fact: Klumpke Palsy leads to significant impairment of hand function.
- Mechanism of claw hand: Loss of lumbrical function leads to unopposed action of finger extensor muscles.
Overview of Thoracic Nerves
- There are 12 thoracic spinal nerves (T1-T12) located in the thoracic region of the spinal cord.
- Each thoracic nerve divides into anterior and posterior divisions.
Thoracic Nerves and Intercostal Nerves
- Thoracic nerves T1-T11 form the intercostal nerves which run between the ribs, providing innervation to the thoracic wall.
- The last thoracic nerve, T12, is called the subcostal nerve and runs below the twelfth rib.
Intercostobrachial Nerve
- The intercostobrachial nerve is formed by branches of the second and third thoracic nerves (T2 and T3).
- Provides sensory innervation to the upper arm and chest.
Anterior Thoracic Nerve Divisions
- The anterior divisions of the thoracic nerves primarily form the intercostal nerves (T1-T11) and the subcostal nerve (T12).
Posterior Thoracic Nerve Divisions
- The posterior divisions of the upper six thoracic nerves (T1-T6) have medial branches that pierce the rhomboid and trapezius muscles, providing sensory innervation to the skin of the back.
Functions of Thoracic Nerves
- Intercostal Nerves: innervate the intercostal muscles, aiding in respiration, and provide sensory innervation to the skin of the chest.
- Subcostal Nerve: provides sensory innervation to the abdominal region.
- Medial Branches: (Upper six thoracic nerves) provide sensory innervation to the skin of the back.
- Intercostobrachial Nerve: provides sensory innervation to the upper arm and chest.
Autonomic Nervous System (ANS) Connection
- Thoracic nerves connect to the paravertebral ganglia, which are part of the sympathetic nervous system of the ANS.
Thoracic Nerve Function
-
T1-T5 Thoracic Nerves: Primarily responsible for controlling the muscles of the upper chest, mid-back, and abdomen. They play a crucial role in respiratory movements by controlling the rib cage, lungs, and diaphragm.
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T6-T12 Thoracic Nerves: Primarily involved in supporting abdominal and back muscles for core strength and posture, contributing to balance and core stability. They also aid in protective respiratory reflexes like coughing and expelling foreign bodies from the airways.
Key Points
- T1-T5: Contribute to upper chest stability and respiratory movements
- T6-T12: Essential for core stability, posture, and protective respiratory reflexes
- Damage to T6-T12: Can impair coughing and other protective respiratory reflexes
- T1-T5: Do not directly innervate the diaphragm, but contribute to its function through rib cage control
- T6-T12: Do not directly control arm movements
Thoracic Nerve Injuries and their Effects
- Injury to T1-T5 thoracic nerves results in paraplegia (paralysis of the lower body).
- T1-T5 nerve injuries do not affect hand and finger movement.
- T1-T5 nerve injuries impair the function of abdominal muscles and the lower back.
- Injury to T6-T12 thoracic nerves may lead to little or no control over the bowel and bladder.
- T9-T12 thoracic nerve injuries affect abdominal muscles.
- T1 thoracic nerve injury can affect hands and fingers.
- T6-T8 thoracic nerve injury leads to impaired chest and abdominal muscle function.
- T1-T5 nerve injuries do not affect arm and hand function.
- T6-T12 nerve injuries result in impaired control over abdominal muscles and some bowel/bladder functions.
- T2-T5 thoracic nerve injuries primarily affect chest muscles.
- T1-T5 injury results in paraplegia, but arm and hand function is retained.
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Description
Explore the structure and function of the Peripheral Nervous System, focusing on spinal nerves and their crucial role in communication between the central nervous system and the body. Learn about the 31 pairs of spinal nerves and their classifications, including cervical, thoracic, lumbar, and sacral divisions.