Exam 2 Quiz 2 Flashcards
Define the peripheral nervous system and list its components
-all neural structures outside of the brain and spinal cord
-sensory receptors
-peripheral nerves and associated ganglai
-motor endings (i.e. axon terminal, motor end pate)
-ganglia are a collection of cell bodies in the PNS
How are receptors classified
-stimulus type
-location
-structural complexity
classifications of receptors by stimulus type
Mechanoreceptors- light touch, pressure, vibration, stretch and itch (these adapt readily)
Thermoreceptors- changes in temperature
Photoreceptors- light energy (e.g. retina)
Chemoreceptors- chemicals (e.g. smell, taste, changes in blood chemistry)
Nociceptors- pain causing stimuli (e.g. extreme heat or cold, excessive pressure, inflammatory chemicals)
-receptors differ in there locations intensity of stimulus required to generate an impulse of adaptability
How do you classify receptors by location
-the two classifications are somatic and special
somatic: multiple locations in the body
-pressure temperature, pain touch, body position and movement
-primary somatosensory cortex(post central gyrus)
Special: only in certain areas of the body
-taste, smell hearing, balance, vision
-perception processing in specific cortical regions
what is the difference between sensation and perception
-sensation: awareness of changes in internal and external environment
Perception: conscious interpretation of those stimulus (applying meaning)
list the three basic levels of neural integration in sensory systems
- receptor level: sensory receptors (transduction: this is converting to electrical stimulus –> graded potentials)
*graded potentials are the nervous system translation of stimulus
- circuit level: processing in ascending pathways (transmission–> APs)
*transmission is the propagation of action potential across axon
- perceptual level: processing in cortical sensory area
How does the central nervous system interpret information based on origin and frequency
-the action potentials are transmitted to specific brain regions
-visual stimuli travel via sensory neurons directly to brain areas associated with vision
-all information traveling through these neurons are interpreted as light
-stronger stimuli activate more receptors and trigger greater frequency of impulses in sensory neurons
-activation of a sensory pathway at any point gives rise to the same sensation that would be produced by stimulation of receptors in the body part itself
-acuity is influences b the receptive field size
-each sensory neuron responds to stimulus info only within a circumscribed region of the body surrounding it (receptive field)
-the size of the field varies with density of receptors in region; the more closely receptors are spaced, the smaller the area of the body each monitors
-the smaller the receptive field, the greater its acuity or discriminative ability
Define sensory adaptation, what is the advantage of this and which receptors adapt slowly and which ones quickly
-sensory neuron stops sending impulses even tough stimulus is still present
advantage: keep track of changes in stimuli while ignoring unimportant stimuli
-certain receptors (olfaction, light touch) adapt quickly while others (pain, joint and muscle) adapt slowly or not at all
-the ones that don’t adapt are pain receptors and thermoreceptors
Name the components of a reflex arc
-reflexes occur over neural pathways called reflex arcs that have five essential components- receptor, sensory neuron, CNS integration center, motor neuron and effector
Describe what each component of the reflex arc does
- receptors are the site of stimulus action
- Sensory neurons transmit afferent impulses to the CNS
- integration Center: if it is a simple reflex arc, the n the integration center will be a single synapse in the middle of a sensory neuron and a motor neuron. in more complex reflex arcs, multiple synapses with chains of interneurons are involved
- motor neurons: conducts efferent impulses form the integration enter to an effector organ
- Effector: muscle fiber or gland cell that responds to the efferent impulses (by contracting or secreting)
What are inborn (intrinsic) reflexes
a rapid, involuntary, predictable motor response to a stimulus
learned (acquired) reflex
A reflex that results from practice or repetition (like driving)
What does the knee jerk reflex test
the somatic reflexes is important clinically to assess condition of the NS
Compare and contrast stretch & tendon reflexes (hint proprioception)
-they both help the nervous system smoothly coordinate the activity of your skeletal muscles
-in order to be able to coordinate the activity of the skeletal muscles the length of the muscle must be known and the tension of the muscle and the associated tendons
-proprioception (where the body is in space) is essential for smooth, coordinated movements
what is in charge of detecting the length of the muscles
the muscle spindles
what is in charge of the tension in the muscle and tendons
the golgi tendon organs
what is the role of mechanoreceptors and reflexes
the mechanoreceptors in skeletal muscle, tendon and joints respond to changes in muscle length, tendon tension and joint position (proprioceptors)
Describe the stretch reflex
-maintain muscle tone in large postural muscles
-cause muscle contraction in response to increased muscle length (stretch)
-all stretch reflexes are monosynaptic and ipsilateral
What nervous systems are involved in conscious control of skeletal muscles
-the afferent and somatic efferent nervous systems
-they are also involved in the involuntary mechanisms to control muscles
-most somatic reflexes help us maintain balance/ posture and avoid injury
What are the 3 types of muscle tissue?
