Download Free Medical Neural Communication-Basics PowerPoint Presentation

Neural Communication-Basics PowerPoint Presentation

DOWNLOAD MEDICAL POWERPOINT PRESENTATION

About This Presentation

Description : Check out this medical presentation on Neurology, which is titled "Neural Communication: Basics", to know about the Basics of Neural Communication.

Tags : Neurology, Neural Communication, Basics

Published on : Aug 23, 2021 | Views : 1284 | Downloads : 0

Shareable Url :

Embed Code :

Comment

Transcript

Slide 1-

ppt slide no 1 content not found
Slide 2-

Overview Course introduction Neural Processing: Basic Issues Neural Communication: Basics Vision, Motor Control: Models
Slide 3-

Neurons cell body dendrites (input structure) receive inputs from other neurons perform spatio-temporal integration of inputs relay them to the cell body axon (output structure) a fiber that carries messages (spikes) from the cell to dendrites of other neurons
Slide 4-

postsynaptic neuron science-education.nih.gov
Slide 5-

Synapse site of communication between two cells formed when an axon of a presynaptic cell “connects” with the dendrites of a postsynaptic cell
Slide 6-

Synapse axon of presynaptic neuron dendrite of postsynaptic neuron bipolar.about.com/library
Slide 7-

Synapse a synapse can be excitatory or inhibitory arrival of activity at an excitatory synapse depolarizes the local membrane potential of the postsynaptic cell and makes the cell more prone to firing arrival of activity at an inhibitory synapse hyperpolarizes the local membrane potential of the postsynaptic cell and makes it less prone to firing the greater the synaptic strength, the greater the depolarization or hyperpolarization
Slide 8-

ppt slide no 8 content not found
Slide 9-

Neural Communication: 1 Communication within and between cells
Slide 10-

Transmission of information Information must be transmitted within each neuron and between neurons
Slide 11-

The Membrane The membrane surrounds the neuron. It is composed of lipid and protein.
Slide 12-

The Resting Potential There is an electrical charge across the membrane. This is the membrane potential. The resting potential (when the cell is not firing) is a 70mV difference between the inside and the outside. inside outside Resting potential of neuron = -70mV + - + - + - + - + -
Slide 13-

Artist’s rendition of a typical cell membrane
Slide 14-

Ions and the Resting Potential Ions are electrically-charged molecules e.g. sodium (Na+), potassium (K+), chloride (Cl-). The resting potential exists because ions are concentrated on different sides of the membrane. Na+ and Cl- outside the cell. K+ and organic anions inside the cell. inside outside Na+ Cl- Na+ K+ Cl- K+ Organic anions (-) Na+ Na+ Organic anions (-) Organic anions (-)
Slide 15-

Ions and the Resting Potential Ions are electrically-charged molecules e.g. sodium (Na+), potassium (K+), chloride (Cl-). The resting potential exists because ions are concentrated on different sides of the membrane. Na+ and Cl- outside the cell. K+ and organic anions inside the cell. inside outside Na+ Cl- Na+ K+ Cl- K+ Organic anions (-) Na+ Na+ Organic anions (-) Organic anions (-)
Slide 16-

Maintaining the Resting Potential Na+ ions are actively transported (this uses energy) to maintain the resting potential. The sodium-potassium pump (a membrane protein) exchanges three Na+ ions for two K+ ions. inside outside Na+ Na+ K+ K+ Na+
Slide 17-

ppt slide no 17 content not found
Slide 18-

Excitatory postsynaptic potentials (EPSPs) Opening of ion channels which leads to depolarization makes an action potential more likely, hence “excitatory PSPs”: EPSPs. Inside of post-synaptic cell becomes less negative. Na+ channels (NB remember the action potential) Ca2+ . (Also activates structural intracellular changes -> learning.) inside outside Na+ Ca2+ + -
Slide 19-

Inhibitory postsynaptic potentials (IPSPs) Opening of ion channels which leads to hyperpolarization makes an action potential less likely, hence “inhibitory PSPs”: IPSPs. Inside of post-synaptic cell becomes more negative. K+ (NB remember termination of the action potential) Cl- (if already depolarized) K+ Cl- + - inside outside
Slide 20-

Integration of information PSPs are small. An individual EPSP will not produce enough depolarization to trigger an action potential. IPSPs will counteract the effect of EPSPs at the same neuron. Summation means the effect of many coincident IPSPs and EPSPs at one neuron. If there is sufficient depolarization at the axon hillock, an action potential will be triggered. axon hillock
Slide 21-

Neuronal firing: the action potential The action potential is a rapid depolarization of the membrane. It starts at the axon hillock and passes quickly along the axon. The membrane is quickly repolarized to allow subsequent firing.
Slide 22-

Before Depolarization
Slide 23-

Action potentials: Rapid depolarization When partial depolarization reaches the activation threshold, voltage-gated sodium ion channels open. Sodium ions rush in. The membrane potential changes from -70mV to +40mV.
Slide 24-

