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The Nervous System (H) (The Nervous System (H) (Cranial Nerves (H9) (XII.)…
The Nervous System (H)
The Nervous System (H)
Neurotransmitters &Their Roles in Synaptic Transmission (H5)
Synapes
Chemical
Axon terminal, receptor region. More abundant, slower, more selective
Electrical
Least common, corresponds to gap junctions
Postsynaptic potentials
Inhibitory
Push the neuron further from the threshold, makes an action potential harder to achieve
Excitatory
Push the neurons closer to threshold and make an action potential more likely
Neurotransmitter (examples)
Norepinephrine
Triggers flight or fight
Dopamine
Influences emotion and attention
Acetycholine
Neuromuscular junction
Seratonin
Mainly inhibitory, role in regulating mood, appetite, circadian rhythm, and sleep
Summation (Postsynaptic Potentials)
Spatial
Multiple input
Results from the buildup of neurotransmitters released by several presynaptic end bulbs
Temporal
A single imput
Response to stimuli that occur at the same location in the membrane of the postsynaptic cell but at different times
Presynaptic
Converts an electrical signal (nerve impulse) into a chemical signal (released neurotransmitter)
Postsynaptic
Receives change in the membrane potential. Receives the chemical signal and in turn may generate an electrical signal
Reflexes (H11)
Specific reflexes used in clinical assessments
Abdominal
Involves contraction of the muscles that compress the abdominal wall in response to stroking the side of the abdomen
Patellar Reflex
Involves extension of the knee by contraction of the quadriceps femoris muscle in response to tapping the patellar ligament
Babinski
Reflex results in gentle stroking of the lateral outer margin of the sole.
Achilles
Involves plantar flexion of the foot by contraction of the gastrocnemius and soleus muscles in response to tapping the calcaneal tendon.
Intersegmental reflex
Nerve impulses from one sensory neuron ascend and descend in the spinal cord and active inter neurons in several segments and the spinal cord
Cross extensor
Help maintain balance
Flexor Reflex
Causes withdrawal of a part of the body in response to a painful stimulus
A fast, involuntary, unplanned sequence of actions that occurs in response to a particular stimulus
Stretch flex
Causes contraction of a skeletal muscle in response to stretching of the muscle (patellar or knee jerk)
Spinal reflex
Integration takes place in the spinal cord gray matter
Division, origin, and function of component parts of the brain (H7)
Hemispheric Specialization
Corpus Callosum
allows communication between the two hemispheres of the brain, responsible for neural messages between the right and left sides
Left Hemisphere
Controls movement in the right side of the body, speech, receives sensations from right side of the body, comprehension of language, reading and writing, analytical thinking, logical reasoning mathematics
Right Hemisphere
Controls movement in the left side of the body, creativity, Receives sensations from left side of the body, recognition of faces, recognition of patterns, musical ability, spatial ability, emotional detection and expression, appreciation of art
Lobes of cerebral cortex
Frontal Lobe
central sulcus seperates the frontal lobe from the parietal lobe
associated with reasoning, planning, emotion and problem solving
precentral gyrus, located immediately anterior to central sulcus
Insula
Within the lateral cerebral sulcus, deep to the parietal frontal, and temporal bones, cannot be seen at the surface
Temporal Lobe
lateral cerebral sulcus the frontal lobe from the temporal lobe
associated with perception and recognition auditory stimuli, memory and speech
Occipital Lobe
parieto-occipital sulcus, seperates parietal lobe from occipital lobe
associated with visual processing
Parietal Lobe
associated with movement, orientation, recognition, perception of stimuli
postcentral gyrus, located posterior to central sulcus, contains the primary somatosensory area of the cerebral cortex
Developmental regions
Thalamus
