Lecture 4: Muscle & Nerve Tissue Flashcards
1
Q
What are the two types of Nerve Cells?
A
Neurons & Neuroglia
2
Q
What is a Neural Cell?
A
A Cell of the Nervous System
3
Q
Where does the word Neuron come from?
A
based on the ancient Greek neuron ‘sinew, cord, nerve’
4
Q
Where does the word Neuroglia come from?
A
from neuro- ‘of nerves’ + Greek glia ‘glue’.
5
Q
What are the subdivisions of the Nervous System?
A
Central nervous system (CNS): brain and spinal cord (and optic nerve)
Peripheral nervous system (PNS): all nervous tissue outside CNS
6
Q
Where are Neurons found?
A
In both the Central Nervous System & the Peripheral Nervous System
7
Q
Where are Neuroglia found?
A
Different types can be found in the Central Nervous System, or the Peripheral Nervous System. A singular type can not be in both.
8
Q
What is the Soma?
A
The cell body.
Contains the nucleus and the organelles.
9
Q
What is the function of Neurons?
A
To process and transmit information
10
Q
What is the function of Neuroglia?
A
To support the Neurons in a variety of ways.
11
Q
What is the area where the Axon leaves the Soma called?
A
The Axon Hillock
12
Q
What are the divisions of the Peripheral Nervous System?
A
Sensory/afferent division: Information to the CNS.
Motor/efferent division: Information from CNS to the organs (muscles and glands).
13
Q
What does the Nervous System help us do?
A
Maintain homeostasis (along with the endocrine system)
Initiates voluntary movements
Responsible for perception, behaviour and memory
14
Q
What are the three major functions of the Nervous System?
A
Sensory: Detection of internal and external stimuli and transfer to CNS
Integrative: analysis and storing of information
Motor: stimulation of effectors (e.g. muscle and glands) through PNS i.e.
motor here means “effector”
15
Q
What is the composition of a Neuron?
A
A cell body into which short, branched dendrites convey nerve impulses (action potentials) and from which a longer, single axon conducts nerve impulses to another neuron or tissue.
16
Q
What is a Dendrite?
A
The receiving/input part of the neuron.
17
Q
What is an Axon?
A
Carries the nerve impulse away from the neuron. It is the output portion of the neuron.
18
Q
Do Neurons divide?
A
No.
19
Q
What can’t Neurons survive without?
A
High metabolic rate.
(die rapidly without O2)
19
Q
Do Neuroglia divide?
A
Yes.
20
Q
What are Multipolar Neurons?
A
Neurons with 2 or more dendrites and a single axon.
21
Q
What are the most common Neuron type?
A
Multipolar Neurons
22
Q
What Neuron type are all motor neurons?
(Control Skeletal Muscle)
A
Multipolar Neurons
23
Q
What is the longest Neuron type?
A
Multipolar Neurons
Spinal cord to toe muscles
24
What are Bipolar Neurons?
Neurons with 1 Dendritic process (can branch at tip, but not at cell body) and 1 axon.
Has cell body between
axon and dendrite
Rare and small (30μm)
25
Where are Bipolar Neurons?
Special sense organs
(sight, smell, hearing)
Relay information from receptor
to neurons
26
What are Unipolar Neurons?
The dendrites and axon are continuous
Cell body off to one side
Whole thing from where dendrites converge called axon
Most sensory nerves are unipolar
Very long (1m) like motor nerves CNS-toe tip.
27
What are Anaxonic Neurons?
Rare and functions are poorly understood
Anatomy cannot distinguish dendrites from axons
Found in brain and special sense organs
28
What type of Nerve cells make up the majority of the volume in the CNS?
Neuroglia
29
Are Neurons or Neuroglia smaller
Neuroglia
Smaller than neurons but more numerous (5-50x)
30
Can Neuroglia propagate action potentials?
Do not propagate action potentials, but can communicate.
31
Can Neuroglia divide?
Can divide within the mature nervous system
32
What characterizes voluntary muscle tissue?
