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nervous system
| Question | Answer |
|---|---|
| Corpus callosum | Large fiber tract; connects 2 hemispheres |
| Lobes | Major regions (named for cranial bones): parietal, frontal, temporal, occipital |
| Gyri | Elevated ridges of tissue (Folds) |
| Sulci | Shallow grooves |
| Fissures | Deeper grooves, separate large regions of brain |
| Motor and sensory functions | Opposite hemispheres |
| Cerebral cortex | Grey matter, "executive suite" --> conscious mind |
| Frontal lobe | Motor cortex, speech |
| Parietal lobe | Somatosensory cortex, speech, taste, reading |
| Temporal lobe | Smell, hearing |
| Occipital lobe | Vision, visual association |
| 3 main structures of diencephalon (interbrain) | Thalamus, hypothalamus, and epithalamus |
| Thalamus | Relay station for incoming info |
| Hypothalamus | Autonomic control center, emotional response, body temperature regulation, regulate food intake, sleep-wake cycles, control endocrine system (pituitary gland) |
| Epithalamus | Pineal gland (sleep-wake cycle) |
| Brain stem | Programmed, automatic behaviors for survival. 3 regions: midbrain, pons, medulla oblongata |
| Midbrain | Vision, hearing, reflex |
| Pons | Breathing |
| Medulla oblongata | Heart rate, BP, breathing, swallowing, vomiting, coughing, sneezing |
| Cerebellum | Balance, equilibrium, timing of skeletal muscle activity |
| Protection of CNS | Meninges and CSF |
| Meninges | Connective tissue covering CNS structures. Dura mater (leathery outer), arachnoid mater (web-like middle), pia mater (surface of brain) |
| Meningitis | Inflammation of meninges; bacterial or viral infectiion |
| Cerebrospinal fluid (CSF) | Watery cushion to protect NS from trauma |
| Lumbar (spinal) tap | Test for infection, tumors, multiple sclerosis |
| Blood-brain barrier | Endothelial cells in capillaries prevent substances from crossing into brain |
| Can not pass the blood brain barrier | Urea, toxins, proteins, white blood cells, bacteria, most drugs |
| Can pass the blood brain barrier | Water, glucose, amino acids, gases, fat-soluble substances, some drugs: anestehtics, alcohol, nicotine |
| 4 major regions of the brain | Cerebral hemispheres, diencephalon, brain stem, cerebellum |
| Nervous control (communication) | Impulses across synapses |
| Hormonal control (communication) | Hormones in the blood |
| Nervous control (speed) | Very rapid (within a few miliseconds) |
| Nervous control (duration) | Short term and reversible |
| Nervous control (target pathway) | Specific (through nerves) to specific cells |
| Nervous control (action) | Causes glands to secrete or muscles to contract |
| Hormonal control (speed) | Relatively slow (over minutes, hours, or longer) |
| Hormonal control (duration) | Longer, lasting effects |
| Hormonal control (target pathway) | Hormones broadcast to target cells everywhere |
| Hormonal control (action) | Causes changes in metabolic activity |
| Basic Functions of Nervous system | Sensory input, integration, motor output |
| Sensory input | Gather information, detect and respond to changes in the external environment |
| Integration | Process and interpret sensory input |
| Motor output | Response by muscles and glands |
| Nervous system is divided into . . . | Central Nervous system (CNS) and Peripheral nervous stem (PNS) |
| CNS | Brain + spinal cord, integrative and control centers |
| PNS | Nerves (spinal nerves, cranial nerves) and communication lines between CNS and rest of body |
| Two divisions of PNS | Sensory (afferent) and motor (efferent) |
| Sensory (afferent) division | Sensory receptors --> CNS |
| Motor (efferent) division | CNS --> effectors (muscles+glands) |
| Which division is which? | Sensory - afferent and motor - efferent |
| Ventricles | Cavities containing the cerebrospinal fluid, which absorbs shocks and delivers nutritive substances |
| The brain contains ___ ___ ____ filled with CSF | 4 chambers (ventricles) |
| The CSF is produced in | The lateral ventricles (one in each hemisphere) |
| The CSF both | Protects and nourishes the brain+spinal cord\ |
| Inter-ventricular foramen | Opening where CSF drains from the lateral ventricle to the third ventricle |
| 3 layers of membranes (meninges) | Dura mater, arachnoid mater, pia mater |
| The CSF lies between | Two inner meningeal layers |
| The CSF is formed from the | Blood by clusters of capillaries (choroid plexuses) in the roof of each ventricle of the brain |
| CSF is continously | Circulated through the ventricles of the brain and the spinal cord before returning to the blood |
| Spinal Cord | A cylinder of nervous tissue extending from the baqse of the brain down the back, protected by the bones of the spinal column |
| The spinal cord . . . | Transmits signals to and from the brain+controls spinal reflexes. It can bypass the brain with sudden reflex actions |
| Peripheral nerves (sensory, motor, or mixed) all | Enter or leave the CNS, either at the spinal cord (spinal nerves) or the brain (cranial nerves) |
| Sensory nerves arise from | Sensory receptors |
| Sensory nerves . . . | Carry messages to CNS for processing and keeps CNS aware of external+internal environments |
| Sensory division includes | Sense organs such as ears, eyes, taste buds and internal receptors for monitoring thirst, hunger, and body position. |
| Motor nerves are | Comprised of 2 parts; somatic and autonomic NS |
| Motor nerves . . . | Carry impulses from the CNS to effectors: muscles and glands |
| Somatic NS | The neurons that carry impulses to voluntary (skeletal muscles) |
