Nervous Coordination and Muscles (Chapter 15) Flashcards
What are the three types of neurons?
Sensory, Intermediate and Motor
What do most neurons have?
Cell body, dendrites, axon, Schwann cells, myelin sheath and nodes of Ranvier
Where do electrical impulses move from and to?
Dendrite to Axon
How is resting potential maintained?
1) Na+ ions pumped out of axon by sodium-potassium pump (using active transport - ATP needed)
2) 3 NA+ ions pumped out for every 2 K+ ions.
3) Membrane is more permeable to potassium
Describe the stages of Action Potential
1) Some K+ ion channels always open up with K+ leaving from the axon and out of the cell by diffusion
2) Voltage-gated Na+ channels open
3) Sodium ions enter axon by diffusion
4) Axon becomes depolarised (have +40mV charge) so more Na+ channels open up (positive feedback)
5) Na+ ion channels close
6) More K+ ion channels open
7) K+ ions leave axon by diffusion
8) Axon become hyperpolarised (-85mV)
9) Some K+ ion channels close
10) Sodium-Potassium pump restores resting potential (-65mV)
What are the stages in the reflex arc?
Stimulus > Receptor > Sensory Neurone > Intermediate Neurone > Motor Neurone > Effector
What is the refractory period?
Time during which a new action potential cannot be generated as the cell is in hyperpolorisation. Sodium channels are closed so sodium cannot enter. Helps action potentials pass in one direction and form discrete impulses.
What is the all or nothing principle?
If enough sodium ions enter cell and reaches threshold, it will cause more sodium ion voltage gated channels to open - if not, no impulse. All action potentials are the same size +40mV.
Why does oxygen consumption increase when a neurone transmits impulses?
- More respiration
* More ATP supplied for the active transport in Na+/K+ pump
Describe the stages of synaptic transmission
1) Action potential causes calcium ion channels to open and calcium ions to enter synaptic knob by diffusion.
2) Causes synaptic vesicles to fuse with presynaptic membrane and release neurotransmitter into synaptic cleft.
3) This diffused across synapse.
4) Binds with specific receptor sites on post synaptic neurone.
5) Opens either sodium channels (excitatory) or chloride channels (inhibitory) which either increases or reduces action potentials in post synaptic neurone.
What is the sarcomere?
Distance between Z lines which gets shorter during muscle contractions.
What are I bands?
Region of just actin, gets shorter during contraction.
What are A bands?
Where actin and myosin overlap - stays the same length.
Describe the stages in muscle contraction
1) Action membrane arrives in muscle cell membrane (by sodium ions etc.)
2) Carried across sarcoplasm in T tubules.
3) Causes sarcoplasmic reticulum to release Ca2+ ions into microfibrils which bind to troponin.
4) Causes tropomyosin to be displaced - reveals myosin binding site on actin.
5) Allows myosin head to attach to actin binding site and form cross bridges,
6) Myosin heads change angle and release ADP causes actin filament to slide relative to myosin.
7) ATP used to detach myosin from actin.
8) ATPase breaks down ATP into ADP.
What are fast twitch muscle fibres used for and what are their adaptations?
Used for explosive movement
- Enzymes for anaerobic respiration
- Phospocreatine for ATP regeneration
- Higher quantity of myosin for powerful contractions.
What are slow twitch muscle fibres used for and what are their adaptations?
Used for endurance
- Lots of mitochondria for aerobic respiration
- Good supply of glycogen
- Rich capillary network to provide oxygen
Why do muscle cells contain glycogen granules?
Store glucose for respiration.
What is the importance of hydrolysis of ATP in muscle cells?
Provides energy used in muscle contraction to break cross bridges and detach myosin heads. Allows myosin heads to move back to their original position for process to continue.
What is the role of calcium ions in muscles?
Binds to troponin - causes tropomyosin to be displaced - revealed myosin binding site on actin (allowing actinomyosin cross bridges to form).
Activates ATPase (on myosin)
What is the role of tropomyosin in muscles?
- Blocks myosin binding site on actin
* Moves from binding site du to Ca+ ions allowing cross bridges to form.
What is the sliding filament theory?
When contracted, myosin and actin overlap more - Actin moves along myosin - Actin pulls Z lines closer together.
What are synapses?
The gaps between neurons.
Why are synapses and neurons unidirectional?
Neurotransmitters are only stored in pre-synaptic neurone and receptors only in post-synaptic neurone
What neurotransmitter does cholinergic use?
Acetylcholine
What can affect synaptic transmission?
Drugs
