PHR 3100 EX2

Sensory input is the \______ tract

afferent

motor output is the \_______ tract

efferent

Integration neurons are found in what part of the nervous system?

CNS

Represents the afferent arm of the nervous system and provides the brain with information about the internal and external environment

sensory system

Three parts of the sensory system?

(1) sensory receptors (receive stimuli from the external or internal environment),
(2) the neural pathways (conduct information from the receptors to the brain or spinal cord),
(3) parts of the brain (process information).

What are the five senses?

vision, hearing, smell, taste, equilibrium

perception

the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events
conscious interpretation of the external world

transduction

conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brains can interpret.

Starting with the physical stimulus to the perception of something, list what occurs?

transduction- convert the physical stimulus to something the brain can understand
conduction- sending the signal from the receptor to afferent neurons to eventually the brain
processing, once the signal is in the brain, the brain processes it with 2-4 order neurons

photoreceptors

eye detect light (vision).

mechanoreceptors

skin, joints, muscle, inner ear, etc. transmit mechanical deformation (touch, pressure, hearing, balance).

thermoreceptors

detect temperature

chemoreceptors

detect chemicals (smell, taste)

nociceptors

detect pain

What are the two basic sensory receptor arrangements?

1. specialized nerve ending on primary afferent neurons
2. specialized receptor cells associated with primary afferent neurons (the receptor cell sends signal to the afferent cell EX: photoreceptor)

receptor potential

A slow, graded (means it is proportional to stimulus intensity) electrical potential produced by a receptor cell in response to a physical stimulus; if it reaches the threshold it can become an AP

trigger zone

where action potential is generated

AP threshold

charge that must be reached to generate an AP

Since all AP are the same strength how do you distinguish between greater intensity stimuli?

AP frequency
primary afferent neuron firing frequency reflects the magnitude of the receptor potential which reflects the magnitude of stimulus

What is coding?

conversion of stimuli into the action potential int he CNS and the AP frequencies

What are the four key questions for primary sensory coding?

What is it? (quality/modality)
How strong is it? (intensity)
How long is it? (timing)
Where is it? (localization)

modality

The specific form of energy of a stimulus (either temp, sound, pressure, light, pain, taste, etc.)

receptor specificity

Receptors are designed to respond best to specific modalities EX: temp, pressure, light, etc

adequate stimulus

the type of stimulus for which a given sensory organ is particularly adapted (the modality to which the receptor responds to best)

What determines stimulus intensity?

Coded by the level of threshold (minimum stimulus intensity that is needed to activate the receptor

The typical response to a CONSTANT stimulus is \___________ in time

decreases

sensory adaptation

•when sensory receptors change their sensitivity to the stimulus.

Adaptation involves a decrease in the size of the receptor potential with a \________ stimulus

constant

How does the brain know where a stimuli, such as touch, temp, or pain came from (localized)

Labelled line code connects the peripheral receptor to the cortex via series of neurons
think of how an old telephone, where the operator would link you up to the correct person on the other end

1st order neuron

detects a stimulus and transmits a signal to the spinal cord or brainstem

2nd order neuron

from spinal cord to thalamus

3rd order neuron

thalamus to primary somatosensory cortex of cerebrum

lateral inhibition

The pattern of interaction among neurons in which activity in one neuron inhibits adjacent neurons' responses.
Look at slide 25 of slides "Singh Sensory" has good visual, basically the most stimulated neuron will tell nearby ones to not activate as much

What is central control of the afferent information mean?

All sensory signals are subject to extensive modification at the various synapses along the sensory pathways before they reach higher levels of the central nervous system
EX: an inhibitor neuron sending a signal to an afferent to not send a signal

What percent of adults lose at least 1 of five senses?

