F215:04:08 Three types of muscle

Question 1

Describe the composition of muscles

Answer 1

composed of cells that are elongated to form fibres

Question 2

Why do all muscles produce a force on contraction?

Answer 2

Because they contain filaments made of the proteins actin and myosin
These protein filaments operate to cause contraction of voluntary muscle

Question 3

What are the 3 types of muscle?

Answer 3

involuntary
cardiac
voluntary

Question 4

What is another name for involuntary muscle?

Answer 4

smooth muscle

Question 5

What is voluntary muscle often known as?

Answer 5

striated or skeletal muscles

Question 6

Why is smooth muscle not under voluntary control?

Answer 6

As it is innrvated by neurones of the autonomic nervous system

Question 7

Describe the arrangement of the muscle cells and the action carried out by involuntary muscles in the walls of the intestine

Answer 7

Arrangement: Circular and longitudinal bundles
Action: Peristalsis- moves food along the intestine

Question 8

What is peristalsis?

Answer 8

Where food is moved along the intestine

Question 9

Describe the arrangement of the muscle cells and the action carried out by involuntary muscles in the Iris of the eye

Answer 9

Circular and radial bundles
Controls the light intensity of light entering the eye:
- Contraction of radial muscles dilates the pupil
- Contraction of circular muscle contricts the pupil

Question 10

How does the involuntary muscle in the eye control the light intensity that enters the eye?

Answer 10

• Contraction of radial muscles dilates the pupil

- Contraction of circular muscle contricts the pupil

Question 11

Describe the arrangement of the muscle cells and the action carried out by involuntary muscles in the wall of the arteries and around arterioles; wall and cervix of the uterus

Answer 11

Circular bundles
Important in temp regulation, regulation of local blood pressure and the redirecting of blood to voluntary muscles during exercise:
- Contraction of muscle narrows vessel diameter so reducing blood flow
- Relaxatio causes dilation, increasing blood flow

Question 12

How do involuntary muscles in the wall of the arteries and around arterioles carry out their role in temp regulation, regulation of local blood pressure and the redirecting of blood to voluntary muscles during exercise?

Answer 12

• Contraction of muscle narrows vessel diameter so reducing blood flow
• Relaxatio causes dilation, increasing blood flow

Question 13

Why are muscle cells referred to as being ‘spindle-shaped’?

Answer 13

As they contain small bundles of actin and myosin and a single nucleus

Question 14

How long and wide are muscle cells when in a relaxed state?

Answer 14

5um wide

500um long

Question 15

What two characteristics do involuntary muscles have?

Answer 15

The contraction is relatively slow

The muscle tires very slowly

Question 16

Where is cardiac muscle found?

Answer 16

it forms the muscular part of the heart

Question 17

What are the 3 types of cardiac muscle?

Answer 17

1. atrial muscle
2. ventricular muscle
3. Specialised excitatory and conductive muscle fibres

Question 18

What is the difference between the contractions of atrial and ventricular muscles, and skeletal muscles (cardiac muscles)

Answer 18

atrial and ventricular muscles have longer durations of contractions

Question 19

Describe the excitatory and conductive fibres in cardiac muscle

Answer 19

they contact feebly but control electronic impulses and control the rhythmic heartbeat

Question 20

What controls the rhythmic heartbeat and regulate the rate of contraction?

Answer 20

The excitatory and conductive fibres

Neurones of the autonomic system which carry impulses to the heart

Question 21

What is a myogenic type of contraction?

Answer 21

Cardiac muscle which is capable of stimulating contraction without a nerve impulse

Question 22

Where is the sinoatrial node found?

Answer 22

in the right wall of the atrium

Question 23

What does sympathetic stimulation do and what kind of muscle does it effect?

Answer 23

increases the rate of the heart

cardiac muscle

Question 24

What does parasympathetic stimulation do and what kind of muscle does it effect?

Answer 24

returns the heart muscle to its normal rate

Question 25

What is the sinoatrial node made up of?

Answer 25

specialised excitatory and conductive fibres

Question 26

What is the vital characteristic of the sinoatrial node?

Answer 26

It has self-excitation amd the electrical activity generated there immediately spreads into the atrial wall

Question 27

What separates the atria and ventricles in the heart and why is it necessary?

Answer 27

a layer of non-conducting fibres | so the electrical activity can only spread to ventricles at the AV node

Question 28

What does AV stand for?

Answer 28

atrioventricular

Question 29

What is the role of the AV node?

