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Veterinary A & P

Neurological System & Special Senses

Neurotransmitters The nervous system's chemical messengers.
neurons Nerve cells. Produce neurotransmitters. Stars of the nervous system: basic fundamental units of the system.
synapses a junction between two nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitter.
central nervous system System composed of the brain and spinal cord
peripheral nervous system consists of cordlike nerves that link the central nervous system with the rest of the body
neuroglia (glial cells) structurally and functionally support and protect neurons. Out number neurons 10 to 1. Not directly involved in the transmission of information or impulses through the nervous system. Support cells.
cell body (soma or perikaryon) is the bulbous, non-process portion of a neuron or other brain cell type, containing the cell nucleus.`
dendrites receives stimuli, or impulses, from other neurons and conduct this stimulation to the cell body. (afferent processes). Can be modified into sensory receptors that receive/sense: heat, cold, touch, pressure, stretch from inside or outside the body
Axons conduct nerve impulses away from the cell body toward another neuron or an effector cell (a cell that does something when stimulated, such as a muscle or gland cell). Efferent processes. Can be very long.
nerve fibers bundles of axons that make up cordlike nerves in the body
myelin Appears white. Nervous tissue containing many myelinated axons is often referred to as white matter.
Gray matter appearing darker: nervous tissue that is made up largely of neuron cell bodies
oligodendrocytes myelin sheath made of the cell membranes of specialized glial cells in the brain and spinal cord
schwann cells myelin sheath made of the cell membranes of specialized glial cells in the outside the brain and spinal cord (peripheral nervous system)
Nodes of Ranvier small gaps in the myelin sheath between adjacent glial cells enhance the speed of conduction of nerve impulses along the axon
How do basic communication and control functions differ between the nervous system and the endocrine system? the endocrine system uses chemical signaling hormones while the nervous system uses electrical signaling (neural impulses). The signal transmission of the nervous system is fast because neurons are interconnected, but the functions are more short-lived.
How are the functions of neurons and neuroglia different from each other? They outnumber neurons about 10 to 1 but are not directly involved in the transmission of information or impulses through the nervous system. They are important parts of the infrastructure necessary for the neurons to do their jobs.
Name the parts of a typical neuron They have three distinct parts, including a cell body, axon, and dendrites. These parts help them to send and receive chemical and electrical signals.
How are dendrites and axons different in structure and function? Dendrites receive electrochemical impulses from other neurons, and carry them inwards and towards the soma. Axons carry the impulses away from the soma. Most neurons have a lot of dendrites and only have one axon (can be long).
What is the difference between gray matter and white matter? Grey matter is distinguished from white matter in that it contains numerous cell bodies and relatively few myelinated axons. White matter contains fewer cell bodies and is composed chiefly of long-range myelinated axons.
What is the relationship between the myelin sheath and the nodes of ranvier? Myelinated axons have unmyelinated gaps between the numerous myelin sheaths surrounding the myelinated axon. Gaps are called Nodes of Ranvier. A change in voltage across the plasma membrane of an unmyelinated portion of axon is called an action potential.
What are the anatomic differences between the CNS and the PNS? The CNS consists of the brain and spinal cord, while the PNS includes all other nervous system tissue. All sensory receptors, sensory neurons and motor neurons are part of the PNS.
Which are afferent nerve fibers: motor nerve fibers or sensory nerve fibers? Which are efferent? Neurons that receive information from our sensory organs (eye, skin) and transmit input to the central nervous system: afferent neurons. Neurons that send impulses from the central nervous system to your limbs and organs: efferent neurons.
Define autonomic and somatic nervous systems. The Somatic Nervous System: part of the PNS that handles voluntary control of body movements. The Autonomic Nervous System is the part of the PNS that acts as an involuntary control system: controls visceral functions.
Sensory vs Motor Sensory neurons carry signals from the outer parts of your body (periphery) into the CNS. Motor neurons carry signals from the CNS to the outer parts (muscles, skin, glands) of your body.
sensory nerve fibers usually called afferent nerve fibers
motor nerve fibers usually called efferent nerve fibers
somatic nervous system Part of the PNS. Major functions: include voluntary movement of the muscles and organs and reflex movements. In the process of voluntary movement, sensory neurons carry impulses to the brain and the spinal cord.
autonomic nervous system A control system that acts largely unconsciously and regulates bodily functions such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal.
