A&P Theory Unit 9 Notes PDF

**[A&P Theory Unit 9 Notes: ]** The nervous system has been called the **master control system** of the body, as it controls and coordinates all the functions of the body. **Major functions include:** - Monitoring the body\'s internal and external environments - Integrating sensory informati...

**[A&P Theory Unit 9 Notes: ]** The nervous system has been called the **master control system** of the body, as it controls and coordinates all the functions of the body. **Major functions include:** - Monitoring the body\'s internal and external environments - Integrating sensory information - Coordinating voluntary and involuntary responses **[Two Main Divisions of the nervous system]**: **Peripheral:** All nervous tissue outside of the CNS, contains cranial and spinal nerves (responds to impulses/ liaison between brain and spinal cord and the rest of the body) **Central:** Coordinates sensory processing and motor nerve transmission, consists of the brain and spinal cord. (Dorsal body cavity) **Afferent Division:** brings information to the CNS from receptors in the body tissues and organs. - Receptors: Sensory structures that detect changes in the environment or respond to specific stimuli - Many different types of receptors are found in the Peripheral Nervous System. **Efferent Division:** (E for Exit) Carries information away from the CNS to effectors It is also known as the motor division. - Effectors: Muscles and glands that respond to neural commands to carry out motor responses. **[Breakdown of Nervous System:]** **[Somatic and Autonomic:]** **Somatic Nervous System:** (Soma means body) voluntary, controls skeletal muscles consciously. **Autonomic Nervous System:** The ANS is responsible for involuntary control of the body for the sake of homeostasis. Controlling smooth muscle, cardiac muscle, and glands. Involuntary responses. **Sympathetic Division**: "Fight or flight" division includes heart rate and increased rate and depth of breathing **Parasympathetic division** (p for peace) rest and digest, heart rate is slowed, rate of digestion increases. **[Neurons: ]** Neurons receive and send information via electrochemical impulses, called action potentials. It allows communication from one cell to another. Structures of Neurons: Soma: main part of the neuron, aka cell body. Organelles are located (Mitochondria, nucleus, Golgi body, etc.) Nissl body: Protein synthesis occurs here Dendrites: receives info from other neurons at specialized areas of contact called synapses. They conduct nerve impulses/ action potentials towards the cell body Axon Hillock: Area where action potential begins Axon: carries electrical signal away from cell body towards a target cell (muscle/gland) Shawann Cells: made up of myelin sheath, thick lipid layer to insulate axon Axon Collaterals: Branches off a main axon, that allow a neuron to communicate with different types of cells. Axon Terminals: end of the axon where there are several branches extending toward the target cell. Axon terminals are where the vesicles of neurotransmitters are contained. Synapse: a narrow junction across which a chemiocal signal passes from neuron to the next, intiautring a new electrical signal in the target cell. **[Types of Neurons: ]** Unipolar: - Unipolar neurons have only one process emerging from the cell. - At one end of the axon are dendrites, and at the other end, the axon forms synaptic connections with a target. - Unipolar cells are exclusively sensory neurons. Bipolar: - Bipolar neurons have two processes, which extend from each end of the cell body, opposite to each other. - One is the axon and one the dendrite. Bipolar cells are not very common. - They are found mainly in the olfactory epithelium, and as part of the retina. Multipolar Neuron: Multipolar neurons have one axon and two or more dendrites (usually many more). These are the most common type of neuron, especially in the CNS. Efferent **[Neuron Organization: ]** **[Neuron Organization in PNS:]** Spinal Nerves: There are **31 pairs** of spinal nerves that branch off of the spinal cord. These nerve carry both sensory input and motor output. Cranial Nerves: There are **12 pairs** of cranial nerves located in the brain that carry a combination or sensory, motor of both types of innervation to specific areas of the head, face & neck. **[Neuron Organization in the CNS]** Collections of neuron cell bodies are called nuceli. Bundles of axons are called tracts. **[Glial Cells:]** **Astrocytes:** - Regulation of ion concentration - Uptake and/or breakdown of some neurotransmitters - Formation of the blood-brain barrier - Reaction to tissue damage **Oligodendrocytes:**\ Main glial cells in CNS, makes myelin sheath **[Myelin: ]** Myelin is a **lipid-rich** sheath that surrounds the axon. It speeds up the transmission of electrical signals along the axon, causing the action potential to \"jump.