Nervous System Flashcards
What is the CNS made up of
Spinal chord and brain
What is the peripheral system made up of
All the other neurones
What does the peripheral system split into
Systematic nervous system and the autonomic nervous system
Systematic nervous system
Conscious control
Autonomic nervous system
Unconscious body activating
What is the autonomic nervous system made up of
Parasympathetic- slows things down - acytlcholine ….
Sympathetic-speeds things up- noradrenaline
Receptor
Specific, will only detect one type of stimulus. Can be cell or protein, transforms stimuli into electrical impulse ( chemical change)
Sensory neurone
Single long dendron, single short axon
Relay neurone
Within the CNS, many short dendrites, many short axons
Motor neurone
Many short dendrites, single long axon, ends with a neuromuscular junction
Effector
Muscle or gland, brings about a response
Potential difference
More positive ions on outside than on the inside so we say this is the resting potential
Resting potential
When,
(1) SODUIM POTASSIUM PUMP: active transport 3Na+ out, 2K+ in
(2) VOLTAGE GATED SODIUM ION CHANNEL: closed, membrane is not permeable to Na+
(3) POTASSIUM ION CHANNEL: open, some k+ diffuses out down electrochemical gradient, doesn’t reach equilibrium due to positive charge on outside
What makes up an action potential ( in order)
- Resting potential
- Generator potential
- Threshold
- Depolarisation
- Depolarisation
- Re polarisation
- Hyper polarisation
What is the refractory period
Another action potential cannot be started, makes action potentials- discrete ( don’t overlap)- unidirectional (one way)
AP:resting potential
Sodium potassium pump
Active transport
Na out
k in
AP Generator potential
Weak stimulus Some Na channels open Some Na diffuses in Does in reach threshold Nak pump stores resting potential
AP Threshold
Greater potential reaches threshold
Many voltage gated Na channels open
Na diffuses into axon
Positive feedback
AP depolarisation
Na channels are open
Na diffuses in
AP Repolarisation
K channels open ( voltage gated)
K diffuses out
Voltage gated Na close
AP Hyperpolarosation
When membrane potential is more negative than resting potential , k channels close
The all or nothing law
If a generator potential reaches threshold it will trigger an action potential
What’s the myelin sheath
Schwann cells make the myelin, it’s an electrical insulator - prevents depolarisation, prevents movement of ions in/out of the neurone
Saltatory conduction
When an action potential jumps between the nodes of ranvier
Points to remember about saltatory conduction
Speeds up transmission of nerve impulse, cytoplasm conducts enough charge to depolarise the next node
Nodes of ranvier
The gaps in the myelin sheath, lots of Na and K channels
What can only happen at the nodes of ranvier
Depolarisation
Diameter of the axon
Less resistance, more surface area for ion movement, greater diameter the faster the speed of action potential
Synapse
A junction between two neurones
Describe the steps of a cholinergic synapse
- AP arrives at presynaptic knob 2. Ca channels open and diffuse in 3. Causes vesicles to fuse with membrane 4. Ach diffuses across cleft 5. Ach binds to receptors on postsy 6. Some Na channels open and diffuses in 7. Voltage gated Na channels open 8. AP triggered at postsy 9. Acetylcholinerase breaks down Ach 10. Products reabsorbed into presy
Evidence that synapse are unidirectional
Only receptors on the post synaptic membrane, neurotransmitters released from presy, diffuse from high to low concen across synaptic cleft
Synaptic divergence
When one neurone joins many neurones, spreads the AP to other parts of the body
Synaptic convergence
When many neurones join a single neurone, amplifies signal
Spatial summation
When neurotransmitters from multiple neurones combine to trigger an action potential in a post synaptic neurone
Temporal summation
A strong stimulus will cause more frequent AP’s, release more neurotransmitters which add up to trigger an AP in the postsy
Neuromuscular junction
A synapse between a motor neurone and a muscle fibre
Differ eat compared to a cholinergic synapse
More receptors on postsy, so an AP is always generated in postsy, acetlycholinerase found in pits in postsy, receptors called nichotinic chollinergic receptor
Exteroceptors
Respond to a stimuli from the external environment
Enteroceptors
Respond to stimuli from the internal environment
Proprioceptors
Respond to tension with tendons and muscles
Why is there lots of mitochondria in the synaptic bulb
ATP for active transport, making neurotransmitters, synaptic vesicles-Golgi, removal of calcium after AP
Cholinergic synapse
Neurones that release acytlcholine
Adrenergic synapse
Neurones that relates noradrenaline
