Module 2: Muscle and Nervous Tissue

convergent fascicle arrangment (skeletal muscle)

"fanned" like the pectoralis major

smooth muscle

- NOT striated - involuntary - located in the walls of many internal organs and passageways - Move food, urine, reproductive secretions through their respective systems - Control the diameter of blood vessels, respiratory tracts, iris - NOT connected by intercalated discs with gap junctions - capable of cell division and generating new cells

Bipolar neurons:

- These neurons have two processes, which extend from each end of the cell body- one is the axon and one the dendrite. - Bipolar cells are not very common and are found mainly in the olfactory epithelium (where smell stimuli are sensed), and as part of the retina.

glial cells can lead to three types of gliomas

- astrocytomas (tumor of astrocytes, less defined border and harder to resect) - oligodendrogliomas (tumor of oligodendrocytes) - mixed gliomas

functions of Myelin, a lipid-rich sheath that surrounds the axon

- facilitates the transmission of electrical signals along the axon - acts as insulation - gaps in the myelin are called nodes of Ranvier and assist with the speed of conduction along an axon

Ependymal cells (glial cell of the CNS):

- filter blood to make cerebrospinal fluid (CSF), the fluid that circulates through the CNS. - line each ventricle, the open spaces in the brain, and the cilia on their surface help to move CSF through the CNS.

Pseudounipolar neurons:

- have one process that includes both the axon and the dendrite - exclusively sensory neurons and have two unique characteristics.

characteristics of neurons:

- live for a lifetime - don't divide - high metabolic rates - most exist in the CNS for protection by bone

Astrocytes (glial cell of the CNS):

- most abundant glial cells in the CNS. - Named for their star shape, they have many processes extending from their main cell body which extend to interact with neurons and blood vessels. -Astrocytes have many functions, most of which serve to support neurons.

Schwann cells (glial cell of the PNS):

- myelinate axons in the PNS - Schwann cells are different than oligodendrocytes, in that a Schwann cell wraps its entire self around one part of only one axon segment

Oligodendrocytes (glial cell of the CNS):

- myelinate axons in the central nervous system. - One oligodendrocyte will provide the myelin for multiple axon segments, either for the same axon or for separate axons.

characteristics of glial cells:

- protection, insulation, and nourishment of neurons - more abundant than neurons - CAN divide - NOT excitable

Microglia (glial cell of the CNS):

- smallest and least-abundant in the CNS - "immune cells" of the brain - White blood cells, which are a primary line of defense in the body, cannot get through the blood brain barrier. Instead, microglia are constantly patrolling the CNS, extending and retracting their processes to inspect the brain and spinal cord tissue. - If there is damage to nervous tissue in the CNS, chemicals are sensed by the microglia and draw them to the injury site. - The microglia then phagocytize debris from the dead or dying cells and invading microorganisms.

cardiac muscle

- striated - involuntary - located in heart wall - circulates blood - connected by intercalated discs with gap junctions - NOT capable of cell division or generating new cells

skeletal muscle

- striated - voluntary - located in muscles acting on the limbs & trunk, muscles of facial expression, external sphincters regulating passage out of the body - Movement or stabilization of the skeleton, guard entrances and/or exits for the digestive, respiratory, and urinary systems - maintain posture and stabilize joints - Heat production - Protects internal organs - NOT connected by intercalated discs with gap junctions - NOT capable of cell division, but still capable of repair through satellite cells

Satellite cells (glial cell of the PNS):

- surround the cell bodies of neurons in the PNS, isolating them and protecting them from the surrounding tissue. - provide support, performing similar functions in the periphery as astrocytes do in the CNS.

pennate fascicle arrangment (skeletal muscle)

- unipennate (one angle) - bipennate (two angles) - multipennate (multiple angles)

astrocyte functions:

1. Regulate the environment around neurons and takes up and/or breaks down some neurotransmitters or ions in the fluid surrounding the neurons. 2. Contribute to the blood-brain barrier, a physiological barrier that keeps many substances that circulate in the rest of the body from getting into the central nervous system. 3. Act like the "connective tissue of the brain, filling spaces and holding things together 4. Form scar tissue of the brain by proliferating and surrounding damaged regions to separate it from the healthy neurons. This protects healthy neurons from chemical cascade that occurs as a result of the damage. 5. Regulate the inflammatory response to damage. 6. Involved in synapse formation and neuronal growth in developing nervous tissue. 7. Propagate calcium signals involved with memory.