\" **White Matter:** White matter is white because axons are insulated with myelin. It includes all of the nerves of the PNS and much of the interior of the spinal cord and brain. **Gray Matter:** Gray matter is unmyelinated and found in clusters of neurons in the brain and spinal cord. **Microglia:** - Microglia are smaller than most other glial cells, as their name implies, and also the rarest type of glial cell. - These cells protect the nervous system against infection and are related to macrophages, which are white blood cells. They are phagocytes, as they ingest and digest those cells or the pathogens that cause disease, or any cellular waste. **Ependymal Cells:** Ependymal cells line the ventricles of the brain and central canal of the spinal cord. They filter blood to make cerebrospinal fluid (CSF), the fluid that circulates through the CNS. **Satellite and Schwann Cells (S in the PNS)** Satellite Cells: Like astrocytes in terms of function, minus establishing the BBB, regulating ion concentration, reacting to tissue damage, protecting cell bodies. Schwann Cells: Insulate axons with myelin **[Ion Channels and Processes of Nerve Transmission at a Synapse: ]** **Electrical Synapse:** there is a direct connection between the two cells so that ions can pass from one cell to the next, has gap junctions. Least common. Connexxons: **Chemical Synapse:** most common, alloiw for relase and transmission of neurotransmitter. Two parts that allow for chemical synapse to take place. Protein channels allow for ions to pass into and out of the cell. **[Types of Channels:]** Voltage-gated channels: based on charge. found at axon hillock, nodes of Ranvier, unmyelinated axons, dendrites Leak Channels: open randomly, open or closed at any time. Chemically gated channels: a grouping of channels that are open or closed by neurotransmitters Mechanically Gated Channels: based on touch, open based on distortion of the membrane NA+: sodium is a positively charged ion, and is found in higher concentrations outside the cell/ When sodium comes into the cell, it makes the cell more positive, called depolarization. K+: A cation, but higher concentrations inside the cell than outside, when K+ leaves the cell it will become more negative, repolarization. CL- is negative, higher concentration outside the cell, when it comes into the cell, it makes it more negative and tougher to reach an action potential. CA2+ is a positively charged ion and found in higher concentrations outside the cell. When it comes into the cell, it can make it more positive **[Action Potential:]** Change in voltage of a cell membrane in response to a stimulus that results in transmission of an electrical signal; unique to neurons and muscle fibers **[Depolarization:]** Movement of a cell's membrane potential to a more positive value (moving closer to zero). **[Repolarization:]** Movement of a cell's membrane potential to a more negative value. **[Hyperpolarization:]** Movement of a cell\'s membrane potential to a more negative value past -70mV. - Resting membrane potential is the membrane potential of an undisturbed cell. It describes the steady state of the cell, which is a dynamic process that is balanced by ion leakage and ion pumping. - The resting membrane potential is at a voltage of -70 mV, meaning it is more negative on the inside relative to the outside, largely due to large negatively charged proteins inside the cell. **[Extracellular Fluid:]** Extracellular fluid is high in Na+ and Cl- **[Intracellular Fluid:]** Intracellular fluid is high in K+ and negatively charged proteins **[Sodium-Potassium Pump]**: Sodium in of the cell, potassium out of the cell. Uses active transport. **[Ion Pump:]** The Na+/K+ pump is an important ion pump found in the membranes of many types of cells. These pumps are particularly abundant in nerve cells, which are constantly pumping out three sodium ions and pulling in two potassium ions to maintain an electrical gradient across their cell membranes. - Neurons are excitable. This means that a stimulus can trigger them to send electrical signals called action potentials. - Neurons only generate action potentials if the stimulus is