Physio_ Week 4-3 - legacy

Thin myofilaments consist of SMC actin and tropomyosin.

An example is the β1 adrenergic receptor.

cGMP activates phosphatase.

Most vascular smooth muscle, which induces vasoconstriction via α1 adrenergic receptors, is regulated only by the sympathetic division.

Both have thin and thick filaments that slide over each other for contraction, require ATP for muscle contraction, and have intracellular calcium ([Ca2+]) as a critical regulator of contraction.

Through mechanisms such as enzyme action, reuptake, and diffusion.

ACh esterase helps in the termination of the signal by breaking down acetylcholine.

No, smooth muscle cells do not have T tubules, but they do have sarcoplasmic reticulum (SR), which varies in importance among different smooth muscle cells.

It involves varicosities with neurotransmitter vesicles, allowing one axon to affect many target cells rather than a 1-1 transmission.

Epinephrine (E) has a higher affinity for β2 adrenergic receptors and is more effective than norepinephrine (NE) in causing vasodilation.

L-type voltage-gated calcium channel.

They can block action potentials, but smooth muscle cells are not sensitive to TTX, which blocks voltage-gated sodium channels.

The plateau phase lasts around 10 seconds.

MLC is phosphorylated by MLCK.

MLC-P is dephosphorylated by phosphatase.

It inhibits calcium entry into the cell.

Pharmacomechanical activation refers to changes in contraction or relaxation of smooth muscle cells without a change in membrane potential, often through ligand binding to receptors.

Rho-kinase activates and phosphorylates myosin light chain (MLC), increasing calcium sensitivity and allowing for the same contraction with less intracellular calcium.

Electromechanical activation involves depolarization from neighboring cells or ligand-dependent mechanisms that lead to contraction.

Ligand binding to a membrane receptor can activate intracellular signaling pathways, leading to calcium release and contraction of smooth muscle cells.

Nicotinic receptor, which is a ligand-dependent ion channel that generates fast EPSP.

Long.

E is only released from the adrenal medulla, which is a modified postganglionic neuron in the sympathetic system.

Age and hormonal effects can change the number of receptors.

Slow waves are changes in membrane potential that can lead to action potential formation and subsequent contractile force in smooth muscle cells.

Dense bodies serve as anchor points for thin filaments and are connected to the plasma membrane, facilitating contraction.

Calcium is an important regulator in smooth muscle contraction, as its release into the cytoplasm is crucial for the contraction process.

It changes the activity of the synapse by inhibiting norepinephrine (NE) uptake.

Parasympathetic ganglia are close to the target cell, while sympathetic ganglia are close to the CNS/spinal cord.

The intracellular calcium level decreases through mechanisms such as membrane Ca2+ -ATP-ase, membrane Na+/Ca2+ antiporter, and SR - Ca2+ -ATP-ase.

cGMP activates phosphatase, which leads to relaxation of smooth muscle.

Single-unit smooth muscle is more common, has gap junctions between cells, exhibits spontaneous contractions and basal activity, and neural signals only modulate the activity.

MLCK can be activated by an increase in intracellular calcium levels, forming a calcium-calmodulin complex that activates MLCK.

Receptor activity can be efficiently modulated by agonists and antagonists, making them important for pharmacological interventions.

1. Depolarization from neighboring cells via gap junctions, 2. Neural stimulation leading to transmitter release, 3. Mechanical activation through mechanosensitive channels.

NE reuptake leading to degradation in the cytoplasm and diffusion of transmitters.

Blocking transmitter release (ACh), blocking choline reuptake, and blocking ACh esterase.

The depolarization phase involves L-type voltage-gated Ca2+ channels, while the repolarization phase involves voltage-gated late K+ channels.

Calcium mechanisms are important for both the formation and maintenance of action potentials.

cAMP induces MLCK phosphorylation, which decreases calcium sensitivity.

The two systems are counteracting, making the regulation of the autonomic nervous system not simple.

General activation of the sympathetic nervous system leads to increased blood pressure, heart rate, and dilation of pupils, among other effects.

An increase in intracellular calcium concentration is important to induce contraction of smooth muscle cells.

Thick myofilaments are composed of myosin, which includes two heavy chains and two light chains that bind to each heavy chain.

The Bayliss effect refers to the contraction induced by mechanical changes, such as vessel stretching due to increased pressure, which opens mechanosensitive ion channels.

The action potential in smooth muscle cells has a much smaller amplitude, lasts longer, and involves different ion channels.

Calcium binds to calmodulin, changing its conformation and allowing it to bind to MLCK, which activates MLC and induces phosphorylation of MLC, leading to contraction.

Each cell is independently controlled by neural signals.

Different afferents from the periphery, somatic afferents to the CNS, interneurons, further signals from the CNS, and local reflexes.

The postganglionic receptor is a nicotinic acetylcholine receptor (nAChR), which is ligand-gated.