Depolarization
Slide 25-

Depolarization
Slide 26-

Action potentials: Repolarization Sodium ion channels close and become refractory. Depolarization triggers opening of voltage-gated potassium ion channels. K+ ions rush out of the cell, repolarizing and then hyperpolarizing the membrane.
Slide 27-

Repolarization
Slide 28-

Action potentials: Resuming the Resting Potential Potassium channels close. Repolarization resets sodium ion channels. Ions diffuse away from the area. Sodium-potassium transporter maintains polarization. The membrane is now ready to “fire” again.
Slide 29-

The Action Potential The action potential is “all-or-none”. It is always the same size. Either it is not triggered at all - e.g. too little depolarization, or the membrane is “refractory”; Or it is triggered completely.
Slide 30-

Course of the Action Potential The action potential begins with a partial depolarization (e.g. from firing of another neuron ) [A]. When the excitation threshold is reached there is a sudden large depolarization [B]. This is followed rapidly by repolarization [C] and a brief hyperpolarization [D]. There is a refractory period immediately after the action potential where no depolarization can occur [E] [E]
Slide 31-

Action Potential Local Currents depolarize adjacent channels causing depolarization and opening of adjacent Na channels Question: Why doesn’t the action potential travel backward?
Slide 32-

ppt slide no 32 content not found
Slide 33-

Conduction of the action potential. Passive conduction will ensure that adjacent membrane depolarizes, so the action potential “travels” down the axon. But transmission by continuous action potentials is relatively slow and energy-consuming (Na+/K+ pump). A faster, more efficient mechanism has evolved: saltatory conduction. Myelination provides saltatory conduction.
Slide 34-

Myelination Most mammalian axons are myelinated. The myelin sheath is provided by oligodendrocytes and Schwann cells. Myelin is insulating, preventing passage of ions over the membrane.
Slide 35-

Saltatory Conduction Myelinated regions of axon are electrically insulated. Electrical charge moves along the axon rather than across the membrane. Action potentials occur only at unmyelinated regions: nodes of Ranvier. Node of Ranvier Myelin sheath
Slide 36-

Synaptic transmission Information is transmitted from the presynaptic neuron to the postsynaptic cell. Chemical neurotransmitters cross the synapse, from the terminal to the dendrite or soma. The synapse is very narrow, so transmission is fast.
Slide 37-

terminal dendritic spine synaptic cleft presynaptic membrane postsynaptic membrane extracellular fluid Structure of the synapse An action potential causes neurotransmitter release from the presynaptic membrane. Neurotransmitters diffuse across the synaptic cleft. They bind to receptors within the postsynaptic membrane, altering the membrane potential.
Slide 38-

Neurotransmitter release Synaptic vesicles, containing neurotransmitter, congregate at the presynaptic membrane. The action potential causes voltage-gated calcium (Ca2+) channels to open; Ca2+ ions flood in. vesicles Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ Ca2+
Slide 39-

Neurotransmitter release Ca2+ causes vesicle membrane to fuse with presynaptic membrane. Vesicle contents empty into cleft: exocytosis. Neurotransmitter diffuses across synaptic cleft. Ca2+
Slide 40-

ppt slide no 40 content not found
Slide 41-

Ionotropic receptors (ligand gated) Synaptic activity at ionotropic receptors is fast and brief (milliseconds). Acetylcholine (Ach) works in this way at nicotinic receptors. Neurotransmitter binding changes the receptor’s shape to open an ion channel directly. ACh ACh
Slide 42-

ppt slide no 42 content not found
Slide 43-

Ionotropic Receptors
Slide 44-

Metabotropic Receptors (G-Protein)
Slide 45-

ppt slide no 45 content not found
Slide 46-

Postsynaptic potentials Depending on the type of ion channel which opens, the postsynaptic cell membrane becomes either depolarized or hyperpolarized. Ions will tend to follow the concentration gradient from high to low concentration, and the electrostatic gradient towards the opposite charge.
Slide 47-

Postsynaptic Ion motion
Slide 48-

Requirements at the synapse For the synapse to work properly, six basic events need to happen: Production of the Neurotransmitters Synaptic vesicles (SV) Storage of Neurotransmitters SV Release of Neurotransmitters Binding of Neurotransmitters Lock and key Generation of a New Action Potential Removal of Neurotransmitters from the Synapse reuptake
Slide 49-

Three Nobel Prize Winners on Synaptic Transmission Arvid Carlsson discovered dopamine is a neurotransmitter. Carlsson also found lack of dopamine in the brain of Parkinson patients. Paul Greengard studied in detail how neurotransmitters carry out their work in the neurons. Dopamine activated a certain protein (DARPP-32), which could change the function of many other proteins. Eric Kandel proved that learning and memory processes involve a change of form and function of the synapse, increasing its efficiency. This research was on a certain kind of snail, the Sea Slug (Aplysia). With its relatively low number of 20,000 neurons, this snail is suitable for neuron research.
Slide 50-

