πͺπ»&π€ Flashcards
A band
DARK
stacked set of thick filaments (myosin) + portion of thin filaments (actin)
actin overlaps on both ends of the thick filaments
H zone
lighter area in the middle of the A band, where the thin filaments do not reach
M line
extends vertically down the middle of the A band; is in the middle of the H zone
I band
LIGHT
remaining portions of the thin filaments
Z line
dense, vertical line, located in the middle of each I band;
flat cytoskeletal disc that connects the thin filaments of two adjoining sarcomeres
sarcomere
smallest unit of skeletal muscle that can undergo muscle contraction;
area between two Z lines
Transverse (T) tubules
location?
runs from _______ to the _______ of the muscle fibre => ____ (slow/rapid) spread of the AP
at the junction of A and I band, where surface membrane dips into the muscle fibre;
runs from surface to the central portions of the muscle fibre => rapid spread of the AP
sarcoplasmic reticulum (SR) is modified _______ that consists of fine network of ____________ enclosed compartments surrounding each myofibril like a __________ [think clothing]
sarcoplasmic reticulum (SR) is modified ENDOPLASMIC RETICULUM that consists of fine network of INTERCONNECTED MEMBRANE enclosed compartments surrounding each myofibril like a MESH SLEEVE
lateral sacs (terminal cisternae) separated from adjacent T tubules by \_\_\_\_\_\_, \_\_\_\_ [substance] storages; the spread of \_\_\_\_ down a T tubule triggers release of \_\_\_\_ [substance] from the SR into \_\_\_\_\_\_\_ [substance/organelle in the cell]
separated from adjacent T tubules by a slight gap, Ca2+ storages;
the spread of AP down a T tubule triggers release of Ca2+ from the SR into cytosol
foot proteins aka ryanodine receptors
bridge the gap between lateral sacs and T tubules, are Ca2+ release channels
dihydropyridine receptors are also called \_\_\_\_\_\_\_\_\_ why are they called dihydropyridine? nature of their work? what electrical activity activates these channels?
= T tubule receptors;
can be blocked by the drug dihydropyridine
voltage-gated sensors;
local depolarisation activates these channels
AP β> local depolarisation β> T tubule receptors trigger the opening of _______ β> opening of the ________ not directly associated with the ________ β> Ca2+ released into _______ β> exposure of the ______ on the ____ molecules so that they can link with ________ cross bridges β> beginning of the cross bridge cycle
ryanodine receptors ryanodine receptors T tubule receptors cytosol binding sites actin myosin
Cardiac muscle AP
________ plateau = _________ contraction => ________ (adequate/inadequate) ejection time
plateau due to activation of ________ channels (why this name?)
PROLONGED plateau = PROLONGED contraction => ADEQUATTE ejection time
plateau due to activation of L-TYPE Ca2+ channels (L because opened for Long)
actin is build from chains thatβ¦.
intertwine
tropomyosin looks like a _____ [sewing kit], physically covers ______
thread like
actin
troponin is made up of 3 subunits, what does each bind to?
one binds to tropomyosin
one to actin
one combines with Ca2+ ions released from lateral sacs
Myosin looks like ______ [sports gear], _____ is twisted
globular head has two sites, what does each bind to?
like a golf club
shaft is twisted
globular head has two sites: one for binding of actin, the other one for myosin ATPase
A band (during contraction)
stays same width (A band = thick filaments, hence stays the same)
I band (during contraction) width \_\_\_\_ (decr./same/incr.) \_\_\_\_\_\_ filaments are \_\_\_\_ overlapping \_\_\_\_\_ filaments
width π½
THIN filaments are NO LONGER overlapping THICK
H zone (during contraction)
width π½ (thick filaments not overlapping thin)
cross bridge cycle has 4 steps:
binding
power stroke
detachment
binding
(1st) Binding [of the cross bridge cycle]
what binds to what?