Smooth muscle contraction requires much less ATP compared to skeletal muscle contraction.

α1 adrenergic receptors are stimulated, leading to vasoconstriction in blood vessels of skeletal muscle.

The pupillary sphincter is regulated by the parasympathetic division, while the pupillary dilator is regulated by the sympathetic division.

Smooth muscle cells are uninucleated, small, not striated, lack Z lines, and have thin filaments anchored to dense bodies and the plasma membrane.

cAMP induces phosphorylation of MLCK by PKA, resulting in decreased calcium sensitivity.

Cranial nerves 3, 7, 9, and 10.

Near or within the organ, very close to the target cell.

Long, as it is close to the organ.

Norepinephrine is converted to epinephrine by the enzyme N-methyltransferase.

The first synapse is between the preganglionic axon and the postganglionic neuron.

The actin-myosin cycle in smooth muscle is slow, involving actin-myosin cross bridges.

Autonomic nerves release neurotransmitters from varicosities, which can affect multiple smooth muscle cells.

Red indicates a state of being fully relaxed and then fully contracted, with a return to complete relaxation after some time.

The parasympathetic division induces non-viscous, enzyme-rich saliva, while the sympathetic division induces viscous, mucinous saliva.

They help regulate functions such as heart rate, pupillary response, and blood pressure.

The pathway involves a preganglionic neuron from the CNS, which synapses with a postganglionic neuron in a peripheral ganglion, leading to the target cell.

Examples include the esophagus and urinary bladder for fully relaxed and contracted states, sphincters for normally contracted states, and smooth muscle in airways and blood vessels for partial tone.

The myosin light chain in smooth muscle has different subunits than those found in skeletal muscle.

cAMP (via β2-adrenergic receptor stimulation) and cGMP (NO-dependent activation) are crucial for smooth muscle relaxation.

In the sympathetic system, the preganglionic neurons are long.

Norepinephrine (NE) is more effective than epinephrine (E) for α1 adrenergic receptors.

The main divisions of the ANS are the Parasympathetic, Sympathetic, and Enteric nervous system.

Smooth muscle cells are not a homogenous population; there are many differences between smooth muscle cells in different organs.

MLC, when phosphorylated, allows for the binding of actin and myosin.

The phosphorylation of myosin light chain is mediated by MLCK (myosin light chain kinase).

There are two synapses involved: one between the preganglionic and postganglionic neurons, and the other at the target cell.

Phosphorylated MLC changes the structure connected to the heavy chains, which is essential for the contraction of smooth muscle cells.

The expression of N-methyltransferase is dependent on high levels of steroid hormones.

The receptors for acetylcholine in effector cells are muscarinic acetylcholine receptors (mAChR), which include M1, M2, M3, M4, and M5.

MLC-P is the phosphorylated form of myosin light chain.

The expression pattern is dynamic and can lead to tissue-specific cellular responses.

Autonomic neurotransmitters regulate unconscious autonomic functions, which are important for maintaining homeostasis in the body.

The adrenal medulla is part of the sympathetic division.

The adrenal medulla contains modified, specific postganglionic neurons.

There are two heavy chains in myosin for smooth muscle.

They release their transmitter directly into the bloodstream.

Close to the spinal cord, in pre/paravertebral ganglia.

The adrenergic receptors associated with norepinephrine are α1, α2, β1, β2, and β3.

The adrenal medulla is considered a modified postganglionic neuron.

The sympathetic division increases heart rate, while the parasympathetic division decreases it.

Many action potentials are correlated with contraction, indicating that the frequency of action potentials can influence the strength of contraction.

Green indicates a normally contracted resting state, where the muscle can relax upon receiving a signal and then contract again.

Blue represents a normally partial tone, where there is an increase in contraction followed by stimulation for relaxation.

Rho-kinase has an additive effect with MLCK, enhancing contraction by increasing calcium sensitivity.

Less intracellular calcium is needed to induce the same contraction due to increased calcium sensitivity.

From the thoracic and lumbar regions of the spinal cord.

Acetylcholine (ACh) is released by the preganglionic axon.

It limits calcium entry into the cell, inducing relaxation.

The postganglionic neurons in the adrenal medulla lose their axons.

Acetylcholine.

The adrenal gland produces high levels of steroids, which are necessary for the formation of epinephrine.

Thin and thick filaments in smooth muscle are connected to each other through gap junctions between adjacent cells.

Each smooth muscle cell has its own innervation.

Short.

Short.

Acetylcholine (ACh) is primarily used at the second synapse in the parasympathetic division.

There are different relationships between membrane potential and force generation in different types of smooth muscle.

Rho-kinase inhibits the function of phosphatase, leading to increased phosphorylation of MLC and stronger contractions.

Only electrotonic potential changes at first, followed by summation of all signals, leading to an action potential if the threshold is reached.

Norepinephrine (NE) is primarily used at the second synapse in the sympathetic division.