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Nervous System (Senses (Sensory Types (Thermocrecptors
Heat/Cold,…
Nervous System
Senses
Sensory Receptors
Exteroceptors
Origin: External Environment
Location: Skin, Special Senses (Smell, hearing, taste)
Function: Monitors external environment
Interoceptors
Origin: Internal Organs
Location: Intestines, Bladder, lungs
Function: Senses organ pain, hunger, fullness
Proprioceptors
Origin: Muscles, tendons, ligaments, and joints
Location: Inside Muscles
Function: Tells where the body or body parts are in space
Eye
Sense: Vision
Components
Fibrous Layer
Sclera
- White part of the eye
- Gives shape to the eye
- Attachment point for extrinsic eye muscles
- Dense Connective Tissue
Cornea
- Outer layer of the fibrous layer
- Clear
- Focuses light on the Retina
Vascular Layer
Choroid
- Nourishes the other layers
- Deeply pigmented
- Absorbs light and prevents scattering of light
Internal Layer
Retina
Neural Layer
- Photoreceptors
- Axons converge to form the optic nerve
Optic Disc
- Blind Spot
- No Photoreceptors
- Place where the optical nerves converge
Cones
- Fewer
- Allow us to see color
- Best in bright light
Rods
- Many
- Sensitive to Light
- Vision in dim light
Precise Posterior Pole
Macula Lutea
- Yellow Spot
- Clearest Vision
Fovea Centralis
- Center of Macula Lutea
- Clearest vision (most sharp)
- Light gets focused here
Pigmented Layer
- Thinner layer
- Lies against the choroid
- Absorbs light
Iris
- Intrinsic Muscle
- Sphincter Muscle (Dilate/Constrict)
- Colored by the Pigmented layer
Lens
- Posterior to the Iris
- Focuses light on the retina
Posterior Segment
- Largest area
- Filled with Vitreous Humor
- Clear liquid, supports retina and lens, Gel like, maintains normal eye pressure
Anterior Segment
Posterior Chamber
- Aqueous Humor (Clear, water like)
- Iris to Posterior chamber
Anterior Chamber
- Aqueous Humor (clear, water like) continuously regenerated nourishes the lens and cornea
- Maintains normal inter-ocular pressure
- Iris to Cornea
Visual Pathway
Cornea (Focus)
Pupil
Lens (Focus)
Posterior Segment
Retina
Optic Nerve
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Sensory Types
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Photoreceptors
- Detects and reacts to light
Chemoreceptors
- Chemical sensor
- Monitors: Air, Saliva, Water, Blood
Nociceptors
- Monitor for pain or danger to the body
Mechanoreceptors
- Pressure, touch, vibration, stretch
Baroreceptors
- Monitor Blood Pressure in the body
Gustation
Sense: Taste
Components
Taste Buds
Location: Tongue, Inner Cheeks, Epiglottis, posterior wall of pharynx
Structure: Peg like with 50-100 epithelial gustatory cells
Function: Bind to molecules to determine taste
Saliva
- An enzyme that dissolves food to break apart molecules to be able to attach to taste buds
Nerves
Facial Nerve (VII)
- Taste receptors on the anterior part of the tongue.
Glossopharyngeal Nerve (IX)
- Taste Receptors on posterior part of tongue
Vagus Nerve (X)
- Taste Receptors on Epiglottis and pharynx
Gustation Pathway
Cranial Nerves VII, IX, X
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Olfaction
Sense: Smell
Components
Olfactory Cilia
- Hair like structure
- Apical Dendrite of the neuron
- Coated with a layer of mucus
Olfactory Epithelium
- Pseudostratified Ciliated Epithelium
- Embedded with sensory neurons
- Covers superior part of the nasal septum
Olfactory Bulb
- Located in the forebrain
- Axons branch and connect to Mitral cells via the glomeruli
- Nerves travel through the cribriform foraminia of the cribriform plate
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Ear
Sense: Hearing
Components
Auricle (Pina)
- External Ear
- Gathers Sound
- Amplification
External Acoustic Meatus
- Short tube in temporal plate
- Elastic Cartilage
- Lined with hairs and glands
Tympanic Membrane
- Ear Drum
- Boundary between external and middle ear
- Vibrates from sound waves to transfer to middle ear
Auditory Ossicles
- Three bones in the middle ear
- Amplify sounds
Cochlea
- Spiral shaped chamber
- Size of a small pea
- Liquid filed
- Takes vibration to create sound
- Receptor Epithelium for hearing
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Neurons
Components
Cell Body
- Contain the Nucleus and cytoplasm
- Can receive signals from other neuron cells
Chromatophilic Substance
- Clusters of Ribosomes and Rough Endoplasmic Reticulum
- Renews the Plasma Membrane of the cell body
- Protein within the cytosol
- Contain Neurofibrils that support the cell and prevent it from tearing apart
Dendrites
- Receives signals from other cells
Axon Hillock
- Where the signal starts at the cell body
- Axon comes from it
Axon Collateral
- A branch that comes out on an axon
- Could be more then one
Terminal Arborization
- End of the axon
- Several little branches
Axon Terminals
- Terminal Boutons
- on the very ends of the branches of the terminal arborizations
Functional Types
Motor Neurons
- Multipolar
- Cell bodies in the Central Nervous System
- Travel to muscles and glands in the Peripheral Nervous System
Sensory Neurons
- Unipolar
-Bipolar - Special Senses
- Cell bodies located in the ganglia of the Peripheral Nervous System (near the spinal cord)
Interneurons
- Between the neurons in the Central Nervous System
- Multipolar
- 99.98% of neurons are these
Structural Types
Multipolar
- Cell body on one end with the dendrites
- Axon extends from the cell body
- Located in muscles
Bipolar
- A Dendrite end and an Axon end
- Cell body is in the middle
- Used in the Special Senses
Unipolar
- One process comes out from the cell body and then splits in two
- Peripheral Process forms the receptive end
- Central Process forms a second receptive end
- Both processes are called the axon
- Located in the skin
Nervous System Anatomy
Glial Cells
Central Nervous System
Microglial
- Smallest
- Least abundant
- Elongated bodies with pointy projections
- Phagocytes of the nervous system
- Monitors for pathogens and damaged nervous tissue
Ependymal
- Simple Cuboidal/Columnar Epithelium
- Microvili and Cilia
- Lining spaces filed with cerebrospinal fluid called ventricles in the brain
- Cerebrospinal fluid created in the ventricle and moved around by the cilia
Astrocytes
- Most numerous
- Many processes that contact neurons and capillaries
- Support Neurons
- Maintain appropriate chemical environment
Oligodendrocytes
- Fewer branches then Astrocytes
- Plasma membrane is wrapped around one portion of several axons
- A Myelin sheath composed mostly of lipids
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Major Components
Nerves
- A bundle of neurons sending signals to the Central Nervous System or away from the Central Nervous System
- Most Nerves have: Sensory or Motor Neurons (Always Distinct)
Epineurium
- Tough fibrous connective tissue
- Surround the Nerve
Nerve
- A bundle of fascicles (axons)
Perineurium
- Fibrous connective tissue
- Surrounds each fascicle
Endoneurium
- Loose Connective Tissue
- Surrounds the Myelin sheath encased axon
Myelin Sheath
- Insulation that covers some axons
- Two Types: Myelinated and Non-myelinated
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