 Autonomic Nervous System  Outline the main structural and functional differences between the somatic and autonomic nervous systems.  Identify the structural features of the autonomic nervous system.  Discuss the functions of the sympathetic and parasympathetic divisions of the autonomic nervous system.

Somatic nervous system (SNS; consciously perceived)  includes both sensory and motor neurons.  Somatic sensory neurons convey input form receptors for the special senses:  Vision, hearing, taste, smell, and equilibrium  Also receptors for somatic senses of:  Pain, temperature, touch, and proprioceptive sensations  Sensory motor neurons synapse with skeletal muscle and produce conscious, voluntary movements.  Skeletal muscles also generate breathing movements.

Autonomic Nervous System (ANS; cannot be consciously suppressed or altered)  Autonomic sensory neurons are associated with sensory receptors that monitor internal conditions.  blood CO 2 levels  degree of stretching in walls of internal organs or blood vessels  Autonomic motor neurons regulate cardiac and smooth muscles, and glands.  Comparison of somatic and autonomic motor neurons  Somatic motor neurons extend from CNS to skeletal muscle fibers that it stimulates.  Autonomic motor pathways consist of two motor neurons.  Preganglionic neuron  Has cell body in CNS  Postganglioninc neuron  Lies entirely in PNS  Autonomic also has two main branches:  sympathetic division  parasympathetic division

 ANS Neurotransmitters NeurotransmitterAcetylcholineNorepinephrine Sympathetic preganglionic neurons ALL Parasympathetic preganglionic neurons ALL Sympathetic postganglionic neurons ALL Parasympathetic postganglionic neurons A FEWMOST

Sympathetic Activities—“Fight or Flight”  “E” situations that could bring on stress:  Exercise, excitement, emergency, or embarrassment  List examples of “Fight or Flight” responses:  pupils of eyes dilate  heart rate, force of heart contraction, and blood pressure increase  airways dilate, faster movement of air into and out of lungs  reduce blood flow in vessels of nonessential organs; slowing urine formation and digestive activities during exercise  blood vessels supply organs involved in exercise or fighting off danger dilate, allowing greater blood flow through these tissues  liver cells break down glycogen to glucose, adipose cells break down triglycerides to fatty acids and glycerol, providing molecules used by body cells for ATP production  release of glucose by liver increases blood glucose level  processes not essential for meeting stressful situation are inhibited

Parasympathetic Activities—“Rest and Digest”  Supports body functions that conserve and restore body energy during times of rest and recovery  SLUDD: salivation, lacrimation, urination, digestion, and defecation

 Sensations  Define a sensation and describe the conditions necessary for a sensation to occur.  List and describe the somatic sensations.  Define proprioception and describe the structure of proprioceptive receptors.  Describe the receptors for olfaction and the olfactory pathway to the brain.  Describe the receptors for gustation and the gustatory pathway to the brain.  Describe the receptors for vision and the visual pathways to the brain.  Describe the mechanism involved in vision.  Describe the receptors for hearing and equilibrium, and their pathways to the brain.

Definition of a Sensation  Must meet four conditions:  stimulus or change in environment, activate certain sensory neurons  form of light, heat, pressure, mechanical energy, or chemical energy  sensory receptor must convert stimulus to electrical signal which produces one or more nerve impulses if it is large enough  nerve impulses must be conducted along a neural pathway from sensory receptor to brain  region of brain must receive and integrate nerve impulses into a sensation Characteristics of Sensations  Perceptions: conscious sensation  “eyes see” ; specialized sensory neurons integrated in cerebral cortex where they are interpreted  Adaptation: a decrease in strength of a sensation due to prolonged stimulus which may lead to perceptions fading or disappearing even though stimulus persists

 Review Table 12.1, page 315 for test  Free nerve endings  Encapsulated nerve endings  Mechanoreceptors  Thermoreceptors  Nociceptors  Photoreceptors  Chemoreceptors

Go to page 316 and try labeling… a. Meissner corpuscles (Corpuscles of touch) b. Pacinian corpuscles (Lamellated corpuscles) c. Ruffini corpuscles (Type II cutaneous mechanoreceptors) d. Merkel Disks (Type I cutaneous mechanoreceptors) e. Hair Root Plexuses f. Free nerve Endings

Tactile Sensations (Mechanoreceptors) Touch, pressure, vibration -- Detected by encapsulated nerve endings Itch, and tickle -- Detected by free nerve endings