Collection of nuclei that relay information, all sensory information except smell, passes through the thalamus, before processing by the cortex
Brainstem
Connects the brain to the spinal cord, consists of the medulla oblongata, pons, and midbrain
Cerebellum
"little brain", largely responsible for comparing information from the cerebrum with sensory feedback from the periphery through spinal cord
Diencephalon
Consists of thalamus, hypothalamus, and epithalamus
Hypothalumus
Collection of nuclei that are largely involved in regulating homeostasis
Cerebrum
Largest part of the brain, divided into two hemispheres, memory, emotion, and consciousness are the result of cerebral function
Limbic system
Amygdala
Composed of several groups of neurons located close to the tail of the caudate nucleus
Denate gyrus
Lies between the hippocampus and parahippocampus
governs emotional aspects of behavior
Olfactory bulbs
Flattened bodies of the olfactory pathway that rest on the cribriform plate
Mammillary bodies
Two round masses close to the midline near the cerebral peduncles
Septal Nuclei
Located within the septal area formed by the regions under the corpus callosum and the paraterminal gyrus
Limbic lobe
Is a rim of cerebral cortex on the medial surface of each hemisphere
Cranial Nerves (H9)
XII.) Hypoglossal
Motor. Muscles of the larynx and lower pharynx, promotes speech and swallowing
XI.) Accessory
Motor. Neck muscles, controls movement of the head
X.) Vagus
Motor. Terminal ganglia serving thoracic and upper abdominal organs (heart and small intestines)
IX.) Glossopharygeal
Motor. Pharyngeal muscles, Geniculate ganglion, Otic ganglion
VIII.) Vestibuocochlear
Sensory. Spinal ganglion (hearing), Vestibular ganglion (balance).
VII.) Facial
Mixed (both sensory & motor). Conducts taste sensationa from anterior two-thirds of tongue; relays motor output to muscles of facial expressions; tear glands and most salivary glands. Located in nuclei in the pons
VI.) Abducens
Motor. Innervates one extrinsic eye muscle (lateral rectus) to move the eye. Located in Potine (abducens) nucleus of the pons
V.) Trigeminal
Mixed (both sensory & motor). Mixed nerve that consists of three divisons: ophlamic, maxillary, and mandibular. Located in the nuclei of pons
IV.) Trochlear
Motor. Contracts one extrinsic eye muscle (superior obique) to move eye inferiorly and laterally. In the Trochlear nucleus within the midbrain
III.) Oculomotor
Motor. Oculomotor and Edinger Westphal nuclei within the midbrain
II.) Optic
Sensory, (Vision). Retina of the eye
I.) Olfactory
Sensory, (smell). Receptors in olifactory epithelium of nasal cavity
Anatomy of Spinal Cord and Nerves (H10)
Spinal Nerve Plexuses
Sacral Plexus
Superior gluteal nerve, Inferior gluteal nerve, Sciatic nerve, Tibial nerve, Posterior cutaneous nerve of thigh, Pudendal nerve
Lumbar Plexus
Iliohypogastric nerve, Ilioinguinal nerve, Genitofemoral nerve, Lateral nerve, Femoral nerve, Obturator nerve
Brachial Plexus
Musculocutaneous nerve, Axillary nerve, Median nerve, Radical nerve, Ulnar nerve, Intercoastal nerve, Subcostal nerve, Second lumbar vertebra
Cervical Plexus
Lesser occipital nerve, Greater auricular, Ansa Cervicalis, Transverse cervical nerve, Supraclavicular nerve, Phrenic Nerve
Spinal Nerves
There are 8 pairs of cervical nerves (C1-C8), 12 pairs of thoracic nerves (T1-T12), 5 pairs of lumbar nerves (L1-L5), 5 pairs of sacral nerves (S1-S5), and 1 pair of coccygeal nerves
Paths of communication between the spinal cord and specific regions of the body
Roots
Dorsal Root Ganglion
Contains cell bodies of sensory neurons
Ventral Root
Including rootlets contain axons of motor neurons, which conduct nerve impulses from the CNS to effectors (muscles and glands)
Spinal cord cross section structures
Posterior ramus of spinal nerve
Anterior ramus of spinal nerve
Subarachnoid space
Epidualr space
Posterior root of spinal nerve
Pia mater
Denticulate ligament
Dura mater and arachnoid mater
Anterior root of spinal nerve
Gross anatomy of Spinal Cord
Dura Mater (outer)
Arachnoid mater (middle)
Denticulate ligament
Pia Matter (inner)
Subarachnoid space
