General Biology II: Synapses

Presynaptic cell

Signal comes from this cell → which synthesizes and stores neurotransmitters where chemicals will cross the synaptic cleft which will signal the postsynaptic cell

Postsynaptic Cell

This cell will start a new action potential in this cell

Presynaptic Neuron

Action potential will depolarize membrane, allowing the voltage gated Ca²⁺ to open and the vesicles fusing with the membrane to release a neurotransmitter

(PRESYNAPTIC)

1) Action Potential Arrives at synaptic terminal, which depolarizes membrane

2) Your voltage gated Ca²⁺ will open and allow Ca²⁺ to diffuse

3) Ca²⁺ increase can cause vesicles to fuse with terminal membrane

4) Neurotransmitters are released from your synaptic cleft, which will diffuse to bind to a postsynaptic neurons’ receptors

(POSTSYNAPTIC)

5) Signals received from neurotransmitters, which will bind to ligand gated ion channels

6) Ions diffused across postsynaptic membrane (your PSP)

7) Either get to Excitatory Postsynaptic Potential or Inhibitory Postsynaptic Potential

SEQ the pathway of a synaptic transmission

(PRESYNAPTIC)

1) Action Potential Arrives at synaptic terminal, which depolarizes membrane

1st step of the pathway of a synaptic transmission

(PRESYNAPTIC)

2) Your voltage gated Ca²⁺ will open and allow Ca²⁺ to diffuse

2nd step of the pathway of a synaptic transmission

(PRESYNAPTIC)

3) Ca²⁺ increase can cause vesicles to fuse with terminal membrane

3rd step of the pathway of a synaptic transmission

(PRESYNAPTIC)

4) Neurotransmitters are released from your synaptic cleft, which will diffuse to bind to a postsynaptic neurons’ receptors

4th step of the pathway of a synaptic transmission

(POSTSYNAPTIC)

5) Signals received from neurotransmitters, which will bind to ligand gated ion channels

5th step of the pathway of a synaptic transmission

(POSTSYNAPTIC)

6) Ions diffused across postsynaptic membrane (your PSP)

6th step of the pathway of a synaptic transmission

(POSTSYNAPTIC)

7) Either get to Excitatory Postsynaptic Potential or Inhibitory Postsynaptic Potential

7th step of the pathway of a synaptic transmission

Excitatory Postsynaptic Potential (EPSP)

This type of postsynaptic potential will cause depolarization

Excitatory Postsynaptic Potential (EPSP)

This type of postsynaptic potential will cause depolarization

Inhibitory Postsynaptic Potential (IPSP)

This type of postsynaptic potential will cause hyperpolarization

It depends on the information from chemical synapses (signal receival of neurons)

How can a postsynaptic neuron determine whether it is EPSP or IPSP?

No

If the distance of the synapse is small, can an action potential be triggered?

Not really

If the distance of the synapse is large, can an action potential be triggered?

Temporal

Summation type when you have 2 EPSP at a single synapse after each other (rapid and time matters!)

Spatial

EPSPs same time, but different synapses (different sources, but still getting to the signal)

Axon hillock will integrate to the membrane potential to reach threshold

When the 2 summations will have interplay, what will happen to the membrane potential?

Neurotransmitters

Small chemical signals across synapses

Gene expression and Signal Transduction

When the nervous system is developing embryonically, what are the 2 traits that it will have?"

Neuronal Plasticity

When the brain is developed and remodeled according to experiences. This will weaken based on the activity of neurons coinciding with other neurons

Short-Term Memory

This is information that is briefly held and difficult to retrieve. Although it will be stored in the cerebral cortex, it will make temporary links with the hippocampus

Long Term Memory

This is information where memory is stored in the cerebral cortex and you are able to RETRIEVE it back

1) High Frequency of Action Potentials

2) Depolarization of a second synapse

What are the conditions of the presynaptic neuron before going through LTP?

MUST have glutamate receptors (NMDA & AMPA)

What are the condition(s) for the postsynaptic neuron in order for it to undergo LTP?