skeletal, cardiac, smooth
describe skeletal muscle tissue (what is it attached to, its shape, what it looks like etc)
-it is attached to bones and skin
-striated (myofibrils)
-voluntary (conscious control)
-powerful
-single, very long cylindrical, multinucleate cells with obvious striations
cardiac muscle tissue
-the walls of the heart
-shows uninucleate or bi nucleate striations
-involuntary
smooth muscle tissue
-Involuntary
-single unit muscle in the walls of hollow visceral organs (other than the heart) multiunit muscle in intrinsic eye muscle, air ways, large arteries
-single fusiform, uninucleate and no striations
List four important functions of muscle tissue.
-produce movement of bones or fluid (blood)
-maintain posture and body position
-stabilize joints
-generate heat(skeletal muscle)
what are the special characteristics of muscle tissue
-excitability: (responsiveness or irritability): receive and respond to stimuli
-contractility: shorten when stimulated
-extensibility: stretch
-elasticity: recoil to resting length
-they can transform chemical energy (ATP into directed mechanical energy (this makes them capable of exerting force)
How many arteries, nerves and veins is each skeletal muscle served by
-one artery
-one nerve (with multiple neurons)
-one or more veins
why does skeletal muscle have such a rich blood supply
-they need a rich blood supply because they need oxygen and nutrients o produce ATP for contraction
how are skeletal muscle fibers organized
-striated by a highly organized internal arrangement
what is a skeletal muscle cell
muscle fiber
how is a skeletal muscle organized and how long are the fibers
-many parallel muscle fibers bundles by connective tissues
-fibers usually extend entire length of muscle
embryonic development
-formed by fusion of many smaller cells called myoblasts
myo=muscle
blasts= primitive cell that forms more specialized cell)
Why does it make sense that another feature of skeletal muscle is the abundance of mitochondria
-ATP is needed for muscle contraction (chemical energy–> mechanical energy)
what are Myofibrils
-Densely packed, rodlike elements
- 80% of cell volume
-Exhibit striations
-contains myofilaments creating dark A band and light I band
Describe the functional role of myofibrils
to produce muscle contraction and relaxation
Describe the microscopic structure and the functional role of the sarcoplasmic reticulum, and T tubules of skeletal muscle fibers
-both regulate muscle contraction
-The Sarcoplasmic reticulum regulates intracellular levels of ionic calcium. It stores calcium and releases it on demand when the muscle fiber is stimulated to contract
-Most Sarcoplasmic reticulum tubules run longitudinally along the myofibril
-T tubules increase the muscles fiber surface area
-T tubules also encircle each sarcomere
-Think of the T tubules as a rapid communication or messaging system that ensures that every myofibril in the muscle fiber contracts at virtually the same time
Describe the sliding filament model of muscle contraction
-when relaxed: slight overlapping of actin and myosin
-When the nervous system stimulates muscle fibers, the myosin heads on the thick filaments latch onto myosin-binding sites on actin in the thin filaments, propelling actin toward M line
-sarcomeres, muscle cells and whole muscle shortens
-the H zone disappears and the I band shortens
Define motor unit
A motor unit consists of one motor neuron and all the muscle fibers it innervates, or supplies
Describe the difference between eccentric and concentric contractions
Concentric Contractions: muscle shortens and does work, such as picking up a book or kicking a ball (think of coming together)
Eccentric Contractions: muscle generates force as it lengthens, are equally important for coordination and purposeful movements
-Eccentric contractions occur in your anterior thigh muscles
Name the cranial nerves that are involved with the special senses
