Muscle and Nerve tissue Flashcards
Features and functions of skeletal muscle
Cylindrical fibres
Under conscious control (not voluntary)
Heat, posture, protection
Structure of muscle fibres
Multinucleated
Long fibres
Striated
Size and structure of myofibrils
2um diametre
Extend length of muscle fibre
arrangement forms striations
Size of components of myofibrils
Actin - 8nm diametre, 1.5 um length
Myosin - 16nm diametre, 1.5 um length
The 3 connective tissues of skeletal muscle
Epimysium - Surrounds muscles
Perimysium - Surrounds fascicles
Endomysium - Surrounds individual muscle fibres
Bands and lines of muscle fibres
A line - Actin and Myosin I line - Actin only H line - Myosin only M line - centre of sarcomere Z line - between sarcomeres, actinins hold sarcomeres together
Structure of cardiac muscle
Striated Branched Single nucleus Joined by intercalated discs Purkinje fibres (fewer myofibrils, more gap junctions)
Components of intercalated discs
Desmosomes
Gap junctions
Location of smooth muscle
Walls of hollow internal structures
e.g intestines, blood vessel walls
Features of smooth muscle
Small, short and spindle shaped
Single central nucleus
Non striated
Structure of smooth muscle
Bundles of myosin and actin still present
Both thin and intermediate filaments attach to dense bodies (consisting largely of actinin)
Intermediate filaments do not contract - the cell ‘twists’ around these stable rods
Function of nervous system
Maintain homeostasis (along with the endocrine system)
Initiates voluntary movements
Responsible for perception, behaviour and memory
3 major functions of nervous system
Sensory
Integrative
Motor
Two cell types of nervous tissue
Nerve cells
Supporting neuroglia
Structures of neurons
Dendrites - receive other impulses Axon - output portion of neuron Trigger zone Myelin sheathe Axon terminal Cell body
Features of neurons
High metabolic rate (die quickly without O2)
Do not divide
Types of neurons
Multipolar
Bipolar
Unipolar
Anaxonic
Features of multipolar neurons
Many dendrites
Most common
Make up all motor neurons
Features of bipolar neurons
1 dendrite and 1 axon with cell body between
Rare and small (30 um)
Often in special sense organs
Features of unipolar neurons
Dendrites connected to axon
Cell body on side
Most sensory nerves
Very long
Feature of anaxonic neuron
Dendrites and axon indistinguishable
Rare and poorly understood
Found in brain and special sense organs
Features of neuroglia
Found in CNS and PNS 50% volume of CNS (acts as glue) 5-50x more numerous than neurons Small Do not propagate AP Divide
Function of neuroglia
Give structure to nervous tissue Repair nervous tissue Phagocytosis Nutrient supply Regulate interstitial fluid
List CNS neuroglia
Astrocytes
Oligodendrocytes
Microglia
Ependymal cells
Function and features of astrocytes
Star shaped - most abundant neuroglia Support and repair Communicate with neuronsvia gliotransmitters Regulate environment Maintain blood brain barrier
Function of oligodendrocytes
Form insulating multilayered myelin sheathe around axon in CNS
Can myelinate more than one axon
Function of microglia
Phagocytosis
Function of ependymal cells
Produce cerebrospinal fluid (CSF)
Line ventricles of brain and central canal of spianl cord
Predominantly cuboidal cells - have cilia for flow and microvili for sampling
CSF moves nutrients and waste
Peripheral system neuroglia
Schwann cells - can myelinate one axon but can support many
Satellite cells - surround cell bodies. Support and fluid exchange
