Week 3: The Somatic Nervous System PT. 1 & Sensory Perception Flashcards
How can sensory receptors be classified?
Structurally or Functionally
What is a structural sensory receptor?
It refers to their position in relation to stimuli being sensed.
What are the 3 Structural classifications of sensory receptors?
Exteroceptor
Interoceptor
Propioceptor
What is a exteroceptor?
Located near stimulus in EXTERNAL environment
EX. somatosensory receptors in skin
What is an interoceptor?
Intercepts stimuli from INTERNAL organs/tissues
EX. Baroreceptors sense changes in BP in the aorta/carotid sinus
What is a proprioceptor?
Located near MOVING PART OF BODY (muscle) and interprets position of tissues as they move
What is a functional sensory receptor?
Transduction of stimuli or how the mechanical, light, or chemical changed the cell membrane potential.
What are the 3 structural receptor types?
Free Nerve Ending
Encapsulated Ending
Specialized Receptor Cell
What is a free nerve ending (structural sensory receptor)?
It is a neuron with dendrites embedded in tissue that receives sensations directly.
EX. Pain/temperature receptors in the dermis of skin.
What is an encapsulated ending (structural sensory receptor)?
Neuron with sensory nerve ending encapsulated in connective tissue for enhanced sensitivity.
EX. Lamellated corpuscles in skin respond to pressure/touch.
What is a specialized receptor cell (structural sensory receptor)?
Distinct structural components that interprets specific types of stimuli.
EX. Cells in retina that responds to light = photoreceptor)
What is an ion/macromolecule (function receptor)?
It affects transmembrane receptor proteins when chemicals diffuse across the cell membrane.
What is a physical environment (function receptor)?
Affects the receptor cell membrane potentials.
What is an electromagnetic radiation (EMR) (functional receptor)?
From visible light (only EMR humans can detect)
What are the 3 types of stimuli?
Chemical Stimuli
Solute Stimuli
Physical Stimuli
What are the 2 forms of chemical stimuli?
Chemoreceptor and Nociceptor
What is a chemoreceptor (chemical stimuli)?
Interprets chemical stimuli (taste & smell)
What is a nociceptor (chemical stimuli)?
Interprets chemical stimuli from tissue damage (pain)
What is the 1 form of solute stimuli?
Osmoreceptor
What is an osmorecpetor (solute stimuli)?
Interprets solute concentrations of body fluids
What are the 2 forms of physical stimuli?
Mechanoreceptor and Thermoreceptor
What is a mechanoreceptor (physical stimuli)?
Interprets pressure, vibration, sensation of sound and body position (hearing & balance)
What is a thermoreceptor (physical stimuli)?
Interpret temperatures above (heat) or below (cold) normal body temperature
What are sensory modalities?
It is the way information is encoded/transduced in the body.
What are submodalities?
The five major senses can be broken down into more specific categories.
> Ex. touch can be separated into light pressure, deep pressure, vibration, itch, pain, temperature, or hair movement.
What are the 5 major senses?
Taste, Smell, Touch, Hearing/Balance, Sight
What are general senses?
They are distributed throughout the body and have receptor cells within the structures of other organs.
They contribute to the sense of touch, body movement, and is the most important of automatic functions.
What are specific senses?
Specific organ devoted to it.
EX. Eye, Inner Ear, Tongue, Nose
What are the 3 parts of the External Ear?
Auricle (Pinna)
Auditory (Ear) Canal
Tympanic Membrane (Ear Drum)
What is the Auricle (Pinna)?
The large, fleshy structure on the lateral aspect of the head, and its C-shaped curves direct sound waves to the auditory canal.
What is the Auditory (Ear) Canal?
Enters the skull through external auditory meatus of temporal bone.
What is the Tympanic Membrane (Ear Drum)?
Vibrates when struck by sound waves.
What are the 3 parts of the Middle Ear?
Malleus (Hammer)
Incus (Anvil)
Stapes
What is the Malleus (Hammer)?
Attached to the tympanic membrane (TM) and articulates with the Incus.
What is the Incus (Anvil)?
Articulates with the Stapes
What is the Stapes?
Attached to the inner ear
What are the 2 parts of the Inner Ear?
Cochlea (hearing)
Vestibule (balance)
What is the Cochlea?
It contains sensory neurons of spinal ganglia and attached to the Stapes through oval window.
