4.2 Nervous System Flashcards
Central Nervous System
Brain (86 billion nerve cells) and spinal cord (1b)
- spinal cord: long cylinder of neural tissue, extends from medulla of the brain down the middle of the back (spine)
Peripheral NS
Nerves that run thruout the body, exits from CNS
- Somatic Nervous System
- Autonomic NS
PNS: Somatic NS
contains nerves that carry sensory signals from body to CNS
nerves that carry signals from CNS to skeletal muscles
associated w voluntary movement, e.g. pressing a button: signal from BRAIN to finger via SNS
PNS: Autonomic NS
regulates internal enviro of the body
=> involuntary movement
signals from internal organs to CNS, from CNS to internal organs
e.g. digestion and heartbeat
Nerve fibers:
- Sympathetic
- Parasympathetic
Peripheral nervous system
Autonomic nervous system
Sympathetic NS (fight or flight responses) vs Parasympathetic NS (rest and digest responses)
increases energy by stimulating and mobilizing VS conserves energy
SNS - Fight or flight: increase heart rate, stimulate sweat glands
PNS - Eating a meal: stimulate digestion, slow heart rate
What protects the brain and spinal cord?
they are the best protected parts of body for survival.
Heavy bones of the skull (brain)
- meninges (membranes)
Spinal vertebrae (spinal cord)
CSF: cerebrospinal fluid (both)
- provides cushioning in case of injury
- suspends the brain to prevent false signals
- removes toxins as it constantly flows around the brain
- distributed by the ventricles in the brain
How do the CNS and PNS work together?
CNS integrates the sensory info collected by the PNS, and responds by coordinating unconscious and conscious activity
=> 2 part system
=> brain sorts the info and gives orders
What does the spinal cord initiate?
reflexes
Neurons and their functions
- sensory neurons: relay info from external environ (eg body) back to CNS
- motor neurons: from CNS to the muscles + glands of body
- interneuron: form bridges between SN and MN ⇒ do not have sensory or motor functions
