Module 2 - Nervous Systems Flashcards Preview

BIOL1040 > Module 2 - Nervous Systems > Flashcards

Flashcards in Module 2 - Nervous Systems Deck (28):

Sensory neuron vs interneuron vs motor neuron structure

Sensory neuron - long axon
Interneuron - lots of dendrites to collect information and many synaptic terminals (branches off axon)
Motor neuron - many dendrites and 1 long axon from CNS to effector


What are Glia? What are the types and their roles?

- supporting cells that are vital for structural integrity and normal function of neurons

Astrocytes - in the CNS, form the blood-brain barrier and regulate extracellular concentration of ions and neurotransmitters

Oligodendrocytes (CNS) and Schwann cells (PNS) - form myelin sheaths around axons that act as insulators


What is the abundance of Glia?

10-50 times more than neurons in the mammalian brain


Resting membrane potential Na+ and K+ concentration

ECF - 5mM K+ and 150mM Na+
Cytoplasm - 140mM K+ and 15mM Na+


Rate of Na+/K+-ATPase pumping

3 Na+ ions out and 2 K+ ions in


What causes the resting membrane potential?

Many open K+ channels and few Na+ channels plus charged proteins inside the cell


Hyperpolarisation vs depolarisation

Hyper - inside of membrane becomes more negative as a result of K+ channels opening and K+ flowing out of cell

De - inside of membrane becomes more positive as a result of Na+ channels opening and Na+ ions flowing into the cell


Graded vs action potentials

- can be hyper- or depolarisation
- vary in magnitude with the strength of stimulus
- local and die out

- depolarisation only
- reach a certain threshold and is an 'all or nothing' response
- travel along axons


Absolute refractory period (ARP) vs relative refractory period (RPR)

ARP - no action potential can be generated on top of the current one as Na+ channels are open and then inactive

RPR - action potential can only be generated to add to the current one if a large stimulus is applied, as some Na+ channels are closed again


Saltatory vs. smooth conduction

Saltatory: conduction of AP along axon - AP only needs to be generated at Nodes of Ranvier between Schwann cells along the axons => faster conduction

Smooth: AP generated all the way along due to no myelination


Na+ channels vs K+ channels

Na+ channels have 3 stages - Closed, open and inactive, and open very fast
K+ channels have 2 stages - closed and open, and are slower to open

Both open by depolarisation signal


What effects the speed of conduction?

- Axon diameter: larger diameter = less resistance = faster conduction
- temperature: increase temp = increase conduction speed
- degree of myelination: increase myelination = decreased loss of electrical signal = increased conduction speed (more effect than axon diameter)


Electrical vs chemical synapses

- rare type
- at gap junctions
- direct electrical currents between cells

- common type
- involve release of a neurotransmitter
- neurotransmitter released by presynaptic neuron


Excitatory vs inhibitory postsynaptic potential

EPSP - depolarisation in postsynaptic membrane, could lead to another action potential is depolarisation reaches threshold

IPSP - hyperpolarisation at postsynaptic membrane


Temporal vs spatial summation

temporal - several EPSP's from the same synapse just after each other

spatial - two or more EPSP's from different synpases


Postsynaptic potential vs action potential

- excitatory (EPSP) or inhibitory (IPSP)
- graded
- local
- at the cell body or dendrites

- depolarisation
- all or nothing
- can be the result of the addition of excitatory postsynaptic potentials
- generated at the axon hillock
- travels along the axon


Types of chemical synaptic transmission and related receptor types

- neurotransmitter opens ion channels on the postsynaptic membrane
- action via ligand-gated ion channels
Receptors: ion channel receptors

- neurotransmitter binds to a receptor on the postsynaptic membrane
- activates a signal transduction pathway
- involves a second messenger
Receptors: GPCR's


4 ways to remove neurotransmitters from synaptic cleft

- Broken up by enzymes such as acetylcholinesterase (super fast, enzyme sits in cleft ready to take action)
- Diffusion (too slow for the necessary control)
- recycled by selective uptake of transporters such as NET and SERT back into the presynaptic neuron where they return to vesicles (different transport proteins for each neurotransmitter)
- Taken up by astrocytes which mop up the left overs


What animals don't have a nervous system?




- brain
- spinal cord

- cranial nerves (12 pairs in mammals)
- spinal nerves (31 pairs in mammals)


Somatic vs autonomic nervous system

Both part of PNS

Somatic - voluntary control e.g. motor neurons

- mostly involuntary control e.g. heart rate
- 3 divisions: sympathetic, parasympathetic and enteric


Sympathetic vs parasympathetic vs enteric divisions of autonomic nervous system from PNS, and response/s of activation

Enteric - nerves to gut, very complex

- fight or flight
- bronchi dilate
- heart rate increases
- increase converstion of glycogen to glucose
- adrenaline secretion
- digestion inhibitation
- nerves arise from thoracic or lumber (middle) regions of spine
- short pre-ganglia fibre and long post-ganglia fibre

- rest and digest
- calming
- often has opposite response to the sympathetic division
- nerves arise from cervical or sacral (top and bottom) regions of spine
- long pre-ganglia fibre and short post-ganglia fibre


Roles of cerebrospinal fluid

- protects the CNS
- clear fluid in subarachnoid space (between the skull and cortex)
- 4 ventricles and central canal
- supply nutrients and hormones
- remove waste
- blocks flow in hydrocephalus


Grey vs white matter inc. location in brain and spinal cord

Grey matter:
- dendrites, cell bodies and unmyelinated axons
- outside of brain
- inside of spinal cord

White matter:
- myelinated axons
- inside of brain
- outside of spinal cord


Where are new neurons derived from?

adult stem cells


What determines how long the refractory period goes for?

How long it takes for the voltage-gated sodium channels to reactivate at the end of an action potential


4 ways that neurotransmitters affect postsynaptic cells

- causing molecular changes in the cells
- affecting ion-channel proteins
- initiating signal transduction pathways in the cells
- altering the permeability of the cells


How is the activity of acetylcoline in a synapse terminated?

It is degraded by a hydrolytic enzyme on the postsynaptic membrane