BIOSC 1250 - EXAM #2

Visual input

Goes into opposite side of visual cortex; a fraction will go into the same lobe

Depth perception

Both eyes receive visual input from left and right visual fields (horses don't have good depth perception bc eyes on side, no overlap)

Allowed by optical chiasm/crossing

Damage to optic nerves, chiasm or tracts

See pp. 234

External Ear - Components

Pinnea, external auditory canal, tympanic membrane

Pinnea

Collects sound waves and conveys to external auditory canal

Tympanic membrane

The eardrum. A structure that separates the outer ear from the middle ear and vibrates in response to sound waves. Conveys sound waves to middle ear

Middle ear - Components

Oval and round windows, auditory ossicles (malleus, incus, stapes), tensor tympani muscle, stapedius musclle

Oval Window

membrane that covers the opening between the middle ear and inner ear

Affects tectorial membrane to begin sound wave transmission

Round Window

A membrane-covered opening in the inner wall of the middle ear that compensates for changes in cochlear pressure.

Where sound wave dissipates; last step of transmission of sound waves

Malleus

hammer; first of the three auditory ossicles of the middle ear

Incus

anvil; middle of the three auditory ossicles of the middle ear

Stapes

stirrup; last of the three auditory ossicles of the middle ear

Primary function of auditory ossicles

Transmit and amplify vibrations from tympanic membrane to oval window

Tensor tympani muscle and stapedius muscle

2 skeletal muscles in the middle ear that contract reflexively to protect the structures of the inner ear from loud noise

Tempor tympani taut to loose depending on vibration

Inner ear components

cochlea, vestibule, semicircular canals, perilymph fluid

Divided into two components - bony labyrinth and membranous labyrinth

Cochlea

Sense organ for hearing

3 channels:

-Cochlear duct---Basilar Membrane--Scala Tympani---Scala vestibuli

basilar membrane

separates the cochlear duct from the scala tympani; contains organ of corti

Organ of corti

Contains hair cells (1 row of inner hair cells, 3 rows of outer)

Inner hair cells

Responsible for transducing vibrations to electrical signals

stereocilium

any of the hairlike extensions on the tips of hair cells in the cochlea that, when flexed, initiate the release of neurotransmitters

Tip link

a tiny filament that stretches from the tip of a stereocilium to the side of its neighbor

Like a chain stopper

Sound Transduction

Inner hair cells brush against each other as they are vibrated. Mechanically gated ion channels open and primarily K+ flows into hair cell causing depolarization. VG calcium channels open, diffuse inside and use exocytosis to pop NT. When hair cells are at rest, these channels are weakly open, causing weak/low freq APs. When they are vibrated/activated, there are high APs since the channels are fully open. However, if a vibration brushes the hairs to the right instead, the channels close completely to cause hyperpolarization and minimal APs.

Outer hair cells

Enhance sensitivity of inner hair cells

Hair cell innervation

-Innervations from sensory and motor neurons of the cochlear branch VIII nerve

-Sensory neurons synapse with inner hair cells

-Motor neurons synapse with outer hair cells

Vestibule

Sense organ for equilibrium

Capula

A gelatinous cap that extends from the crista to the roof of the ampulla where the stereocilia and a kinocilium of it are embedded.

Rotate head: the drag of the endolymph causes the cupula and embedded hairs to bend in opposite direction

Semicircular ducts

detect rotational acceleration or deceleration; use capula

Meniere's disease

Abnormal buildup of endolymph that enlarges the membranous labyrinth

Semicircular canals

Sense organ for equilibrium

Make 90 degree angles with each other

Contain ducts that have hair cells that project into capula

Contain lymph fluid, enables vestibular system to know if your head moves at all

Membraneous labyrinth

Divison of inner ear that contains utricle and saccule

Pitch/tone

determined by frequency of vibrations

Intensity

Determined by amplitude/size

Pitch discrimination

Depends on which region of the basilar membrane vibrates; each portion has hair cells and auditory neurons tuned to particular pitch/frequency

Loudness discrimination

Depends on how much the basilar membrane vibrates

High intensity = more vibration = fully open K+ channels = high AP = brain interpreting as loud sound

Utricle

Contain hair cells/receptors for linear acceleration/deceleration and position of head/tilt - HORIZONTAL, like in a car, or tilting your head forward and back (contained in maculae)

