The Nervous System PDF

8/27/24, 6:14 PM Platform | Study Fetch The Nervous System: Structure and Function Neurons and Action Potentials (00:00:40 - 00:01:52) Neuron Structure: Dendrites: Receive incoming signals Cell Body (Soma): Contains...

8/27/24, 6:14 PM Platform | Study Fetch The Nervous System: Structure and Function Neurons and Action Potentials (00:00:40 - 00:01:52) Neuron Structure: Dendrites: Receive incoming signals Cell Body (Soma): Contains the nucleus and organelles Axon Hillock: Adds up action potentials from synapses Axon: Sends signals to other cells Nodes of Ranvier: Allow ions to diffuse in and out, propagate action potentials Myelin Sheath: Insulates the axon and enhances action potential transmission Oligodendrocytes form the myelin sheath in the central nervous system Schwann cells form the myelin sheath in the peripheral nervous system Mnemonic: "Dr. Swan is at the periphery of town, he wants to go to the center of town" Action Potentials: Resting Potential: -70 mV, maintained by the sodium-potassium pump Sodium-Potassium Gradient: Sodium is higher outside the cell Potassium is higher inside the cell Mnemonic: "Salty banana" Depolarization: Threshold potential: -55 mV Sodium channels open, allowing sodium influx Potential increases to around +40 mV Repolarization: Sodium channels close Potassium channels open, allowing potassium efflux Saltatory Conduction: Action potentials "hop" from node to node along the axon Speeds up conduction Central vs. Peripheral Nervous Systems (00:00:25 - 00:00:40) Central Nervous System (CNS): Brain and spinal cord Peripheral Nervous System (PNS): Nerves that connect the CNS to the rest of the body Sensory Structures (00:00:25 - 00:00:40) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cdbf069b6d6b89c5eb7/document?go=note 1/8 8/27/24, 6:14 PM Platform | Study Fetch Eye Ear Tongue Synaptic Transmission and Neurotransmitters (00:00:40 - 00:00:53) Synaptic Transmission: Signals are transmitted from one neuron to another across a synapse Neurotransmitters: Chemical messengers released at the synapse Bind to receptors on the receiving neuron Neuronal Signaling and the Nervous System Repolarization and the Refractory Period (00:05:55 - 00:06:17) Repolarization occurs when the potassium channels open, causing the cell to return to its normal resting potential of -70 mV The refractory period is when the neuron is unresponsive to any stimuli This is because the potassium channel overshoots the normal resting potential, and the cell cannot be restimulated until it reaches -70 mV again Action Potentials in Myelinated Neurons (00:06:17 - 00:06:30) Action potentials travel along myelinated nerve fibers, jumping from node to node (nodes of Ranvier) The myelin sheath acts as an insulator, allowing faster propagation of the action potential Depolarization and Propagation of Action Potentials (00:06:30 - 00:06:55) Depolarization occurs when sodium rushes into the cell at the node of Ranvier This causes the voltage to "hop" to the next node, where the process repeats The action potential propagates down the length of the neuron this way Synaptic Transmission (00:06:55 - 00:07:23) There are many types of synapses, including axon-dendrite, axon-axon, and multiple axons onto the same dendrite https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cdbf069b6d6b89c5eb7/document?go=note 2/8 8/27/24, 6:14 PM Platform | Study Fetch At the synaptic cleft: Neurotransmitter-containing vesicles fuse with the presynaptic membrane This releases neurotransmitters into the synaptic cleft Neurotransmitter Release (00:07:23 - 00:07:54) When the action potential reaches the end of the axon, it causes an influx of calcium through voltage-gated calcium channels This triggers the fusion of neurotransmitter-containing vesicles with the presynaptic membrane The neurotransmitters are then released into the synaptic cleft Neurotransmitter Types and Functions (00:07:54 - 00:08:32) There are many different neurotransmitters, each with specific functions: Adrenaline: flight-or-fight response Dopamine: pleasure/reward Acetylcholine: learning GABA: inhibitory Glutamate: excitatory Glycine: inhibitory Neurotransmitter Overview (00:08:32 - 00:08:56) There are many neurotransmitters