 Touch  rapidly adapting touch receptors:  Corpuscles of touch (Meissner corpulses)_  Hair root plexuses_  slowly adapting touch receptors:  Type I cutaneous mechanoreceptors (Merkel disks)  Type II cutaneous mechanoreceptors (Ruffini corpulses)  Pressure and Vibration  pressure is a sustained sensation felt over a larger area than touch  Pressure receptors:: Type I mechanoreceptors and lamellated (pacinian) corpulses  lower frequency vibrations: corpulses of touch  higher frequency vibrations: lamellated corpulses  Itch and tickle  Itch sensations stimulated by stimulation of free nerve endings by certain chemicals like bradykinin, often a result of local inflammatory response Can you tickle yourself? Why or why not? Impulses are conducted to and from cerebellum when you are moving your fingers and touching yourself does not occur when someone else tickles you

 Thermoreceptors: free nerve endings  Thermal sensations: coldness and warmth  Temperatures between 10  and 40  C (  F)  activate cold receptors  located in the epidermis  Temperatures between 32  and 48  C (  F)  activate warm receptors  located in the dermis  Below 10  C and above 48  C stimulate  nociceptors  produce painful sensations

 Nociceptors: free nerve endings  Found in almost every tissue of body except brain  Five stimuli that can cause pain  excessive stimulus of sensory receptors  bright light in your eyes  excessive stretching of structure  prolonged muscle contractions  hold weight for a long time  inadequate blood flow to organ  certain chemical substances  Referred pain: pain felt in skin above or located near but not in organ  Fast pain: within 0.1 seconds of stimulus; acute, sharp, or prickling pain; localized not in deep tissue  Slow pain: begins a second or more after stimulus is applied; chronic burning, aching, throbbing; skin deep tissue and internal organs

 Inform you consciously and unconsciously of  degree to which your muscles are contracted  amount of tension present in your tendons  positions of your joints  orientation of your head  Receptors for these sensations called:  Proprioreceptors and are located in:  skeletal muscles, tendons, in and around synovial joints, and in inner ear  They adapt slowly and only slightly  Kinesthesia: perception of body movements, allows you to walk, type, or dress without using your eyes

OLFACTION: SENSE OF SMELL (Chemoreceptors)  CHARACTERISTICS OF RECEPTORS:  first-order neuron of olfactory pathway  tips are protected by olfactory hairs  stimulated by odorants; inhaled chemicals  cells live about a month and then replaced

GUSTATION: SENSE OF TASTE (Chemoreceptors)  CHARACTERISTICS OF RECEPTORS:  chemicals known as tastants stimulate them  electrical signal stimulate release of neurotransmitter molecules that bind to gustatory receptors on dendrites of taste buds’ first-order neurons  respond to any one of five primary tastes: sweet, sour, bitter, salty, or umami (savory, glutamate detection)  1. bitter  2. salty  3. sour  4. sweet

VISION (Photoreceptors)  Retina is the beginning of visual pathway  Three layers:  photoreceptor layer, bipolar cell layer, and ganglion cell layer  Two types of cells in photoreceptor layer:  rods (allow us to see shades of gray in dim light, like moonlight)  cones (stimulated by brighter light- highly acute, color vision)  Stimulation of photoreceptors  photopigment absorbs light ; undergo change in structure to adjust to amount of light available  rods photopigment is rhodopsin

HEARING AND EQUILIBRIUM (Mechanoreceptors)  Ear three principle regions: the outer ear, the middle ear, and the inner ear.  Physiology of Hearing (1) auricle directs sound waves into external auditory canal (2) sound waves strike eardrum; produce vibrations, eardrum vibrates in response (3) central area of eardrum connects to malleus that also starts to vibrate, vibration moves from malleus to incus to stapes (4) stapes moves back and forth, pushes the oval window in and out (5) movement of oval window sets up fluid pressure waves in cochlea (6) pressure waves move eventually to membrane covering the round window causing it to bulge into the middle ear (7) pressure waves deform walls internal structures pushing membranes back and forth, creating pressure waves inside cochlear duct (8) pressure causes basilar membrane to vibrate, moving hair cells of the spiral organ release neurotransmitter molecules; sensory neurons generate nerve impulses along nerve and sound is received and interpreted

Physiology of Equilibrium  Static equilibrium  maintenance of the position of the body relative to the force of gravity; maintains posture and balance by providing sensory information on the position of the head  Dynamic equilibrium  maintenance of body position in response to sudden movements such as rotation, acceleration, and deceleration; reestablish balance to disturbed equilibrium by regulating sensitivity of hair cells in the ear