Module 2: Nervous System Flashcards
Draw a labelled diagram showing the stages of an Action Potential:
See booklet for correct diagram
Outline 5 points with regards to Membrane Potential:
- The resting membrane potential is negative because Na+/K- ATP-ase pumps 3Na+ out and 2K in
- The membrane at rest has many open K+ channels and few Na+ or Cl-
- This has nothing to do with voltage gated ion channels! Those are for action potentials
- There is a build-up of negative charge in the neutron
- Equilibrium is approx. -70mV in the human neuron. All cells have a membrane potential
Describe the 6 steps of the structure-function of membrane channels: Sodium-Potassium pumps:
- The interior of the pump is open to the inside of the axon; 3 sodium ions enter the pump and attach to their binding sites
- ATP transfers a phosphate group from itself to the pump, causing the pump to change shape and the interior is then closed
- The interior of the pump opens to the outside of the axon and three sodium ions are released
- Two potassium ions from outside can then enter and attach to their binding sites
- Binding of potassium causes release of the phosphate group, causing the pump to change shape so it is only open to the inside of the axon
- Sodium ions can then enter and bind to the pump
Describe the 3 steps of the structure-function of membrane channels: Voltage-gated sodium channels:
- Channel is closed. There is a negative charge inside the axon and a net positive charge outside. The channel is voltage gated
- If the net charge is negative on the outside, the protein moves so that it is open temporarily
- A ‘ball’ fits into the pore within milliseconds of the pore opening, which is removed when the channel returns to its original closed state
Give an example of a use for the Voltage-gated sodium channel:
Local anaesthetics
- act on the ‘ball’ of the ‘ball and chain’ mechanism, causing the channel to be inactivated longer
List and describe the 3 factors affecting conduction:
- Myelination: Insulation of myelin sheath allows for saltatory conduction (‘skipping’ along the nodes of Ranvier) for faster conduction
- Axon diameter: Less resistance of the action potential allows it to propagate faster, not as a effective as myelination
- Temperature: faster activity
List the 3 steps of information processing in nervous systems:
- Sensory output
- Integration
- Motor output
List everything in the structure of a neuron (10)
- Presynaptic cell
- Synapse
- Postsynaptic cell
- Nucleus
- Cell body
- Dendrites
- Axon hillock
- Axon: myelin sheath, Schwann cells, Nodes of Ranvier
- Synaptic terminals
List and describe the 3 types of Neurons:
- Sensory neurons: have the cell body in the middle of the axon
- Interneurons: have very branched dendrites with a lot of exposure, but not as branched axon terminals
- Motor neurons: look more ‘classic’, with branched dendrites but not as branched axon terminals, and very long axon
Describe the main components of nerves:
- a nerve consists of many neurons, connective tissues and blood vessels
- glial cells are vital for structural integrity and normal functioning for the neurons
- there are 10-50 times more glia than neurons in the mammalian brain
List and describe the types of glial cells: Those that form myelin sheaths (lipid sheaths) that insulate the axon:
- Oligodendrocytes: of the CNS
- Schwann Cells: of the PNS
Describe the features of Astrocytes (a glial cell) of the CNS:
- used for structural support
- regulates extracellular concentration of ions and neurotransmitters
- formation of the blood brain barrier
Describe the formation of the Blood-brain barrier
- astrocyte foot processes
- basement membrane
- tight junctions (no toxins allowed through)
- endothelial cell
- only diffusion through astrocytes and endothelial cells are allowed through the blood vessels
Describe the structure of synapses and synaptic transmission
- synapses are very close to each other and form tight junctions
- this close proximity prevents fluid moving across a layer of cells
- gap junctions are where neurotransmission occurs
List and describe the 2 types of Postsynaptic potential types:
- EPSP: excitatory postsynaptic potential: occurs if depolarisation at postsynaptic membrane
- temporal summation: several EPSP’s can reach the threshold at the axon hillock, causing an action potential
- spatial summation: two or more EPSP’s from different synapses: the closer synapse will produce the fastest response - IPSP: inhibitory postsynaptic potential: if hyper polarisation at postsynaptic membrane
List the 4 types of Summation
- Sub-threshold (no summation)
- E1 and E1 one after another, does not reach threshold potential - Temporal summation
- E1 and E1 close enough after another, reaches threshold potential - Spatial summation of EPSPs
- E1 and E2 together reaches threshold potential - Spatial summation of EPSP and IPSP
- E1 depolarises, I hyperpolarises, E1 and I together small depolarisation, does not reach threshold potential
List/ draw the process of Synaptic Neurotransmission (9 steps)
- Nerve impulse is propagated along the pre-synaptic neuron until it reaches the pre-synaptic membrane
- Depolarisation causes Ca ions to diffuse through channels in the membrane
- This causes vesicles containing neurotransmitter to fuse with the membrane
