Physiol Exam 2: Chps. 10-12 + Labs 05-06 Flashcards
Describe the functions of sensory receptors
• Perceptions created by brain
• Sensory receptors respond (to stimuli), generate & propagate APs
1. Respond to a particular modality (form) of stimuli (internal or external)
— Different neural pathway & synaptic connections
2. Transduce (change) different forms of energy (stimuli) into APs → CNS for perception/understanding
Define the following terminology: tonic receptor, phasic receptor, sensory adaptation
Tonic receptors: Maintain firing of AP during stimulation (Slow adapting); as long stimulus is present
* EX: pain
Phasic receptors: Burst of AP firing but quickly fades (Fast adapting)
— Sensory adaptation: If stimuli constant, sensory receptor ceases to respond
* EX: hot tub (starts off hot, then body adapts)
Describe generator potentials & their effect on action potentials
- Stimulus at sensory endings of sensory receptor
- Lead to local (signal), graded changes in membrane potential (generator potential)
- If it reaches threshold, generator potentials lead to AP
Define receptive fields & describe the relationship between area and density of sensory receptors. How does this apply to the back and legs, and fingertips?
Receptive field: Refers to area of skin around each sensory receptor
* Area varies INVERSELY with density of sensory receptors; more sensory receptors = each receptor is responsible for small area and vice versa
- Back & legs = FEWER number sensory receptors with LARGER receptive fields
- Fingertips = LARGER number sensory receptors with SMALLER receptive fields
* Greater sensory acuity = sharpness of sensation for fingertips
Describe the purpose of the two-point threshold
- Two-point touch threshold: Minimum distance between 2 pts of touch perceived as 2 pts
- Threshold indicates TACTILE ACUITY
- Test: Used to detect approximate size of receptive field for light touch
- Calipers touch skin at same time
Describe the relationship between a region’s two-point touch threshold & its representation on the sensory homunculus
Areas with smaller two-point touch threshold will have greater representation at the brain
Describe the purpose of lateral inhibition
Lateral inhibition: sharpens the sensation by inhibiting interneurons
* When blunt object touches skin, central area stimulated more than lateral fields
* Result: Brain perceives 1 sharp touch
* Ex: Hearing, Vision, Smell
Memorize the details for the neural pathways for somatesthetic sensations
Sensations from proprioceptors (body position) & cutaneous receptors (found in skin) relayed to brain in three neurons:
- 1st order neuron: large, myelinated nerve fibers
* Receptor → SC or medulla oblongata; ipsilaterally
- 2nd order neuron: up & decussate to reach thalamus (gateway to cerebral cortex)
- 3rd order neuron: (at the thalamus) project to postcentral gyrus
Define referred pain
Referred pain: visceral pain mistaken for somatic pain
* Possibly due to visceral & somatic sensory neurons synapsing on SAME interneuron
Identify the components that form the vestibular apparatus
Vestibular Apparatus (2 parts)
1. Three semicircular ducts
2. Otolith organs (Utricle and saccule)
Distinguish endolymph from perilymph
- Endolymph - inner fluid with higher [K+] than other fluids
- Perilymph - surrounding outer fluid with normal [ion]
Describe the information provided by the frequency of action potentials in the hair cells of the vestibular apparatus
Frequency of APs = gives info about direction of movements
Stimulated:
Stereocilia bend TOWARD kinocilium→ K+ channels open → depol. → release MORE chemical messenger → more AP’s in vestibular n. (CNVIII)
Inhibited:
Stereocilia bend AWAY from kinocilium→ hyperpol.→
release less chemical messengers → less AP’s in vestibular n. (CNVIII)
Name the cranial nerve (and number) involved in equilibrium & name the 2 locations in the brain that receives the information from the cranial nerve
Vestibulocochlear nerve (CN VIII)
1. Cerebellum
2. Vestibular nuclei of medulla oblongata
Name the type of information that the utricle vs. saccule vs. all 3 semicircular ducts together vs. each individual semicircular duct detect(s)
- Utricle: for detecting horizontal acceleration
- Saccule: for detecting vertical acceleration
- Semicircular ducts: detecting rotational acceleration
1. Anterior semicircular duct: detects sagittal rotational acceleration
2. Posterior semicircular duct: detects coronal rotational acceleration
3. Lateral semicircular duct: detects horizontal rotational acceleration
Distinguish vestibular nystagmus from vertigo
Vestibular nystagmus: involuntary oscillations of the eye
Vertigo: the loss of equilibrium
Memorize the sequence of structures & spaces of the ear that sound waves travel through to be detected at the spiral organ for low sound waves and high sound waves
- Auricle/Pinna
- External acoustic meatus
- Tympanic membrane
- Malleus
- Incus
- Stapes
- Oval window
- Perilymph of scala vestibuli
- LOW sound waves
- Apex of helicotremma then returns to base via scala tympani
- Round window and sound dies
OR
9. HIGH sound waves
10. Vestibular memebrane
11. Cochlear duct/Scala media (with endolymph)
12. Basilar membrane (to scala tympani)
Distinguish the location on the basilar membrane where high vs. low vs. moderate pitch sounds are detected
