Cells and Tissues: Muscle and Nervous Tissue Flashcards
Muscle tissue description
tissue that is made of contractile cells (muscle fibres) that contract to make body parts move and generates heat
What is muscle tissue comprised of?
It is made up of elongated cells (muscle cells or muscle fibres or myocytes)
What is the function of muscle tissue?
To use energy from the hydrolysis of ATP to generate contractile forces, producing body movements, maintains posture and generates heat
What are the three types of muscle tissue?
Skeletal, cardiac and smooth muscle (these comprise more than 50% of body tissue mass)
Where are skeletal muscle attached?
To bones via tendons
What is skeletal muscle comprised of?
Long, cylindrical fibres in the tissue that make it look striated. It is also multinucleated (many peripheral nuclei pushed to the side)
The function of skeletal muscle?
Motion, posture, heat production and protection
Is skeletal muscle voluntary?
It is considered voluntary because contraction and relaxation are under conscious control. However, some things like posture are not voluntary
What is the stapedius and where is it located?
The smallest skeletal muscle in the body (1.25mm) and is located in the ear
What is hyperacusis?
Excessively sensitive hearing -
What is Bell’s Palsey?
A condition where paralysis of the facial nerve causes muscular weakness in one side of the face and hyperacusis
What is the sartorius and where is it located?
The longest skeletal muscle (60cm) which is located in the anterior region of the thigh?
What is the function of the sartorius?
Flexes, abducts, and laterally rotates thigh/hip; flexes knee
What are myofibrils?
Protein structures (diameter is 2 micrometres) that run the entire length of the sarcoplasm (cytoplasm), made up of filaments
What is sarcoplasm?
The cytoplasm in skeletal muscle
What is sarcolemma?
is the plasma membrane of a striated muscle fibre cell
What are myofibrils made of?
Thin and thick filaments
What type of filament is Actin?
The thin filament in myofibrils (8 nm diam; 1-2 μm long)
What type of filament is myosin?
The thick filament in myofibrils (16 nm diam; 1-2 μm long)
What is a sarcomere?
A structural unit of a myofibril in striated muscle
What is epimysium?
dense irregular connective tissue surrounding a muscle
What is perimysium?
the sheath of connective tissue surrounding a bundle of muscle fibres
What is endomysium?
a layer of areolar connective tissue that ensheaths each individual muscle fibre/ muscle cell. Capillaries and nerves are on this layer
What is the A band?
The dark middle area of the sarcomere, containing all thick filaments
What is the I band?
Area of sarcomere containing thin filaments only
What is the H zone?
Area of sarcomere containing thick filaments only
What is the M line?
Middle of the sarcomere, holds thick filaments in place and binds to titin
What is the Z disc?
Provides anchorage for thin filaments (I band) and titin while also linking filaments of adjacent sarcomeres
What is titin?
The ‘molecular spring’ that links the M line to the Z disc
What does cardiac muscle consist of?
Fibres that join end-to-end through intercalated discs. It is striated and branched with a single central nucleus.
What are intercalated discs and what do they contain?
Attachment sites between the transverse lines between cardiac muscle cells, containing desmosomes and gap junctions
The function of desmosome in the intercalated disc
To bind intermediate filaments and provide adhesion in vigorous contractions
The function of gap junctions in the intercalated disc
For communication, cell co-ordination and rapid conduction throughout the heart
Where is cardiac muscle tissue found?
The heart wall
What is the function of cardiac muscle tissue?
To pump blood to all parts of the body
Where is smooth muscle tissue located?
Located in the walls of hollow internal structures
e.g. intestines (peristalsis); blood vessel walls (constriction); Iris of the eye, reproductive; digestive; respiratory; urinary; skin erector pili
Is cardiac muscle tissue voluntary?
No, it is involuntary
Is smooth muscle tissue voluntary?
No, it is involuntary
What is smooth muscle comprised of?
It contains bundles of thin (actin) and thick (myosin) filaments
It is short, small, spindle-shaped, about 30-200 μm long; 3-8 μm thickest in the middle Non-striated (smooth) and has a single central nucleus
What are dense bodies?
