Bio 141 | Lecture 7 | Action Potentials & Organization of NS
Bio 141 | Lecture 7 | Action Potentials & Organization of NS Bio 141
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This 4 page Class Notes was uploaded by Gabriella Morales on Sunday February 7, 2016. The Class Notes belongs to Bio 141 at Pennsylvania State University taught by Dr. Jenelle Malcos in Winter 2016. Since its upload, it has received 19 views. For similar materials see Biology and Physiology in Biology at Pennsylvania State University.
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Date Created: 02/07/16
Action potentials Friday, January 29, 2016 9:09 AM Local Potentials VS. Action Potentials Local Potential -Triggered by receptors and neurotransmitters Can depolarize or hyperpolarize the membrane Are graded (proportional to strength of stimuli) Reversible (to a certain point, threshold) Local (effects are close to the origin) Decremental Refractory period- Time when a region of a neuron cannot fire another action potential Absolute- Impossible Refractory- Possible but unlikely (Stimulus must be super strong) Conduction: Dendrites / Cell Body > Axon After the initial action potential o High influx of sodium diffuses in the cytoplasm from point of entry o Causes adjacent voltage-gated channels to open o Process continues down the axon o One-way because of refractory period Continuous propagation (every part of membrane must be excited) Myelin Sheath Helps to electrically insulate axons Made of oligodendrocytes in the CNS and Schwann cells in the PNS o Lipid/protein dense Allows for very fast propagation of signal o Signal is not lost to environment Important for conductivity Conduction for Myelin Sheaths Faster than unmyelinated axons Action potentials only occur at nodes of Ranvier o Myelin sheaths allows ions to diffuse further because they cannot be transported to the ECF by pumps Signal "jumps" down the axon > salutatory propagation New PowerPoint - Synaptic activity involves the process of secretion (converting and electrical signal to a chemical signal.) This allows neurons to communicate with each other Pre and Post Synaptic Activity Neurotransmitters are synthesized in the cell body and transported in vesicles to the axon terminal Many neurotransmitters are derived from amino acids (dopamine or norepinephrine,) but some can be gaseous or made of other chemicals (acetylcholine.) Vesicles transport down the axon to the synapse (or back to the cell body for recycling) uses microtubules (cytoskeleton.) Organization of Nervous System Friday, January 29, 2016 9:08 AM Central Nervous System: Composed of the brain and spinal cord Houses both the cell bodies and axons Peripheral Nervous System: Composed of neurons that travel to/ leave from the CNS Houses Axons and ganglion Axons are grouped together in nerves Ganglion: Only location of the cell bodies outside of the CNS Afferent and Efferent neurons are classified as somatic, visceral, or special Afferent (Sensory) Neurons: Located in PNS Has three classes o Somatic- forms bones, muscles, and skin o Visceral - forms organs o Special- Hearing, sight, taste, smell Interneurons Located in CNS Efferent (Motor) neurons Located in PNS 2 classes o Somatic- to bones, muscle, skin o Visceral- to organs Somatic sensory neurons collect info from the skin, muscles, joints, and bones Monitored by receptors ( specialized afferent neurons) or receptor cells (specialized cells that synapse with afferent neurons) Proprioceptors- Neurons that send signals to the brain about the body's movement (where and how fast you are moving in space) Visceral Sensory Receptors Input from internal organs Most are chemoreceptors ( receptors that sense chemicals ) Motor Division 2 divisions o Somatic Motor: Voluntary movement (muscle contraction) o Visceral Motor (Autonomic Nervous System) Involuntary responses of organs Mainly function to adjust activity Targets do not depend on ANS to function o Visceral Motor has 2 divisions Sympathetic: Fight or flight response Para-sympathetic: Rest and digest o Function depends on sensory input and integration in CNS The somatic motor division involves one efferent neuron traveling to a target The axon terminal can branch to excite multiple parts of a muscle, but there is one main target (effector) Efferent neurons secrete acetylcholine - cholinergic neurons The visceral motor division involves two efferent neurons traveling to multiple targets Path includes spinal cord > ganglion > target tissue There are many post-ganglionic neurons for each pre-ganglionic neuron This allows for a WIDESPREAD RESPONSE where one signal from the CNS can alter the function of many organs (divergence) Efferent neurons secrete acetylcholine (cholinergic neurons) or norepinephrine (adrenergic neurons) Brain - CNS (Integrating Center) Organ made of neurons Gray matter > location of neuron dendrites and cell bodies White matter > Location of axons There are billions of neurons in the brain Trillions of synapse's Many neurons in the brain specifically communicate with other parts of the brain Region and Function of the Brain: Responses in our body range from primitive to higher-order Hindbrain: Primitive responses common to all animals (heart rate, breathing rate, blood pressure, movement, coordination) Midbrain More specialized, integrates info from special sense and movement Forebrain Most specialized in human Integrate info to help regulate complex organ systems Integrate conscious thought
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