Saccule

Contain hair cells/receptors for linear acceleration/deceleration and position of head/tilt - VERTICAL, like in an elevator (contained in maculae)

Macculae

Fused to inner walls of utricle and saccule; contain the receptors for acc/dcc, tilt

Otholithic membrane

Hair cells of utricle and saccule project into; contains otholiths/'stones'

Positional vertigo

Otoliths get loose/float

Otoliths

small crystals in the fluid-filled vestibular sacs of the inner ear that, when shifted by gravity, stimulate nerve cells that inform the brain of the position of the head

Auditory Pathway

Hair cells of cochlea --> cochlear branch of VIII nerve --> brain stem --> thalamus --> cerebral cortex

Within cochlear branch: info goes into cochlear nuclei and then into olivary nucleus

Cochlear nuclei

brainstem nuclei that receive input from auditory hair cells and send output to the superior olivary complex

Olivary nucleus

a collection of nuclei in the medulla and pons that is the first site where auditory information from the right and left ears converges

inferior colliculi

auditory reflex center

Equilibrium pathway

hair cells of utricle/saccule/semicircular ducts --> vestibular branch of vestibulocochlear nerve --> brain stem --> cerebellum --> thalamus --> cerebral cortex

Lower than hearing pathway

Nervous System - 2 divisions

central nervous system and peripheral nervous system

Central Nervous System

contains the brain and spinal cord

Peripheral Nervous System

the sensory and motor neurons that connect the central nervous system to the rest of the body; cranial nerves, sacral nerves

Peripheral Nervous System Divisions

afferent (sensory)- carry impulses to CNS

efferent (motor)- carry impulses to effector organs

-somatic motor NS

-visceral motor (autonomic) NS

>sympathetic (fight or flight)

>parasympathetic (rest & digest)

Afferent PNS

carries sensory info to CNS

Efferent PNS

Carries motor commands away from the CNS

Contains somatic nervous system and autonomic nervous system

Autonomic nervous system contains

sympathetic and parasympathetic nervous system

enteric nervous system (gi)

Regulates smooth, cardiac muscle and glands; visceral organs

Most organs receive dual innervation...

From Sympa and Parasympa systems

Sympathetic nervous system (SNS) effects

Fight or flight

Dominates the PNS during emotional or physical stress

Pupils dilate, heart rate, BP, and more increase

"E" = excite, emergency, exercise, embarassment

SNS has longer responses because...

-Motor pathways diverge to more effectors

-NE is deactivated more slowly than ACh

-NE from the adrenal inceases the effect of NE from neurons

-Systemic via blood vessels

What deactivates ACh?

AChE (acetylcholinesterase)

Parasympathetic Nervous System (PNS) effects

Rest and digest

SLUDD - Salvation, Lacrimination, Urination, Digestion, Defecation

Decreases heart rate, diameter of broncial tubes and pupils.

The autonomic nervous system regulates...

smooth muscle, cardiac muscle, glands (visceral effectors)

Dual innervation

most viscera receive nerve fibers from both parasympathetic and sympathetic divisions

Autonomic motor pathways are comprised of...

Two autonomic motor neurons and a visceral effector

Go to adrenal medulla

First order neuron of ANS

Preganglionic neuron

Preganglionic neuron

Cell body located within brain or spinal cord; axot exits via cranial or spinal nerve and extends to (bringing AP) an autonomic ganglion

Where do sympathetic nerves originate?

thoracic and lumbar

Craniosacral system

Parasympathetic

Thoracolumbar system

Sympathetic

What cranial nerves do preganglion neurons exit through? (parasympathetic)

3, 7, 9, 10, 11

Autonomic ganglion

where the preganglionic and postganglionic neurons meet and communicate; located in the PNS

NT produced

Postganglionic neuron

Lies entirely within PNS; cell body within autonomic ganglion; axon extends to visceral organ

-Axon lacks end bulbs; rather, it has swollen varicosities that contain synaptic vesicles carrying neurotransmitter

Second order neuron of ANS

Postganglionic neuron

Varicosities

Where AP arrives

Parasympathetic pre-ganglion --> post

Long axon --> short axon (ACh --> ACh)

