Ch. 5 Sensorimotor System

sensory transduction

sensory receptors convert

information from the world into electrical signals

Vision

light energy

Hearing

vibration of air

Touch

pressure, temperature

Taste & Smell

chemical

We only are aware of ____ if we have receptor

cells that can ____ them

stimuli, transduce

Sensation

receiving info from the world via sensory transduction

Perception

interpreting info from the world

Attention

plays a role in determining what is sensed versus perceived

The brain recognizes distinct senses because action

potentials travel along separate nerve tracts:

labeled lines.

Generator potentials:

stimulus produces a graded electrical potential

(like EPSP!).

If potential large enough, reaches _____ -> action potential (we have sensed it!).

threshold

5 Aspects of sensory processing:

1. Coding

patterns of A.P.s

reflect stimulus

5 Aspects of sensory processing:

2. Adaptation

loss of response when stimulation maintained

Phasic receptors

show adaptation

Tonic receptors

show little or no adaptation

5 Aspects of sensory processing:

3. Central modulation of sensory information

brain centers suppress sensory inputs

5 Aspects of sensory processing:

4. Pathways:

Each sensory

system has a labeled line.

Most pass through thalamus

on way to cortex.

5 Aspects of sensory processing:

5. Receptive fields

region of

‘space’ that a neuron in the

cortex responds to

As you sit and answer this question, you are receiving

less and less information about the feeling of the seat on

which you are sitting. This is due to the process

underlying your sensory receptors response to the

stimuli called

adaptation

The generator potential produced by a

Pacinian corpuscle (a touch receptor) in

response to mechanical stimulation is

proportional to the stimulus

intensity.

Why can’t we perceive magnetic

fields?

We do not have receptors that can transduce

magnetic fields

This is an example of a:

Phasic receptor

Pathway from touch receptor

in skin to brain:

Touch receptor axons into dorsal root of spinal cord

Touch receptor axons into

dorsal root of spinal cord ->

medulla

medulla ->

thalamus

thalamus ->

primary somatosensory

cortex

Primary somatosensory cortex in

parietal lobe.

Association areas

show mixture of inputs from different modalities.

Synesthesia

a condition in which a stimulus in one modality creates a perception in another.

If a body region is _____,

the cortical area for adjacent

body regions will expand

removed

If a body region is _____,

the cortical area for that

region will expand.

stimulated

Pain

unpleasant experience

associated with tissue damage

Congenital insensitivity to

pain:

inherited syndrome

where the person does not

experience pain.

Nociceptors

Nociceptors respond to painful stimuli.

Different nociceptors respond to pain or changes in temperature

Touch and pain have different sized axons and myelination

Spinal Pathways transmit pain information:

Free nerve endings

(nociceptors)

Free nerve endings

(nociceptors) ->

spinal neurons

spinal neurons ->

periaqueductal gray and

thalamus

periaqueductal gray and

thalamus →

somatosensory cortex and

cingulate cortex

Pain information integrated in

cingulate cortex

Neuropathic pain

(subtype: phantom limb pain) may be

due to inappropriate signaling of pain by neurons.

Which of the following are not involved

in pain perception?

lateral temporal lobe

Which of the following statements about sensory cortical

maps is true?

a. Cortical maps can change with an animal’s

experience and training.

b. if you lose your hand, the map with reorganize so that

the neurons that responded to hand touch could now

respond to face or arm touch

c. Plasticity may arise from changes in the strength of

existing synapses or the formation or loss of synapses.

Sayra practices the violin many hours each day. What

might occur to the somatosensory cortex representation

of her fingers?

The cortical finger representations will expand

Motor plan:

muscle

commands established

before action.

muscle fibers made up of ____

and ____

myosin, actin

Contraction

myosin and actin slide

past each other.

neuromuscular junction:

A.P. in motor neuron (cell

body in spinal cord/

brainstem) →

release acetylcholine at

neuromuscular junction

(synapse between motor

neuron and muscle)

release acetylcholine at

neuromuscular junction

(synapse between motor

neuron and muscle) →

triggers actin/myosin to

slide past each other =

contraction

Proprioception

information about body movements and positions.

Muscle spindles

monitor muscle stretch

Golgi tendon organs

monitor muscle contraction (strong

stimulation -> reflexive relaxation)

Commands from the brain sent through two major pathways.

Pyramidal system (or corticospinal system), Extrapyramidal system (basal ganglia and

cerebellum)

Many axons in _____ tract have cell bodies in____

pyramidal, primary motor cortex (M1)

Large regions of M1 devoted to body parts involved in ______

complex movement

lesions of M1 produce ______ on the opposite side of body

paralysis

piano players: the ____ the musician started playing, the ____ the hand area

younger, larger

Lesions along the

pyramidal tract

cause _________

paralysis in

the muscle targets

Extrapyramidal Systems regulate/fine

The basal ganglia modulates

movement:

• help control amplitude, direction, initiation of movement.

• movements guided by memories (“muscle memory” = skill memory)

Cerebellum:

Coordination, balance, fine-tune skilled

movements and classical conditioning

Poliovirus

destroys spinal motor neurons and sometimes cranial motor neurons.

Parkinson’s disease

• causes tremors at rest, loss of muscle tone, and difficulty in motor movements.

• Degeneration (death) of dopamine-containing cells of the substantia nigra

Huntington’s disease

involves basal ganglia damage, shows

excessive, involuntary movement.

Is responsible for Huntington’s disease. As

progresses, cognitive and emotional changes

A dominant allele of a single

gene (named HTT)

Primary motor cortex (M1) is

sometimes called “executive” because

it appears to control particular kinds of

_______ movements.

voluntary

The basal ganglia is important for

the

amplitude of movement

Omar has one dominant allele and one

recessive allele of the Huntington’s

Disease gene (HTT). What are the

chances that he has the disease?

100%

Allison has been infected with polio.

What may occur?

destruction of motor neurons

A complex set of commands to

muscles that is established before a

behavior starts is called a

motor plan

I hand you a very heavy item. Your muscle

spindles report stretch. You try to hold onto the

item. Now your golgi tendon organs will report

muscle _____, and if too strongly stimulated, this

will occur:

contraction; drop the item

The striped appearance of muscle

fibers is due to the regular

arrangement of thick _______

filaments and thin _______ filaments.

myosin; actin