Bio214 Exam #4 Part 2

Autonomic nervous system (ANS)

\-a motor nervous system that controls glands, cardiac muscle, and smooth muscle 

\-also called visceral motor system

What are the primary organs of the ANS?

\-viscera of thoracic and abdominal cavities

\-some structures of the body wall

* cutaneous blood vessels
* sweat glands
* piloerector muscles

The ANS carries out involuntary or voluntary actions?

involuntary (without conscious intent or awareness)

Denervation hypersensitivity

exaggerated responses of cardiac and smooth muscle if autonomic nerves are severed

Visceral reflexes

unconscious, automatic, stereotyped responses to stimulation involving visceral receptors and effectors

Receptors

nerve endings that detect stretch, tissue damage, blood chemicals, body temperature, and other internal stimuli

Afferent neurons

lead to CNS

Integrating center

interneurons in the CNS

Efferent neurons

carry motor signals away from CNS

Effectors

carry out end response

Sympathetic division

Prepares body for physical activity: exercise, trauma, arousal, competition, anger, or fear

* Increases heart rate, BP, airflow, blood glucose levels, etc.
* Reduces blood flow to the skin and digestive tract
* “Fight-or-flight”

Parasympathetic division

Calms many body functions reducing energy expenditure and assists in bodily maintenance

* Digestion and waste elimination
* “Resting and digesting” state

Autonomic tone

\-normal background rate of activity that represents the balance of the two systems according to the body’s needs

\-parasympathetic tone

\-sympathetic tone

Parasympathetic tone

\-maintains smooth muscle tone in intestines

\-holds resting heart rate down to about 70 to 80 beats per minute

Sympathetic tone

keeps most blood vessels partially constricted and maintains blood pressure

ANS contracts to…

somatic motor pathway

Somatic pathway characteristics

A motor neuron from brainstem or spinal cord issues a myelinated axon that reaches all the way to skeletal muscle

Autonomic pathway characteristics

* Signal must travel across two neurons to get to the target organ


* Must cross a synapse where these two neurons meet in an autonomic ganglion
* Presynaptic neuron: the first neuron has a soma in the brainstem or spinal cord
* Synapses with a postganglionic neuron whose axon extends the rest of the way to the target cell

Sympathetic division characteristics

* Relatively short preganglionic and long postganglionic fibers


* Preganglionic neurosomas in lateral horns and nearby regions of spinal cord gray matter 
* Fibers exit spinal cord by way of spinal nerves T1 to L2
* Lead to nearby **sympathetic chain of ganlia** (paravertebral ganglia)
* preganglionic fibers
* postganglionic fibers

Preganglionic fibers

small myelinated fibers that travel from spinal nerve to the ganglion by way of the white communicating ramus (myelinated)

Postganglionic fibers

leave the ganglion by way of the gray communicating ramus (unmyelinated)

What are the three courses the postganglionic fibers may follow after entering the sympathetic chain?

1. Some end in __**ganglia**__ which they enter and synapse immediately with a postganglionic neuron
2. Some travel up or down the chain and synapse in ganglia at other levels
3. Some pass through the chain without synapsing and continue as splanchnic nerves

Adrenal cortex

\-outer layer

\-secretes steroid hormones

Adrenal medulla

\
\-inner core

\-Essentially a sympathetic ganglion consisting of modified postganglionic neurons (without fibers)

\-Secretes a mixture of hormones into bloodstream

* Catecholamines—85% epinephrine (adrenaline) and 15% norepinephrine (noradrenaline)

What are the origins of the long preganglionic neurons?

