Lecture 11
The Synapse
- A junction between 2 communicating neurons
- synaptic cleft – impulse must be conveyed across the cleft
- Neural communication across the cleft is synaptic transmission
- Neurotransmitter is used the communication
- There Is pre-synaptic cleft and post-synaptic cleft
Synaptic transmission
- Excitatory neurotransmitters
o increase Na+ ions into postsynaptic
o Bring membrane closer to threshold
o Making action potential (need to reach -55mv) more likely
- Inhibitory neurotransmitters
o Increase Cl- ions into neuron or flow of K+ ion of the neuron
o Makes change inside the neuron more negative
o Making action potential less likely
Neurotransmitters
- Produced in synaptic knobs and store in synaptic vesicles
- Acetylcholine, monoamines, amino acid and neuropeptides
- Some neuron produces one type, some produce two types
Neurotransmitter recycling
- Enzymes in synaptic clefts and on postsynaptic membrane rapidly decompose the
neurotransmitters after their release -> Acetylcholinesterase (Ach E)
o Break down Ach
- Some will travel back into the presynaptic neuro for reuse -> reuptake
Facilitation
- Increase release of Neurotransmitter in response to one
impulse; this increases the likelihood that the postsynaptic
neuron will reach threshold
Convergence
- Impulses to a single neuron within a pool from two or more
fiber
Divergence
- Impulses to a neuron in a pool to several output fibers
, Types of nerves
- Nerve – a bundle of nerve fibers (axons) in PNS
o Sensory (afferent) nerves
Conduct impulses to the CNS
Axons are called sensory fibers
o Motor (efferent) nerves
Carry impulses from the CNS to effectors
Axons are called motor fibers
o Mixed nerves
Carry both sensory and motor fibers
Most nerve are this type
- Connective tissue coverings
o Epineurium – outer covering of a nerve
o Perineurium – covering around fascicles of nerve
fibers
o Endoneurium – covering around individual nerve
fibers
Neural pathways
- The routes nerve impulses travel are called neural pathways, the simplest of which is a
reflex arc
- Components:
o Sensory receptor – detects changes
o Sensory neurons – carries info from a receptor
towards the CNS
o Interneuron – reflex center
o Motor neuron – carries a command to
effectors
o Effector – muscle gland; respond to the initial
change
Meanings
- 3 membranes called meninges that lie between the skull
bones and vertebrae and the soft CNS tissues
o Dura mater
Outermost layer of meninges
Made up of tough, dense connective
tissue and is very thick
Contains many blood vessels
The Synapse
- A junction between 2 communicating neurons
- synaptic cleft – impulse must be conveyed across the cleft
- Neural communication across the cleft is synaptic transmission
- Neurotransmitter is used the communication
- There Is pre-synaptic cleft and post-synaptic cleft
Synaptic transmission
- Excitatory neurotransmitters
o increase Na+ ions into postsynaptic
o Bring membrane closer to threshold
o Making action potential (need to reach -55mv) more likely
- Inhibitory neurotransmitters
o Increase Cl- ions into neuron or flow of K+ ion of the neuron
o Makes change inside the neuron more negative
o Making action potential less likely
Neurotransmitters
- Produced in synaptic knobs and store in synaptic vesicles
- Acetylcholine, monoamines, amino acid and neuropeptides
- Some neuron produces one type, some produce two types
Neurotransmitter recycling
- Enzymes in synaptic clefts and on postsynaptic membrane rapidly decompose the
neurotransmitters after their release -> Acetylcholinesterase (Ach E)
o Break down Ach
- Some will travel back into the presynaptic neuro for reuse -> reuptake
Facilitation
- Increase release of Neurotransmitter in response to one
impulse; this increases the likelihood that the postsynaptic
neuron will reach threshold
Convergence
- Impulses to a single neuron within a pool from two or more
fiber
Divergence
- Impulses to a neuron in a pool to several output fibers
, Types of nerves
- Nerve – a bundle of nerve fibers (axons) in PNS
o Sensory (afferent) nerves
Conduct impulses to the CNS
Axons are called sensory fibers
o Motor (efferent) nerves
Carry impulses from the CNS to effectors
Axons are called motor fibers
o Mixed nerves
Carry both sensory and motor fibers
Most nerve are this type
- Connective tissue coverings
o Epineurium – outer covering of a nerve
o Perineurium – covering around fascicles of nerve
fibers
o Endoneurium – covering around individual nerve
fibers
Neural pathways
- The routes nerve impulses travel are called neural pathways, the simplest of which is a
reflex arc
- Components:
o Sensory receptor – detects changes
o Sensory neurons – carries info from a receptor
towards the CNS
o Interneuron – reflex center
o Motor neuron – carries a command to
effectors
o Effector – muscle gland; respond to the initial
change
Meanings
- 3 membranes called meninges that lie between the skull
bones and vertebrae and the soft CNS tissues
o Dura mater
Outermost layer of meninges
Made up of tough, dense connective
tissue and is very thick
Contains many blood vessels