Voluntary muscle tissue is controlled by the conscious will of the individual, allowing for intentional movements.
33
How many skeletal muscles are there in the human body?
There are approximately 650 named skeletal muscles in the body, usually attached to bones via tendons.
34
What is the structure of skeletal muscle fibers?
Skeletal muscle fibers are cylindrical, multinucleate cells with peripheral nuclei pushed to the side, and they appear striated under a microscope due to the organized arrangement of myofibrils.
35
What is the smallest skeletal muscle in the human body?
The smallest skeletal muscle is the stapedius, measuring 1.25 mm, which stabilizes the stapes bone in the ear and prevents hyperacusis.
36
What is the longest skeletal muscle in the human body?
The longest skeletal muscle is the sartorius, which can be up to 60 cm long and is involved in twisting the leg inwards.
37
What is the role of the sarcolemma in muscle fibers?
The sarcolemma is the cell membrane of muscle fibers, which are essential for muscle contraction.
38
What is the role of the sarcoplasm in muscle fibers?
The sarcoplasm is the cytoplasm that contains myofibrils, which are essential for muscle contraction.
39
What is hyperacusis and how is it related to the stapedius muscle?
Hyperacusis is a condition where there is an increased sensitivity to sound, which can occur if the stapedius muscle, controlled by the facial nerve, is damaged.
40
Describe the type of muscle that is attached to bones by tendons.
Skeletal muscle is the type of muscle that is attached to bones by tendons.
41
Explain the structure of skeletal muscle cells.
Skeletal muscle cells are long, striated, and multinucleate, with many peripheral nuclei pushed to the side.
42
How is skeletal muscle controlled?
Skeletal muscle is under voluntary control.
43
List the primary functions of skeletal muscle.
The primary functions of skeletal muscle include motion, posture, heat production, and protection.
44
Define myofibrils and their role in skeletal muscle.
Myofibrils are structures that fill the cytoplasm of muscle fibers and extend their entire length, composed of thin and thick filaments.
45
What are the two types of filaments found in myofibrils?
The two types of filaments in myofibrils are thin filaments, mostly actin, and thick filaments, which are myosin.
46
Explain the arrangement of myofilaments within skeletal muscle fibers.
Myofilaments are arranged in compartments called sarcomeres, which are separated by Z discs
47
Define a sarcomere in the context of skeletal muscle.
A sarcomere is the basic functional unit of a myofibril in skeletal muscle.
48
Describe the connective tissue layers associated with skeletal muscle.
The connective tissue layers include:
epimysium (surrounds the entire muscle)
perimysium (around fascicles)
endomysium (around individual muscle fibers).
49
What is the role of the endomysium in skeletal muscle?
The endomysium surrounds muscle fibers and provides a layer for capillaries and nerves, facilitating blood flow and control.
50
Explain the significance of Z discs in skeletal muscle.
Z discs separate sarcomeres and are crucial for the structural organization of myofibrils.
51
How do the striations in skeletal muscle fibers occur?
Striations in skeletal muscle fibers are due to the highly organized arrangement of myofibrils within the cells.
52
What is the diameter of thin and thick filaments in myofibrils?
Thin filaments have a diameter of 8 nm, while thick filaments have a diameter of 16 nm.
53
Describe the sarcoplasm in skeletal muscle.
Sarcoplasm is the cytoplasm of a muscle fiber, containing myofibrils and other organelles.
54
What is the sarcolemma?
The sarcolemma is the actual plasma membrane of a muscle cell.
55
Describe the function of the epimysium in muscle anatomy.
The epimysium surrounds the anatomical muscle, providing a protective coat that reduces rubbing and merging between muscles.
56
Explain the role of fascicles in muscle structure.
Fascicles are rod-like structures that allow muscles to adopt different postures and shapes.
57
Define perimysium and its relationship to fascicles.
Perimysium is a connective tissue that coats the fascicles, similar to the epimysium, providing support and structure.
58
How does endomysium contribute to muscle function?
