Quiz 3 Mod 2 Bio 362

What is the order of CO₂ transport in the body?

1. 7% dissolved in the plasma

2. 23% bound to hemoglobin

3. 70% converted to HCO₃^- (Bicarbonate)

What is the first step of CO2 transport

CO2 from cells diffuse out of the tissue into the capillaries

What is the second step of CO2 transport

7% dissolves in the blood plasma

What is the third step of CO2 transport

The remaning 93% enters Red Blood Cells where 23% binds to hemoglobin f

What is the name of carbon dioxide that binds to hemoglobin

Carbaminohemoglobin

What is the fourth step of CO2 transport

CA combines the 70% of remaining CO2 with water to make HCO3- and H+

What enzymes convert CO2 into HCO3-?

Carbonic Anhydrase

How does the pH of blood not change with the production of H+?

The hemoglobin stays bound to H+

Where does HCO3- stay

It stays in the RBCs

What is the fifth step in CO2 transport

Chloride shift → HCO3- is transported out of RBC and back into the plasma in exchange for Cl-

Waht is the sixth step of CO2 transport

Once blood reaches the lungs, the dissolved CO2 diffuses across the pulmonary capillaries into the alveoli

What is the seventh step of CO2 transport

The decrease in the pressure of CO2 in blood drives CO2 to unbind hemoglobin and diffuse out of the Red Blood Cells

What is the eighth step in CO2 Transport

The decrease of CO2 in Red Blood Cells causes Carbonic Anhydrase to reverse the reaction that formed HCO3-

What law does the reversal of HCO3- follow

The law of mass action

What is the purpose of chloride shifts

An exchange of two negative molecules cancels out any changes in charge and maintains the electrochemical gradient

what happens to the blood during exercise

it gets more acidic because cells produce and release H+ and CO2 which gets dissolved in plasma and creates carbonic acid

What characteristics vary in smooth muscles

1. Location

2. Patterns of Contractions

3. Cell - Cell Communication

How can muscle be identified

Its physiology will reflect its function depending on its origin

Where is Vascular Smooth muscle found?

walls of blood vessels

Where is GI Smooth Muscle found?

gut and accessory organs of the digestive system

Where is Urinary Smooth Muscle found?

bladder and ureters

Where is Respiratory Smooth Muscles found?

Airways

Where is Reproductive Smooth Muscles found?

Reproductive Structures

Describe the Phasic Smooth Muscle Type

Smooth muscle that is usually in its relaxed form and contracts at certain times

Describe the Tonic Smooth muscle type

A type of smooth muscle that is held in the contracted phase and relaxes at certain times

→ The opposite of phasic

What is a single unit smooth muscle

Single unit smooth muscle is connected by gap junctions and contract as a single unit

The most common type

What is another name for single unit smooth muscle

Visceral smooth muscle, because it is found in the body’s hollow organs called viscera

What are multiunit smooth muscles

muscle units that must be individually stimulated and are not electrochemically connected

They are useful in small/fine motor controls like the iris and ciliary muscles

Sometimes found in reproductive organs

How are smooth muscles similar to striated muscles

1. Force and movement ar eproduced by actin and myosin crossbridge

2. Calcium is still the signaling trigger

How are Smooth muscles diffrent from striated muscles

1. Smooth muscles do not have sarcomeres, so the actin and mysin are arranged differently, resulting in smooth appearance instead of striated

2. Calcium comes from different places in the cell

3. There is no troponin in smooth muscles, other mechanisms control contraction

Describe the anatomy of smooth muscle

1. no sarcomeres

2. skeletom of intermediate filaments and dense bodies

3. actin attached to dense bodies

4. Myosin between actins

How are the actin and myosin heads oriented on smooth muscle

Myosin heads are positioned on either side and pull actin in opposite directions

What is the benefit of pulling in opposite directions for actin and myosin

Gives a longer range of contractile lengths because they pull diagonally apart

What is the first step of smooth muscle contraction

Calcium enters the ECF

What are the ways that calcium can enter the ICF

1. Calcium induced Calcium release → calcium entering from the ECF binds to the ryanodine receptors that release calcium from the SR (Sarcoplasmic Reticulum)

2. IP₃ Receptor → Calcium channel on SR that opens through GPCR activation

One way or another, calcium will find its way into the cell

What is the second step in smooth muscle contraction

Calcium binds to calmodulin (CaM)

