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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.
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 that stimulates or inhibits contraction of smooth and cardiac muscle and stimulates glandular secretions
involuntary non-striated muscle, excited by external stimuli, which causes contraction
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.
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
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.
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.
CNS; covers capillaries and induce the blood-brain barrier, interact metabolically with neurons and modify the extracellular environment of neurons
form the epithelial lining of brain cavities and central canal of spinal cord, covers tufts of capillaries to form choroid plexuses
surrounds axons of peripheral nerve fibers, forming a neurilemmal sheath, also form myelin sheaths; PNS
a large number of ganglionic neurons activate many effector organs; causes a heightened sense of alertness due to stimulation of reticular activation system
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).
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
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
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
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.
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
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)
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
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
presynaptic neuron fires causes the postsynaptic neurons membrane potential to approach but not reach the threshold potential
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
simultaneous control of one neuron by two or more input neurons - sensory branch of the nervous system
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
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
Mechanical force, deforms cell membranes of sensory dendrites or deforms hair cells that activate sensory nerve endings
dissolved chemicals, chemical interactions affects ionic permeability of sensory cells
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
anterior portion of vascular tunic, supports lens through suspensory ligaments and decides thickness, secretes aqueous humor
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.
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.
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
known as cranial nerve 2, transmits visual information from the retina to the brain, does not regenerate after transection.
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
Spiral Organ of Corti
the organ in the inner ear found only in mammals that contains auditory sensory cells, or "hair cells."
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.
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
on papillae of tongue, includes tongue surface, taste pore, taste hair, taste bud - gustatory cell, supporting cell, sensory nerve fiber
General Sensory Receptors
Primary receptors = free nerve endings (taste, pain, touch)
Secondary receptors - specialized epithelial cells which form synapses with sensory neurons
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.
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.
It is an inhibitory neurotransmitter, is strongly associated with reward mechanisms in the brain. Drugs like cocaine, opium, heroin, and alcohol increase the levels.
acts like a brake to the excitatory neurotransmitters that lead to anxiety, and associated with epilepsy
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)
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.
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