Control and cordination Flashcards
2 Nervous system
central nervous system - brain and spinal cord
peripheral Nervous system- cranial nerves (Connected to the brain) and spinal nerves (connected to the spinal cord)
motor neuron structure
Has a cell body with dendrites on one side
and axon
the other side will terminal branches
Sensory neuron structure
A cell body in the middle of the axon and symmetrical ends except 1 is dendrites and other are the terminal branches
Relay neuron structure
A cell body with dendrites around
no axon
central nervous system
The relay neuron
The cell body and dendrites of the motor neuron
The terminal branches (Synaptic knobs) of the sensory neuron
Action potential
rapid change in the electrical charge distribution across a cell surface membrane
5 phases of membrane potential mV against time
Rest till stimulus received (-70mV)
Depolarization (30mV)
Repolarization (-70mV)
Refractory period (Below -70mV)
Rest (-70mV)
Rest
No membrane protentional where 3Na+ is transported out and 2K+ is transported into the membrane by Na+/K+ pump
This creates a membrane potential of -70mV in the axon
where positive charge is higher outside (More Na+)
Na+ voltage gated channels open
(Received stimulus)
Depolarization (Action potential)
The voltage gated channel open when stimulus is received and Na+ rushes from high to low conc. inside the axon making in more positive (+30mV)
when mV 30 is reached the voltage gated channels close and K+ channels open
Repolarization (Action potential)
K+ voltage gated channels open and K+ rushes in from high to low conc.
creating a -ve charge inside the axon
Refractory period
During this period the axon is unresponsive to stimulus
Rest
the entire process repeats across the axon switching charges and transferring the impulse
Threshold potential
If weak stimulus is detected very few Na+ vgc open and only a little Na+ rush in to action potential is not generated as it is not being able to hold up to reach threshold potential
this is useful as our body will be able to conserve ATP and not waste it on unnecessary impulse that does it no good
usually between -50mv and -60mv
action potential across the axon
The conc. of Na+ is high in that section and lower along the axon
Na+ shall diffuse further allowing Na+ vgc to open across the axon and Na+ rushes in increasing the membrane potential
This whole process is called as local current
causing the next section of the axon to depolarize.
the action potential travel along the axon in one direction
Function of myelin sheath
myelin sheath (Schwann cells) provides an electrical insulation
[saltatory conduction]
causes action potential to ‘jump’ along the nodes of Ranvier (section on the axon without myelinated sheath)
speed up the action potential
cholinergic synapse situation
PS: name of the synapse depends on the neurotransmitter
The neuron before the synapse gap is presynaptic neuron
The neuron after the synapse gap is Postsynaptic neuron
Ca+ voltage gated channels on the presynaptic neuron
vesicles containing neurotransmitters (ACh)
synaptic cleft the distance between the 2 neurons
Post synaptic neuron maintains a resting membrane potential
it also has ACh (complimentary) receptors that open the Na+ ligand gc
Cholinergic synapse (Acetyl choline)
impulse reaches the end of the presynaptic neuron.
voltage gated ca+ channels open.
Ca+ rushes in
vesicles move towards the cell surface membrane
exocytosis of ACh
ACh diffuses across the synaptic cleft
ACh binds to complementary receptors on the post synaptic neuron
Ligand gated Na+ channels open and Na+ rushes in
Post synaptic membrane depolarizes and new action potential is generated
What happens to acetyl choline
if acetyl choline is always attached to receptors then membrane is permanently depolarized as the channel remains open and cannot return to resting potential / repolarization
- ACh detaches from the receptors and is need back
- Acetylcholinesterase breaks down ACh into acetate and choline
- choline is reabsorbed into the presynaptic neuron and regenerated into ACH
Role of synapses
To ensure impulse only travels in 1 direction
because presynaptic always has vesicles and poste synaptic neuron always have receptors
Allows interconnection of nerve pathways
individual neurons can connect with multiple other neurons
Allow us to produce a more efficient response
skeletal muscle ‘cell’
no exactly a cell because it has many nucleus
very very long
referred to as syncytium instead
cytoplasm and cell membranes in referred as sarcoplasm and sarcolemma respectively
sarcoplasmic reticulum instead of endoplasmic
structure of myofibrils
Myofibril forms patterns of dark and light areas and are the contractive units units
[myosin]
Thick protein filaments
creating the darker region in myofibrils
M-line holds the myosin filaments in line
[actin]
thin protein filaments
creating the lighter region in myofibrils
Z-line holds the actin filaments in line
Distance between 2 Z-lines is known are sarcomere
Actin filament structure
A thin filament made out of actin proteins, troponin and tropomyosin
Tropomyosin function
prevents actin filament and myosin head from attaching
Troponin
binding site of Ca+ (Ca+ receptors)
