Terry Gleave Flashcards
what happens if the sodium/potassium pump gets poisoned?
it stops working
Na+ voltage gated ion channels are either:
open, closed or closed&inactive
Unipolar sensory neurons have…
one long axon which connects receptors to the spinal cord or brain
multipolar, inter and motor neurons have
many dendrites and one axon
Bipolar neurons have
one dendrite and one axon
What is the equilibrium potential for K+?
-90mV
Alan L. Hodgkin and Andrew F. Huxley won a Nobel Prize in Physiology/Medicine in 1963. Wha did they record in 1939?
They first recorded the resting potential from living neuron - Squid giant axon (0.5mm in diameter)
The threshold is when
the membrane potential becomes more positive than at rest and depolarisation reaches a trigger point
At threshold, what is generated?
an action potential
As the axon hillock depolarizes, which voltage gated ion channels open rapidly?
Na+
Conduction velocity is the speed of…?
Action potential
1-20m/s is the speed of what?
an impulse that travels along neurons
What does the speed of conduction depend on?
The diameter of a fiber (bigger AP= faster), temperature and whether or not it is myelinated
What is saltatory conduction?
Where action potentials jump between nodes of Ranvier under myelination.
A fibres are
large myelinated axons that conduct action potential at the speed 15-120 m/s
B fibres are
medium diameter myelinated axons that conduct the action potential at the speed 3-15 m/s
C fibres are
unmyelinated axons that conduct the action potential at the speed <3 m/s
Electrical synapses are
extremely rare, have direct contact between cells (gap junctions) and are located in CNS and PNS.
Chemical synapses are
involved in the release of neurotransmitters, most abundant and the cells are not directly coupled.
Name the three types of muscles:
Skeletal, cardiac, smooth
Phasic smooth muscles are controlled by
the action potentials of the Uterine and the GI tract
Tonic smooth muscles are controlled by
Electrical, chemical and mechanical signals
How is the contraction of skeletal muscles controlled?
by motor units
What activates the excitation of skeletal muscles?
the nerve endings of motor neurons
Why is the postsynaptic membrane of the muscle cell highly folded?
it increases the surface area for increasing the number of acetylcholine receptors.
How many times longer is the duration of the cardiac action potential than the skeletal muscle action potential
100 times
What are cardiac muscles interconnected by? what does this allow?
Gap junctions. These allow the passage of action potentials from cell to cell. This ensures that the entire heart participates in contraction.
Skeletal muscle contracts only when
it receives a nerve impulse
SAN generates APs at a faster rate than other areas of the heart at ……. beats per minute
70-80
How many beats per min do the AV node and the AV bundle produce?
40-60
the purkinjie fibres and the bundle branches generate action potentials at what rae (beats per min)
20-40
What happens when the SAN malfunctions?
The next highest frequency action potentials are used, usually the AVN
what is meant by systole?
to contract
what is meant by atrial systole?
Contraction of atrial myocardium
What is meant by diastole?
to dilate
What is meant by atrial diastole?
Relaxation of atrial myocardium
What is the P wave?
the SAN generates the pacemaker potential which causes depolarization which propagates across the atria
What is the QRS complex on an ECG?
- Starts as AP pass from AVN to the ventricles
- Completed when the ventricles are depolarised and start to contract
- Atrial repolarisation is masked by QRS and atria relaxed
What is another word for changes in heart rate?
Chronotropic changes
Changes in the force of contraction are called
inotropic changes
What are the factors which affect the stroke volume?
Preload, afterload, contractility
Baroreceptors sense
pressure
An increase in pressure causes a(n) ……….. in sympathetic activity
decrease
A decrease in pressure causes a(n) …………. in sympathetic activity
increase
an increase in volume causes a ………. in Anti Diuretic Hormone secretion which leads to…………
decrease, reduction of water retention
An increase in volume will also result in an……………… in Atrial Natriuretic hormone secretion and an increase in……………
increase, urine production
