Lecture 4 : The Tissues of the Human Body: Muscle & Nervous Tissue Flashcards
Muscle tissue (I)
Elongated cells, muscle fibres (myocytes), energy from the hydrolosis of ATP to generate force
Muscle tissue (II)
Muscle contraction produces body movement, maintains posture, and generates heat.
Skeletal muscle (I)
650
attatched to bones via tendons
striated
Skeletal muscle (II)
Voluntary; but not always
cylindracal
smallest: stapedius
largest: sartorius
The striations (I)
of skeletal muscle fibres, arragement of myofibrils within the cells
The striations (II)
Myofibrils fill the cytoplasm (sacroplasm) of the muscle fibre and extend its entire length of the cell
Myofibrils are composed of 2 types of myofilaments
thin: actin
thick: myosin
Myofilaments
Do not extend the length of the muscle fibre, arranged into sacromeres
Sacromere
Sacromere is the basic functional unit of myofibril
Z discs (z lines) separate sacromeres
Connective tissue (I)
Epimysium: surrounds anatomical muscle
Perimysium: around fascicles
Endomysium: around muscle fibers (“cell”) –
(layer for capillaries/nerves)
Connective tissue (II)
Sarcolemma: actual cell plasma membrane
Sacroplasm: cell cytoplasm
Thick & thin myofilaments overlap to produce
Striations
Bands (I)
A band: dark mid, all thick
I Band: thin
H Zone: thick
M line: mid of sacromere
Bands (II)
Z disc: passes through centre of I band, actinin, link adjacent sacromeres
Titin: links Z disc to M line: resting tension in I band, molecular spring
Cardiac muscles
Striated, branched
Single central nucleus
Fibres join end-to-end through intercalated discs
intercalated discs
Desmosome - adhesion in contraction
gap junction - communication
involuntary, actin and myosin
“Purkinje fibres”
are specialised muscle cells that conduct electrical activity around the heart. They have less myofibrils and more specialised “connexins” (gap junctions).
Smooth muscle (I)
Involuntary
non-striated
single central nucleus
short, small, spindle shaped
Smooth muscle (II)
walls of hollow internal structures - intestine; BV walls
Smooth muscle (III)
thin filaments attatch to dense bodies (actinin) similar to Z discs
Smooth muscle (IV)
twists around rod
intermediate filamens also connect to dense bodies
Nervous tissue
CNS: brain, sc and optic nerve
PNS: all nervous tissue outside CNS
PNS
sensory/afferent division: info to CNS
motor/efferent: info from CNS to organs (muscles and glands)
Nervous function
Maintains homeostasis (endocrine)
involuntary movements
perception, behaviour and memory
Activities grouped under three major functions:
i. Sensory: Detection of internal and external stimuli and transfer to CNS
ii. Integrative: analysis and storing of information
Activities grouped under three major functions:
Motor: stimulation of effectors (e.g. muscle and glands) through PNS i.e.
motor here means “effector” 19
Neurons (I)
Dendrites: receiving/input part of neuron
axon: carries the nerve impulse away from neuron. (output)
do not divide, high metabolic rate (without O2 = death)
Neurons (II)
Cell body, branched dendrites convery nerve impulses (action potentials), longer single axon conducts nerve impulses to another neuron or tissue.
Multipolar Neurons
2 or more dendrites, 1 axon
most common neuron in CNS
Multipolar Neurons
all motor neurons (control skeletal muscle) are in this class
som of the longest (sc to toe muscles)
Bipolar neurons
1 dendrite, 1 axon
cell body between axon and dendrite
small and rare
Bipolar neuron
Special sense organs (sight, smell, hearing) relay info from receptor to neurons
Unipolar neuron
dendrites and axons are continuous
cell body to one side
most sensory nerves are unipolar
Unipolar neuron (II)
Very long (1m) like motor nerves CNS-toe tip
whole thing from where dendrites coverage called axon
Anaxonic neuron
rare and function poorly understood
cannot distinguish between dendrites from axons
Anaxonic neuron
Brain and special sense organs
Neurogila (I)
CNS & PNS
~50% the volume of CNS (glue)
Neurogila (II)
smaller than neruons but more numerous
communicate
can divide within the mature nervous system
Neurogila functions (I)
physical structure & repair framework of nervous tissue
phagocytosis
Neurogila functions (II)
Nutrients –> neurons
regulate intersitiual fluids in nerual tissue
CNS Neurogila: Astrocytes
star shaped; largest
SYNCYTIUM NETWORK
CNS Neurogila: Astrocytes
communicate with neurons via gliotransmitters
maintain environment around neuron
CNS Neurogila: Astrocytes
maintain blood brain barrier via endothelium
Oligodendrocytes
insulating multilayers myelin sheath arond CNS axons
myelinate more than 1 neuron cells axon. accelerate action potential
microgila
phagocytic (resident macrophages) - protection
Ependymal cells
Produce cerebrospinal fluid (CSF).
Line the Cerebrospinal Fluid (CSF)-filled
ventricles in the brain and the central
canal of the spinal cord.
Ependymal cells
These single layer of predominantly
cuboidal cells have cilia (flow) and
microvilli (sampling).
Located in ventricles and in other locations
where CSF found.
Ependymal cells
CSF mechanical buffer; moves nutrients and waste
PNS Neurogila: Schwann cells
form insulating myelin sheath around axons or can just support and surround several non-myelinated axons.
(Note: One Schwann cell per axon for myelination but more axons/cell if just support).
PNS Neurogila: Satellite cells
ii. Satellite cells: surround neuron cell bodies. Support and fluid exchange
(equiv. to astrocytes in CNS) .