myosin cross bridge binds to actin molecule
Power stroke [of the cross bridge cycle]
what happens?
what is the consequence?
cross bridge bends, pulling thin myofilament inward
Detachment [of the cross bridge cycle]
it happens at the end of what?
what happens later?
cross bridge detaches at end of power stroke and returns to normal conformation
(2nd) Binding [of the cross bridge cycle]
what binds to what? what is the next step?
cross bridge binds to more distal actin molecule;
cycle repeats
CNS (____) β> ______ β-> _____ & ______ & _______ & _______
central nervous system PNS = peripheral nervous system somatic efferent enteric (ENS) autonomic (ANS) somatic and visceral afferent
ANS β-> ______ & ______
sympathetic division
parasympathetic division
SNS transmitters (2), specify order
pregangionic neurone: ACh (cholinergic)
postganglionic neurone: usually NA = noradrenaline (adrenergic)
PSNS transmitters (2), specify order
pregangionic neurone: ACh (cholinergic)
postganglionic neurone: ACh (cholinergic)
ACh is synthesised byβ¦
choline acetyltransferase (CAT)π±π±π±
ACh is degraded to _____ and _____ by
acetate
choline
acetylcholinesterase (AChE)
type of G protein: \_\_\_\_ G protein coupled receptor: M1 action: \_\_\_\_\_\_ affected organ(s): stomach effect on the organ: \_\_\_\_\_\_
Gq
simulation of phospholipase C
πΌ acid secretion
type of G protein: Gi G protein coupled receptor: \_\_\_\_ action: inhibition of adenylyl cyclase & \_\_\_\_\_\_\_\_\_ affected organ(s): heart effect on the organ: \_\_\_\_\_\_
M2
opening of K+ channels
π½ rate
type of G protein: Gq
G protein coupled receptor: _____
action: simulation of phospholipase C
affected organ(s): salivary glands [effect?], ______ [contraction]
- _______ is indirectly relaxed by ____ receptor activation due to release of ______ from neighbouring endothelial cells
M3
increased secretion
visceral smooth muscle
Vascular smooth muscle
M3
nitric oxide
type of G protein: Gs G protein coupled receptor: \_\_\_\_ action: \_\_\_\_\_\_\_\_ affected organ(s): heart effect on the organ: \_\_\_\_\_\_
Ξ²1
stimulation of adenylyl cyclase
πΌ rate & force
type of G protein: \_\_\_\_ G protein coupled receptor: Ξ²2 action: stimulation of adenylyl cyclase affected organ(s): \_\_\_\_\_\_ effect on the organ: \_\_\_\_\_\_
Gs
bronchial and vascular smooth muscle
relaxation
type of G protein: Gq G protein coupled receptor: \_\_\_\_ action: stimulation of phospholipase C affected organ(s): \_\_\_\_\_ effect on the organ: \_\_\_\_\_\_
Ξ±1
vascular smooth muscle
contraction
type of G protein: \_\_\_\_\_ G protein coupled receptor: Ξ±2 action: \_\_\_\_\_\_\_\_ affected: NorAd release effect: \_\_\_\_\_\_
Gi
inhibition of adenylyl cyclase
inhibition
NorAd is reuptaken by two transporters:
uptake 1 (U1), and uptake 2 (U2)
NorAd is metabolised by two enzymes:
monoamine oxidase (MAO,) and catechol-O-methyltransferase (COMT)
examples of synergistic muscles (synergists) in upper limb (2 pairs)
biceps brachii & brachialis
triceps brachii & anconeus
examples of flexors in upper limb (2)
Biceps brachii
brachialis
examples of extensors in upper limb (2)
triceps brachii
anconeus
axial muscles controlβ¦
movements of the trunk (maintaining posture)
proximal (or girdle) muscles are found in _____, ______, ______ and ______
they [action]
the shoulder, elbow, pelvis and knee
mediate locomotion
distal muscles move ______, _____, and ______
they [action]
the hands
feet
digits
allow fine manipulation of objects by the hand
Axons of LMNs (lower motor neurones) exit the spinal cord in _________
the ventral roots
Each ventral root joins with a ________ to form a ___________ (30 pairs) which
contains sensory and motor fibres
dorsal root
mixed spinal nerve
Motor neurones
