Nervous System Flashcards
What are the parts of Central Nervous System? (CNS)
Brain and Spinal Cord containing relay neurones
What is the function of the CNS?
Spine: Transmits nerve signals from sensory to motor neurones by relay neurones
Brain: Transmits signals from brain to effectors
What are the parts of the Somatic Nervous System? (SNS)
Sensory neurones from sensory receptors and senses to CNS
Motor neurones from CNS to skeletal muscles
What is the function of the SNS?
Voluntary actions controlled by CNS
OR
Involuntary reflex actions (Receptors -> CNS -> Effectors)
What is the parts of the Autonomic Nervous System? (ANS)
Sensory neurones found in organs from sensory receptor to CNS
Motor neurones from CNS to smooth muscle , heart and glands
What is the function of the ANS?
Controls involuntary actions (Heart contractions)
Parts of a Neurone
- Cell Body
- Dendron and extending Dendrites
- Axon and axon terminals
- Myelin Sheaths
- Node of Ranvier
Describe the pathway of Voluntary actions
Impulses produced by brain -> Relay Neurone in spinal cord -> Motor neurone -> Effector
Describe the pathway of reflex arc
Receptors -> sensory neurones -> CNS (brain or spinal cord) -> relay Neurones (may not be involved) -> motor neurones -> effector
Differences in Voluntary and Reflex Action
- Involvement of Sensory neurone
- Involvement of brain
- Where the nerve impulse starts
- Control of action
- Time taken
Heat withdrawal reflex
Heat Stimulus -> Receptors -> Sensory Neurones -> Relay Neurones in CNS (Spinal Cord) -> Motor Neurones -> Effector (Arm Muscles)
Knee-jerk Reflex
Stimulus -> Receptor of Sensory neurone -> Sensory Neurone -> CNS (Spinal Cord) -> Motor Neurone -> Effector (Upper thigh muscle)
NO relay neurone
Sequence of neural circuits
- sensory receptor
- Transmits nerve impulses to relay neurone in CNS
- Relay neurones receive nerve impulses
- Transmit nerve impulses to motor neurones
- Motor neurones transmit nerve impulses from CNS to effectors
How do myelin sheath and Node of Ranvier work together?
- Myelin sheath provides insulation to the axon
- Node of Ranvier in between myelin sheaths allows electrical impulse to ‘jump’
Together they increase speed of nerve impulse transmission