Each skeletal muscle has three layers of connective tissue that enclose it, provide structure and support to the muscle as a whole, and compartmentalize the muscle fibers within the muscle. What are these?

Epimysium (outer): a sheath of dense, irregular connective tissue that surrounds each muscle Perimysium (middle): a sheath of connective tissue surrounding each individual fascicle Endomysium (inner): a sheath of connective tissue surrounding each individual muscle fiber

All muscle cells, or myocytes, share the following characteristics:

Excitability: can respond to a stimulus. Contractility: can contract and shorten the length of the fiber. The contraction of muscle tissue can be under voluntary, or conscious control, or involuntary, unconscious control. Extensibility: can stretch or contract beyond its resting length. Elasticity: can return to its original length when relaxed.

what does it mean that neurons are polar?

Information flows through a neuron from the dendrites, across the cell body, and down the axon --- information flows in this ONE direction.

myocyte shape of skeletal muscle

Large, long, cylindrical

Multipolar neurons:

Multipolar neurons are all of the neurons that are not unipolar or bipolar. They are by far the most common neurons in the body. They have one axon and two or more dendrites (usually many more).

myocyte shape of smooth muscle

Small, spindle-shaped (wide in the middle & tapered on each end, somewhat like a football)

The actin and myosin in a sarcomere overlap and move along each other as the muscle contracts, shortening the sarcomere. As sarcomeres shorten, the myofibril, muscle fiber, and the overall muscle all shorten.

The striated appearance of skeletal muscle fibers is due to the arrangement of the myofilaments in sequential order from one end of the muscle fiber to the other.

slow oxidative (SO) fibers:

aerobic, endurance, contract slowly, use oxygen and are fatigue resistant which makes them useful in maintaining posture, producing isometric contractions, stabilizing bones and joints, and making small movements that happen often but do not require large amounts of energy

fibers that carry sensory information toward the CNS are called __________ neurons, whereas fibers that carry motor information away from the CNS are called __________ neurons

afferent; efferent

When a motor neuron is stimulated, all muscle fibers in its motor unit will contract. This is called the __________.

all or none principle

neuronal convergence allows for _________ whereas divergence allows for ___________

amplification; widespread communication

Fast glycolytic (FG) fibers:

anaerobic, contract quickly and primarily use glucose which is located within the muscle, used to produce rapid, forceful contractions to make quick, powerful movements and therefore fatigue quickly

A 57-year-old male had a stroke in a branch of his middle cerebral artery. The brain tissue supplied by that branch began to break down due to lack of oxygen and nutrients. However, he was able to get to the ER within a short amount of time, so the amount of damage was limited. The two glial cells that would be active in this situation are the ...

astrocyte and microglia

Where the axon emerges from the cell body, there is a special region referred to as the ______________. This is a tapering of the cell body toward the axon fiber.

axon hillock

parallel fascicle arrangment (skeletal muscle)

biceps and rectus abdominis

what are the three main parts of a neuron?

cell body (soma): includes most of the cytoplasm, the organelles, and the nucleus. It is the processing or "thinking" part of the neuron. dendrite: receive input from other neurons and carry it to the cell body. axon: Neurons typically have one, propagates the nerve impulse which is communicated to one or more cells. The single axon can branch repeatedly to communicate with either a neuron, a muscle fiber, or a gland.

neural modalities

classifications of nervous tissue functions categorized by whether the nerve fibers are carrying sensory or motor information and by whether the nerve fibers are carrying somatic or visceral information.

Sharpey's fibers

collagen fibers penetrating deep into cortical bone (outer bone) and anchor tendon to bone

The somatic nervous system is responsible for our ___________ perception of the environment and for our voluntary responses to that perception by means of skeletal muscles.

conscious;

tendons are made up of

dense regular CT formed by merging all CT layers; avascular and very strong

Individual axons are surrounded by loose connective tissue called the _____________.

endoneurium

The predominant fiber type in a muscle is determined by the primary function of the muscle. The proportion of slow muscle fibers in muscle determines the suitability of that muscle for _________ activities.

endurance

When necessary, the maximal number of motor units in a muscle can be recruited simultaneously, producing the maximum force of contraction for that muscle, but this cannot last for very long because of the __________

energy requirements to sustain the contraction.

