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107 terms

BIOL 2160 Test 3 Part 1

Nervous system
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Central Nervous System
Brain and Spinal Cord
Nuclei
Grouping of neuron cell bodes within CNS
Tracts
Grouping of Nerve fibers that interconnect regions of CNS
Peripheral Nervous System
Nerves, ganglia, and nerve plexuses
Cranial Nerves
nerves that emerge directly from the brain; twelve pairs of cranial nerves. Only the first and the second pair emerge from the cerebrum; the remaining ten pairs emerge from the brainstem.
Spinal Nerves
emerge from segments of the spinal cord; carries motor, sensory, and autonomic signals between the spinal cord and the body. Humans have 31 left-right pairs of spinal nerves, The spinal nerves are part of the peripheral nervous system (PNS).
Nerve
cable like collection of many axons, may be mixed with sensory and motor fibers
Ganglia
grouping of neuron cells located outside of CNS
Sensory Neurons
afferent neuron, neurons that transmits impulses from a sensory receptor in the CNS
Motor Neurons
efferent neuron, neuron that transmits impulse from the CNS to effector organ
Effector Organs
a muscle or gland which has an effect when it is turned on by a motor neurone
Somatic Motor
Nerve that stimulates contraction of skeletal muscles
Autonomic Motor
nerve that stimulates or inhibits contraction of smooth and cardiac muscle and stimulates glandular secretions
Smooth Muscles
involuntary non-striated muscle, excited by external stimuli, which causes contraction
Cardiac Muscles
involuntary striated muscle found in the walls and histological foundation of the heart, specifically the myocardium; Coordinated contractions of cardiac muscle cells in the heart propel blood out of the atria and ventricles to the blood vessels of the left/body/systemic and right/lungs/pulmonary circulatory systems.
Sympathetic Branch
one of the three parts of the autonomic nervous system, aids in the control of most of the body's internal organs, Stress—as in the flight-or-fight response—is thought to counteract the parasympathetic system
Parasympathetic Branch
responsible for stimulation of "rest-and-digest" activities that occur when the body is at rest, including sexual arousal, salivation, lacrimation (tears), urination, digestion, and defecation.
Guillain - Barre Syndrome
a disorder affecting the peripheral nervous system. Ascending paralysis, weakness beginning in the feet and hands and migrating towards the trunk, is the most typical symptom, and some subtypes cause change in sensation or pain as well as dysfunction of the autonomic nervous system.
Ganglionic Gliocytes
It gives support to the cell bodies in the preipheral nervous system, or PNS.
Multiple Sclerosis
an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms.
Astrocytes
CNS; covers capillaries and induce the blood-brain barrier, interact metabolically with neurons and modify the extracellular environment of neurons
Microglia
CNS, phagocytose pathogens and cellular debris in CNS
Ependyma
form the epithelial lining of brain cavities and central canal of spinal cord, covers tufts of capillaries to form choroid plexuses
Schwann Cells
surrounds axons of peripheral nerve fibers, forming a neurilemmal sheath, also form myelin sheaths; PNS
Satellite Cells
support functions of neurons within sensory and autonomic ganglia; PNS
Oligodendrocytes
form myelin sheaths around central axons, producing white matter of CNS; CNS
Mass Activation
a large number of ganglionic neurons activate many effector organs; causes a heightened sense of alertness due to stimulation of reticular activation system
Splanchnic Nerves
aired nerves that contribute to the innervation of the viscera, carrying fibers of the autonomic nervous system (visceral efferent fibers) as well as sensory fibers from the organs (visceral afferent fibers).
Abdominal Ganglia
control movements of abdominal muscles.
Divisions of Automatic Nervous System
Parasympathetic (craniosacral) Division
Adrenergic and cholinergic synaptic transmission
Other autonomic neurotransmittors
Organs with dual innervation
Neurotransmitters in Automatic Nervous System
the chemicals which allow the transmission of signals from one neuron to the next across synapses
Synapses en Passant
Some synaptic junctions appear partway along an axon as it extends
Action Potential
short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory, "nerve impulses" or "spikes"
Refractory Period of Cardiac Muscles
Heart contracts as syncytium & thus can sustain force
Its AP lasts about 250 msec
Has a refractory period almost as long as AP
Cannot be stimulated to contract again until has relaxed
Components of Total Refractory Period
Absolute Refractory Period - due to inactivated Na channels
Relative Refractory Period - due to continued outward K diffusion
Saltatory Conduction
propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials without needing to increase the diameter of an axon.
