A & P II Exam 1

brachial plexus location

extends down & laterally thru armpit

brachial plexus function

innervates entire upper extremity

roots

formed by ventral rami of C5-T1

• “branch off”

trunks

pass over 1st rib & deep to clavicle

divisions

• anterior supply to anterior upper extremities

• posterior supply to posterior upper extremities

cords

named according to relationship w/ axillary artery

branches

individual nerves that branch from cords

• nerves innervate the muscles they pass thru

axillary nerve pathway

C5-C6

• winds posteriorly to surgical neck of humerus & pierces deltoids

axillary nerve (muscle)

innervates deltoid & teres minor

axillary nerve (sensory)

innervates skin around shoulder

radial nerve pathway

C5-T1

• spirals down deep to triceps, crossing over posterior arm

• ends up laterally anterior to lateral epicondyle & deep to brachioradialis, branches into deep & superficial branches

  • deep branch pierces supinater to extensors in forearm

  • superficial branch runs w/ radial artery deep to brachioradialis

radial nerve (muscle)

innervates muscles that extend forearm, wrists, digits, & supinator

radial nerve (sensory)

innervates skin on posterior arm, extensor, forearm, radial 2/3 of hand & back of first 3 1/2

ulnar nerve pathway

C8-T1

• runs along medial arm

• @ elbow between olecranon & medial epicondyle

• travels deep to flexor carpi ulnaris

• over flexor retinaculum

• into hand

ulnar nerve (muscle)

branches to flexor carpi ulnaris, ulnar ½ of flexor digitorum profundus, & hypothenar muscles

hypothenar muscles

under pinky

• meaty part of palm

ulnar nerve (sensory)

innervates skin on ulnar forearm, ulnar 1/3 of hand, pinky, & ½ of ring finger

median nerve pathway

C5-T1

• travels w/ brachial artery on medial side of arm

• crosses cubital fossa on medial side of biceps tendon

• runs through middle of forearm deep to flexor digitorum superficialis

• runs thru carpal tunnel into hand

median nerve (muscle)

branches to pronator teres & flexors of wrist & digits (except FCU & ulnar ½ of FDP); innervates thenar muscles

median nerve (sensory)

innervates skin of radial 2/3 of palm & first 3 ½ digits, including nail beds

thenar muscles

under thumb

• meaty part of palm

musculocutaneous nerve pathway

C5-C7

• passes laterally between biceps & brachialis

• crosses cubital fossa on lateral side of biceps tendon

• becomes a cutaneous nerve on radial forearm

cutaneous nerve

just under skin

musculocutaneous nerve (muscle)

innervates biceps brachii, brachialis, & coracobrachialis

musculocutaneous nerve (sensory)

innervates skin on radial edge of forearm

cutaenous distribution

diagrams showing areas of skin supplied by certain nerves

sensory map

skin regions supplied by certain nerves

dermatomes

skin regions supplied by spinal cord levels/roots

nerve injury

complete severing of a nerve inhibits all motor & sensory info

complete sever leads to…

paralysis

partial sever leads to…

paresis

extent of injury symptoms depends on…

extent of damage

the more distal the injury…

the lesser the symptoms

how is axillary nerve usually injured?

shoulder dislocation or humerus fracture

axillary nerve injury symptoms

• paralysis of deltoid & teres minor

• partial paralysis of shoulder (abduction)

• sensory loss in shoulder

ulnar nerve injury symptoms

• paralysis of flexor carpi ulnaris, ½ of flexor digitorum profundus, & hypothenar

• weakened flexion in wrist, ring, and pinky (claw hand)

• sensory loss on ulnar side of forearm & hand, partial ring, and pinky

radial nerve injury symptoms

• wrist drop

• weak finger & elbow extension

• weak forearm supination

• sensory loss of posterior arm & forearm, radial thumb, index & middle

median nerve injury symptoms

• difficulty pinching, gripping, & making fist

• weak flexion of wrist, index & middle

• weak forearm pronation

• sensory loss of palmar thumb, index & middle, lateral ½ of ring

musculocutaneous nerve injury symptoms

• weak elbow flexion

• weak forearm supination

• reduced lifting strength

• sensory loss of lateral forearm

klumpke’s paralysis

birth paralysis affects mainly C8, T1, & inferior trunk

• loss of ulnar supply

klumpke’s paralysis symptoms

• sensory loss of medial arm, forearm & wrist

• paralysis of hypothenar, flexor digitorum profundus, & flexor digitorum superficialis

• claw hand

lumbar plexus & branches

• L1-L4

• obturator nerve & femoral nerve

obturator nerve

(L2-L4)

muscles of medial compartment of thigh & its skin

femoral nerve

(L2-L4)

muscles of anterior compartment of thigh & its skin

lumbar plexus injury symptoms

lose ability to flex and extend leg

sacral plexus & branches

• L4-L5; S1-S4

• sciatic nerve breaks into

  • tibial nerve

  • common fibular nerve

sciatic nerve

(L4-S3)

gives branches to muscles of posterior compartment of thigh

tibial nerve

(L4-S3)

• continues through popliteal fossa

• branches to muscles of posterior compartment of leg

common fibular nerve branches into…

(L4-S2)