Resting State of a neuron Membrane potential of a neuron. (about -70 mV (mV=millivolt) - Meaning: the inside of the neuron is 70 mV less than the outside. At rest, there are relatively more sodium ions outside the neuron and more potassium ions inside that neuron.
Sodium-potassium pump Found in many plasma membranes. Powered by ATP, it moves sodium and potassium ions in opposite directions, each against its concentration gradient. A single cycle of the pump = three sodium ions extruded and two potassium ions imported
resting membrane potential The resting membrane potential is determined by the uneven distribution of ions (charged particles) between the inside and the outside of the cell, and by the different permeability of the membrane to different types of ions. Potassium: Sodium:
depolarization Depolarization: change within a cell during which the cell undergoes a shift in electric charge distribution. Result: less negative charge inside the cell. It is essential to the function of and communication between cells
action potential Change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell.
repolarization refers to the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential which has changed the membrane potential to a positive value.
threshold stimulus The weakest stimulus that could generate an action potential in a neuron.
wave of depolarization Occurs in the four chambers of the heart: both atria and then both ventricles. The sinoatrial (SA) node on the wall of the right atrium initiates depolarization in the right and left atria, causing contraction: symbolized by the P wave on an ECG.
conduction of the action potential the passive spread of depolarization to the adjacent distal region of membrane slightly depolarizes the new region, causing opening of a few voltage-gated Na+ channels and an increase in Na+ influx. At its peak.
nerve impulse a signal transmitted along a nerve fiber. It consists of a wave of electrical depolarization that reverses the potential difference across the nerve cell membranes.
all-or-nothing-principle States that the strength of a response of a nerve cell or muscle fiber is not dependent upon the strength of the stimulus. If a stimulus is above a certain threshold, a nerve or muscle fiber will fire.
refractory period a period immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation.
saltatory conduction (from the Latin saltare, to hop or leap) is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.
synaptic transmission Biological process by which a neuron communicates with a target cell across a synapse. Chemical synaptic transmission involves release of a neurotransmitter from the presynaptic neuron, and neurotransmitter binding to specific postsynaptic receptors.
synaptic cleft (synaptic gap) the space between neurons at a nerve synapse across which a nerve impulse is transmitted by a neurotransmitter
presynaptic neuron a neuron (nerve cell) that fires the neurotransmitter as a result of an action potential entering its axon terminal. In both the central and peripheral nervous systems in mammals, presynaptic terminals operate mostly in the same way.
neurotransmitter a chemical substance that is released at the end of a nerve fiber by the arrival of a nerve impulse and, by diffusing across the synapse or junction, causes the transfer of the impulse to another nerve fiber, a muscle fiber, or some other structure.
postsynaptic neuron a neuron (nerve cell) that receives the neurotransmitter after it has crossed the synapse. May experience an action potential if the neurotransmitter is strong enough. Postsynaptic neurons work through temporal summation and spatial summation.
terminal bouton the specialized presynaptic terminal at the end of an axon. Contain necessary organelles, proteins and molecules needed to transmit chemical/electrical information to the postsynaptic cell.
synaptic end bulb (synaptic knob) Contains synaptic vesicles which are filled with a neurotransmitter substance. When a nerve impulse travels down the axon and reaches the end bulb the neurotransmitter is released into a small space (synaptic cleft)
During depolarization, what ion channels open and what ion moves? Where does it move? After depolarization, it undergoes one final change in internal charge. After depolarization, the open voltage-gated sodium ion channels close again. The increased positive charge within the cell causes the potassium channels to open.
During repolarization, what ion channels open and what ion moves? Where does it move? Repolarization: when the K+ channels open and K+ moves out of the axon, creating a change in polarity between the outside and inside of the cell. The impulse travels down the axon in one direction, to the axon terminal where it signals other neurons.
What normally maintains the resting membrane potential of a neuron during the resting state? Sodium-potassium pumps move two potassium ions inside the cell as three sodium ions are pumped out to maintain the negatively-charged membrane inside the cell; this helps maintain the resting potential.
What is threshold? What role does threshold play in the all-or-none principle? The all-or-none law is a principle that states that the strength of a response of a nerve cell or muscle fiber is not dependent upon the strength of the stimulus. If a stimulus is above a certain threshold, a nerve or muscle fiber will fire.
