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Biology Ch14
Nervous system and neurons
| Question | Answer |
|---|---|
| Overall function of nervous system is__________________ | receives and process sensory information from both external and internal environments to coordinate the body's activities |
| 3 major divisions | Central nervous system (CNS), Peripheral nervous system (PNS), Autonomic nervous system (ANS) |
| 3 functions of nervous system | Sensory, Integration, Motor |
| Sensory function | sensory receptors respond to stimuli by generating nerve signals that travel via the PNS to CNS |
| Integration function | The CNS sums up the input it receives from all over the body, stores memories, and creates motor responses |
| Motor function | Generates motor output, which travel from the CNS via the PNS to muscles, glands, and organs |
| 2 major nervous cell types | Neurons (nerve cells) and Neuroglial (glial/glia cells) |
| Neurons (nerve cells) | 3 categories (which are based on function) 1. sensory (afferent) - sensory receptors to CNS 2. Motor (efferent) - CNS to Effector 3. Interneurons (association) - between sensory and motor neurons |
| Neuroglial Cells (Glial/glial cells) | a. outnumber neurons 10:1 b. several types, each with a specific function (1. neuroglia in the CNS: microglia, astrocytes, oligodendrocytes; 2. Neuroglia in the PNS: Schwann cells) |
| Neuroglia in CNS | Microglia - phagocytic cells that remove bacteria and debris astrocytes - provide metabolic and structural support directly to neurons. Oligodendrocytes - form myelin sheathes in PNS |
| Neuroglia in PNS | Schwann cells - form myelin sheathes in PNS |
| 3 types of neurons (based on function) | sensory neuron, interneuron, motor neurons |
| Sensory neuron | carries nerve signals from a sensory receptor to the CNS a. sensory receptor - detect changes in the environment |
| Interneuron | found only in the CNS a. receive input from sensory neurons and other interneurons b. sum up signals received fomr other neurons, then communicate with motor neurons |
| Motor Neurons | carries nerve impulses away from the CNS to an effector a. muscle --> organ --> gland , these carry out the response to the environmental change |
| Q: you go to check the contents of a pot on the stove, touch the handle of the lid not realizing how hot it is. You almost immediately drop the lid. Which type of neuron carried the information that the lid was hot? | sensory neuron |
| Q: you go to check the contents of a pot on the stove, touch the handle of the lid not realizing how hot it is. You almost immediately drop the lid. Which type of neuron communicated directly with the effector ? | motor neuron |
| Parts of a neuron | dendrites, axon, cell body |
| Nerves consist of... | parallel axons, dendrites, or both from many neurons |
| Nerves are covered with... | tough connective tissue |
| Myelin Sheath | covers some axons |
| Myelin sheath in PNS | formed by Schwann cells which contain lipid substance myelin in their plasma membrane |
| Node of Ranvier | space/gaps between the myelin sheaths |
| Myeline sheath is composed of...... | plasma membranes of glial cells |
| long axons and short axons, myelin sheath? | long axons usually have myelin sheath, short usually dont |
| Gray matter (myelin sheath) | is grey because it contains NO myelinated axons |
| White matter (myelin sheath) | is white because it contains myelinated axons |
| Myelin sheath importance in nerve regeneration (in PNS) | the myelin sheath remains and serves as a passageway for new fiber growth, provides electrical insulation that increases rate of conduction of a nerve impulse and helps repair the axon |
| Saltatory condction | messages travel faster as they travel from one node of Ranvier to the next |
| In the CNS, ____________________ form the myelin sheath | oligodendrocytes |
| impulse moves from _________ to __________ along a myelinated axon | cell body, hops the nodes of ranvier, to dendrites |
| Multiple sclerosis | a disease where the myelin sheath in the brain and spinal cord are progressively destroyed |
| Nerve impulse/Action Potential | Electrochemical changes that convey the information within the nervous system |
| Polarization | neg and pos ions switch (works its way down the line) |
| Repolarization | switch back to original position |
| Refractory period | keeps the polarization only going one way down and not allowing it to go "backwards" |
| Resting potential | the potential energy of a neuron at rest |
| Resting potential exists because .... | the plasma membrane is polarized (a more positive charge outside the cell and more negative charge inside), measured in mV (millivolts) |
| neurons must maintain their resting potential to be able to ..... | send nerve impulses |
| sodium-potassium pump | pumps Na+ and K+ into neurons, will go against the concentration gradient, uses cellular energy |
| Action potential | nerve impulses |
| Action potential occurs in... | axons, a stimulus is a change that activates the neuron |
| Threshold | the minimum voltage that must be reached in order for an action potential to occur (equal to 55 mV) |
| Nerve impulse | action potential (an electrochemical signal involving sodium and potassium ions that cross the cell membrane channels) |
| Action Potentials are "______________" | all or nothing |
| Action Potentials - once threshold is reached, the action potential happens __________ | completely |
