Physiology Exam Study Material for INB365s by Cheng

Graded potential (characteristics, locations, and ion channels)

variable-strength signals that travel over short distances and lose strength as they travel through the cell; short distance communication; occurs in dendrites/cell body; mechanically, chemically, or voltage-gated channels, depolarizing (Na+) or hyperpolarizing (Cl-) signal

Action potential (characteristics, locations, and ion channels)

very brief, large depolarizations, travel for long distances without losing strength; occur in trigger zone through axon; voltage-gated channels

Membrane proteins and ion distributions when a resting membrane potential is reached

Higher Na+ outside, K+ higher inside and the cell is ready to do work (has potential energy)

Leak channels for K+ to exit the cell, sodium channels limit Na+ from coming in, Na+/K+ pump lets out 3 Na+ and in 2 K+ to make inside of cell slightly -

Temporal summation

summation that occurs from graded potentials overlapping in time and may initiate an action potential

Spatial summation

occurs when the currents from nearly simultaneous graded potentials combine and arrive at trigger zone together to create a suprathreshold signal and generate an action potential

5 Mechanisms to trigger NTs release in the axon terminal

- An action potential depolarizes the axon terminal

- The depolarization opens voltage-gated Ca2+ channels, and Ca2+ enters the cell

- Calcium entry triggers exocytosis of synaptic vesicle contents

- Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell

- Neurotransmitter binding initiates a response in the postsynaptic cell

EPSP (excitatory postsynaptic potential)

depolarization that makes the cell more likely to fire an action potential by increasing membrane potential

IPSP (inhibitory postsynaptic potential)

hyperpolarization (moves it away from membrane potential threshold) that makes the cell less likely to fire an action potential

What is all-or-none?

action potentials are called this because it only fires at maximum depolarization or not at all

Function of frontal lobe

skeletal muscle movement, decision making (prefrontal cortex)

Function of parietal lobe

sensory information from skin, musculoskeletal system, viscera, taste buds

Function of occipital lobe

vision

Function of temporal lobe

hearing, smell, learning, memory

Brain areas associated with movement control

motor cortex (frontal lobe), cerebellum, basal ganglia (parkinsons), thalamus, brainstem

Brain areas associated with pain perception

spinal cord, thalamus

Special sense receptors vs. general sense receptors

Special sense: specialized receptors confined to structures in the head (eyes, ears, nose, and mouth)

General sense: receptors that are widely distributed throughout the body (skin, various organs, and joints)

Compare receptors with big and small receptive fields.

Big receptive fields: big fields overlap (convergence) and allows simultaneous subthreshold stimuli to sum and initiate an action potential

Small receptive field: fewer neurons overlap and allow for low convergence, which helps distinguish the two different stimuli

Compare rods and cones

Rods: big receptive fields, used for night vision

Cones: small receptive fields, used for bright light

explain signal transduction of rods/cones

- In darkness, rhodopsin is inactive, cGMP is high, and CNG and K+ channels are open (depolarized)

- light bleaches rhodopsin, opsin decreases cGMP, closes CNG channels, and hyperpolarizes the cell (hyperpolarized)

- In the recovery phase, retinal combines with opsin to reform rhodopsin

visible light --> rhodopsin --> lower cGMP --> CNG channels close --> hyperpolarization of cell --> lower transmitter

what is dark current?

the flow of ions in photoreceptor cells (specifically rods and cones) in the retina of the eye in the absence of light

Sound transduction and frequency coding in the auditory system

- sound wave represents alternating areas of high and low pressure

- tympanic membrane vibrates in response to sound wave

- vibrations are amplified across ossicles

- vibrations against oval window set up standing wave in fluid of vestibuli

- pressure bends the cochlear duct membrane for each given frequency which causes hair cells in the basilar membrane to vibrate

How do the sensory receptors distinguish the 4 properties of a stimulus?

Modality (type), location, intensity, duration

Quick adapting vs. slow adapting receptors.

- tonic receptors are slowly adapting receptors that respond for the duration of a stimulus (pain, there but subsides after a while)

- phasic receptors rapidly adapt to a constant stimulus and turn off (smell, get used to it even if it's still there)

Vestibular sense and its signal transduction

balance!

endolymph (fluid) moves through the canals that corresponds to the plane of head movement, fluid moves into the ampulla where hair cells are moved by the endolymph, this movement releases neurotransmitters to signal the brain; otolith organs in the labyrinth detect gravitational forces and can also move hair cells

Gustatory sensation

taste!

sweet, sour, bitter, salty, umami --> taste + smell = flavor

Adrenal gland

sits atop our kidneys, sympathetic nervous system, secretes epi into the blood for stress response

Sympathetic vs. parasympathetic systems. Functions, pre- and post-ganglia structures, and locations in the spinal cord

sympathetic = fight or flight

- T1-L2 (whole thing) with long fibers that reach to target organs

parasympathetic (rest and digest)

- just the top and bottom with short fibers that reach target organs

Control centers of ANS

hypothalamus, pons, medulla

Dual innervation + examples

organ or tissue is innervated by both the sympathetic and parasympathetic divisions of the autonomic nervous system; likely with opposite effects

i.e. heart rate has dual innervation while sweat glands are only controlled by the sympathetic system

Sweat gland

The glands that secrete sweat, located in the dermal layer of the skin. Only sympathetic pathway, ACh to nicotinic to Muscarinic

Voltage-Gated Na+ Channels (neuron location)

axon hilock/axon

Voltage-Gated K+ Channels (neuron location)

axon hilock/axon

Voltage-Gated Ca2+ Channels (neuron location)

axon terminal (release neurotransmitters)

Ligand-Gated Na+ Channels (neuron location)

mostly in dendrites but also soma

Ligand-Gated K+ Channels (neuron location)

mostly in dendrites but also soma

Ligand-Gated Ca2+ Channels (neuron location)

NONE

Match event to the correct location of neuron: EPSP

mostly dendrites but soma

Match event to the correct location of neuron: IPSP

mostly dendrites but soma

Match event to the correct location of neuron: action potential

axon hilock/axon

Match event to the correct location of neuron: saltatory conduction

axon

Match event to the correct location of neuron: continuous conduction

NONE

Match event to the correct location of neuron: exocytosis

axon terminal

basal nuclei

influences muscle activity, inhibits unnecessary motor movements, coordinates slow sustained contractions

medulla oblongata

vital reflex centers: cardiac, vasomotor, respiratory, regulates ANS activities

Hypothalamus

regulates ANS activities, biological clock, body temp, food intake, regulates water balance, controls several major endocrine functions

Pons

regulates ANS activities

Thalamus

edits sensory information which is passed on to cerebral cortex relays motor signals coming out of cerebral cortex, receives and processes sensory information from receptor pathways w spinal cord, perception

cerebral cortex

memory, integration, interpretation, discrimination, localization; language

spinal cord

major reflex centers, receives and processes sensory information from receptor pathways w thalamus, perception, reticular activating system; also involved in motor and visceral activities

limbic system

functional system responsible for emotional behavior

midbrain

involved in eye reflexes, pupillary, consensual response, blinking

simple sensory receptors

only sense pain, free nerve endings

complex sensory receptors

specialized structure, detects pressure and touch, myelinated axons

special senses

light, sound, and chemical molecules--> causes depolarization to release neurotransmitters (hearing, taste, smell, sight)

sympathetic A1

reduced blood flow

sympathetic A2

GI tract and pancreas

sympathetic B1

increased heart rate

sympathetic B2

bronchodilation