HISTOLOGY - Skeletal Muscle & Nerve Tissue Lecture

Question 1

What are the three muscle types

Answer 1

Skeletal – striated and voluntary Cardiac – striated, involuntary Smooth – non striated and involuntary

Question 2

Describe the following:

1) Myocytes
2) Endomysium
3) Fascicles
4) Perimysium
5) Epimysium

Answer 2

1) mytocytes - skeletal mucles cells (aka myofiber/muscle fibers)
2) endomysium - membrane that seperate monocytes
3) fascicles - groups of myocytes
4) perimysium - membrane that seperates fascicles
5) epimysium - membrane that surrounds the entire muscle

From interior to exterior = 1 –> 2 –> 3 –> 4 –> 5

Question 3

Answer 3

a -Epimysium

b -Perimysium

c - Endomysium

d -Muscle fiber in middle of fascicle

Question 4

Answer 4

A - transverse

B - longitudinal

Question 5

What is a sarcomere?

Answer 5

The smallest unit of a muscle

The contractile unit of muscle made of actin and myosin

Question 6

What are the functions of the following sarcomere structural units?

1) Z-line
2) I-band
3) M-line
4) H-zone
5) A-band

Answer 6

Z-line = the anchor site for actin (thin) microfilaments

I-band = an area containing only actin (thin) microfilaments

M-line = anchor site for thick myosin filaments

H-zone = contains only thick myosin filaments

A-band = overlap of thick and thin filaments

Question 7

Where does a sarcomere extend from?

Answer 7

One Z-line to the next Z-line

Question 8

Answer 8

a - Z-line

b -myosin filament (thick)

c - actin filament (thin)

d - I-band

e - A band

F - I-band

g - H-zone

Question 9

Question 10

Skeletal muscle cells are…

Answer 10

multinucleated (located on peripohery of cell) and fused together from myoblasts

Question 11

What is a sarcolemma? What are transverse tubules?

Answer 11

• a plasma membrane surrounding a skeletal muscle cell
• invaginations of the sarcolemma that play a key role in continuing and action potential to the sarcoplasmic reticulum. Also play key role in moving calcium

Question 12

What is sarcoplasmic reticulum?

Answer 12

A specialized type of endoplasmic reticulum in muscle cells that functions primarily to store Ca2+ ions for muscle contraction — reabsorbs Ca2+ once used

Question 13

What are Terminal Cisternae?

Answer 13

The distal ends of the SR that release Ca2+, triggering muscle contraction

Question 14

Explain the Sliding Filament Mechanism during contraction?

Answer 14

1) During contraction, thin and thick filaments slide past one another bringing the Z-lines closer together
2) There is no change in the size of the actin or myosin filaments during this process — ONLY THE DEGREE OF OVERLAP

Question 15

Explain the regulatory proteins 1) Tryptomyosin and 2) Tryponin and what they do

Answer 15

Tryptomyosin - lies in groove between actin filaments and muscler tissue, resposible for blocking cross-bridge sites ON ACTIN during relaxation, preventing contraction (CONTRACTION INHIBITOR)

Troponin

Troponin T - Binds troponin complex to tryptomyosin

Troponin I - inhibnits the binding of myosin heads with actin

Troponin C - Binds to Ca2+, revealing the cross-bridge sites on actimnm via conformational change in Troponin I

Question 16

Why are myosin heads important for muscle contraction?

Answer 16

They have ATP binding sites that start contraction and a binding site for attaching to actin cross-bridge sites

Question 17

What are the steps of muscle contraction?

Answer 17

1) Neuron gives signal to contract
2) ATP becomes bound to mysoin head and is hydrolyzed
3) Myosin head extends to attached to actin cross-bridge site once calcium reveals the sites (see calcium importance steps
4) “Powerstroke” action is initiated and the myosin head pulls the actin toward the m-line, shortening the distance between the z-lines
5) ADP released during process, another is needed to either continue contraction, increase contraction or release contraction

Question 18

Explain the importance of calcium in muscle contraction?

Answer 18

Ca2+ controls muscle contraction

1) Ca2+ is held in SR and is released following signal from neuron
2) Signal travels down the sarcolemma and the T-tubules release the Ca2+
3) Ca2+ binds to troponin C in the presence of enough ATP, which induces confirmational change that movews the tryptomyosin, exposing the cross-bridge sites

Question 19

How are muscle fibers catagorized?

