muscles and nerves Flashcards
muscle functions
movement (skeleton, intestines, heart and blood vessels) static support heat production
what are the 3 types of muscle
skeletal, cardiac and smooth
skeletal muscle
attached to skeleton
locomotion
voluntary
cardiac muscle
heart
blood circulation
involuntary
smooth muscle
walls of vessels and organs
move substances and restrict flow
involuntary
skeletal muscle
long and slender fibres
multinucleate, peripherally located, long and elongated
many mitochondria
cross striations
arranged into fascicles
cardiac muscle
cross striated by involuntary
single rounded nu
branched cells
region where the ends of the cells are connected = intercalated disc
intercalated disc contains gap junctions - allow muscle cells to be electrically coupled to beat in synchrony
smooth muscle
devoid of cross striations
shorter fibre length
centrally situated, cigar shaped nu
how does bone attach to muscle
via a tendon
fasicle
one bundle of muscle fibres surrounded by a layer or connective tissue
tendons
dense connective tissues (collagen)
dont shorten
transfer the force to the bone to which it attaches
can alter force direction
some muscles share a common tendon, allowing them to work together
muscles passing over a joint will …
act on that joint
some pass over more than one joint
muscles with multiple function
e.g. deltoid
flexion, extension and abduction at the shoulder joint, different parts contract for different movement
muscles maintaining posture
oppose gravity
e.g. erector spinae
movement and static support function
muscles working as part of a system
e. g. elbow joint: triceps and biceps working in opposition
e. .g shoulder joint: stabilised by joint action of rotator cuff muscle, muscles work together fork the same action
e. g. hand: forearm muscles for powerful grip and intrinsic hand muscles for position
muscle compartments in the limbs
arm: flexor (anterior compartment) and extensor (posterior compartment)
forearm: flexor - pronator compartment and extensor - supinator compartment
nerve supply of muscles
muscles of the same compartment are usuall supplied by the same nerve
e.g. radial nerve supplies all extensors in the upper limb
structural divisions of the nervous system
CNS (brain and spinal cord)
PNS (12 cranial and 31 spinal nerves)
functional divisions of the nervous system
somatic
autonomic (sympathetic and parasympathetic)
enteric
functional types of nerve fibres
sensory - afferent neurons
motor - efferent neurons (cause an effect)
dorsal root contains
sensory fibres only
(posterior)
ventral root contains
motor fibres only
(anterior)
rami contain
both sensory and motor fibres
dorsal rami = mixed to erector spinae
ventral rami = mixed to all other motor regions
somatic pathway
sensory nerves detect stimulus, travel towards spinal cord via sensory fibres in the dorsal root, motor fibres exit from the ventral root, muscles contract
MOTOR FIBRES DON’T SYNAPSE
Autonomic pathways
motor fibres synapse in the sympathetic ganglion
sympathetic trunk
formed by the sympathetic ganglia
this is where most sympathetic motor fibres synapse (except fibres to the abdominopelvic viscera)
paravertebral
differences between symapthetic and parasympathetic
location of outflow from CNS: S - thoracolumbar, PS - craniosacral
location of ganglia: S - sympathetic trunk and additional for abdominopelvic region, PS - sit close to target organ
transmitters and receptors used
what is a motor unit
one motor neurone supplying a varying number of muscle fibres
this leads to variation in the amount of control over the different muscle types, one nerve –> fewer fibres –> higher levels of control
myotome
area of mscle supplied by one spinal nerve
dermatome
area of skin supplied by one spinal nerve
what is the difference between dermatomes and cutaneous nerve maps
dermatome map = shows the areas supplied by a single spinal nerve
cutaneous nerve map = show the areas of skin supplied by a single cutaneous nerve, cutaneous nerves get fibres from multiple different spinal nerves
what is a nerve
combination of fibres from different spinal nerves
what are the different types of spinal nerves
8 cervical (C1-8)
12 thoracic (T1-12)
5 lumbar (L1-5)
5 sacral (S1-5)
1 coccygeal (Co1)
how are there 8 cervical nerves but only 7 cervical vertebrae