- Base for high pitch/frequency
- Apex for low pitch/frequency
- Middle for pitches/frequencies in between
Describe the process of how vibrations in the perilymph of the scala vestibuli lead to the generation of action potentials in the sensory neuron of cranial nerve VIII
As basilar membrane moves towards tectorial membrane, K+ channels open → depol. in inner hair cell → release glutamate → depol. in sensory neuron of CNVIII → AP’s
Describe how louder sounds are detected & how they influence action potential generation
Louder sounds
* Causes GREATER bending of basilar membrane & stereocilia →↑ chemical messenger → ↑ generator potentials in sensory neuron →↑ number of APs
Memorize the entire pathway (4) that information about SOUND travels through after leaving the spiral organ of the cochlea
- Sensory neuron in CN VIII
- Inferior colliculus: for auditory reflexes
- Medial geniculate body of thalamus
- (Temporal lobe) Primary auditory cortex and auditory association area: to interpret
Distinguish the function of the inferior colliculus vs. primary auditory cortex vs. auditory association area
Inferior colliculus: for auditory reflexes (turning our head to hear that sound)
Primary auditory cortex: to interpret
Auditory association area: to interpret
Define tonotopic organization
Tonotopic organizations: Different regions of the ear represent different pitches
Distinguish sensorineural hearing loss from conductive hearing loss
Sensorineural hearing loss: Impaired AP’s from cochlea to auditory cortex
- Impairs SOME pitches to others
- Solution - Cochlear implants
Conductive hearing loss: Impaired SOUND WAVES from outer and middle ear to oval window
- Impairs ALL sound frequencies
- Solution: Hearing aids
Memorize the sequence of structures, substance & spaces of the eye that light waves travel through to be detected at the retina
- Cornea
- Aqueous humor of anterior cavity
- Pupil
- Lens
- Vitreous humor or vitreous chamber
- Retina
How is image projected onto each retina? Distinguish the portions of the visual field that focus on the left half vs. right half of each retina
- Image projected onto each retina is INVERTED and REVERSED
- Cornea and lens:
— Focus R-half of field of vision onto L-half of each retina = L eye temporal (lateral) half & R eye nasal (medial) half
— Focus L-half of field of vision onto R-half of each retina = L eye medial half & R eye lateral half
Name the cells & structures that the retina consists of
- Retinal pigment epithelium
- Photoreceptors (rods and cones)
- Bipolar cells and ganglion cells
Distinguish the direction of incoming light from the direction of neural activity
Incoming light:
Cornea ➡ Aqueous humor of anterior cavity ➡ Pupil ➡ Lens ➡ Vitreous humor of posterior cavity ➡ Retina (ganglion cells, bipolar cells, photocreceptors) ➡ Choroid
Neural activity:
Photoreceptors ➡ Bipolar cells ➡ Ganglion cells ➡ Optic nerve ➡ Optic chiasma ➡ Optic tract…
➡ (Some;30%) Superior colliculi
OR
➡ (Most;70%)Thalamus ➡ Optic radiations ➡ Primary visual cortex ➡Visual association area
Memorize the details of the bleaching reaction
- Once light enters eyes, rods activated during the bleaching reaction
- Light absorbed by rhodopsin @ outer segment
- CIS-retinal (while attached to opsin) becomes TRANS-retinal (free)
- Trans-retinal splits from opsin
- Changes rod’s ion permeability → NO generator potential = neurotransmitters can’t be released
Memorize the details of the interactions among retinal cells in the dark
In the DARK:
* Rods & cones: Na+ channels in their cell membrane OPEN → Na+ in (called DARK CURRENT) → Slight depol. (excited)
* → Rod cells release inhibitory neurotransmitters → IPSP in bipolar cells → No neurotransmitters from bipolar cell to ganglion cell, so NO AP’s in ganglion cell
Memorize the details of the interactions among retinal cells when there is light
When there is LIGHT:
* Rods & cones: Na+ channels in their cell membrane CLOSE → LESS Na+ in = LESS dark current → Hyperpol. (inhibited)
* → no inhibitory neurotransmitters released→
Bipolar cells free to release excitatory neurotransmitters
→EPSP in ganglion cell→ AP’s in optic n. (ganglion cell’s axon)
Name the specific structure that forms the optic nerve
Ganglion cell’s axon
Describe the steps involved in producing the dark current
In the DARK, cGMP keeps Na + channels open by binding to it → Na in → dark current
Describe how light causes the stopping of the dark current
When there is light, trans-retinal formed & leaves opsin, opsin changes shape
- Opsin’s G protein is released and activates an enzyme (Phosphodiesterase), which turns cGMP into GMP, CLOSING Na+ channels
Name the photoreceptor cell that the fovea centralis contains & describe the 2 consequences of having this type of cell here
Contains ONLY CONES
1. Greatest visual acuity
2. Poorest sensitivity to low light
Memorize the entire pathway that information about light travels through after leaving the optic nerve
Optic chiasma
- Some decussate (medial side) @ optic chiasma vs. others stay ipsilateral (lateral side)
→ Optic tract
Distinguish the function of the superior colliculus vs. primary visual cortex vs. visual association area
- Superior colliculus: For visual reflexes; “Where is it?”