(BEFORE LTP)

1) NMDA receptors are open to glutamate, but Mg²⁺ is blocking it

(DURING LTP)

2) Depolarization will have NMDA release Mg²⁺

3) Your glutamate neurotransmitters are taken in as AMPA receptors that can activate Ca²⁺ (continuously diffused)→ PSP can be created to generate AP

(AFTER LTP)

4) NMDA & AMPA receptors are active where lots of depolarization occurs where action potential is reached

SEQ LTP Pathway

(BEFORE LTP)

1) NMDA receptors are open to glutamate, but Mg²⁺ is blocking it

1st step of LTP pathway

(DURING LTP)

2) Depolarization will have NMDA release Mg²⁺

2nd step of LTP pathway

(DURING LTP)

3) Your glutamate neurotransmitters are taken in as AMPA receptors that can activate Ca²⁺ (continuously diffused)→ PSP can be created to generate AP

3rd step of LTP pathway

(AFTER LTP)

4) NMDA & AMPA receptors are active where lots of depolarization occurs where action potential is reached

4th step of LTP pathway

1) Sensory Reception (stimulus is detected by cells/receptors)

2) Sensory Transduction - Conversion of stimulus to receptor potential → this will change it to membrane potential

3) Transmission - When sensory info travels through your Nervous System that causes depolarization (AP trigger = higher receptor potential)

4) Perception- Brain processes information and integrates by your sensory neurons

SEQ Sensory Pathway

Sensory Reception

This is when the stimulus is detected by cells + receptors

Sensory Transduction

Conversion of stimulus to receptor potential where there is a change in membrane potential

Transmission

When sensory info travels through your nervous system that causes depolarization and higher receptor potential

Perception

When your brain processes information and integrates by your sensory neurons

1) Sensory Reception (stimulus is detected by cells/receptors)

1st step of Sensory Pathway

2) Sensory Transduction - Conversion of stimulus to receptor potential → this will change it to membrane potential

2nd step of Sensory Pathway

3) Transmission - When sensory info travels through your Nervous System that causes depolarization (AP trigger = higher receptor potential)

3rd step of Sensory Pathway

4) Perception- Brain processes information and integrates by your sensory neurons

4th step of Sensory Pathway

Chemoreceptors

When the stimulus binds to taste/smell receptors

Mechanoreceptor

When the stimulus binds to touch and hearing

Photoreceptors

Stimulus binds to light & seeing receptors

Hearing

When there are changes sensed in external vibrations

Equilibrium

Balance is controlled by sensing movement of fluid in ears

1) Outer ear

• Pinna will collect your sound waves

• Auditory Canal: channels waves to tympanic membrane

• Tympanic Membrane (ear drum): Thin membrane that vibrates and transmits to middle ear

2) Gets to the middle ear

• Ossicles: (your 3 small bones → Malleus, Incus, Stapes) that will amplify sound, transmit to oval window (inner ear

3) Gets to the inner ear

• Cochlea: Spiral tube where sound is detected

SEQ Sensory Reception of the Ear

Pinna

Part of your ear that collects sound waves

Auditory Canal

Channels waves to tympanic membrane

Tympanic Membrane

A thin membrane that vibrates and transmits to middle ear (eardrum)

Middle Ear

Part that is your air filled cavity

Ossicles

Containing 3 small bones that amplify sound, transmit to oval window and to inner ear (your incus, malleus, and stapes)

Cochlea

Spiral tube where sound is detected and hari cells are contained (mechanoreceptors with cilia where they vibrate against the plasma membrane of hair cells)

1) Hair cells stimulated

2) Depolarization

3) Action Potential → Axons bundled into auditory nerve to transmit signals to brain

4) Brain will process that signal (signal perception)

How is sound converted to hearing? Can you sequence it?

1) Outer ear

• Pinna will collect your sound waves

• Auditory Canal: channels waves to tympanic membrane

• Tympanic Membrane (ear drum): Thin membrane that vibrates and transmits to middle ear

1st step of Sensory Reception of the Ear

2) Gets to the middle ear

• Ossicles: (your 3 small bones → Malleus, Incus, Stapes) that will amplify sound, transmit to oval window (inner ear

2nd step of sensory reception to the ear

3) Gets to the inner ear

• Cochlea: Spiral tube where sound is detected

3rd step of sensory reception of the ear

1) Hair cells stimulated

1st step of sound converted to hearing

2) Depolarization

2nd step of converting sound to hearing

3) Action Potential occurs → Axons bundled into auditory nerve to transmit signals to brain

3rd step of converting sound to hearing

4) Brain will process that signal (signal perception)

4th step of converting sound to hearing