Nervous Coordination + Muscles (15) Flashcards
What is the cell body/ role?
Contains nucleus and organelles eg. Mitochondria
What is the dendrites/ role?
Carry nerve impulses towards cell body many
different nerve pathways to contract muscle
What is myelin/ role?
Insulates axon which makes electrical impulses to jump to nodes of ranvier increasing the speed. (Schwann cells)
What type of conduction is used in myelinated neurones?
Saltatory conduction.
Where does sensory neurones carry impulse?
Receptor to CNS
Where does relay neurones carry impulses?
Within the CNS
Where does motor neurone carry impulses?
CNS to Effectors
Blurt the 4 points of establishing a resting a potential difference in a nerve cell
More Na+ pumped out than K+ in.
K+ can diffuse out via K+ channels.
Overall more positive outside than inside.
Inside relatively speaking negative compared to outside.
Describe the all or nothing principle
Once threshold met and action potential always triggered.
Doesn’t meet threshold no action potential.
Action potential always the same size.
Blurt the 6 points of generation of an action potential
Resting potential- around -70 mV
Stimulus- voltage gated Na+ open and Na+ flow inside the axon making it less negative
Depolarisation- if threshold (-55 mV) more Na+ channels open causing an influx of Na+
Re polarisation- around +30 mV, Na+ channels shut, K+ channels open. So K+ flow out axon and membrane re polarised.
Hyperpolarisation- excess of K+ leave axon dropping below -70 mV
Refractory period- various ion pumps and channels work together to restore the membrane back to resting
Describe the refractory period
Reset
During this period a neurone cannot generate another action potential
Sodium ion channels remain closed during re polarisation preventing depolarisation.
List the three factors effecting the speed of an action potential
Mylenation
Axon diameter
Temperature
Describe why myleination effects speed of a nerve impulse
Electrical impulse jumps over myelin, to nodes of ranvier which increases the speed.
Why does axon diameter affect speed of an action potential?
Larger axon diameter less resistance to ion flow. So wave of depolarisation travels faster
Explain how temperature effects speed of an action potential
Accelerates diffusion of ions however above 40 degrees proteins denature.
Blurt the 10 steps of transmission across a synapse
- AP reaches synaptic knob
- Ca2+ diffuse into axon
- Synaptic vesicles fuse with presynaptic membrane
- Neurotransmitter released into synaptic cleft and diffuses across
- Neurotransmitter fuses with receptor site on post-synaptic membrane
- Voltage gates open allowing Na+ to diffuse into post synaptic membrane
- AP may be initiated in post synaptic nerve
- Neurotransmitter broken down by acetylcholinesterase
- Breakdown products diffuse back across the synaptic cleft
- Acytlcholine resynthesises by ATP from mitochondria in pre synaptic neurone
What is an excitory neurone and does it hyperpolarise or depolarise?
Depolarisation
Will trigger AP if threshold met eg. Acetylcholine in CNS
What is an inhibitory neurotransmitter and does it hyperpolarise or depolarise?
Hyperpolarisation
Prevents AP by opening Cl- channels on post synaptic membrane—- influx of negative ions in less likely an AP.
What is spatial summation?
Neurones converge on single post synaptic membrane. Combined input triggers an action potential
What is temporal summation?
Repeated firing by a presynaptic membrane leads to continued neurotransmitter release. More likely trigger an action potential.
What is skeletal muscle?
Voluntary muscle to move skeleton
What is cardiac muscle?
Heart muscle
What is smooth muscle?
Involuntary muscle found in walls of gut and blood vesicles
What is the sarcoplasm?
Cytoplasm of a muscle fibre