2 Types of Nerve Fibers
Myelinated Fibers - rapid conduction velocity; Control rapid body movements by skeletal muscles; Transmit sensory signals from receptors to CNS


Unmyelinated fibers - slower conduction velocity
Control subconscious activities via ANS
Function of Myelin Sheath
to increase the speed at which impulses propagate along the myelinated fiber, provides a track along which regrowth can occur
All or None Law in Nerve Fibers
principle that the strength by which a nerve or muscle fiber responds to a stimulus is not dependent on the strength of the stimulus. If the stimulus is any strength above threshold, the nerve or muscle fiber will give a complete response or otherwise no response at all; Henry Pickering Bowditch in 1871
Speed of Conduction Velocities
...
Summation
frequency summation is the method of signal transduction between neurons, which determines whether or not an action potential will be triggered by the summation of postsynaptic potentials.
Neural physiology
the additive effects of graded nerve potentials
Muscle physiology
The additive effects of contractions of different muscle fibers
Types of Summation
Spatial summation and temporal summation
Spatial Summation
recruitment of variable numbers of nerve fibers in a nerve
1. Minimal stimulus or threshold stimulus - voltage at which only one nerve fiber stimulated to fire
2. Maximal stimulus - voltage all the nerve fibers in the nerve fire
Temporal Summation
frequency modulation - variation in number of action potentials sent along a nerve fiber per second: (frequency is limited by the refractory period of the nerve fiber)
Neuronal Junctions
Electrical synapses, synaptic transmission, neuromuscular junction
Electrical Synapses
Cardiac muscle
Some smooth muscles
Some neurons in the brain
Synaptic Transmission
1. Action Potentials reach axon terminals
2. Voltage gated Ca channels open
3. Ca in cytoplasm activates proteins, leading to fusion of vesicles with plasma membrane
4. Pore forms in fused vesicle and exocytosis releases neurotransmitter
Neuromuscular Junction
Motor Unit
Physiological anatomy
Details of transmission
Effect of drugs on the neuromuscular junction
Effect of ions on the neuromuscular junction
Morphology of Gap Junctions
plasma membrane of one cell, plasma membrane of connecting cell, connexin proteins forming gap junctions, surrounding cytoplasm
Skeletal Muscle Neuromuscular Junction
terminal bouton of axon, mitochondria, synaptic vesicles, synaptic cleft, post synaptic cell/skeletal muscle
Excitatory Postsynaptic Potential
a temporary depolarization of postsynaptic membrane potential caused by the flow of positively charged ions into the postsynaptic cell as a result of opening of ligand-sensitive channels.
Inhibitory Postsynaptic Potential
result from the flow of negative ions into the cell or positive ions out of the cell.
Drugs and Effects on Neurol Control of Skeletal Muscles
Botulinium toxin - stops release of acetylcholine (ACH)
Curare - Prevents interaction of ACH with post synaptic receptor protein
Saxitoxin/Tetrodotoxin - blocks voltage gated Na channels
Nerve gas/Neostigmine - stops acetylcholinesterase in postsynaptic membrane
Strychnine - prevents IPSPs in spinal chord
Basic Neuronal Pools
Accumulations of neurons making up the numerous anatomical regions of the CNS
Area of Stimulation
sphere of influence upon neurons with which the neuron synapses
Discharge Zone
Presynaptic neuron causes the postsynaptic neuron to fire
Facilitated Zone
presynaptic neuron fires causes the postsynaptic neurons membrane potential to approach but not reach the threshold potential
Circuits in Neuronal Pools
One oncoming/outgoing, Diverging, Converging, inhibitory
One oncoming - outgoing Circuit
Relay
Diverging/ Amplifying Circuit
1 →many neurons
Amplifying - CNS control of skeletal muscles
Diverging circuit → multiple tracts
Sensory information in dorsal columns of spinal cord to:
Cerebellum and Thalamus and cerebral cortex
Converging Circuit
simultaneous control of one neuron by two or more input neurons - sensory branch of the nervous system
Inhibitory Circuit
- shuts off one pathway while opening another
Sensory Receptors
detect intensity gradients of such sensory stimuli as touch, sound, light, smell, taste, cold and warmth; produce generator (= receptor) potentials in proportion to the strength of the environmental stimulus and send pulse encoded information to the CNS for processing
Receptor Potential
produced by sensory transduction., form of graded potential, a depolarizing event resulting from inward current flow. The influx of current will often bring the membrane potential of the sensory receptor towards the threshold for triggering an action potential.
