Week 5

Question 1

Briefly summarise the primary tissues.

Answer 1

Epithelial tissues: forms layers that line or cover body structures, cavities and organs

Connective tissues: cells are widely spaced and separated by extracellular matrix

Nerve: fast communication cells

Muscle: contractile cells able to adapts in shape to generate movement

Question 2

Briefly explain the key features of skeletal muscle tissue (e.g. function, structure)

Answer 2

• consists of long, cylindrical, striated fibres.
• fibres vary greatly in length, from a few cms in short muscles to 30-40cm in the longest muscles
• fibre is roughly cylindrical, multi nucleated cell with nuclei at the periphery
• considered voluntary because it can be made to contract or relax by conscious control
• usually attached to bones by tendons
• FUNCTION: motion, posture, heat production, protection

Question 3

Briefly explain key features of cardiac muscle tissue.

Answer 3

• consists of branched, striated fibres with usually only one centrally located nucleus
• attach end to end by transverse thickenings of plasma membrane called Intercalated Discs, which contains desmosomes and gap junctions
• desmosomes strengthen tissue and hold fibres together during vigorous contractions
• gap junctions provide route for quick conduction of electrical signals throughout heart
• involuntary (not conscious control)
• location: heart wall
• FUNCTION - pumps blood to all parts of body

Question 4

Briefly explain key features of smooth muscle tissue.

Answer 4

• consists of fibres usually involuntary, nonstriated
• small spindle-shaped cell thickest in middle, tapering at each end, and containing a single centrally located nucleus
• gap junctions connect many individuals fibres
• can produce powerful contractions as many muscle fibres contract in unsion
• location: iris of eyes; walls of hollow internal structures such as blood vessels, airways to lungs, stomach, intestines, gall bladder, urinary bladder & uterus
• FUNCTION: Motion - constriction of blood vessels and airways, propulsion of foods through gastrointestinal tract, contraction of urinary bladder and gall bladder

Question 5

What are the 4 key functions of muscle tissue?

Answer 5

• Producing body movement- movements of the whole body and localised movements rely on integrated functioning skeletal muscles, bones and joints
• Stabilising body positions - skeletal muscle contractions stabilise joints and help maintain body positions (standing or sitting)
• Storing and moving substances within the body - accomplished by sustained contractions of ring like bands of smooth muscle called sphincters, which prevent outflow of the contents of hollow organ
• Generating heat: muscular tissue contraction produces heat by thermogenesis - used to maintain normal body temperature

Question 6

What are the 4 main properties of muscular tissue?

Answer 6

1. Electrical excitability: the ability to respond to certain stimuli by producing action potentials. Stimuli can arise from autorhythmic electrical signals from muscular tissue itself or chemical stimuli (neurotransmitters, hormones, local changes in pH)
2. Contractility - the ability to contract forcefully when stimulated by action potential
3. Extensibility - the ability of muscular tissue to stretch , within limits, without being damaged.
4. Elasticity - the ability of muscular tissue to return to its original length and shape after contraction or extension

Question 7

Fascicles (many muscle fibres bundled together) are associated with Connective Tissues. Elaborate further on this.

Answer 7

Epimysium: outer layer and surrounds the whole muscle; dense irregular CT

Perimysium: surrounds and supports the fibres forming the fascicle; dense irregular CT

Endomysium - surrounds the muscle fibre; reticular CT

Question 8

How are muscle fibres formed?

Answer 8

Formed by fusion of many myoblasts in development. This is why muscle fibres have multiple nuclei on the periphery of the cell. (also because if the nuclei was in the middle it would impair the ability to contract)

Question 9

What are myofibrils?

Answer 9

Myofilaments are bundled together to from complex organelles; form the structural and functional subunits of muscle fibre

Question 10

What is the sarcolemma

Answer 10

The plasma membrane of a muscle cell.

Question 11

What is the sarcoplasm?

Answer 11

The cytoplasm. Includes Glycogen (composed of many glucose molecules and used for synthesis of ATP)

Question 12

What are transverse (T) tubules?

Answer 12

Invaginations of the sarcolemma which tunnel in from surface towards the centre of each muscle fibre.

Question 13

What are are myoglobin proteins?

Answer 13

Releases oxygen when it is needed by mitochondria for ATP production.

Question 14

What is the sarcoplasmic reticulum?

Answer 14

Fluid-filled system of membranous sacs that encircles each myofibril.

Question 15

What are terminal cisterns?

Answer 15

Dilated end sacs of the SR

Question 16

What is a triad?

Answer 16

A transverse tubule and the two terminal cisterns on either side of it form a triad.

Question 17

What are Z discs

Answer 17

Narrow plate-shaped regions of dense material that separate one sarcomere from the rest.

Question 18

What are A bands?

