Sensory and Motor Mechanisms

Evolutionary Importance

• Some animals can sense things that other animals can't
• Different evolutionary advantages
• Don't evolve to be more exact, evolve to emphasize important information
• Comparative studies of the human brain & other small mammals' brains (from the 6 main branches of mammalian evolution)
• Areas of neocortex evolved from 20-25 in early primates to over 200 in today's humans

Overview/Major Concepts

Sensory

transduction

Conversion of stimulus energy into a change in the membrane potential of a sensory receptor (receptor potential)

Neocortex: largely involved in sensory perception & motor commands

Amplification

Strengthening of stimulus energy by cells in sensory pathways

• Sight - photoreceptors in the eye capture light and allow you to see
• Smell - odorants bind to olfactory receptors in the nose, which relay signals to the brain and gives sense of smell
• Taste - specific taste receptors that are most reactive to a certain substance, signal the brain, provides ability to taste
• Hearing - vibrations are detected and signals are sent to brain for processing

Transmission

After stimulus energy is transduced into a receptor potential, action potentials are transmitted to CNS

Integration

Processing of sensory information, begins as soon as information is received

• Touch - nerve endings in tissues send signals received from stimuli

Maintaining Homeostasis

• Many receptors send information to the hypothalamus so it is able to maintain homeostasis within the body.

• Ex. thermoreceptors send information about heat and cold from skin receptors to the hypothalamus

• Ex. Ears provide information about body position with respect to gravity so the body knows how the body is positioned in order to return to normal

• Ex. Pain receptors allow us to stay away from substances that can harm the body such as poisons and toxins

Smell

• Ex. Chemoreceptors in the blood are used to determine when insulin and glucagon should be released

Interdependence with other systems

Sensory and Motor Mechanisms

• Olfactory receptors: type of chemoreceptor, neurons lining upper portion of nasal cavity
• Odorants bind to receptor proteins on plasma membrane of cilia
• Odorant binding causes channels to be opened, Na+ and Ca2+ ions rush into cell, causes depolarization & action potential
• People detect thousands of different scents, and each olfactory cell expresses no more than a few OR genes

Skeletal: bones provide calcium, which neurons need to function

Cardiovascular: baroreceptors send blood pressure information to the brain

Muscular: allows for movement/motor function

Integumentary: receptors in skin send sensory information to brain

Immune: Pain receptors release neurotransmitters to induce inflammation and attract the immune system to the area

http://www.sinomarin.com/nose_2_4.htm

(Senses of smell and taste are separate, but interact)

http://health.howstuffworks.com/mental-health/human-nature/perception/eye2.htm

Taste

Major Senses

Sight

Red-Green

Color-Blindness

Congenital Analgesia (CIP)

• Also called Congenital Insensitivity to Pain (CIP)

• Taste buds - taste receptor cells in humans, modified epithelial cells
• 5 main taste perceptions: sweet, salty, sour, bitter, umami (savory)
• Each kind of taste receptor can be stimulated by different substances, but is most reactive to one specific substance
• For complex flavors, the brain integrates signals from multiple taste receptor cells
• Transduction pathway varies slightly between different taste receptors, but in all:

• Causes - a mutation in the gene for sodium channels in nociceptors causes them to lose the ability to transmit signals.

• Symptoms - people with the disease can sense pressure and temperature, but can't tell the difference when they are being hurt

• Most common form of inherited color blindness, affects 7%-10% of men & 0.5% of women worldwide
• Can't differentiate between shades of red and green
• Cause: loss or limited function of either red-cone or green-cone photopigments
• 1. Protanomaly: abnormal red cone photopigment
• 2. Protanopia: no working red cone cells
• 3. Deuteranomaly:abnormal green cone photopigment
• 4. Deuteranopia: no working green cone cells

• People with this disease generally have a lot of bruises or broken bones which usually aren't found.

• Multiple different layers make up the eye
• Rod cells - detect dim light, respond to changes in light intensity
• Cone cells - daytime vision, detect colors, normally 3 types
• 1. Absorbs mainly red light
• 2. Absorbs mainly blue light
• 3. Absorbs green light
• Visual processing system

• Most people with CIP also don't have a sense of smell because the mutation for the sodium channels also affects olfactory sensory neurons.

• Treatments/Cures - there is no cure for CIP, and the only treatment is to be aware of the condition and monitoring yourself for injuries.

No treatments exist for inherited color-blindness.