CN I: Olfactory Nerve (smell)
CN II: Optic Nerve (vision)
CN VII: Facial Nerve (taste)
CNVIII: Vestibulocochlear Nerve (hearing and balance)
CN IX: Glossopharyngeal (taste)
CN X: Vagus ( taste)
Describe the location and structure of taste receptors
-taste depends on chemoreceptors found on the tongue
-taste bud: cluster of 25 taste cells and 25 supporting cells
about 10,000 taste buds
-found mostly on papillae of the tongue
-taste hairs contain chemoreceptors specific for certain chemicals of tastants
-most taste receptors are located along outer of tongue with few receptors in the center of the tongue
What do taste buds convert chemical signals from food and drink to
-taste buds convert chemical signals from food or drink dissolved in saliva into Action Potentials
what are the five qualities of taste that taste receptors and sensory neurons respond to
-sweet
-sour
-salty
-bitter
umami (savory)
Describe the gustatory pathway
-tastant bind to chemoreceptors causing to depolarization and NT release that stimulates…
-Cranial Nerves VII, IX and X carry impulses from taste buds to medulla
-then it goes to the thalamus
-gustatory cortex in the insula
-hypothalamus and limbic system appreciation and hippocampus (memories)
relationship between taste and other senses and receptors
-taste is combined with signals from multiple taste receptors allow us to differentiate between hundreds of flavors
-taste is 80% smell
-chewing food releases chemicals from the food that contact olfactory receptors
-thermoreceptors, mechanoreceptors, nociceptors in mouth also influences taste
-temp and texture enhance or detract from taste
Describe the location and structure of smell receptors (also how many olfactory chemoreceptors are for different odorants)
-there are olfactory chemoreceptors for more than 1,000 different odorants
-olfactory hairs project into the olfactory epithelium covering inner surface of nostrils
Pathway for smell
odorants dissolve in mucus and bind to chemoreceptors on olfactory hairs
-olfactory receptor cells then generate an impulse
-olfactory receptor cells synapse with olfactory neurons in olfactory bulb where the information is partially integrated before being passed to olfactory areas in frontal and temporal lobes
- around 10,000 different smells can be sensed
What makes smell different from the other senses?
-messages from the olfactory nerves go directly to the limbic system, without entering the thalamus first
Compare and contrast the roles of rods and cones in vision
rods: dim light, shades of grey, peripheral vision receptors
-rods are more sensitive to light than cones but do not provide clear outlines of objects
Cones: bright light, color images and sharp outlines
-remember colorful cones
Describe the relationship of cones and wavelength
-blue, red and green cones are named for the wavelength of light that they absorb best
-all other colors come from activation of more than one type of cone at the same time
color blindness
-is more common in men
-it is due to a lack of one or more cone cell
Photoreceptors (where are the located and what do they do)
-located in the eyes (the retina) and they receive visual information
-photoreception: eye detects visual stimuli by converting light energy to nerve impulses and transmitting them to the brain (this is the transduction for eyes)
Pathway of light through the eye
Light enters eye -> cornea -> aqueous humor -> pupil -> lens -> vitreous humor -> neural layer of retina
What is the iris
-Controls the diameter of the pupil and how much light enters
-dilates and constricts the pupil
Constrictor pupillae: constricts the pupil
Dilator Pupillae: dilatates the pupil
what are Golgi tendon reflexes
-polysynaptic reflexes
-help prevent damage due to excessive stretch/ force by relaxing the muscles
-important for smooth on sent and termination of muscle contraction (coordination of movements)
