Control And Coordination Flashcards
Dendrites
Carries nerve impulse towards cell body
Axons
Carries nerve impulse away from cell body
Some enclosed with myelin shieth
Synapse
Junction between neurons or muscles
Myelin shieth
Insulates axons
Speeds up conduction of nerve impulse
Made or Schwann cells
Nodes of ranvier
Founds between myelin shieth
Types of neurons
Sensory neuron (afferent), relay neurons, motor neuron (efferent)
Reflex arc
Very strong stimulus detected by receptors
Action potential generated in sensory neurons
Sensory neurons connected to spinal cord
Through synapse: action potential passed into relay neurons
Through synapse: action potential passed into motor neurons
Cholinergic synapse of neuromuscular junction
Effectors carry out response
Reflex arc (definition)
Pathway where nerve impulse are carried along during reflex action
Advantages of reflex arc
Fast, involuntary, protects from harm
Impulse
Brief change in charge across membrane
At rest
More negative on the inside than the outside
Resting potential: - 70 mv
When impulses are formed
More positive on the inside than outside
Action potential or depolarization: 30 mv
Roles of receptor cells
- Detects a stimuli
- Acts as transducers
Taste chemoreceptor cells (nacl)
Sodium ions into cell microvilli
Membrane depolarization
Voltage gated calcium ions channel open
Calcium ions enter cells
Triggers movement of vesicles containing neurotransmitters
Neurotransmitters releases
Stimulates an action potential in sensory neurons
Resting potential
Membrane potential is At rest
No impulse formed or transmitted
Inside of axon more negatively charged than outside
Neurons are polarized and maintained at -70 mv
How is a resting potential generated?
. Sodium and potassium pumps
. 3 sodium ions pumped out, 2 potassium ions pumped in
. Creates an electrochemical charge gradient
. High concentration of sodium ions outside and high concentration of potassium ions inside the axon
. Movement of Na inside and K outside via channel proteins
. More k ions leaving man sodium ions entering as membrane is more permeable towards potassium ions
. The leaving potassium ions are responsible for maintaining a resting potential
Depolarization
Voltage gated potassium ion channel closes
Voltage gated sodium ion channels open
Na ions enters making membrane less negative
Size of action potential is generated at +30 mv
Higher the strength of stimulus, higher the frequency of action potential
Repolarization
Voltage gated sodium ion channel closes
Voltage gated potassium ion channel opens
K moves out of cell
Inside of membrane becomes more negative: - 70 mv
Hyperpolarization
Voltage gated potassium ions channel And voltage gated sodium ion in annex remains closed
Slight delay in potassium ion channels
Thus excess K ions have already moved out
Membrane potential: less than -70 mv
How does action potential transmit along non myelin shieth
Depolarization moves to the next region as positive ion moves to negative region
Local circuit is set up
Voltage gated sodium ion channel opens at the next region and an action potential is generated
Threshold potential
Minimum potential needed for an action potential to be generated
Depolarization > = 50 mv generates an action potential
Fixed at +30 mv
Encase of myelin shieth
Faster transmission
Insulates axons
Action potential and local circuit set up at node of ranvier
Role of synapse
- ensures one way transmission
- Involved in memory and learning
- Filters out low level stimuli
- Inter connection y nerve pathways
cholinergic synapse
1 Action potential reaches pre synaptic membrane
2 voltage gated calcium ions channel opens
3 ca ions enter presynaptic membrane
4 vesicles containing ach fuses with pre synaptic membrane
5 exocytosis occurs
6 ach diffuses across synaptic cleft and fuses with receptor protein on post synaptic membrane
7 receptor protein changes shape and sodium ion channels remain open
8 sodium ions enter post synaptic membrane and action potential is generated
9 ach broken down by acetylcholinesterase into acetate and choline
