Define central nervous system.
The complex of nerve tissues that control the activities of the body. Comprised of the brain and spinal cord.
Define peripheral nervous system.
Neuron system apart from brain and spinal cord. Carries signals from receptors to the spinal cord and brain. Motor neurons carry signals from the CNS to its effectors.
Main apparatus for receiving signals from other cells.
Main conducting unit of the neuron, across which the electrical signal is carried.
Define myelin sheath.
Protects axon and prevents interference between axons as they pass along bundles. Makes conduction faster.
Define node of ranvier.
Speeds up propagation of action potential and saves energy.
Define axon terminals.
Facilitates conveying of electronic messages between neurons.
Define saltatory conduction.
The nerve impulse jumping from one node of ranvier to the next.
Define continuous conduction.
Conduction along the axon without jumping. Much slower than saltatory conduction.
What is resting potential in neurons?
The electrical potential across the membrane of a neuron that is not conducting an impulse. Is used to repolarize a neuron inbetween impulses. It is negative in neurons.
Explain the Na+/K+ pump in neurons.
3 Na+ ions are pumped out for every two K+ ions pumped in by active transport.
When does the K+ channel open and in what direction are ions moving?
-Closed during depolarization -Open during repolarization, allowing K+ to diffuse out of the membrane, making membrane potential decrease before it is restored.
When does the Na+ channel open and in what direction are ions moving?
-Opening leads to depolarization as Na+ diffuses across its concentration gradient into the neuron. This leads to reversing the charge imbalance across the membrane, making it positive.
How is a resting potential maintained in a neuron? Why is it negative?
-Na+/K+ pump creates a charge imbalance by pumping out more Na+ than it pumps in K+. -Organic proteins in the membrane are also negatively charged.
Define action potential.
Depolarization and repolarization of the neuron to conduct an electrical impulse.
Outline an action potential, starting at the resting potential.
-Resting potential maintained through Na+/K+ pump -Depolarization is triggered by the arrival of an action potential. -Voltage-gated Na+ channels open if change in membrane potential rises above threshold. Charge imbalances switched as Na+ diffuse into the neuron. -Na+ diffusion triggers K+ channels to open, causing K+ to rush out of the neuron, causing repolarization.
Resting potential: How is the internal potential? Where are the sodium ions? Where are the potassium ions? What membrane proteins are used?
-Internal potential is negative -Sodium ions are outside -Potassium ions are inside -Na+/K+ pump is used
Action potential: How is the internal potential? Where are the sodium ions? Where are the potassium ions? What membrane proteins are used?
-Internal potential positive -Sodium ions inside -Potassium ions outside -Voltage-gated channels
When the neuron becomes more negative than its resting potential before returning to it.
How is the one-way direction of a nerve impulse maintained?
-Na+ diffuse outwards and in the opposite direction of the pulse while Na+ inside the neuron diffuse along with the pulse.
Outline the process of synaptic transmission.
-Nerve impulse reaches pre-synaptic membrane. -Depolarization of pre-synaptic membrane-> Ca2+ to diffuse into the neuron. -Influx of Ca2+ causes vesicles containing neurotransmitter to move to pre-synaptic neuron and then bind with it -Neurotransmitters released to synaptic cleft by exocytosis -Neurotransmitters diffuse across cleft and bind to receptors on post-synaptic membrane -Binding causes adjacent sodium channels to open, causing an action potential.
What is acetylcholine?
Neurotransmitter used in synaptic transmission
Explain the antagonistic nature of the action of muscles.
As one muscle contracts, the other releases, producing opposite movements at a joint.
What are skeletal muscle fibres also called?
Plasma membrane surrounding fibre,
Define sarcoplasmic reticulum.
Modified version of endoplasmic reticulum, sending electrical signal down muscle
What is the functional unit of the myofibril?
Describe the sliding filament theory of muscle contraction.
-During muscle contraction, myosin filaments pull the actin filaments inwards towards the center of the sarcomere, shortening the sarcomere and thus the whole muscle fibre -Myosin filament heads bind to actin filaments, creating cross-bridges through which they exert a force, causing the contraction.
What role does Ca2+ have in controlling muscle contractions?
Released by sarcoplasmic reticulum when a muscle fibre receives a signal from a motor neuron. Bind to troponin, causing tropomyosin to move, thus exposing actin's binding site.
What role does tropomyosin have in controlling muscle contractions?
Blocks binding sites on actin
What role does troponin have in controlling muscle contractions?
Causes tropomyosin to move
Outline the contraction of skeletal muscle.
-Action potential initiated in muscle cell membrane. -Sarcoplasmic reticulum reacts to action potential by releasing Ca2+ ions. -ATP binds to myosin heads and causes them to break cross-bridges by detaching from the binding sites. -Hydrolysis of ATP to ADP and phosphate provides energy for heads to swivel outwards away from the center of the sarcomere -Energy stored in myosin head when it was cocked causes it to swivel inwards towards the center of the sarcomere, moving the actin filament a small distance. -Calcium ions pump back into the sarcoplasmic reticulum so the regulators protein moves and covers the binding sites on actin.
What is the role of sinovial fluid in the joint?
Lubricates the joint.
What is the role of cartilage in the joint?
Covers the bones and prevents friction.
What is the role of the joint capsule?
Seals the joint and helps prevent dislocation.