What is the Vestibule?
It is a fluid-filled tube starting at the oval window that extends from the window, over top the cochlear duct (central cavity of cochlea containing sound-transducing neurons with organs of Corti).
Where are the Eyes located?
Located within orbits of the skull that protect and anchor the soft tissues of the eyes.
What protects the Eyes?
Eyelids with lashes protect eyes from abrasions.
Inner surface of eyelids in palpebral conjunctiva.
Conjunctiva extends over the sclera and connect the eyelids.
What are Tears?
Produced by the lacrimal gland at the superior and lateral sides of the eyeball.
Lacrimal duct to the medial corner of the eye.
Tears wash away particles from the conjunctiva.
What is the Fibrous Tunic?
It is the OUTERMOST layer of the eye including the sclera and cornea.
What are the 2 parts of the Fibrous Tunic layer?
Sclera and Cornea
What is the Vascular Tunic?
It is the MIDDLE layer of the eye made up of the choroid, ciliary body, and iris.
What are the 3 parts of the Vascular Tunic layer?
Choroid, Ciliary Body, Iris
What is the Neural Tunic?
It is the INNERMOST layer of the eye.
What is singular part of the Neural Tunic layer composed of?
The Retina
What is the sclera?
It covers 5/6 of the eye’s surface area
What is the cornea?
It covers the anterior part of the eye and allows for light to enter, then works with the lens to focus light on the retina.
What is the Choroid?
It is vascularized connective tissue that supplies blood to the eyeball.
What is the Ciliary Body?
It is the muscular structure attached to the lens by suspensory ligaments (zonule fibres), and helps to bend lens to focus light on the retina.
What is the Iris?
It is the smooth muscle that constricts (response to bright lights) or dilates (response to dim lights).
What is the Retina?
It is composed of several layers and contains specialized cells for processing visual stimuli.
What are the 2 cavities of the eye?
Anterior Cavity and Posterior Cavity
What is the Anterior Cavity of the eye?
It is the space between the cornea and lens, and includes the iris and ciliary body.
What is the Posterior Cavity of the eye?
It is the space behind the lens and extends to posterior side of interior eyeball
What is Aqueous Humor?
Watery fluid that fills the Anterior cavity
What is Vitreous Humor?
Viscous fluid that fills the Posterior cavity
What are the 6 extra ocular muscles of the eye?
- Superior rectus
- Medial rectus
- Inferior rectus
- Lateral rectus
- Superior Oblique
- Inferior Oblique
Which way does the Superior Oblique muscle rotate the eye?
Laterally
Which way does the Inferior Oblique muscle rotate the eye?
Laterally in OPPOSITION to the Superior Oblique
What are Photoreceptors?
They change membrane potential when stimulated by light.
What are the 2 parts of Photoreceptors?
Bipolar Cells and Amacrine Cells
What are Bipolar Cells?
They are within the outer synaptic layer and connect photoreceptors to retinal ganglion cells (RGCs) within the inner synaptic layer.
What are Amacrine cells?
They contribute to retinal processing prior to action potential being produced in RGCs.
What causes blind spots in our vision?
A lack of photoreceptors.
EX. no photoreceptors at the optic disc.
What are the 2 segments of Photoreceptors?
Inner Segment and Outer Segment
What is the Inner Segment?
It contains nucleus and common organelles of a cell.
What is the Outer Segment?
It is where photoreception takes place.
What are the 2 parts that make up the Outer Segments?
Rods and Cones
What are Rods?
They are rod shaped and contain a stack of membrane bound discs containing photopigment rhodopsin.
Sensitive to vision in LOW LIGHT.
What are Cones?
They are cone shaped, infolding in cell membranes that contain photopigment iodopsin.
There are 3 cones (red, blue, green) each linked to a particular wavelength of light.
Sensitive to BRIGHTER conditions.
What are the 5 types of tastes?
Sweet, Sour, Salty, Bitter, Unami
Taste: What is Sweet?
The sensitivity of gustatory cells to the presence of glucose/monosaccharides dissolved in the saliva.
> Affinity for each molecule to G protein receptor varies resulting in some sugars tasting sweeter than glucose.
Taste: What is Salty?
Perception of Na+ ions in saliva.
> Eat something salty and the salt crystals dissolve into Na+/Cl- ions in saliva.