Unmyelinated axons in the PNS are still surrounded by Schwann cells, but they are not myelinated, meaning the Schwann cells do not wrap themselves in layers around unmyelinated cells. Instead, one Schwann cell can

engulf and surround a portion of several nearby axons.

Nerves are composed of more than just nervous tissue. They have connective tissues invested in their structure, as well as blood vessels supplying the tissues with nourishment. The outer surface of a nerve is a surrounding layer of fibrous connective tissue called the _______ .

epineurium

true or false: a single motor unit can control both slow oxidative and fast glycolytic fibers

false

true or false: exercise results in the formation of new muscle fibers

false

true or false: smooth muscle is striated

false

true or false: the CNS can regenerate but the PNS cannot

false

Each skeletal muscle is an organ that consists of skeletal muscle fibers, blood vessels, nerve fibers, and connective tissue. Inside each skeletal muscle, muscle fibers are organized into individual bundles, called ______________.

fascicles

After class you are spending time with friends and you decide to have a competition to see who can jump the highest. The type of skeletal muscle most active when you are jumping is ...

fast glycolytic

Resistance exercises require large amounts of fast glycolytic fibers to produce short, powerful movements that are not repeated over long periods of time. Muscles used for power movements have a higher ratio of ________ glycolytic fibers to _______ oxidative fibers.

fast; slow

response time for the NS is ... whereas response time for the endocrine system is ...

fast; slow

Skeletal muscle ____________, or muscle cells, are long, cylindrical fibers that span the entire length of a muscle.

fibers

Small motor unit = one motor neuron supplies a small number of fibers in a muscle. Small motor units permit very _____ motor control of the muscle.

fine Examples: muscles that move the eye (extraocular muscles) or muscles of the hand, where a single motor neuron can supply less than ten muscle fibers

Large motor unit = one motor neuron supplies a large number of muscle fibers in a muscle. Large motor units are concerned with simple, or _______(large), movements.

gross Examples: thigh muscles or back muscles, where a single motor neuron will supply thousands of muscle fibers

Cardiac muscle and smooth muscle can respond to electrical stimuli from the nervous system as well as

hormones and local stimuli.

smooth muscle cells are thousands of times shorter than skeletal muscle fibers. Unlike other muscle tissue, smooth muscle tissue can also divide to produce more cells, a process called ____________

hyperplasia

hypertrophy

increase in muscle size (opposite is atrophy)

Skeletal muscle completely depends on _______________ from the nervous system to contract.

innervation

cardiomyocytes contain _______________ with gap junctions that form communication channels between adjacent cells, allowing cardiac muscle cells to contract in a wave-like pattern so the heart can work as a coordinated pump.

intercalated discs

General visceral motor:

involuntary movement of our cardiac and smooth muscle and secretion from glands

the effect of the NS is ... whereas the effect of the endocrine system is ...

localized; widespread

To prevent complete muscle fatigue, motor units are generally not all simultaneously active, but instead some motor units rest while others are active, which allows for ...

longer and more efficient muscle contractions.

Because most smooth muscles must function for long periods without rest, their power output is relatively ______, but contractions can continue without using large amounts of energy.

low

General visceral sensory:

monitoring and sensing unconscious information primarily coming from our organs and glands

Every skeletal muscle fiber must be innervated by a ______ neuron in order to contract.

motor

Each muscle fiber is innervated by only one motor neuron, but one motor neuron can innervate several skeletal muscle fibers. The group of muscle fibers in a muscle innervated by a single motor neuron is called a _____________

motor unit

Skeletal muscle tissue forms the muscles that

move our bones and joints.