— SOME from optic tract (~30%) ; turn our head for what we see - Primary visual cortex: Makes us aware that we are looking something
- Visual association area: To interpret; “What is it?”
Define accommodation
Accommodation: Ability of eye to keep images focused on retina as distance between eyes & the object varies
Describe the details of accommodation when a person focuses on a distant vs. close object (focus on the ciliary muscle, tension on suspensory ligaments & lens convexity)
Distant (≥ 20 ft)
1. Ciliary m. relax
2. Causes tension on suspensory ligaments
3. Pulls on lens & makes it least convex (thinner)
Close:
1. Ciliary m. contract (NOT constrict)
2. Reduces tension on suspensory ligaments
3. Lens most convex (thicker)
Describe the pupillary reflex vs. when the eye is in dim light (focus on the iris muscles & division of the autonomic nervous system involved in each)
Pupillary reflex AKA consensual light reflex: shine light into 1 eye, both pupils constrict
- Coordinated by superior colliculi of midbrain
- From oculomotor nerve, synapse on ciliary ganglion, with postganglionic PARASYMPATHETIC axon = circular smooth m. constrict
Eye in dim light:
- From superior cervical ganglion to the postganglionic SYMPATHETIC axon = radial smooth m. dilates
Describe the purpose of proprioceptors & name 2 examples of proprioceptors
Purpose of proprioceptors: provide continuous sensory feedback (helps control skeletal muscle movements)
- EX: Golgi tendon organs and muscle spindles
Distinguish the function of Golgi tendon organs from muscle spindles
Golgi tendon organs: monitor tension on tendons
Muscle spindles: monitor muscle length
Distinguish alpha motor neurons from gamma motor neurons in terms of control (voluntary vs. Involuntary), muscle fiber type innervated & relative speed
Alpha (α) motor neuron
* Voluntary
* Innervate extrafusal fibers
* Relatively faster speed
Gamma (γ) motor neuron
* Involuntary
* Innervate intrafusal fibers
* Relatively slower speed
Name the initial precursor molecule used to synthesize all steroid hormones & identify the chemical nature of that precursor molecule (polar or non-polar)
Cholesterol; non-polar
Distinguish the 3 types of hormone interactions (& if applicable, their subtypes) & recognize examples of each type/subtype
- Antagonistic effect: action of 1 hormone opposes effects of another hormone
- EX: Insulin (synthesis) vs glucose (breakdown of adipose tissue) - Permissive effect: 1st hormone enhances responsiveness of target organ to 2nd hormone or ↑ activity of 2nd hormone
- Ex: Prior exposure to estrogen causes ↑ # receptors for progesterone (uterus) = stronger response - Synergistic effect: ≥ 2 hormones work together
a. Additive: alone, each hormone produces response; but together→ greater effect
- EX: Epinephrine and Norepinephrine on HR
b. Complementary: each hormone produces different step in the target cell’s response
- EX: Estrogen + Cortisol + Prolactin + Oxytocin on lactation
Name the 3 locations that remove hormones from the circulation
- Target tissue
- Liver
- Kidneys
Describe the half-life for most hormones
Half-life: Time [hormone] in plasma reduced to 1⁄2
- Most: minutes to hours
Distinguish upregulation from downregulation
Upregulation: ↑ # receptors on target cells, leading to a STRONGER response
Downregulation: ↓ # receptors on target cells, leading to a WEAKER response