Physiology Flashcards
what are muscle striations formed from
alternating dark and light filaments
what are the dark filamens
thick myosin
what are the light filaments
thin actin
what is contained in the sarcomere
actin and myosin
are gap junctions present in skeletal muscle
no
define motor unit
a single alpha motor neurone and the fibres it innervates
why would a motor neurone contain few fibres per motor unit
when precision is more important than power
give an example of a muscle where there are few fibres per motor unit
extra-ocular muscles
give an example of a muscle where there are many fibres per motor unit
quads
give the structure of muscle
Muscle -> muscle fibre -> myofibril -> sarcomere
how big is a muscle fibre
1 cell
what is a myofibril
intracellular contractile structure
what is a functional unit
smallest component that can perform all an organ’s functions
what is the functional unit of skeletal muscle
sarcomere
names of the zones within a sarcomere
A band
H zone
M line
I band
what is the A band
thin filament overlapping both ends of thick filaments
what is the H zone
lighter area within A-band where thin filaments don’t reach
what is the M line
vertically down middle of A band in centre of H zone
what is the I band
remaining portion of thin filaments
how to histologically tell apart muscle fibre types
succinate dehydrogenase stain
names of skeletal muscle fibre types
Slow oxidative I
Fast oxidative IIa
Fast glycolytic IIx
features of type I skeletal muscle
resistant, oxidative metabolism, > mitochondria
when is type I skeletal muscle used
long low aerobic activities - walking, posture
features of type IIa skeletal muscle
intermediate twitch, aerobic & anaerobic metabolism, fatigue resistant
when is type IIa skeletal muscle used
long moderate work - jogging
features of type IIx skeletal muscle
fast twitch, anaerobic metabolism, fatigue easy, < mitochondria, greater force, white fibre
when is type IIx skeletal muscle used
short term high intensity e.g. jumping
what does skeletal muscle look like on histology
unbranched nuclei under sarcolemma, multinucleate (syncytium), long cylindrical fibres
where are the nuclei located in the cell in skeletal muscle? how does the differ from cardiac muscle?
peripherally, in centre in cardiac
define fascicle
bundle of muscle fibres
define epimysium
connective tissue that surrounds muscle
define perimysium
connective tissue around a single fascicle
define endomysium
connective tissue around a single muscle fibre
sarcomes entend from …
1 Z line to the next
sliding filament theory; where is Ca released from
sarcoplasmic reticulum lateral sac
sliding filament theory; what does Ca bind to
troponin on actin
sliding filament theory; what is the power stroke
tropomyosin moved aside; pulls thin filament inward during contraction to reveal cross bridge
sliding filament theory; what happens when no action potential
ATP pumps Ca++ to sarcoplasmic reticulum
sliding filament theory; what is required for AP
ATP
sliding filament theory; what happens when muscle muscle
no cross bridge binding, actin physically covered by troponin tropomyosin complex
what factors influence muscle tension
no. of fibres contracting (motor unit recruitment >1 unit contracting, prevents fatigue)
tension developed by each fibre (stimulation freq & fibre length/thickness)
what happens if repetitive fast stimulation
twitches summate
what happens in tetanus
sustained contraction; stimulated so rapidly muscle doesn’t relax between stimuli stronger contraction
why doesn’t tetanus happen in cardiac muscle
long refractory period
when is maximum tension in skeletal muscle
at optimum (resting) muscle length before contraction
what movements are done by isotonic contraction
movement/moving objects
what movements are done by isometric contraction
supporting objects/posture
what happens in isotonic contraction
tension constant as muscle length changes
what happens in isometric contraction
tension develops at constant muscle length
are there different types of fibre in each motor unit
nope
what differences are there between skeletal muscle fibres
enzymatic ATP synthesis pathways, fatigue resistance, myosin ATPase activity
what does myosin ATPase activity affect
muscle contraction speed
where does fast ATP supply for muscle contraction come from
creatine phosphate to ADP
where does ATP supply for muscle contraction come from when O2 present
oxidative phosphorylation
where does ATP supply for muscle contraction come from when O2 not present