Anterior median fissure
Subdural space
Central canal
Posterior median sulcus
White Matter
Contains sensory and motor tracts
Dense collections of myelinated fibers (axons)
Gray Matter
Site for integration of EPSP's and IPSP's
Mostly neuron cell bodies and unmyelinated fibers
Function (H1)
Sensation
Receiving information about the environment to gain input about what is occurring on the inside and outside of the body
Response
Produces a response on the basis of the stimuli perceived by sensory structures
Integration
Stimuli that are received by sensory structures are communicated to the nervous system where that information is processed
Organization (H2)
Functional Organization
Central Nervous System (CNS)
integrative and control centers
Peripheral nervous system (PNS)
Cranial and spinal nerves serve as communication lines between CSN and all of the body
Sensory (afferent) divison
Somatic and visceral sensory nerve fibers, conducts impulses from receptors to the CNS
Motor (efferent) divison
Motor nerve fibers, Conducts impulses from the CNS to effectors (muscles and glands)
Autonomic
(Involuntary) Visceral motor, Conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands
Parasympathetic divison
Conserves energy, promotes house-keeping functions during rest (rest and digest)
Sympathetic division
mobilizes body for activity (fight or flight)
Somatic
(Voluntary) Somatic motor, Conducts impulses from the CNS to skeletal muscles
anatomical
peripheral nervous system PNS
ganglia
Reception of sensory stimuli by dorsal root and cranial ganglia (somatic and automatic), relay of visceral motor responses of autonomic ganglia (automatic)
spinal nerves
Both sensory and motor
cranial nerves
Sensory and motor neurons (somatic and autonomic)
central nervous system CNS
spinal cord
Initiation of reflexes from ventral horn (somatic) and lateral horn (autonomic), pathway for sensory and motor functions between periphery and brain (somatic and automatic)
brain
Perception and processing of sensory stimuli (somatic and autonomic)
Execution of voluntary motor responses (somatic)
Regulation of homeostatic mechanisms (automatic)
Sensory Receptors (H6)
Types of receptor cells
Photoreceptor
Receptor cells specialized to respond to light stimuli
Chemoreceptors
Interprets chemical stimuli, such as an objects taste or smell
Mechanoreceptor
Physical stimuli, such as pressure and vibration, as well as the sensation of sound and body position
Nociceptors
Interprets the presence of chemicals from tissue damage, or similar intense stimuli
Proprioceptor
Receptor located near a moving part of the body, such as a muscle, that interprets the positions of the tissues as they move
Interoceptor
Interprets stimuli from internal organs and tissues, such as the receptors that sense the increase in blood pressure in the aorta and carotid sinus
Exteroceptor
Receptor that is located located near a stimulus in the external environment, such as the somatosensory receptors that are located in the skin
Feedback Loop (H2)
Effectors
Sweat Glands, skeletal muscles
Control Center
Thermoregulatory center in the brain
Receptors
Temperature sensitive cells in skin and brain
Neurophysiology (H4)
Neuron cell membrane
The cell membrane is composed of a phospholipid bilayer and has many transmembrane proteins, including different types of channel proteins that serve as ion channels
ion channels
Voltage Gated Ion Channel
Voltage gated Ca++
Voltage gated K+
Voltage gated Na+
Usually closed, but they open in response to changes in electrical charge across the plasma membrane
Mechanically gated channels
When mechanical change occurs in the surrounding tissue, such as pressure or touch, the channel is physically open
Leakage Channels
In certain situations, ions need to move through the membrane randomly, the particular electrical properties of certain cells are modified by the presence of is type of channel
Ligand-gated Channels
Neurotransmitter (such as acetylcholine) binds to a specific location on the extracellular surface of the channel protein, the pore opens to allow certain ions through.