| In an action potential increasing the strength of the stimulus does not change the size of an action potential. Instead, to convey a stronger signal, __________________________________ | it causes more action potentials to occur |
| Action potential - sodium gates open | Depolarization - sodium channels open bringing Na+ into the cell causing it to become more positive inside Repolarization - Na+ channels close, K+ channels open, K+ runs out of the cell, making the cell become more negative again |
| Axon branch into fine endings called axon terminals, each terminal lies very close to either the dendrite or the cell body of another neuron, this region of close proximity is ________________ | called a synapse |
| 1st Event of Synapse | 1. nerve impulse/action potential travels along an axon to reach an axon terminal |
| 2nd event of synapse | 2. calcium ions enter the terminal and stimulate synaptic vesicles to merge with plasma membrane at the axon terminal of the sending membrane |
| 3rd event of synapse | 3. Neurotransmitter is released into the synaptic cleft and diffuses across to the receiving neuron, there they bind to receptor proteins within the plasma membrane |
| Synapse: Excitation | occurs if the neurotransmitter causes the sodium gates to open` |
| Synapse: Inhibition | occurs if a neurotransmitter causes potassium ions to exit the receiving neuron |
| Synaptic Integration | summing up multiple incoming excitatory and inhibitory signals |
| After a neurotransmitter has initiated a response, it is removed from the ___________ ______________ | synaptic cleft |
| reuptake | the sending membrane in synapse reabsorbs the neurotransmitter, can be blocked by drugs |
| Norepinephrine | important to dream, waking, and mood |
| serotonin | is involved in thermoregulation, sleeping, emotions, and perceptions |
| Dopamine | regulates emotions and complex movements |
| 2 major divisions of the nervous system | Central nervous system (CNS ) and Peripheral Nervous system (PNS) |
| Central nervous sytem are made up of | brain and spinal cord |
| Peripheral nervous system | Sensory - somatic sensory (muscles), visceral sensory (viscera) Motor - Somatic motor (can see happen), Visceral Motor (can not see happen) |
| Visceral Motor in Autonomic nervous sytem | regulates involuntary actiovities - sympathetic nervous system - in charge during emergencies (fight or flight) - parasympathetic nervous sytem - adjusts bodily functions during restful times ("Rest and digest") |
| Protection of the CNS | Bones of skull and vertebrae column, meninges (Dura Mater, Arachnoid, Pia mater), Cerebrospinal fluid, blood brain barrerier |
| Meninges | 3 connective tissue membranes that protect the central nervous system 1. Dura mater - outer 2. arachnoid - middle layer 3. pia mater - inner layer |
| Cerebrospinal fluid | fills space between meninges, ventricles of brain, and the central canal of the spinal cord |
| Functions of Cerebrospinal fluid | shock absorption, support, nourishment, waste removal (of neurons) |
| Excess cerebrospinal fluid goes where? | drains into the cardiovascular system |
| Blood brain barrier - structure | formed by tight junctions between the squamos epithelial cells of capillaries supplyign the central nervous system |
| Blood brain barrier - functions | protects the central nervous system by selecting the substances that can enter the cerebrospinal fluid from the blood |
| Blood brain barrier - negative effect | it can stop many potentially life-saving, infection-figting, or tumor-suppressing drugs, from reaching brain tissue if they are not lipid soluble |
| Cerebrum | a. the thinking ,concious part of the brain b. largest part of the brain c. accounts for 83% of total brain weight d. divided into two hemispheres by the longitudinal fissure |
| Each hemisphere of the brain ____________________ and __________________ | receives sensory information from, directs movements of the opposite side of body |
| Gyri | thick folds seperated by shallow grooves (sulci) |
| Cerebral cortex | thin outer layer of the cerebrum? |
| Corpus Callosum - structure | thin, highly convoluted outer layer of cerebral hemispheres (composed of gray matter) |
| Corpus Callosum - function | responsible for sensation, voluntary movement, thought processes, and consciousness |
| _______________ is the last center to receive sensory input and carry out integration before comanding voluntary motor responses. this also communicates with and coordinates the activities of other parts of the brain. | corpus callosum |
| lobes of brain | frontal, parietal, occipital, temporal |
| Sensory (senses of vision, hearing, smell, taste and touch) are part of what lobes of the brain? | parietal, occipital, temporal |
| Motor (voluntary movements) is part of what lobes of the brain? | frontal |
| Associatin (judgement, analysis, learning, creativity) are part of what lobes of the brain | Frontal, parietal (only part of it), occipital, and temporal |
| Lobe for skin senses? (touching something, pressure) | parietal |
| lobe for taste? | parietal |
| Lobe for Olfaction? | frontal/temporal |
| lobe for hearing? | temporal |
| lobe for vision? | occipital |
| Vestibular | spatial orientation and self-motion perception |
| Visceral sensory area | receives information from the thalamus |
| primary somatosensory area | just behind the central sulcus in the parietal lobe (sensory information from skin and skeletal muscles arrive here, large areas are dedicated to thos body areas with acute sensation, face and hands occupy the largest part) |
