Sensory Physiology Flashcards
What are sensory receptors? (3)
- Are specialised cells/neuron endings that convert stimuli into electrical signals
- Action potential is generated by light striking the eye = Action potential triggered by air vibrating in the ear.
- May be grouped to form → sensory organs
Sensation:
→ action potentials that reach brain via sensory neurons, aware of stimulus
Perception:
→ brain interprets, giving an understanding of what the sensation means
Types of sensations: (5)
Functions of Sensory receptors: (4)
- Sensory transduction → change of stimulus into electrical energy, change in membrane potential is known as receptor potential, graded potentials
- Amplification → enhancement of signal
- Transmission → Synapses
- Integration → processing begins as soon as information is received, summation; sensory adaptation - decrease in responsiveness during continued stimulation; selective receptors
What are somatic sensations? (6)
Originate at more than one location in body
- Temp
- Touch
- Vibration
- Pressure
- Pain
- Awareness
What are special senses? (4)
Receptors restricted to particular areas of the body
- Taste
- Smell
- Vision
- Hearing
What is mechanoreceptor?
A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion.
Sense: (5)
- Physical deformation
- Pressure
- Touch
- Stretch
- Motion
- Sound
Mechanoreceptors are modified ____ endings of sensory neurons.
dendritic
Types of mechanoreceptors: (4)
- Tactile receptors
- Proprioceptors
- Statocysts (in invertebrates)
- Hair cells
Normally there are four main types of _____, or hairless, mammalian skin: Glabrous skin/Hair-free skin is found mainly on the palms and soles. It is innervated by _____ nerves that help us to understand subtle tactile details.
glabrous
specialized
What are mechanoreceptors in hairy skin? (4)
- Lamellar corpuscles
- Tactile corpuscles
- Merkel nerve endings
- Bulbous corpuscles
TACTILE RECEPTORS
Location:
Response (to):
Location: in the skin
Response (to): pressure/touch
May be simple nerve endings or may form specialized receptors
What is the function of PROPRIOCEPTORS?
By transducing changes in muscle shape and length, provide the information needed to distinguish different types of movement.
PROPRIOCEPTORS
Location:
Response (to):
Location: muscles, tendons, and joints
Response (to): tension + movement
- Allow animal to perceive positions of body parts and overall orientation
- Little sensory adaptation → continuously supply information
Types of Proprioceptors: (3)
- Muscle spindles
- Golgi tendon organs
- Joint receptors
What are muscle spindles? (4)
- modified skeletal muscle cells in skeletal muscle
- Function: detect muscle movement
- Location: parallel to muscle fibres
- Response (to): stretch (tap patellar tendon)
What are Golgi tendon organs? (4)
- dendrites around collagen in muscle-tendon junction
- monitor skeletal muscle tension
- stretch when muscle contracts
- transduce (convert) force exerted by muscle
What are joint receptors?
- Monitor pressure, tension, and movement in joints
What are STATOCYSTS (IN VERTEBRATES)? (3)
Respond (to): Gravity
Function: Allow invertebrates to maintain orientation with respect to gravity
The statocyst is a balance sensory receptor present in some aquatic invertebrates, including molluscs, bivalves, cnidarians, ctenophores, echinoderms, cephalopods, and crustaceans. A similar structure is also found in crustaceans.
What is the structure of statocysts?
The statocyst consists of a sac-like structure containing a mineralised mass (statolith) and numerous innervated sensory hairs (setae).
- The statolith’s ____ causes it to push against the setae when the animal accelerates.
- Deflection of setae by the statolith in response to ____ activates neurons, providing feedback to the animal on change in orientation and allowing balance to be maintained.
- In other words, the statolith shifts as the animal moves. Any movement large enough to throw the organism off ____ causes the statolith to brush against tiny bristles which in turn send a message to the brain to correct its balance.
inertia
gravity
balance
What are the functions of hair cells?
Auditory + vestibular apparatus
- Vertebrate hair cells required for hearing and balance have “hairs” formed into a bundle that bends when surrounding fluid moves.
- Each hair cell releases an excitatory neurotransmitter at a synapse with a sensory neuron, which conducts action potentials to the CNS.
- Bending of the bundle in one direction depolarizes the hair cell, causing it to release more neurotransmitters and increasing the frequency of action potentials in
the sensory neuron. - Bending in the other direction has the opposite effect.
- number of K+ channels open depends on the tension of connecting filaments
What are chemoreceptors? (2)
Function: transduce chemical compounds into neural impulses
Responsible for:
- gustation (taste – chemicals dissolved in water) → occurs in taste buds
- olfaction (smell – gaseous chemicals in air) → occur in olfactory epithelium
What are electromagnetic receptors? (2)
Function: transduce various forms of electromagnetic energy, e.g., light, electricity, magnetism
Well-developed in fish and sharks and some mammals e.g., duck-billed platypus
Earth’s electromagnetic field, e.g., salmon, pigeons, turtles, humans
What are thermoreceptors? (2)
Function: detect temperature in internal and external environments
Location: in skin and anterior hypothalamus
What are pain receptors?