Answer 18

Dark, middle part of sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments.

Question 19

What are the I band?

Answer 19

Light, less dense area of sarcomeres that contains remainder of thin filaments but no thick filaments. A Z disc passes through centre of each band.

Question 20

What is the H zone?

Answer 20

Narrow region in centre of each A band that contains thick filaments but no thin filaments.

Question 21

What is the M line?

Answer 21

Region in centre of H zone that contains proteins that hold thick filaments together at centre of sarcomere.

Question 22

Myofibrils are built from 3 kinds of proteins. What are they and what do they do?

Answer 22

1. Contractile proteins which generate force during contraction (actin and myosin)
2. Regulatory proteins which help switch the contraction process on & off (Troponin and tropomyosin)
3. Structural proteins: which keep thick and thin filaments in proper aligmnet, give the myofibril elasticity and extensibility and link the myofibrils to the sarcolemma and ECM (Titn, a-actinin, Myomesin, Nebulin and dystrophin)

Question 23

What is the structure of thick filaments

Answer 23

Myosin is main component of thick filament and functions as motor protein in all 3 types of muscle tissue

Each myosin molecule is shaped like two golf clubs twisted together. Myosin tails form the shaft of te filament, and myosin heads projects outward towards the surrounding thin filaments.

Question 24

What is the structure of thin filaments?

Answer 24

Contain actin, troponin and tropomyosin. Contracticle protein Actin generate force during contraction; regulatory proteins help switch contraction on and off.

Question 25

Briefly explain the 3 main types of muscle fibres.

Answer 25

Slow oxidative (SO) fibres: slow-twitch, fatigue resistant fibres (shoulder, neck, back muscle/deep leg muscle).

Fast oxidative-glycolytic fibres: largest fibres with high resistance to fatigue (superficial leg)

Fast glycolytic fibres: contract strongly and quickly and are adapted for intense anaerobic movements of short duration, but they fatigue quickly (shoulder, arms)

Question 26

Tell me what makes up slow oxidative muscle fibre and what they are used for?

Answer 26

• Slow oxidative fibres appear dark red, contain large amounts of Myoglobin, many blood capillaries and many large mitochondria.
• They generate ATP mainly by aerobic respiration, hence called Oxidative fibres.
• These slow-twitch, fatigue resistant fibres are adapted for maintaining posture and for aerobic endurance-type activites

Question 27

Fast oxidative-glycolytic fibres. Explain what they are in depth.

Answer 27

• Typically largest fibres containing large amounts of Myoglobin and many blood capillaries
• Can generate considerable ATP by aerobic respiration, which gives them a moderately high resistance o fatigue
• FOG fibres are fast because the ATPase in their myosin heads hydrolyses ATP 3 to 5 times faster than the myosin
• FOG fibres contribute to activities such as walking and sprinting

Question 28

Talk about fast glycolytic fibres in depth, please. Cheers cob.

Answer 28

• Have a low myoglobin content, few blood capillaries and few mitochondria and appear white in colour.
• Contain large amounts of glycogen and generate ATP mainly by glycolysis.
• FG fibres contract strongly and quickly and are adapted for intense anaerobic movements of short duration, such as weight lifting or throwing a ball, but they fatigue quickly.

Question 29

What is creatine phosphate? Where is it synthesised and how much energy does it give the muscles to contract?

Answer 29

Synthesised in liver, kidneys, and pancreas and then transported to muscle fibres. First source of energy when muscle contraction begins; transfers a high-energy phosphate group to ADP, forming ATP during muscle contraction. Enough energy for muscles to contract maximally for about 15 sec.

Question 30

What is Anaerobic glycolysis?

Answer 30

Breakdown of muscle Glycogen into Glucose and production of Pyruvic
acid from glucose via Glycolysis produce both ATP & lactic acid. Because no oxygen is needed,
this is an anaerobic pathway.
‐ During heavy exercise not enough oxygen is available to skeletal muscle fibres. Under these
anaerobic conditions, the pyruvic acid generated from glycolysis is converted to lactic acid.
‐ Each molecule of Glucose catabolised via anaerobic glycolysis yields 2 molecules of lactic
acid and 2 molecules of ATP.
‐ Enough energy for about 2 min of maximal muscle activity.

Question 31

What is aerobic respiration?

Answer 31

Aerobic respiration: Within mitochondria, pyruvic acid, fatty acids & amino acids are used to
produce ATP via Aerobic respiration‐ a series of oxygen‐requiring reactions (Krebs cycle &
Electron transport chain) that produce ATP, carbon dioxide, water & heat.
‐ Each molecule of glucose catabolised under aerobic conditions yields about 30 or 32 molecules
of ATP.
During a long‐term event such as a marathon race, most ATP is produced aerobically