The Nervous System

Seite 1

• 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

Seite 2

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