Answer 19

1) Type of contraction (power, speed, duration)
2) ATP supply (anaerobic, aerobic)

Question 20

Explain:

Type I Fibers

Type IIa Fibers

Type IIb Fibers

Answer 20

Type I (slow, oxidative) —- marathon runners

-Very red due to myoglobin, many mitochondria, slow ATPase, contract slowly and for long periods without fatigue

Type IIa (oxidative-glycolytic)

-Primarily aerobic, most abundant in body, some mitochiondria, intermediate ATPase, PROVIDES POWER

Type IIb (Fast glycolytic) —- weight lifters

-Primarily anaerobic, Fast ATPase, fatigue quickly, few myoglobin and mitochondria

Question 21

Whata re the name of neurons in CNS vs PNS

Answer 21

CNS = nuclei

PNS = ganglia

Question 22

Whata re the two type of cells in nerve tissue?

Answer 22

Neurons - comnduct electrical impulses

neuroglia - neuron supporting cells (myelinate, protect)

Question 23

What is Nissl Substance?

Answer 23

A substance consiting of many granular endoplasmic reticulum and ribosomes which strongly adhere to stains in histology

Many are present in neurons becauses they need to make a lot of protein/neurotransmitters in order to span through the body

Question 24

What are the basic components of a nerve cell?

Answer 24

Cell body - processess electical info

Axon - transmits electrical info/carry signal away fromc cell body

Dendrites - recieve signal/carries toward cell body

Synapse - point where electric signals are transmitted from an axon terminal to an effector cell

Schwann cells - myelinate the axons in the PNS

Question 25

What are the three anatomical classificatiomns of neurons?

Answer 25

1) Multipolar - one axon, many dendrites (MOST COMMON) 2) Bipolar - one axon, one dendrite (Retina) 3) Unipolar - one cell process with a branch thay has one axon and one dendrite (Dorsal Root Ganglia)

Question 26

What are satellite cells

Answer 26

Cells that cover neurons and are responsible for maintaining and regulating the environmenta around the neuron

Question 27

What is the importance of myelin sheaths and the process of mylination?

Answer 27

Improves speed of signal transmission via Nodes of Ranvier (hops from node to node) Oligodendrocytes (CNS) or Schwann cells (PNS) wrap around axons repeatedly until they form a myelin membrane Axons can be be myelinated OR unmyelinated

Question 28

What are the three important structures of a peripheral nerve cell?

Answer 28

Endoneurium - CT between/surounding axons (COVERS AXONS) Perineurium - CT surrounding clusters of axons, forming fascicles (COVERS FASCICLES) Epineurium - CT surrounding several nerve fascicles (COVERS ENTIRE NERVE)

Question 29

Answer 29

A - Perinurium B - Epineurium C - Fascicle

Question 30

What is this?

Answer 30

A X-section of a peripheral nerve cell

Question 31

What are the 4 essential parts of a the chemical synapse?

Answer 31

1) Presynaptic knob (axon terminal) --- Has vesicles that release neurotransmitter in synaptic cleft 2) Synaptic cleft - space between neurons which continues signal via neurotransmitters 3) Presynaptic membrane 4) Postsynaptic membrame

Question 32

Explain what happens are the neuromuscular junction that stimulates muscle contraction?

Answer 32

1) Nerve impulse stimulates release of Acetylcholine (ACh) into synaptic cleft 2) ACh stimulates sarcolemma which excites the muscle and iscarried down to T-tubules to initiate contraction (Ca2+ release) 3) Enzymes break down ACh to limit action to 1 muscle twitch KEY: every skeletal muscle cell has an axon terminal but not all cardiac or smooth muscle cell is directly innervated

Question 33

What are muscle spindle receptors?

Answer 33

Monitor changes in length, rate of change (Stretch and speed) Prevents you from overstretching the muscle and contracting too fast SENDS REFLEX signal to spinal cord saying tnot to stretch any further

Question 34

How many schwann cells and oligodendrocytes are there comopared to neurons?

Answer 34

Schwann cells - one cell to one neuron Oligodendrocytes - one cell to many neurons

Question 35

What are the two types of Muscle Spindle Receptors?

Answer 35

1) Intrafusal Fibers - inside muscle spindle a) Nuclear Bag Fibers -- wrapped at center by type Ia nerve fibers, monitor change in length and degree of tension b) Nuclear chain fibers -- wrapped at ends by Type II nerve fibers, detect static muscle length 2) Extrafusal Fibers - outside muscle spindle (alpha motor fibers)

Question 36

What are golgi tendon organs?

Answer 36

Located in at the origins and insertions of muscle tendons, they are proprioreceptive sensory organs that sense changes in muscle tension When you lift weights, golgi tells how much you are exerting and will prevent further contraction to prevent injury