belong to a spinal segment: _______ (C) ______, _______ (T) _______, ______ (L) ______ and ______ (S) _____
cervical 1-8
thoracic 1-12
lumbar 1-5
sacral 1-5
Motor neurones are not distributed equally within the spinal cord: greater number in the ________ (______) supplying the arm and _________ (______) supplying leg
cervical enlargement (C3 - T1) lumbar enlargement (L1-S3)
Motor neurones that innervate distal and proximal musculature are mainly in __________ of the spinal cord, whereas those innervating the axial musculature _________
lumbar-sacral segments
occur at all levels
motor unit
alpha motor neurone + all the skeletal muscle fibres that it innervates;
the smallest functional component of the motor system
motor neurone pool
collection of alpha motor neurones that innervate a single muscle
LMNs innervating axial muscles ____ to those innervating distal muscles
medial
LMNs innervating flexors _____ to those supplying extensors
dorsal
3 sources of input to an alpha motor neurone that regulate its activity are:
- central terminals of dorsal root ganglion cells whose axons innervate the muscle spindles
- upper motor neurones (UMNs) in the motor cortex and brain stem
- spinal interneurones
Slow-oxidative (Type I) Fibres:
ATP derived from ______
_____ (slow/fast) contraction and relaxation
_____ (β
/β)fatigue resistant β______β because of high _____ content
oxidative phosphorylation slow β "red meat" myoglobin
Fast (Type II) Fibres β type IIa
ATP derived from ______
_____ (slow/fast) contraction and relaxation
_____ (β
/β)fatigue resistant
_____ (pale/red) and _____ (β
/β) well vascularised
oxidative phosphorylation fast β red β
Fast (Type II) Fibres -- type IIx ATP derived from \_\_\_\_\_\_ \_\_\_\_\_ (slow/fast) contraction \_\_\_\_\_ (β /β)fatigue resistant \_\_\_\_\_ (pale/red) and \_\_\_\_\_ (β /β) well vascularised "\_\_\_\_\_\_"
glycolysis fast β pale β white meat
origin
end of the muscle attached to the more stationary part of the skeleton
insertion
end attached to the skeletal part that moves
contractile response (twitch) has 3 parts:
lag -> contraction -> relaxation
twitch
when a muscle fibre is restimulated after complete relaxation, 2nd twitch = 1st twitch, magnitude-wise
twitch summation
when a muscle fibre is restimulated before complete relaxation and a 2nd twitch is added on to 1st
tetanus / tetanic π’π»π₯
when a muscle fibre is stimulated so rapidly that it doesnβt have an opportunity to relax at all between stimuli,
a maximum sustained contraction occurs
For a muscle to shorten during contraction, the tension developed in the muscle must _____ the forces that oppose movement of the bone to which the muscleβs insertion is attached
exceed
example of loadβ¦
is the weight of the object being lifted
two primary types of contraction:
isotonic contraction (lift object) isometric contraction (hold object)
isotonic contraction = muscle tension _______ (changes/remains constant) and the muscle length _______ (changes/remains constant)
remains constant
changes
Isometric contraction:
the muscle length _______ (changes/remains constant), so tension develops at ________ (increasing/constant) muscle length
remains constant
at constant muscle length
the two types of isotonic contractions are:
concentric
eccentric
concentric contraction
muscle shortens under load
eccentric contraction
muscle lengthens under load
Skeletal muscle can be attached to:
- _____
- _____ (e.g. ______)
- _____ (e.g. ______)
- _____
- _____ (e.g. ______)
- _____ (e.g. ______)
- _____
- _____ ( [how?], e.g. ______)
Bone at each end
crossing one joint (e.g. deltoid)
crossing multiple joints (e.g. semimembranosus)
Bone at one end
and a different type of structure at the other (e.g. extraocular eye muscles)
or nothing at the other (tongue)
