Nervous system Flashcards
Role of neurons
Process sensory info + carry out motor response
-> X divide therefore cannot be replaced
Role of neuroglia
Insulate, support + nourish neurons
Structure of multipolar neuron
- many dendrites
- 1 axon
- cell body b/t dendrites + axon
Structure of unipolar neuron
- dendrites merge onto axon
- cell body b/t dendrite + axon
eg. sensory neuron
Structure of bipolar neuron
- 1 dendrite, 1 axon
- cell body b/t dendrite + axon
- rare
Describe astrocytes
- most abundant neuroglia in CNS
- provide structural support for neurons
- regulate interstitial environment b/t neurons
- maintain blood brain barrier
Describe ependymal cells
produce, secrete + monitor cerebrospinal fluid around spinal cord
Describe oligodendrocytes
wrap around axons providing layers of membrane that insulate axons eg. myelin sheaths (CNS)
Describe microglia
-least abundant
migrate through tissue / clean up cellular debris, waste products + pathogens
Describe satellite cells
regulates environment around PNS neurons
Describe schwann cells
Wrap around axons providing layers of membrane that insulate axon
Define neurotransmission
Transmission of info across a synapse
Define membrane potential
The separation of positive and negative charges across a membrane creating a potential difference
-70mV at rest
State how active/gated channels function
- open + close in response to specific stimuli
at rest, most closed
Describe chemically gated ion channels
Chemical eg. neurotransmitter binds to gate
-> gate opens + ions diffuse through
Describe voltage gated ion channels
Membrane potential changes -> gate opens to enable ion flow
Describe mechanically gated ion channels
Structure of gate changes due to pressure applied -> gate opens + enables ions to enter via diffusion
Describe graded potential
Whereby a small, local + temporary change in membrane potential occurs
-> caused by chem/mechanical stimulus opening active channel in dendrite
Describe the function of an axon potential
Enables the travelling of info from cell body to axon terminals
-> starts at axon hillock + reaches axon terminal
Describe the phases of an action potential
- Resting membrane potential = -70mV, voltage gated Na+ + K+ channels closed
- Depolarisation to threshold = summation of graded potentials reaches threshold (-60mV to -55mV) / voltage gated Na+ channels open
- Activation of sodium channels + rapid depolarisation = Na+ ions rush into cell causing inside of cell to become positive / 30mV
- Inactivation of Na channels / activation of K channels = Na channels close + K channels open to enable K+ to move out of the cell
- Closing of K+ channels = k channels close as resting membrane potential restored / close slowly resulting in brief hyperpolarisation at -90mV
Differentiate b/t myelinated + unmyelinated axons
Unmyelinated have continuous propagation whilst myelinated have faster propagation of action potentials as they only move through node
Describe the process of neurotransmission
- action potential arrives at axon terminal
- voltage gated Ca+ channels open + Ca2+ enters axon terminal
- Ca2+ entry causes synaptic vesicles to release their contents via exocytosis
- neurotransmitters diffuse across the synaptic cleft + bind to specific receptors on the post synaptic neuron