Unencapsulated endings near skin surface –
respond to excessive pressure, heat, light or chemicals, density highest in skin
What are the type of pain receptors? (2)
- Fast pain (sharp or acute pain) → physical pressure, heat, near the surface of body, strong withdrawal response
- Slow pain → muscles or internal organs, chemically sensitive pain receptors, chemicals from damaged tissue
(histamine)
- Chemoreceptors
- Taste
* Chemical signal to ____ _____
* Rough – papillae, taste buds at the surface of
folds
* _______ taste buds – mostly on the tongue
* taste bud = 25 taste cells + 25 supporting cells
* Taste hairs at the tip – contain ______
* Specific to certain chemicals (tastant)
* ______ bind to chemoreceptors
5 tastes: __________.
action potential
10 000
chemoreceptors
Tastants
sweet, sour, salty, bitter, and umami
What is a taste bud? (3)
▪ Taste cell is not a neuron
▪ Taste cell + sensory neuron required to convert chemical stimulus to nerve impulse
▪ Chemical molecules in food bind to receptors, leading to K+ closing, depolarization
4 taste qualities, respond to specific receptors
▪ Sweet (____), sour (____), salty (___), bitter (_____ ____ chemicals)
▪ Umami (delicious flavour) – _____ taste receptor → common AA in proteins
▪ All tastes elicited from all the regions of the tongue with taste buds -no evidence of spatial segregation of ______.
sugar
H+ ion
Na
toxic plant
glutamate
sensitivities
The sensitivity of taste:
▪ Flavours are recognised mainly through the sense of ____
▪ Taste cells along with smell cells are the only sensory cells that are regularly replaced throughout a person’s life span.
▪ Taste cells usually last ___ days
smell
10
Process of perceiving odours: (3)
▪ Gaseous and airborne odorants – enter nasal passages and dissolve in mucous
▪ Bind to chemoreceptors on olfactory hairs to generate impulse
▪ Olfactory receptor cells synapse with olfactory neurons in the nearby olfactory bulbs in the brain
- Mechanoreceptors
- Hearing
* Sound – waves of compressed air
* Sound _____ – refers to the energy of sound
* Loudness – subjective interpretation of sound
* Both related to _____ – measured in decibels
* 0 dB (barely audible, the threshold of human hearing)
In hearing the ear _____ this mechanical stimulus into nerve impulses that the brain perceives as sound. To hear music, speech, or other sounds we rely on hair cells that detect _____.
intensity
amplitude
transduces
motion
Mechanism of hearing: (6)
- Sound waves enter the ear go through the external auditory canal and hit the eardrum
- Eardrum is connected to the malleus (smallest bone) which sends sound vibrations to the incus which pass them to the stapes.
- Stapes push against the oval window
- Signal/ sound waves is passed to the cochlear duct (filled with fluid) which contains organ of Corti (the organ for hearing) → contains hair cells which transmit vibrations into electrical impulses which are carried to the brain
- Cochlear apex (fibres at end of cochlear) resonate to lower frequency sound
- Oval window (fibres at beginning of cochlear) respond to higher frequencies
Scala Vestibuli and Tympani contain ____ and Scala Media contains _____.
When the oval window is depressed by ossicles, it creates waves that travel through the fluid of the cochlea. These waves cause the ____ membrane to move as well.
perilymph
endolymph
basilar
What happens waves flow through the basilar membrane? (2)
- When waves flow through basilar membrane, it causes small waves to travel through the membrane as well (travelling wave). Different sections of basilar membrane respond to different frequencies of sound. As waves progress down membrane, they reach their peak at the part of the membrane that responds to the frequency of the cell that we have created by the original stimulus.
- The basilar membrane translates accurately the frequency of sounds picked up by ear into neural activity that can be sent to brain.
What do the Vibrations of the stages against the oval window produce?
Vibrations of the stages against the oval window produce pressure waves (black arrows) in the fluid (perilymph in blue) of the cochlea. The waves travel to the apex via the vestibular canal and back towards the base via the tympanic canal. The energy in the waves causes the basilar membrane (pink) to vibrate, stimulating hair cells – more in a bit. Because the basilar membrane varies in stiffness along its length, each point along the membrane
vibrates maximally in response to waves of a particular frequency.
Basilar membrane
- Supports _____ hair cells
- Hairlike projection embedded in ____ membrane
- Organ of Corti – converts pressure waves to ____
- Vibration of basilar membrane causes hairs to bend
- Movement of hair cells open ion channels and neurotransmitters to _____ _____.
15000
tectorial
impulses
auditory nerve
Vestibular apparatus – fluid-filled canals & chambers next to cochlea.
* 3 semi-circular canals – ____ ______
* vestibule – senses ____ position & linear _____ (otolith organs)
rotational movement
static
acceleration
How is rotational movement sensed? (4)
- Sensing rotational movement – semi-circular canals
* Fluid filled tubes of bone
* End of each canal – ampulla, containing gel-like dome called cupula
* Hairs of mechanoreceptor sensory neurons embedded in cupula
* Moving fluid bends cupula and hairs
- Sensing head position and acceleration
* Position – mechanism sensitive to gravity
* Two chambers of the _____
- _____ - more sensitive to vertical acceleration (like riding in an elevator)
- _____ - more sensitive to horizontal acceleration (riding in a car)
vestibule
Saccule
Utricle
What do horizontal cells do? (4)
→ receive input from multiple photoreceptor cells
* They integrate signalling from various populations of photoreceptors
* Make adjustments to signals sent to bipolar cells
* Regulate activity in photoreceptor cells themselves
What do Amacrine cells do? (2)
→ receive input from bipolar cells
* Integrate + regulate activity in bipolar and ganglion cells
4 layers of the Retina:
- Pigmented cells & choroid –absorb light not captured by photoreceptor cells
- Rods & cones - photoreceptor cells, synapse with…
- Bipolar cells - neurons that synapse with layer of rods & cones, synapse with…
- Ganglion cells – also neurons, long axons become optic nerves, integrate information