Itself (forming a circle; e.g. sphincter)
____ is a rigid structure capable of moving around a pivot point known as _____
lever
fulcrum (Krum z HP)
_____ function as levers, the _____ serve as fulcrums and the _____ provide the force to move the bones to produce directed movement
bones
joints
muscles
Levers can be used so that a small force can move a much bigger force i.e. ___________
mechanical advantage
There are four parts to a simple lever:
lever arm
pivot
effort
load
there are 3 classes of levers:
class 1 lever class 2 lever class 3 lever
Class 1 lever \_\_\_\_\_\_----\_\_\_\_\_\_----\_\_\_\_\_\_ commonly known as "\_\_\_\_\_\_" and "\_\_\_\_\_\_" \_\_\_ (β /β) mechanical advantage e.g. \_\_\_\_\_ \_\_\_\_\_ (large/small) load \_\_\_\_\_ (large/small) range
effort pivot load βSee-sawβ; βCrowbarβ β neck & head large & small, hence mechanical advantage
Class 2 lever
______β-______β-______
commonly known as β______β
Effort force ______(>/
pivot load effort βWheelbarrowβ < β standing on the tippy toes
Class 3 lever
______β-______β-______
commonly known as β______β
___ (β
/β) mechanical advantage, as effort ______(>//
pivot effort load βShovelβ β greater than larger and greater arm & forearm small & large, hence mechanical disadvantage
types of joints (6):
ball-and-socket joint (pectoral gridle + arm) pivot joint (elbow) saddle joint (wrist) ellipsoid joint (fingers) hinge joint (knee) plane joint (ankle)
joints that alter position during movement, which influences their βlever statusβ tend to ______ mechanical disadvantage, e.g. _____
minimise
knee
Synovial fluid in cavity β 2 functions
lubricates the joint
provides nourishment for cartilage
Capsule & synovial membrane β 2 functions
hold joint together
membrane makes synovial fluid
Articular cartilage β- 2 functions
cushions impact (flexibility function) protects bone
intrinsic ligaments β where?
part of capsule
extrinsic ligaments β- where?
outside capsule
knee joint
ligaments β- 2 functions
hold bones together, prevent unwanted movement
the myotatic reflex
when a skeletal muscle is pulled, it pulls back
Change in length (and rate of change) is registered by a sensory organ within the muscle, __________; this contributes to non-conscious ____________
the muscle spindle
proprioception
spindles consist of (4):
- a fibrous capsule
- intrafusal muscle fibres
- sensory afferents that innervate the intrafusal fibres
- gamma motor neurone efferents that innervate the intrafusal fibres
describe sensory afferents
innervate the intrafusal fibres
Ia class, myelinated and very fast conducting
Striking of the _____ tendon with a ______ [item] causes a β______β [behaviour] underpinned by the _______ [type of reflex]
patellar
tendon hammer
knee jerk
myotatic reflex
reflex [definition]
rapid, automatic response generated by the circuitry of the spinal cord
reflex [function]
- controlling automatic behaviour
- important role in voluntary movement
the myotatic reflex is a ___*___, the only one in humans
___*___ is (2):
*monosynaptic reflex arc
rapid
most prominent in extensor muscles
the myotatic reflex can be used to assessβ¦
the functional integrity of the spinal cord at specific levels
Muscle (joint) assessed: biceps (elbow)
Spinal level assessed: __
C5-C6
Muscle (joint) assessed: _____
Spinal level assessed: C5-C6
supinator (wrist)
Muscle (joint) assessed: triceps (elbow)
Spinal level assessed: __
C7
Muscle (joint) assessed: ______
Spinal level assessed: L3-L4
quadriceps (knee)
Muscle (joint) assessed: ____
Spinal level assessed: S1
gastrocnemius (ankle)
intrafusal fibres can be subdivided on the basis of morphology and function into (1+2+1):
- Nuclear bag fibres
- Bag 1 or dynamic
- Bag 2 or static
- Chain fibres
