Nerves and Muscle Flashcards
(40 cards)
Define the anatomical components of the central and peripheral nervous systems.
the CNS is the brain and the spinal cord.
the PNS is the nerves that branch out from the brain and spinal cord.
Explain the principal functions of neurons and glial cells and know their primary morphological features.
neurons are collectors and integrators of information. they can strengthen or weaken synapses and change connection, which alters their branching. spaces not covered by synapses are covered by glial cells and have a large surface area to volume ratio.
glial cells maintain homeostasis, form myelin, and provide support and protection for neurons.
Explain the difference between cells and structures in the peripheral and the central nervous systems.
PNS - peripheral nerves that are covered by ganglia and surrounded my specialized connective tissue cells.
CNS - brain and spinal cord, encased by meninges which contain cerebrospinal fluid
Describe the effect of voltage on ion movement.
If there is any change in membrane potential, the voltage gated ion channels will respond. For example, if the Vm nears 0, voltage gated Ca2+ channels will open and Ca2+ will diffuse into the cell.
Describe the development of diffusion potential by ion movements - Nernst potential.
This is the voltage at which the electrostatic force on an ion is equal and opposite to the chemical force from the concentration gradient. Nernst potential is when the cell membrane is solely permeable to K+, resting Vm is equal to Ek.
Describe the relationship between diffusion potential and membrane potential (Vm).
If there is a concentration difference for an ion across a membrane and the membrane is permeable to that ion, a potential difference (the diffusion potential) is created.
Describe the relationship between Vm and ion concentrations.
Differences in the concentrations of ions on opposite sides of a cellular membrane lead to a voltage called the membrane potential
Describe the role of Na+/K+-ATPase.
Replenish K+ lost from the cell and remove Na+ accumulated within the cell. Na+/K+-ATPase channel pumps Na+ into the extracellular space and K+ into the intracellular space via ion channels.
Describe the characteristics of neuronal action potential.
A threshold potential has to be reached. The rising phase of the action potential is due to depolarization, the charge then goes above the 0 potential. The potential is then repolarized and hyperpolarized.
Describe the ionic basis of action potential generation.
- rapid depolarization is due to the opening of Na+ channels once the threshold voltage is reached
- The membrane is repolarized by K+ leaving the cell
Describe the refractory period and Na+ channel inactivation.
A given period of time before a stimuli will elicit another response. It can be overcome to some degree with a stronger stimulus. This is up to a certain point known as the absolute refractory period. This is due to Na+ ion channel inactivation.
Describe propagation and conduction of action potential.
Nerve conduction velocity is affected by axon diameter, myelination and temperature.
Describe synaptic structure and the mechanisms of chemical neurotransmission.
- the presynaptic membrane which is formed by the terminal button of an axon
- the postsynaptic membrane which is composed of a segment of dendrite or cell body
- the space between these two structures which is called the synaptic cleft.
neurotransmitters diffuse across this gap.
Describe ionotropic receptors and fast synaptic transmission.
The neurotransmitter is the ligand and binds to and opens ion channels in the postsynaptic membrane. There are then changes in the ionic permeability of the postsynaptic cell membrane. This leads to a rapid and reversible change in the membrane potential of the postsynaptic cell.
Describe excitatory and inhibitory synapses and postsynaptic potentials.
excitatory - makes postsynpatic neurone more likely to fire an action potential. brings Vm nearer to the threshold and increases the chance of the AP firing. It also increases excitability and summates to elicit an action potential.
inhibitory - makes postsynpatic neurone less likely to fire an action potential.
Describe summation and excitability – target for drugs.
Summation is from both from multiple simultaneous inputs (spatial summation), and from repeated inputs (temporal summation).
excitability - the ability to generate a large, rapid change of membrane voltage in response to a very small stimulus
Describe metabotropic receptors and slow synaptic transmission.
A metabotropic receptor a type of membrane receptor that initiates a number of metabolic steps to modulate cell activity.
neurotransmitters have to pass the synpase by diffusion, which is relatively slow.
Describe pharmacological action of diazepam.
effects are thought to result from a facilitation of the action of gamma aminobutyric acid (GABA), an inhibitory neurotransmitter in the central nervous system
List the functions of smooth muscle.
found in walls of hollow organs, work automatically, stomach, arterioles, airways
Compare and contrast the properties of smooth muscle and skeletal muscle.
skeletal muscle is striated, smooth muscle does not act on structures, both need calcium for contraction, smooth muscle is single unit and multi unit.
Describe the functional significance of single-unit behaviour of smooth muscle and explain how co-ordination of this activity is achieved.
cells are close together with few innervations of varicosities. electrically coupled to eachother via gap junctions. myogenic
Identify two sources of calcium ions that can promote contraction of smooth muscle.
calcium in the sarcoplasmic reticulum, extracellular calcium
Provide one example of how the autonomic nerves can increase and decrease smooth muscle activity and link your answer to a physiological response.
the autonomic nerve fires an action potential which leads to the release of neurotransmitters from the varicosities to the muscle cell.
Understand the function of the actomyosin system and recognise its importance for movement in the human body.
the actin-myosin complex that forms in the cytoskeleton and allows for muscle contraction. the myosin head binds to actin using ATP