These are similar to Z discs which contain protein Actinin. Thin filaments (actin) and intermediate filaments attach themselves to dense bodies
How do smooth muscle cells twist during contraction?
The intermediate filaments are non-contractile so when the cell contracts the filaments force the cell to contract around these “stable rods” causing it to twist
What is the function of smooth muscle tissue?
Motion - the constriction of blood vessels and airways, propulsion of foods through the gastrointestinal tract, contraction of urinary bladder and gallbladder
Nervous tissue description
tissue that contains conducting nerve cells and supportive neuroglia that carries information from one part of the body to another through nerve impulses
The two components of the nervous system
The central nervous system (CNS) and the Peripheral nervous system (PNS)
What is in the CNS?
Brain, spinal cord and optic nerve
What is in the PNS?
All other nervous tissue outside of the CNS
What is the role of the PNS?
Afferent division: to send information to the CNS
Efferent division: to send information from the CNS to the organs (muscles and glands)
Nervous system function
Maintain homeostasis(along with the endocrine system)
Initiates voluntary movements
Responsible for perception, behaviour and memory
What is the nervous tissue sensory function?
Detection of internal and external stimuli and transfer to CNS
What is the nervous tissue integrative function?
analysis and storing of information
What is the nervous tissue motor function?
stimulation of effectors (e.g. muscle and glands) through PNS
What does nervous tissue consist of?
Neurons and neuroglia that have both conscious and unconscious control
What are neurons comprised of?
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.
NEURONS DO NOT DIVIDE and have a high metabolic rate
What is a dendrite?
The receiving/input part of the neuron
What is an axon?
carries the nerve impulse away from the neuron. It is the output portion of the neuron
Features of multipolar neurons
Have 2 or more dendrites and a single axon.
Most common neurons in CNS
All motor neurons (control skeletal muscle) are in this class
Some of the longest (spinal cord to toe muscles)
Features of bipolar neurons
Two distinct processes
–1 dendritic process (can branch at the tip but not at cell body)
–And 1 axon
Has the cell body between axon and dendrite
Rare and small (30μm)
Special sense organs (sight, smell, hearing) relay information from receptor to neurons
Features of Unipolar neurons
The dendrites and axon are continuous
Cell body off to one side
Whole thing from where dendrites converge called an axon
Most sensory nerves are unipolar
Very long (1m) like motor nerves CNS-toe tip.
Features of an anaxonic neuron
RARE
Anatomy cannot distinguish dendrites from axons
Found in the brain and special sense organs
What are the functions of the neuroglia
The physical structure of nervous tissue Repair framework of nervous tissue Undertake phagocytosis Nutrient supply to Neurons Regulate interstitial fluid in neural tissue.
Where are neuroglia found?
in both the CNS and PNS
How big are neuroglia?
They are smaller than neurons but more numerous
Features of neuroglia
They can communicate but do not propagate action potentials and can divide in the mature nervous system
What is the Myelin sheath?
Covers the axon of some neurons and helps speed neural impulses
What are Astrocytes?
CNS neuroglia that is responsible for the support and repair of neurons. They maintain the environment around neurons through maintaining the blood-brain barrier, regulate ions, influence the permeability of vessels
What are Gliotransmitters?
Method of communication between astrocytes and neurons
What are Ependymal cells?
CNS neuroglia that produces Cerebrospinal fluid, line ventricles in the brain, contain cilia for movement and microvilli for sampling and monitoring
The function of Cerebrospinal fluid?
A mechanical buffer that moves nutrients and waste
What are Oligodendrocytes?
Type of glial cell in the CNS that wrap axons in a myelin sheath. These can myelinate more than one neuron cell’s axon at a time.
What are Microglia?
Phagocytic glia that provides protection
What are the two cells in the PNS?
Schwann cells and Satellite cells
What are Schwann cells?
PNS glia that can form the myelin sheath for one axon, or provide support for multiple non-myelinated axons
What are satellite cells?
PNS cells that surround the neurons to provide support and help with fluid exchange