Types of Sensory Receptors
Mechanoreceptors
Thermoreceptors
Nociceptors
Electromagnetic receptors
Chemoreceptors
Mechanoreceptors
Mechanical force, deforms cell membranes of sensory dendrites or deforms hair cells that activate sensory nerve endings
Pain Receptors
Tissue damage, damaged tissues release chemicals that excite sensory endings
Chemoreceptors
dissolved chemicals, chemical interactions affects ionic permeability of sensory cells
Photoreceptors
light, photochemical reactions affect ionic permeability of receptor cells
Cutaneous Receptors
Free Nerve Endings - light touch, hot, cold, pain
Merkel's Disc - sustained touch and pressure
Ruffini's Corpuscles - sustained pressure
Meissner's Corpuscles - change in texture, slow vibrations
Pacinian Corpuscles - deep pressure, fast vibrations
Fibrous Tunic
Outer eyeball, gives shape to eyeball
Sclera
white of eye, supports and protects eyeball
Cornea
inside surface of eyeball, transmits and refracts light
Vascular Tunic
uvea, middle layer of eyeball, supplies blood, prevents reflection
Choroid
middle layer of posterior of eyeball, supplies blood to eyeball
Ciliary Body
anterior portion of vascular tunic, supports lens through suspensory ligaments and decides thickness, secretes aqueous humor
Iris
continous to ciliary body, regulates diameter of pupil, and amount of light that enters
Internal Tunic
inner layer of eyeball, provides location and support for robs and cones
Retina
principal portion of internal tunic, photoreception, transmits impulses
Lens
between posterior and vitreous chamber, refracts light and focuses on fovea centralis
Emmetropia
normal vision, rays focus on retina, no correction needed
Myopia
nearsightedness, rays focus on front of retina, concave lens
Hyperopia
farsightedness, rays focus behind retina, convex lens
Astigmatism
rays do not focus, uneven lens
Pupil Reflex
reflex that controls the diameter of the pupil, in response to the intensity (luminance) of light that falls on the retina of the eye, thereby assisting in adaptation to various levels of darkness and light, in addition to retinal sensitivity.
Rod Cell
photoreceptor cells in the retina of the eye that can function in less intense light, approximately 125 million rod cells in the human retina, rod cells are almost entirely responsible for night vision.
Cone Cell
photoreceptor cells in the retina of the eye that are responsible for color vision; they function best in relatively bright light, six million in the human eye was found
Optic Nerve
known as cranial nerve 2, transmits visual information from the retina to the brain, does not regenerate after transection.
Tympanic Membrane
ear drum, cone-shaped membrane that separates the external ear from the middle ear in humans and other tetrapods; transmit sound from the air to the ossicles inside the middle ear
Ossicular System
Malleus
Incus
Stapes → Oval window
Spiral Organ of Corti
the organ in the inner ear found only in mammals that contains auditory sensory cells, or "hair cells."
Vestibular Apparatus
contributes to balance in most mammals and to the sense of spatial orientation, is the sensory system that provides the leading contribution about movement and sense of balance.
Ear Anatomy
Outer Ear - helix, auricle, external auditory meatus, earlobe
Middle Ear - auditory ossicles, tympanic membrane, semicircular canals
Inner Ear - Semicircular canals, facial nerve, vestibular nerve, cochlear nerve, cochlea, temporal bone, round window, cavity cavitiy, auditory tube
Primary Sensations of Taste
Sour - H channels
Sweet - Na Channels
Sweet and meaty - sugars and glutamate via g-protein receptors
Bitter - quinine vi g protein receptors
Taste Buds
on papillae of tongue, includes tongue surface, taste pore, taste hair, taste bud - gustatory cell, supporting cell, sensory nerve fiber
Olfactory Cells
bipolar nerve cells derived initially from the CNS,
Primary Sensations of Smell
Camphoraceous
Musky
Floral
Pepperminty
Ethereal
Pungent
Putrid
General Sensory Receptors
Primary receptors = free nerve endings (taste, pain, touch)
Secondary receptors - specialized epithelial cells which form synapses with sensory neurons
Acetylcholine
neurotransmitter responsible for much of the stimulation of muscles, including the muscles of the gastro-intestinal system, has a part in scheduling REM (dream) sleep.
Norepinephrine
neurotransmitter strongly associated with bringing our nervous systems into "high alert." It is prevalent in the sympathetic nervous system, and it increases our heart rate and our blood pressure. It is also important for forming memories.
Dopamine
It is an inhibitory neurotransmitter, is strongly associated with reward mechanisms in the brain. Drugs like cocaine, opium, heroin, and alcohol increase the levels.
GABA
acts like a brake to the excitatory neurotransmitters that lead to anxiety, and associated with epilepsy
Glutamate
most common neurotransmitter in the central nervous system, actually toxic to neurons, and an excess will kill them. Sometimes brain damage or a stroke will lead to an excess and end with many more brain cells dying than from the original trauma. (ALS disease)
Serotonin
inhibitory neurotransmitter that has been found to be intimately involved in emotion and mood. Too little has been shown to lead to depression, tied to migraines, irritable bowel syndrome, and fibromyalgia.
Endorphin
short for "endogenous morphine.", Inhibitory, it is involved in pain reduction and pleasure, drug associated (heroin)