MUSCLE 2 Flashcards
The axons of the plexus form structures called____ which are the sites of transmitter release
Varicosities
The sympathetic nerves primarily release _____ as a transmitter vs the parasympathetic nerves primarily elevate _____ as a transmitter
Noradrenaline
Acetylcholine
____ is produced by an elevation in intracellular Ca2+ and is often augmented by an enhancement of actin/myosin cross binding.
Contraction
____ is produced by decreasing intracellular Ca2+.
Relaxation
Noradrenaline is released by ______ nerves
Acetylcholine is released by _____ nerves
Sympathetic
Parasympathetic
Sympathetic nerves release noradrenaline which can activate __ and __ receptors
Alpha and beta
Parasympathetic nerves release acetylcholine which can activate ____ receptors
Muscarinic
____ nerves releases noradrenaline which can activate alpha and beta receptors
Sympathetic
_____ nerves release acetylcholine which can activate Muscarinic receptors
Parasympathetic
Which receptors (alpha or beta) :
- contract smooth muscle = __
- relax smooth muscle =___
Alpha
Beta
Which receptor most often contract smooth muscle however in blood vessels they act on the endothelium to produce smooth muscle relaxation ?
Muscarinic
The major smooth muscle receptors are activated by ____ and ______
Noradrenaline and acetylcholine
Hormonal and neural mediated smooth muscle contraction and relaxation CNS be mediated through ______ or ____ mechanisms
Pharmacomechanical
Electromechanical
________coupling is contraction or relaxation not mediated by a change in smooth muscle cell membrane potential.
Pharmacomechanical
________coupling is contraction or relaxation mediated by a change in smooth muscle cell membrane potential.
Electromechanical
Skeletal and cardiac muscle contraction in solely mediated via ______ coupling
Electromechanical
Can smooth muscle cells utilize both Pharmacomechanical and electromechanical mechanisms to elicit contraction?
Yes
_________ is produced through the intracellular release of Ca2+ from the sarcoplasmic reticulum (SR) via IP3 receptors and /or the activation protein kinase C (PKC) which enhances myosin/actin cross bridging.
Pharmacomechanical contraction
_______is virtually always produced by an intracellular elevation in cyclic AMP (cAMP) or cyclic GMP (cGMP) which respectively activate cAMP and cGMP dependent protein kinases that inhibit myosin/actin cross bridging
Pharmacomechanical relaxation
Electromechanical contraction and relaxation is mediated by smooth muscle membrane potential ____ and ____
Depolarization
Hyperpolarization
The influx of Ca2+ into the smooth muscle in response to depolarization promotes ___________
Electromechanical contraction
Smooth muscle hyperpolarization closes voltage gated Ca2+ channels and inhibits Ca2+ AP’s and decreases intracellular Ca2+ influx resulting in smooth muscle _______
Relaxation
Depolarization opens voltage-gated ___ channels admitting __
Ca2+
Ca2+
In some smooth muscle cells- ______ can occur along with ____ in response to sympathetic or parasympathetic nerve stimulation via ARP co-release along with adrenaline and acetylcholine
Electromechanical
Pharmacomechanical
____ smooth muscle cells are not electrically connected with gap junction
Multi unit
_____ smooth muscle cells are electrically connected with gap junctions
Unitary
Are multiunit or unitary smooth muscle cells electrically connected with gap junctions?
Unitary
Can multiunit SM cell depolarization or hyperpolarization spread from cell to cell via gap junctions?
No
Can unitary SM cell depolarization or hyperpolarization spread from cell to cell via gap junctions?
Yes
Are multiunit or unitary SM cells similar to skeletal muscles where each muscle cell contracts individually in response to nerve stimulation?
Multiunit
Are multiunit or unitary SM cells similar to cardiac muscles where depolarization is spread from cell to cell ?
Unitary
________ and ______ increase slow wave frequency, peristalsis and SMC contraction via M3 receptors.
Parasympathetic and acetylcholine
____ and ____ rescue slow wave frequency, peristalsis and relax the SMC’s via Beta receptors
Sympathetic and noradrenaline
Sarcomere structure (organization of actin/myosin/troop in/troop myosin and striations) is similar to ___ muscles
Skeletal
The heart is spontaneously at ice, it as no direct motor nerve connection to CNS. Heart muscle fibre contraction is initiated and rhythmically maintained by intrinsic pacemaker cells that produce action potentials within an area called the ______ in the atria.