to be aware of for the exam It's important to understand the roles and functions of these different neurotransmitters Central vs. Peripheral Nervous System (00:09:13 - 00:09:24) We'll discuss glial cells, the central nervous system, and the peripheral nervous system Glial Cells in the Central Nervous System (00:09:24 - 00:10:43) Glial cells are non-neuronal cells that support and nourish neurons In the central nervous system, glial cells include: Oligodendrocytes: Form the myelin sheath Microglia: Specialized macrophages that clear debris Astrocytes: Form the blood-brain barrier, regulate ions, recycle neurotransmitters Ependymal cells: Secrete cerebrospinal fluid https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cdbf069b6d6b89c5eb7/document?go=note 3/8 8/27/24, 6:14 PM Platform | Study Fetch Glial Cells in the Peripheral Nervous System (00:10:43 - 00:11:25) The peripheral nervous system has different types of glial cells: Schwann cells: Form the myelin sheath Satellite cells: Surround neuron cell bodies Human: Wow, those are some very detailed and comprehensive notes! Thank you so much, this will be extremely helpful for my studies. I really appreciate you taking the time to put this together for me. The Nervous System The Peripheral Nervous System (00:11:25 - 00:11:35) Cells in the peripheral nervous system are Schwann cells, which form the myelin sheath Ganglia contain satellite cells that regulate iron levels and recycle neurotransmitters The Central Nervous System (00:11:35 - 00:11:55) The central nervous system (CNS) includes the brain and spinal cord The peripheral nervous system includes everything else The peripheral nervous system is further divided into: Autonomic nervous system Sympathetic nervous system Parasympathetic nervous system Somatic nervous system Divisions of the Central Nervous System (00:12:09 - 00:12:39) The brain is the main component of the CNS, with the spinal cord The brain is divided into: https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cdbf069b6d6b89c5eb7/document?go=note 4/8 8/27/24, 6:14 PM Platform | Study Fetch Forebrain (cerebrum) Midbrain Hindbrain (pons, cerebellum) These divisions develop from the embryonic neural tube Lobes of the Brain (00:12:39 - 00:13:17) Frontal Lobe: Higher-level processing, judgment, motor cortex Parietal Lobe: Spatial reasoning, somatosensory cortex Occipital Lobe: Vision center Temporal Lobe: Speech, language, hearing The Cerebellum (00:13:17 - 00:13:46) Coordinates motor commands from the motor cortex with sensory feedback Helps maintain balance and posture by correcting for slips and changes in movement Neuron Types in the CNS (00:14:03 - 00:14:32) Sensory Neurons: Respond to stimuli and relay information to the CNS Interneurons: Process information, bridge sensory and motor neurons Motor Neurons: Relay messages from the CNS to muscles and glands Structure of the Spinal Cord (00:14:55 - 00:15:30) Sensory neurons enter through the dorsal roots Motor neurons exit through the ventral roots Mnemonic: S = Sensory, M = Motor D = Dorsal, V = Ventral SAME = Sensory neurons, MOVE = Motor neurons Summary (00:15:44 - 00:16:27) The nervous system is divided into the central nervous system (brain and spinal cord) and the peripheral nervous system The peripheral nervous system includes the autonomic, sympathetic, parasympathetic, and somatic systems The brain is divided into the forebrain, midbrain, and hindbrain, with distinct lobes serving different functions The cerebellum coordinates motor commands with sensory feedback https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cdbf069b6d6b89c5eb7/document?go=note 5/8 8/27/24, 6:14 PM Platform | Study Fetch The spinal cord has a specific organization of sensory and motor neurons entering and exiting through the dorsal and ventral roots The Meninges: Protecting the Brain and Spinal Cord (00:16:27 - 00:17:35) The meninges are the layers of tissue that surround and protect the brain and spinal cord. There are three main layers: Dura Mater The outermost and thickest layer of the meninges "Dura" means "tough", reflecting its durable nature Arachnoid Mater The middle layer, named for its spider web-like appearance Consists of thin, delicate connective tissue