Population living in one place form a

You measure levels of Ca2+ in various locations within a motor neuron and a skeletal muscle fiber when the motor neuron is NOT d

gogolik [260]

Answer:

The correct answer is 3: "High levels of Ca2+ are expected to be found within the sarcoplasmic reticulum".

Explanation:

Muscular contraction is a highly regulated process that depends on free calcium concentration in the cytoplasm. Amounts of cytoplasmic calcium are regulated by sarcoplasmic reticulum that functions as a storage of the ion.

When a nerve impulse reaches the membrane of a muscle fiber, through acetylcholine release, the membrane depolarizes producing the entrance of calcium from extracellular space. The impulse is transmitted along the membrane to the sarcoplasmic reticulum, from where calcium is released. At this point, tropomyosin is obstructing binding sites for myosin on the thin filament. The calcium channel in the sarcoplasmic reticulum controls the ion release, that activates and regulates muscle contraction, by increasing its cytoplasmic levels. When calcium binds to the troponin C, the troponin T alters the tropomyosin by moving it and then unblocks the binding sites, making possible the formation of cross-bridges between actin and myosin filaments. When myosin binds to the uncovered actin-binding sites, ATP is transformed into ADP and inorganic phosphate.

Z-bands are then pulled toward each other, thus shortening the sarcomere and the I-band, and producing muscle fiber contraction.

4 0

3 years ago

Give importances of locomotion in man

zheka24 [161]

Answer:

Locomotion is essential for various internal and external bodily functions

Explanation:

Locomotion is the art through which our body exhibit various functions and also escapes various condition of environment.

For instance –

a) Through movement of limbs, actions such as running, walking, jumping, crawling, swimming, etc are performed.

b) Movement of body parts and joints helps in taking different comfortable postures.

c) Even some body parts move even when it is not essentially vital for the function being performed such as movement of eyeball and external ear while swallowing food.

d) Movement of nutrients and blood with in the circulation system and digestive system.

e) Movement of sense organs when exposed to extreme environmental conditions.

7 0

3 years ago

The anterior portion of the body of most annelids, such as the earthworm, is adapted for sensing the environment.

Diano4ka-milaya [45]

Answer:

The answer is False. Although sensitive cells are more abundant in the anterior portion of the annelid´s body, in general, they are arranged in all the segments.

Explanation:

Annelids, such as the earthworm, have a variety of sensory cells:

Mechanoreceptors, disposed of in groups in each segment of their body.

Photoreceptors: Light-sensitive cells. Although they are located in the whole body, they are abundant in anterior and posterior segments, concentrated in the intern and dorsal part of the epidermis.

Humidity receptors are the most sensitive cells and are located in the first segments of the earthworm body

Chemoreceptors: sensorial cells cumulus forming a prominent tubercle with prolongations that extends through the cuticle. These tubercles form three rings in each segment but are especially abundant in the anterior part of the body.

The tegument is very rich in free nervous terminations, which functions might be tactile.

6 0

3 years ago

Even though he added an extra strand to the structure of dna he ultimately won two nobel prizes

pantera1 [17]

Linus Pauling

Hope this helped. Good luck!

7 0

3 years ago

Plz help I need the answer fast

cupoosta [38]

the answer is the second one how appearance of an organism and its structure

8 0

3 years ago