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NERVOUS SYSTEM (SENSES (Receptors based on stimulus type: (Chemoreceptors …
NERVOUS SYSTEM
SENSES
Eye components and visual pathway:
Components:
Vascular Layer:
choroid
(highly vascular, darkly pigmented membrane under sclera) - nourishes other layers, absorbs light, prevents scattering;
ciliary body
(ciliary muscle and ciliary processes, ciliaray zonule) - acts to focus lens;
iris
(circularly arranged and radiating smooth muscle fibers) - acts to vary the size of the pupil (sphincter and dilator pupillae muscles).
Inner Layer:
retina
(thin pigmented layer and thicker neural layer, under choroid) - absorbs light (contains photoreceptor cells: rod and cone cells);
optic nerve
(runs from the eye to the brain)
Fibrous Layer:
sclera
( white dense connective tissues) - provides shape and anchoring site for extrinsic eye muscles;
cornea
(transparent, avascular, connective tissue) - light-bending apparatus of the eye.
Pathway: Cornea -> lens ->retina -> optic nerve -> optic chiasma ->optic tract -> midbrain ->thalamus -> primary visual cortex.
Olfaction components and pathway:
Pathway:
Nasal conchae -> olfactory sensory neurons -> olfactory bulb -> olfactory tract -> limbic region and primary olfactory cortex.
Components:
Receptors are in the roof of nasal cavity, part of olfactory epitheium (pseudostratified columnar ep.), olfactory sensory neurons, olfactory stem cells, olfactory cillia
Receptors based on stimulus type:
Chemoreceptors - chemicals in solution.
Photoreceptors - light (eyes).
Thermoreceptors - temperature changes.
Nociceptors - pain.
Mechanoreceptors - touch, pressure, stretch, vibrations.
Baroreceptor
-blood pressure.
Gustation components and pathway:
Components:
Taste buds in mucosa of pharynx and mouth, papilla, gustatory epithelial cells, basal epithelial cells, gustatory hairs, taste pore.
Pathway:
Taste buds with receptor cells ->3 cranial nerves (facial (VII), glossopharyngeal (IX), vagus (X)) -> medulla oblongata ->thalamus -> primary gustatory cortex in the insula lobe.
Receptors based on stimulus origin:
Interoceptors - changes in chemical concentration, taste, stretching, temperature (internal organs such as: lungs, bladder, digestive tube).
Proprioceptors - degree of stretch (musculoskeletal organs).
Exteroceptors - environment (skin, special senses such as: sight, hearing, taste, olfaction, smell, equilibrium balance).
Ear components and pathway:
Components:
Middle ear:medial and lateral boundary, oval and round window, epitympanic recess, mastoid antrum, pharyngotympanic tube, auditory ossicles, malleus, incus, stapes, skeletal muscles: tensor tympani and stapedius.
Internal ear: bony labyrinth, membranous labyrinth, endolymphatic flluid, perilymphatic fluid, cochlea.
External ear: auricle (pinna), helix, lobule, external acoustic meatus, tympanic membrane.
Pathway:
Acoustic meatus -> tympanic membrane -> middle ear ->auditory ossicles ->cochlea ->cochlea nerve -> vestibular nerve (VIII) -> medulla oblangata ->pons -> midbrain -> thalamus -> primary auditory cortex in temporal lobe.
NERVOUS SYSTEM ORGANIZATION
PNS main structures and functions:
Structure: cranial nerves, spinal nerves, ganglia.
Function: gathers sensory information, passes it on.
Somatic division/motor: voluntary; conducts impulses from the CNS to skeletal muscles (mainly skin, body torso, skeletal muscles).
CNS main structures and functions:
Structure: brain and spinal cord
Function: integrating and command center of the nervous system; receives incoming sensory signals, interprets, and dictates motor responses.
Autonomic division/motor:involuntary; conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands (mainly ventral body cavity).
Sympathetic (mobilizes body systems during activity)
Parasympathetic (conserves energy).
NEURONS
Major components:
Cell body, neuron processes (dendrites and axons), synapses.
Functional types:
Sensory(afferent), motor(efferent), and interneurons
Structural classification:
Multipolar, bipolar, unipolar
ANATOMY OF NERVOUS SYSTEM
Nerve components:
Myelinated and unmyelinated axons (nerve fibers surrounded by Schwann cells) enclosed by wrappings of connective tissue (endoneurium, perineurium, epineurium).
Glial cells:location, description:
Location:
CNS
Astrocytes (most abundant, regulating neurotransmitter levels, signaling increased blood flow through capillaries, controlling ionic environment).
Microglial (phagocyte).
Ependymal (forms a simple epithelium that lines the central cavity of the spinal cord and brain).
Oligodendrocytes (myelin sheaths creation).
PNS
Satellite (regulates what goes in/out of neuron cell bodies).
Schwann (myelin sheaths production).