Lecture 4 muscle + nerves Flashcards
Muscle tissue structure/function
Elongated muscle cells (myocytes) hydrolyse Adenosine Triphosphate (ATP) to generate force. Movements, posture, generates heat
3 types of muscle tissue
Skeletal, cardiac, smooth
Skeletal muscle structure
650 of them; striated, usually voluntary and attached to bones by tendons, cylindrical fibres, multi-nuclei
Skeletal muscle function
generates heat, produces body movement, and maintains posture from contractions
sarcomere
basic unit of myofibrils, defined by z discs on each side
myofibril structure
consists of sarcomere units made of thick (myosin) and thin (actin) myofilaments, surrounded in endomysium
fascicles
bundles of myofibrils covered in perimysium
epimysium
surrounds muscle
sarcoplasm and sarcolemma
muscle cell cytoplasm and muscle cell membrane
muscle fibre cell structure
Covered in endomysium, then double layered sarcolemma membrane. Sarcoplasm contains myofilaments actin and myosin.
IZ
Z discs (made from actinins which bind actin between sarcomeres) pass thru I band (only thin)
MAH
M line passes thru A (H bands (only thick) + overlap areas) and holds thick myosin together
Titin
Links Z disc to M line like spring providing tension in I band
Cardiac muscle
Striated, branched, ends of fibres join end - end thru intercalated discs, single nuclei, involuntary
Intercalated discs
Desmosomes for adhesion, gap junctions for communication/coordination/rapid conduction
Purkinje fibres
Specialised heart cells that conduct electrical activity; less myofibrils, more connexins
Smooth muscle structure
non striated but still have myosin/actin, single central nuclei, involuntary, dense bodies major protein is actinin, also connected by non-contractile intermediate filaments
PNS afferent and efferent functions
Sensory info to CNS, motor info to organs
Nervous system functions
Sensory, Motor, Integrative
Sensory
Detects internal + external stimuli for homeostasis
Motor
stimulation of effectors (muscles and glands) and initiates voluntary movement
Integrative
Analyse and store info for perception, behaviour, memory
2 nervous tissue cell types
Neuron (large), Neuroglia (supportive, small)
Neuron cell structure
Nucleus in cell body, dendrites receive nerve impulses (action potentials), axon sends out nerve impulses
4 neuron types
Multi-polar, bipolar, unipolar, anaxonic
Multi polar neurons
two or more dendrites + one axon, most common type.
Bipolar neurons
one dendrite + one axon, rare and small
Unipolar neurons
continuous dentrite and axon with cell body off to side
Anaxonic neurons
Very rare, dunno function, dendrites and axons indistinguishable, found in brain and special sense organs
All Motor neurons are what type
Multipolar
Special senses (sight, smell, hearing) what neuron type
Bipolar
CNS neuroglia
Astrocytes, oligodendrocytes, microglia, ependymal cells
PNS neuroglia
Satellite cells, Schwann cells
Astrocytes function
Support and repair, maintain environment around neutron via regulating ions, maintains BBB by influencing blood vessel permeability
Astrocytes features
Star shaped, largest and most numerous of neuroglia; forms Syncytium network.
Oligodendrocytes function
Forms insulating myelin sheaths (protein lipid layer) around CNS axons to accelerate action potential
Oligodendrocyte vs Schwann cells
One Oligo cell can myelinate more than one axon per cell, one Schwann cell can only myelinate one axon per cell(but can support/tube more than one axon)
Microglia
Resident macrophages (phagocytic) for protection of CNS
Ependymal cells function
Produce CerebroSpinal Fluid (CSF), lines central canal of spinal chord and other CSF filled ventricles (in brain), CSF mechanical buffer and moves nutrients/waste
Ependymal cell structure
Predominantly simple cuboidal, have BOTH microvilli and cilia
Schwann cell function
Forms insulating myelin sheath around PNS axons or just support/surround non-myelinated axons
Satellite cells function
Surround neuron cell bodies to provide support and fluid exchange
(equiv to astrocytes of cns)
Neuroglia features
Don’t communicate with action potentials (use chemicals), smaller than neurons but more numerous, in CNS and PNS, can divide within mature nervous system
Neuroglia functions
Physical structure and repair framework of nervous tissue, phagocytosis, nutrient supply, regulate interstitial fluid in neural tissue
Smallest/longest skeletal muscle
Smallest: Stapedius -1.25mm- to prevent hyperacusis (loud sound deafening)
Largest: Sartorius -up to 60cm- twist leg to look at bottom of feet
Smooth muscle locations
Blood vessels; iris of eye; digestive, urinary, reproductive systems, intestines, skin erector pili
what do astrocytes communicate with
gliotransmitters (e.g. glutamate)
Ependymal mechanical buffer function
Absorbs shock by acting as cushioning