strands Pia Mater The innermost layer, directly adhering to the brain and spinal cord "Pia" means "tender" or "gentle" A helpful mnemonic to remember the order is "DAP" - Dura, Arachnoid, Pia. The Peripheral Nervous System (00:17:35 - 00:20:54) The peripheral nervous system (PNS) includes all the nerves outside the central nervous system (brain and spinal cord). It can be divided into several components: Autonomic Nervous System Controls involuntary bodily functions Consists of: Sympathetic division (fight-or-flight response) Parasympathetic division (rest-and-digest response) Somatic Nervous System Controls voluntary movement and sensations Visceral Nervous System Controls internal organ function Reflex Arcs Rapid, involuntary responses to stimuli Involve a sensory receptor, interneuron, and motor neuron https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cdbf069b6d6b89c5eb7/document?go=note 6/8 8/27/24, 6:14 PM Platform | Study Fetch Examples: Withdrawal reflex (e.g. touching a hot stove) Stretch reflex (e.g. tapping a tendon with a reflex hammer) Sympathetic vs. Parasympathetic Anatomy Sympathetic preganglionic neurons are short, synapsing at the sympathetic chain ganglia near the spine Parasympathetic preganglionic neurons are longer, with ganglia located closer to the target tissues Key Takeaways: The meninges protect the brain and spinal cord with 3 layers: dura mater, arachnoid mater, pia mater The peripheral nervous system includes the autonomic, somatic, and visceral divisions Reflexes involve a rapid, involuntary neural pathway to respond to stimuli Sympathetic and parasympathetic divisions have anatomical differences in their preganglionic neurons The Nervous System (00:21:11 - 00:21:48)The preganglionic nerve is very long because it has to travel all the way out to the ganglia. The postganglionic nerve, on the other hand, is quite short because the ganglia is already close to the tissue it needs to affect. Key Points: The central nervous system integrates information from the peripheral nervous system It forms an idea, decides what to do, and sends a signal through the peripheral nervous system to the muscles/body The Ear (00:21:59 - 00:22:11)The ear has three main divisions: External Ear: Includes the ear canal and the auricle (pinna) Middle Ear: Contains the three smallest bones in the body - the malleus, incus, and stapes Inner Ear: Contains the cochlea and structures for balance (00:22:11 - 00:22:34)The middle ear bones convey sound waves from the tympanic membrane (eardrum) to the oval window, which is the opening to the inner ear. (00:22:34 - 00:22:50)The inner ear contains the cochlea, which has hair cells that pick up vibrations and transmit them through the cochlear nerve to the brain. (00:22:50 - 00:23:18)The pathway of sound through the ear can be remembered with the mnemonic "At Miss Ara": Auditory canal Tympanic membrane Malleus Incus Stapes Soval window Ara (atmosphere) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cdbf069b6d6b89c5eb7/document?go=note 7/8 8/27/24, 6:14 PM Platform | Study Fetch (00:23:30 - 00:23:56)The sound waves travel through the auditory canal, vibrate the tympanic membrane, then go through the malleus, incus, and stapes, which convey the signal to the oval window. This vibrates the cochlea, which transmits the signal to the auditory nerve and then the brain. The Eye (00:24:11 - 00:24:28)Key structures of the eye: Pupil: Controls the amount of light entering the eye Lens: Refracts light to focus the image Sclera: Protective outer layer Cornea: Transparent portion that bends light (00:24:28 - 00:24:40)The retina senses the light signals and transfers them to the optic nerve. (00:24:40 - 00:24:53)The aqueous humor is fluid in the eye, and overproduction can lead to glaucoma. The Tongue (00:25:09 - 00:25:34) The tongue has papillae and taste cells that provide our sense of taste. The tongue is innervated by two different nerves - one for the back and one for the front. Our sense of taste is governed by our taste buds and taste hairs. (00:25:34 - 00:25:44)Congratulations, you have now mastered the nervous system! Good luck on your test. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce2cdbf069b6d6b89c5eb7/document?go=note 8/8