Question

Q1) Soon after a sugary meal, ______ cells in the pancreatic islets (islets of Langerhans) secrete ____.

1. Alpha; insulin
2. Alpha; glucagon
3. Beta; insulin
4. Beta; glucagon
5. None of these.

Q2)

what is the physiological significance of the skeletal muscle fiber triad relationship?

1. The t-tubules conduct electrical impulses that stimulate calcium release from the sarcoplasmic reticulum.
2. The t-tubules bring calcium to the sarcoplasmic reticulum.
3. The terminal cisternae subdivide the sarcolemma.
4. The sarcoplasmic reticulum transfer calcium to the t-tubules.
5. None of these

Q3)   Which of these happens fourth in an adrenergic synaptic transmission?

1. ATP is converted to cyclic AMP
2. Adenylate cyclase is activated
3. G protein dissociates from the NE receptor
4. G protein binds to adenylate cyclase
5. Cyclic AMP induces several effects in the cell

Q4)  ____ is the only sense in which signals can reach the cerebral cortex through second order sensory neurons.

1. Equilibrium
2. Vision
3. Touch
4. Smell
5. Taste
6. None of these

Q5) During the muscle contraction ______.

1. The A-bands get smaller
2. The H zone becomes more obvious
3. The Z-discs get pulled away from the A bands
4. The I-bands get smaller
5. None of these

Answer 1

Ans 1) Soon after a sugary meal,beta cells in the pancreatic islets (islets of Langerhans) secrete insulin which helps  to lower the blood sugar

Ans 2. The t-tubules conduct electrical impulses that stimulate calcium release from the sarcoplasmic reticulum.

Sarcotubular system is a system of membranous structures in the form of vesicles and tubules in the sarco plasm of the muscle fiber.

Sarcotubular system is formed mainly by two types of structures: 1. T tubules 2. L tubules

Ttubules or transverse tubules are narrow tubules formed by the invagination of the sarcolemma. These tubules penetrate all the way from one side of the muscle fiber to an another side. Because of their origin from sarcolemma, the Ttubules open to the exterior of the muscle cell. Therefore, the ECF runs through their lumen.

L-Tubules or  longitudinal tubules are the closed tubules that run in long axis of the muscle fiber, forming sarcoplasmic reticulum. These tubules form a closed tubular system around each myofibril and do not open to exterior like Ttubules.

At regular intervals, throughout the length of the myofibrils, the L-tubules dilate to form a pair of lateral sacs called terminal cisternae. Each pair of terminal cisternae is in close contact with Ttubule.

The T tubule along with the cisternae on either side is called the triad of skeletal muscle.

Function of T-Tubules ---- T tubules are responsible for rapid transmission of impulse in the form of action potential from sarcolemma to the myofibrils. When muscle is stimulated, the action potential develops in sarcolemma and spreads through it.

Function of L-Tubules L tubules store a large quantity of calcium ions. When action potential reaches the cisternae of L tubule, the calcium ions are released into the sarcoplasm. Calcium ions trigger the processes involved in contraction of the muscle.

Ans 3  d .ATP is converted to cyclic AMP

Sequence of events

a. G protein dissociates from the NE receptor

b. G protein binds to adenylate cyclase

c. Adenylate cyclase is activated

d .ATP is converted to cyclic AMP

e. Cyclic AMP induces several effects in the cell

Ans 4.  Smell is the only sense in which signals can reach the cerebral cortex through second order sensory neurons.

Ans 5. 2. Length of the ‘I’ band decreases since the actin filaments from opposite side overlap

Changes in sarcomere during muscular contractionThus, changes that take place in sarcomere during muscular contraction are:

1. Length of all the sarcomeres decreases as the ‘Z’ lines come close to each other

2. Length of the ‘I’ band decreases since the actin filaments from opposite side overlap

3. ‘H’ zone either decreases or disappears

4. Length of ‘A’ band remains the same