Endomysium surrounds individual muscle cells, providing a layer for capillaries and nerves, facilitating nutrient and signal exchange.
59
What is the sarcolemma and its significance in muscle cells?
The sarcolemma is the actual cell plasma membrane of muscle cells, crucial for maintaining the cell's integrity and facilitating communication.
60
Describe the composition of sarcoplasm.
Sarcoplasm is the cytoplasm of muscle cells, containing various organelles and substances necessary for muscle function.
61
Explain the significance of the A band in myofibrils.
The A band is the dark, middle part of the myofibril that contains all the thick filaments, playing a key role in muscle contraction.
62
What characterizes the I band in muscle fibers?
The I band consists of thin filaments and contains no thick filaments, contributing to the striated appearance of muscle fibers.
63
Define the H zone and its relevance in muscle structure
The H zone is the region within the A band that contains only thick filaments and no thin filaments, important for muscle contraction dynamics.
64
Describe the M line and its function in the sarcomere.
The M line is located in the middle of the sarcomere and holds the thick filaments together, providing structural support.
65
What is the Z disc and its role in muscle fibers?
The Z disc passes through the center of the I band and is made up of actinins, linking filaments of adjacent sarcomeres.
66
Describe the structure of cardiac muscle.
Striated, branched, has a single central nucleus, and features intercalated discs.
67
Explain the function of intercalated discs in cardiac muscle.
Intercalated discs contain desmosomes for adhesion during contraction and gap junctions for coordinated and rapid communication.
68
How do Purkinje fibers differ from regular cardiac muscle cells?
Purkinje fibers are specialized muscle cells with fewer myofibrils and more 'connexins'; gap junctions that facilitate electrical conduction.
69
Define the control mechanism of cardiac muscle.
Cardiac muscle is under involuntary control.
70
Describe the location and function of smooth muscle.
Smooth muscle is located in the walls of hollow internal structures such as intestines and blood vessels, and it functions in processes like peristalsis and constriction.
71
Explain the characteristics of smooth muscle cells.
Smooth muscle cells are short, small, spindle-shaped, and range from about 30 to 200 μm in length.
72
Identify the types of structures where smooth muscle can be found.
Smooth muscle can be found in the intestines, blood vessel walls, iris of the eye, and in reproductive, digestive, respiratory, urinary systems, and skin (erector pili).
73
How does the structure of cardiac muscle contribute to its function?
The striated and branched structure, along with intercalated discs, allows for strong contractions and coordinated heartbeats.
74
Describe the thickness of smooth muscle fibers.
Smooth muscle fibers are 3-8 μm thickest in the middle.
75
Explain the striation characteristics of smooth muscle.
Smooth muscle fibers are non-striated, meaning they do not have the banding pattern seen in striated muscles.
76
Define the nucleus structure in smooth muscle cells.
Smooth muscle cells have a single central nucleus.
77
How do thin filaments attach in smooth muscle fibers?
Thin filaments, such as actin, attach to dense bodies, which are functionally similar to Z discs.
78
What is a major protein found in dense bodies of smooth muscle?
A major protein found in dense bodies is Actinin.
79
Describe the role of intermediate filaments in smooth muscle contraction.
Intermediate filaments are non-contractile elements that connect to dense bodies and help transmit tension during contraction.
80
Explain the contraction mechanism of smooth muscle cells.
During contraction, tension is transmitted to the intermediate filaments, causing the cell to twist as it contracts around these stable 'rods'.
81
Identify the type of muscle that is involuntary and non-striated.
The type of muscle that is involuntary and non-striated is smooth muscle.
82
Where is smooth muscle typically located in the body?
Smooth muscle is located in the walls of hollow internal structures, such as blood vessels, intestines, and skin.
83
What type of control is associated with smooth muscle?
Smooth muscle is controlled involuntarily.
84
Describe the main function of neurons in nervous tissue.
Neurons are responsible for transmitting electrical signals throughout the nervous system, facilitating communication between different parts of the body.