Na+ concentration elevated outside gustatory cells, creating a strong concentration gradient-diffusion of the ions into the cells.
Entry of Na+ into these cells results in the depolarization of the cell membrane and the generation of a receptor potential.
Taste: What is Sour?
Perception of H+ ions concentration/acids in our food.
> Similar to Na+ with salty foods, H+ ions enter the cell and trigger depolarization.
Increasing H+ ion concentration in saliva lowers pH triggering progressively stronger graded potentials in the gustatory cells.
Taste: What is Bitter?
Large diversity of bitter-tasting molecules, often triggers a gag reflex. Are often combined with sweet foods to make more palatable.
> Molecules either depolarize or hyperpolarize gustatory cells.
Molecules either increase or decrease G protein activations within gustatory cells (dependent on type of binding molecule).
Taste: What is Unami?
Often perceived while eating protein-rich foods.
> Like sweet/bitter taste, relies on activation of G protein-coupled receptors.
Molecule that activates this receptor is the amino acid L-glutamate.
What is Gustation (taste)?
Gustation is the special sense associated with the tongue.
The tongue and oral cavity are lined with stratified squamous epithelium cells.
What are Papillae?
Raised bumps on the tongue containing structures for gustatory transduction.
4 types based on appearance:
1. circumvallate
2. foliate
3. filiform
4. fungiform.
What are Taste Buds?
Taste buds are located within papillae and contain specialized gustatory receptor cells that transduce taste stimuli by releasing neurotransmitters.
What is Neurotransmitter Activation?
Neurotransmitters activate sensory neurons in facial, glossopharyngeal, and vagus cranial nerves.
What is the Facial Nerve?
The Facial nerve connects to taste buds in the anterior 2/3s of the tongue.
What is the Glossopharyngeal Nerve?
The Glossopharyngeal nerve connects to taste buds in the posterior 1/3 of the tongue.
What is the Vagus Nerve?
The Vagus nerve connects to taste buds in extreme posterior section of tongue and are more sensitive to noxious stimuli like bitterness.
What is Olfaction (smell)?
Olfaction (smell) is the response to chemical stimuli.
What is the Olfactory Process?
- Airborne (odorant) molecules are inhaled.
- Molecules are dissolved in mucus and bind to proteins (odorant = protein complex) that get transported to olfactory dendrites.
- Once at olfactory dendrites, odorant-protein complex binds to receptor proteins (G protein-coupled).
- Produces graded membrane potential in olfactory neurons that travel to the brain.
What are Olfactory Receptor Neurons?
They are bipolar sensory neurons located in the olfactory epithelium (superior nasal cavity), that have dendrites extending from the apical surface of epithelium into the mucous lining the cavity.
Where are Olfactory Receptor Neurons located?
Superior Nasal Cavity (olfactory epithelium)
What are the steps of the Olfactory Pathway?
Extends from epithelium through cribriform plate (ethmoid bone) into the brain.
Forms olfactory tract, connects to olfactory bulb (ventral surface of frontal lobe).
Axons split to various brain regions.
What are the main brain regions of the Olfactory Pathway?
Primary olfactory complex (temporal lobe)
Limbic system and hypothalamus (long-term memory, emotional responses)
What are unique features of the Olfactory Pathway?
There is no synapse in thalamus before the cerebral cortex.
It has a strong connection to memory and emotion.
Can replacement Olfactory neurons occur?
YES
They are regularly replaced as they can be harmed by airborne toxins.
New axons grow along existing cranial nerve axons.
What is Anosmia?
The loss of sense of smell
What are the 2 types of axons found in Spinal Nerves?
Afferent and Efferent
What are Afferent axons?
Afferent axons are impulses from sensory impulses (eg. skin) that move TOWARDS the brain.
What are Efferent axons?
Efferent axons are impulses that travel AWAY from the brain to the muscles of effector muscles.
What do the spinal nerves split into?
Dorsal Roots and Ventral Roots
What are Dorsal roots (spinal nerves)?
They contain sensory neuron axons
What are Ventral roots (spinal nerves)?
They contain motor neuron axons
What are cranial nerves?
They are nerves that emerge directly from the brain, including the brainstem.
How many cranial nerves are there?
There are 12 cranial nerves
Most cranial nerves are IPSILATERAL, which means:
That they are on the same side.
EX. The cranial nerve on the right side connects to the right side of the brain.
