Human Bio lecture notes, week of 02/08
Human Bio lecture notes, week of 02/08 BSC 2023
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This 6 page Class Notes was uploaded by Eleonora Sacks on Friday February 12, 2016. The Class Notes belongs to BSC 2023 at Florida International University taught by Paul Sharp in Spring 2016. Since its upload, it has received 21 views. For similar materials see Human Biology in Biology at Florida International University.
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Date Created: 02/12/16
Class Notes: week of 02/08 2/13/16 12:03 AM Cont.: Neurons, CNS and PNS • Na+: sodium, starts an action potential when is rushes inside the plasma membrane causes the flip of the signs • • Membrane potential: difference in electrical change between 2 sides of a membrane. • Resting membrane potential: polarized plasma membrane (-70 mV--you are -70 negative inside compared to the outside), the net number of positively charged ions outside and the negatively charged ions inside it • Sodium-potassium pump: membrane protein that uses ATP to pump 3 Na+ out and 2 K+ into the cell, there's always going to be a negative charge on the inside of the membrane this way. This sets things up for diffusion, because the Na+ will be in high concentration outside and will want to go inside and vice versa with the K+, when this happens, the action potential is happening. • Orange= sodium channel, pink=potassium channel • Potassium can sometimes leak out, this makes the inside even more negative. • What happens during action potential? 1. Conductance of a nerve signal in axons 2. All or nothing event (either works or doesn't work), self propagating 3. 1st sodium gates open resulting in depolarization (the first domino has fallen down) (once the gate opens, the sodium rushes inside the membrane because of diffusion, so the inside of the membrane will no longer be negative) 4. Next potassium gates open resulting in repolarization (lifting the domino back up) (the potassium rushes outside because of diffusion) 5. Sodium-potassium pump restores original ionic distribution • Stimulus: activates neuron and begins action potential (causes first domino to fall) if threshold is met (-40 Mv, when the voltage changes from -70 to -40, then the sodium gate opens up), eg: pricked by a pin • Protein channels (gates): 1. Voltage gated: opens and closes in response to voltage changes across membrane 2. Ligand gated: opens and closes when a specific chemical binds to it 3. Mechanically regulated: responds to physical distortions of the membrane surface • Class Notes: week of 02/08 2/13/16 12:03 AM • Synapse: • The junction between neurons (empty space between axon terminal/presynaptic membrane and cell body or dendrites/postsynaptic membrane); nerve signal can not jump synaptic cleft st 1 : presynaptic membrane (axon terminal) 2 : synaptic cleft rd 3 : postsynaptic membrane (usually dendrite) • Neurotransmitters: chemicals responsible for transmission across a synapse. Closer ti -40mV you will communicate, if its getting further from the -40mV, then no. The neurotransmitters get out through exocytosis. Stored in synaptic vesicles at axon terminal. Also transmits signal between: • Nerve--- muscle • Nerve--- organ • Nerve--- gland • • Events at synapse: 1. Nerve signal travels along axon to an axon terminal 2. Ca2+ ion gates open and Ca2+ rushes in axon terminal 3. Ca2+ ions promote fusion of synaptic vesicles with presynaptic membrane 4. Exocytosis of neurotransmitter into synaptic cleft and diffusion occurs 5. Neurotransmitters attach to receptors on the postsynaptic membrane. Only single type of channel opens 6. Excitatory or Inhibitory synapse, depending on the neurotransmitter 7. Integration: summing up of excitatory and inhibitory signals 8. Termination of neurotransmitter effects: degraded by enzymes 9. Reuptake by presynaptic membrane 10.Diffusion out of synapse • Neurotoxins: include numerous chemicals that poison the nerve. Ex. Novocain • Central Nervous System: sensory information is received & motor control is initiated • Meninges: protective membranes that cover brain and spinal cord. Eg. Meningitis- infection of the meninges • Cerebrospinal fluid: cushions and protects CNS; fills spaces between meninges. Helps maintain blood-brain barrier • • Ventricles: interconnecting chambers that produce and serve as a reservoir for cerebrospinal fluid. 1. Lateral ventricles: proximate to cerebrum 2. Third ventricle: proximate to diencephalon 3. Fourth ventricle: proximate to cerebellum (extends all the way down to the spinal cord) Class Notes: week of 02/08 2/13/16 12:03 AM • Grey matter: contains cell bodies and short, nonmyelinated fibers • White matter: contains neuron fibers that run together in bundles called tracts (the myelinated axons make it look white): • Ascending tracts take info to the brain • Descending tracts take info away from the brain • Tracts cross paths just after they enter and exit the brain • (spinal cord diagram) • Spinal cord: extends from base of brain and proceeds inferiorly in the vertebral column, allow for communication between brain and peripheral nerves, center for thousands of reflex arcs. Has grey matter on the inside and it looks like a butterfly, white matter on the outside (opposite to brain--brain has white inside and grey outside). • The bulb structure (dorsal root) is where the sensory information goes to brain and is ascending • The ventral root is of motor neurons that is descending • Brain: enlarged superior portion of the CNS located in cranial cavity of the skull • Cerebrum: largest part of brain, consists of 2 cerebral hemispheres (left and right). communicates with and coordinates the activities of the other parts of the brain o Left hemisphere: has greater control over language and mathematical abilities, logic, analysis o Right hemisphere: more visual-spatial skills, intuition, emotion and art and music • Sulci: grooves that divide each hemisphere into lobes: 1. Frontal lobe: motor functions, permits voluntary muscle control, enables one to think, problem solve, speak and smell 2. Parietal lobe: receives info from sensory receptors in skin and taste receptors in mouth 3. Occipital lobe: interprets visual input and combines it with other sensory experiences 4. Temporal lobe: sensory areas for hearing and smell • Cerebral cortex: outer layer of cerebral hemisphere, composed of grey matter, receives sensory info and controls motor activity. Accounts for sensation, voluntary movement and thought processes. Very thin layer (2-4mm) but makes up 40% of the biomass of the brain and has over 1 billion cell bodies. Enables us to perceive, communicate, remember, understand, appreciate and initiate voluntary movements (associated with consciousness). o Higher mental functions: memory (ability to hold a thought in mind or recall events from the past) and learning (retain information) • Diencephalon: part of the forebrain between the 2 hemispheres and midbrain. has the thalamus, 3rd ventricle and hypothalamus • Thalamus: "gatekeeper to the cerebrum" by controlling which received sensory info are passed on to the cerebrum (filters noises you don't pick up for example) • Hypothalamus: helps maintain homeostasis: regulates hunger, sleep, thirst, body temp, heart rate, etc and forms floor of 3rd ventricle. • Corpus callosum: extensive bridge of nerve tracts, enables communication between left and right hemispheres • Cerebellum: coordinates equilibrium and motor activity to produce smooth movement (looks like a tree)