Introdction To Basic Tissue Types Muscle And Nervous Flashcards
Muscle tissue
Responsible for generating movement of animal body and its parts, including musculoskeletal system, visceral organs, heart
Characteristics of muscle cells
Muscle cells also called myocytes, large amounts of contractile proteins actin and myosin
Myofibril
Structural and functional subunits of muscle cells, composed of actin and myosin myofilaments organized in specific and repetitive manner
Classification of muscle
classified according to appearance of contractile cells
2 principle types- smooth and striated
Can differentiate based on size and shape of cell, number, shape, and location of nuclei within cell
All muscle cells regardless of type are surrounded by external lamina that is analogous to basement membrane of epithelial tissue
Striated muscle cells
Exhibit cross striations at light microscopic level by myofilaments are in parallel arrays in register with each other
Subdivided into
Skeletal and cardiac based on function and location
Smooth muscle
Myofilaments are not organized in parallel arrays and it therefore does not have striated appearance
Comparison of three muscle types
Shape Number, shape, and location nuclei
Skeletal Cylindrical Multiple, flat, peripheral
Cardiac Branched. Single, block like, central
Smooth. Fusiform. Single, spindle-or corkscrew-shaped, central
Organization skeletal muscle
Striated muscle fibers held together by connective tissue, muscle fiber is multinuclearted syncytium formed by fusion of small individual myoblasts during development; in cross section skeletal muscle fibers have polygonal shape, long axes are in the direction in which the contract
Associated connective tissue
Endomysium, perimysium, epimysim
Endomysium
Thin delicate layer of reticular fibers that immediately surrounds individual muscle fibers
Perimysium
Thicker layer that surrounds group of fibers forming bundle (fascicle)
Epimysium
Forms dense sheath surrounding collection of fascicles which forms a muscle
Organization of Cardiac muscle
Cardiac muscle also called myocardium. Appears striated bc myofilaments organized in same manner as skeletal muscle, fibers are not multinucleated syncytium like in skeletal muscle but rather multiple cells arrayed end to end; cells attach to each other via intercalated discs; can form branched fiber via joining of two or more cells
Smooth muscle
Smooth muscle generally in sheets or bundles of elongated fusiform cells with tapered ends; cytoplasm will stain envelope with eosin
Sensory component of nervous system
Collects info from external environment and from within body
Motor component of nervous tissue
Controls activity of muscles, organs, and even individual cells
Anatomical division of nervous system
CNS- brain and spinal chord
PNS- nerves that conduct impulses to and from brain and spinal chord
Cell types of nervous tissue
Neurons and neuroglia ( supporting cells)
Neuron- functional unit of nervous system, relieve stimuli from other cells and conduct electrical impulses accordingly
Neuroglia- non conducting cells, located near neurons, functions: physical support, electrical insulation, facilitation of repair, regulation internal fluid environment in CNS, clearance neurotransmitters metabolic exchange between vascular system and neurons
Axon
Transmits impulses away from cell body to synapse which makes contact with another neuron or an effector cell (muscle cell or glandular epithelial cell); in PNS all neurons are enveloped in Schwann cells providing structural and metabolic support. Non-myelinated axons enveloped by cytoplasm of Schwann cells. Myelinated axons are wrapped in myelin sheath consisting of variable number of concentric layer of Schwann cell plasma membrane. In CNS axon myelinated by oligodendrocytes
When viewed via light microscopy axons appear wavy bc need extra length to withstand stretching forces
Dendrites
Transmit impulses toward the cell body; receptors that recieve impulses from other neurons or from external environment, Nissl bodies, free ribosomes, and occasionally Golgi apparatus will extend into dendrites (NEVER axon)
Cell body of neuron
Contains nucleus and organelles, nucleus is large and euchromatin with prominent nucleus (bc cell makes a lot of protein), abundant free ribosomes and rough ER, mitochondria (numerous), large Golgi apparatus, lysosomes, transport vesicles, cytoskeletal elements
Nissl bodies
When viewing neuron cell body by light microscopy the abundant ribosomal constant appears as small intensely basophillic bodies called Nissl bodies, each Nissl body corresponds to a stack of rER
Axon hillock