| Autonomic NS | The neurons that regulate visceral functions over which there is generally no conscious control. E.g: heart rate, pupil reflex |
| Interneurons | Connect sensory and motor neurons |
| Functional classification | Direction nerve impulse is traveling |
| Relay neurons | Also called association or interneurons. Located in the CBS and carry impulses from sensory to motor neurons (as in reflexes) |
| Structural classification | # of processes extending from cell body |
| Multipollar (structure) | 1 axon, several dendrites |
| Multipolar (rarity) | Most common (99%) |
| Multipolar (e.g.) | Motor neurons, interneurons |
| Bipolar (structure) | 1 axon, 1 dendrite |
| Bipolar (rarity) | Rare |
| Bipolar (e.g.) | Retina, nose, ear |
| Unipolar (structure) | 1 process |
| Unipolar (characteristic) | Short with 2 branches (sensory, CNS) |
| Unipolar (e.g.) | PNS, ganglia |
| Sensory input to receptors come via | Stimuli |
| Information about the effect of a response is provided by | Feedback mechanisms so that the system can be readjusted |
| Somatic NS | Voluntary; control skeletal muscles |
| Autonomic NS | Involuntary; regulate smooth muscles, cardiac, glands. Subdivisions: sympathetic+parasympathetic |
| Involuntary NS | Regulates involuntary visceral functions through reflexes. Most visceral effectors receive fibers from both branches of the ANS, the sympathetic and parasympathetic divisions. These two branches have broadly opposing actions on the organs they control. |
| Parasympathetic neurons release | ACh (neurotransmitter) which is rapidly deactivated at the synapse, and its effects localized |
| Sympathetic neurons release | Norepinephrine (neurotransmiter) which enters blood stream and is slowly deactivated |
| Sympathetic stimulation . . . | Generally has a wider ranging and longer lasting effects than parasympathetic stimulation |
| Parasympathetic includes nerves from | The brainstem and sacral (S) regions |
| Sympathetic division of the ANS includes nerves from | The thoracic (T) and lumbar (L) regions |
| Nervous tissue | Main cells and support cells |
| Neurons (nerve cells) | Transmit message |
| Cell body | Contains nucleus; metabolic center |
| Dendrite | Fiber that conveys message toward cell body |
| Axon | Conduct nerve impulses away from the cell body |
| Axon terminals | End of axon; contain neurotransmitters and release them |
| Synaptic cleft/synapse | Gap between neurons |
| Myelinated neurons | Speed needed : axons of neurons are sheathed by a lipid and protein-rich MYELIN |
| Myelinated neurons (characteristic) | Whitish, fatty material that covers nerve fibers to speed up nerve Whitish, fatty material that covers nerve fibers to speed up nerve impulses and is produced by oligendrocytes in the CNS and by Schwann cells in the PNS |
| Myelinated neurons (function) | Acts as an insulator, prevents flow of ions across the neuromembrane and increase speed at which nerve impulses travel because it forces the current to jump along the axon |
| Non-myelinated neurons | Relatively more common in the CNS where the distances signals travelled are shorter than in the PNS |
| Non-myelinated neurons (characteristic) | Instead of myelin, axons are enclosed in the cytoplasmic extensions of oligodendrocytes or Schwann cells |
| Non-myelinated neurons (function) | Speed of impulse conduction is slower than in myelinated neurons because the nerve impulse is propogated along the entire axon membrane |
| Supporting cells | Neuroglia |
| CNS (neuroglia) | Astrocytes, microglia, ependymal cells, oligodendrocytes |
| CNS (neuroglia) functions | Barrier between capillaries and neurons, protect neurons, immune/defense, line brain and spinal cord cavities, wrap nerve fibers, and produces myelin sheaths (covering) |
| PNS (neuroglia) | Schwann cells, satellite cells |
| PNS (neuroglia) functions | Surround large neurons, protect+cushion |
| Astrocytes (characteristic) | Most abundant supportive cells in nervous tissue. |
| Astrocytes (functions) | Anchor neurons to capillaries and support the blood-brain barrier by restricting the passage of certain substances. |
| Astrocytes (importance) | Important in the repair of the brain+spinal cord following injury |
| Microglial cells (characteristic) | The defense cells of the nervous tissue |
| Microglial cells (functions) | Antibodies are too large to cross the blood-brain barrier so the phagocytic microglia must be able to recognize and dispose of foreign material and debris |
| Ependymal cells (characteristic) | The epithelial cells lining the ventricles in the brain and the central canal of the spinal cord |
| Ependymal cells (functions) | The surfaces of these cuboidal cells are covered in cilia and microvili, which circulate and absorb CSF |
| Ependymal cells (more functions) | Specialized ependymal cells and capillaries together for the choroid plexuses, which produce the CSF |
| Oligondendrocytes | Produce insulating myelin sheaths around the axons of neurons in the CNS. A single one can extend up to 50 axons. |
| Schwann cells | May be myelinating or nonmyelinating |
| Nodes of Ranvier | Gaps between Schwann cells |
| Myelinating schwann cells | Wrap around axons in the PNS; providing insulating myelin sheaths (tight coil of wrapped membranes) |
| Non-myelinating schwann cells | Involved in the maintenance of the axons |
| Ganglia | Collections of nerve cell bodies (tissue mass) |
| Bundles of nerve fibers = | Tracts (CNS) or nerves (PNS) |
| White matter | Dense collections of myelinated fibers |
| Gray matter | Unmyelinated fibers and cell bodies |
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