Neuron signaling
Action potential
Change in membrane potential travels down cell membrane
continuous conduction - without myelin
saltatory conduction - action potential "jumps" from neurofibril node to next
triggers slow-acting voltage-gated K+ channels
causes repolarization (potential to drop back to -70)
triggers fast voltage-gated Na+ channels
causes depolarization (potential increases to 30 mV)
begins at axon hillock (first voltage gated channels)
role of Na+/K+ pump
resting potential restored
Na+/K+ pump re-establishes Na+ and K+ gradients
Neurotransmitter release
AP triggers voltage gated calcium channels
influx of calcium triggers exocytosis of neurotransmitter
allow influx of Ca++
only on synaptic bulb
Resting potential
due to leakage K+ channels andICF/ECF ion concentrations
normal negative potential - approx -70 mV of neuron inner cell membrane
Graded potentials
Threshold
occurs when summation of EPSPs and IPSPs reaches threshold at the axon hillock
Summation
Spatial
many areas of the neuron are stimulated at once
Temporal
one area of neuron is stimulated repeatedly
EPSP - excitatory post-synaptic potential
occurs when positive ions enter the neuron (Na+, Ca++)
IPSP - inhibitory post-synaptic potential
occurs when positive ions leave the neuron (K+) or negative ions enter neuron (Cl-)
Stimuli from neurotransmitters open ligand-gated channels on dendrites or soma
Influx of ions (ex. Na+, Cl-) or outflow of ions (ex. K+) changes local membrane potential
Gross & microscopic anatomy of nervous tissue (H3)
Tract
Bundles of axons within the CSN in which the axons have a similar function and share origin and destination
Nerve
A bundle of axons in the PSN
Structural types of neurons
Unipolar
Single short process, emerges from cell body, divides into proximal and distal branches, found in ganglia in PSN. Sensory
Multipolar
Three or more processes. One axon and rest are dendrites. Most common neuron in humans. Mostly Motor, some are sensory
Bipolar
Two processes, axon and dendrite that extend from opposite sides of cell body, found in some special sense organs. Sensory
Neuron Processes
Cell body (Soma)
Receives information from other neurons
Varies in location. Biosynthetic center of the neuron, contains the usual organelles needed to synthesize protiens and other chemicals
Dendrites
Receives signals from other neurons
One of many branchlike processes that extends from the neuron cell body and functions as a contact for incoming signals (synapses) from other neurons or sensory cells
Axon
Carries an electrical signal (action potential) away from cell body toward a target cell
Conducts an output signal, typically away from the cell body
Glial cells
in PNS
Schwann Cells
Insulate axons with myelin in the periphery, they are very similar to oligodendrocytes, important to regeneration of damaged peripheral nerves
Satellite Cells
Found in sensory and autonomic ganglia, surround the cell bodies of neurons. Perfrom similar functions as astrocytes that are found in the CNS
in CNS
Oliogodendrocytes
Large cells, with bulbous body and slender cytoplasmic extensions. These cells wrap around and insulate axons in the CSN to form a myelin sheath, this allows faster propagation of action potentials.
Ependymal Cells
Ciliated simple cuboidal or simple columnar epithelial cells that line the internal cavities of the brain and central canal of spinal cord. Work together with blood capillaries to form choroid plexus. This helps produce cerebrospinal fluid, a clear liquid that covers the external surface of the CSN.
Microglial Cells
Small, classified as phagocytic cells of the immune system, they wonder through the CSN and replicate in response to infection. They also protect against any microorganisms and other hamful substances and debris of dead or damaged nervous tissues.
Astrocytes
Most abundant and versatile glial cells, and have a "star shape", support neurons in the CNS, by maintaining the concentration of the chemials in extracellular space, removing excess signaling molecules, reacting to tissue damage and contributing to the blood-brain barrier.