What is the difference between the absolute and the relative refractory periods? Absolute: the time when a second action potential cannot be initiated, no matter how large the stimulus. Relative: the interval immediately after the Absolute Refractory Period when initiation of a second action potential is inhibited but not impossible.
Explain why waves of depolarization are conducted faster in myelinated axons than in unmyelinated ones., The myelin sheath prevents sodium ions from flowing across the neuronal cell membrane. In this way, depolarization continues from one cell to the next.
receptor proteins protein molecules inside the target cell or on its surface that receive a chemical signal. Chemical signals are released by signaling cells in the form of small, usually volatile or soluble molecules
excitatory neurotransmitters types of neurotransmitters have excitatory effects on the neuron. They increase the likelihood that the neuron will fire an action potential. Some of the major ones include epinephrine and norepinephrine.
inhibitory neurotransmitters types of neurotransmitters have inhibitory effects on the neuron; they decrease the likelihood that the neuron will fire an action potential. Some of the major ones include serotonin and gamma-aminobutyric acid (GABA).
acetylcholine A neurotransmitter which is a chemical released by a nerve cell or neuron. Acetylcholine causes muscles to contract, activates pain responses, and regulates endocrine and REM sleep functions. Deficiencies can lead to muscle weakness.
acetylcholinesterase he primary enzyme responsible for the hydrolytic metabolism of the neurotransmitter acetylcholine (ACh) into choline and acetate.
monoamine oxidase (MAO) a type of enzyme that helps neurons fire throughout your body. Formed in your liver and cleans up neurotransmitters in your brain once they've done their jobs. It also cleans out tyramine, a chemical that helps regulate blood pressure.
catechol-o-methyltransferase an enzyme that is involved in the degradation of catecholamine neurotransmitters like norepinephrine
What role do the synaptic cleft, presynaptic neuron, neurotransmitter, and post synaptic neuron play in the continuation of a depolarization wave from one nerve to another? Depolarization waves causes the vesicles to dump neurotransmitters into the synaptic cleft. Neurotransmitter diffuse across the synaptic cleft toward the postsynaptic membrane. Receptors on the postsynaptic membrane bind the neurotransmitters.
What is the functional relationship between a neurotransmitter and a receptor? Will any neurotransmitter stimulate any receptor? Neurotransmitter molecules released by the synaptic knob bind with receptors and trigger a change in the postsynaptic cell. If not a match they will not bind. No change will occur.
What is the difference between an excitatory and an inhibitory neurotransmitter? Excitatory have an excitatory effect on the postsynaptic membrane when they combine with their specific receptors. Inhibitory tend to make the inside of the cell more negative instead of positive: move the charge farther away from threshold.
How is acetylcholine different from acetylcholinesterase? Acetylcholine: neurotransmitter broken down quickly by acetylcholinesterase found on the postsynaptic membrane.
What are catecholamines? Catecholamines are the neurotransmitters norepinephrine, epinephrine, and dopamine.
What are GABA and glycine? Gamma-aminobutyric acid (GABA) and glycine are inhibitory neurotransmitters. GABA is found in the brain, and glycine is found in the spinal cord.
Gray Matter (of the CNS) Contains most of the neuron cell bodies, and appears a dark brownish-gray color. "Thinking" part of the CNS.
White Matter Contains most of the myelinated nerve fibers and appears white because of all the myelin. The "wiring" that connects the various components of the brain.
Cerebrum Made up of gray matter in the cerebral cortex (outermost layer) and white matter beneath the cortex, including the corpus callosum (a set of fibers that connect the two halves of the cerebral cortex.) (learning, reason, intelligence)(largest portion)
Cerebellum Allows for coordinated movement, balance, posture, and complex reflexes.
Diencephalon (more primitive) (Thalamus, Hypothalamus, Pituitary) The between brain. Serves as a nervous system passageway between the primitive brainstem and the cerebrum.
Brainstem (more primitive) (Midbrain, Pons and Medulla) The connection between the rest of the brain and the the spinal cord.
gyri is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (depressions or furrows; sulcus). Gyri and sulci create the folded appearance of the brain in humans and other mammals
lobes each of the parts of the cerebrum of the brain. Right Hemisphere and Left Hemisphere (cerebral hemispheres) Frontal lobe, Parietal Lobe, Occipital Lobe, Temporal Lobe, Cerebellum, brain stem (Midbrain, Pons and Medulla)
sulci (fissures) a groove or furrow, especially one on the surface of the brain.
longitudinal fissure The median longitudinal fissure, or interhemispheric fissure is the deep groove that separates the two hemispheres of the vertebrate brain.