85
Explain the role of dendrites in a neuron.
Dendrites receive signals from other neurons and transmit these signals to the cell body.
86
What is the significance of the axon in a neuron?
The axon transmits electrical impulses away from the cell body to other neurons or muscles.
87
How do neurons respond to a lack of oxygen?
Neurons die rapidly without oxygen due to their high metabolic rate and inability to divide.
88
Explain the function of neuroglia in the nervous system.
Neuroglia are supportive cells that assist neurons, maintain homeostasis, and provide protection, but do not propagate action potentials.
To provide homeostatic, structural and metabolic support of neurons, to meylinate (forming a myelin sheath) their axons to ensure rapid signal transmission and to be the main defensive and immunocompetent cells.
89
Describe the role of Schwann cells in the nervous system.
Schwann cells form the myelin sheath around peripheral nerves, aiding in the insulation and speed of electrical signal transmission.
Note: One Schwann cell per axon for myelination but more axons/cell if just supporting
90
What is the function of satellite cells in the nervous system?
Satellite cells support and protect neuron cell bodies in the peripheral nervous system.
Equivalent to astrocytes in CNS
91
How do oligodendrocytes contribute to the central nervous system?
Oligodendrocytes form the myelin sheath around axons in the central nervous system, which insulates and speeds up signal transmission.
92
Explain the role of microglia in the nervous system.
Microglia act as the immune cells of the central nervous system, capable of engulfing and digesting dead cells and debris.
93
What is the function of ependymal cells in the central nervous system?
Ependymal cells line the ventricles of the brain and the central canal of the spinal cord, helping to circulate and sample cerebrospinal fluid.
94
Describe the characteristics of astrocytes in the central nervous system.
Astrocytes are star-shaped, the largest and most numerous type of neuroglia, providing support, repair, and maintaining the blood-brain barrier.
95
How do astrocytes communicate with neurons?
Astrocytes communicate with neurons through gliotransmitters, such as glutamate, influencing neuronal activity.
96
What is the significance of the blood-brain barrier maintained by astrocytes?
The blood-brain barrier protects the brain from harmful substances in the bloodstream while allowing essential nutrients to pass through.
97
Define the term 'syncytium network' in relation to astrocytes.
A syncytium network refers to the interconnected nature of astrocytes, allowing them to work together in supporting neuronal function.
98
Explain the role of microfilaments in astrocytes.
Microfilaments provide structural support to astrocytes, enabling them to maintain their shape and assist in the repair of nervous tissue.
99
What is the primary function of the myelin sheath formed by oligodendrocyte
The myelin sheath insulates axons, increasing the speed of electrical signal transmission along the nerve fibers.
100
Describe the function of oligodendrocytes in the central nervous system.
Oligodendrocytes can myelinate more than one neuron cell's axon and accelerate the action potential.
101
Define the primary function of ependymal cell
Ependymal cells produce cerebrospinal fluid (CSF) and line the CSF-filled ventricles in the brain and the central canal of the spinal cord.
102
How do ependymal cells contribute to the movement of substances in the brain?
Ependymal cells have cilia that help in the flow of cerebrospinal fluid and microvilli that assist in sampling nutrients and waste.
103
Identify the locations where ependymal cells are found.
Ependymal cells are located in the ventricles of the brain and in other areas where cerebrospinal fluid is present.
104
What is the mechanical function of cerebrospinal fluid (CSF)?
CSF acts as a mechanical buffer, moving nutrients and waste within the central nervous system.
105
Describe the role of Schwann cells in the peripheral nervous system.
Schwann cells form an insulating myelin sheath around axons and can also support and surround several non-myelinated axons.
106
How does the myelination process differ between Schwann cells and oligodendrocytes?
One Schwann cell myelinates one axon, while oligodendrocytes can myelinate multiple axons.
107
Explain the function of satellite cells in the peripheral nervous system.
Satellite cells surround neuron cell bodies, providing support and facilitating fluid exchange, similar to astrocytes in the central nervous system.