glycolysis
what is a reflex action
stereotyped response to a specific stimulus
what type of feedback is the stretch reflex
ve feedback mechanism
when is the stretch reflex used
maintains posture
what is the stretch reflex
simplest monosynaptic spinal reflex resisting passive change in muscle length
what is a muscle spindle
sensory stretch reflex receptors
what is a muscle spindle formed of
specialised intrafusal fibres
nerve supply to muscle spindle
have own efferent nerve supply, gamma motor neurones
where do muscle spindles synpase
in spinal cord with alpha motor neurons
how can you test the muscle spindle
patellar tendon tap
what type of neuro-receptor is involved in synaptic transmission of skeletal muscles
nicotinic ACh GPCR
what terminates synaptic transmission in skeletal muscle
ACh hydrolysis by AChE
when does the e.p.p. occur and what effect does this have
when na influx > k efflux causes depolarisation
when is an AP stimulated in skeletal muscle
when e.p.p. is > threshold
what is the m.e.p.p
response to 1 quantum of neurotransmitter
what is haemopoiesis and where does it take place
BC production in bone
what is an osteocyte
mature osteoblast bone cell
where are osteocytes
in canaliculi/lacunae in bone matrix
what is an osteoblast
bone forming cells with prominent mitochondria
where are osteoblasts
on bone surface
what is an osteoclast
bone resorption multinucleate cell
where are osteoclasts
on surface
what is a osteoprogenitor cell
stem cell; pool of reserve osteoblasts
where are osteoprogenitor cells
on bone surface under periosteum
how do osteocytes recieve oxygen and nutrients
from synovial fluid via haversian canals
what cell type are osteoclasts derived from
macrophages
which type of bone is strong: woven or lamellar
woven weak
fibrous lamellar strong
what is NADH oxidised to
NAD+ + H+ + 2e-
which types of collagen are in hyaline and fibrocartilage
type 1 collagen hyaline
type 2 collagen fibrocartilage
which cells produce synovial fluid
fibroblasts
what is found in the centre of bone
bone marrow
what type of bone surrounds bone marrow
cancellous trabecular spongy bone
what type of bone is located externally
compact cortical lamellar bone
what type of stain is used for bone
silver
what is another name for osteon
haversian system
what are osteon
cylindrical tubes within bone containing the haversian canal
what is contained within the haversian cnaal
arterial and venous branch, nerve fibres and osteogenic cells
what structure runs perpendicularly in bone and what is its function
canaliculi connect osteocytes to one another & to Haversian canal
what is lacunae of bone
space containing osteocytes
how do osteocytes of cancellous trabecular bone survive
from contact to adjacent marrow cavity
what is the structure of lamellar fibrous bone
collagen fibres orientated in the same direction
what is a diarthrosis
synovial joint
what type of joint are the intervertebral discs
cartilaginous
what type of cartilage is found on articular surfaces
hyaline
what type of joint is the pubic synthesis
cartilaginous
what type of cartilage are the tracheal rings
hyaline
what is fibrocartilage formed of
type 1 collagen + chondrocytes
what type of joint is the chostochondral joint and what type of cartilage are the costal cartilages
cartilaginous joint
hyaline cartilage
what is a chondroblast
immature chondrocyte
what cells secrete collagen
chondrocytes
what is cartilage regenerated to
fibrocartilage
what are the most successful joint replacements
hip and knee
give 3 examples of toxins produced by staph aureus
enterotoxin
staphylococcus scaled skin syndrome SSSST
panton valentine leukocydin PVL
what type of infection do sessile bacteria cause
biofilms
name 3 types of cartilage
hyaline
elastic
fibrocartilage
what is perichondrium
fibrous connective tissue layer directly above cartilage surface
what are the 3 types of joints
synovial
fibrous
cartilaginous
what is the difference between a simple and a compound synovial joint
simple: 1 articular surface pair
compoound: >1
what mineral is found in highest quantities in bone
ca hydroxyapatite crystal
what is the diaphysis, physis, metaphysis and epiphysis of long bones
diaphysis shaft, growth plate physis, metaphysis around physis, epiphysis on physis
where does central tolerance take place
primary lymphoid tissue
what cells express HLA class I on their surface
all nucleated cells
what cells express HLA class II on their surface
specialised APCs
