Sensory, Motor, and Integrative Systems BIO 137 ANTOMY & PHYSIOLOGY I

General Sensations In this chapter we explore the levels and components of pathways that convey sensory nerve impulses from the body to the brain, and the general sensations (somatic and visceral) that result. We will also examine the activation of motor pathways and movements In chapter 17 we will look at the special senses of sight, hearing, taste, and smell

Special Senses Comparing the general senses and the special senses Include somatic sensations (tactile, thermal, pain, and proprioceptive) and visceral sensations Are scattered throughout the body Are relatively simple structures Special Senses Include smell, taste, vision, hearing and equilibrium Are concentrated in specific locations in the head Are anatomically distinct structures Form complex neural pathways

Sensory Receptors Receptors detect a stimulus inside or outside a cell They transmit a sensory impulse (action potentials) to the appropriate area of the cerebral cortex Each piece of incoming information is combined with other arriving and previously stored information in a process called integration What is the relay station for this information????

Sensations and Perception A sensation is the initial awareness of a stimulus (sensory impulse) Smell something sweet Perception is the way the brain interprets a sensation Smell of a banana Your perception is your reality Projection occurs when the cortex projects the sensation back towards the sensory receptor You smell the banana with your nose

Sensory Adaptation Adjustment of sensory receptors to continuous stimulation Sensory Receptor becomes less responsive to continuous stimulation A stronger stimulus is required to activate receptors i.e. entering a very ‘smelly’ location and adapting

Sensory Receptor Types Receptors can be classified by the type of stimulus they detect Chemoreceptors Photoreceptors Mechanoreceptors Thermoreceptors Pain receptors Proprioceptors

Sense Receptors Chemoreceptors Respond to changes in concentrations of chemicals O2 or CO2 levels in blood Odorants Ions Dissolved Food

Receptor Types Photoreceptors Pain receptors (nociceptors) respond to light cones and rods in retina of eye Pain receptors (nociceptors) respond to tissue damage distributed along with all receptors above, except in the brain Mechanoreceptors Sense mechanical forces (pressure, touch)

Thermoreceptors Heat receptors sensitive to temperatures above 25oC (77o F) unresponsive to temperature above 45oC (113oF) Produce burning sensation near that temperature (PAIN) Cold receptors sensitive to temperatures between 10oC (50oF) and 20oC (68oF) Produce freezing sensation near that temperature (PAIN) Thermoreceptors undergo sensory adaptation

Tactile System: Sense of Touch 1st sensory system to develop in the womb and the largest sensory system in the body Touch affects development and expansion of our brains into adulthood Studies show infants deprived of touch show developmental delays, stunted growth and abnormal cortisol levels Tactile receptor locations Skin, lining of mouth & throat, digestive system, ear canal, covering organs…..

Types of Touch Light Touch Deep Pressure Vibration Temperature Pain Meissner’s Corpuscles Feel of sand, washing your hair or face Deep Pressure Pacinian Corpuscles Bear hugs, massage Vibration Temperature Pain

Sense of Pain Detected by nociceptors (DO NOT ADAPT) Widely distributed throughout skin and internal tissues (except nervous tissue of brain) Stimulated by tissue damage, chemicals, low blood volume or O2 or extremes in temperature Function is to protect tissues from further damage

Abnormality of Perception Visceral pain results from stimulation of nociceptors in visceral organs Visceral Pain may present as considered referred pain The pain is felt in or just deep to the skin that overlies the stimulated organ, or in a surface area far from the stimulated organ. Pain is felt in an area of the body that is different than where the actual stimulus is Occurs because of shared common sensory nerve pathways to the spinal cord from the skin and internal organs

Referred Pain may occur due to sensory impulses from two regions following a common nerve pathway to spinal cord 12-11

Nociception Common patterns of referred visceral pain are shown in this graphic

Proprioception Sense associated with awareness of position of body parts in space Proprioceptors are mechanoreceptors located within joints, tendons, ligaments, connective tissue and muscles that monitor joint movement Transmit information about muscle contraction, position of joints and location of the head to the brain

Proprioception No conscious awareness of this sense While performing a task, you are not always aware of where your body parts are (or at least not thinking about them)

Somatic Sensory Pathways Somatic sensory neurons (and their axons that convey somatic sensations) are not distributed evenly in the body The peripheral areas with the highest density are represented in the brain with the largest amount of gray matter cortex. The most sensitive areas in the body are therefore the tip of the tongue, lips, and Fingertips.

Somatic Motor Pathways Motor activity begins in the primary motor areas of the precentral gyrus and other cerebral integrative centers The basal nuclei and cerebellum influence movement through their effects on upper motor neurons.

Sensory Integration or Processing All sensory input is processed together in the brain in many of the same structures SI is the neurological process of organizing sensations for use in everyday life refers to how people use this sensory info Because the senses are integrated, we assign meaning to sensory experiences and know how to respond and behave accordingly

Sensory Integration SI usually occurs without conscious thought or effort That is, you can multitask while conversing Ironing while talking, cleaning while talking You can normally tune out unimportant stimuli

Normal Sensory Processing As sensory processing skills mature, neural pathways become stronger and more myelinated Can filter out what is not important at a given time so you can focus on what is needed

Impairments in Sensory Processing The senses do not integrate efficiently Interferes with learning and development, social interaction, everyday activities Estimated to affect 10-15% of children People with SID do not have accurate information about their senses and may react inappropriately

SI Dysfunction Do not have this discriminative ability to filter out senses The brain inefficiently processes sensory information Sensory Neural pathways are not as developed

‘Seek out a sensation or avoid a sensation’

Limbic System and SI Limbic system must be involved in processing sensory info Controls emotional response to a stimulus If can not normally process sensory info, limbic system shuts down and you can not process ANY more sensory info ‘Hands over the ears’

Proprioception Abnormalities Difficulty with motor planning What do I do? Difficulty with motor control How do I do it? Poor proprioception in fingers Difficulty with fine motor skills Manipulation with the wrist and fingers Writing, buttoning Poor muscle tone

Tactile Abnormalities Avoids sticky substances Avoids sand, dirt, getting dirty Does not like tags in clothing Won’t eat certain foods because of the texture

Plasticity Capacity for the brain to change at any age Decreases with age We learn through strengthening or weakening synapses

Sensory Integration Therapy Provide different types of sensory stimulation Through plasticity, strengthen neural pathways for each of the senses Allows individuals with SID to process sensory stimuli effectively