Receptors

depolarization causes neurotransmitters → sensory neuron → brain

Mechanoreceptors -

http://humandiagram.info/misconception-in-tongue-diagram/sense-of-taste-diagram/

Sense a physical change caused by stimuli (forms of mechanical energy)

Chemoreceptors -

includes general receptors that transmit information about total solute concetration and specific receptors that respond to single molecules

Thermoreceptors -

respond to heat or cold, respond to internal and external body temperature

Nociceptors (pain receptors) -

Diseases

and

Disorders

naked dendrites in the epidermis that respond to excess heat, pressure, or specific chemicals released by damaged or inflamed tissue

By: Rachael Brady

and Sydney Gates

Electromagnetic receptors -

detect various forms of electromagnetic energy

Hearing and Equilibrium

Tetanus

• Commonly known as "lockjaw"

• Causes - Clostridium tetani bacteria

• Affects the nervous system

• Symptoms - appear between a few days to a few weeks

• Muscle spasms, trouble swallowing, fever, elevated blood pressure, increased heart rate

• Bones in middle ear transmit vibrations creating a pressure wave in the fluid of the cochlea.
• Small hair cells in the inner ear vibrate in response to stimuli. When they vibrate a certain direction, the hair cell is depolarized and if it goes in the other direction, it is hyperpolarized.
• The stimuli are carried to the brain by the auditory nerve.
• Pitch is determined by frequency of sound waves.
• Behind the oval window are two chambers- utricle and saccule. Hair cells in the utricle and saccule respond to changes in head position with respect to gravity.

• Treatments/Cures - Tetanus vaccine

• Powerful sedatives, antibiotics, and antitoxins can also be used to treat the symptoms of Tetanus

• Statocysts are sensory organs found in many invertebrates that contain mechanoreceptors and function in sensing equillibrium

Resources

Touch

http://biology-forums.com/index.php?action=gallery;sa=view;id=8203

http://hearinghubaudiologist.co.za/blog/hearing-pretor/

• Sensation - awareness of a stimulus

• Sensory receptors in skin, skeletal muscles, or near joints transmit somatic senses

• Receptors in walls of internal organs transmit visceral signals

• The somatosensory cortex is a part of the cerebral cortex that has neurons that create a "map" of the body.

• Sensory neurons can have a capsule at the end or be free

http://web.pdx.edu/~zelickr/biology253/lecture-notes/notes/older/ch46-sensory-muscle.pdf

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2349093/

Biology: The Unity and Diversity of Life

https://www.nei.nih.gov/health/color_blindness/facts_about

http://www.colour-blindness.com/general/prevalence/

https://faculty.washington.edu/chudler/organ.html

http://ghr.nlm.nih.gov/condition/congenital-insensitivity-to-pain

http://www.mayoclinic.org/diseases-conditions/tetanus/basics/definition/con-20021956

http://biology-forums.com/index.php?action=gallery;sa=view;id=8203

http://www.interactive-biology.com/4381/an-introduction-to-the-skeletal-system-bones-and-cartilage/

https://www.studyblue.com/notes/note/n/chapter-9/deck/4368823

http://www.appsychology.com/Book/Biological/vision.htm

http://www.theasthmacenter.org/index.php/disease_information/sinusitis/types_of_sinusitis/chronic_sinusitis/symptoms_of_chronic_sinusitis

http://www.biographixmedia.com/human/ear-anatomy.html

http://humandiagram.info/misconception-in-tongue-diagram/sense-of-taste-diagram/

• Stretch receptors in muscle fibers tell the brain the position of limbs.

• Pain - perception of tissue damage

• Injured cells release local signaling molecules to inform nearby pain receptors

• Referred pain is when you feel pain in an unaffected part of the body

Skeleton

• The skeleton has 3 functions - support, protection, and movement.

Movement

• Skeletal muscles are responsible for movement.

• 3 types of skeletons:
• Hydrostatic Skeleton-consists of fluid held under pressure in a closed body compartment
• Exoskeleton - a hard encasement on the surface of an animal
• Endoskeleton - hard, supporting elements within soft tissue

• Movement in animals is based on energy consumption and muscle fibers moving together. Microfilaments are responsible for muscle movement.

• Two types of muscle fibers -
• Thin Filaments
• Thick Filaments

http://www.interactive-biology.com/4381/an-introduction-to-the-skeletal-system-bones-and-cartilage/

• Skeletal muscles are also called striated muscles.

• The arrangement of bands in sarcomeres is the key element in muscles that allows for contraction

• Vertebrate skeletons can be classified as axial or appendicular

• The Sliding Filament Model says that thick and thin filaments don't change size when muscles contract - they overlap more.

• Tails of myosin molecules attach to each other and heads attach to actin molecules and hydrolyze ATP for energy.

• Bone size is determined by weight and position of limbs.
• Muscles and tendons bear most of the weight when walking

• Energy is stored in creatine, phosphate, and glycogen.

• Action potentials travel through motor neurons and release neurotransmitters that open voltage-gated ion channels in muscles to allow calcium ions through to stimulate muscle contraction.

• Nervous system must contract ALL muscles in the motor unit.

• Muscle tension depends on the number of muscle fibers.

https://www.studyblue.com/notes/note/n/chapter-9/deck/4368823