sinoatrial node

Examples of sinoatrial node in the following topics:

• Characteristics of Mammals

  • Mammals also have a specialized group of cardiac fibers located in the walls of their right atrium called the sinoatrial node, or pacemaker, which determines the rate at which the heart beats.

• The Cardiac Cycle

  • The internal pacemaker starts at the sinoatrial (SA) node, which is located near the wall of the right atrium.
  • Electrical charges spontaneously pulse from the SA node, causing the two atria to contract in unison.
  • The pulse reaches a second node, the atrioventricular (AV) node, between the right atrium and right ventricle, where it pauses for approximately 0.1 seconds before spreading to the walls of the ventricles.
  • The signal is initiated at the sinoatrial valve.
  • Summarize the caridac cycle and explain the role of the SA node and the AV node in regulating the its rhythm

• Functions of Stems

  • Nodes are points of attachment for leaves, aerial roots, and flowers.
  • The stem region between two nodes is called an internode.
  • Leaves are attached to the plant stem at areas called nodes.
  • An internode is the stem region between two nodes.
  • The leaves just above the nodes arise from axillary buds.

• Cytotoxic T Lymphocytes and Mucosal Surfaces

  • Lymph nodes scattered throughout the body house large populations of T and B cells, dendritic cells, and macrophages .
  • These antigens are filtered through lymph nodes before the lymph is returned to circulation.
  • Functionally, the spleen is to the blood as lymph nodes are to the lymph.
  • The liquid passes through (b) lymph nodes that filter the lymph that enters the node through afferent vessels, leaving through efferent vessels.
  • Lymph nodes are filled with lymphocytes that purge infecting cells.

• Nerve Impulse Transmission within a Neuron: Action Potential

  • A node of Ranvier is a natural gap in the myelin sheath along the axon .
  • Action potential "jumps" from one node to the next in saltatory conduction.
  • Nodes of Ranvier also save energy for the neuron since the channels only need to be present at the nodes and not along the entire axon.
  • Nodes of Ranvier are gaps in myelin coverage along axons.
  • Nodes contain voltage-gated K+ and Na+ channels.

• Stem Modifications

  • A rhizome is a modified stem that grows horizontally underground; it has nodes and internodes.
  • Stolons are stems that run almost parallel to the ground, or just below the surface, and can give rise to new plants at the nodes.
  • Runners are a type of stolon that runs above the ground and produces new clone plants at nodes at varying intervals: strawberries are an example.

• Charales

  • Branches arising from the nodes are made of smaller cells.
  • Male and female reproductive structures are found on the nodes; the sperm have flagella.

• Leaf Structure and Arrangment

  • Plants that have only one leaf per node have leaves that are said to be either alternate or spiral.
  • If there are three or more leaves connected at a node, the leaf arrangement is classified as whorled.

• Bone and Joint Disorders

  • The formation of hard nobs at the middle finger joints (known as Bouchard's nodes) and at the farther away finger joint (known as Heberden's node) are a common feature of Osteoarthritis in the hands.

• The Diversity of Life

  • A phylogenetic tree is composed of nodes and branches.
  • The internal nodes represent ancestors and are points in evolution when, based on scientific evidence, an ancestor is thought to have diverged to form two new species.