Sino atrial(SA) node
Action potentials are transmitted between cardiac cells through ______ within intercalated discs forming special tunnels between cells. In contrast skeletal muscle cells are ___ isolated from each other
Gap junctions
Electrically
These characteristics describe which muscle ?(cardiac or skeletal)
1. 20x volume of mitochondria
2. 7.5x capillary density supplying blood
3. Extracts more o2 from blood
4. High myoglobin content
5. Depends on oxidative phosphorylation for energy
Cardiac
______ is the synchronized sequential cardiac muscle contraction and relaxation
Cardiac cycle
In order to pump blood to lungs and into body the cardiac muscle present in the __ and ___ has to contract and relax in sequential coordinated manner
Atria and ventricles
Order the cardiac cycle :
A. The atria contract forcing more blood into ventricles
B. After delay the ventricles contract simultaneously pushing blood into lungs and blood
C. Atria and ventricles fill when the heart is relaxed
C, a, b
Modified cardiac cells form a conduction system tat starts in the ____ and propagates action potentials to the ____ then to the ___ initiating contraction in the cardiac muscle cells within both areas.
SA node
Atria
Ventricles
The ___ is the hearts “pacemaker”
SA node
SA node cells produce spontaneous, repetitive , unique ___ driven action potentials
Ca2+
Place the Cardiac conduction system in order :
1. Depolarization of 0mV triggers a rapid effluent of K+ which hyperpolarizes the cells back to -60mV.
2. The cells start at a resting membrane potential of 60mV. They are leaky to Na+ and Ca2+. The influx of Na+ and Ca2+ slowly depolarize the cells.
3. When the Na+ and Ca2+ leak depolarize the cell to a threshold of -40mV and AP is produced via fast influx of Ca2+ which plateaus at 0mV
2, 3, 1
The cardiac conduction system repeats about __ times per minute - the average resting heart rate in humans
70
Action potentials generated in SA node spread through conduction system and depolarize atrial and ventricular cardiac muscle cells causing them to evolve AP’s and ___
Contract
______ are protein tunnels that connect the cytoplasm of adjacent cells and transmits depolarization
Gap junctions
Every cardiac cell is connected electrically via _____ present within intercalated discs
Gap junctions
Every cardiac muscle cell can evoke an AP when it is depolarized to threshold. The cells within the conducting system can’t contract but they transmit depolarization to cells in ___ and ___ which can contract causing cells to produce action potentials and ____
Atria and ventricles
Contract
Depolarization spreads from cell to cell through gap junction causing adjacent cells to fire ________
Action potentials
__ induced depolarization triggers ___ influx through special voltage gated channels. This triggers a large release of __ from sarcoplasmic reticulum, resulting in ____
Na+
Ca2+
Ca2+
Contraction
___ influx produces depolarization —> produces __ influx —> triggers ____
Na+
Ca2+
Contraction
Order sequence of depolarization/contraction in heart:
1. SA node spontaneously fires AP’s depolarization spreads through atria producing AP’s in atrial muscle cells
2. Delay occurs then depo. and AP’s transmit down conducting system to apex of ventricle
3. Depo. & and AP spread from apex up through ventricle cardiac cells, produce contraction, squeezes blood into lungs and body
4. spread of depo. & production of AP’s through atria following by atrial contraction (push blood to ventricles)
1, 4, 2, 3
In skeletal muscle cells the AP travels through t-tubule system and activates ___ receptor which releases Ca2+ from sarcoplasmic reticulum (SR)
DHP
Do skeletal or cardiac muscle cells have DHP as the receptor ?
Skeletal
Do skeletal or cardiac muscle cells have voltage gated Ca2+ channels ?
Cardiac
What is the difference between action potentials in skeletal vs cardiac muscle cells
Skeletal- DHP receptor
Cardiac - Voltage gated Ca2+ channels
The ____ and ___ nervous systems control the heart rate and strength of ventricle contraction
Sympathetic
Parasympathetic
SNS release ____ and ______ and bind to B1 receptors depolarizing SA node cells = beat faster & enhancing ___ release which increase force of ventricle cell contraction.
Noradrenaline and adrenaline
Ca2+
Vagal (PSNS) release ____ which binds to ____ receptors which hyperpolarizes SA cells and conducting system reduce SA node firing and conduction
Acetylcholine
Muscarinic
_____ nerve (SNS) when stimulated releases neurotransmitters at SA node to increase ____
Accelerator
Heart rate
- ___ nerve (PSNS) when stimulated releases neurotransmitter at SA node to decrease _____
Vagus
Heart rate
Stretching the cardiac cells produces a more optimal orientation of ___ and ___ allowing greater contractile force to be generated
Actin and myosin
What law is the intrinsic control of ventricular contraction?
Starlings