\-midbrain

\-pons

\-medulla

\-sacral spinal cord segments S2 to S4

The parasympathetic nervous is relatively ___ in stimulation of target organ

selective

Enteric nervous system

* the nervous system of the digestive tract 
* Innervates smooth muscle and glands


* Composed of 100 million neurons found in the walls of the digestive tract
* What Has its own reflex arcs

Does the enteric nervous system have any CNS components?

no

What does the enteric nervous system regulate?

motility of esophagus, stomach, and intestines and secretion of digestive enzymes and acid

Normal digestive function also requires…

regulation by sympathetic and parasympathetic systems

Hearing

a response to vibrating air molecules

Equilibrium

the sense of motion, body orientation, and balance

Where do both hearing and equilibrium reside in?

the inner ear, within a maze of fluid-filled passages and sensory cells

Sound

any audible vibration of molecules

How does sound work?

* A vibrating object (e.g., tuning fork) pushes on air molecules


* These, in turn, push on other air molecules
* Air molecules hitting eardrum cause it to vibrate

Pitch

\-our sense of whether a sound is “high” or “low”

\-determined by vibration frequency (Hz)

Loudness

\-the perception of sound energy, intensity, or amplitude of the vibration

\-expressed in decibels (dB)

How many sections does the ear have?

3

\-outer

\-middle

\-inner

What are the first two sections of the ear only concerned with?

the transmission of sound to the inner ear

Inner ear

vibrations converted to nerve signals

Outer ear

a funnel for conducting vibrations to the tympanic membrane (eardrum)

* Auricle (pinna) directs sound down the auditory canal
* Shaped and supported by elastic cartilage
* Auditory canal (external acoustic meatus): passage leading through temporal bone to tympanic membrane
* Guard hairs protect outer end of canal

External acoustic meatus of the outer ear

passage leading through temporal bone to tympanic membrane

* guard hairs protect outer end of canal
* Cerumen

Cerumen

earwax, mixture of secretions of ceruminous and sebaceous glands and dead skin cells

Middle ear

located in the air-filled tympanic cavity in temporal bone 

* Tympanic membrane (eardrum) closes the inner end of the auditory canal (separates it from middle ear)
* Vibrates freely in response to sound
* Tympanic cavity is continuous with mastoid air cells
* Contains auditory ossicles
* Auditory (eustachian) tube connects middle-ear to nasopharynx
* Auditory ossicles

Auditory (eustachian) tube functions

\-equalizes air pressure on both sides of the tympanic membrane

\-normally closed, but swallowing or yawning open it

\-allows throat infections to spread to middle ear

What are the different auditory ossicles?

\-Malleus

\-Incus

\-Stapes

Malleus

has long handle attached to inner surface of tympanic membrane

Incus

articulates with malleus and stapes

Stapes

shaped like a stirrup; footplate rests on oval window-where inner ear begins

Otitis media

\-middle-ear infection

\-common in children due to horizontal auditory tube (for drainage)

Bony labyrinth

passageways in temporal bone

Membranous labyrinth

\-fleshy tubes lining bony labyrinth

\-filled with endolymph (similar to ICF)

\-floating in perilymph (similar to CSF)

Labyrinth

vestibule and three semicircular ducts

Cochlea

organ of hearing

What are the three fluid-filled chambers within the cochlea?

\-Scala vestibuli

\-Scala tympani

\-Scala media

Scala vestibuli

* superior chamber 


* Filled with perilymph
* Begins at oval window and spirals to apex

Scala tympani

* inferior chamber 


* Filled with perilymph
* Begins at apex and ends at round window
* Secondary tympanic membrane: covers round window

Scala media (cochlear duct)

* middle chamber


* Filled with endolymph
* Contains spiral organ—organ of Corti: acoustic organ that converts vibrations into nerve impulses

Spiral organ

* has epithelium composed of hair cells and supporting cells


* Hair cells have long, stiff microvilli called stereocilia on apical surface
* Gelatinous tectorial membrane rests on top of stereocilia
* Spiral organ has four rows of hair cells spiraling along its length

Spiral organ inner hair cells

\-single row of about 3500 cells

\-provides for hearing

Spiral organ outer hair cells

\-three rows of about 20000 cells

\-adjusts response of cochlea to different frequencies

\-increases precision

What is the main purpose of sterocilia?