Answer 29

It conducts the activity to the ventricle tips via the Purkyne fibres

Question 30

Describe the composition of a cardiac muscle cell

Answer 30

they are made of many individual cells connected in rows | Separated by dark areas called intercalated discs, which are cell membranes

Question 31

What are intercalated discs?

Answer 31

Cell membranes that divide the individual cells in cardiac muscle fibres They fuse in such a way that there are gap junctions with free diffusion of ions and so action potentials pass very easily and quickly between cardiac muscle fibres through the latticework of interconnections

Question 32

Why are there gap junctions between the individual cells in cardiac muscle fibres that fuse in a way that there are gap junctions between them?

Answer 32

To allow free diffusion of ions and so action potentials pass very easily and quickly between cardiac muscle fibres through the latticework of interconnections

Question 33

Describe the way in which muscle fibres contract

Answer 33

Its continuous throughout its life | it contracts powerfully without fatigue

Question 34

What is voluntary muscle necessary for?

Answer 34

the movement of the skeleton at joints

Question 35

Describe the makeup of voluntary muscle cells, including its size

Answer 35

100um in diameter contains many nuclei Each fibre is surrounded by a cell surface membrane called a sarcolemma

Question 36

What is a sarcolemma?

Answer 36

the cell surface membrane that surrounds each voluntary muscle fibre

Question 37

What is cell muscle cytoplasm known as?

Answer 37

Sarcoplasm

Question 38

Describe the organelles inside the sarcoplasm

Answer 38

- Many mitochondria - Extensive sarcoplasmic reticulum - Number of myofibrils

Question 39

What are myofibrils?

Answer 39

contractile elements and each consists of smaller contractile units called sarcomeres Within the myofibrils are two types of protein myofilaments- thin actin and thick myosin

Question 40

What are sarcomeres?

Answer 40

the smallest contractile unit of a muscle | Makes up myofibrils

Question 41

What are the two different types of protein myofilaments found in sarcomeres?

Answer 41

myosin and actin which run the length of the cell

Question 42

Describe the contractions of voluntary muscle

Answer 42

It contracts quickly and powerfully but fatigues quickly

Question 43

Describe the detail of the skeletal muscle, beginning with the muscle and ending with the myofibril

Answer 43

``` muscle tendon bundle of muscle fibres connective tissue muscle fibre myofibril ```

Question 44

Blood vessels such as arterioles contain circular smooth muscle. Contraction of this muscle constricts the vessel. Why do blood vessels not need longitudinal muscle to act against the circular muscle in order to cause dilation?

Answer 44

Circular muscles are needed in order to constrict the blood vessels; however, the dilation of the blood vessels is achieved by relaxation of the circular muscles only, because the pressure of the blood in the vessel dilates the vessel- effectively the force for dilation is derived from the pumping of blood by the heart

Question 45

Suggest the advantage of the electrical activity of the heart being able to pass from atria walls to ventricle walls only at the AV node

Answer 45

It is essential that the ventricles contract smoothly from the apex upwards, so if the electrical activity passed from atrial walls to ventricular walls, they would begin contracting from the top downwards - It is also essential to allow full contraction of atrial walls, pushing the blood into the ventricles before ventricular contraction begins - So the impulse only being able to pass via the AV node introduces a short delay which allows full atrial contraction before ventricular contraction begins

Question 46

What is the difference between involuntary, voluntary and cardiac muscle in terms of their appearance ?

Answer 46

involuntary: short spindle shaped cells, each with a single nucleus Voluntary: Cells form long multinucleate fibres cardiac: Cells form branched fibres with intercalated discs joining cells at their ends

Question 47

What is the difference between involuntary, voluntary and cardiac muscle in terms of contraction?

Answer 47

Involuntary: contracts slowly , fatigues slowly Voluntary: contracts quickly, fatigues quickly Cardiac: contracts quickly, does not fatigue

Question 48

What is the difference between involuntary, voluntary and cardiac muscle in terms of what controls their contractions?

Answer 48

Invol: Autonomic nervous system Vol: Nervous system Cardiac: Contraction is myogenic, autonomic nervous system controls the rate of contraction

Question 49

What is the difference between involuntary, voluntary and cardiac muscle in terms of what they are involved in?

Answer 49

Invol: movement of materials along internal tubes, e.g. gut and autonomic reflexes such as pupil dilation/constriction Vol: Voluntary movements of bones of the skeleton about the joints Cardiac: pumping blood round the body

Question 50

What is the difference between involuntary, voluntary and cardiac muscle in terms of its appearance under a microscope

Answer 50

Invol: unstriated Vol: striated Cardiac: striated