Week 5 Flashcards
• Outline the major anatomical and functional divisions of the nervous system
Anatomical division
- Central nervous system-brain spinal chord
- Peripheral nervous system
○ Nerves
§ 12 pairs of crainial nerves and 31 pairs of spinal nerves
Functional divisions
- Voluntary conscious control
- Somatic nervour system
○ Speical sensense-vision, hearing, taste, smell, touch
○ Motor pathways
- Involuntary unconscious control
○ Autonomic nervous system
§ Innervation of involuntary structures to maintain homeostasis
§ Eg-cardiovascular and respiratory system
○ Enteric nerovus system
§ Involuntary nervous system of digestive tract=Controls digestion movement of contents
• Define the functional and structural features of a neuron.
- Neuron structure
○ Dendrites (tree)
§ Dendritic membrane under synapce (post synaptic membrane) contain many receptor proteins to Recieve neural stimuli
§ Excitatory or inhibitory in nature
○ Soma/cell body
§ Houses nucleus and organelles
§ Metabolic center which processes and interprets stimulus to decided whether it will be passe done
○ Axon
§ Conducts nerve impulse to axon terminals so message can be relayed to effector cell-membrane around axon is different to that of cell body
○ Axon Hillock
§ Site of AP intitation
○ Myelin Coat
§ Insulates cxon and increases speed of AP conduction
§ Different cell types provide this coating in CNS and PNS
○ Nodes of ranvier
§ Gaps between myelin coats enables AP to jump between and propagate signal quicker
○ Axon terminal=specialised endings that make contact with effector cells
§ AP triggers relase of neurotransmitters at synapse
• Outline the functional and structural classification of neurons.
Multipolar= 2 or more dendrites surrounding cell body and One main axon
Motor/efferent neuron-carry info from CNS to effector Interneurons-integrate info within CNS Unipolary/Psuedo unipolar= Only one axon from cell body 2 direction branches Sensory/afferent neurons= Carry signals from periphery to CNS Bipolar neurons=2 major processes= main dendrite and 1 main axon
• Discuss the structure and function of neuroglia within the central and peripheral nervous systems.
- Glia=glue-protect neurons and nerovus system by noursihing and supporting cells in surround environment
STRUCTURE • Outline the components and significance of the blood-brain barrier.
○ Epithelium lining that usually lines any BV in body
○ Simple layer of squamous epithelial cells
○ No gaps between cells only cpnnected by tight junctions
§ Ensures any molecule that corsses enters through the multiple layers of BBB
○ Pericytes ensure stringent regulation of substances
○ Basement membrane enables strucutal support
Astrocytes-largest neuroglia cells have exending projections of podocytes that encaspulate BV to insure strucutral support to BBB adding to strigency of monitoring membrane
• Discuss the properties of the neuron that are key for neuronal communication.
- Ion channels and Pumps
○ Facilitate entry and exit of ions (K+,Ca2+,Na+,Cl-)- Neurosynapses
○ At axon terminal enters extracellular space electrical message turns chemical○ Membrane potential looks at difference in charge electrical between intracelllular and extracellular spaces for electrical signalling and release of AP
- Neurosynapses
• Describe the concept of membrane potential and the components of the membrane that establish the resting membrane
potential.
○ Membrane potential looks at the difference in charge electrical between intracellular and extracellular spaces
○ -70 milivolts is membrane ptoential for neurons at rest
• Describe the concept of membrane potential and the components of the membrane that establish the resting membrane
potential.
Plasma membrane-lipid bilayer spearates internal and extrenal cell environment controls movement of substances and is a chemical insulator and also electrical insulator as many substances moving are charged
Ion channels and Pumps- Facilitate entry and exit of ions to respond to change in chemical or electrical potential via gated channels (voltage for electric, chemical/ligand for chemical) or leakage channels or mechanical channels to control rest state
• Describe the subtypes of ion channels and their activity (leakage, ligand, voltage and mechanically gated).