Neuronal firing: the action potential The action potential is a rapid depolarization of the membrane. It starts at the axon hillock and passes quickly along the axon. The membrane is quickly repolarized to allow subsequent firing.
Slide 51-

Overview Course introduction Neural Processing: Basic Issues Neural Communication: Basics Vision, Motor Control: Models
Slide 52-

ppt slide no 52 content not found
Slide 53-

Motor Control: Basics
Slide 54-

Motor Control Basics Reflex Circuits Usually Brain-stem, spinal cord based Interneurons control reflex behavior Central Pattern Generators Cortical Control
Slide 55-

ppt slide no 55 content not found
Slide 56-

Hierarchical Organization of Motor System Primary Motor Cortex and Premotor Areas
Slide 57-

Primary motor cortex (M1) Foot Hip Trunk Arm Hand Face Tongue Larynx
Slide 58-

postsynaptic neuron science-education.nih.gov
Slide 59-

Flexor- Crossed Extensor Reflex (Sheridan 1900) Painful Stimulus Reflex Circuits With Inter-neurons
Slide 60-

ppt slide no 60 content not found
Slide 61-

ppt slide no 61 content not found
Slide 62-

Gaits of the cat: an informal computational model
Slide 63-

Vision and Action
Slide 64-

Cortical Motor System Pre-motor cortex Movement planning/sequencing Many projections to M1 But also many projections directly into pyramidal tract Damage => more complex motor coordination deficits Stimulation => more complex mov’t Two distinct somatotopically organized subregions SMA (dorso-medial) May be more involved in internally generated movement Lateral pre-motor May be more involved in externally guided movement
Slide 65-

Somatotopy of Action Observation Foot Action Hand Action Mouth Action Buccino et al. Eur J Neurosci 2001
Slide 66-

Rizzolatti et al. 1998 A New Picture
Slide 67-

Somato-Centered Bimodal RFs in area F4 (Fogassi et al. 1996)
Slide 68-

The fronto-parietal networks Rizzolatti et al. 1998
Slide 69-

F5c-PF Rizzolatti et al. 1998
Slide 70-

The F5c-PF circuit Links premotor area F5c and parietal area PF (or 7b). Contains mirror neurons. Mirror neurons discharge when: Subject (a monkey) performs various types of goal-related hand actions and when: Subject observes another individual performing similar kinds of actions
Slide 71-

ppt slide no 71 content not found
Slide 72-

Murata et al. J Neurophysiol. 78: 2226-2230, 1997 F5 Canonical Neurons
Slide 73-

Vision
Slide 74-

Overview of the Visual System
Slide 75-

ppt slide no 75 content not found
Slide 76-

ppt slide no 76 content not found
Slide 77-

ppt slide no 77 content not found
Slide 78-

ppt slide no 78 content not found
Slide 79-

Physiology of Color Vision © Stephen E. Palmer, 2002 Cones cone-shaped less sensitive operate in high light color vision Rods rod-shaped highly sensitive operate at night gray-scale vision Two types of light-sensitive receptors
Slide 80-

The Microscopic View
Slide 81-

ppt slide no 81 content not found
Slide 82-

ppt slide no 82 content not found
Slide 83-

How They Fire No stimuli: both fire at base rate Stimuli in center: ON-center-OFF-surround fires rapidly OFF-center-ON-surround doesn’t fire Stimuli in surround: OFF-center-ON-surround fires rapidly ON-center-OFF-surround doesn’t fire Stimuli in both regions: both fire slowly
Slide 84-

ppt slide no 84 content not found
Slide 85-

ppt slide no 85 content not found
Slide 86-

ppt slide no 86 content not found
Slide 87-

ppt slide no 87 content not found
Slide 88-

ppt slide no 88 content not found
Slide 89-

ppt slide no 89 content not found
Slide 90-

ppt slide no 90 content not found
Slide 91-

ppt slide no 91 content not found
Slide 92-

Visual Processing
Slide 93-

http://www.iit.edu/~npr/DrJennifer/visual/retina.html Rods and Cones in the Retina
Slide 94-

What Rods and Cones Detect Notice how they aren’t distributed evenly, and the rod is more sensitive to shorter wavelengths
Slide 95-

Center / Surround Strong activation in center, inhibition on surround The effect you get using these center / surround cells is enhanced edges top: the stimuli itself middle: brightness of the stimuli bottom: response of the retina You’ll see this idea get used in Regier’s model http://www-psych.stanford.edu/~lera/psych115s/notes/lecture3/figures1.html
Slide 96-

How They Fire No stimuli: both fire at base rate Stimuli in center: ON-center-OFF-surround fires rapidly OFF-center-ON-surround doesn’t fire Stimuli in surround: OFF-center-ON-surround fires rapidly ON-center-OFF-surround doesn’t fire Stimuli in both regions: both fire slowly