characteristics of bag 1 or dynamic
very sensitive to the rate of change of muscle length
innervated by dynamic gamma motor neurones
characteristics of bag 2 or static
more sensitive to the absolute length of the muscle
innervated by static gamma motor neurones
characteristics of chain fibres
sensitive to the absolute length of the muscle
innervated by static gamma motor neurones
types of afferent fibre that innervate the intrafusal fibres (2):
Both sets of afferents respond to stretch, but the _____
are more sensitive to _______ and _______ are more sensitive to _________
Ia afferents
II fibres
Ia fibres
rate of change
II fibres
absolute length of the intrafusal fibres
afferent fibre that innervate the intrafusal fibres β Ia afferents [description]
form a primary annulospiral nerve ending winding around the centre of all intrafusal fibres
afferent fibre that innervate the intrafusal fibres β II fibres
are more slowly conducting, form flowerspray endings on all intrafusal fibres except the bag 1 dynamic type
RESPONSE TO SELECTIVE ACTIVATION OF STATIC AND DYNAMIC GAMMA MOTOR NEURONES β Ia fibre
responds to both the rate of change of muscle length (dynamic response) and absolute length (steady state, or static response) of the muscle
RESPONSE TO SELECTIVE ACTIVATION OF STATIC AND DYNAMIC GAMMA MOTOR NEURONES β Stimulation of static gamma fibre
causes steady state, or static response, to πΌ
RESPONSE TO SELECTIVE ACTIVATION OF STATIC AND DYNAMIC GAMMA MOTOR NEURONES β Stimulation of dynamic gamma fibre
enhances the dynamic response to stretch
only static gamma motor neurones are active whenβ¦
an activity involves muscle length to change slowly and predictably
only dynamic gamma motor neurones are active duringβ¦
behaviours in which muscle length changes rapidly and unpredictably
free nerve endings
location:
characteristics:
location: found in capsule and connective tissue
characteristics: most numerous
HT [high threshold] & SA [slowly adapting]
nociceptive function
Golgi-type endings
location:
characteristics:
location: only in ligaments
HT [high threshold] & SA [slowly adapting]
protective role?
Paciniform endings
location:
characteristics:
location: found in periosteum near the articular attachments and the fibrous part of the joint capsule
characteristics: LT [low threshold] & SA [slowly adapting]
acceleration detectors
Ruffini endings
location:
characteristics:
location: mainly in joint capsule
characteristics: LT [low threshold] & SA [slowly adapting]
static position and speed of movements
Proprioceptive information arises from (3):
- Muscle spindles
- Golgi tendon organs
- Joint receptors
Spinal interneurons receive input from (4):
- primary sensory axons (e.g. Ia and Ib fibres)
- descending axons from the brain
- collaterals (branches) of lower motor neurones
- other interneurons
Inhibitory interneurons mediate:
- the inverse myotatic response
- reciprocal inhibition between extensor and flexor muscles
Excitatory interneurons mediate 2 reflexes:
the flexor reflex
the crossed extensor reflex
The flexor reflex
Noxious stimulus causes limb to flex by (2):
- contraction of flexor muscles via excitatory interneurones
- relaxation of extensor muscles via excitatory and inhibitory interneurones
Crossed extensor reflex
Noxious stimulus causes limb to extend by (2):
This reflex enhances postural support during withdrawal of a foot from a painful stimulus (you do not fall over!)
- contraction of extensor muscles via excitatory interneurones
- relaxation of flexor muscles via excitatory and inhibitory interneurones
excitation-contraction coupling
the way in which the muscle converts an AP (electrical stimulus) into a contraction (mechanical response)
latent period
time delay between AP and muscle contraction