Thalamus Acts as a relay station for regulating sensory inputs to the cerebrum
Hypothalamus Is an interface between the nervous system and the endocrine system
Pituitary Is the endocrine "master gland" that regulates production and release of hormones throughout the body.
What part of the brain is responsible for conscious thought and perception of sensations? Cerebrum. Specifically: cerebral cortex
What are the correct names for the bumps and fissures that make the cerebral cortex appear wrinkled? The folds, called gyri (plural of gyrus), are separated by deep grooves called fissures, and the more shallow grooves are called sulci (plural of sulcus).
What part of the brain is critical for coordination, posture, and fine motor control? How does this part of the brain accomplish these responsibilities? The cerebellum is located behind the brain stem. The frontal lobe controls movement but the cerebellum “fine-tunes” this movement. This area of the brain is responsible for fine motor movement, balance, and the brain's ability to determine limb position.
What part of the brain serves as a relay station for impulses going to and from the cerebrum? It serves as a relay station for impulses traveling to and from the spinal cord, brain stem, cerebellum and cerebrum. It has an important function in directing sensory input to the appropriate place in the cerebral cortex.
Which part of the brain controls many autonomic functions related to cardiovascular, respiratory, and gastrointestinal functions? Brainstem. But the medulla oblongata control many functions of the digestive, cardiovascular, pulmonary, reproductive and urinary systems. The vagus nerve (both sensory and motor fibers) supplies sensory input to these centers through its afferent fibers.
Meninges the three membranes (the dura mater, arachnoid, and pia mater) that line the skull and vertebral canal and enclose the brain and spinal cord.
cerebrospinal fluid A clear, colorless body fluid found in the brain and spinal cord. It is produced by specialized ependymal cells in the choroid plexuses of the ventricles of the brain, and absorbed in the arachnoid granulations.
blood-brain barrier is a highly selective semipermeable border that separates the circulating blood from the brain and extracellular fluid in the central nervous system (CNS).
fenestrations Found in some tissues where there is extensive molecular exchange with the blood such as the small intestine, endocrine glands and kidneys. They are pores that allow larger molecules through. More permeable than continuous capillaries
myelogram a diagnostic imaging test generally done by a radiologist. It uses a contrast dye and X-rays or computed tomography (CT) to look for problems in the spinal canal. Problems can develop in the spinal cord, nerve roots, and other tissues.
What are the protective membranes that surround, support, and protect the CNS? Meninges (from the Greek word for membrane). The outermost layer is the dura mater (Latin for “hard mother”). As the Latin name suggests, the primary function for this thick layer is to protect the brain and spinal cord.
What is the fluid called that bathes, cushions, and aids in transport of materials to and from the CNS? Cerebrospinal fluid (CSF) is a clear, colorless body fluid found in the brain and spinal cord.
What helps keep dangerous poisons and certain drugs from leaving the blood and entering the brain? Describe this structure. BBB is semipermeable; allows some materials to cross but prevents others. In the brain, endothelial cells fit tightly together and substances cannot pass out of the bloodstream. Molecules like glucose are transported out of the blood by special methods.
What are the 12 cranial nerves? Which nerves are motor, which are sensory, and which are both? Olfactory: s, Optic: s, Oculomotor: m, Trochlear: m, Trigeminal: both s and m, Abducent: m, Facial: both s and motor, Vestibulocochlear: sensory, Glossopharyngeal: both sensory and motor, Vagus: both sensory and motor, Accessory: motor, Hypoglossal: motor
spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. It encloses the central canal of the spinal cord, which contains cerebrospinal fluid.
dorsal nerve roots one of two "roots" which emerge from the spinal cord. It emerges directly from the spinal cord, and travels to the dorsal root ganglion. Transmits sensory information, forming the afferent sensory root of a spinal nerve.
ventral nerve roots or anterior root is the efferent motor root of a spinal nerve. At its distal end, the ventral root joins with the dorsal root to form a mixed spinal nerve.
dorsal horns a longitudinal subdivision of gray matter in the dorsal part of each lateral half of the spinal cord that receives terminals from some afferent fibers of the dorsal roots of the spinal nerves.