→ A calcium modulator

What is the third step of smooth muscle contraction

Ca²⁺ - CaM complex activates Myosin Light Chain Complex (MLCK)

What is the fourth step of smooth muscle contraction

MLCK turns on myosin heads by using ATP to phosphorylate Myosin Light Chains

The ATP used is separate from the ATP used for crossbridge cycling

What is the fifth step in Smooth Muscle Contraction

Myosin engages in cross bridge cycing with actin

What is the sixth step of smooth muscle contraction / first step of smooth muscle relaxation

Calcium gets pumped back into the SR and ECF

What is the seventh step of smooth muscle contraction / second step of smooth muscle relaxation

Calcium unbinds from CaM and the MLCK is inactivated

What is the eighth step of smooth muscle contraction / third step of smooth muscle relaxation

Myosin Light Chain Phosphotase (MLCP) dephosphorylates myosin light chains and turns off the myosin heads

This is always present in the ICF

What is the ninth step in smooth muscle contraction / fourth step of smooth muscle relaxation

Cross bridge cycling stops and myosin heads are off

What controls smooth muscle activity

The relative activity of MLCK and MLCP; the ratio of active MLCK/MLCP

What is the role of MLCK

It turns on crossbridge cycling

What is the role of MLCP

Turns of Cross bridge cycling

How does MLCP regulate Ca²⁺

It controls the smooth muscle’s sensitivity to calcium

ie. If there is lots of MLCP that is active, the cell will not respond as strongly to calcium and becomes desensitized

What are the types of coupling in smooth muscles

1. Electromechanical Coupling → Muscles contract in response to a change in the membrane potential

2. Phamacomechanical Coupling → Muscle contracts/relaxes in response to chemical signaling with no change in the membrane potential

What are the types of Electromechanical Coupling

1. Voltage gated Ca²⁺ channels → Action potentials on the cell membrane trigger the opening of Ca²⁺ channels

2. Chemically gated Ca²⁺ channel → A chemical signal binds to Ca²⁺ channel, opening them

3. Stetch Activated Ion Channels → Physical stretching of the cells causes a depolarization that opens nearby Ca²⁺ channels

What happens in Pharmacomechanical Coupling

Muscle contractions are independent of membrane potential and instead are caused by the binding of different chemical signals that affect MLCK and/or MLCP

True or False; Some smooth muscles create their own action potentials

True

What is slow wave potential

When membrane potential cycles between depolarization and hyperpolarization while occasionally reaching threshold values

What is pacemaker potential

Similar to cardiac muscle, where action potentials are automatically created at a regular rhythm

How is smooth muscle controlled

endocrine system and autonomic division of the nervous system can modulate membrane potentials in smooth muscle

→ They can change the rate and strength of muscle contractions

What is the primary function of the digestive system

Move substances from external environment into the body to support homeostasis

→ energy water ions

Eliminates metabolic waste

Must also maintain mass balance, defend against pathogens, and not digest itself

What is secretion

The releas of chemicals from cellsW

What are the types of secretion

1. Endocrine goes into blood

2. Exocrine goes into GI tract

What is digestion

The chemical and mechanical breakdown of food into absorbable units

What is absorption

The movement of materials from the GI tract to the ECF

What is motility

The movement of material though the GI tract

What is excretion

elimination of wastes from the body

What is the relationship between ingestion and secretion

The volume of ingestion and secretion into the GI must equal the volume leaving through absorption or excretion

2L of food/drink digested but 7L of secretions from body

Almost all of it is absorbed and only 0.1L defecated

What is the GI tract composed of

A tube consisting of oral cavity (mouth/phraynx) esophagus stomach small intestine large intestine rectum and anus

What is a lumen

The inside of a tube in the gut that is considered continuous with external environment

what are the accessory organs

1. Salivary glands

2. Liver

3. Gall Bladder

4. Pancreas

What is the oral cavity

the mouth and pharynx; includes the tongue, teeth, spiglottis, and associated with salivary glands

What is the esophagus

The muscular tube connecting the pharynx to stomach '

The top is is skeletal muscle but it transitions to smooth muscle 2/3 of the way down

what is the esophageal sphincter

It closes off the phrarynx from the esophagus to prevent air from entering

What is the lower esophageal sphincter

It prevents materials in the stomach from entering the esophagus

What is the stomach

An expansible bag in the GI that can hold up to 2L of content

What are the parts of the stomach

1. Fundus → The top

2. Body → The middle

3. Antrum → The bottom

What is the pylorus?