94%

Sensory neuron diseases

peripheral-nervous-system diseases caused by degeneration of short and long peripheral axons and afferent sensory projections. Caused by systemic immune problems, vitamin intoxication/deficiency, neurotoxic drugs, cancer, genetic mutations

synesthesia

crossovers in the senses activity in one sensory modality, such as vision or hearing

prosopagnosia

(face blindness) - inability to recognize faces in 1.5 % of population. Caused by brain damage

motor neurons

nerve cells in the spinal cord that send their axons to innervate muscles

What neurotransmitter is used to innervate muscles?

acetylcholine

neuromuscular junction

point of contact between a motor neuron and a skeletal muscle cell

The right side of the brain controls what side of the body?

left side

Where do neurons cross to the other side in the body?

1. in the medulla
2. crosses in the spinal cord as well

What composes a motor unit?

•A motor unit is made up of a motor neuron and the skeletal muscle fibers innervated by that motor neuron's axonal terminals.

What determines contraction strength of a muscle?

•Contraction strength is determined by AP frequency and recruitment of motor units.

innervation ratio

number of fibers innervated by an axon

can you draw a strict definition between voluntary and involuntary movements?

no, almost all motor behaviors involve both components

•Actions become more \____________ as the actions are repeated

involuntary

What are the three classes of motor movement?

1. reflexes
2. rhythmic motor patterns
3. voluntary movements

reflexes characteristics (how complex, voluntary?, example, where does motor movement come from?)

•Simplest
•Largely involuntary
•Examples: sneezing, knee-jerk, flexor withdrawal, etc.
Spinal cord

rhythmic motor patterns characteristics (how complex, voluntary?, example, where does motor movement come from?)

•Starting & stopping are voluntary
•sequence of stereotyped, repetitive movements
• Examples: walking, running, etc.
•Thalamus, basal ganglia, cerebellum)

voluntary movements motor patterns characteristics (how complex, voluntary?, example, where does motor movement come from?)

•Goal-directed and purposeful
•Largely learned and improve with practice
•Examples: playing piano, writing, etc.
•Cerebral cortex
motor areas

What is the motor control hierarchy?

You start at the high level (pre-command level) where planning occurs, then in the middle level you have the projection level, which creates the instructions, the final level is the segmental level which is the central pattern generation
the cortical association cortex in the high pre-command level creates the idea for voluntary movement, which is communicated to both the cerebellum and the basal ganglia
In the middle projection level rhythmic motor patterns are created, which are communicated via the motor cortex/brain stem
in the low segmental level, which is the spinal cord, relfexes occur
For a good diagram go to slide 10 of the powerpoint "singh motor control"

interneurons

Interneurons can be inhibitory or excitatory and can function as switches to turn motor neurons "on" or "off" (constitute 90% of spinal cord neurons).

reflex

rapid, predictable, and involuntary responses to stimuli.

reflex arc

shortest route from a sensory neuron to an effector.

monosynaptic reflex

Reflex pathway with only one synapse between the sensory and motor neurons (ex: knee-jerk).

polysynaptic reflexes

-More complex neural pathway
-More than one synapse involving interneurons within the reflex arc
-The withdrawal reflex is an example

The reflex arc is useful to a doctor because?

it can indicate damage in the nervous system

Reciprocal Innervation-

The activation of neurons to one muscle with the simultaneous inhibition of neurons to its antagonistic muscle

Proprioreception

the collection of information about body movements and position; awareness of the position of movements of body parts

Two major types of proprioreceptive receptors?

