Coordination Flashcards
Describe the structure of a motor neurone
Diagram dendrites Cell body Cytoplasm containing many mitochondria and RER Nucleus Schwann cell Nucleus of Schwann cell Node of ranvier Long axon Synaptic knob Terminal branches
Describe the structure of a myelin sheath and explain its role in speed of transmission
Schwann cells
Surround axon of neurons
Mostly lipid
Speed up transmission by insulating the axon membrane
No depolarization can occur
only occur at node of Ranvier
Action potentials jump from one node to the next which is saltatory conduction
Local circuits exist from one node to the next
Speed up transmission up to 50 times than unmylienated neuron
Describe the actions of a reflex arc
Strong Stimulus is detected by receptor
AP is sent along sensory neuron
Which is sent to a synapse with a relay neuron
Action potential is sent to effector in motor neuron
Doesnt involve conscious part of the brain
Useful in responding to danger
Fast
How is the resting potential maintained in an axon
Axon membrane is impermeable to K+ and Na+
Sodium potassium pump has ATP binding site
For pumping to occur ATP is used
3Na+ out and 2 K+ in
Through their protein channels
More potassium channels than sodium
Potassium diffuses back out faster than sodium diffuses back in
Explain how an action potential is transmitted along a motor neuron
▪️Voltage gated Na+ channels open allowing Na+ to enter (depolarization)
▪️changes the pd across the mem making it less negative inside
▪️sodium ion voltage gated channels close
▪️K+ channels open
▪️k+ diffuse out of the axon down the conc gradient repolarizing the membrane
▪️local circuits,myelin sheath,saltatory conduction
Describe how chemoreceptors in the taste buds send nerve impulses
▪️Entry of sodium ions depolarizes mem in the sensory zone
▪️this stimulates Ca2+ channels to open
▪️entry of calcium ions stimulates movement of vesicles and release neurotransmitter by exocytosis
▪️if stimulation is above threshold impulses travel to brain along sensory neuron
Describe how a nerve impulse crosses a cholierigic synapse
▪️An action potential arrives at pre synaptic membrane
▪️stimulates opening of volatge gated Ca2+ channels
▪️calcium ions diffuse in to pre synaptic knob
▪️stimulates vesicles to move and fuse with membrane
▪️release ach by exocytosis in to synaptic cleft
▪️diffuses across the membrane
▪️binds and changes shape of protein receptors on post synaptic membrane
▪️stimulates opening of Na+ channels
▪️Na+ diffuse in to post synaptic membrane
▪️depolarization
▪️acteylcholinestrase breaks down ach in to acetate
And choline
Describe the role of synpases
▪️ensure one way transmission
Since receptor is on one end and vesicles on the other
▪️wide range of responses due to interconnection of many nerve pathways
▪️inhibitory synapses affect other synapses
▪️involved in memory and learning due to new synapses being formed
▪️summation
Describe how muscles contract
▪️muscle contracts which stimulates Ca2+ from SR to be released and bind to troponin
▪️this stimulates troponin mol to change shape
▪️troponin and tropomyosin move to diff positions in the thin filaments exposing actin mol
▪️myosin heads bind forming cross bridges
▪️myosin pulls actin filaments towards center of sarcomere
▪️power stroke
▪️ATP hydrolses heads to lead go of actin
▪️heads tip back again
Explain the role of hormones in maintaining human menstrual cycle
▪️Fsh and LH are released by ant pituitary ▪️Graafian follicle develops ▪️estrogen produced by follicle ▪️eostrogen conc rises for first 12 days ▪️causes endometrium to thicken ▪️surge in LH around day 14 ▪️stimulates ovulation ▪️corpus luteum develops ▪️produces progestrone ▪️maintains thickness of endometrium ▪️if no fertilisation LH secretion is inhibted ▪️corpus leutum degenrates ▪️progestrone conc falls ▪️endometrium breaks down ▪️negative feed back
Outline the biological basis for contraceptive pills containing estorgen and progesterone
Progesterone and estrogen inhibt ant pituatry gland
Negative feedback
No fsh or lh produced
No primary oocyte made
No ovulation
Cervical mucus made to try and stop sperm from entering
Endometrium thin and not ready for implantation
Describe the ultrastructure of a striated muscle fibre
▪️Myosin heads attached to m line ▪️Fibrous ▪️actin filaments are made of globular chain ▪️troponin and tropomyosin bind to actin to prevent myosin head from attaching ▪️T-tubules ▪️sarcomere is cell surface membrane ▪️sarcoplasmic reticulum has proton pumps ▪️sarcoplasm has many mitochondria ▪️myofibrils ▪️I band only actin ▪️H bands only myosin ▪️A band both
Describe the role of the neuromuscular junction,t tubules and SR in stimulating contraction in ms cells
▪️action potential at pre synaptic membrane ▪️VG Ca2+ channels open ▪️Ca2+ enter ▪️stimulates movement of vesicles to fuse with pre synaptic membrane ▪️exocytosis of Ach ▪️diffuses across synaptic cleft ▪️binds to receptors on post synaptic membrane ▪️sodium ion channels open ▪️allow depolarization of sarcolemma ▪️depolarization spreads down T-tubules ▪️VG Ca2+ channels open ▪️Calcium ions diffuse out of SR ▪️calcium ions diffuse in to sarcoplasm ▪️calcium ions bind to troponin
