Unit 2: Cells and Systems Topic 3: The Nervous System

Nervous System Overall, the Nervous system responds to Stimuli Which if you remember, responding to the environment is a key factor of life! What kind of stimuli are there?

Nervous System Overall, the Nervous system responds to Stimuli Which if you remember, responding to the environment is a key factor of life! What kind of stimuli are there? Temperature Light Pressure Sound Body Chemistry Dangers (burning yourself)

Neurons Neurons receive messages from small branches called Dendrites Incoming messages go from the Dendrite to the Cell Body to the Axon Axons send the messages to the following neuron’s Dendrites. This is partly done through electrical transmission!

Neurons Dendrite Axon Cell Body Neurons receive messages from small branches called Dendrites Incoming messages go from the Dendrite to the Cell Body to the Axon Axons send the messages to the following neuron’s Dendrites. This is partly done through electrical transmission! Dendrite Axon Cell Body

Neurons

Organization of the Nervous System Two main categories 1) Central Nervous System Brain and Spinal cord 2) Peripheral Nervous System Cranial nerves, spinal nerves, peripheral nerves

Central Nervous System

Central Nervous System Cerebrum Control/reaction to senses Movement Thinking Cerebellum Balance Medulla Breathing Heart Rate

Central Nervous System Reflexes can happen only using your Spinal Cord, not your brain! After you react, your brain is notified and then you scream in pain, but you hand is already safe!

Peripheral Nervous System The Peripheral Nervous System has two types of neurons 1) Sensory Neurons Carry information from the body to the central nervous system 2) Motor Neurons Carry information from the central nervous system to the body

Peripheral Nervous System Lets divide the Peripheral Nervous System again, sounds like fun right????? 1) Somatic Nervous System You can voluntarily control this For example, You choose to walk forward 2) Automatic Nervous System Your body automatically adjusts without your control For example, your pupils adjust to light, or your heart rate increases when you exercise You don’t have to tell your heart to beat!

Peripheral Nervous System

Uneven Sense of Touch Your body has certain locations of nervous responsible for vision (eyes), hearing (ears), smell (nose) and taste (tongue) What about touch? We can feel things everywhere on our bodies. Some places have more touch sensory neurons than others, our hands are much more sensitive than our backs.

Cool Fact Some nerves grow in ways that are inconvenient The RLN nerve, which goes from the larynx to the brain takes a detour and wraps around the aorta first-which does nothing! It is just how nerves first evolved Giraffes take this to the extreme, and have the nerve go all the way down their neck and back, when it could have just gone from the mouth to the brain……

Cool Fact We have a neuron (1 cell) that goes from our spine to our big toe! Called the Sciatic Nerve