Division of the nervous system

The nervous system

• split into 2 parts

• peripheral nervous system:

• extends beyond the CNS

• transmits messages to and from the nervous system

• responsible for relaying messages (nerve impulses) from the brain and spinal cord to the rest of the body

• the central nervous system

• brain and spinal cord

• The main job is to ensure life is maintained

• Some parts of the brain are involved with problem-solving and planning

• The spinal cord transmits messages to and from the brain to the peripheral nervous system 

• It’s also involved in reflex actions such as startle responses

• the brain provides conscious awareness and is involved in all psychological processes

peripheral nervous system

• autonomic (controls self-regulated action of internal organs and glands)

• sympathetic - arousing

• involuntary

• regulates the functions of our internal organs (heart, stomach, lungs, and intestines)

• controls some of the muscles within the body

• regulates involuntary responses ( we don’t notice when blood vessels change size or our heart beats faster)

• responsible for functions that keep the body in a stable state (homeostasis)

• example - controls heart rate, eye sensitivity, and digestion

• Many of the functions are automatic - they require little or no conscious thought

• control centre - top of the brain stem (hypothalamus and pituitary gland)

• acts as an accelerant

• important for the mobilisation of resources during fight or flight

• parasympathetic - calming

• somatic ( controls voluntary movement of skeletal muscles)

• regulates voluntary movements, part of the PNS - connects the brain to the motor neurons, such as those found in skeletal muscles

• We are in control of this system (voluntarily), and we use it when we want to make our muscles move

• brake to bodily functions

• rest and digest functions

•  This is the automatic response that tells the body it is safe to focus on recovery and involves lowering blood pressure, breathing rate and heart rate as well as triggering other functions like digestion

  
  

Types of neuron

The nervous system functions through three types of neurons: sensory neurons, relay neurons, and motor neurons

• sensory neurons:

• carries information from the sensory receptors ( skin, eyes, and ears) to the CNS

• direction - from PNS to CNS

• structure - long dendrites, short axon

• example - carrying messages about temperature or pain to the brain

•  relay neurons:

• function: connects sensory neurons to motor neurons within the CNS

• works inside the CNS only

• short dendrites and short axons

• example - In a reflex arc, relay neurons pass the message from sensory to motor neurons in the spinal cord.

• motor neurons:

• function - carry messages from the CNS to the effectors (muscles or glands)

• directions - from CNS - effectors

• structure - short dendrites, long axon

• example - sending a signal from the spinal cord to the muscle to make it contract

nervous system overview

1⃣ Central Nervous System (CNS)

Made up of:

Brain – centre of all conscious awareness. Divided into parts (e.g., cerebrum, cerebellum, brain stem).

• Spinal Cord – passes messages to and from the brain; responsible for reflex actions.

Function:

Controls behaviour and regulates physiological processes.

• Processes information and sends instructions to the body.

2⃣ Peripheral Nervous System (PNS)

Made up of all the nerves outside the CNS.
Function: Transmits information to and from the CNS.

Divided into two subsystems:

a) Somatic Nervous System (SNS)

• Voluntary control of muscles (e.g. walking).

• Carries sensory information to CNS and motor commands from CNS to muscles.

• Controls skeletal muscles.

⚙ b) Autonomic Nervous System (ANS)

• Controls involuntary functions (e.g. heart rate, digestion, breathing).

• Automatic (you don’t consciously control it).

The ANS is split into two branches:

🔺 Sympathetic Nervous System

• Activates the body in stressful situations (“fight or flight”).

• Increases heart rate, dilates pupils, and slows digestion.

🔻 Parasympathetic Nervous System

• Calms the body after stress (“rest and digest”).

• Slows heart rate, stimulates digestion. Nervous System

  │

  ├── Central Nervous System (CNS)

  │ ├── Brain

  │ └── Spinal Cord

  │

  └── Peripheral Nervous System (PNS)

  ├── Somatic Nervous System (SNS)

  └── Autonomic Nervous System (ANS)

  ├── Sympathetic

  └── Parasympathetic

summary of the whole nervous system

• nervous system - complex network of nerve cells that carry messages to and from brain and spinal cord to different parts of the body - process of communication

nervous system - branches off into:

central nervous system:

• brain

• spinal chord - connected to brain - sends information to the brain from the outer part of the body ( PNS) and sends signals from brain to the PNS

• spinal chord connected to brain to send info to it from outer parts of the body

peripheral nervous system:

• outer body

• carries information to the CNS or from the CNS to the rest of the body

• somatic nervous system: responsible for conscious perception and voluntary movement of skeletal muscles

• has sensory and motor neurons ( somatic nervous system receives sensory information from outside world and sends it to the brain)

• somatic ns sends a signal to muscles (motor neurons) to bring action

• autonomic nervous system:

• responsible for involuntary controls of the body including reflex movement and organ function ( breathing and heart rate)

• no sensory neurons - only motor neurons to bring action

• split into:

• sympathetic nervous system:

• fight or flight

• releasing adrenaline and physiological changes in the body taking place

• parasympathetic nervous system:

• rest and digest