Cardiac muscle tissue is found in the heart. Cardiomyocytes, or cardiac muscle fibers (muscle cells), are

much smaller and shorter than skeletal muscle fibers, and they are extensively branched.

organization of skeletal muscle: skeletal muscle --- fascicles ---

muscle fiber --- myofibrils --- myofilaments --- sarcomere

Each muscle fiber contains many ___________, and each " " runs the entire length of the muscle fiber. " " contain many ______________, which are actin and myosin proteins. The actin and myosin are organized into repetitive groupings, and each unique grouping is called a __________.

myofibrils; myofilaments; sarcomere

In both the CNS and PNS two main classes of cells make up nervous tissue: ____________.

neurons and neuroglia (support neurons)

the target of the NS is ... whereas the targets of the endocrine system are ...

neurons, glands, muscles; any cell with a receptor for that hormone

Neurons, or nerve cells, transmit information through the body via electrochemical signals. There are many neurons in the nervous system—a number in the trillions. The synapse is the gap between two neurons, or between a neuron and its target, a muscle or a gland, across which the impulse is transmitted by chemical compounds known as ...

neurotransmitters

the NS communicates via ... whereas the endocrine system communicates via ...

neurotransmitters; hormones

A group of neuronal cell bodies in the CNS is called a _________ whereas a group of neuronal cell bodies in the PNS is called a __________

nucleus; ganglion

General somatic sensory:

our sense of touch, pressure, pain, temperature, and proprioception

what are the four fascicle arrangements of skeletal muscle fiber?

parallel, convergent, pennate, and circular

Within the nerve, axons are further bundled into fascicles, which are each surrounded by their own layer of fibrous connective tissue called ______________.

perineurium

Of the flexor carpi radialis (forearm). quadriceps (thigh), and lateral rectus (eye): The muscle with the most muscle fibers per neuron is the ... The muscle with the smallest motor unit (least fibers per neuron) is the ...

quadriceps; lateral rectus

The __________ is the functional unit of the muscle fiber.

sarcomere

In the PNS, the entire surface of each nerve is completely surrounded by glial cells. The type of glial cell that surrounds the cell bodies are the ___________ and the type of glial cell that surrounds the axons are the ____________.

satellite cells; schwann cells

a decrease in glial cells in the frontal cortex has been associated with ...

schizophrenia and depression

the response duration of the NS is ... acting whereas the effect of the endocrine system is ... acting

short; long-lasting

The neuromuscular junction is the ________________

site where a motor neuron meets the muscle fiber.

what are the three types of muscle tissue?

skeletal, cardiac, smooth

As you are sitting in your chair, your postural muscles are active to keep you sitting upright. The type of skeletal muscle fibers most abundant in these postural muscles is ...

slow oxidative

Which type of skeletal muscle fibers do you think has the greatest number of capillaries (blood supply)?

slow oxidative (relies on oxygen for its fuel which comes from blood vessels)

what are the three types of skeletal muscle fibers?

slow oxidative fibers, fast oxidative fibers, fast glycolytic fibers

myocyte shape of cardiac muscle

small, short, branched

circular fascicle arrangment (skeletal muscle)

sphincters and orbicularis oris

Both skeletal and cardiac muscle tissue is

striated

The three connective tissue layers merge, and the collagen fibers intertwine and become aligned together to form the _________, which is composed of dense regular connective tissue.

tendon

muscles attach to bone via ...

tendons

For oligodendrocytes in the CNS, the rest of the cell is separate from the process that forms a myelin sheath around a given axon segment. For Schwann cells in the PNS, ...

the entire cell wraps itself around the axon.

sarcopenia

the loss of muscle mass and function that comes with aging and is irreversible (less pronounced in endurance athletes than power athletes)

A bundle of axons (fibers) in the CNS is called a _________ whereas a bundle of axons in the PNS is called a __________

tract (most common), also fascicle, lemniscus, commissure; nerve

true or false: oligodenrocytes can myelinate several parts of several axons whereas schwann cells only myelinate one part of one axon

true

Visceral information involves ___________ sensory and motor activity. Visceral motor activity is part of the __________ nervous system.

unconscious; autonomic

General somatic motor:

voluntary movement by skeletal muscles

the PNS can regenerate because of

wallerian degeneration --- distal area breaks down and axon regenerates through chord that guides axon back to its target, Schwann cells promote growth