Anatomy and Physiology Exam 2 Flashcards

1
Q

Threshold Stimulus

A

the minimal stimulus that results in a muscle twitch.

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2
Q

Twitch Contraction

A

the brief contraction of all muscle fibers in a motor unit in response to a single action potential in its motor neuron.

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3
Q

Contraction Period

A

lasts about 10-100 msec and is the period during which force (measured in grams) is increasing.

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4
Q

Latent Period

A

Lasts about 2-10 msec (milliseconds) and is the time between stimulation of muscle cells and force generation.

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5
Q

Relaxation Period

A

Lasts about 10-100 msec, is the period when the force is decreasing.

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6
Q

Neuron

A

a nerve cell, consisting of a cell body, dendrites, and an axon.

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7
Q

Dendrites

A

are the receiving or input portions of a neuron.

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8
Q

Axon Hillock

A

an axon is a long, thin, cylindrical projection that often joins to the cell body at a cone-shaped elevation called the axon hillock.

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9
Q

Grey Matter

A

the grey matter of the nervous system contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, neuroglia.

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10
Q

White Matter

A

is composed primarily of myelinated axons. the whitish color of myelin gives white matter its name.

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11
Q

Multipolar Neuron

A

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.

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12
Q

Bipolar Neuron

A

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.

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13
Q

Unipolar Neuron (Pseudounipolar)

A

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.

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14
Q

Epidural Space

A

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.

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15
Q

Dura Matter

A

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.

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16
Q

Arachnoid Matter

A

this layer, the middle of the meningeal membranes, is a thin, avascular covering comprised of cells and thin, loosely arranged collagen and elastic fibers. It is called the arachnoid mater because of its spider’s-web arrangement of delicate collagen fibers and some elastic fibers that extend between the arachnoid mater and pia mater. It is deep to the dura mater and is continuous through the foramen magnum with the arachnoid mater of the brain. Between the dura mater and the arachnoid mater is a thin subdural space, which contains interstitial fluid.

17
Q

Pia Matter

A

this innermost meninx is a thin transparent connective tissue layer that adheres to the surface of the spinal cord and brain. It consists of thin squamous to cuboidal cells within interlacing bundles of collagen fibers and some fine elastic fibers. Within the pia mater are many blood vessels that supply oxygen and nutrients to the spinal cord. Triangular-shaped membranous extensions of the pia mater suspend the spinal cord in the middle of its dural sheath. These extensions, called denticulate ligaments, are thickenings of the pia mater. They project laterally and fuse with the arachnoid mater and inner surface of the dura mater between the anterior and posterior nerve roots of spinal nerves on either side. Extending along the entire length of the spinal cord, the denticulate ligaments protect the spinal cord against sudden displacement that could result in shock. Between the arachnoid mater and pia mater is a space, the subarachnoid space, which also contains shock-absorbing cerebrospinal fluid.

18
Q

Sensory Receptor

A

If the stimulus to the sensory receptor is strong enough, an action potential is generated in the sensory neuron.

19
Q

Sensory Neuron

A

The sensory neuron propagates the action potential and synapses with neurons in the spinal cord or brain stem.

20
Q

Integrating Center

A

The integrating center is located within the gray matter of the central nervous system (CNS) and transfers information from the sensory neuron to the motor neuron. The integrating center of a monosynaptic reflex arc is a single synapse between a sensory and motor neuron. In a polysynaptic reflex arc, the integrating center consists of multiple synapses involving one or more interneurons (association neurons) between a sensory and a motor neuron.

21
Q

Motor Neuron

A

The motor neuron carries the action potential initiated by the integrating center to the effector.

22
Q

Effector

A

An effector can be skeletal muscle (somatic reflex), cardiac muscle, smooth muscle, or glands (autonomic reflexes). A reflex is the response of the effector to stimulation by the motor neuron of the reflex arc.

23
Q

Reflex Arcs

A

that involve sensory receptors, sensory nerve neurons, motor neurons, and effectors all on the same side of the body are ipsilateral.

24
Q

Contralateral Reflex Arcs

A

involve sensory receptors and neurons on one side of the body and motor neurons and effectors on the opposite side.

25
Q
A