Class Notes for the Nervous System - Section 1

Two Systems Within a System Peripheral Nervous System: PNS All the parts of the nervous system, except the brain and spinal cord

Neuron Structure: Cell body (nucleus) Dendrites – receive impulses Axon – sends impulses Axon terminal – ends of axon (connected to other dendrites)

Information Collection: Sensory neurons – have specialized endings called receptors that collect information (pressure, temperature, etc.)

Delivering Orders: Motor neurons – send impulses from brain and spinal cord to other systems.

Nerves: Collection of axons bundled together with blood vessels & connective tissue Most have both sensory & motor neurons

Somatic and Autonomic Nervous Systems: Somatic Nervous System – voluntary actions; neurons stimulate skeletal muscles Autonomic Nervous System – involuntary actions; keeps all body’s functions in balance (digestion, heart rate, lungs, eyes)

Two Systems Within a System Central Nervous System: CNS The brain and spinal cord Brain is largest organ in the nervous system & control center

The Cerebrum Largest part of brain Controls thinking, memory, voluntary actions, & allows for senses

The Cerebellum 2 nd largest part of brain Beneath back of Cerebrum Processes sensory info and keeps you balanced (so you don’t fall )

The Medulla Connects spinal cord to brain (brain stem) Controls involuntary processes (blood pressure, temp, heart rate, breathing)

The Spinal Cord Allows brain to communicate with PNS Spinal Cord Injuries – could block all information (impulses) to & from brain

Class Notes for Responding to the Environment - Section 2

Sense of Touch Integumentary system – hair, skin, nails Sensory receptors in skin allow you to feel touch Different kinds of receptors – temp, pressure, pain, vibration

Responding to Sensory Messages Reflex – immediate & involuntary movement in response to a stimulus (impulse doesn’t go all the way to brain) Feedback mechanism – info from one step controls or affects a previous step Hot brain sweat glands cooling

Sense of Light Photoreceptor - special neuron that changes light into electrical impulses Rods – sensitive to dim light (night and b/w vision) Cones – sensitive to bright light (color & fine details) Optic nerve carries impulses to brain where they’re interpreted as images.

Sense of Hearing Sound makes vibrations against cochlea Neurons in cochlea change waves to electrical impulses These impulses travel along auditory nerve to brain that interprets sound.

Sense of Smell & Taste Taste cells (on tongue) & olfactory cells (in upper part of nasal cavity) both contain receptors that detect dissolved molecules. Exp: baking cookies give off tiny particles that go up your nose when you breathe and your brain interprets that as “baking cookies” smell! Impulses from these receptors are sent to brain that are interpreted as taste and smell. Info from both are combined in the brain to give you a sensation of “flavor”.