Muscle Flashcards
Define cardiac muscle.
Muscle found in the heart walls
Define involuntary muscle.
Smooth muscle that contracts without conscious control.
What is a neuromuscular junction?
The structure at which a nerve meets the muscle; it is similar in action to a synapse.
What is skeletal (striated) muscle?
Muscle under voluntary control.
Describe the features of muscle.
Muscle are composed of cells arranged to form fibres. These fibres can contract to become shorter, which produces a force.
How is contraction achieved?
By interaction between two protein filaments (actin and myosin) in the muscle cells.
What are the three types of muscle?
Involuntary (smooth)
Cardiac
Voluntary (skeletal or striated muscle)
Describe involuntary (smooth) muscle cells.
Consists of individual cells, tapered at both ends (spindle shaped). Each cell contains a nucleus and bundles of actin and myosin.
What are the features of involuntary muscle?
This type of muscle contracts slowly and regularly. It does not tire quickly. it is controlled by the ANS.
Where is involuntary muscle found?
Involuntary muscle is found in the walls of the tubular structures, such as the digestive system and blood vessels. The muscle is usually arranged longitudinally and circular layers that oppose each other.
Describe be the structure of cardiac muscle.
The individual cells form long fibres, which branch to form cross bridges between the fibres.
What do the cross bridges in cardiac muscle do?
Help to ensure that electrical stimulation spreads evenly over the walls of the chambers.
During contraction this also helps to ensure that the contraction is a squeezing action rather than one-dimensional.
How are cardiac muscle cells joined?
By intercalated discs
What are intercalated discs?
Specialised cell surface membranes fused to produce gap junctions that allow free diffusion of ions between the cells. Action potentials pass easily and quickly along and between the cardiac muscle fibres.
Give some characteristics of cardiac muscle.
It can contract and relax continuously throughout life.
It can contract powerfully and does not fatigue easily. Some muscle fibres in the heart are modified to carry electrical impulses (purkyne fibres).