to allow us to zero in on the location of sound

Tympanic membrane

* Has 18 times area of oval window


* Ossicles concentrate the energy of the vibrating tympanic membrane on an area 1/18 that size
* Ossicles create a greater force per unit area at the oval window and overcome the inertia of the perilymph
* Ossicles and their muscles have a protective function
* Lessen the transfer of energy to the inner ear

Step 1 to stimulation of cochlear hair cells

Stretchy protein filament (**tip link**) connects ion channel of one stereocilium to the sidewall of the next

Step 2 to stimulation of cochlear hair cells

Tallest stereocilium is bent when basilar membrane rises up toward tectorial membrane

Step 3 to stimulation of cochlear hair cells

pulls on tip links and opens ion channels

Step 4 to stimulation of cochlear hair cells

K+ flows in —depolarization causes release of neurotransmitter

Step 5 to stimulation of cochlear hair cells

Stimulates sensory dendrites and generates action potential in the cochlear nerve

What causes vibration of the basilar membrane?

vibration of the ossciles

What causes variations in the intensity of cochlear vibrations?

variations in loudness (amplitude)

What does pitch depend on?

which part of the basilar membrane vibrates

When does the brain interpret a signal as high-pitched?

when the vibration is at the basal end with membrane attached, narrow and stiff

When does the brain interpret a signal as low-pitched?

when the vibration is at the distal end, 5 times wider and more flexible

Deafness

hearing loss

Conductive deafness

conditions interfere with transmission of vibrations to inner ear

Otosclerosis

fusion of auditory ossicles that prevents their free vibration

Sensorineural (nerve) deafness

\-death of hair cells or any nervous system elements concerned with hearing

\-common in factory workers, construction workers, musicians

Equilibrium

coordination, balance, and orientation in three-dimensional space

Vestibular apparatus

* constitutes receptors for equilibrium


* Three semicircular ducts
* Detect only angular acceleration (dynamic equilibrium)
* Two chambers
* Anterior saccule and posterior utricle

What are the two chambers responsible for in the vestibular apparatus?

static equilibrium and linear acceleration

Static equilibrium

the perception of the orientation of the head when the body is stationary

Dynamic equilibrium

perception of motion or acceleration 

* Linear acceleration
* Angular acceleration

Linear acceleration

change in velocity in a straight line (elevator)

Angular acceleration

change in rate of rotation (car turns a corner)

Macula

a 2 by 3 mm patch of hair cells and supporting cells in the saccule and utricle

* macula sacculi
* macula utriculi

Macula sacculi

lies vertically on wall of saccule

Macula utriculi

lies horizontally on floor of utricle

Kinocilium

true cilium

Otoliths

calcium carbonate–protein granules that add to the weight and inertia and enhance the sense of gravity and motion

What happens with a static equilibrium?

when head is tilted, heavy otolithic membrane sags, bending the stereocilia and stimulating the hair cells

What happens with a dynamic equilibrium?

* in car, linear acceleration detected as otoliths lag behind, bending the stereocilia and stimulating the hair cells


* Because macula sacculi is nearly vertical, it responds to vertical acceleration and deceleration

What detects rotary movements within the ear?

three semicircular ducts

What is each semicircular duct filled with?

endolymph

Ampulla

dilated sac that each duct opens up as

Crista ampullaris

Consists of hair cells with stereocilia and a kinocilium buriedin a mound of gelatinous membrane called the cupula(one in each duct)

Vision (sight)

perception of objects in the environment by means of light they emit or reflect

Light

\-visible electromagnetic radiation

\-human vision

\-ultraviolet radiation

\-infrared radiation

Human vision is limited to wavelengths of light from…

400-700 nm

Ultraviolet radiation

< 400 nm; has too much energy and destroys macromolecules

Infrared radiation

> 700 nm; too little energy to cause photochemical reaction, but does warm the tissues