The Nervous System

• Can be organised into 2 groups: CNS and PNS CNS: Brain and Spinal Cord PNS: Somatic and Autonomic  

CNS

• Made up of brain and Spinal Cord • Spinal cord is hollow tube filled with cerebrospinal fluid - communicates with external nerves and control spinal reflexes • Brain is broken into 3 sections: forebrain, midbrain, hindbrain. Forebrain: Cerebrum, thalamus, hypothalamus (Controls conscious processes and develops last) Midbrain: No discernible structures and mostly 'absorbed' at birth Hindbrain: Develops first, essential and automatic functions (eg. breathing, heartbeat)

PNS

• Divided into somatic and autonomic Somatic • Comprised of sensory neurons and motor neurons. Governs conscious brain sensing and response. Autonomic • Unconscious or involuntary actions to stimuli. Automatic response to information.     Sympathetic: Fight or flight    Parasympathetic: Rest and digest   

The Neuron

• Basic unit of the nervous system • Each section of the NS is a collection of neurons • Every neuron has a: cell body, nucleus, axon, dendrites, axon terminals, and a myelin sheath. • Info comes in at the dendrites and is passed on by neurotransmitters at the axon terminal.  (Draw the 3 types on neurons from the PP) Sensory (afferent) neurons: • Carry sensory information from the extremities and internal organs to the brain. Receive stimuli from environment and relay that info to the brain. Association Neurons: • Found in the CNS and link motor and sensory neurons. Commonly used in reflex arcs. Motor (efferent) neurons: • Carry messages from brain to target organs, tissues, or cells, to evoke a response to the stimulus (cause the body to react to information). • Response of the NS is quick-acting and short-lasting.  

Reflex Arc

• Responsible for bringing about reflex actions • Consist of sensory neuron, interneuron  (sometimes), and motor neuron, without requiring the brains coordination. 5 Step Procedure: 1. Arrival of stimulus  2. Activation of sensory neuron 3. Info is processed and response triggered by interneuron 4. Activation of motor neuron 5. Response by effector