Junction of axon with cell body, lacks large organelles, good way to distinguish between axon and dendrites
Ganglia
Groups of nerve cells outside of CNS. Ganglion consists of cell bodies of either sensory or motor neurons NEVER both
Nerves
Groups of axonal processes (aka nerve fibers) travel together in anatomical structure known as nerve; Nerves can be sensory motor or mixed
Peripheral nerves
Held together by connective tissue in manner similar to skeletal muscle
Endoneurium- composed of loose connective tissue surrounds each individual fiber
Perineurium- surrounds fascicles (bundles of fibers)
Epineurium- dense irregular connective tissue that surrounds entire nerve and fills in spaces between nerve fascicles
Questions for identifying tissues
- Are the cells on a surface
- Are the cells in contact with their neighbors or are the separated from each other by an intervening substance
- Do the cells belong to a group with specialized functional (and structural) properties such as nerve of muscle
Autonomic ganglia
Clusters of neurons located along autonomic pathways, contain autonomic motor neurons
3 major categlories
Sympathetic trunk ganglia, ganglia in head, abdomen, and pelvic cavity, and
Terminal Ganglia
Sympathetic trunk ganglia
Located ventrolaterally to vertebral bodies along sympathetic trunk, connected to spinal nerves by communicating branches, generally segmental other than
Cranial Cervical Ganglion- multiple fused cervical ganglia at caudal skull base
Middle cervical ganglion- multiple fused cervical ganglia at thoracic inlet
Cervicothoracic ganglion- caudal cervical ganglia fused with first 2-3 thoracic ganglia
Ganglia located in head abdomen and pelvic cavity
Ciliary ganglia of head (parasympathetic), celiacemosenteric and caudal mesenteric ganglia of abdomen (sympathetic), pelvic ganglia (sympathetic and parasympathetic)
Terminal ganglia
Microscopic clusters of neurons located within target tissue, associated with vagus and pelvic nerves, involved in parasympathetic function
Vertebral nerve
Continues cranially from cervicothoracic ganglion to supply sympathetic autonomic innervation of skin and muscles of the neck, travels with vertebral artery into transverse foramina of cervical vertebrea
Communicating branches from vertebral nerve join each cervical spinal nerve to provide sympathetic innervation to muscles and skin supplied by that spinal nerve, NO SYMPATHETIC GANGLIA IN VERTEBRAL NERVE bc axons making up vertebral nerve have cell bodies (from sympathetic neurons) in cervicothoracic ganglion
Sensory pathways
Carrying information from tissues to the CNS, somatic and visceral afferent pathways
Motor pathways
Carrying commands from the CNS to muscles and glands, somatic and visceral efferent pathways ** Visceral efferent subdivides into sympathetic and parasympathetic
Visceral efferent
Motor pathway (ANS), smooth muscle, cardiac muscle, glands, split into parasympathetic (vegetative functions) and sympathetic (fight of flight)
Somatic afferent
Sensory, skin, bones, joints, skeletal muscles
Visceral afferent
Internal organs, sensory
Somatic efferent
Motor skeletal muscles
Visceral efferent
Motor pathway, ANS, sympathetic (fight for flight), parasympathetic (vegetative functions)
Visceral and somatic information with in CNS
Will be integrated ie stepping on a tack produces sympathetic (Visceral efferent) response of increased heart rate and somatic efferent response of pulling foot away
Somatic efferent pathways
Consist of one neuron from CNS to target muscle, these are called lower motor neurons or somatic efferent neurons, most skeletal muscle under voluntary control so this is referred to as voluntary muscle (though not all under voluntary control)
Location of cell bodies of LMN that control skeletal muscles of body
Somatic efferent neurons ie LMN are in Ventral horn of spinal cord, axons exit spinal cord via ventral root then spinal nerve, exit dorsal branch for epaxial muscle and ventral branch for hypaxial muscles
Synaptic terminal of LMNs forms specialized synapse on muscle fibers called neuromuscular junction where neurotransmitters are released from axon terminal leading to muscle fiber contraction
Location of cell bodies that control skeletal muscles of head
Brainstem axons exit brainstem and travel in cranial nerves
Phrenic nerve motor pathway
Phrenic nerve is somatic so LMN cell bodies are in ventral horn of spinal chord, segments C5C6C7 (keep you from going to heaven), axons exit each segment via ventral root and enter spinal nerve then ventral branches, leave ventral branches to merge and form phrenic nerve (bilaterally), axons of phrenic nerve terminate in neuromuscular junctions of muscle fibers of diaphragm