• superficial fibular nerve

• deep fibular nerve

superficial fibular nerve

(L4-S2)

supplies muscles of lateral compartment of leg

deep fibular nerve

(L4-S2)

supplies anterior compartment of leg

sciatic nerve injury symptoms

• sensory loss below knee

• loss of dorsiflexion, much of leg below knee is useless

• foot drop

tibial nerve injury symptoms

• sensory loss of sole of foot, heel & toes

• no plantar flexion, weak toe flexion & foot inversion

superficial fibular nerve injury symptoms

• sensory loss of dorsum of foot, anterolateral lower leg

• weak foot eversion

deep fibular nerve injury symptoms

• sensory loss between big toe & 2nd toe

• loss of dorsiflexion, toe extension

• toe drag when walking

autonomic nervous system (ANS)

• involuntary control

• unconscious visceral activity

• entirely motor (general visceral efferent fibers)

• divides into sympathetic & parasympathetic

examples of unconscious visceral activity

• peristalsis & mixing

• heart rate

• blood pressure

• gland secretion

• pupil & blood vessel dilation

• sexual arousal

• urination & defecation

dual innervation

organs receive supply from both sympathetic & parasympathetic

• often have opposing actions

all autonomic nerves maintain some level of activity called…

autonomic tone

• homeostatic balance between the 2 allow for range of control in organ activity

autonomic patthways

consist of

• 2 efferent neurons that synapse in a ganglion

• reflex centers in brain stem

• regulating centers in hypothalamus

preganglionic neuron

cell bodies in brain stem of spinal cord → axons extend to autonomic ganglia → synapse with ganglionic neuron

ganglionic neuron

cell bodies in ganglion → axons extend to effector/target organ

*entirely outside the CNS

sympathetic pathways

respond to crisis, “fight-or-flight”, typically widespread through body

preganglionic cell bodies (S)

found in thoracic & lumbar segments of spinal cord (T1-L2)

• short fibers

• release ACh

ganglia (S)

sympathetic trunk located along either side of vertebral column

cholinergic

release ACh

postganglionic cell bodies (S)

• long fibers

• release norepinephrine

adrenergic

release norepinephrine

parasympathetic pathways

“rest & digest”

• narrow impact with more specific effects

preganglionic cell bodies (PS)

in brain stem (S2-S4)

• long fibers

• release ACh

ganglia (PS)

terminal ganglia located near effector organ

postganglionic cell bodies (PS)

• short fibers

• release ACh

second messenger system steps

1. neurotransmitters bind to receptor

2. activates different types of G protein

3. coupled to different types of enzymes

4. production of second messenger

what are the 2 types of receptors @ cholinergic synapses?

nicotinic & muscarinic

nicotinic receptors

• always excitatory

• open chemically-gated Na+ channels

• ACh receptor of NMJ

• @ ALL pre-topostganglionic synapses

• nicotine acts as “mimic”

muscarinic receptors

• in parasympathetic postganglionic-to-effector synapse

• G protein coupled

• excitatory or inhibitory depending on activation of specific enzymes

what are the 2 classes of adrenergic synapses?

alpha & beta

alpha synapses

accept norepinephrine & epinephrine

beta synapses

stimulated by epinephrine

alpha-1

protein activation increases Ca release from sarcoplasmic reticulum into cytosol

• result is usually excitatory

• ex: vasoconstriction & sphincter closing

alpha-2

G protein activation decreases cAMP

• result is usually inhibitory

• ex: decreased motility in GI tract

beta-1

stimulates skeletal & cardiac muscle

beta-2

inhibits smooth muscle of respiratory & digestive tracts

• causes relaxation

types of messenger (nervous vs. endocrine)

NS: neurotransmitters (chemical/electrical signals)

ES: hormones

delivery (nervous vs. endocrine)

NS: @ synapse

ES: in bloodstream

speed of response (nervous vs. endocrine)

NS: milliseconds

ES: minutes/hours

target of response (nervous vs. endocrine)

NS: small & more specific (fewer target cells)

ES: large & more general (more target cells)

how are nervous & endocrine systems connected?

one can stimulate the other

2 types of glands in endocrine system

exocrine & endocrine

exocrine glands

secrete their products into duct system

ex: salivary glands, seminal vesicle, sweat & sebaceous glands

endocrine glands

secrete their products into extracellular space around cells→diffuse into capillaries→carried to other organs

what are the 3 classes of chemistry hormones

• amino acid derivatives

• peptides

• lipid derivatives

amino acid derivatives

modified amino acid (simplest structure)

ex: norepinephrine & epinephrine

peptides

chains of amino acids

ex: oxytocin & insulin

lipid derivatives

steroids or steroids produced from cholesterol

ex: sex hormones & aldosterone

what do ALL hormones do?

help maintain homeostasis by changing speed of cell activities

target cells

respond to hormone

hormones are specific, which means…

not ALL cells respond to ALL hormones

what do endocrine cells respond to when homeostasis is upset?

• nerve stimulation

• other hormones

• changes in composition of extracellular fluid

how do they respond when homeostasis is upset?

release hormones

→negative feedback system