ventral horns contains the cell bodies of motor neurons that send axons via the ventral roots of the spinal nerves to terminate on striated muscles. These pathways are also referred to as the cortico-spinal tracts.
sympathetic nervous system (SNS) is part of the autonomic nervous system (ANS). This nervous system activates what is often termed the fight or flight response.
parasympathetic nervous system (PSNS) is one of three divisions of the autonomic nervous system. It conserves energy as it slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles in the gastrointestinal tract. (Rest and Digest)
thoracolumbar system sympathetic division of the autonomic nervous system influences the various organ systems of the body through connections emerging from the thoracic and upper lumbar spinal cord.
cranial-sacral system consists of the membranes and fluid that surround and protect the brain and spinal cord, as well as the attached bones. Because it enhances the body's natural healing processes CST is increasingly used as a preventive health measure.
autonomic ganglion is a cluster of nerve cell bodies (a ganglion) in the autonomic nervous system. The two types are sympathetic ganglion and parasympathetic ganglion.
preganglionic neuron originates in the brainstem or the spinal cord, and the second set, called ganglion cells or postganglionic neurons, lies outside the central nervous system in collections of nerve cells called autonomic ganglia
postganglionic neuron These neurons are directly responsible for changes in the activity of the target organ via biochemical modulation and neurotransmitter release.
sympathetic ganglion chain The bilaterally symmetric sympathetic chain ganglia, also called the paravertebral ganglia, are located just ventral and lateral to the spinal cord. The chain extends from the upper neck down to the coccyx, forming the unpaired coccygeal ganglion.
cranial nerve nucleus a collection of neurons (gray matter) in the brain stem that is associated with one or more cranial nerves. Axons carrying information to and from the cranial nerves form a synapse first at these nuclei.
sympathetic nervous system (nerve locations) thoracolumbar system
parasympathetic nervous system (nerve locations) emerges from the brain and the sacral vertebral regions and therefore is called the cranial-sacral system
cholinergic neurons a nerve cell which mainly uses the neurotransmitter acetylcholine (ACh) to send its messages. Many neurological systems are cholinergic.
cholinergic receptors are receptors on the surface of cells that get activated when they bind a type of neurotransmitter called acetylcholine. There are two types of cholinergic receptors: nicotinic and muscarinic receptors - named after the drugs that work on them.
nicotinic receptors are receptor polypeptides that respond to the neurotransmitter acetylcholine. Nicotinic receptors also respond to drugs as the agonist nicotine. These receptors are considered cholinergic receptors, since they respond to acetylcholine.
muscarinic receptors are acetylcholine receptors that form G protein-coupled receptor complexes in the cell membranes of certain neurons and other cells. They are so named because they are more sensitive to muscarine than to nicotine.
somatic reflexes are one of the two types of reflex arcs, and specifically involve the skeletal muscles. They are unlearned muscle reflexes that are mediated by the brainstem and spinal cord.
autonomic reflexes are unconscious motor reflexes relayed from the organs and glands to the CNS through visceral afferent signaling.
reflex arc In vertebrates, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This allows for faster reflex actions to occur by activating spinal motor neurons without the delay of routing signals through the brain.
sensory neuron nerve cells in the nervous system responsible for converting external stimuli from an organism's environment to internal electrical impulses. Some of these neurons respond to tactile stimuli and can activate motor neurons to achieve muscle contraction.
stretch reflex a muscle contraction in response to stretching within the muscle. It is a monosynaptic reflex which provides automatic regulation of skeletal muscle length. When a muscle lengthens, the muscle spindle is stretched and its nerve activity increases.
withdrawal reflex is a spinal reflex intended to protect the body from damaging stimuli. It is a polysynaptic reflex, causing stimulation of sensory, association, and motor neurons
extensor reflex is a reflex in which the contralateral limb compensates for loss of support when the ipsilateral limb withdraws from painful stimulus in a withdrawal reflex.
muscle spindle are stretch receptors within the body of a muscle that primarily detect changes in the length of the muscle. They convey length information to the central nervous system via afferent nerve fibers.
palpebral reflex elicited by touching either the periocular skin (palpebral) or the cornea (corneal). This reflex is important to protecting the eye, and interference with it (facial paralysis, trigeminal palsy, local anesthesia) often results in severe ocular damage.
pupillary light reflex (PLR) Normally when a light is shone into one eye it will cause both pupils to constrict.
Created by: Raevyn1



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