The Neuroeffector Junction (NEJ)

the synapse between a postganglionic autonomic neuron and its target cell (visceral effector)

-Where NT released (SEE MECHANISM ON SG)

- where ANS nerve communicates with a visceral organ

Sympathetic preganglion neurons --> post

Short axon --> long axon (ACh --> NE)

Receptors for neurotransmitters in ANS

Located all over surface of target region/visceral effector

ANS receptors

cholinergic and adrenergic

Cholinergic receptors

Release ACh

Present in ALL PNS and SNS preganglionic neurons

Present in MOST PNS postganglionic neurons

ACh diffuses through synaptic cleft to find receptor

Types of Chlorinergic receptors

Nicotinic and Muscarinic

Ionotrophic

Nicotinic ACh Receptors

Present in membrane of dendrites and cell bodies of both PNS and SNS postganglionic neurons (along with all skeletal muscle at the NMJ)

Adrenal medulla

Contains a cation channel and two ACh binding sites

Muscarinic ACh receptors

G-protein receptor (slower)

Present in the membrane of effectors/on target tissues of parasympathetic nervous system

Innervated by PNS postganglionic axons

Limited in the sympathetic system to sweat glands

Atropine

Drug that blocks muscarinic ACh receptors

Dilates pupils/pupil muscles don't contract

Can also reduce glandular secretions, relax smooth muscle in GI tract

Adrenergic Receptors

Respond to norepinephrine (NT/hormone) or epinephrine (hormone)

In most SNS postganglionic neurons

Consist of A1, A2, B1, B2, B3

Metabotropic receptors that trigger 2nd messenger pathways by coupling to Gprots

Adrenergic NTs

NE - released by postganglionic cells of sympathetic nervous system (as a NT), or adrenal medulla (as a hormone carried by blood supply)

EP - Releazsed by chromaffin cells of adrenal medulla

chromaffin cells

the cells in the adrenal medulla that secrete epinephrine and norepinephrine

Adrenergic Rs - alpha vs beta

Alpha - smooth muscle contraction/vasoconstriction (increasing BP)

Beta - increased heart rate, vasodilation, kidney, adispose tissue

A1, B1 - Stimulate

A2, B2 - Inhibit

Dual innervation (A and B on same organ)

Alpha 1 receptors

NE > E

Alpha 2 receptors

NE > E

Beta 1 receptors

NE = E

Beta 2 receptors

NE < E

Beta 3 receptors

NE > E

Autonomic reflexes

Help maintain homeostasic

Involuntary responses that occur when APs pass through autonomic reflex arcs

Ie pee, digestion, poop

Autonomic reflex arc components

receptor

sensory neuron

integrating center

motor neurons

effector

Autonomic control centers

Present in brain (brain stem and hypothalamus) and spinal cord

Cardiovascular

Respiratory

Etc

Dual innervation of iris

Sympathetic/adrenergic effect - pupil dilated (dilator pupillae contracts)

Parasympathetic/cholinergic effect- pupil constricted (sphincter pupillae contracts)

ANS - Autonomic Tone

Regulated by hypothalmus; regulates your reaction to threat (hypothalmus tells stomach no time for digestion, we need to run, blood supply must go to muscles)

Body organs receive constant innervation by both branches; one will turn up while the other turns on

Raynaud Phenomenon***

Vasoconstriction in fingers and toes

Paleness, cyanosis, and pan in digits when cold or stressed due to excessive sympathetic stimulation of smooth muscle in arterioles

Treated with vasodilators and Ca++ channel blockers

Somatic Nervous System

the division of the peripheral nervous system that controls the body's skeletal muscles - voluntary

Somatic motor pathways are comprised of...

A somatic motor neuron from the CNS and a skeletal muscle

Neuromuscular Junction (NMJ)

Synapse formed between somatic motor neuron and skeletal muscle

The motor neuron's axon contains bulbs that have vesicles filled with ACh

ACh and NMJ

ONLY NT of somatic motor pathways

ACh --> Sk. m. --> Nicotonic Receptors --> Contraction

Excites the NMJ --> Muscle contraction

Motor end plate

Region of muscle fiber plasma membrane opposite to end bulbs/separates cleft from end bulbs

Contains ACh nicotinic receptors

Muscle membrane