Science Test - Control and Coordination

Function of nervous system

• Monitor and control body’s organs and coordinate their activities

• Sense and respond to stimuli

Main concepts

• Form and function: organs and cells of the nervous system have structures that enable them to receive/transmit information

• Hierarchy of organization

  • Central Nervous System

  • Peripheral Nervous System

Peripheral nervous system

• All “non-Central Nervous System” nerves

• 12 cranial nerves, 31 spinal nerves

• Divided into somatic nervous system and autonomic nervous system 

Somatic nervous system & autonomic nervous system

• Somatic nervous system: communicates with voluntary muscles 

• Autonomic nervous system: communicates with internal organs/glands, divided into sympathetic nervous system and parasympathetic nervous system

Sympathetic nervous system & parasympathetic nervous system

• Sympathetic nervous system: mobilizes body systems during increased activity

• Parasympathetic nervous system: conserves energy and promotes “housekeeping” during restful periods

Central nervous system

• Includes the brain and spinal cord

  • Brain has the cerebrum, cerebellum, and brainstem

    • Brainstem has midbrain, pons, and medulla

Spine

• Backbone

• Stacked vertebrae bones with cartilage cushions in between

  • Cervical = neck

  • Thoracic = chest

  • Lumbar = lower back

  • Sacrum = tailbone

Spinal cord and nerves

• Protected by vertebrae

• Nerves exit spine through holes called neuroforamen

• 31 spinal nerves exit backbone

• Nerves = bundled neurons

Connective tissue in neurons

• Endoneurium = surrounds individual neurons

• Perineurium = surrounds bundles of neurons

• Epineurium = outermost layer that surrounds bundles of nerves

Types of neurons

• Afferent neurons

  • Receive information from stimuli and sends impulses to the CNS, “sensory neurons”

• Interneurons

  • Connect these neurons in the CNS and integrate reflexes, “relay neurons”

• Efferent neurons

  • Conduct impulses from CNS to muscles, glands, etc and carries out response to stimuli, “motor neurons”

Structure of a neuron

• Cell body

  • Contains organelles

• Dendrite

  • Receives neurotransmitters

• Axon

  • Carries impulses away from dendrites and towards the axon terminal

• Axon terminal

  • Releases neurotransmitters

• Myelin sheath

  • Fatty covering on axon which increases the speed of electrical impulses

• Schwann cells

  • Help maintain functionality of neuron, located on axon, type of glial cell (glia support neurons)

• nodes of Ranvier

  • Gaps in myelin sheath between Schwann cells

Vision

• Function

  • Convex lenses (lens and cornea) “bend” light

  • Light focuses on the macula (region in retina with more cone cells than rod cells)

  • Rhodopsin and photopsin are special proteins in cone cells and rod cells absorb different wavelengths of light

  • Allows rod and cone cells to translate light energy to an electrical message

  • Nerve cells receive impulses which get sent out of the eye through the optic nerve

• Form

  • Cornea: clear, convex, disc-shaped tissue that covers the iris and pupil, light passes through it

  • Lens: another clear, convex, disc-shaped tissue

  • Retina: nerve tissue located at the back of the eye that is sensitive to light, very sensitive macula/fovea

  • Optic nerve: bundle of nerve fibers gathered from the retina

The ear and hearing

• Function

  • Soundwaves travel through outer ear, which guides them inside

  • The middle ear translates vibration from sound waves into mechanical energy (movement of tiny bones)

  • The inner ear translates that energy into fluid waves

  • The cochlea is filled with fluid and lined with tiny hair cells

  • Hair cells bend at different frequencies and create an electrical impulse, which travels down the auditory (cochlear) nerve

• Form

  • Outer ear: pinna and ear canal

  • Middle ear: eardrum, ossicles (malleus, incus, stapes), eustachian tube

  • Inner ear: cochlea, semicircular canals, auditory nerve

The ear and balance

• Function

  • When you tilt your head or spin around, the fluid in the semicircular canals move with you

  • As the fluid moves, your hair cells bend and send a signal to your brain by your vestibular nerve

  • Your brain sends a signal via efferent neurons to respond to the movement and maintain balance

• Form

  • Also called vestibular system

  • Semicircular canals in your inner ear contain fluid and hair cells

Smell

• Function

  • Specialized neurons detect molecules in the air

  • Molecules in the air dissolve into the mucus and become detectable

  • If enough of the molecules are present, the olfactory neuron sends a signal to the brain

  • The stimulus may be recognized from a previous experience and you can identify the odor

• Form

  • Olfactory cells (kept moist by mucus)

Taste

• Function

  • Taste buds receive signal from external world and send information to the brain

  • Taste pore: molecules enter

  • Taste cell: detect molecules (type and strength)

  • Basal cell: differentiate into mature taste cells

  • Afferent nerve: if strong enough, sends signal to the brain

  • In order to taste sweet, salty, sour, bitter, and umami, the molecules must be wet

• Form

  • 10,000 taste buds on a human tongue

  • Composed of many different structures (taste pore, taste receptor cell, basal cell, afferent nerve)

  • Different parts of the tongue contain different types of taste buds

“Touch” somatosensory system

• Function

  • Thermoreceptors detect temperature and temperature change

  • Pressure receptors detect varying levels of pressure by changing shape

  • Pain receptors only respond to damaging or potentially damaging stimuli

• Form

  • Receptors for “touch” are located all over the body, inside and out

  • Thermoreceptors, pain receptors, pressure receptors

  • Different areas of the body have different concentrations of touch receptors