~ Chapter 2, Pt. 1 ~
Nervous System & Neurons
Communication Systems
● Two systems that coordinate behavior
○ Nervous system (instantaneous)
■ Sends signals through electrochemical impulses in the brain and spinal
cord
■ Central nervous system → consists of the brain and spinal cord
■ Peripheral nervous system → all other nerves in the body
● Somatic nervous system → controls voluntary muscle
movements, senses, pressure
● Autonomic nervous system → controls smooth muscle function
(i.e. organs)
○ Sympathetic → prepares the body for action; “fight, flight,
or freeze”
○ Parasympathetic → returns body to homeostasis
○ Endocrine system (slower, longer lasting)
■ Secretes hormones into the bloodstream
○ Both react to stimuli (internal and external)
The Brain
● Weighs about 3 pounds and is about 70% fluid
● Predominantly soft tissue, susceptible to being damaged
○ Brain often swells in response to damage and can cause tissue death
■ Parts of the skull can be removed to relieve swelling if necessary
● Traumatic brain injury → TBI
● Neuroplasticity → the ability of the brain to change and adapt
○ Includes taking over for damaged sections
● Clinical death → when a person has flatlined and have died, but could still be potentially
brought back; different from biological death
● Biological death → irreversible damage to the brain; brain dead
○ Over 50% of oxygen intake goes to the brain
○ 3-4 minutes without oxygen before damage is done
○ One sign for not enough oxygen is lower body temperature, as that means less
oxygen is needed
Structure of the Brain
● Hindbrain (subcortex) → considered the most primitive part of the brain; controls
survival instincts
Nervous System & Neurons
Communication Systems
● Two systems that coordinate behavior
○ Nervous system (instantaneous)
■ Sends signals through electrochemical impulses in the brain and spinal
cord
■ Central nervous system → consists of the brain and spinal cord
■ Peripheral nervous system → all other nerves in the body
● Somatic nervous system → controls voluntary muscle
movements, senses, pressure
● Autonomic nervous system → controls smooth muscle function
(i.e. organs)
○ Sympathetic → prepares the body for action; “fight, flight,
or freeze”
○ Parasympathetic → returns body to homeostasis
○ Endocrine system (slower, longer lasting)
■ Secretes hormones into the bloodstream
○ Both react to stimuli (internal and external)
The Brain
● Weighs about 3 pounds and is about 70% fluid
● Predominantly soft tissue, susceptible to being damaged
○ Brain often swells in response to damage and can cause tissue death
■ Parts of the skull can be removed to relieve swelling if necessary
● Traumatic brain injury → TBI
● Neuroplasticity → the ability of the brain to change and adapt
○ Includes taking over for damaged sections
● Clinical death → when a person has flatlined and have died, but could still be potentially
brought back; different from biological death
● Biological death → irreversible damage to the brain; brain dead
○ Over 50% of oxygen intake goes to the brain
○ 3-4 minutes without oxygen before damage is done
○ One sign for not enough oxygen is lower body temperature, as that means less
oxygen is needed
Structure of the Brain
● Hindbrain (subcortex) → considered the most primitive part of the brain; controls
survival instincts