strong enough to hit a minimum threshold. - Weak stimuli- like a light touch, a minor temperature change, or a very small change in voltage- do not trigger an action potential. **[Graded Potential:]** Graded potentials are temporary changes in the membrane voltage, the characteristics of which depend on the size of the stimulus. The stimulus of a graded potential is not strong enough to cause an action potential. - Any **depolarization** that does not change the membrane potential to -55 mV or higher will not reach threshold and thus will not result in an action potential. - Once the threshold is reached again, another action potential will fire. Action potentials are *"all or none."* - Inside of the cell is more negative than the outside of the cell Stages of Action Potential: 1. Resting Membrane Potential 2. Stimulus that reaches threshold 3. Depolarization 4. Repolarization 5. Hyperpolarization 6. Return to Resting membrane potential The depolarization and repolarization of an action potential are dependent on two types of channels: - Voltage-gated Na+ channel - Voltage-gated K+ channel **Refractory Period:** While an action potential is in progress, another one cannot be initiated. That effect is referred to as the refractory period Axon potential=nerve impulse **[Propagation:]** how is the axon potential traveling **[Continuous conduction:]** is slow because there are always voltage-gated Na+ channels opening, and more and more Na+ is rushing into the cell. Propagation along an unmyelinated axon is referred to as continuous conduction. **[Saltatory:]** Propagation along the length of a myelinated axon is saltatory conduction. Saltatory conduction is faster because the action potential basically jumps from one node to the next (saltare = "to leap"), and the new influx of Na+ renews the depolarized membrane. **dendrite \>\> cell body \>\> along axon \>\> synapse (gap) \>\> dendrites**. In a cell permeable only to K^+^, the resting membrane potential would be called the \_equilibrium\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ potential for K^+^, which is \_\_\_-90\_\_\_\_\_\_\_ mV. In an excitable cell, also permeable to Na^+^ and Cl^--^, the electrochemical gradient for Na^+^ causes it to move into\_\_\_\_\_\_\_\_\_ the cell. b\. What force tends to pull K^+^ back into the cell? \_electrical gradient\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ **[Neurotransmitters: ]** - Neurons communicate with other cells by releasing chemicals called neurotransmitters. - Neurotransmitters can cause gates and channels to open. - There are several types of neurotransmitters that are found at various synapses in the nervous system. Some examples are acetylcholine, serotonin, noradrenaline, and GABA. **[Adrenaline:]** Fight or Flight Produced in stressful situations. Increases heart rate and blood flow. Leads to physical boost and heightened awareness. Also known as epinephrine. **[GABA:]** Calms firing nerves in the CNS. High levels improve focus, low levels cause anxiety. Also contributes to motor control and vision. **[Noradrenaline:]** Concentration Affects attention and responding actions in the brain. Contracts blood vessels, increasing blood flow. Also known as norepinephrine. **[Acetylcholine:]** Learning Involved in thought, learning, and memory. Activates muscle action in the body. Also associated with attention and awakening. **[Dopamine:]** Pleasure Feelings of pleasure and euphoria, movement, and motivation. People repeat behaviors that lead to dopamine release. Associated with addiction. **[Glutamate:]** Memory Most common neurotransmitters. Involved in learning and memory. Regulates development and creation of nerve contacts. **[Serotonin:]** Mood Contributes to well-being and happiness. Helps sleep cycle and digestive system regulation. Affected by exercise and light exposure. **[Endorphins:]** Euphoria Released during exercise, excitement, and sex. Produces well-being and euphoria and reduces pain. **[Receptors: ]** **[Nicotinic:]** Nicotine will bind to the nicotinic receptor and activate it similar to acetylcholine. Nicotinic are excitatory receptors. **[Muscarinic:]** Muscarine, a product of certain mushrooms, will bind to the muscarinic receptor, and can be either excitatory or inhibitory. - Epinephrine and norepinephrine are biogenic amines, which is a group of neurotransmitters that are enzymatically made from amino acids. - They have amino groups in them, but no longer have carboxyl groups an**d are therefore no longer classified as amino acids.** PNS\