bio 10

-exteroceptive

-proprioceptive

-interoceptive

-perception of stimuli applied to the skin

-perception of joints, muscles, and balance. Important for knowing where your body is in space

internal signals such as body temp and blood pressure

• - free nerve endings
• *temp, pain

-pacinian

-ruffini

-merkel

nerve endings on skin

*pick up information on temp, pain, etc.

-respond to displacement of the skin (pressure)

-rapidly adapting

-best suited for sensing suddent change

-adapt slowly

-best suited to signal gradual changes in skin stretch

-adapt slowly

-best suited to singla gradual changes in skin indentation

spinal cord where they enter via dorsal root ganglion.

area of skin that is served by the dorsal root ganglion

-orderly entry of dermatomes into the spinal cord

-topography is maintained all the way to the cortx just like in the viual and auditory systems

1. info enters via dorsal root ganglion

2. information projects to and synapses on to cells of dorsal column nuclei

• 3. CONTRALATERAL projection to ventral posterior nucleus of the thalamus
• 4. then arrives at primary somatosneory cortex

-vision

-audition

-gustation

-somatosensation

lateral geniculate nucleus

-located in occipital

medial geniculate nucleus

-located in temporal

ventral posterior medial nucleus

-located in frontal

ventral posterior nucleus

-located in parietal

-in the parietal lobe

-posterior to the central sulcus

somatosensory map

-representations vary per body part, some are more sensitive than others

*receptive fields are much larger on our trunks than hands.

• brain structures can change to better cope with the environment
• *constant stimulation can change the pattern of nuerons

limb is lost, individual still feel sensations in that limb for days, months, and even years to come

-representation of the limb in somatosensory cortex is still present

Therefore, because the limb is no longer in use, adjacent areas of somasensory cortex might take over (plasticity)

• -damahe to large portions or parietal cortex include primary and secondary leads to asomatognosia
• *failure to recognize a body part as belonging to oenself

• -can also result in contralateral neglect
• *people fail to address their other side of body affected

• sensory systems interact with motor systems to guide appropriate motor behavior
• *when we make a movement, all the following in used report back to evaluate how effective the movement was

• -we must know where our limbs are realtive to our body
• *starting point

-we must know location of the object we wish to target for grasping

-receives input from visual, auditory, and somatosensory systems

-sends info to secondary motor cortex and other areas of association cortex involved in movement

-receives information from sensorimotor association cortex

-sends information to primary motor cortex

-involved in planning of motor sequences

*stimulation of secondary motor cortex evokes complex movements that involve both sides of the body

-neurons in this morter cortex begin responding before movement has been initiated

• - some regions have bimodal responses.
• *they respond to visual stimuli in addition to being involved in movements

-individual areas of primary motor cortex control the movement of specific muscle groups

• -it also receives 'feedback' from somatosensory system via somatosensory cortex as well as receptors in muscles and joints so that movements can be completed or modified
• *throwing darts at bullseyes

-located in the frontal lobe

*just anterior to the central sulcus

cross the middle line

does not cross the midline

individual muscle fibers

-slow twitch and fast twitch

contract faster but exhaust

contract more slowly but can contract more often

a fixed number of muscle fibers

motor unit

all the fibers it contacts will contract

which causes the muscle to contract

spinal motor nuerons

they either directly or undirectly innervate neurons of the ventral horns of spinal cord