| Primary motor area | in the frontal lob just before central sulcus (voluntary signal to skeletal muscles begin here, muscles that control facial movements (Swallowing, salivation, expression) take up an especially large portion) |
| Premotor area | anterior to/in front of, the primary motor area (coordinates learned motor skills that are patterened or repetitive ("muscle memory") |
| Association areas | communicate with the sensory area, motor areas, and other parts of the brain to analyze and act on sensory input |
| Prefrontal cortex | enables us to reason, think, plan for the long term, think about abstract thoughts |
| Midbrain includes | thalamus and hypothalamus |
| Thalamus | two masses of grey matter, it is the "gateway to the cerebral cortex", which means no sensory information makes it there without a stop here (except sense of smell), also direvts motor activity, cortical arousal and memory |
| Hypothalams | controls autonomic nervous system, maintains homeostasis (blood pressure, heart rate, breathing rate, digestion - higner/fullness, body temperature, water balance), influenxes pituitary gland to coordinate nervous and endocrine system, regulates emotions |
| Cerebellum | integrates information from the motor cortex and sensory pathways (produce smooth, well-timed voluntary movements, coordinates eye movements with body movements, controls equilibrium, posture, balance) |
| Brainstem components | midbrain, pons, medulla oblongata |
| Midbrain function | relay station between cerebrum and the spinal cord/cerebellum, processes inormation about sights and sounds, controls simple reflex responses to these stimuli such as turning your head toward a loud sound |
| Pons | a. connects/bridges different parts together (spinal cord and cerebellum to cerebrum, thalamus, and hypothalamus) b. with the medulla oblongata, they regulate breathing rate c. reflex center, coordinate head movements in response to stimuli |
| Medulla oblongata - serves as the pathway for | all sensory messages going to the higher brain centers, all motor messages leaving the brain |
| Medulla Oblongata - contains flex centers for reflexing | heartbeat, breathing, vasoconstriction (blood pressure) |
| Medulla oblongata - reflect centers for | vomiting, coughing, sneezing, hiccupping, swallowing |
| limbic system | defined on the basis of function rather than anatomy, produce emotions and memory, integrates emotions with higher mental functions (reasoning, memory) |
| Amygdala | creates the sensation of fear (part of limbic system) |
| Hippocampus | plays a crucial role in learning and memory |
| higher mental functions | memory and learning and reticular activating system |
| short-term memory | holds a small amount of information for a few seconds or minutes, stored in prefrontal |
| long-term memory | stores limitless amounts of information for hours, days, or years, ie memorized facts |
| semantic memory | memorized number, words |
| episodic memory | memorized persons, events |
| skill memory | perofrming motor activities |
| learning | retain and use past memories |
| Reticular activating system is ... | an extensive network of neurons that runs through the medulla and projects to the cerebral cortex, hypothalamus, and thalamus |
| Reticular activating system does... | a. filters sensory input b. keeps the cerebral cortex in an alert and attentive state c. stimulates muscle tone, aids posture d. helps keep balance when one foot is raised e. habituation f. pain control pathways |
| Pain control pathways of Reticular activating system | 1. general anesthetics suppress it 2. natural endorphons and apiates and morphine act here |
| Habituation | brain learns to ignore repetitive inconsequential stimuli |
| Spinal cord structure | tube of neural tissue with a central canal inside, white matter toward surface, gray matter in center |
| Spinal cord functions | conducts messages between the brain and the body, serves as a reflex center, locomotion |
| locomotion | walking - movements of limbs initiated by cerebrum - spinal cord takes over the movement from there |
| reflex arcs | automatic response to stimulus in a pre-wired circuit |
| Part of the spinal cord "circuit" | receptor, sensory neuron, interneuron (1+), motor neuron, effector |
| Spinal reflexes are decisions made by the __________________ when a speed reaction is safer | spinal cord |
| Peripheral nervous system includes ... | spinal nerves, cranial nerves, |
| spinal nerves | originate from the spinal cord, carry both sensory and motor fibers |
| CN1 | olfactory nerve |
| CN2 | optic nerve |
| CN3 | Oculomotor nerve |
| CN4 | Trochlear nerve |
| CN5 | Trigeminal nerve |
| CN6 | abducens nerve |
| CN7 | Facial nerve |
| CN8 | Vestibulocochlear nerve |
| CN9 | Glossopharyngeal nerve |
| CN10 | Vagus nerve |
| CN11 | Accessory nerve |
| CN12 | Hypoglossal nerve |
| Subdivisions of the Peripheral nervous system | Somatic nervous system, autonomic nervous system (sympathetic and parasympathetic) |
| Somatic nervous system | governs conscious sensations and voluntary movements |
| Autonomic nervous system | governs unconscious involuntary internal activities (ie cardiac, smooth muscles, organs, glands) |
| Sympathetic nervous system | prepares the body for "fight or flight", increases heart rate, dilates the airways, for a ready supply of glucose and oxygen |
| Parasympathetic nervous system | adjusts body functions so that energy is conservedd during restful times, "rest and digest", promotes digestions of food, slows heart rate |
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