- Ion channels and Pumps ○ Facilitate entry and exit of ions § Key ions look at □ K+ □ Na+ □ Ca2+ □ Cl- ○ Types of ion channels § Gate channels □ Voltage gated ® Respond to change in charge or electrical potential □ Chemically or ligan gated ® Respond to change in chemical concentration or binding of a chemical □ Mechanically gates ® Respond to mechanical stimulus § Leakage channels Always open OR randomly alternate between open and closed
Define the sequence of events of an action potential (i.e., reaching threshold, depolarisation, repolarisation, hyperpolarisation
and return to resting membrane potential).
- Initiation
○ Stimulus reaches threshold at -55mv
○ At rest neuron recieves message amd membrane potential is moved to threshold- Depolarisation
○ Influx of positive ions in cell increase charge in intracellular space to +40mv - Repolarisation
○ Membrane potential goes down to -7omv exit of ions out of cell
○ Restore resting membrane potential - Hyper polarisation
○ Shooting past -70mv and then excess + ions added to regain -70mv - Resting potential
○ Voltage gated Na+ K+ channels closed
○ Na+/K+ pump maintains -70mv
○ High concentrentation of Na+ outside
○ High K+ on inside - Depolarisation AP
○ Stimulus initated Membrane potnetial change to threshold value of -55mv-action potential will occur beyond this
○ -55mv enables voltage gated sodium channels open
○ Na+ ions flow into cell from outside carrying + charge with it
○ Inside cell more +
○ Continues until membrane ptoential is +40mvAP
○ Explosive and fast - Repolarisation
○ Return to rest state
○ Volage gated Na+ channels close
○ Potassium K+ channels open at +40mv
○ K+ exit cell and iside becomes more negatively charged
○ Excess K+ pumped out
○ Some K+ re enter
○ Straight past deisred -70mv
Refractory period-channels closed but sodium potassium pump re calibrating and establishing rest state
- Depolarisation
• Describe the structure and function of myelin and its role in saltatory conduction.
○ Myelinated-protein lipid complex that coats axon of neurons and acts as protector and insulator- neurons
Insulation by myelin allows AP moves through axon protected through the myelinated region to node of Ranvier which is loaded with voltage-gated ion channels to allow for eflux and influx of ions allowing fast signal
• Describe how EMGs can be used to examine the activation of muscle by the nervous system via surface and intramuscular
techniques.
○ Electromyography
§ Measures electrical activity in resting and contracting muscles
§ Forceful contraction produces increased electrical activity
§ Helps evaluate if muscle weakness or paralysis is from malfunctionn of muscle or nerves supplying muscle
○ Action potential in muscle is measured
○ Motor neurons communicate with muscle
○ Transform into AP propagated from neuromusclular junction to ends of muscle fibres
○ Involves Na+ and K+ channels
○ Activated contractile proteins to contract
○ Electrodes used in EMGS
○ Surface emg- Electrodes on skin direclty over muscle ○ Intramuscular emgs-Thin wires inserted into muscle
• Describe the structure and function of a synapse.
Neuronal communication occurs here
Space between neurons where signals may be released via ions or neurotrasnmitters
• Define the sequence of events of synaptic transmission.
- Synapse propagation of one neuron to another
○ Action potential reaches axon terminal at pre synaptic neuron
○ Voltage gated Ca2+ channels open result in influx of Ca++ into axon terminals
○ Neurotransmitters in carrier vesicles exit axon terminals via exocytosis
○ Neurotransmitters diffuse across the synaptic cleft
○ Neurotransmitters bind to specific receptors on post synaptic neuron
○ Post synaptic potential stimulated
○ Aps in post synaptic neuron flow through
• Outline the role of neurotransmitters.
Neurotransmitters are messenger molecules that transmit messages across different neurons made in neurons they are packaged travelled down to the axon terminal of presynaptic cell
• Compare and contrast ionotropic and metabotropic neurotransmitters.
- Ionotrpic vs Metabotropic
§ Ionotropic neurotransmission-ligand gated receptors
□ Open close response in neurotransmitter binding
□ Super quick and efficient
□ Glutamate receptors NMDAr
§ Metabotropic-g protein coupled receptors
§
□ Take a bit longer but reliable
□ Sense ligand binding and activates secondary messengers
® Activate other effector proteins-2a-enzymes, 2b-ion channels
® Causes signalling cascades within cell
Impacts metabolic pathways membrane permability
