Monday April 14, 2014. N ervous system and biological electricity I V 1 . Exam 2 results

1. Monday April 14, 2014. Nervous system and biological electricity IV 1. Exam 2 results 2. Lab this week 3. Review of the synapse 4. The connectome 5. Vertebrate nervous system 6. Mapping the brain

2. This week in Lab

3. Lab philosophy and Scientific literacy An example of why this is important

4. Lab philosophy and Scientific literacy • Lab is designed to illustrate science as: • A creative process • Challenging • An interactive and social activity

5. Dropping grades in lab

6. ACTION POTENTIAL TRIGGERS RELEASE OF NEUROTRANSMITTER Na+ and K+ channels 1. Action potential arrives; triggers entry of Ca2+. Action potentials 2. In response to Ca2+, synaptic vesicles fuse with presynaptic membrane, then release neurotransmitter. Presynaptic membrane (axon) 3. Ion channels open when neurotransmitter binds; ion flows cause change in postsynaptic cell potential. Postsynaptic membrane (dendrite or cell body) 4. Ion channels will close as neurotransmitter is broken down or taken back up by presynaptic cell (not shown).

7. Excitatory vs. Inhibitory Synapses • Excitatory synapses cause the post-synaptic cell to become less negative triggering an excitatory post-synaptic potential (EPSP) • Increases the likelihood of firing an action potential • Inhibitory synapses cause the post-synaptic cell potential to become negative triggering an inhibitory post-synaptic potential • Decreases the likelihood of firing an action potential

8. Postsynaptic Potentials Can Depolarize or Hyperpolarize the Postsynaptic Membrane Postsynaptic potentials can depolarize or hyperpolarize the postsynaptic membrane. Depolarization, Na+ inflow Hyperpolarization, K+ outflow or Cl– inflow Depolarization and hyperpolarization stimuli applied Excitatory postsynaptic potential (EPSP) Inhibitory postsynaptic potential (IPSP) EPSP  IPSP Resting potential

9. Neurons Integrate Information from Many Synapses Most neurons receive information from many other neurons. Axons of presynaptic neurons Dendrites of postsynaptic neuron Cell body of postsynaptic neuron Axon hillock Axon of postsynaptic cell Excitatory synapse Inhibitory synapse

10. Neurons Integrate Information from Many Synapses Postsynaptic potentials sum. Action potential Threshold Resting potential

11. Neurotransmitters • More than 100 neurotransmitters are now recognized, and more will surely be discovered. • Acetylcholine is important and one of the first ones discovered because its involvement in muscle movement. • Dopamine and serotonin hugely important for many behaviors. • The workhorses of the brain are glutamate, glycine, and γ-aminobutyric acid (GABA).

12. Neurotransmitter Transport Proteins/Reuptake Neurotransmitters must be stopped. They have to be broken down and recycled by the neuron. E.g., Acetylcholine is broken down by acetylcholine esterase. Drug companies often target these 'reuptake' proteins for drug therapies.

13. ‘The Connectome’ • Sebastian Seung • Biophysicist/neurophysiologist @ MIT. • http://www.ted.com/talks/sebastian_seung

14. Mini-Brain/Nervous System Lecture Central Nervous System = brain and spinal cord (interneurons) Peripheral Nervous System = all other parts of nervous system besides brain & spinal cord - includes motor neurons and sensory neurons

15. The Functions of the PNS Form a Hierarchy Central nervous system (CNS) Information processing Peripheral nervous system (PNS) Sensory information travels in afferent division Most information travels in efferent division, which includes… Autonomic nervous system Somatic nervous system Sympathetic division Parasympathetic division

16. Neurons vs. Nerves • Neuron = a cell that is specialized for the transmission of nerve impulses. Typically has dendrites, a cell body, and a long axon that forms synapses with other neurons. Also called a nerve cell. • Nerve = A long, tough strand of nervous tissue typically containing thousands of neuronswrapped in connective tissue; carries impulses between the central nervous system and some other part of the body.

17. Sciatic Nerve The sciatic nerve is this huge nerve that leaves your lower back (and spinal cord) and runs the length of your leg. There are many different types of neurons. Some are myelinated, some are not. Smaller nerves branch off of the sciatic nerve. The sciatic nerve responsible for innervating muscles, skin, etc. in the leg. It contains both motor neurons and sensory neurons (i.e. messages go both way). There are some neurons that originate at the top and have axons that run the whole way to your foot. In other words, there are axons that are about 1 meter long.

18. How Does Information Flow through the Nervous System? The brain integrates sensory information and sends signals to effector cells. Sensory neuron CNS (brain  spinal cord) Sensory receptor Interneuron Motor neuron (part of PNS) Effector cells

19. How Does Information Flow through the Nervous System? When reflexes occur, sensory information bypasses the brain. Spinal cord Interneuron Motor neuron Sensory receptor Effector cells Sensory neuron

20. Brain Parts The brain is made up of four distinct structures. Inside view Cerebrum Conscious thought, memory Diencephalon Information relay and control of homeostasis Cerebellum Coordination of complex motor patterns Brain stemInformation relay and center of autonomic control for heart, lungs, digestive system

21. Functional Mapping Paul Broca Studied the brain of a person who could hear and comprehend, but not speak. Found a lesion on one part of the brain. First to claim that different parts of the brain did different things.

22. Brain Lesion

23. Brain Mapping – Electrical Stimulation • In treating people with severe seizures, doctors electrically stimulate the brain to find the area where the seizure originates from. • The idea is to remove this part of the brain with removing as little as possible from other adjoining areas. Doctors still do this today. • Based on electrical stimulation of conscious patients, we know that different parts of the brain do different things.

24. Brain Mapping – fMRI

25. Mapping of Brain to Anatomical Parts

26. Specific Brain Areas Have Specific Functions Cross section through area responsible for sense of touch and of temperature Head Leg Trunk Hip Fingers Arm Hand Thumb Nose Eye Lips Genitals Teeth Jaw Left hemisphere Tongue Intra-abdominal