Question

Part I – The Tour

You are an intern working in the Atlanta, GA office of Dr. Priya Wayne, MD. Dr. Wayne is a specialist in rare neuromuscular and musculoskeletal disorders. You’ve been working with Dr. Wayne for the last year and due to this experience you’ve gained a great deal of knowledge about the human body and muscle physiology. You’re also a college student and working with Dr. Wayne has allowed you to gain first-hand experience with some of the material that you’re learning in your human physiology course. Just last week you had to turn in an assignment comparing and contrasting disorders of the neuromuscular junction. You learned all about several issues, including myasthenia gravis, sarin, curare, botulism, and Eaton-Lambert syndrome.

Today a group of high school students is coming for a tour and Dr. Wayne has asked you to prepare some information about muscles to present to the students. Specifically, Dr. Wayne has asked you to discuss the neuromuscular junction (NMJ), skeletal muscle contraction, and explain some of the issues that can occur when signaling between neurons and muscles does not go as planned.

Questions

Use the word bank to match the appropriate letter to the definitions/descriptions on the next page.

(a) Sodium

(b) Nicotinic acetylcholine receptor (nACh) (c) Myosin

(d) Actin

(e) Acetylcholine (ACh)

(f) Depolarization

(g) Motor end plate

(h) Acetylcholinesterase (AChE)

(i) Synaptic vesicles

(j) T-tubule

(k) Sarcoplasmic reticulum (l) Dihydropyridine receptor (m) Ryanodine receptor

(n) Synaptic terminal

(o) Sarcolemma

(p) Sarcomere

*These four undergraduate students contributed equally to the creation of this case study and are listed in alphabetical order.

Case copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Originally published September 29, 2016. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work. Photograph by Victoria Garcia, Open Stax, <https://cnx.org/contents/[email protected]:mU03zyTM@2/Interactions-of-Skeletal-Muscl>, cc by 4.0.

NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE 1. ___ Thin contractile protein involved in cross-bridge formation, comes in filamentous or globular forms.

2. ___ Store neurotransmitters, and following a Ca2+ driven signal, dump neurotransmitters into the synapse.

3. ___ The structure at the end of the axon that contains neurotransmitters and vesicles.

4. ___ The functional unit of the muscle fiber that includes the A-band, I-band, H-zone and the M-line.

5. ___ The ion responsible for depolarizing the muscle membrane by traveling through the nACh receptor, down its electrochemical gradient.

6. ___ Located on the sarcoplasmic reticulum and once opened, allows Ca2+ flow from the sarcoplasmic reticulum into the sarcoplasm.

7. ___ Thick filamentous contractile protein involved in cross-bridge formation, has a club-like appearance with a “head.”

8. ___ A neurotransmitter derived from choline; responsible for sending the excitatory signal in the neuromuscular junction.

9. ___ These invaginations allow depolarization of the muscle membrane to quickly penetrate from the sarcolemma to the myofibril.

10. ___ Large and complex terminal formation by which an axon of a motor neuron establishes synaptic contact with a skeletal muscle fiber, transmitting neural impulses to a muscle.

11. ___ The plasma membrane of a muscle fiber.

12. ___ The enzyme responsible for stopping the ACh signal. Functions by metabolizing ACh into choline, which is recycled, and acetate.

13. ___ Responsible for opening a ligand-gated Na+/K+ channel in the muscle membrane when the proper ligand binds to it.

14. ___ A L-type calcium channel in the muscle cell membrane, activated upon depolarization, couple depolarization signal to release of calcium.

15. ___ An electrical change which brings the relative charge of the inside of the cell more positive; necessary for transmission of electrical impulses within a cell, or from one cell to another.

16. ___ Modified endoplasmic reticulum, stores and releases calcium.

Explain the organization/classifications of the Human Nervous System.

1. Which component(s) will be your main focus in this case study

Answer 1

Events at Neuromuscular junction are 1. Action potential arrives at axon terminal.

2. Voltage gated calcium channels open, calcium enters at axon terminal by moving the electro chemical gradient.

3. Acetylcholine releases by exocytosis. Ach diffuses across the synaptic cleft, binds to its receptors at sarcolemma.

4. This acetylcholine binding allows to open the ion channels in the receptors, which makes the sodium ions to diffuse into muscle fibre and potassium ions to move out of muscle fibre. This produces end plate potential.

5. Acetylcholinesterase breaks the acetylcholine effects at synaptic cleft.

1. Actin

2. Synaptic vesicles

3. Synaptic terminal

4. Sarcomere

5. Sodium

6. Ryanodine receptor

7. Myosin

8. Acetylcholine

9. T tubule

10. Motor end plate

11. Sarcolemma

12. Acetylcholinesterase

13. Nicotinic acetylcholine receptor

14. Dihydropyridine receptor

15. Depolarization

16. Sarcoplasmic reticulum

Classification of nervous system -

Ⅰ ⑴Peripheral nervous system. ⑵ Central nervous system

Ⅱ Peripheral nervous system is divided into 1.Autonomic nervous 2. Somatic nervous system.

⑴Autonomic nervous system is further divided into Sympathetic and Parasympathetic nervous system.

⑵ Central nervous system consists brain and spiral cord.

Brain is divided into 1. Forebrain

2.Midbrain

3.Hindbrain

① Forebrain contains 1. Telencephalon ( cerebral cortex, amygdala, hippocampus and basal ganglia )

2. Diencephalon ( Hypothalamus, thalamus )

②.Midbrain consists of Mesencephalon. ( Cerebellum )

③.Hindbrain contains Metencephalon ( Cerebellum and ponsHmyelencephalon.