(01) Muscle and Nervous Tissue Flashcards
functions of muscle tissue
uses energy from the hydrolysis of ATP to generate force
contract –> movements / maintain posture / generate heat
general structure of muscle tissue
consists of elongated cells - muscle cells / fibres or myocytes
what is a myocyte
the smallest subunit of all muscle tissue (cardiac and skeletal)
name the three types of muscle tissue
skeletal
cardiac
smooth
describe the appearance of skeletal muscle
striated (under microscope)
cylindrically shaped fibres
long cells
multinucleated (nuclei pushed to sides of cylindrical muscle fibres)
describe the functions and locations of skeletal muscle
voluntary / consciously controlled contractions
attached to bones by tendons
name the smallest skeletal muscle in the human body
Stapedius- 1.25mm
where is the stapedius located and what does it do?
in the ear
stabilises the stapes (smallest bone in the ear), keeps sound in comfortable range (prevents hyperacusis - loudness perception disorder)
name the longest skeletal muscle in the human body
sartorius - up to 60cm
where is the sartorius located
checking for gum - hip flexor, abductor, lateral rotator
meaning of prefix myo-
denotes muscle
meaning of prefix sarco-
denotes flesh
name the three main parts of a skeletal muscle fibre
sarcolemma = outside plasma membrane of muscle fibre
Sarcoplasm = inside part = cytoplasm
myofibrils = filaments
why are skeletal muscle fibres striated?
due to highly organised myofibrils within cells
name the two types of filaments in myofibrils
Myofilaments:
- THIN = actin
- THICK = myosin
8nm diam vs 16
what are sarcomeres
the basic functional unit of a myofibril
myofilaments are arranged in compartments called sarcomeres
name the bands producing striations
A band
I band
H zone
M line
Z disc
describe the A band
dark middle part of the sarcomere
contains ALL thick filaments
describe the I band
thin filaments, no thick filaments
the remaining part of the sarcomere not including A band
describe the H zone
thick filaments ONLY, no thin
within the A band
(think literally an H shape)
describe the M line
the middle of the sarcomere
Holds thick filaments together
describe the Z disc and what it’s made up of
between sarcomeres
links filaments to adjacent sarcomeres
passes through the centre of the I band
made up of ACTININS
describe contracted muscle in terms of bands / zones
relaxed muscle has both A / I band, and H zone
during contraction, H zone and I band shrink as thin and thick filaments overlap more
maximally contracted muscle has only A band
describe cardiac muscle (location, structure, appearance, function)
heart, involuntary
striated, branched
single central nucleus
intercalated discs - fibres joined end to end
what do intercalated discs contain?
desmosomes
gap junctions
what do desmosomes in intercalated discs do
heart must deal with FORCE:
they bind intermediate filaments
provide adhesion in contraction
what do gap junctions in intercalated discs do
heart must be COORDINATED:
important for communication
rapid conduction
describe the appearance / structure of smooth muscle
not striated, but still has bundles of thin (actin) and thick (myosin) filaments
short, small, spindle-shaped
single central nucleus
diamond layout of “dense bodies”
function and location of smooth muscle
involuntary
in the walls of hollow internal structures
eg. blood vessels, intestines, skin
what are dense bodies made up of and what do they do
functionally similar to Z discs
major protein is also actinin
connected to thin filaments and intermediate filaments, so during contraction tension is transmitted to intermediate filaments (don’t contract) and the cell twists
roles of the nervous system
maintain homeostasis (with endocrine system)
initiates voluntary movements
perception, behaviour, memory
three major functions of the nervous system
- sensory (detect external stimuli –> CNS)
- Integrative (analysis / store info)
- Motor (stimulation of effectors through PNS)
two types of cells in nervous tissue
neurons (longest cells in the body!)
neuroglia
name the main parts of a neutron
cell body (soma)
dendrites
axon
describe dendrites
short, branched, attached to cell body
the receiving / input part
describe the axon
longer, single axon attached to cell body
output - carries the nerve impulse away from the neuron
for our purposes, neurons…
do not divide
have high metabolic rate (die rapidly without O2)
name four types of neurons
multipolar
bipolar
unipolar
anaxonic
name the most common type of neurons in the CNS
multipolar neurons
structural features of multipolar neurons
hace 2+ dendrites
a single axon
some of the longest (spinal cord to toe)
what are motor neurons
they control skeletal muscles
all multipolar neurons
structural features of bipolar neurons
two distinct processes: 1 dendritic process (can branch at tip but not at cell body) and 1 axon
cell body is between axon and dendrite
small and rare
function of bipolar neurons
special sense organs (sight / smell / hearing)
relay info from receptor to neurons
structure of unipolar neurons
CONTINUOUS dendrites and axon
cell body off to one side
very long
function of unipolar neurons
most sensory nerves
structure of anaxonic neurons
cannot distinguish dendrites from axons
(looks kinda like a starfish)
function of anaxonic neurons
rare, function poorly understood
found in brain and special sense organs
where are neuroglia found
both the CNS and PNS
makes up about 50% volume of CNS
neuroglia vs neurons relative size
neuroglia are smaller than neurons but more numerous
neuroglia vs neurons action potentials
neuroglia do NOT propagate action potentials, but they can communicate (chemically)
neuroglia vs neurons cell division
unlike neurons, neuroglia continually divide throughout an individual’s lifetime, even within a mature nervous system
functions of neuroglia
“-glia” = glue
physical structure of nervous tissue
repair framework of NT
undertake phagocytosis
nutrient supply to neurons
regulate interstitial fluid in neural tissue
name four types of neuroglia in the CNS
Astrocytes
oligodendrocytes
microglia
ependymal cells
describe the structure of astrocytes
star-shaped
largest and most numerous of the neuroglia - wrapped around capillaries
has microfilaments
key functions of astrocytes
maintain (chemical) environment around neuron - blood-brain barrier via endothelium
support and repair
communicate with neurons via gliotransmitters (eg. glutamate)
structure of oligodendrocytes
they resemble astrocytes (star shaped) but are smaller and contain fewer processes
function of oligodendrocytes
forms insulating multilayered myelin sheath around CNS axons to accelerate action potential
(increases speed of nerve impulse conduction)
can mylenate more than one neuron cell’s axon
what is the myelin sheath around CNS axons made of
a protein lipid layer
describe the appearance of microglia
smaller cells with slender processes that give off numerous spine-like projections
function of microglia
phagocytic – remove cellular debris
phagocytise microbes and damaged nervous tissue
structure of ependymal cells
single layer of cuboidal (sometimes columnar) cells with both cilia and microvilli
location of ependymal cells
lines ventricles of the brain and central canal of the spinal cord (and other locations where CSF is found)
role of ependymal cells
produce and circulate cerebrospinal fluid (CSF)
CSF mechanical buffer - moves nutrients and waste
Name the two types of neuroglia in the PNS
Schwann cells
Satellite cells
what is the function of Schwann cells
the PNS equivalent of CNS oligodendrocytes -
forms insulating myelin sheath around axons (1 per axon)
OR supports several non-myelinated axons (multiple per axon)
location and function of satellite cells
PNS equivalent of CNS astrocytes -
surrounds neuron cell bodies + regulate environment
support + fluid exchange
myelinating Schwann structure
forms sheath around peripheral axons
outer surface of Schwann cell = neurilemma
single Schwann cell myelinated one INTERNODE of one axon
non-myelinating Schwann cell structure and function
neurilemma (outer surface) wraps around multiple axons
forms internode of many unmyelinated axons
so that axons are arranged around the Schwann cell nucleus
stabilises positions of axons + isolates them from chemicals in interstitial fluid
