F215:04:08 Three types of muscle Flashcards
Describe the composition of muscles
composed of cells that are elongated to form fibres
Why do all muscles produce a force on contraction?
Because they contain filaments made of the proteins actin and myosin
These protein filaments operate to cause contraction of voluntary muscle
What are the 3 types of muscle?
involuntary
cardiac
voluntary
What is another name for involuntary muscle?
smooth muscle
What is voluntary muscle often known as?
striated or skeletal muscles
Why is smooth muscle not under voluntary control?
As it is innrvated by neurones of the autonomic nervous system
Describe the arrangement of the muscle cells and the action carried out by involuntary muscles in the walls of the intestine
Arrangement: Circular and longitudinal bundles
Action: Peristalsis- moves food along the intestine
What is peristalsis?
Where food is moved along the intestine
Describe the arrangement of the muscle cells and the action carried out by involuntary muscles in the Iris of the eye
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
How does the involuntary muscle in the eye control the light intensity that enters the eye?
- Contraction of radial muscles dilates the pupil
- Contraction of circular muscle contricts the pupil
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
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
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?
- Contraction of muscle narrows vessel diameter so reducing blood flow
- Relaxatio causes dilation, increasing blood flow
Why are muscle cells referred to as being ‘spindle-shaped’?
As they contain small bundles of actin and myosin and a single nucleus
How long and wide are muscle cells when in a relaxed state?
5um wide
500um long
What two characteristics do involuntary muscles have?
The contraction is relatively slow
The muscle tires very slowly
Where is cardiac muscle found?
it forms the muscular part of the heart
What are the 3 types of cardiac muscle?
- atrial muscle
- ventricular muscle
- Specialised excitatory and conductive muscle fibres
What is the difference between the contractions of atrial and ventricular muscles, and skeletal muscles (cardiac muscles)
atrial and ventricular muscles have longer durations of contractions
Describe the excitatory and conductive fibres in cardiac muscle
they contact feebly but control electronic impulses and control the rhythmic heartbeat
What controls the rhythmic heartbeat and regulate the rate of contraction?
The excitatory and conductive fibres
Neurones of the autonomic system which carry impulses to the heart
What is a myogenic type of contraction?
Cardiac muscle which is capable of stimulating contraction without a nerve impulse
Where is the sinoatrial node found?
in the right wall of the atrium
What does sympathetic stimulation do and what kind of muscle does it effect?
increases the rate of the heart
cardiac muscle
What does parasympathetic stimulation do and what kind of muscle does it effect?
returns the heart muscle to its normal rate
What is the sinoatrial node made up of?
specialised excitatory and conductive fibres
What is the vital characteristic of the sinoatrial node?
It has self-excitation amd the electrical activity generated there immediately spreads into the atrial wall
What separates the atria and ventricles in the heart and why is it necessary?
a layer of non-conducting fibres
so the electrical activity can only spread to ventricles at the AV node
What does AV stand for?
atrioventricular
What is the role of the AV node?
It conducts the activity to the ventricle tips via the Purkyne fibres
Describe the composition of a cardiac muscle cell
they are made of many individual cells connected in rows
Separated by dark areas called intercalated discs, which are cell membranes
What are intercalated discs?
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
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?
To allow free diffusion of ions and so action potentials pass very easily and quickly between cardiac muscle fibres through the latticework of interconnections
Describe the way in which muscle fibres contract
Its continuous throughout its life
it contracts powerfully without fatigue
What is voluntary muscle necessary for?
the movement of the skeleton at joints
Describe the makeup of voluntary muscle cells, including its size
100um in diameter
contains many nuclei
Each fibre is surrounded by a cell surface membrane called a sarcolemma
What is a sarcolemma?
the cell surface membrane that surrounds each voluntary muscle fibre
What is cell muscle cytoplasm known as?
Sarcoplasm
Describe the organelles inside the sarcoplasm
- Many mitochondria
- Extensive sarcoplasmic reticulum
- Number of myofibrils
What are myofibrils?
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
What are sarcomeres?
the smallest contractile unit of a muscle
Makes up myofibrils
What are the two different types of protein myofilaments found in sarcomeres?
myosin and actin which run the length of the cell
Describe the contractions of voluntary muscle
It contracts quickly and powerfully but fatigues quickly
Describe the detail of the skeletal muscle, beginning with the muscle and ending with the myofibril
muscle tendon bundle of muscle fibres connective tissue muscle fibre myofibril
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?
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
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
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
What is the difference between involuntary, voluntary and cardiac muscle in terms of their appearance ?
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
What is the difference between involuntary, voluntary and cardiac muscle in terms of contraction?
Involuntary: contracts slowly , fatigues slowly
Voluntary: contracts quickly, fatigues quickly
Cardiac: contracts quickly, does not fatigue
What is the difference between involuntary, voluntary and cardiac muscle in terms of what controls their contractions?
Invol: Autonomic nervous system
Vol: Nervous system
Cardiac: Contraction is myogenic, autonomic nervous system controls the rate of contraction
What is the difference between involuntary, voluntary and cardiac muscle in terms of what they are involved in?
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
What is the difference between involuntary, voluntary and cardiac muscle in terms of its appearance under a microscope
Invol: unstriated
Vol: striated
Cardiac: striated