the C1 nerve exits between the skull and the atlas
C8 exits between C7 and T1
what is the difference between a root and a ramus
rootlets extend out of the spinal cord medially and combine to form roots
roots combine to form the spinal nerve and then split apart to form rami
what do the dorsal rami innervate
deep muscles of the back for motor control
also a horizontal strip of skin for sensory input
what do the ventral rami innervate
in the thoracic region they are known as the intercostal nerves
run deep to the ribs and innervate intercostal muscles
provide sensory input for the overlying horizontal strips of skin as well as the abdominal wall muscles (motor) and skin (sensory)
nerve plexuses
network of nerves that mostly serve the limbs
they are a network of nerves that come together and then redistribute themselves with a different distribution of nerves into the limbs
made from the rest of the ventral ramus
each end of the plexus contains fibres from several spinal nerves
fibres from each ventral ramus travel along different routes so limb muscle recieves innervation from more than one spinal nerve
what are the 4 nerve plexuses
cervical, brachial, lumbar and sacral
cervical plexus
located underneath the sternocleidomastoid muscle (C1-C4)
Most branches innervate the skin of neck and deep neck muscles
phrenic nerve (C3,4,5) innervates the top of the diaphragm
if phrenic nerves are cut of the spinal cord is severed above C3, breathing stops
axial muscles
any muscle attaching to the trunk only
appendicular muscle
muscles attaching to the appendicular skeleton (limbs)
can be attached distally or proximally
studying muscles in compartments
- attachements (bone)
- actions (e.g. flexion/extension)
- innervation (anatomical and clinical persepective)
attachments
origin: superior, proximal or medial attachment
insertion: inferior, distal or lateral attachment
e. g. brachioradialis
origin = humerus
insertion = radius
action = elbow flexion
trapezius
origin: superior nuchal line, occipital bone, the ligamentum nuchae, and the spinous processes, supraspinous ligament (C7-T12)
insertion: scapula, acromion, clavicle
latissimus dorsi
origin: spinous processes and supraspinous ligament (T6-L5), thoracolumbar fascia, sacral and iliac crest, ribs
insertion: humerus
action: adduction, internal rotation, extension of humerus
flexion
to bend a joint by pulling the bones closer together
e.g. bending the arm up
extension
to unbend or lengthen a joint by pulling bones further apart
e.g. lengthen the arm out straight
5 rules of skeletal muscle activity
- all skeletal muscles cross at least one joint
- the bulk of a skeletal muscle lies proximal to the joint crosses
- all skeletal muscles have at least 2 attachments (origin and insertion)
- skeletal muscles can only pull, they never push
- during contractino, a skeletal muscle insertion moves toward the origin
innervation of appendicular muscles
supplied by nerve plexuses
- nerves containing mixed fibres from more than one spinal nerve
innervation of axial muscles
supplied segmentally
- by separate nerves that haven’t mixed with others
Hilton’s law
the nerve supplying the muscles extending directily across and acting at a given joint also innervate the joint and the overlying skin
segmental innervation of the trunk
individual nerves supply each trunk segment separately
cutaneous nerves here supply the skin individually
muscle (fascial compartments)
appendicular muscles are arranged in compartments and are formed by tough connective tissue septa)
muscles in a compartment:
- perform similar functions
- attach across the same joints
- perform similar actions
- are supplied by the same nerve
compartment syndrome
acute medical problem following injury or surgery
increased pressure in a compartment
ligament
attaches bone to bone, strengthens the joint
grey matter
white matter
grey = cell bodies
white = axons
trunk dermatomes
T2 = sternomanubrial joint (T4 vertebrae)
T4 = nipples
T10 = umbilicus
L1 = groin
what is the advantage of having nerve plexuses
control of skeletal muscle is shared by different axons that originate in adjacent levels of the spinal cord
damage to a single level of the spinal cord is less likely to result in paralysis of a muscle innervated by nerves from that plexus
densley stained nu
dendrites coming in
axons leaving
very granular