Muscle-spindle stretch receptors are mechanoreceptors monitoring muscle stretch.- found in the muscle the nerves wrap around the tendon and are stretched when the muscle is stretched
Golgi tendon organs are in the fibrous tendons that connect muscles to bone, monitoring muscle tension.-

How do golgi tendon organs work?

when the collagen fibers (tendon) are pulled on (increased tension) they fibers straighten out and the neuron that is tangled in the fiber is distorted and thus activates the receptor

Stretch reflex vs golgi tendon reflex

The stretch reflex, causes extensor contraction and flexor relaxation
the golgi tendon reflex is the opposite, it causes extensor relaxation and flexor contraction- basically override the stretch reflex, they work together to create the knee tap reflex

The nerve fibers of the corticospinal pathway starts in the \________ cortex and terminate in the \________, cross the midline.

sensorimotor; spinal cord

Do brainstem pathways cross sides?

no they stay on the same side

•Relative sizes of body structures are \____________ to the number of neurons dedicated to their motor control.

proportional

motor program

a particular class of actions is stored in memory and that a unique pattern of activity will result whenever the program is executed.

Based on proprioceptive info, the \__________ neuron programs are modified

motor

•If a complex movement is repeated, learning takes place and the movement becomes \__________ (improved program).

skilled

voluntary movements are decided by?

prefrontal cortex

voluntary movements are selected by

premotor cortex

voluntary movements are executed by the?

motor area of the cerebral cortex

•The selection of desired movements and supression of unwanted movements involves \_______ \_________ circuits that inhibit thalamic projections to the motor cortex

basal nuclei

•The \_______________ corrects errors in ongoing movements via exciting thalamic projections to the motor cortex.

cerebellum

Parkinson disease is caused by?

a deficiency of the neurotransmitter " dopamine " in the substantia nigra; thus the basal ganglia cannot send signals ot the motor cortex; less instructions for movement, means more shaky and less voluntary movement

Parkinson causes what in each of these areas?
Substantia nigra
Basal ganglia
thalamus

SN-input is diminished
BG- less inhibition of the inhibitory output
more inhibition of thalamus, means less thalamic excitation of motor cortex

\___% of what we learn is though our eyes

80%

What is require to perceive a visual signal?

1.the eyes capable of detecting, focusing and responding to light (eyes are the second most complex organ after the brain; can process about 60 image frames per sec)
2.the appropriate neural pathways
3.Brain regions to interpret the signal (about half of the brain is involved in vision).

visual perception

the ability to detect light and interpret it

Visual transduction of light is done by?

rod cells and cone cell of the retina, they convert light into electrical signals

wavelength

distance between successive peaks of EM radiation (from one peak to the next)

visible spectrum

400-750nm

What wavelength of light can snakes see?

infrared

reflection

•Light waves strike and bounce off surfaces that we see. (Although we receive some light directly (sun & light bulb) most light is reflected off the objects with non-perceived wavelengths absorbed.)

Refraction

Light waves bend as they pass through transparent materials of different densities.

iris

muscle that controls size of pupil and amount of light that enters eye regulates the diameter of the pupil

retina

layer of tissue containing the photoreceptors

optic nerve

axons of ganglion neurons in the retina that carry visual information to brain

What are the two muscle types of the iris?

the radially arranged and the circular muscle fibers
radial muscles all area directed so they go in toward the center of the eye, when contracted, they pull the inner part of the iris away from the center, and widen the pupil to let more light in
The inner circular fibers are arranged in a circle, when contracted they constrict the pupil an make it smaller, to let less light in

Radial iris muscles are stimulated by?

parasympathetic nerves

Circular muscle fibers of the iris are stimulated by?

The sympathetic nerves

If it is dark, which muscles of the iris would contract, which part of the nervous system does this?

radial muscles by the parasympathetic nerves

cornea and lens have \______ surfaces to focus light rays onto the retina

convex

What basis is used to focus light on the retina?

refraction

Visual info that reaches the retina is \______ right to left and is upside down

reversed

When you view a far away object the lens \______ for a weak refraction

flattens

When view a object is close the lens \_______ for a strong refraction

rounds

accommodation

•refers to normal ability of lens to adjust its curvature to view near or far objects

Why do objects close to you require more refraction to view clearly?

•Light rays that enter the eye from distant objects are nearly parallel and require little bending or refraction to focus on the retina.
•Light rays from close objects are diverging as they enter the eye and require more refraction.