Anatomy and Physiology Exam 2 Flashcards
Threshold Stimulus
the minimal stimulus that results in a muscle twitch.
Twitch Contraction
the brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron.
Contraction Period
lasts about 10-100 msec and is the period during which force (measured in grams) is increasing.
Latent Period
Lasts about 2-10 msec (milliseconds) and is the time between stimulation of muscle cells and force generation.
Relaxation Period
Lasts about 10-100 msec, is the period when the force is decreasing.
Neuron
a nerve cell, consisting of a cell body, dendrites, and an axon.
Dendrites
are the receiving or input portions of a neuron.
Axon Hillock
an axon is a long, thin, cylindrical projection that often joins to the cell body at a cone-shaped elevation called the axon hillock.
Grey Matter
the grey matter of the nervous system contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, neuroglia.
White Matter
is composed primarily of myelinated axons. the whitish color of myelin gives white matter its name.
Multipolar Neuron
usually have several dendrites and one axon. most neurons in the brain and spinal cord are of this type, as well as all motor neurons.
Bipolar Neuron
have one main dendrite and one axon. they are found in the retina of the eye, the inner ear, and the olfactory area of the brain.
Unipolar Neuron (Pseudounipolar)
have dendrites and one axon that are fused together to form a continuous process that emerges from the cell body. These neurons are so named because they begin in the embryo as bipolar neurons. During development, the dendrites and axon fuse together and become a single process. The dendrites of most pseudounipolar neurons function as sensory receptors that detect a sensory stimulus such as touch, pressure, pain, or thermal stimuli. The trigger zone for nerve impulses in a unipolar neuron is at the junction of the dendrites and axon. The impulses then propagate toward the synaptic end bulbs. The cell bodies of most pseudounipolar neurons are located in the ganglia of spinal and cranial nerves.
Epidural Space
the spinal cord is also protected by a cushion of fat and connective tissue located in the epidural space, a space between the dura mater and the wall of the vertebral canal.
Dura Matter
the most superficial of the three spinal meninges is a thick strong layer composed of dense irregular connective tissue. The dura mater forms a sac from the level of the foramen magnum in the occipital bone, where it is continuous with the meningeal dura mater of the brain, to the second sacral vertebra. The dura mater is also continuous with the epineurium, the outer covering of spinal and cranial nerves.