- Neurotransmitter is realised into the synaptic cleft via exocytosis
- Neurotransmitters diffuse and bind to receptors on the post-synaptic membrane
- Binding of neurotransmitter to receptor open Na ion channels
- Na ions diffuses down the concentration gradient into the post-synaptic membrane, causing it to reach threshold potential, -50mV
- An action potential is triggered in the post-synaptic membrane and propagated along
- Neurotransmitter is broken down
List and give the action of the 4 types of Post-synaptic potentials
- EPSP or IPSP: only depolarisation
- Graded: all or nothing
- Local: EPSPs add up to cause action potential
- At cell body or dendrites: Generated at axon hillock, travels along axon
Describe Direct synaptic transmission
- neurotransmitter opens ion channels on post-synaptic membrane
- leads to a graded post-synaptic potential
- ligand-grated ion channels: ion channel linked receptors (fastest)
Describe Indirect synaptic transmission
- neurotransmitter binds to post-synaptic membrane receptor
- activates signal transduction pathway involving a second messenger: G-protein coupled receptors (slower)
- can result in EPSPs or IPSPs depending on neurotransmitter and receptor type
List the 4 types of Amino Acid Neurotransmitters
- GABA (gamma aminobutyric acid)
- Glycine
- Glutamate
- Aspartate
List the 4 types of Amine Neurotransmitters
- Acetylcholine
- Noradrenaline
- Dopamine
- Serotonin/ 5HT
List the removal of neurotransmitters from the synaptic cleft in order of likelihood
- Recycled by selective uptake by transporters (e.g. NET, SERT)
- Taken up by astrocytes
- Broken down by enzymes (e.g. acetylcholinesterase)
- Diffusion: least likely due to small gap junctions
List and give examples of the Organisation of a circuit for primitive organisms: (3)
- Cnidarians (e.g. hydra)- nerve net
- Echinoderms (sea stars)- radial nerves from nerve rings
- Flatworms (planarians)- eyespot, brain, nerve cords with traverse nerves
Give examples (2) of more complex invertebrate nervous system:
- segmentally arranged clusters of neurons into a ganglia- PNS, connected to a central nervous system
1. Annelids (leeches)- brain, ventral nerve cords, segmental ganglion
2. Arthropods (insects)- brain, ventral nerve cords, segmental ganglia
Give examples (2) of diverse nervous systems based on lifestyle (e.g. molluscs)
- mollusc organisation depends on lifestyle
1. Mollusc (chitin)- ganglia, anterior nerve ring, longitudinal nerve cords
2. Mollusc (squid)- brain, ganglia - -> the giant axon of the squid is used as an experimental model in physiology
Explain the most complex vertebrate nervous systems
- Consists of central nervous system, peripheral nervous systems, regional specialisation
1. CNA- brain and spinal cord
2. PNS- spinal nerves branching outwards, cranial nerves containing sensory and motor neurons
List the 7 stages of the Reflex Arc:
- Skin/muscle
- Sensory neurons
- Dorsal root ganglion on sensory neuron
- Interneuron at spinal cord
- Motor neuron
- Ventral root on motor neuron
- Muscle
List the divisions of the PNS
PNS –> Somatic nervous system (voluntary action) or Automatic nervous system —> Sympathetic division (fight or flight) or Parasympathetic division (rest and digest) or Enteric division (gastrointestinal functions)
List 4 components of the Cerebrospinal fluid
- subarachnoid space
- 4 ventricles and central canal
- supply of nutrients and hormones, removes waste
- in hydrocephalus, the flow is blocked (skull swells)
List the 4 different components of the Brain
- Grey matter
- White matter
- Ventricles
- Spinal cord
List 3 components of Grey matter:
- dendrites
- unmyelinated axons
- cell bodies
List 1 component of White matter:
- myelinated axons in tracts
List 1 component of ventricles:
- network of cavities that transports cerebrospinal fluid
List 3 components of Spinal cord:
- grey matter
- white matter
- butterfly appearance
What are the 7 regions of the brain:
- Frontal lobe
- Parietal lobe
- Occipital lobe
- Diencephalon
- Brainstem
- Cerebellum
- Temporal lobe
Breakdown/describe the Cerebrum (forebrain) components (4 parts)
- Frontal lobe:
- prefrontal cortex: decision making and planning
- motor cortex: control of skeletal muscle
- Broca’s area: speech formation - Temporal lobe:
- auditory cortex
- Wernicke’s area: comprehension of language - Parietal lobe:
- somatosensory cortex: touch
- sensory association cortex: integration - Occipital lobe:
- visual association cortex: object recognition
- visual cortex: processing and pattern recognition
Breakdown/describe the Midbrain components (1 part)
- Brain stem:
- evolutionarily old
- basic functions
- homeostasis, movement
- transfers information
- sections: pons, midbrain, reticular formation (selectivity filter determines arousal and sleep), medulla oblongata
Breakdown /describe the Hindbrain components (1 part)
- some of brain stem
1. Cerebellum - coordination
- motor function
- cognitive and perceptual functions
Breakdown/describe the Diencephalon (forebrain) components (3 parts)
- Epithalamus
- connects limbic system (emotions) to rest of brain
- pineal gland secretes melatonin (sleep) - Thalamus
- input from sensory neurons
- output via motor neurons - Hypothalamus
- homeostatic regulation via hormones
- circadian rhythms
- survival
