Anatomy Chapter 18

Adaptation

Adaptation: reduction in the sensitivity due to a constant stimulus EX: if you are stimulating something for long period of time, you become adapt to that stimulus, therefore you stop responding to that stimulus

Central adaptation

Central adaptation: CNS adapts to the stimulus (done at the level of the CNS) Your brain is consciously aware of stimulus, but quickly disappears, because your brain does not want to be stimulated by something that is not important EX: the LUCY movie where she only uses 10% of her brain Erase stimulus that are not important to us at that particular time

General Sense and Classification according to the nature of stimulus

Classification according to the nature of stimulus Nociceptors Thermoreceptors Mechanoreceptors Chemoreceptors

Perception

Conscious awareness of a sensation

General Sense and Simple Classification

Exteroceptors: provide info coming from the external environment Proprioceptors: provide info for position of the body Interoceptors: provide info for inside of the body (visceral)

Thermoreceptors

Located in specific areas of our body (EX: dermis, skeletal muscle, liver, and hypothalamus) - Type of phasic receptors (Classic EX: when its hot outside and you walk into a cold room, your body later adjust to the cold temperature in the room, therefore you don't feel as cold) Receptor receiving this difference in temp is a free nerve ending (type of receptor that is going to be taking pain info- that's why when you go to extreme temperatures you can feel a lot of pain) Two different types of receptors Cold receptors Hot receptors No structural difference between the two receptors Cold receptors are more numerous than hot receptors Both run through the same pathway of your PAIN receptors

Tactile Receptors

Located on skin 8 different types of tactile receptors Free nerve ending- pain, control temp, control touch Merkel cells- epidermis Ruffini corpuscle: Located in muscle fibers Any distortion of these will give you the sensation of tactile Note: she was very brief in this slide !

Peripheral Adaptation

Peripheral (sensory) adaptation (done at the level of the PNS) Adaptation to a stimulus because axons become tired of firing the same signal= synaptic fatigue There it stops sending the stimulus Characteristic of a phasic receptor- FAST adapting receptors Tonic receptors: little peripheral adaption therefore they are called SLOW adapting receptors

Receptive Fields

Receptors involved with characteristic sensitivity: where info is arriving in the CNS There are different types of receptors Most simplest: free nerve ending: respond to a variety of stimuli we are able to differentiate between receptors because of the endpoint of the stimuli More complex receptors (retina- only respond to light) Wide variety of receptors Receptive fields: how we are able to differentiate between sensation coming from a similar location The LARGER the receptive field the MORE DIFFICULT it is to localize a stimulus The SMALLER the receptive field the EASIER it is to localize a stimulus

Mechanoreceptors

Sensitive to stimuli that stretch, compress, twist, or distort their plasmalemma (Sensitive to any type of distortion that happens on your skin or certain type of organs, joints, and muscles (EX: stretching skin or muscle, compressing skin, twisting certain types of body parts, distorting cell membrane of a cell) Three classes of mechanoreceptors: Tactile receptors: Provide sensations of touch, pressure, and vibration Baroreceptors: Detect pressure changes in walls of blood vessels and in portions of digestive, reproductive, and urinary tracts (Work together with blood vessels to increase or decrease influx to control blood pressure, work with digestive system, reproductive, and urinary systems VERY IMPORTANT RECEPTORS) Proprioceptors : Monitor positions of joints and muscles; Most complex of the general sensory receptors (Give us our position Combines the tonic and the phasic receptors= MORE complicated )

Sensation

Sensory information arriving at the CNS

Special Sense

Smell, taste, balance, hearing, vision Sensations provided by specialized receptor cells

Chemoreceptors

Specialized neurons that can detect small changes in concentration of specific chemicals or compounds In general: Respond only to water-soluble and lipid soluble substances dissolved in surrounding fluid Found in respiratory system, carotid artery, medulla oblongata, aorta Important for these receptors Carotid Bodies and Aortic Bodies- measure pH changes, partial pressure of CO2 and O2 Due to cranial nerve IX (CAROTID BODIES): triggers reflexive adjustments in respiratory and cardiovascular activity Due to cranial nerve X (AORTIC BODIES): triggers reflexive adjustments in respiratory and cardiovascular activity Medulla oblongata- ONLY checks pH changes and partial pressure of CO2 Triggers reflexive adjustments in the depth and rate of respiration

General senses

Temperature, pain, touch, pressure, vibration, and proprioception Sensations arrive at the primary sensory cortex

Sensory Coding

The identity of the active neuron indicates: Location of the stimulus and Nature of the stimulus, , WHICH provides information about the strength, duration, variation, and movement of the stimulus

Nociceptors

Three types: Receptors sensitive to extreme temperatures Receptors sensitive to mechanical damage Receptors sensitive to chemicals All categories all have to do with PAIN The type of receptors is the free nerve ending receptor (LARGE receptive field) When they ask you at the doctor, "Where do you feel the pain?" and you can not pin point it because it has a large receptive field Type of pain sensation (We feel) Fast pain: sensation that is really fast, goes directly to the CNS; EX: usually associated with pricking pain or cuts Fast pain: the painful sensation goes away after the tissue damage has ended (so after tissue damage has been recovered) EX: prick your finger Slow pain: reaches the CNS but slowly; EX: burns and aching pains - Slow pain: takes longer for the pain to go away and the pain persist longer EX: burn your hand

Classification of Receptors

Tonic receptors: Always active (EX: photo receptors of your eye, receptors that are constantly monitoring our body position) Phasic receptors: Provide information on the intensity and rate of change of a stimulus (usually inactive, when they are stimulated then they are active for a short period of time (EX: touch and pressure receptors) Combine both: Very complicated - proprioceptors; Proprioceptors: tells you where you are in space and time